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Felton AJ, Knapp AK, Smith MD. Carbon exchange responses of a mesic grassland to an extreme gradient of precipitation. Oecologia 2018; 189:565-576. [PMID: 30411149 DOI: 10.1007/s00442-018-4284-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 10/21/2018] [Indexed: 11/24/2022]
Abstract
Growing evidence indicates that ecosystem processes may be differentially sensitive to dry versus wet years, and that current understanding of how precipitation affects ecosystem processes may not be predictive of responses to extremes. In an experiment within a mesic grassland, we addressed this uncertainty by assessing responses of two key carbon exchange processes-aboveground net primary production (ANPP) and soil respiration (Rs)-to an extensive gradient of growing season precipitation. This gradient comprised 11 levels that specifically included extreme values in precipitation; defined as the 1st, 5th, 95th, and 99th percentiles of the 112-year climate record. Across treatments, our experimental precipitation gradient linearly increased soil moisture availability in the rooting zone (upper 20 cm). Relative to ANPP under nominal precipitation amounts (defined as between the 15th and 85th percentiles), the magnitude of ANPP responses were greatest to extreme increases in precipitation, with an underlying linear response to both precipitation and soil moisture gradients. By contrast, Rs exhibited marginally greater responses to dry versus wet extremes, with a saturating relationship best explaining responses of Rs to both precipitation and soil moisture. Our findings indicate a linear relationship between ANPP and precipitation after incorporating responses to precipitation extremes in the ANPP-precipitation relationship, yet in contrast saturating responses of Rs. As a result, current linear ANPP-precipitation relationships (up to ~ 1000 mm) within mesic grasslands appear to hold as appropriate benchmarks for ecosystems models, yet such models should incorporate nonlinearities in responses of Rs amid increased frequencies and magnitudes of precipitation extremes.
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Affiliation(s)
- Andrew J Felton
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, 251 Pitkin Street, Fort Collins, CO, 80523, USA.
| | - Alan K Knapp
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, 251 Pitkin Street, Fort Collins, CO, 80523, USA
| | - Melinda D Smith
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, 251 Pitkin Street, Fort Collins, CO, 80523, USA
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Asbjornsen H, Campbell JL, Jennings KA, Vadeboncoeur MA, McIntire C, Templer PH, Phillips RP, Bauerle TL, Dietze MC, Frey SD, Groffman PM, Guerrieri R, Hanson PJ, Kelsey EP, Knapp AK, McDowell NG, Meir P, Novick KA, Ollinger SV, Pockman WT, Schaberg PG, Wullschleger SD, Smith MD, Rustad LE. Guidelines and considerations for designing field experiments simulating precipitation extremes in forest ecosystems. Methods Ecol Evol 2018. [DOI: 10.1111/2041-210x.13094] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Heidi Asbjornsen
- Department of Natural Resources and the EnvironmentUniversity of New Hampshire Durham New Hampshire
- Earth Systems Research CenterInstitute for Earth, Oceans, and SpaceUniversity of New Hampshire Durham New Hampshire
| | - John L. Campbell
- Northern Research StationUSDA Forest Service Durham New Hampshire
| | - Katie A. Jennings
- Department of Natural Resources and the EnvironmentUniversity of New Hampshire Durham New Hampshire
- Earth Systems Research CenterInstitute for Earth, Oceans, and SpaceUniversity of New Hampshire Durham New Hampshire
| | - Matthew A. Vadeboncoeur
- Earth Systems Research CenterInstitute for Earth, Oceans, and SpaceUniversity of New Hampshire Durham New Hampshire
| | - Cameron McIntire
- Department of Natural Resources and the EnvironmentUniversity of New Hampshire Durham New Hampshire
| | | | | | - Taryn L. Bauerle
- School of Integrative Plant ScienceCornell University Ithaca New York
| | - Michael C. Dietze
- Department of Earth and EnvironmentBoston University Boston Massachusetts
| | - Serita D. Frey
- Department of Natural Resources and the EnvironmentUniversity of New Hampshire Durham New Hampshire
| | - Peter M. Groffman
- Department of Earth and Environmental SciencesAdvanced Science Research Center at the Graduate Center of the City University of New York and Brooklyn College New York New York
| | - Rosella Guerrieri
- Centre for Ecological Research and Forestry Applications (CREAF)Universidad Autonoma de Barcelona Barcelona Spain
| | - Paul J. Hanson
- Environmental Sciences DivisionOak Ridge National Laboratory Oak Ridge Tennessee
| | - Eric P. Kelsey
- Department of Atmospheric Science and ChemistryPlymouth State University Plymouth New Hampshire
- Mount Washington Observatory North Conway New Hampshire
| | - Alan K. Knapp
- Department of Biology and Graduate Degree Program in EcologyColorado State University Fort Collins Colorado
| | | | - Patrick Meir
- Research School of BiologyAustralian National University Canberra ACT Australia
- School of GeosciencesUniversity of Edinburgh Edinburgh UK
| | - Kimberly A. Novick
- School of Public and Environmental AffairsIndiana University Bloomington Indiana
| | - Scott V. Ollinger
- Department of Natural Resources and the EnvironmentUniversity of New Hampshire Durham New Hampshire
| | - Will T. Pockman
- Department of BiologyUniversity of New Mexico Albuquerque New Mexico
| | | | - Stan D. Wullschleger
- Environmental Sciences DivisionOak Ridge National Laboratory Oak Ridge Tennessee
| | - Melinda D. Smith
- Department of Biology and Graduate Degree Program in EcologyColorado State University Fort Collins Colorado
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53
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Knapp AK, Carroll CJW, Griffin-Nolan RJ, Slette IJ, Chaves FA, Baur LE, Felton AJ, Gray JE, Hoffman AM, Lemoine NP, Mao W, Post AK, Smith MD. A reality check for climate change experiments: Do they reflect the real world? Ecology 2018; 99:2145-2151. [PMID: 30054917 DOI: 10.1002/ecy.2474] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 07/05/2018] [Indexed: 11/08/2022]
