1
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Masudi SP, Odadi WO, Kimuyu DM, Gachuiri CK, Sensenig RL, Young TP. Wild herbivores and cattle have differing effects on postfire herbaceous vegetation recovery in an African savanna. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2024; 34:e2975. [PMID: 38747033 DOI: 10.1002/eap.2975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 12/01/2023] [Accepted: 02/06/2024] [Indexed: 07/02/2024]
Abstract
Fire and herbivory have profound effects on vegetation in savanna ecosystems, but little is known about how different herbivore groups influence vegetation dynamics after fire. We assessed the separate and combined effects of herbivory by cattle and wild meso- and megaherbivores on postfire herbaceous vegetation cover, species richness, and species turnover in a savanna ecosystem in central Kenya. We measured these vegetation attributes for five sampling periods (from 2013 to 2017) in prescribed burns and unburned areas located within a series of replicated long-term herbivore exclosures that allow six different combinations of cattle and wild meso- and megaherbivores (elephants and giraffes). Vegetation cover (grasses, mainly) and species richness were initially reduced by burning but recovered by 15-27 months after fire, suggesting strong resilience to infrequent fire. However, the rates of recovery differed in plots accessible by different wild and domestic herbivore guilds. Wildlife (but not cattle) delayed postfire recovery of grasses, and the absence of wildlife (with or without cattle) delayed recovery of forbs. Herbivory by only cattle increased grass species richness in burned relative to unburned areas. Herbivory by cattle (with or without wildlife), however, reduced forb species richness in burned relative to unburned areas. Herbivory by wild ungulates (but not cattle) increased herbaceous species turnover in burned relative to unburned areas. Megaherbivores had negligible modifying effects on these results. This study demonstrates that savanna ecosystems are remarkably resilient to infrequent fires, but postfire grazing by cattle and wild mesoherbivores exerts different effects on recovery trajectories of herbaceous vegetation.
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Affiliation(s)
- Sherril P Masudi
- Department of Animal Production, University of Nairobi, Nairobi, Kenya
- Wageningen Institute of Animal Science, Wageningen University and Research, Wageningen, The Netherlands
| | - Wilfred O Odadi
- Department of Natural Resources, Egerton University, Egerton, Kenya
- Mpala Research Center, Nanyuki, Kenya
| | - Duncan M Kimuyu
- Mpala Research Center, Nanyuki, Kenya
- Department of Natural Resources, Karatina University, Karatina, Kenya
| | | | - Ryan L Sensenig
- Mpala Research Center, Nanyuki, Kenya
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Truman P Young
- Mpala Research Center, Nanyuki, Kenya
- Department of Plant Sciences, University of California, Davis, Davis, California, USA
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2
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Voysey MD, de Bruyn PJN, Davies AB. Are hippos Africa's most influential megaherbivore? A review of ecosystem engineering by the semi-aquatic common hippopotamus. Biol Rev Camb Philos Soc 2023; 98:1509-1529. [PMID: 37095627 DOI: 10.1111/brv.12960] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 03/30/2023] [Accepted: 04/03/2023] [Indexed: 04/26/2023]
Abstract
Megaherbivores perform vital ecosystem engineering roles, and have their last remaining stronghold in Africa. Of Africa's remaining megaherbivores, the common hippopotamus (Hippopotamus amphibius) has received the least scientific and conservation attention, despite how influential their ecosystem engineering activities appear to be. Given the potentially crucial ecosystem engineering influence of hippos, as well as mounting conservation concerns threatening their long-term persistence, a review of the evidence for hippos being ecosystem engineers, and the effects of their engineering, is both timely and necessary. In this review, we assess, (i) aspects of hippo biology that underlie their unique ecosystem engineering potential; (ii) evaluate hippo ecological impacts in terrestrial and aquatic environments; (iii) compare the ecosystem engineering influence of hippos to other extant African megaherbivores; (iv) evaluate factors most critical to hippo conservation and ecosystem engineering; and (v) highlight future research directions and challenges that may yield new insights into the ecological role of hippos, and of megaherbivores more broadly. We find that a variety of key life-history traits determine the hippo's unique influence, including their semi-aquatic lifestyle, large body size, specialised gut anatomy, muzzle structure, small and partially webbed feet, and highly gregarious nature. On land, hippos create grazing lawns that contain distinct plant communities and alter fire spatial extent, which shapes woody plant demographics and might assist in maintaining fire-sensitive riverine vegetation. In water, hippos deposit nutrient-rich dung, stimulating aquatic food chains and altering water chemistry and quality, impacting a host of different organisms. Hippo trampling and wallowing alters geomorphological processes, widening riverbanks, creating new river channels, and forming gullies along well-utilised hippo paths. Taken together, we propose that these myriad impacts combine to make hippos Africa's most influential megaherbivore, specifically because of the high diversity and intensity of their ecological impacts compared with other megaherbivores, and because of their unique capacity to transfer nutrients across ecosystem boundaries, enriching both terrestrial and aquatic ecosystems. Nonetheless, water pollution and extraction for agriculture and industry, erratic rainfall patterns and human-hippo conflict, threaten hippo ecosystem engineering and persistence. Therefore, we encourage greater consideration of the unique role of hippos as ecosystem engineers when considering the functional importance of megafauna in African ecosystems, and increased attention to declining hippo habitat and populations, which if unchecked could change the way in which many African ecosystems function.
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Affiliation(s)
- Michael D Voysey
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
| | - P J Nico de Bruyn
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
| | - Andrew B Davies
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
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3
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Brassard F, Pettit MJ, Murphy BP, Andersen AN. Fire influences ant diversity by modifying vegetation structure in an Australian tropical savanna. Ecology 2023; 104:e4143. [PMID: 37471112 DOI: 10.1002/ecy.4143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 06/29/2023] [Indexed: 07/21/2023]
Abstract
Fire is a dominant ecological force shaping many faunal communities globally. Fire affects fauna either directly, such as by killing individuals, or indirectly, such as by modifying vegetation structure. Vegetation structure itself also modulates fire frequency and intensity. As such, faunal responses to fire need to be seen through the lens of variable fire activity and vegetation structure. Here, we incorporate information on fire activity and vegetation structure to enhance an understanding of the response of ants to long-term (17-year) experimental fire treatments in an extremely fire-prone tropical savanna in northern Australia. Previous analysis revealed limited divergence in ant communities after 5 years of experimental fire treatment. Hence, we first investigated the extent to which ant communities diverged over a subsequent 12 years of treatment. We then assessed the relative contribution of fire treatment, cumulative fire intensity (fire activity), and woody cover to responses of ant species frequency of occurrence, richness, and composition. We found that, even after 17 years, fire treatments explained little variation in any ant response variable. In contrast, woody cover was a strong predictor for all of them, while fire activity was a moderate predictor for abundance and richness. Ant species occurrence and richness increased in open habitats receiving higher levels of fire activity, compared with plots with higher vegetation cover experiencing low (or no) fire activity. Moreover, species composition differed between plots with high and low vegetation cover. Our findings provide experimental support to the principle that the effects of fire on fauna are primarily indirect, via its effect on vegetation structure. Furthermore, our results show that a "uniform" fire regime does not have uniform impacts on the ant fauna, because of variability imposed by interactions between vegetation structure and fire activity. This helps to explain why there is often a weak relationship between pyrodiversity and biodiversity, and it lessens the need for active management of pyrodiversity to maintain biodiversity.
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Affiliation(s)
- François Brassard
- Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, Northern Territory, Australia
| | - Magen J Pettit
- Commonwealth Scientific and Industrial Research Organisation, Berrimah, Northern Territory, Australia
| | - Brett P Murphy
- Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, Northern Territory, Australia
| | - Alan N Andersen
- Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, Northern Territory, Australia
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4
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Gordon CE, Greve M, Henley M, Bedetti A, Allin P, Svenning JC. Elephant rewilding affects landscape openness and fauna habitat across a 92-year period. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2023; 33:e2810. [PMID: 36694991 DOI: 10.1002/eap.2810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/27/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
Trophic rewilding aims to promote biodiverse self-sustaining ecosystems through the restoration of ecologically important taxa and the trophic interactions and cascades they propagate. How rewilding effects manifest across broad temporal scales will determine ecosystem states; however, our understanding of post-rewilding dynamics across longer time periods is limited. Here we show that the restoration of a megaherbivore, the African savannah elephant (Loxodonta africana), promotes landscape openness (i.e., various measures of vegetation composition/complexity) and modifies fauna habitat and that these effects continue to manifest up to 92 years after reintroduction. We conducted a space-for-time floristic survey and assessment of 17 habitat attributes (e.g., floristic diversity and cover, ground wood, tree hollows) across five comparable nature reserves in South African savannah, where elephants were reintroduced between 1927 and 2003, finding that elephant reintroduction time was positively correlated with landscape openness and some habitat attributes (e.g., large-sized tree hollows) but negatively associated with others (e.g., large-sized coarse woody debris). We then indexed elephant site occurrence between 2006 and 2018 using telemetry data and found positive associations between site occurrence and woody plant densities. Taken alongside the longer-term space-for-time survey, this suggests that elephants are attracted to dense vegetation in the short term and that this behavior increases landscape openness in the long term. Our results suggest that trophic rewilding with elephants helps promote a semi-open ecosystem structure of high importance for African biodiversity. More generally, our results suggest that megafauna restoration represents a promising tool to curb Earth's recent ecological losses and highlights the importance of considering long-term ecological responses when designing and managing rewilding projects.
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Affiliation(s)
- Christopher E Gordon
- Centre for Biodiversity Dynamics in a Changing World and Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus C, Denmark
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia
| | - Michelle Greve
- Department of Plant and Soil Sciences, University of Pretoria, Pretoria, South Africa
| | - Michelle Henley
- Applied Behavioural Ecology and Ecosystem Research Unit, School of Environmental Sciences, University of South Africa, Pretoria, South Africa
- Elephants Alive, Hoedspruit, South Africa
- Department of Philosophy, Faculty of Humanities, University of Johannesburg, Johannesburg, South Africa
| | | | - Paul Allin
- Transfrontier Africa, Hoedspruit, South Africa
| | - Jens-Christian Svenning
- Centre for Biodiversity Dynamics in a Changing World and Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus C, Denmark
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5
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Dornbusch MJ, Limb RF, Bloom-Cornelius IV, Elmore RD, Weir JR, Fuhlendorf SD. Factors influencing the persistence of a fire-sensitive Artemisia species in a fire-dependent ecosystem. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2022; 32:e2604. [PMID: 35365937 DOI: 10.1002/eap.2604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 01/03/2022] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
Fire refugia and patchiness are important to the persistence of fire-sensitive species and may facilitate biodiversity conservation in fire-dependent landscapes. Playing the role of ecosystem engineers, large herbivores alter vegetation structure and can reduce wildfire risk. However, herbivore effects on the spatial variability of fire and the persistence of fire-sensitive species are not clear. To examine the hypothesis that large herbivores support the persistence of fire-sensitive species through the creation of fire refugia in fire-prone landscapes, we examined the response of a fire-sensitive plant, Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis [Beetle & Young]) to fire and grazing in the fire-dependent mixed-grass prairie of the northern Great Plains. We carried out a controlled burn in 2010 within pre-established exclosures that allowed differential access to wild and domestic herbivores and no record of fire in the previous 75 years due to fire suppression efforts. The experiment was set up with a split-plot design to also examine potential changes in plots that were not burned. Canopy cover of big sagebrush was recorded before the burn in 2010 and again in 2011 with percent area burned recorded within 1-month post-fire in the burned plots. Percentage area burned was the greatest in ungulate exclosures (92% ± 2%) and the least in open areas (55% ± 21%), suggesting that large herbivores influenced fire behavior (e.g., reducing fire intensity and rate of spread) and are likely to increase fire patchiness through their alterations to the fuel bed. Regression analysis indicated that the proportion of sagebrush cover lost was significantly correlated with the proportion of area burned (R2 = 0.76, p = 0.05). No differences in the non-burn plots were observed among grazing treatments or among years. Altogether, this illustrates the potential importance of large herbivores in creating biotic-driven fire refugia for fire-sensitive species to survive within the flammable fuel matrix of fire-dependent grassland ecosystems such as the mixed-grass prairie. Our findings also attest to the resiliency of the northern Great Plains to fire and herbivory and underscore the value of managing grasslands for heterogeneity with spatial and temporal variations in these historic disturbances.
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Affiliation(s)
- Megan J Dornbusch
- School of Natural Resource Sciences, North Dakota State University, Fargo, North Dakota, USA
| | - Ryan F Limb
- School of Natural Resource Sciences, North Dakota State University, Fargo, North Dakota, USA
| | - Ilana V Bloom-Cornelius
- Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, Oklahoma, USA
| | - R Dwayne Elmore
- Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, Oklahoma, USA
| | - John R Weir
- Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Samuel D Fuhlendorf
- Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, Oklahoma, USA
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6
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Nugent DT, Baker-Gabb DJ, Leonard SWJ, Morgan JW. Livestock grazing to maintain habitat of a critically endangered grassland bird: Is grazer species important? ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2022; 32:e2587. [PMID: 35333422 DOI: 10.1002/eap.2587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/29/2021] [Accepted: 09/03/2021] [Indexed: 06/14/2023]
Abstract
Livestock grazing is an important management tool for biodiversity conservation in many native grasslands across the globe. Understanding how different grazing species interact with their environment is integral to achieving conservation goals. In the semiarid grasslands of Australia, grazing by sheep or cattle is used to manipulate vegetation structure to suit the habitat needs of a globally unique, critically endangered grassland bird, the plains-wanderer Pedionomus torquatus. However, there has been no investigation of whether sheep and cattle differ in their effects on plains-wanderer habitat and, therefore, it is unknown if these grazers are substitutable as a management tool. Using a grazing experiment in native grasslands over 3 years, we determined the effects of grazer type (sheep, cattle) on occurrence and vocal activity of plains-wanderer, vegetation structure and composition, and food availability. We also examined grazer effects on encounter rates of other grassland birds. Plains-wanderer breeding activity was inferred from vocalization rates captured by bioacoustic recorders. Spotlighting was used to measure encounter rates of other grassland birds. We found that different grazers altered the structure of the habitat. Grasslands grazed by cattle were typically more open, less variable, and lacked patches of dense vegetation relative to those grazed by sheep. Grazer type did not influence the likelihood of plains-wanderer occurrence, but it did interact with year of survey to affect breeding activity. The number of days with one or more calls significantly increased at sheep grazed sites in year-3, which coincided with enduring drought conditions. Similarly, grazer effects on encounter rate of all birds, bird species richness, and Australasian pipit Anthus novaeseelandiae were different between years. Dense vegetation specialists (such as stubble quail Coturnix pectoralis) were positively associated with grasslands grazed by sheep. As a habitat management tool, sheep or cattle grazing are useful when the goal is to support an open grassland structure for the plains-wanderer. However, their substitutability is likely to be dependent upon climate. We caution that a loss of dense vegetation in grasslands grazed by cattle during drought could limit the availability of optimal habitat for the plains-wanderer and habitat for other grassland birds.
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Affiliation(s)
- Daniel T Nugent
- Department of Ecology, Environment, and Evolution, La Trobe University, Melbourne, Victoria, Australia
| | | | - Steve W J Leonard
- Department of Primary Industries, Parks, Water and Environment, Tasmanian Government, Hobart, Tasmania, Australia
| | - John W Morgan
- Department of Ecology, Environment, and Evolution, La Trobe University, Melbourne, Victoria, Australia
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7
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Young TP, Kimuyu DN, LaMalfa EM, Werner CM, Jones C, Masudi P, Ang'ila R, Sensenig RL. Effects of large mammalian herbivory, previous fire, and year of burn on fire behavior in an African savanna. Ecosphere 2022. [DOI: 10.1002/ecs2.3980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Truman. P. Young
- Department of Plant Sciences University of California Davis California USA
- Mpala Research Centre Nanyuki Kenya
| | - Duncan N. Kimuyu
- Mpala Research Centre Nanyuki Kenya
- Department of Natural Resources Karatina University Karatina Kenya
| | - Eric M. LaMalfa
- Department of Wildland Resources and Ecology Center Utah State University Logan Utah USA
| | - Chhaya M. Werner
- Department of Botany and Wyoming EPSCoR University of Wyoming Laramie Wyoming USA
| | | | - Phyllis Masudi
- Department of Animal Production University of Nairobi Kangemi Kenya
| | - Robert Ang'ila
- Department of Environmental Studies Karatina University Karatina Kenya
| | - Ryan L. Sensenig
- Department of Biological Sciences Goshen College Goshen Indiana USA
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8
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Wells HBM, Crego RD, Ekadeli J, Namoni M, Kimuyu DM, Odadi WO, Porensky LM, Dougill AJ, Stringer LC, Young TP. Less Is More: Lowering Cattle Stocking Rates Enhances Wild Herbivore Habitat Use and Cattle Foraging Efficiency. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.825689] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Over a quarter of the world’s land surface is grazed by cattle and other livestock, which are replacing wild herbivores and widely regarded as drivers of global biodiversity declines. The effects of livestock presence versus absence on wild herbivores are well documented. However, the environmental context-specific effects of cattle stocking rate on biodiversity and livestock production are poorly understood, precluding nuanced rangeland management recommendations. To address this, we used a long term exclosure experiment in a semi-arid savanna ecosystem in central Kenya that selectively excludes cattle (at different stocking rates), wild mesoherbivores, and megaherbivores. We investigated the individual and interactive effects of cattle stocking rate (zero/moderate/high) and megaherbivore (>1,000 kg) accessibility on habitat use (measured as dung density) by two dominant wild mesoherbivores (50–1,000 kg; zebra Equus quagga and eland Taurotragus oryx) across the “wet” and “dry” seasons. To explore potential tradeoffs or co-benefits between cattle production and wildlife conservation, we tested for individual and interactive effects of cattle stocking rate and accessibility by wild mesoherbivores and megaherbivores (collectively, large wild herbivores) on the foraging efficiency of cattle across both seasons. Eland habitat use was reduced by cattle at moderate and high stocking rates across both dry and wet seasons and regardless of megaherbivore accessibility. We observed a positive effect of megaherbivores on zebra habitat use at moderate, but not high, stocking rates. Cattle foraging efficiency (g dry matter step–1 min–1) was lower in the high compared to moderate stocking rate treatments during the dry season, and was non-additively reduced by wild mesoherbivores and high cattle stocking rates during the wet season. These results show that high stocking rates are detrimental to wild mesoherbivore habitat use and cattle foraging efficiency, while reducing to moderate stocking rates can benefit zebra habitat use and cattle foraging efficiency. Our findings demonstrate that ecosystem management and restoration efforts across African rangelands that involve reducing cattle stocking rates may represent a win-win for wild herbivore conservation and individual performance of livestock.
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9
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OUP accepted manuscript. J Mammal 2022. [DOI: 10.1093/jmammal/gyac050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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10
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Rabideau‐Childers R, Angier KIW, Dean BZM, Blumstein M, Darling WS, Kennedy‐Yoon A, Ziemke CH, Perez‐Martinez CA, Wu D, Ye W, Yekwayo I, Kimuyu DM, Martins DJ, Pierce NE. Evidence of nutrient translocation in response to smoke exposure by the East African ant acacia, Vachellia drepanolobium. Ecol Evol 2022; 12:e8244. [PMID: 35126997 PMCID: PMC8794709 DOI: 10.1002/ece3.8244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 09/27/2021] [Accepted: 09/30/2021] [Indexed: 12/04/2022] Open
Abstract
Fire is a major selective force on arid grassland communities, favoring traits such as the smoke-induced seed germination response seen in a wide variety of plant species. However, little is known about the relevance of smoke as a cue for plants beyond the seedling stage.We exposed a fire-adapted savanna tree, Vachellia (=Acacia) drepanolobium, to smoke and compared nutrient concentrations in leaf and root tissues to unexposed controls. Experiments were performed on three age cohorts: 2-year-old, 9-month-old, and 3-month-old plants.For the 2-year-old plants exposed to smoke, carbon and nitrogen concentrations were lower in the leaves and higher in the roots than controls. Less pronounced trends were found for boron and magnesium.In contrast, smoke-exposed 3-month-old plants had lower root nitrogen concentrations than controls. No significant differences were found in the 9-month-old plants, and no significant shifts in other nutrient concentrations were observed between plant tissues for any of the three age cohorts. Synthesis: Our findings are consistent with smoke-induced translocation of nutrients from leaves to roots in 2-year-old V. drepanolobium. This could represent a novel form of fire adaptation, with variation over the course of plant development. The translocation differences between age cohorts highlight the need to investigate smoke response in older plants of other species. Accounting for this adaptation could better inform our understanding of savanna community structure and nutrient flows under fire regimes altered by anthropogenic land use and climate change.
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Affiliation(s)
- Richard Rabideau‐Childers
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
| | - Katherine I. W. Angier
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
| | - Brendan Z. M. Dean
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
| | - Meghan Blumstein
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
- Department of Civil and Environmental EngineeringMITCambridgeMassachusettsUSA
| | - Walker S. Darling
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
| | - Annina Kennedy‐Yoon
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
| | - Clayton H. Ziemke
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
| | - Christian A. Perez‐Martinez
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
- Division of Biological SciencesUniversity of MissouriColumbiaMissouriUSA
| | - Donghao Wu
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
- College of Life SciencesZhejiang UniversityHangzhouChina
| | - Wenqing Ye
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
- College of Life SciencesZhejiang UniversityHangzhouChina
| | - Inam Yekwayo
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
- School of Biology and Environmental SciencesUniversity of MpumalangaMbombelaSouth Africa
| | - Duncan M. Kimuyu
- Department of Natural ResourcesKaratina UniversityKaratinaKenya
- Mpala Research CentreNanyukiKenya
| | - Dino J. Martins
- Mpala Research CentreNanyukiKenya
- Department of Ecology and Evolutionary BiologyPrinceton UniversityPrincetonNew JerseyUSA
| | - Naomi E. Pierce
- Department of Organismic and Evolutionary Biology and Museum of Comparative ZoologyHarvard UniversityCambridgeMassachusettsUSA
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11
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Karp AT, Faith JT, Marlon JR, Staver AC. Global response of fire activity to late Quaternary grazer extinctions. Science 2021; 374:1145-1148. [PMID: 34822271 DOI: 10.1126/science.abj1580] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Allison T Karp
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
| | - J Tyler Faith
- Natural History Museum of Utah, University of Utah, Salt Lake City, UT, USA.,Department of Anthropology, University of Utah, Salt Lake City, UT, USA.,Origins Centre, University of the Witwatersrand, Johannesburg, South Africa
| | | | - A Carla Staver
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA.,Yale Institute for Biospheric Studies, Yale University, New Haven, CT, USA
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12
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Chard M, Foster CN, Lindenmayer DB, Cary GJ, MacGregor CI, Blanchard W. Time since fire influences macropod occurrence in a fire‐prone coastal ecosystem. AUSTRAL ECOL 2021. [DOI: 10.1111/aec.13127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Matthew Chard
- Fenner School of Environment & Society The Australian National University Canberra Australian Capital Territory 2600 Australia
| | - Claire N. Foster
- Fenner School of Environment & Society The Australian National University Canberra Australian Capital Territory 2600 Australia
| | - David B. Lindenmayer
- Fenner School of Environment & Society The Australian National University Canberra Australian Capital Territory 2600 Australia
| | - Geoffrey J. Cary
- Fenner School of Environment & Society The Australian National University Canberra Australian Capital Territory 2600 Australia
| | - Christopher I. MacGregor
- Fenner School of Environment & Society The Australian National University Canberra Australian Capital Territory 2600 Australia
- Threatened Species Recovery Hub National Environmental Science Program Fenner School of Environment & Society The Australian National University Canberra Australian Capital Territory Australia
| | - Wade Blanchard
- Fenner School of Environment & Society The Australian National University Canberra Australian Capital Territory 2600 Australia
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13
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LaMalfa EM, Riginos C, Veblen KE. Browsing wildlife and heavy grazing indirectly facilitate sapling recruitment in an East African savanna. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2021; 31:e02399. [PMID: 34212437 DOI: 10.1002/eap.2399] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 10/07/2020] [Accepted: 03/03/2021] [Indexed: 06/13/2023]
Abstract
Management of tree cover, either to curb bush encroachment or to mitigate losses of woody cover to over-browsing, is a major concern in savanna ecosystems. Once established, trees are often "trapped" as saplings, since interactions among disturbance, plant competition, and precipitation delay sapling recruitment into adult size classes. Saplings can be directly suppressed by wildlife browsing and competition from adjacent plants, and indirectly facilitated by grazers, such as cattle, which feed on neighboring grasses. Yet few experimental studies have simultaneously quantified the effects of cattle and wildlife on sapling growth, particularly over long time scales. We used a series of replicated 4-ha herbivore-manipulation plots to investigate the net effects of wildlife and moderate cattle grazing on Acacia drepanolobium sapling growth over 10 years that encompassed extended wet and dry periods. We also simulated more intense cattle grazing using grass removal treatments (0.5-m radius around saplings), and we quantified the role of intraspecific tree competition using neighborhood tree surveys (trees within a 3-m radius). Wildlife, which included elephants, had a positive effect on sapling growth. Wildlife also reduced neighbor tree density during the 10-yr study, which likely caused the positive effect of wildlife on saplings. Although moderate cattle grazing did not affect sapling growth, grass removal treatments simulating heavy grazing increased sapling growth. Both grass removal and neighbor tree effects on saplings were strongest during above-average rainfall years following drought. This highlights that livestock-driven reductions in grass cover and catastrophic wildlife damage to trees during droughts present a need, or an opportunity, for targeted management of sapling growth and woody plant cover during ensuing wet periods.