Abstract
Experiments are widely used in ecology, particularly for assessing global change impacts on ecosystem function. However, results from experiments often are inconsistent with observations made under natural conditions, suggesting the need for rigorous comparisons of experimental and observational studies. We conducted such a "reality check" for a grassland ecosystem by compiling results from nine independently conducted climate change experiments. Each experiment manipulated growing season precipitation (GSP) and measured responses in aboveground net primary production (ANPP). We compared results from experiments with long-term (33-yr) annual precipitation and ANPP records to ask if collectively (n = 44 experiment-years) experiments yielded estimates of ANPP, rain-use efficiency (RUE, grams per square meter ANPP per mm precipitation), and the relationship between GSP and ANPP comparable to observations. We found that mean ANPP and RUE from experiments did not deviate from observations. Experiments and observational data also yielded similar functional relationships between ANPP and GSP, but only within the range of historically observed GSP. Fewer experiments imposed extreme levels of GSP (outside the observed 33-yr record), but when these were included, they altered the GSP-ANPP relationship. This result underscores the need for more experiments imposing extreme precipitation levels to resolve how forecast changes in climate regimes will affect ecosystem function in the future.
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Affiliation(s)
- Alan K Knapp
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Charles J W Carroll
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Robert J Griffin-Nolan
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Ingrid J Slette
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Francis A Chaves
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Lauren E Baur
- Department of Biology, University of New Mexico, Albuquerque, New Mexico, 87131, USA
| | - Andrew J Felton
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Jesse E Gray
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Ava M Hoffman
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Nathan P Lemoine
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Wei Mao
- Northwest Institute of Eco-Environment and Resource, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Alison K Post
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Melinda D Smith
- Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
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Abstract
The metabolic activity of water-limited ecosystems is strongly linked to the timing and magnitude of precipitation pulses that can trigger disproportionately high (i.e., hot-moments) ecosystem CO2 fluxes. We analyzed over 2-years of continuous measurements of soil CO2 efflux (Fs) under vegetation (Fsveg) and at bare soil (Fsbare) in a water-limited grassland. The continuous wavelet transform was used to: (a) describe the temporal variability of Fs; (b) test the performance of empirical models ranging in complexity; and (c) identify hot-moments of Fs. We used partial wavelet coherence (PWC) analysis to test the temporal correlation between Fs with temperature and soil moisture. The PWC analysis provided evidence that soil moisture overshadows the influence of soil temperature for Fs in this water limited ecosystem. Precipitation pulses triggered hot-moments that increased Fsveg (up to 9000%) and Fsbare (up to 17,000%) with respect to pre-pulse rates. Highly parameterized empirical models (using support vector machine (SVM) or an 8-day moving window) are good approaches for representing the daily temporal variability of Fs, but SVM is a promising approach to represent high temporal variability of Fs (i.e., hourly estimates). Our results have implications for the representation of hot-moments of ecosystem CO2 fluxes in these globally distributed ecosystems.
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55
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McDowell N, Allen CD, Anderson-Teixeira K, Brando P, Brienen R, Chambers J, Christoffersen B, Davies S, Doughty C, Duque A, Espirito-Santo F, Fisher R, Fontes CG, Galbraith D, Goodsman D, Grossiord C, Hartmann H, Holm J, Johnson DJ, Kassim AR, Keller M, Koven C, Kueppers L, Kumagai T, Malhi Y, McMahon SM, Mencuccini M, Meir P, Moorcroft P, Muller-Landau HC, Phillips OL, Powell T, Sierra CA, Sperry J, Warren J, Xu C, Xu X. Drivers and mechanisms of tree mortality in moist tropical forests. THE NEW PHYTOLOGIST 2018; 219:851-869. [PMID: 29451313 DOI: 10.1111/nph.15027] [Citation(s) in RCA: 169] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 12/19/2017] [Indexed: 05/22/2023]
Abstract
Tree mortality rates appear to be increasing in moist tropical forests (MTFs) with significant carbon cycle consequences. Here, we review the state of knowledge regarding MTF tree mortality, create a conceptual framework with testable hypotheses regarding the drivers, mechanisms and interactions that may underlie increasing MTF mortality rates, and identify the next steps for improved understanding and reduced prediction. Increasing mortality rates are associated with rising temperature and vapor pressure deficit, liana abundance, drought, wind events, fire and, possibly, CO2 fertilization-induced increases in stand thinning or acceleration of trees reaching larger, more vulnerable heights. The majority of these mortality drivers may kill trees in part through carbon starvation and hydraulic failure. The relative importance of each driver is unknown. High species diversity may buffer MTFs against large-scale mortality events, but recent and expected trends in mortality drivers give reason for concern regarding increasing mortality within MTFs. Models of tropical tree mortality are advancing the representation of hydraulics, carbon and demography, but require more empirical knowledge regarding the most common drivers and their subsequent mechanisms. We outline critical datasets and model developments required to test hypotheses regarding the underlying causes of increasing MTF mortality rates, and improve prediction of future mortality under climate change.