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Affiliation(s)
- Eric M LaMalfa
- Department of Wildland Resources & Ecology Center, Utah State University, Logan, Utah, 84321, USA
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
| | - Corinna Riginos
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- The Nature Conservancy, 258 Main Street, Suite 200, Lander, Wyoming, 82520, USA
| | - Kari E Veblen
- Department of Wildland Resources & Ecology Center, Utah State University, Logan, Utah, 84321, USA
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
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14
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Djogbenou A, Azihou AF, Dassou AG, Assogbadjo AE, Kassa B, Gaoue OG. Limited ant co-occurrence and defensive mutualism in Acacia plants in a West African savanna. AOB PLANTS 2021; 13:plab036. [PMID: 34234937 PMCID: PMC8255073 DOI: 10.1093/aobpla/plab036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 06/02/2021] [Indexed: 06/13/2023]
Abstract
Our understanding of the role of fire and effect of ant species composition, beyond their diversity and abundance, on the effectiveness of mutualism defence is limited. Most of our knowledge of ant-plant defence in tropical Africa is biased towards East African savannas which have richer soil, higher primary productivity and a more diverse arthropods and mammal community than West African savannas. We assessed the diversity of ant species associated with Acacia species in the Pendjari Biosphere Reserve in the Dahomey Gap, and their impacts on elephant damage. Elephant damage, ant diversity and abundance were measured in stands of five Acacia species. Eleven ant species were identified in the Acacia stands. The composition of these ant communities varied across Acacia species. Pair of ant species co-occurred in only 2 % of sampled trees, suggesting a strong competitive exclusion. Within this annually burnt environment, ants were rare on small trees. The intensity of elephant-caused branch breaking did not vary between trees with ants and trees without ants, suggesting limited Acacia-ant mutualism. Such limited biotic defence may mask strong physical and chemical defence mechanisms of Acacia trees against elephant damage. Ant assemblages in West Africa, unlike those in the more productive East Africa, are particularly species-poor. However, there is a convergence between these two regions in low rate of ant co-occurrence which might indicate strong competitive exclusion. Our study suggests that such low ant species richness while limiting the efficacy of mutualism in controlling mega-herbivore damage may mask a strong defence syndrome.
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Affiliation(s)
- Anyse Djogbenou
- Laboratory of Applied Ecology, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Benin
| | - Akomian F Azihou
- Laboratory of Applied Ecology, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Benin
| | - Anicet G Dassou
- Laboratory of Biotechnology, Genetic Resources, Plant and Animal Breeding, Faculty of Sciences and Technology of Dassa, National University of Sciences, Technology, Engineering and Mathematics, 01 BP 14, Dassa-Zoumè, Benin
| | - Achille E Assogbadjo
- Laboratory of Applied Ecology, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Benin
| | - Barthelemy Kassa
- Laboratory of Applied Ecology, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Benin
| | - Orou G Gaoue
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA
- Faculty of Agronomy, University of Parakou, BP 123, Parakou, Benin
- Department of Geography, Environmental Management and Energy Sciences, University of Johannesburg, APK Campus, Johannesburg, South Africa
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15
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Charles GK, Riginos C, Veblen KE, Kimuyu DM, Young TP. Termite mound cover and abundance respond to herbivore-mediated biotic changes in a Kenyan savanna. Ecol Evol 2021; 11:7226-7238. [PMID: 34188808 PMCID: PMC8216887 DOI: 10.1002/ece3.7445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 02/24/2021] [Accepted: 02/26/2021] [Indexed: 11/12/2022] Open
Abstract
Both termites and large mammalian herbivores (LMH) are savanna ecosystem engineers that have profound impacts on ecosystem structure and function. Both of these savanna engineers modulate many common and shared dietary resources such as woody and herbaceous plant biomass, yet few studies have addressed how they impact one another. In particular, it is unclear how herbivores may influence the abundance of long-lived termite mounds via changes in termite dietary resources such as woody and herbaceous biomass. While it has long been assumed that abundance and areal cover of termite mounds in the landscape remain relatively stable, most data are observational, and few experiments have tested how termite mound patterns may respond to biotic factors such as changes in large herbivore communities. Here, we use a broad tree density gradient and two landscape-scale experimental manipulations-the first a multi-guild large herbivore exclosure experiment (20 years after establishment) and the second a tree removal experiment (8 years after establishment)-to demonstrate that patterns in Odontotermes termite mound abundance and cover are unexpectedly dynamic. Termite mound abundance, but areal cover not significantly, is positively associated with experimentally controlled presence of cattle, but not wild mesoherbivores (15-1,000 kg) or megaherbivores (elephants and giraffes). Herbaceous productivity and tree density, termite dietary resources that are significantly affected by different LMH treatments, are both positive predictors of termite mound abundance. Experimental reductions of tree densities are associated with lower abundances of termite mounds. These results reveal a richly interacting web of relationships among multiple savanna ecosystem engineers and suggest that termite mound abundance and areal cover are intimately tied to herbivore-driven resource availability.
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Affiliation(s)
- Grace K. Charles
- Department of Plant SciencesUniversity of CaliforniaDavisCaliforniaUSA
- Mpala Research CentreNanyukiKenya
| | - Corinna Riginos
- Mpala Research CentreNanyukiKenya
- The Nature ConservancyLanderWyomingUSA
| | - Kari E. Veblen
- Mpala Research CentreNanyukiKenya
- Department of Wildland Resources and Ecology CenterUtah State UniversityLoganUtahUSA
| | - Duncan M. Kimuyu
- Mpala Research CentreNanyukiKenya
- Department of Natural Resource ManagementKaratina UniversityKaratinaKenya
| | - Truman P. Young
- Department of Plant SciencesUniversity of CaliforniaDavisCaliforniaUSA
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The effects of high-severity fires on the arboreal ant community of a Neotropical savanna. Oecologia 2021; 196:951-961. [PMID: 33885980 DOI: 10.1007/s00442-021-04922-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 04/13/2021] [Indexed: 10/21/2022]
Abstract
Fire-suppression is of concern in fire-prone ecosystems because it can result in the loss of endemic species. Suppressing fires also causes a build-up of flammable biomass, increasing the risk of severe fires. Using a Before-After, Control-Impacted design, we assessed the consequences of high-severity fires on Neotropical savanna arboreal ant communities. Over a 9-year period, we sampled the ant fauna of the same trees before and after two severe fires that hit a savanna reserve in Brazil and the trees from an unburned savanna site that served as a temporal control. The ant community associated with the unburned trees was relatively stable, with no significant temporal variation in species richness and only a few species changing in abundance over time. In contrast, we found a strong decline in species richness and marked changes in species composition in the burned trees, with some species becoming more prevalent and many becoming rare or locally extinct. The dissimilarity in species richness and composition was significantly smaller between the two pre-fire surveys than between the pre- and post-fire surveys. Fire-induced changes were much more marked among species with strictly arboreal nesting habits, and therefore more susceptible to the direct effects of fire. The decline of some of the ecologically dominant arboreal ant species may be particularly important, as it opens substantial ecological space for cascading community-wide changes. In particular, severe fires appear to disrupt the typical vertical stratification between the arboreal and ground-dwelling faunas, which might lead to homogenization of the overall ant community.
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17
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Young TP, Kimuyu DM, Odadi WO, Wells HBM, Wolf AA. Naïve plant communities and individuals may initially suffer in the face of reintroduced megafauna: An experimental exploration of rewilding from an African savanna rangeland. PLoS One 2021; 16:e0248855. [PMID: 33822786 PMCID: PMC8023473 DOI: 10.1371/journal.pone.0248855] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 03/06/2021] [Indexed: 12/04/2022] Open
Abstract
Excluding large native mammals is an inverse test of rewilding. A 25-year exclosure experiment in an African savanna rangeland offers insight into the potentials and pitfalls of the rewilding endeavor as they relate to the native plant community. A broad theme that has emerged from this research is that entire plant communities, as well as individual plants, adjust to the absence of herbivores in ways that can ill-prepare them for the return of these herbivores. Three lines of evidence suggest that these "naïve" individuals, populations, and communities are likely to initially suffer from herbivore rewilding. First, plots protected from wild herbivores for the past 25 years have developed rich diversity of woody plants that are absent from unfenced plots, and presumably would disappear upon rewilding. Second, individuals of the dominant tree in this system, Acacia drepanolobium, greatly reduce their defences in the absence of browsers, and the sudden arrival of these herbivores (in this case, through a temporary fence break), resulted in far greater elephant damage than for their conspecifics in adjacent plots that had been continually exposed to herbivory. Third, the removal of herbivores favoured the most palatable grass species, and a large number of rarer species, which presumably would be at risk from herbivore re-introduction. In summary, the native communities that we observe in defaunated landscapes may be very different from their pre-defaunation states, and we are likely to see some large changes to these plant communities upon rewilding with large herbivores, including potential reductions in plant diversity. Lastly, our experimental manipulation of cattle represents an additional test of the role of livestock in rewilding. Cattle are in many ways ecologically dissimilar to wildlife (in particular their greater densities), but in other ways they may serve as ecological surrogates for wildlife, which could buffer ecosystems from some of the ecological costs of rewilding. More fundamentally, African savannah ecosystems represent a challenge to traditional Western definitions of "wilderness" as ecosystems free of human impacts. We support the suggestion that as we "rewild" our biodiversity landscapes, we redefine "wildness" in the 21st Century to be inclusive of (low impact, and sometimes traditional) human practices that are compatible with the sustainability of native (and re-introduced) biodiversity.
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Affiliation(s)
- Truman P. Young
- Department of Plant Sciences and Ecology Graduate Group, University of California, Davis, Davis, CA, United States of America
- Mpala Research Centre, Nanyuki, Kenya
| | - Duncan M. Kimuyu
- Mpala Research Centre, Nanyuki, Kenya
- Department of Natural Resources, Karatina University, Karatina, Kenya
| | - Wilfred O. Odadi
- Mpala Research Centre, Nanyuki, Kenya
- Department of Natural Resources, Egerton University, Egerton, Kenya
| | - Harry B. M. Wells
- Sustainability Research Institute, School of Earth and Environment, University of Leeds, Leeds, United Kingdom
- Lolldaiga Hills Research Programme, Nanyuki, Kenya
| | - Amelia A. Wolf
- Department of Integrative Biology, University of Texas, Austin, TX, United States of America
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18
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Werner CM, Kimuyu D, Veblen KE, Sensenig RL, LaMalfa E, Young TP. Synergistic effects of long-term herbivory and previous fire on fine-scale heterogeneity of prescribed grassland burns. Ecology 2021; 102:e03270. [PMID: 33340104 DOI: 10.1002/ecy.3270] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/17/2020] [Accepted: 10/26/2020] [Indexed: 11/11/2022]
Abstract
Grassland and savanna ecosystems, important for both livelihoods and biodiversity conservation, are strongly affected by ecosystem drivers such as herbivory, fire, and drought. Interactions among fire, herbivores and vegetation produce complex feedbacks in these ecosystems, but these have rarely been studied in the context of fuel continuity and resultant fire heterogeneity. We carried out 36 controlled burns within replicated experimental plots that had allowed differential access by wild and domestic large herbivores since 1995 in a savanna ecosystem in Kenya. Half of these were reburns of plots burned 5 yr previously. We show here that the fine-scale spatial heterogeneity of fire was greater in plots (1) previously burned, (2) accessible to large herbivores, and especially (3) these two in combination. An additional embedded experiment demonstrated that even small experimental burn-free patches can have strong positive effects on tree saplings, which experienced less damage during controlled burns and quicker postfire recovery. This work highlights the importance of simultaneously examining the interactions between fire and herbivory on fuel heterogeneity, which can have important impacts on the growth of woody saplings in savanna grasslands.
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Affiliation(s)
- Chhaya M Werner
- Department of Plant Sciences and Graduate Group in Population Biology, University of California, Davis, California, 95616, USA.,Department of Physiological Diversity, Helmholtz Center for Environmental Research (UFZ), Leipzig, D-04318, Germany.,German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, D-04103, Germany.,Department of Ecology, University of Oulu, Oulu, FI-90014, Finland
| | - Duncan Kimuyu
- Mpala Research Centre, Nanyuki, Kenya.,Department of Natural Resources, Karatina University, Karatina, 10101, Kenya
| | - Kari E Veblen
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Ryan L Sensenig
- Mpala Research Centre, Nanyuki, Kenya.,Department of Biological Sciences, Goshen College, Goshen, Indiana, 46526, USA
| | - Eric LaMalfa
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Truman P Young
- Department of Plant Sciences and Graduate Group in Population Biology, University of California, Davis, California, 95616, USA.,Mpala Research Centre, Nanyuki, Kenya
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19
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Johansson MU, Abebe FB, Nemomissa S, Bekele T, Hylander K. Ecosystem restoration in fire-managed savanna woodlands: Effects on biodiversity, local livelihoods and fire intensity. AMBIO 2021; 50:190-202. [PMID: 32451967 PMCID: PMC7708610 DOI: 10.1007/s13280-020-01343-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 04/20/2020] [Accepted: 04/28/2020] [Indexed: 06/11/2023]
Abstract
Ethiopia aims to restore 15 million ha degraded forests and woodlands, but effects on the potentially contrasting goals of long-term carbon storage, biodiversity and sustainable livelihoods are unknown. To quantify the effects of grazing exclusion on vegetation and fire behaviour, we established six 30 × 30 m fenced exclosures with grazed controls, in a mesic wooded savanna. Experimental burns were done after 1.5 years. Tree seedlings were few but more common inside fences. Field layer cover and biomass increased inside fences, and grass species increased in numbers and cover. Fire intensity was higher inside fences, killing shrubs and saplings but not mature trees. Interviews confirmed that overgrazing has resulted in "cool fires", causing shrub encroachment. High-intensity fires occurred in the 1980s after a zoonotic disease killed most livestock. Short-term increase in carbon storage through fire and grazing exclusion may lead to loss of pasture, and in the long-term increased wildfire risk.
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Affiliation(s)
- Maria Ulrika Johansson
- Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91 Stockholm, Sweden
- Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden
| | - Firew Bekele Abebe
- Department of Natural Resources Management, Haramaya University, Dire Dawa, Ethiopia
| | - Sileshi Nemomissa
- Department of Plant Biology and Biodiversity Management, Addis Ababa University, PO Box 3434, Addis Ababa, Ethiopia
| | - Tamrat Bekele
- Department of Plant Biology and Biodiversity Management, Addis Ababa University, PO Box 3434, Addis Ababa, Ethiopia
| | - Kristoffer Hylander
- Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91 Stockholm, Sweden
- Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden
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20
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Kimuyu DM, Kenfack D, Musili PM, Ang’ila RO. Fine‐scale habitat heterogeneity influences browsing damage by elephant and giraffe. Biotropica 2020. [DOI: 10.1111/btp.12848] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Duncan M. Kimuyu
- Department of Natural Resources Karatina University Karatina Kenya
- Mpala Research Center and Wildlife Foundation Nanyuki Kenya
| | - David Kenfack
- ForestGEO Smithsonian Tropical Research Institute Washington DC USA
| | - Paul M. Musili
- East African Herbarium Botany Department National Museums of Kenya Nairobi Kenya
| | - Robert O. Ang’ila
- Mpala Research Center and Wildlife Foundation Nanyuki Kenya
- Department of Environmental Studies Karatina University Kenya
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21
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Vasconcelos HL, Koch EBA, Camarota F, Tito R, Zuanon LA, Maravalhas J. Severe fires alter the outcome of the mutualism between ants and a Neotropical savanna tree. Biol J Linn Soc Lond 2020. [DOI: 10.1093/biolinnean/blaa132] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractPhysical disturbances, such as fire, may affect the relationship between ants and plants. We evaluated the extent to which severe fires alter the protective effect of ants against the herbivores of an extrafloral-nectary bearing tree. We performed an ant removal experiment and sampled the ant fauna from the same trees over 4 years: the pre-fire year, the fire-year, and again 1 and 2 years later. Ants reduced insect herbivory in the pre-fire year and in the fire-year but failed to provide any plant protection in the two years after fire. The magnitude of the ant effect on herbivory did not differ between the pre-fire year and the fire-year. Fire reduced the abundance of ants with strictly arboreal-nesting habits. However, in the fire year (but not in the subsequent ones), this decline was compensated by an increase in the abundance of arboreal generalists and ground-nesting ants foraging in trees. Our results indicate that severe fires can affect the strength and direction of the ant effects on herbivory by altering the structure of the arboreal ant community and the abundance of insect herbivores. Fire disturbance is thus an important factor of conditionality of ant-plant mutualisms in fire-prone habitats, like the Cerrado savannas.
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Affiliation(s)
- Heraldo L Vasconcelos
- Instituto de Biologia, Universidade Federal de Uberlândia, CEP, Uberlândia, MG, Brazil
| | - Elmo B A Koch
- Laboratório de Mirmecologia, Centro de Pesquisas do Cacau–Comissão Executiva Plano da Lavoura Cacaueira, CEP, Ilhéus-BA, Brazil
| | - Flávio Camarota
- Departamento de Biologia Geral, Universidade Federal de Viçosa, CEP, Viçosa, MG, Brazil
| | - Richard Tito
- Instituto de Ciencias de la Naturaleza, Territorio y Energías Renovables, Pontificia Universidad Católica del Perú, Lima, Peru
| | - Lino A Zuanon
- Instituto de Biologia, Universidade Federal de Uberlândia, CEP, Uberlândia, MG, Brazil
| | - Jonas Maravalhas
- Instituto de Biologia, Universidade Federal de Uberlândia, CEP, Uberlândia, MG, Brazil
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22
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Lai L, Kumar S. A global meta-analysis of livestock grazing impacts on soil properties. PLoS One 2020; 15:e0236638. [PMID: 32764754 PMCID: PMC7413490 DOI: 10.1371/journal.pone.0236638] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 07/10/2020] [Indexed: 11/19/2022] Open
Abstract
Grazing effects on soil properties under different soil and environmental conditions across the globe are often controversial. Therefore, it is essential to evaluate the overall magnitude and direction of the grazing effects on soils. This global meta-analysis was conducted using the mixed model method to address the overall effects of grazing intensities (heavy, moderate, and light) on 15 soil properties based on 287 papers published globally from 2007 to 2019. Our findings showed that heavy grazing significantly increased the soil BD (11.3% relative un-grazing) and PR (52.5%) and reduced SOC (-10.8%), WC (-10.8%), NO3- (-23.5%), and MBC (-27.9%) at 0–10 cm depth, and reduced SOC (-22.5%) and TN (-19.9%) at 10–30 cm depth. Moderate grazing significantly increased the BD (7.5%), PR (46.0%), and P (18.9%) (0–10 cm), and increased pH (4.1%) and decreased SOC (-16.4%), TN (-10.6%), and P (-23.9%) (10–30 cm). Light grazing significantly increased the SOC (10.8%) and NH4+ (28.7%) (0–10 cm). Heavy grazing showed much higher mean probability (0.70) leading to overgrazing than the moderate (0.14) and light (0.10) grazing. These findings indicate that, globally, compared to un-grazing, heavy grazing significantly increased soil compaction and reduced SOC, NO3-, and soil moisture. Moderate grazing significantly increased soil compaction and alkalinity and reduced SOC and TN. Light grazing significantly increased SOC and NH4+. Cattle grazing impacts on soil compaction, SOC, TN, and available K were higher than sheep grazing, but lower for PR. Climate significantly impacted grazing effects on SOM, TN, available P, NH4+, EC, CEC, and PR. Heavy grazing can be more detrimental to soil quality based on BD, SOC, TN, C: N, WC, and K than moderate and light grazing. However, global grazing intensities did not significantly impact most of the 15 soil properties, and the grazing effects on them had insignificant changes over the years.
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Affiliation(s)
- Liming Lai
- Department of Agronomy, Hetao College, Bayannur, Inner Mongolia, China
- Department of Agronomy, Horticulture and Plant Sciences, South Dakota State University, Brookings, South Dakota, United States of America
- * E-mail:
| | - Sandeep Kumar
- Department of Agronomy, Horticulture and Plant Sciences, South Dakota State University, Brookings, South Dakota, United States of America
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Foster CN, Banks SC, Cary GJ, Johnson CN, Lindenmayer DB, Valentine LE. Animals as Agents in Fire Regimes. Trends Ecol Evol 2020; 35:346-356. [DOI: 10.1016/j.tree.2020.01.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 12/17/2019] [Accepted: 01/15/2020] [Indexed: 01/08/2023]
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24
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Sandom CJ, Middleton O, Lundgren E, Rowan J, Schowanek SD, Svenning JC, Faurby S. Trophic rewilding presents regionally specific opportunities for mitigating climate change. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190125. [PMID: 31983340 PMCID: PMC7017765 DOI: 10.1098/rstb.2019.0125] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2019] [Indexed: 01/09/2023] Open
Abstract
Large-bodied mammalian herbivores can influence processes that exacerbate or mitigate climate change. Herbivore impacts are, in turn, influenced by predators that place top-down forcing on prey species within a given body size range. Here, we explore how the functional composition of terrestrial large-herbivore and -carnivore guilds varies between three mammal distribution scenarios: Present-Natural, Current-Day and Extant-Native Trophic (ENT) Rewilding. Considering the effects of herbivore species weakly influenced by top-down forcing, we quantify the relative influence keystone large-herbivore guilds have on methane emissions, woody vegetation expansion, fire dynamics, large-seed dispersal, and nitrogen and phosphorus transport potential. We find strong regional differences in the number of herbivores under weak top-down regulation between our three scenarios, with important implications for how they will influence climate change relevant processes. Under the Present-Natural non-ruminant, megaherbivore, browsers were a particularly important guild across much of the world. Megaherbivore extinction and range contraction and the arrival of livestock mean large, ruminant, grazers have become more dominant. ENT Rewilding can restore the Afrotropics and the Indo-Malay realm to the Present-Natural benchmark, but causes top-down forcing of the largest herbivores to become commonplace elsewhere. ENT Rewilding will reduce methane emissions, but does not maximize natural climate solution potential. This article is part of the theme issue 'Climate change and ecosystems: threats, opportunities and solutions'.