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Affiliation(s)
- Nate McDowell
- Pacific Northwest National Laboratory, Richland, WA, 99354, USA
| | - Craig D Allen
- US Geological Survey, Fort Collins Science Center, New Mexico Landscapes Field Station, Los Alamos, NM, 87544, USA
| | - Kristina Anderson-Teixeira
- Center for Tropical Forest Science-Forest Global Earth Observatory, Smithsonian Tropical Research Institute, Washington, DC, 20036, USA
- Conservation Ecology Center, Smithsonian Conservation Biology Institute, National Zoological Park, Front Royal, VA, 22630, USA
| | - Paulo Brando
- Woods Hole Research Center, 149 Woods Hole Road, Falmouth, MA, 02450, USA
- Instituto de Pesquisa Ambiental de Amazonia, Lago Norte, Brasilia, Brazil
| | - Roel Brienen
- School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Jeff Chambers
- Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Brad Christoffersen
- Department of Biology and School of Earth, Environmental and Marine Sciences, University of Texas Rio Grande Valley, Edinburg, TX, 78539, USA
| | - Stuart Davies
- Center for Tropical Forest Science-Forest Global Earth Observatory, Smithsonian Tropical Research Institute, Washington, DC, 20036, USA
| | - Chris Doughty
- SICCS, Northern Arizona University, Flagstaff, AZ, 86001, USA
| | - Alvaro Duque
- Departmento de Ciencias Forestales, Universidad Nacional de Columbia, Medellín, Columbia
| | | | - Rosie Fisher
- National Center for Atmospheric Research, Boulder, CO, 80305, USA
| | - Clarissa G Fontes
- Department of Integrative Biology, University of California at Berkeley, Berkeley, CA, 94720, USA
| | - David Galbraith
- School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Devin Goodsman
- Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | | | - Henrik Hartmann
- Department of Biogeochemical Processes, Max Plank Institute for Biogeochemistry, 07745, Jena, Germany
| | - Jennifer Holm
- Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | | | - Abd Rahman Kassim
- Geoinformation Programme, Forestry and Environment Division, Forest Research Institute Malaysia, Selangor, Malaysia
| | - Michael Keller
- International Institute of Tropical Forestry, USDA Jardin Botanico Sur, 1201 Calle Ceiba, San Juan, 00926, Puerto Rico
- Embrapa Agricultural Informatics, Parque Estacao Biologica, Brasilia DF, 70770, Brazil
- Jet Propulsion Laboratory, Pasadena, CA, 91109, USA
| | - Charlie Koven
- Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Lara Kueppers
- Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Energy and Resources Group, University of California, Berkeley, CA, 94720, USA
| | - Tomo'omi Kumagai
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 7 Chome-3-1 Hongo, Bunkyo, Tokyo, 113-8654, Japan
| | - Yadvinder Malhi
- Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, OX1 2JD, UK
| | - Sean M McMahon
- Center for Tropical Forest Science-Forest Global Earth Observatory, Smithsonian Tropical Research Institute, Washington, DC, 20036, USA
| | - Maurizio Mencuccini
- ICREA, CREAF, University of Barcelona, Gran Via de les Corts Catalenes, 585 08007, Barcelona, Spain
| | - Patrick Meir
- Australian National University, Acton, Canberra, ACT, 2601, Australia
- School of Geosciences, University of Edinburgh, Old College, South Bridge, Edinburgh, EH8 9YL, UK
| | | | - Helene C Muller-Landau
- Smithsonian Tropical Research Institute, Apartado Postal, 0843-03092, Panamá, República de Panamá
| | - Oliver L Phillips
- School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Thomas Powell
- Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Carlos A Sierra
- Department of Biogeochemical Processes, Max Plank Institute for Biogeochemistry, 07745, Jena, Germany
| | - John Sperry
- University of Utah, Salt Lake City, UT, 84112, USA
| | - Jeff Warren
- Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Chonggang Xu
- Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Xiangtao Xu
- Department of Geosciences, Princeton University, Princeton, NJ, 08544, USA
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56
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Effects of extreme drought on plant nutrient uptake and resorption in rhizomatous vs bunchgrass-dominated grasslands. Oecologia 2018; 188:633-643. [PMID: 30043231 DOI: 10.1007/s00442-018-4232-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 07/18/2018] [Indexed: 10/28/2022]
Abstract
Both the dominance and the mass ratio hypotheses predict that plant internal nutrient cycling in ecosystems is determined by the dominant species within plant communities. We tested this hypothesis under conditions of extreme drought by assessing plant nutrient (N, P and K) uptake and resorption in response to experimentally imposed precipitation reductions in two semiarid grasslands of northern China. These two communities shared similar environmental conditions, but had different dominant species-one was dominated by a rhizomatous grass (Leymus chinensis) and the other by a bunchgrass (Stipa grandis). Results showed that responses of N to drought differed between the two communities with drought decreasing green leaf N concentration and resorption in the community dominated by the rhizomatous grass, but not in the bunchgrass-dominated community. In contrast, negative effects of drought on green leaf P and K concentrations and their resorption efficiencies were consistent across the two communities. Additionally, in each community, the effects of extreme drought on soil N, P and K supply did not change synchronously with that on green leaf N, P and K concentrations, and senesced leaf N, P and K concentrations showed no response to extreme drought. Consistent with the dominance/mass ratio hypothesis, our findings suggest that differences in dominant species and their growth form (i.e., rhizomatous vs bunch grass) play an important nutrient-specific role in mediating plant internal nutrient cycling across communities within a single region.