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Affiliation(s)
- Christopher J. Sandom
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
- Sussex Sustainability Research Programme (SSRP), University of Sussex, Brighton BN1 9QG, UK
| | - Owen Middleton
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
| | - Erick Lundgren
- Centre for Compassionate Conservation, School of Life Sciences, University of Technology, Sydney, Australia
| | - John Rowan
- Department of Anthropology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Simon D. Schowanek
- Section for Ecoinformatics and Biodiversity, Department of Bioscience, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark
- Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Aarhus University, Aarhus, Denmark
| | - Jens-Christian Svenning
- Section for Ecoinformatics and Biodiversity, Department of Bioscience, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark
- Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Aarhus University, Aarhus, Denmark
| | - Søren Faurby
- Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE 405 30, Göteborg, Sweden
- Gothenburg Global Biodiversity Centre, Box 461, SE 405 30, Göteborg, Sweden
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25
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Probert JR, Parr CL, Holdo RM, Anderson TM, Archibald S, Courtney Mustaphi CJ, Dobson AP, Donaldson JE, Hopcraft GC, Hempson GP, Morrison TA, Beale CM. Anthropogenic modifications to fire regimes in the wider Serengeti-Mara ecosystem. GLOBAL CHANGE BIOLOGY 2019; 25:3406-3423. [PMID: 31282085 PMCID: PMC6852266 DOI: 10.1111/gcb.14711] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 05/02/2019] [Indexed: 06/09/2023]
Abstract
Fire is a key driver in savannah systems and widely used as a land management tool. Intensifying human land uses are leading to rapid changes in the fire regimes, with consequences for ecosystem functioning and composition. We undertake a novel analysis describing spatial patterns in the fire regime of the Serengeti-Mara ecosystem, document multidecadal temporal changes and investigate the factors underlying these patterns. We used MODIS active fire and burned area products from 2001 to 2014 to identify individual fires; summarizing four characteristics for each detected fire: size, ignition date, time since last fire and radiative power. Using satellite imagery, we estimated the rate of change in the density of livestock bomas as a proxy for livestock density. We used these metrics to model drivers of variation in the four fire characteristics, as well as total number of fires and total area burned. Fires in the Serengeti-Mara show high spatial variability-with number of fires and ignition date mirroring mean annual precipitation. The short-term effect of rainfall decreases fire size and intensity but cumulative rainfall over several years leads to increased standing grass biomass and fuel loads, and, therefore, in larger and hotter fires. Our study reveals dramatic changes over time, with a reduction in total number of fires and total area burned, to the point where some areas now experience virtually no fire. We suggest that increasing livestock numbers are driving this decline, presumably by inhibiting fire spread. These temporal patterns are part of a global decline in total area burned, especially in savannahs, and we caution that ecosystem functioning may have been compromised. Land managers and policy formulators need to factor in rapid fire regime modifications to achieve management objectives and maintain the ecological function of savannah ecosystems.
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Affiliation(s)
- James R. Probert
- Department of Earth, Ocean & Ecological SciencesUniversity of LiverpoolLiverpoolUK
| | - Catherine L. Parr
- Department of Earth, Ocean & Ecological SciencesUniversity of LiverpoolLiverpoolUK
- Centre for African EcologySchool of Animal, Plant and Environmental SciencesUniversity of the WitwatersrandJohannesburgSouth Africa
- Department of Zoology & EntomologyUniversity of PretoriaPretoriaSouth Africa
| | - Ricardo M. Holdo
- Centre for African EcologySchool of Animal, Plant and Environmental SciencesUniversity of the WitwatersrandJohannesburgSouth Africa
- Odum School of EcologyUniversity of GeorgiaAthensGeorgia
| | | | - Sally Archibald
- Centre for African EcologySchool of Animal, Plant and Environmental SciencesUniversity of the WitwatersrandJohannesburgSouth Africa
- Natural Resources and the Environment, CSIRPretoriaSouth Africa
| | - Colin J. Courtney Mustaphi
- Geoecology, Department of Environmental SciencesUniversity of BaselBaselSwitzerland
- Institutionen för arkeologi och antik historiaUppsala UniversitetUppsalaSweden
- York Institute for Tropical Ecosystems, Environment DepartmentUniversity of YorkYorkUK
| | - Andrew P. Dobson
- Ecology and Evolutionary BiologyPrinceton UniversityPrincetonNew Jersey
| | - Jason E. Donaldson
- Centre for African EcologySchool of Animal, Plant and Environmental SciencesUniversity of the WitwatersrandJohannesburgSouth Africa
| | - Grant C. Hopcraft
- Institute of Biodiversity, Animal Health and Comparative MedicineUniversity of GlasgowGlasgowUK
| | - Gareth P. Hempson
- Centre for African EcologySchool of Animal, Plant and Environmental SciencesUniversity of the WitwatersrandJohannesburgSouth Africa
- South African Environmental Observation Network (SAEON), Ndlovu NodePhalaborwaSouth Africa
| | - Thomas A. Morrison
- Institute of Biodiversity, Animal Health and Comparative MedicineUniversity of GlasgowGlasgowUK
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26
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Wigley BJ, Coetsee C, Kruger LM, Ratnam J, Sankaran M. Ants, fire, and bark traits affect how African savanna trees recover following damage. Biotropica 2019. [DOI: 10.1111/btp.12683] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Benjamin J. Wigley
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
- School of Natural Resource Management Nelson Mandela University George South Africa
| | - Corli Coetsee
- School of Natural Resource Management Nelson Mandela University George South Africa
- Scientific Services Kruger National Park Skukuza South Africa
| | - Laurence M. Kruger
- Organisation for Tropical Studies Skukuza South Africa
- Biology Department University of Cape Town Rondebosch South Africa
| | - Jayashree Ratnam
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
| | - Mahesh Sankaran
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
- School of Biology Faculty of Biological Sciences University of Leeds Leeds UK
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27
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Effect of local topographic heterogeneity on tree species assembly in an Acacia-dominated African savanna. JOURNAL OF TROPICAL ECOLOGY 2019. [DOI: 10.1017/s0266467419000014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractStand structure and tree species diversity patterns were examined plot-wide and among four topographically defined habitats (plateau, cliff, low plain and depressions) in a 120-ha permanent plot in an Acacia-dominated savanna in Mpala Ranch, central Kenya. The four habitats were defined by clustering the 3000 quadrats of 20 × 20 m in the plot based on their altitude, slope and convexity. Structural and floristic differences among the four habitats were examined and species-habitat associations were tested for the 30 most abundant species using torus translation randomization tests. The plot included 113 337 trees in 62 species with diameter at knee height ≥ 2 cm (18.4 species ha−1), 41 genera and 23 families. Fabaceae with the genus Acacia were the dominant family, followed by Euphorbiaceae and Ebenaceae. Tree density and basal area were twice as high on low plain and depressions than on the plateau. Species richness was highest in the cliff and was seven times higher than in the adjacent plateau. Half of the species assessed showed significant positive associations with one habitat and 21 showed significant negative associations with at least one habitat. The variation in stand structure and tree species diversity within the Mpala plot shows that topography is among the important drivers of local species distribution and hence the maintenance of tree diversity in savannas.
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28
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Bergstrom BJ, Sensenig RL, Augustine DJ, Young TP. Searching for cover: soil enrichment and herbivore exclusion, not fire, enhance African savanna small‐mammal abundance. Ecosphere 2018. [DOI: 10.1002/ecs2.2519] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
| | - Ryan L. Sensenig
- Department of Biological Sciences Goshen College Goshen Indiana 46526 USA
| | - David J. Augustine
- Rangeland Resources Research Unit USDA–Agricultural Research Service Fort Collins Colorado 80526 USA
| | - Truman P. Young
- Department of Plant Sciences University of California Davis California 95616 USA
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29
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Sensenig RL, Kimuyu DK, Ruiz Guajardo JC, Veblen KE, Riginos C, Young TP. Fire disturbance disrupts an acacia ant-plant mutualism in favor of a subordinate ant species. Ecology 2018; 98:1455-1464. [PMID: 28273343 DOI: 10.1002/ecy.1797] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 02/07/2017] [Accepted: 02/24/2017] [Indexed: 11/08/2022]
Abstract
Although disturbance theory has been recognized as a useful framework in examining the stability of ant-plant mutualisms, very few studies have examined the effects of fire disturbance on these mutualisms. In myrmecophyte-dominated savannas, fire and herbivory are key drivers that could influence ant-plant mutualisms by causing complete colony mortality and/or decreasing colony size, which potentially could alter dominance hierarchies if subordinate species are more fire resilient. We used a large-scale, replicated fire experiment to examine long-term effects of fire on acacia-ant community composition. To determine if fire shifted ant occupancy from a competitive dominant to a subordinate ant species, we surveyed the acacia-ant community in 6-7 yr old burn sites and examined how the spatial scale of these burns influenced ant community responses. We then used two short-term fire experiments to explore possible mechanisms for the shifts in community patterns observed. Because survival of ant colonies is largely dependent on their ability to detect and escape an approaching fire, we first tested the evacuation response of all four ant species when exposed to smoke (fire signal). Then to better understand how fire and its interaction with large mammal herbivory affect the density of ants per tree, we quantified ant worker density in small prescribed burns within herbivore exclusion plots. We found clear evidence suggesting that fire disturbance favored the subordinate ant Crematogaster nigriceps more than the dominant and strong mutualist ant C. mimosae, whereby C. nigriceps (1) was the only species to occupy a greater proportion of trees in 6-7 yr old burn sites compared to unburned sites, (2) had higher burn/unburn tree ratios with increasing burn size, and (3) evacuated significantly faster than C. mimosae in the presence of smoke. Fire and herbivory had opposite effects on ant density per meter of branch for both C. nigriceps and C. mimosae, with fire decreasing ant densities per meter of branch and the presence of large herbivores increasing ant density. Taken together, these experiments suggest that major ecosystem disturbances like fire can disrupt mutualistic associations and maintain diversity in partner quality and identity despite a clear dominance hierarchy.
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Affiliation(s)
- Ryan L Sensenig
- Department of Biological Sciences, Goshen College, Goshen, Indiana, 46526, USA.,Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
| | - Duncan K Kimuyu
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,School of Natural Resource Management and Environmental Studies, Karatina University, Karatina, Kenya
| | - Juan C Ruiz Guajardo
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,Department of Evolution and Ecology and Center for Population Biology, University of California, Davis, California, 95616, USA
| | - Kari E Veblen
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Corinna Riginos
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,Northern Rockies Conservation Cooperative, Jackson, Wyoming, 83001, USA.,Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, 82071, USA
| | - Truman P Young
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.,Department of Plant Sciences, University of California, Davis, California, 95616, USA
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30
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Johnson CN, Prior LD, Archibald S, Poulos HM, Barton AM, Williamson GJ, Bowman DMJS. Can trophic rewilding reduce the impact of fire in a more flammable world? Philos Trans R Soc Lond B Biol Sci 2018; 373:rstb.2017.0443. [PMID: 30348870 PMCID: PMC6231065 DOI: 10.1098/rstb.2017.0443] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2018] [Indexed: 12/02/2022] Open
Abstract
Large vertebrates affect fire regimes in several ways: by consuming plant matter that would otherwise accumulate as fuel; by controlling and varying the density of vegetation; and by engineering the soil and litter layer. These processes can regulate the frequency, intensity and extent of fire. The evidence for these effects is strongest in environments with intermediate rainfall, warm temperatures and graminoid-dominated ground vegetation. Probably, extinction of Quaternary megafauna triggered increased biomass burning in many such environments. Recent and continuing declines of large vertebrates are likely to be significant contributors to changes in fire regimes and vegetation that are currently being experienced in many parts of the world. To date, rewilding projects that aim to restore large herbivores have paid little attention to the value of large animals in moderating fire regimes. Rewilding potentially offers a powerful tool for managing the risks of wildfire and its impacts on natural and human values. This article is part of the theme issue ‘Trophic rewilding: consequences for ecosystems under global change’.
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Affiliation(s)
- Christopher N Johnson
- School of Natural Sciences and Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - Lynda D Prior
- School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - Sally Archibald
- Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag, Johannesburg, South Africa
| | - Helen M Poulos
- College of the Environment, Wesleyan University, 284 High St., Middletown, CT 06459, USA
| | - Andrew M Barton
- Department of Biology, University of Maine at Farmington, 173 High Street, Preble Hall, Farmington, ME 04938, USA
| | - Grant J Williamson
- School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
| | - David M J S Bowman
- School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
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31
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Andersen AN. Responses of ant communities to disturbance: Five principles for understanding the disturbance dynamics of a globally dominant faunal group. J Anim Ecol 2018; 88:350-362. [PMID: 30280380 DOI: 10.1111/1365-2656.12907] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2018] [Accepted: 08/31/2018] [Indexed: 01/30/2023]
Abstract
Ecological disturbance is fundamental to the dynamics of biological communities, yet a conceptual framework for understanding the responses of faunal communities to disturbance remains elusive. Here, I propose five principles for understanding the disturbance dynamics of ants-a globally dominant faunal group that is widely used as bioindicators in land management, which appear to have wide applicability to other taxa. These principles are as follows: (1) The most important effects of habitat disturbance on ants are typically indirect, through its effects on habitat structure, microclimate, resource availability and competitive interactions; (2) habitat openness is a key driver of variation in ant communities; (3) ant species responses to disturbance are to a large degree determined by their responses to habitat openness; (4) the same disturbance will have different effects on ants in different habitats, because of different impacts on habitat openness; and (5) ant community responses to the same disturbance will vary according to ant functional composition and biogeographical history in relation to habitat openness. I illustrate these principles using results primarily from studies of ant responses to fire, a dominant agent of disturbance globally, to provide a common disturbance currency for comparative analysis. I argue that many of the principles also apply to other faunal groups and so can be considered as general ecological "laws." As is the case for ants, many impacts of habitat disturbance on other faunal groups are fundamentally related to habitat openness, the effects of disturbance on it and the functional composition of species in relation to it.
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Affiliation(s)
- Alan N Andersen
- Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT, Australia
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32
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Diverse effects of the common hippopotamus on plant communities and soil chemistry. Oecologia 2018; 188:821-835. [DOI: 10.1007/s00442-018-4243-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 08/03/2018] [Indexed: 12/30/2022]
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33
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Goheen JR, Augustine DJ, Veblen KE, Kimuyu DM, Palmer TM, Porensky LM, Pringle RM, Ratnam J, Riginos C, Sankaran M, Ford AT, Hassan AA, Jakopak R, Kartzinel TR, Kurukura S, Louthan AM, Odadi WO, Otieno TO, Wambua AM, Young HS, Young TP. Conservation lessons from large-mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments. Ann N Y Acad Sci 2018; 1429:31-49. [DOI: 10.1111/nyas.13848] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/03/2018] [Accepted: 04/06/2018] [Indexed: 11/26/2022]
Affiliation(s)
- Jacob R. Goheen
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming
- Mpala Research Centre; Nanyuki Kenya
| | | | - Kari E. Veblen
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
| | - Duncan M. Kimuyu
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
- Mpala Research Centre; Nanyuki Kenya
| | - Todd M. Palmer
- Department of Biology; University of Florida; Gainesville Florida
- Mpala Research Centre; Nanyuki Kenya
| | | | - Robert M. Pringle
- Department of Ecology and Evolutionary Biology; Princeton University; Princeton New Jersey
- Mpala Research Centre; Nanyuki Kenya
| | | | | | - Mahesh Sankaran
- National Centre for Biological Sciences, TIFR; Bangalore India
- School of Biology, University of Leeds; Leeds United Kingdom
| | - Adam T. Ford
- Department of Biology; University of British Columbia; Kelowna British Columbia Canada
| | | | - Rhiannon Jakopak
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming
| | - Tyler R. Kartzinel
- Department of Ecology and Evolutionary Biology; Brown University; Providence Rhode Island
| | | | | | - Wilfred O. Odadi
- Department of Natural Resources; Egerton University; Egerton Kenya
- Mpala Research Centre; Nanyuki Kenya
| | | | - Alois M. Wambua
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
- Mpala Research Centre; Nanyuki Kenya
| | - Hillary S. Young
- Department of Ecology, Evolution and Marine Biology; University of California; Santa Barbara California
| | - Truman P. Young
- Department of Plant Sciences; University of California; Davis California
- Mpala Research Centre; Nanyuki Kenya
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34
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35
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Eldridge DJ, Delgado-Baquerizo M, Travers SK, Val J, Oliver I, Dorrough JW, Soliveres S. Livestock activity increases exotic plant richness, but wildlife increases native richness, with stronger effects under low productivity. J Appl Ecol 2017. [DOI: 10.1111/1365-2664.12995] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David J. Eldridge
- Office of Environment and Heritage; School of Biological, Earth and Environmental Sciences; c/- Centre for Ecosystem Science; University of New South Wales; Sydney NSW Australia
| | - Manuel Delgado-Baquerizo
- Cooperative Institute for Research in Environmental Sciences; University of Colorado; Boulder CO USA
| | - Samantha K. Travers
- Office of Environment and Heritage; School of Biological, Earth and Environmental Sciences; c/- Centre for Ecosystem Science; University of New South Wales; Sydney NSW Australia
| | - James Val
- Office of Environment and Heritage; Buronga NSW Australia
| | - Ian Oliver
- Office of Environment and Heritage; University of New England; Armidale NSW Australia
- School of Environmental and Rural Science; University of New England; Armidale NSW Australia
| | - Josh W. Dorrough
- School of Environmental and Rural Science; University of New England; Armidale NSW Australia
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36
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Weinstein S, Titcomb G, Agwanda B, Riginos C, Young H. Parasite responses to large mammal loss in an African savanna. Ecology 2017; 98:1839-1848. [PMID: 28403506 DOI: 10.1002/ecy.1858] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 03/01/2017] [Accepted: 04/05/2017] [Indexed: 11/11/2022]
Abstract
Biodiversity loss can alter disease transmission; however, the magnitude and direction of these effects vary widely across ecosystems, scales, and pathogens. Here we experimentally examine the effects of one of the most globally pervasive patterns of biodiversity decline, the selective loss of large wildlife, on infection probability, intensity and population size of a group of common rodent-borne parasites - macroparasitic helminths. Consistent with previous work on vector-borne pathogens, we found that large wildlife removal causes strong and systematic increases of rodent-borne parasites, largely due to increases in rodent density, as rodents are released from competition with larger herbivores. Although we predicted that increased host density would also increase per capita infection among all directly transmitted parasites, this additional amplification occurred for only two of three examined parasites. Furthermore, the actual effects of large mammal loss on per capita infection were mediated by the complex suite of abiotic and biotic factors that regulate parasite transmission. Thus, while these results strongly suggest that large wildlife loss will cause systematic increases in rodent parasite populations, they also underscore the difficulty of making more specific predictions for a given parasite based on simple attributes such as transmission mode or life history strategy. Instead, detailed information on the ecology of each parasite species would be necessary to make more accurate predictions of how biodiversity loss will affect infection.
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Affiliation(s)
- Sara Weinstein
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA
| | - Georgia Titcomb
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.,Mpala Research Centre, Nanyuki, Kenya
| | - Bernard Agwanda
- Zoology Department, Mammalogy Section, National Museums Kenya, Nairobi, Kenya
| | - Corinna Riginos
- Mpala Research Centre, Nanyuki, Kenya.,Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
| | - Hillary Young
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.,Mpala Research Centre, Nanyuki, Kenya
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37
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Dong S, Wolf SA, Lassoie JP, Liu S, Long R, Yi S, Jasra AW, Phuntsho K. Bridging the Gaps between Science and Policy for the Sustainable Management of Rangeland Resources in the Developing World. Bioscience 2017. [DOI: 10.1093/biosci/bix042] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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38
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Kimuyu DM, Veblen KE, Riginos C, Chira RM, Githaiga JM, Young TP. Influence of cattle on browsing and grazing wildlife varies with rainfall and presence of megaherbivores. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2017; 27:786-798. [PMID: 27935669 DOI: 10.1002/eap.1482] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 10/25/2016] [Accepted: 11/15/2016] [Indexed: 06/06/2023]
Abstract
In many savanna ecosystems worldwide, livestock share the landscape and its resources with wildlife. The nature of interactions between livestock and wildlife is a subject of considerable interest and speculation, yet little controlled experimental research has been carried out. Since 1995, we have been manipulating the presence and absence of cattle and large mammalian herbivore wildlife in a Kenyan savanna in order to better understand how different herbivore guilds influence habitat use by specific wildlife species. Using dung counts as a relative assay of herbivore use of the different experimental plots, we found that cattle had a range of effects, mostly negative, on common mesoherbivore species, including both grazers and mixed feeders, but did not have significant effects on megaherbivores. The effect of cattle on most of the mesoherbivore species was contingent on both the presence of megaherbivores and rainfall. In the absence of megaherbivores, wild mesoherbivore dung density was 36% lower in plots that they shared with cattle than in plots they used exclusively, whereas in the presence of megaherbivores, wild mesoherbivore dung density was only 9% lower in plots shared with cattle than plots used exclusively. Cattle appeared to have a positive effect on habitat use by zebra (a grazer) and steinbuck (a browser) during wetter periods of the year but a negative effect during drier periods. Plots to which cattle had access had lower grass and forb cover than plots from which they were excluded, while plots to which megaherbivores had access had more grass cover but less forb cover. Grass cover was positively correlated with zebra and oryx dung density while forb cover was positively correlated with eland dung density. Overall these results suggest that interactions between livestock and wildlife are contingent on rainfall and herbivore assemblage and represent a more richly nuanced set of interactions than the longstanding assertion that cattle simply compete with (grazing) wildlife. Specifically, rainfall and megaherbivores seemed to moderate the negative effects of cattle on some mesoherbivore species. Even if cattle tend to reduce wildlife use of the landscape, managing simultaneously for livestock production (at moderate levels) and biodiversity conservation is possible.