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57
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Connor EW, Hawkes CV. Effects of extreme changes in precipitation on the physiology of C4 grasses. Oecologia 2018; 188:355-365. [PMID: 29959571 DOI: 10.1007/s00442-018-4212-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 06/21/2018] [Indexed: 12/16/2022]
Abstract
Climatic patterns are expected to become more extreme, with changes in precipitation characterized by heavier rainfall and prolonged dry periods. Yet, most studies focus on persistent moderate changes in precipitation, limiting our understanding of how ecosystems will function in the future. We examined the effects of extreme changes in precipitation on leaf-level and ecosystem CO2 and H2O exchange of three native C4 bunchgrasses (Andropogon gerardii, Panicum virgatum, and Sorghastrum nutans) over 3 years. Grasses were grown in three precipitation treatments: extreme dry, mean, and extreme wet based on historical rainfall records. After 3 years, plants were 45% smaller in the extreme dry treatment relative to the mean and extreme high treatment, which did not differ. We also found that an extreme decrease in precipitation caused reductions of 55, 40, and 40% in leaf-level photosynthesis (Anet), stomatal conductance (gs), and water use efficiency (WUE), respectively. Extreme increases in precipitation inhibited leaf-level WUE, with a 44% reduction relative to the mean treatment. At the ecosystem level, both an extreme increase and decrease in precipitation reduced net CO2 and water fluxes relative to plants grown with mean levels of precipitation. Net water fluxes (ET) were reduced by an average of 74% in the extreme dry and extreme wet treatment relative to mean treatment; net carbon fluxes followed a similar trend, with average reductions of 68% (NEE) and 100% (Re). Unlike moderate climate change, extreme increases in precipitation may be just as detrimental as extreme decreases in precipitation in shifting grassland physiology.
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Affiliation(s)
- Elise W Connor
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Christine V Hawkes
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, 78712, USA.
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Zhang Y, Loreau M, He N, Wang J, Pan Q, Bai Y, Han X. Climate variability decreases species richness and community stability in a temperate grassland. Oecologia 2018; 188:183-192. [PMID: 29943096 DOI: 10.1007/s00442-018-4208-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 06/18/2018] [Indexed: 12/15/2022]
Abstract
Climate change involves modifications in both the mean and the variability of temperature and precipitation. According to global warming projections, both the magnitude and the frequency of extreme weather events are increasing, thereby increasing climate variability. The previous studies have reported that climate warming tends to decrease biodiversity and the temporal stability of community primary productivity (i.e., community stability), but the effects of the variability of temperature and precipitation on biodiversity, community stability, and their relationship have not been clearly explored. We used a long-term (from 1982 to 2014) field data set from a temperate grassland in northern China to explore the effects of the variability of mean temperature and total precipitation on species richness, community stability, and their relationship. Results showed that species richness promoted community stability through increases in asynchronous dynamics across species (i.e., species asynchrony). Both species richness and species asynchrony were positively associated with the residuals of community stability after controlling for its dependence on the variability of mean temperature and total precipitation. Furthermore, the variability of mean temperature reduced species richness, while the variability of total precipitation decreased species asynchrony and community stability. Overall, the present study revealed that species richness and species asynchrony promoted community stability, but increased climate variability may erode these positive effects and thereby threaten community stability.
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Affiliation(s)
- Yunhai Zhang
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China.,School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Michel Loreau
- Centre for Biodiversity Theory and Modelling, Theoretical and Experimental Ecology Station, CNRS and Paul Sabatier University, 09200, Moulis, France
| | - Nianpeng He
- Synthesis Research Center of Chinese Ecosystem Research Network, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 100101, Beijing, China
| | - Junbang Wang
- Synthesis Research Center of Chinese Ecosystem Research Network, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 100101, Beijing, China
| | - Qingmin Pan
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China
| | - Yongfei Bai
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China.
| | - Xingguo Han
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China.
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59
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Stampfli A, Bloor JMG, Fischer M, Zeiter M. High land-use intensity exacerbates shifts in grassland vegetation composition after severe experimental drought. GLOBAL CHANGE BIOLOGY 2018; 24:2021-2034. [PMID: 29323767 DOI: 10.1111/gcb.14046] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 12/15/2017] [Accepted: 12/21/2017] [Indexed: 05/04/2023]
Abstract
Climate change projections anticipate increased frequency and intensity of drought stress, but grassland responses to severe droughts and their potential to recover are poorly understood. In many grasslands, high land-use intensity has enhanced productivity and promoted resource-acquisitive species at the expense of resource-conservative ones. Such changes in plant functional composition could affect the resistance to drought and the recovery after drought of grassland ecosystems with consequences for feed productivity resilience and environmental stewardship. In a 12-site precipitation exclusion experiment in upland grassland ecosystems across Switzerland, we imposed severe edaphic drought in plots under rainout shelters and compared them with plots under ambient conditions. We used soil water potentials to scale drought stress across sites. Impacts of precipitation exclusion and drought legacy effects were examined along a gradient of land-use intensity to determine how grasslands resisted to, and recovered after drought. In the year of precipitation exclusion, aboveground net primary productivity (ANPP) in plots under rainout shelters was -15% to -56% lower than in control plots. Drought effects on ANPP increased with drought severity, specified as duration of topsoil water potential ψ < -100 kPa, irrespective of land-use intensity. In the year after drought, ANPP had completely recovered, but total species diversity had declined by -10%. Perennial species showed elevated mortality, but species richness of annuals showed a small increase due to enhanced recruitment. In general, the more resource-acquisitive grasses increased at the expense of the deeper-rooted forbs after drought, suggesting that community reorganization was driven by competition rather than plant mortality. The negative effects of precipitation exclusion on forbs increased with land-use intensity. Our study suggests a synergistic impact of land-use intensification and climate change on grassland vegetation composition, and implies that biomass recovery after drought may occur at the expense of biodiversity maintenance.
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Affiliation(s)
- Andreas Stampfli
- School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Zollikofen, Switzerland
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
- Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland
| | | | - Markus Fischer
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
- Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland
| | - Michaela Zeiter
- School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Zollikofen, Switzerland
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
- Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland
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60
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Suseela V, Tharayil N. Decoupling the direct and indirect effects of climate on plant litter decomposition: Accounting for stress-induced modifications in plant chemistry. GLOBAL CHANGE BIOLOGY 2018; 24:1428-1451. [PMID: 28986956 DOI: 10.1111/gcb.13923] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 07/16/2017] [Indexed: 06/07/2023]
Abstract
Decomposition of plant litter is a fundamental ecosystem process that can act as a feedback to climate change by simultaneously influencing both the productivity of ecosystems and the flux of carbon dioxide from the soil. The influence of climate on decomposition from a postsenescence perspective is relatively well known; in particular, climate is known to regulate the rate of litter decomposition via its direct influence on the reaction kinetics and microbial physiology on processes downstream of tissue senescence. Climate can alter plant metabolism during the formative stage of tissues and could shape the final chemical composition of plant litter that is available for decomposition, and thus indirectly influence decomposition; however, these indirect effects are relatively poorly understood. Climatic stress disrupts cellular homeostasis in plants and results in the reprogramming of primary and secondary metabolic pathways, which leads to changes in the quantity, composition, and organization of small molecules and recalcitrant heteropolymers, including lignins, tannins, suberins, and cuticle within the plant tissue matrix. Furthermore, by regulating metabolism during tissue senescence, climate influences the resorption of nutrients from senescing tissues. Thus, the final chemical composition of plant litter that forms the substrate of decomposition is a combined product of presenescence physiological processes through the production and resorption of metabolites. The changes in quantity, composition, and localization of the molecular construct of the litter could enhance or hinder tissue decomposition and soil nutrient cycling by altering the recalcitrance of the lignocellulose matrix, the composition of microbial communities, and the activity of microbial exo-enzymes via various complexation reactions. Also, the climate-induced changes in the molecular composition of litter could differentially influence litter decomposition and soil nutrient cycling. Compared with temperate ecosystems, the indirect effects of climate on litter decomposition in the tropics are not well understood, which underscores the need to conduct additional studies in tropical biomes. We also emphasize the need to focus on how climatic stress affects the root chemistry as roots contribute significantly to biogeochemical cycling, and on utilizing more robust analytical approaches to capture the molecular composition of tissue matrix that fuel microbial metabolism.