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Affiliation(s)
- Duncan M Kimuyu
- Department of Natural Resources, Karatina University, Karatina, Kenya
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
| | - Kari E Veblen
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Corinna Riginos
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, 82071, USA
| | - Robert M Chira
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - John M Githaiga
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - Truman P Young
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- Department of Plant Sciences, University of California, Davis, California, 95616, USA
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39
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Pringle RM, Prior KM, Palmer TM, Young TP, Goheen JR. Large herbivores promote habitat specialization and beta diversity of African savanna trees. Ecology 2016; 97:2640-2657. [DOI: 10.1002/ecy.1522] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Revised: 06/16/2016] [Accepted: 06/22/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Robert M. Pringle
- Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey 08544 USA
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
| | - Kirsten M. Prior
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
- Department of Biology University of Florida Gainesville Florida 32611 USA
- Department of Biological Sciences Binghamton University State University of New York Binghamton, New York 13920 USA
| | - Todd M. Palmer
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
- Department of Biology University of Florida Gainesville Florida 32611 USA
| | - Truman P. Young
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
- Department of Plant Sciences University of California Davis California 95616 USA
| | - Jacob R. Goheen
- Mpala Research Centre P.O. Box 555 Nanyuki 10400 Kenya
- Department of Zoology and Physiology University of Wyoming Laramie Wyoming 82070 USA
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40
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Odadi WO, Kimuyu DM, Sensenig RL, Veblen KE, Riginos C, Young TP. Fire‐induced negative nutritional outcomes for cattle when sharing habitat with native ungulates in an African savanna. J Appl Ecol 2016. [DOI: 10.1111/1365-2664.12785] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Wilfred O. Odadi
- Department of Natural Resources Egerton University P. O. Box 536‐20115 Egerton Kenya
- Mpala Research Centre P. O. Box 555‐10400 Nanyuki Kenya
| | - Duncan M. Kimuyu
- Mpala Research Centre P. O. Box 555‐10400 Nanyuki Kenya
- Department of Natural Resources Karatina University P. O. Box 1957‐10101 Karatina Kenya
| | - Ryan L. Sensenig
- Department of Biological Sciences Goshen College Goshen IN 46526 USA
| | - Kari E. Veblen
- Mpala Research Centre P. O. Box 555‐10400 Nanyuki Kenya
- Department of Wildland Resources and Ecology Centre Utah State University 5230 Old Main Hill Logan UT 84322 USA
| | - Corinna Riginos
- Mpala Research Centre P. O. Box 555‐10400 Nanyuki Kenya
- Department of Zoology and Physiology University of Wyoming Laramie WY 82071 USA
- Northern Rockies Conservation Cooperative Jackson WY 83001 USA
| | - Truman P. Young
- Mpala Research Centre P. O. Box 555‐10400 Nanyuki Kenya
- Department of Plant Sciences University of California Davis CA 95616 USA
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41
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Veblen KE, Porensky LM, Riginos C, Young TP. Are cattle surrogate wildlife? Savanna plant community composition explained by total herbivory more than herbivore type. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2016; 26:1610-1623. [PMID: 27755702 DOI: 10.1890/15-1367.1] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 12/12/2015] [Accepted: 01/28/2016] [Indexed: 06/06/2023]
Abstract
The widespread replacement of wild ungulate herbivores by domestic livestock in African savannas is composed of two interrelated phenomena: (1) loss or reduction in numbers of individual wildlife species or guilds and (2) addition of livestock to the system. Each can have important implications for plant community dynamics. Yet very few studies have experimentally addressed the individual, combined, and potentially interactive effects of wild vs. domestic herbivore species on herbaceous plant communities within a single system. Additionally, there is little information about whether, and in which contexts, livestock might functionally replace native herbivore wildlife or, alternatively, have fundamentally different effects on plant species composition. The Kenya Long-term Exclosure Experiment, which has been running since 1995, is composed of six treatment combinations of mega-herbivores, meso-herbivore ungulate wildlife, and cattle. We sampled herbaceous vegetation 25 times between 1999 and 2013. We used partial redundancy analysis and linear mixed models to assess effects of herbivore treatments on overall plant community composition and key plant species. Plant communities in the six different herbivore treatments shifted directionally over time and diverged from each other substantially by 2013. Plant community composition was strongly related (R2 = 0.92) to residual plant biomass, a measure of herbivore utilization. Addition of any single herbivore type (cattle, wildlife, or mega-herbivores) caused a shift in plant community composition that was proportional to its removal of plant biomass. These results suggest that overall herbivory pressure, rather than herbivore type or complex interactions among different herbivore types, was the main driver of changes in plant community composition. Individual plant species, however, did respond most strongly to either wild ungulates or cattle. Although these results suggest considerable functional similarity between a suite of native wild herbivores (which included grazers, browsers, and mixed feeders) and cattle (mostly grazers) with respect to understory plant community composition, responses of individual plant species demonstrate that at the plant-population-level impacts of a single livestock species are not functionally identical to those of a diverse group of native herbivores.
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Affiliation(s)
- Kari E Veblen
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA.
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.
| | - Lauren M Porensky
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- USDA-ARS Rangeland Resources Research Unit, Fort Collins, Colorado, 80526, USA
| | - Corinna Riginos
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, 82071, USA
| | - Truman P Young
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- Department of Plant Sciences, University of California, Davis, California, 95616, USA
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42
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Eldridge DJ, Poore AGB, Ruiz-Colmenero M, Letnic M, Soliveres S. Ecosystem structure, function, and composition in rangelands are negatively affected by livestock grazing. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2016; 26:1273-83. [PMID: 27509764 DOI: 10.1890/15-1234] [Citation(s) in RCA: 127] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Reports of positive or neutral effects of grazing on plant species richness have prompted calls for livestock grazing to be used as a tool for managing land for conservation. Grazing effects, however, are likely to vary among different response variables, types, and intensity of grazing, and across abiotic conditions. We aimed to examine how grazing affects ecosystem structure, function, and composition. We compiled a database of 7615 records reporting an effect of grazing by sheep and cattle on 278 biotic and abiotic response variables for published studies across Australia. Using these data, we derived three ecosystem measures based on structure, function, and composition, which were compared against six contrasts of grazing pressure, ranging from low to heavy, two different herbivores (sheep, cattle), and across three different climatic zones. Grazing reduced structure (by 35%), function (24%), and composition (10%). Structure and function (but not composition) declined more when grazed by sheep and cattle together than sheep alone. Grazing reduced plant biomass (40%), animal richness (15%), and plant and animal abundance, and plant and litter cover (25%), but had no effect on plant richness nor soil function. The negative effects of grazing on plant biomass, plant cover, and soil function were more pronounced in drier environments. Grazing effects on plant and animal richness and composition were constant, or even declined, with increasing aridity. Our study represents a comprehensive continental assessment of the implications of grazing for managing Australian rangelands. Grazing effects were largely negative, even at very low levels of grazing. Overall, our results suggest that livestock grazing in Australia is unlikely to produce positive outcomes for ecosystem structure, function, and composition or even as a blanket conservation tool unless reduction in specific response variables is an explicit management objective.
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43
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Fire in the Amazon: impact of experimental fuel addition on responses of ants and their interactions with myrmecochorous seeds. Oecologia 2016; 182:335-46. [DOI: 10.1007/s00442-016-3638-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 04/19/2016] [Indexed: 11/26/2022]
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44
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van der Waal C, de Kroon H, van Langevelde F, de Boer WF, Heitkönig IMA, Slotow R, Pretorius Y, Prins HHT. Scale-dependent bi-trophic interactions in a semi-arid savanna: how herbivores eliminate benefits of nutrient patchiness to plants. Oecologia 2016; 181:1173-85. [PMID: 27094543 PMCID: PMC4954840 DOI: 10.1007/s00442-016-3627-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 04/03/2016] [Indexed: 11/29/2022]
Abstract
The scale of resource heterogeneity may influence how resources are locally partitioned between co-existing large and small organisms such as trees and grasses in savannas. Scale-related plant responses may, in turn, influence herbivore use of the vegetation. To examine these scale-dependent bi-trophic interactions, we varied fertilizer [(nitrogen (N)/phosphorus (P)/potassium (K)] applications to patches to create different scales of nutrient patchiness (patch size 2 × 2 m, 10 × 10 m, or whole-plot 50 × 50 m) in a large field experiment in intact African savanna. Within-patch fertilizer concentration and the total fertilizer load per plot were independently varied. We found that fertilization increased the leaf N and P concentrations of trees and grasses, resulting in elevated utilization by browsers and grazers. Herbivory off-take was particularly considerable at higher nutrient concentrations. Scale-dependent effects were weak. The net effect of fertilization and herbivory was that plants in fertilized areas tended to grow less and develop smaller rather than larger standing biomass compared to plants growing in areas that remained unfertilized. When all of these effects were considered together at the community (plot) level, herbivory completely eliminated the positive effects of fertilization on the plant community. While this was true for all scales of fertilization, grasses tended to profit more from coarse-grained fertilization and trees from fine-grained fertilization. We conclude that in herbivore-dominated communities, such as the African savanna, nutrient patchiness results in the herbivore community profiting rather more than the plant community, irrespective of the scale of patchiness. At the community level, the allometric scaling theory's prediction of plant-and probably also animal-production does not hold or may even be reversed as a result of complex bi-trophic interactions.
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Affiliation(s)
- Cornelis van der Waal
- Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3A, 6708 PD, Wageningen, The Netherlands.,Agri-Ecological Services, PO Box 28, Omaruru, Namibia
| | - Hans de Kroon
- Department of Experimental Plant Ecology, Institute for Water and Wetland Research, Radboud University, PO Box 9010, 6500 GL, Nijmegen, The Netherlands.
| | - Frank van Langevelde
- Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3A, 6708 PD, Wageningen, The Netherlands
| | - Willem F de Boer
- Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3A, 6708 PD, Wageningen, The Netherlands
| | - Ignas M A Heitkönig
- Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3A, 6708 PD, Wageningen, The Netherlands
| | - Rob Slotow
- School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban, 4000, South Africa
| | - Yolanda Pretorius
- Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3A, 6708 PD, Wageningen, The Netherlands.,Centre for Wildlife Management, University of Pretoria, Private bag X20, Hatfield, Pretoria, South Africa
| | - Herbert H T Prins
- Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3A, 6708 PD, Wageningen, The Netherlands
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45
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Davies KW, Bates JD, Boyd CS, Svejcar TJ. Prefire grazing by cattle increases postfire resistance to exotic annual grass (Bromus tectorum) invasion and dominance for decades. Ecol Evol 2016; 6:3356-66. [PMID: 27103990 PMCID: PMC4833623 DOI: 10.1002/ece3.2127] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 02/22/2016] [Accepted: 03/20/2016] [Indexed: 11/21/2022] Open
Abstract
Fire, herbivory and their interaction influence plant community dynamics. However, little is known about the influence of prefire herbivory on postfire plant community response, particularly long‐term resistance to postfire exotic plant invasion in areas that historically experienced limited large herbivore pressure and infrequent, periodic fires. We investigated the long‐term postfire effects of prefire herbivory by cattle, an exotic herbivore, in Artemisia (sagebrush) plant communities in the northern Great Basin, USA. Study areas were moderately grazed or not grazed by cattle since 1936 and then were burned in 1993. Plant community response was measured the 19th through the 22nd year postfire. Prior to burning exotic annual grass presence was minimal (<0.5% foliar cover) and plant community characteristics were similar between grazed and ungrazed treatments, with the exception of litter biomass being two times greater in the ungrazed treatment. Two decades postfire, Bromus tectorum L., an exotic annual grass, dominated the ungrazed treatment. Native bunchgrasses, species richness, and soil biological crusts were greater in prefire grazed areas compared to ungrazed areas. These results suggest that moderate prefire herbivory by cattle increased the resistance of the plant community to postfire invasion and dominance by B. tectorum. We presume that herbivory reduced mortality of large perennial bunchgrasses during the fire by reducing fine fuel (litter) and subsequently burn temperatures. Synthesis: This research demonstrates that a moderate disturbance (herbivory) may mediate the effects of a subsequent disturbance (fire). The effects of disturbances are not independent; therefore quantifying these interactions is critical to preventing oversimplification of complex plant community dynamics and guiding the conservation of endangered ecosystems.