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Affiliation(s)
- Vidya Suseela
- Department of Plant & Environmental Sciences, Clemson University, Clemson, SC, USA
| | - Nishanth Tharayil
- Department of Plant & Environmental Sciences, Clemson University, Clemson, SC, USA
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61
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Tredennick AT, Kleinhesselink AR, Taylor JB, Adler PB. Ecosystem functional response across precipitation extremes in a sagebrush steppe. PeerJ 2018; 6:e4485. [PMID: 29576958 PMCID: PMC5855887 DOI: 10.7717/peerj.4485] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 02/19/2018] [Indexed: 11/26/2022] Open
Abstract
Background Precipitation is predicted to become more variable in the western United States, meaning years of above and below average precipitation will become more common. Periods of extreme precipitation are major drivers of interannual variability in ecosystem functioning in water limited communities, but how ecosystems respond to these extremes over the long-term may shift with precipitation means and variances. Long-term changes in ecosystem functional response could reflect compensatory changes in species composition or species reaching physiological thresholds at extreme precipitation levels. Methods We conducted a five year precipitation manipulation experiment in a sagebrush steppe ecosystem in Idaho, United States. We used drought and irrigation treatments (approximately 50% decrease/increase) to investigate whether ecosystem functional response remains consistent under sustained high or low precipitation. We recorded data on aboveground net primary productivity (ANPP), species abundance, and soil moisture. We fit a generalized linear mixed effects model to determine if the relationship between ANPP and soil moisture differed among treatments. We used nonmetric multidimensional scaling to quantify community composition over the five years. Results Ecosystem functional response, defined as the relationship between soil moisture and ANPP, was similar among irrigation and control treatments, but the drought treatment had a greater slope than the control treatment. However, all estimates for the effect of soil moisture on ANPP overlapped zero, indicating the relationship is weak and uncertain regardless of treatment. There was also large spatial variation in ANPP within-years, which contributes to the uncertainty of the soil moisture effect. Plant community composition was remarkably stable over the course of the experiment and did not differ among treatments. Discussion Despite some evidence that ecosystem functional response became more sensitive under sustained drought conditions, the response of ANPP to soil moisture was consistently weak and community composition was stable. The similarity of ecosystem functional responses across treatments was not related to compensatory shifts at the plant community level, but instead may reflect the insensitivity of the dominant species to soil moisture. These species may be successful precisely because they have evolved life history strategies that buffer them against precipitation variability.
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Affiliation(s)
- Andrew T Tredennick
- Department of Wildland Resources and the Ecology Center, Utah State University, Logan, UT, United States of America
| | - Andrew R Kleinhesselink
- Department of Wildland Resources and the Ecology Center, Utah State University, Logan, UT, United States of America.,Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, United States of America
| | - J Bret Taylor
- United States Department of Agriculture, Agricultural Research Service, U.S. Sheep Experiment Station, Dubois, ID, United States of America
| | - Peter B Adler
- Department of Wildland Resources and the Ecology Center, Utah State University, Logan, UT, United States of America
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Henry HAL, Abedi M, Alados CL, Beard KH, Fraser LH, Jentsch A, Kreyling J, Kulmatiski A, Lamb EG, Sun W, Vankoughnett MR, Venn S, Werner C, Beil I, Blindow I, Dahlke S, Dubbert M, Effinger A, Garris HW, Gartzia M, Gebauer T, Arfin Khan MAS, Malyshev AV, Morgan J, Nock C, Paulson JP, Pueyo Y, Stover HJ, Yang X. Increased Soil Frost Versus Summer Drought as Drivers of Plant Biomass Responses to Reduced Precipitation: Results from a Globally Coordinated Field Experiment. Ecosystems 2018. [DOI: 10.1007/s10021-018-0231-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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63
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Hoover DL, Wilcox KR, Young KE. Experimental droughts with rainout shelters: a methodological review. Ecosphere 2018. [DOI: 10.1002/ecs2.2088] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- David L. Hoover
- Rangeland Resources & Systems Research Unit U.S. Department of Agriculture, Agricultural Research Service 1701 Centre Avenue Fort Collins Colorado 80526 USA
| | - Kevin R. Wilcox
- Rangeland Resources & Systems Research Unit U.S. Department of Agriculture, Agricultural Research Service 1701 Centre Avenue Fort Collins Colorado 80526 USA
| | - Kristina E. Young
- Department of Biological Sciences University of Texas El Paso 500 West University El Paso Texas 79968 USA
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Mokria M, Gebrekirstos A, Abiyu A, Van Noordwijk M, Bräuning A. Multi-century tree-ring precipitation record reveals increasing frequency of extreme dry events in the upper Blue Nile River catchment. GLOBAL CHANGE BIOLOGY 2017; 23:5436-5454. [PMID: 28712116 DOI: 10.1111/gcb.13809] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 06/23/2017] [Indexed: 06/07/2023]
Abstract
Climate-related environmental and humanitarian crisis are important challenges in the Great Horn of Africa (GHA). In the absence of long-term past climate records in the region, tree-rings are valuable climate proxies, reflecting past climate variations and complementing climate records prior to the instrumental era. We established annually resolved multi-century tree-ring chronology from Juniperus procera trees in northern Ethiopia, the longest series yet for the GHA. The chronology correlates significantly with wet-season (r = .64, p < .01) and annual (r = .68, p < .01) regional rainfall. Reconstructed rainfall since A.D. 1811 revealed significant interannual variations between 2.2 and 3.8 year periodicity, with significant decadal and multidecadal variations during 1855-1900 and 1960-1990. The duration of negative and positive rainfall anomalies varied between 1-7 years and 1-8 years. Approximately 78.4% (95%) of reconstructed dry (extreme dry) and 85.4% (95%) of wet (extreme wet) events lasted for 1 year only and corresponded to historical records of famine and flooding, suggesting that future climate change studies should be both trend and extreme event focused. The average return periods for dry (extreme dry) and wet (extreme wet) events were 4.1 (8.8) years and 4.1 (9.5) years. Extreme-dry conditions during the 19th century were concurrent with drought episodes in equatorial eastern Africa that occurred at the end of the Little Ice Age. El Niño and La Niña events matched with 38.5% and 50% of extreme-dry and extreme-wet events. Equivalent matches for positive and negative Indian Ocean Dipole events were weaker, reaching 23.1 and 25%, respectively. Spatial correlations revealed that reconstructed rainfall represents wet-season rainfall variations over northern Ethiopia and large parts of the Sahel belt. The data presented are useful for backcasting climate and hydrological models and for developing regional strategic plans to manage scarce and contested water resources. Historical perspectives on long-term regional rainfall variability improve the interpretation of recent climate trends.