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Affiliation(s)
- Kirk W Davies
- Eastern Oregon Agricultural Research Center USDA - Agricultural Research Service 67826-A Hwy 205 Burns Oregon
| | - Jon D Bates
- Eastern Oregon Agricultural Research Center USDA - Agricultural Research Service 67826-A Hwy 205 Burns Oregon
| | - Chad S Boyd
- Eastern Oregon Agricultural Research Center USDA - Agricultural Research Service 67826-A Hwy 205 Burns Oregon
| | - Tony J Svejcar
- Eastern Oregon Agricultural Research Center USDA - Agricultural Research Service 67826-A Hwy 205 Burns Oregon
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Foster CN, Sato CF, Lindenmayer DB, Barton PS. Integrating theory into disturbance interaction experiments to better inform ecosystem management. GLOBAL CHANGE BIOLOGY 2016; 22:1325-1335. [PMID: 26554638 DOI: 10.1111/gcb.13155] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 10/05/2015] [Indexed: 06/05/2023]
Abstract
Managing multiple, interacting disturbances is a key challenge to biodiversity conservation, and one that will only increase as global change drivers continue to alter disturbance regimes. Theoretical studies have highlighted the importance of a mechanistic understanding of stressor interactions for improving the prediction and management of interactive effects. However, many conservation studies are not designed or interpreted in the context of theory and instead focus on case-specific management questions. This is a problem as it means that few studies test the relationships highlighted in theoretical models as being important for ecological management. We explore the extent of this problem among studies of interacting disturbances by reviewing recent experimental studies of the interaction between fire and grazing in terrestrial ecosystems. Interactions between fire and grazing can occur via a number of pathways; one disturbance can modify the other's likelihood, intensity or spatial distribution, or one disturbance can alter the other's impacts on individual organisms. The strength of such interactions will vary depending on disturbance attributes (e.g. size or intensity), and this variation is likely to be nonlinear. We show that few experiments testing fire-grazing interactions are able to identify the mechanistic pathway driving an observed interaction, and most are unable to detect nonlinear effects. We demonstrate how these limitations compromise the ability of experimental studies to effectively inform ecological management. We propose a series of adjustments to the design of disturbance interaction experiments that would enable tests of key theoretical pathways and provide the deeper ecological understanding necessary for effective management. Such considerations are relevant to studies of a broad range of ecological interactions and are critical to informing the management of disturbance regimes in the context of accelerating global change.
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Affiliation(s)
- Claire N Foster
- Fenner School of Environment and Society, The Australian National University, 141 Linnaeus Way, Acton, ACT, 2601, Australia
| | - Chloe F Sato
- Fenner School of Environment and Society, The Australian National University, 141 Linnaeus Way, Acton, ACT, 2601, Australia
- Australian Research Council Centre of Excellence for Environmental Decisions, National Environmental Research Program Environmental Decisions Hub, The Australian National University, 141 Linnaeus Way, Acton, ACT, 2601, Australia
| | - David B Lindenmayer
- Fenner School of Environment and Society, The Australian National University, 141 Linnaeus Way, Acton, ACT, 2601, Australia
- Australian Research Council Centre of Excellence for Environmental Decisions, National Environmental Research Program Environmental Decisions Hub, The Australian National University, 141 Linnaeus Way, Acton, ACT, 2601, Australia
- The Long Term Ecological Research Network, The Australian National University, 141 Linnaeus Way, Acton, ACT, 2601, Australia
| | - Philip S Barton
- Fenner School of Environment and Society, The Australian National University, 141 Linnaeus Way, Acton, ACT, 2601, Australia
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47
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Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation. Proc Natl Acad Sci U S A 2015; 113:847-55. [PMID: 26504223 DOI: 10.1073/pnas.1502545112] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Until recently in Earth history, very large herbivores (mammoths, ground sloths, diprotodons, and many others) occurred in most of the World's terrestrial ecosystems, but the majority have gone extinct as part of the late-Quaternary extinctions. How has this large-scale removal of large herbivores affected landscape structure and ecosystem functioning? In this review, we combine paleo-data with information from modern exclosure experiments to assess the impact of large herbivores (and their disappearance) on woody species, landscape structure, and ecosystem functions. In modern landscapes characterized by intense herbivory, woody plants can persist by defending themselves or by association with defended species, can persist by growing in places that are physically inaccessible to herbivores, or can persist where high predator activity limits foraging by herbivores. At the landscape scale, different herbivore densities and assemblages may result in dynamic gradients in woody cover. The late-Quaternary extinctions were natural experiments in large-herbivore removal; the paleoecological record shows evidence of widespread changes in community composition and ecosystem structure and function, consistent with modern exclosure experiments. We propose a conceptual framework that describes the impact of large herbivores on woody plant abundance mediated by herbivore diversity and density, predicting that herbivore suppression of woody plants is strongest where herbivore diversity is high. We conclude that the decline of large herbivores induces major alterations in landscape structure and ecosystem functions.
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48
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Young HS, Dirzo R, Helgen KM, McCauley DJ, Nunn CL, Snyder P, Veblen KE, Zhao S, Ezenwa VO. Large wildlife removal drives immune defence increases in rodents. Funct Ecol 2015. [DOI: 10.1111/1365-2435.12542] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hillary S. Young
- University of California Santa Barbara Santa Barbara California 93106 USA
- Division of Mammals National Museum of Natural History Smithsonian Institution Washington District of Columbia 20013 USA
- Mpala Research Centre Box 555 Nanyuki Kenya
| | - Rodolfo Dirzo
- Department of Biology Stanford University Stanford California 94305 USA
| | - Kristofer M. Helgen
- Division of Mammals National Museum of Natural History Smithsonian Institution Washington District of Columbia 20013 USA
| | - Douglas J. McCauley
- University of California Santa Barbara Santa Barbara California 93106 USA
- Mpala Research Centre Box 555 Nanyuki Kenya
| | - Charles L. Nunn
- Department of Evolutionary Anthropology Duke University Durham North Carolina 27708 USA
- Duke Global Health Institute Duke University Durham North Carolina 27708 USA
| | - Paul Snyder
- Odum School of Ecology and Department of Infectious Diseases College of Veterinary Medicine University of Georgia Athens Georgia 30602 USA
- Department of Integrative Biology Oregon State University Corvallis Oregon 97331 USA
| | - Kari E. Veblen
- Mpala Research Centre Box 555 Nanyuki Kenya
- Department of Wildland Resources and Ecology Center Utah State University Logan Utah 84322 USA
| | - Serena Zhao
- Division of Mammals National Museum of Natural History Smithsonian Institution Washington District of Columbia 20013 USA
- Mpala Research Centre Box 555 Nanyuki Kenya
| | - Vanessa O. Ezenwa
- Mpala Research Centre Box 555 Nanyuki Kenya
- Odum School of Ecology and Department of Infectious Diseases College of Veterinary Medicine University of Georgia Athens Georgia 30602 USA
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49
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Pringle RM, Kimuyu DM, Sensenig RL, Palmer TM, Riginos C, Veblen KE, Young TP. Synergistic effects of fire and elephants on arboreal animals in an African savanna. J Anim Ecol 2015; 84:1637-45. [PMID: 26033175 DOI: 10.1111/1365-2656.12404] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Accepted: 05/23/2015] [Indexed: 11/30/2022]
Abstract
Disturbance is a crucial determinant of animal abundance, distribution and community structure in many ecosystems, but the ways in which multiple disturbance types interact remain poorly understood. The effects of multiple-disturbance interactions can be additive, subadditive or super-additive (synergistic). Synergistic effects in particular can accelerate ecological change; thus, characterizing such synergies, the conditions under which they arise, and how long they persist has been identified as a major goal of ecology. We factorially manipulated two principal sources of disturbance in African savannas, fire and elephants, and measured their independent and interactive effects on the numerically dominant vertebrate (the arboreal gekkonid lizard Lygodactylus keniensis) and invertebrate (a guild of symbiotic Acacia ants) animal species in a semi-arid Kenyan savanna. Elephant exclusion alone (minus fire) had negligible effects on gecko density. Fire alone (minus elephants) had negligible effects on gecko density after 4 months, but increased gecko density twofold after 16 months, likely because the decay of fire-damaged woody biomass created refuges and nest sites for geckos. In the presence of elephants, fire increased gecko density nearly threefold within 4 months of the experimental burn; this occurred because fire increased the incidence of elephant damage to trees, which in turn improved microhabitat quality for geckos. However, this synergistic positive effect of fire and elephants attenuated over the ensuing year, such that only the main effect of fire was evident after 16 months. Fire also altered the structure of symbiotic plant-ant assemblages occupying the dominant tree species (Acacia drepanolobium); this influenced gecko habitat selection but did not explain the synergistic effect of fire and elephants. However, fire-driven shifts in plant-ant occupancy may have indirectly mediated this effect by increasing trees' susceptibility to elephant damage. Our findings confirm the importance of fire × elephant interactions in structuring arboreal wildlife populations. Where habitat modification by megaherbivores facilitates co-occurring species, fire may amplify these effects in the short term by increasing the frequency or intensity of herbivory, leading to synergy. In the longer term, tree mortality due to both top kill by fire and toppling by large herbivores may reduce overall microhabitat availability, eliminating the synergy.
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Affiliation(s)
- Robert M Pringle
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA.,Mpala Research Centre, PO Box 555, Nanyuki, Kenya
| | - Duncan M Kimuyu
- Mpala Research Centre, PO Box 555, Nanyuki, Kenya.,Department of Natural Resources, Karatina University, Karatina, Kenya
| | - Ryan L Sensenig
- Mpala Research Centre, PO Box 555, Nanyuki, Kenya.,Department of Biological Sciences, Goshen College, Goshen, IN, 46526, USA
| | - Todd M Palmer
- Mpala Research Centre, PO Box 555, Nanyuki, Kenya.,Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Corinna Riginos
- Mpala Research Centre, PO Box 555, Nanyuki, Kenya.,Department of Zoology and Physiology, University of Wyoming, Laramie, WY, 82071, USA
| | - Kari E Veblen
- Mpala Research Centre, PO Box 555, Nanyuki, Kenya.,Department of Wildland Resources and Ecology Center, Utah State University, Logan, UT, 84322, USA
| | - Truman P Young
- Mpala Research Centre, PO Box 555, Nanyuki, Kenya.,Department of Plant Sciences, University of California, Davis, CA, 95616, USA
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50
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Foster CN, Barton PS, Sato CF, Wood JT, MacGregor CI, Lindenmayer DB. Herbivory and fire interact to affect forest understory habitat, but not its use by small vertebrates. Anim Conserv 2015. [DOI: 10.1111/acv.12210] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- C. N. Foster
- Fenner School of Environment and Society; The Australian National University; Canberra ACT Australia
| | - P. S. Barton
- Fenner School of Environment and Society; The Australian National University; Canberra ACT Australia
| | - C. F. Sato
- Fenner School of Environment and Society; The Australian National University; Canberra ACT Australia
- Australian Research Council Centre of Excellence for Environmental Decisions and the National Environmental Research Program Environmental Decisions Hub; The Australian National University; Canberra ACT Australia
| | - J. T. Wood
- Fenner School of Environment and Society; The Australian National University; Canberra ACT Australia
| | - C. I. MacGregor
- Fenner School of Environment and Society; The Australian National University; Canberra ACT Australia
- Australian Research Council Centre of Excellence for Environmental Decisions and the National Environmental Research Program Environmental Decisions Hub; The Australian National University; Canberra ACT Australia
- The Long-term Ecological Research Network; The Australian National University; Canberra ACT Australia
| | - D. B. Lindenmayer
- Fenner School of Environment and Society; The Australian National University; Canberra ACT Australia
- Australian Research Council Centre of Excellence for Environmental Decisions and the National Environmental Research Program Environmental Decisions Hub; The Australian National University; Canberra ACT Australia
- The Long-term Ecological Research Network; The Australian National University; Canberra ACT Australia
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