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Affiliation(s)
- Mulugeta Mokria
- World Agroforestry Centre (ICRAF), United Nations Avenue, Nairobi, Kenya
- Institute of Geography, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Aster Gebrekirstos
- World Agroforestry Centre (ICRAF), United Nations Avenue, Nairobi, Kenya
| | - Abrham Abiyu
- Amhara Agricultural Research Institute (ARARI), Amhara Region, Ethiopia
| | - Meine Van Noordwijk
- World Agroforestry Centre (ICRAF), United Nations Avenue, Nairobi, Kenya
- Plant Production Systems, Wageningen University, Wageningen, the Netherlands
| | - Achim Bräuning
- Institute of Geography, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
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65
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Kreyling J, Dengler J, Walter J, Velev N, Ugurlu E, Sopotlieva D, Ransijn J, Picon-Cochard C, Nijs I, Hernandez P, Güler B, von Gillhaussen P, De Boeck HJ, Bloor JM, Berwaers S, Beierkuhnlein C, Arfin Khan MA, Apostolova I, Altan Y, Zeiter M, Wellstein C, Sternberg M, Stampfli A, Campetella G, Bartha S, Bahn M, Jentsch A. Species richness effects on grassland recovery from drought depend on community productivity in a multisite experiment. Ecol Lett 2017; 20:1405-1413. [DOI: 10.1111/ele.12848] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 08/06/2017] [Accepted: 08/14/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Juergen Kreyling
- Experimental Plant Ecology; Ernst-Moritz-Arndt University Greifswald; D-17487 Greifswald Germany
| | - Jürgen Dengler
- Plant Ecology; BayCEER; University of Bayreuth; 95440 Bayreuth Germany
- German Centre for Integrative Biodiversity Research (iDiv); 04103 Leipzig Germany
| | - Julia Walter
- Landscape Ecology; University of Hohenheim; 70599 Stuttgart Germany
| | - Nikolay Velev
- Institute of Biodiversity and Ecosystem Research; Bulgarian Academy of Sciences; 1113 Sofia Bulgaria
| | - Emin Ugurlu
- Forest Engineering; Faculty of Forestry; Bursa Technical University; 152 Evler Str., No:2/10 16330 Yildirim Bursa Turkey
| | - Desislava Sopotlieva
- Institute of Biodiversity and Ecosystem Research; Bulgarian Academy of Sciences; 1113 Sofia Bulgaria
| | - Johannes Ransijn
- Disturbance Ecology; BayCEER; University of Bayreuth; 95440 Bayreuth Germany
| | | | - Ivan Nijs
- Plants and Ecosystems; Department of Biology; University of Antwerp; 2610 Wilrijk Belgium
| | - Pauline Hernandez
- Grassland Ecosystem Research; UMR0874 INRA; VetAgroSup; 63000 Clermont-Ferrand France
| | - Behlül Güler
- Department of Biology; Faculty of Science & Letters; Manisa Celal Bayar University; Prof. Dr. Şehit İlhan Varank Campus 45040 Yunusemre Manisa Turkey
| | | | - Hans J. De Boeck
- Plants and Ecosystems; Department of Biology; University of Antwerp; 2610 Wilrijk Belgium
| | - Juliette M.G. Bloor
- Grassland Ecosystem Research; UMR0874 INRA; VetAgroSup; 63000 Clermont-Ferrand France
| | - Sigi Berwaers
- Plants and Ecosystems; Department of Biology; University of Antwerp; 2610 Wilrijk Belgium
| | | | - Mohammed A.S. Arfin Khan
- Disturbance Ecology; BayCEER; University of Bayreuth; 95440 Bayreuth Germany
- Department of Forestry and Environmental Science; Shahjalal University of Science and Technology; Sylhet 3114 Bangladesh
| | - Iva Apostolova
- Institute of Biodiversity and Ecosystem Research; Bulgarian Academy of Sciences; 1113 Sofia Bulgaria
| | - Yasin Altan
- Department of Biology; Faculty of Science & Letters; Manisa Celal Bayar University; Prof. Dr. Şehit İlhan Varank Campus 45040 Yunusemre Manisa Turkey
| | - Michaela Zeiter
- School of Agricultural, Forest and Food Sciences; Bern University of Applied Sciences; CH-3052 Zollikofen Switzerland
- Institute of Plant Sciences; University of Bern; CH-3013 Bern Switzerland
| | - Camilla Wellstein
- Faculty of Science and Technology; Free University of Bozen; I-39100 Bozen Italy
| | - Marcelo Sternberg
- School of Plant Sciences and Food Security; Faculty of Life Sciences; Tel Aviv University; Tel Aviv 69978 Israel
| | - Andreas Stampfli
- School of Agricultural, Forest and Food Sciences; Bern University of Applied Sciences; CH-3052 Zollikofen Switzerland
| | - Giandiego Campetella
- School of Biosciences and Veterinary Medicine; Plant Diversity and Ecosystems Management unit; University of Camerino; Camerino Italy
| | - Sándor Bartha
- Institute of Ecology and Botany; MTA Centre for Ecological Research; H-2163 Vácrátót Hungary
- School of Plant Biology; The University of Western Australia; 35 Stirling Highway Crawley WE 6009 Australia
| | - Michael Bahn
- Institute of Ecology; University of Innsbruck; A-6020 Innsbruck Austria
| | - Anke Jentsch
- Disturbance Ecology; BayCEER; University of Bayreuth; 95440 Bayreuth Germany
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Alba C, NeSmith JE, Fahey C, Angelini C, Flory SL. Methods to test the interactive effects of drought and plant invasion on ecosystem structure and function using complementary common garden and field experiments. Ecol Evol 2017; 7:1442-1452. [PMID: 28261456 PMCID: PMC5330907 DOI: 10.1002/ece3.2729] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 12/07/2016] [Accepted: 12/18/2016] [Indexed: 11/10/2022] Open
Abstract
Abiotic global change drivers affect ecosystem structure and function, but how they interact with biotic factors such as invasive plants is understudied. Such interactions may be additive, synergistic, or offsetting, and difficult to predict. We present methods to test the individual and interactive effects of drought and plant invasion on native ecosystems. We coupled a factorial common garden experiment containing resident communities exposed to drought (imposed with rainout shelters) and invasion with a field experiment where the invader was removed from sites spanning a natural soil moisture gradient. We detail treatments and their effects on abiotic conditions, including soil moisture, light, temperature, and humidity, which shape community and ecosystem responses. Ambient precipitation during the garden experiment exceeded historic norms despite severe drought in prior years. Soil moisture was 48% lower in drought than ambient plots, but the invader largely offset drought effects. Additionally, temperature and light were lower and humidity higher in invaded plots. Field sites spanned up to a 10‐fold range in soil moisture and up to a 2.5‐fold range in light availability. Invaded and resident vegetation did not differentially mediate soil moisture, unlike in the garden experiment. Herbicide effectively removed invaded and resident vegetation, with removal having site‐specific effects on soil moisture and light availability. However, light was generally higher in invader‐removal than control plots, whereas resident removal had less effect on light, similar to the garden experiment. Invasion mitigated a constellation of abiotic conditions associated with drought stress in the garden experiment. In the field, where other factors co‐varied, these patterns did not emerge. Still, neither experiment suggested that drought and invasion will have synergistic negative effects on ecosystems, although invasion can limit light availability. Coupling factorial garden experiments with field experiments across environmental gradients will be effective for predicting how multiple stressors interact in natural systems.
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Affiliation(s)
- Christina Alba
- Agronomy Department University of Florida Gainesville FL USA
| | - Julienne E NeSmith
- School of Natural Resources and Environment University of Florida Gainesville FL USA
| | - Catherine Fahey
- School of Natural Resources and Environment University of Florida Gainesville FL USA
| | - Christine Angelini
- Department of Environmental Engineering Sciences Engineering School for Sustainable Infrastructure and Environment University of Florida Gainesville FL USA
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Densmore-McCulloch JA, Thompson DL, Fraser LH. Short-Term Effects of Changing Precipitation Patterns on Shrub-Steppe Grasslands: Seasonal Watering Is More Important than Frequency of Watering Events. PLoS One 2016; 11:e0168663. [PMID: 27997611 PMCID: PMC5173370 DOI: 10.1371/journal.pone.0168663] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 12/05/2016] [Indexed: 12/02/2022] Open
Abstract
Climate change is expected to alter precipitation patterns. Droughts may become longer and more frequent, and the timing and intensity of precipitation may change. We tested how shifting precipitation patterns, both seasonally and by frequency of events, affects soil nitrogen availability, plant biomass and diversity in a shrub-steppe temperate grassland along a natural productivity gradient in Lac du Bois Grasslands Protected Area near Kamloops, British Columbia, Canada. We manipulated seasonal watering patterns by either exclusively watering in the spring or the fall. To simulate spring precipitation we restricted precipitation inputs in the fall, then added 50% more water than the long term average in the spring, and vice-versa for the fall precipitation treatment. Overall, the amount of precipitation remained roughly the same. We manipulated the frequency of rainfall events by either applying water weekly (frequent) or monthly (intensive). After 2 years, changes in the seasonality of watering had greater effects on plant biomass and diversity than changes in the frequency of watering. Fall watering reduced biomass and increased species diversity, while spring watering had little effect. The reduction in biomass in fall watered treatments was due to a decline in grasses, but not forbs. Plant available N, measured by Plant Root Simulator (PRS)-probes, increased from spring to summer to fall, and was higher in fall watered treatments compared to spring watered treatments when measured in the fall. The only effect observed due to frequency of watering events was greater extractable soil N in monthly applied treatments compared to weekly watering treatments. Understanding the effects of changing precipitation patterns on grasslands will allow improved grassland conservation and management in the face of global climatic change, and here we show that if precipitation is more abundant in the fall, compared to the spring, grassland primary productivity will likely be negatively affected.
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Affiliation(s)
| | | | - Lauchlan H. Fraser
- Department of Natural Resource Sciences, Thompson Rivers University, Kamloops, British Columbia, Canada
- * E-mail:
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