251
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A Decade of Streamwater Nitrogen and Forest Dynamics after a Mountain Pine Beetle Outbreak at the Fraser Experimental Forest, Colorado. Ecosystems 2016. [DOI: 10.1007/s10021-016-0027-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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252
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Canham CD, Murphy L. The demography of tree species response to climate: seedling recruitment and survival. Ecosphere 2016. [DOI: 10.1002/ecs2.1424] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Charles D. Canham
- Cary Institute of Ecosystem Studies Box AB Millbrook New York 12545 USA
| | - Lora Murphy
- Cary Institute of Ecosystem Studies Box AB Millbrook New York 12545 USA
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253
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A dynamical model for bark beetle outbreaks. J Theor Biol 2016; 407:25-37. [PMID: 27396358 DOI: 10.1016/j.jtbi.2016.07.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 06/13/2016] [Accepted: 07/06/2016] [Indexed: 11/22/2022]
Abstract
Tree-killing bark beetles are major disturbance agents affecting coniferous forest ecosystems. The role of environmental conditions on driving beetle outbreaks is becoming increasingly important as global climatic change alters environmental factors, such as drought stress, that, in turn, govern tree resistance. Furthermore, dynamics between beetles and trees are highly nonlinear, due to complex aggregation behaviors exhibited by beetles attacking trees. Models have a role to play in helping unravel the effects of variable tree resistance and beetle aggregation on bark beetle outbreaks. In this article we develop a new mathematical model for bark beetle outbreaks using an analogy with epidemiological models. Because the model operates on several distinct time scales, singular perturbation methods are used to simplify the model. The result is a dynamical system that tracks populations of uninfested and infested trees. A limiting case of the model is a discontinuous function of state variables, leading to solutions in the Filippov sense. The model assumes an extensive seed-bank so that tree recruitment is possible even if trees go extinct. Two scenarios are considered for immigration of new beetles. The first is a single tree stand with beetles immigrating from outside while the second considers two forest stands with beetle dispersal between them. For the seed-bank driven recruitment rate, when beetle immigration is low, the forest stand recovers to a beetle-free state. At high beetle immigration rates beetle populations approach an endemic equilibrium state. At intermediate immigration rates, the model predicts bistability as the forest can be in either of the two equilibrium states: a healthy forest, or a forest with an endemic beetle population. The model bistability leads to hysteresis. Interactions between two stands show how a less resistant stand of trees may provide an initial toe-hold for the invasion, which later leads to a regional beetle outbreak in the resistant stand.
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254
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Steppe K, von der Crone JS, De Pauw DJW. TreeWatch.net: A Water and Carbon Monitoring and Modeling Network to Assess Instant Tree Hydraulics and Carbon Status. FRONTIERS IN PLANT SCIENCE 2016; 7:993. [PMID: 27458474 PMCID: PMC4932327 DOI: 10.3389/fpls.2016.00993] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 06/22/2016] [Indexed: 05/22/2023]
Abstract
TreeWatch.net is an initiative that has been developed to watch trees grow and function in real-time. It is a water- and carbon-monitoring and modeling network, in which high-quality measurements of sap flow and stem diameter variation are collected on individual trees. Automated data processing using a cloud service enables instant visualization of water movement and radial stem growth. This can be used to demonstrate the sensitivity of trees to changing weather conditions, such as drought, heat waves, or heavy rain showers. But TreeWatch.net's true innovation lies in its use of these high-precision harmonized data to also parameterize process-based tree models in real-time, which makes displaying the much-needed mechanisms underlying tree responses to climate change possible. Continuous simulation of turgor to describe growth processes and long-term time series of hydraulic resistance to assess drought-vulnerability in real-time are only a few of the opportunities our approach offers. TreeWatch.net has been developed with the view to be complementary to existing forest monitoring networks and with the aim to contribute to existing dynamic global vegetation models. It provides high-quality data and real-time simulations in order to advance research on the impact of climate change on the biological response of trees and forests. Besides its application in natural forests to answer climate-change related scientific and political questions, we also envision a broader societal application of TreeWatch.net by selecting trees in nature reserves, public areas, cities, university areas, schoolyards, and parks to teach youngsters and create public awareness on the effects of changing weather conditions on trees and forests in this era of climate change.
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Affiliation(s)
- Kathy Steppe
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent UniversityGhent, Belgium
| | - Jonas S. von der Crone
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent UniversityGhent, Belgium
| | - Dirk J. W. De Pauw
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent UniversityGhent, Belgium
- Phyto-ITGhent, Belgium
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255
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Eller CB, Lima AL, Oliveira RS. Cloud forest trees with higher foliar water uptake capacity and anisohydric behavior are more vulnerable to drought and climate change. THE NEW PHYTOLOGIST 2016; 211:489-501. [PMID: 27038126 DOI: 10.1111/nph.13952] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 02/25/2016] [Indexed: 05/24/2023]
Abstract
Many tropical montane cloud forest (TMCF) trees are capable of foliar water uptake (FWU) during leaf-wetting events. In this study, we tested the hypothesis that maintenance of leaf turgor during periods of fog exposure and soil drought is related to species' FWU capacity. We conducted several experiments using apoplastic tracers, deuterium labeling and leaf immersion in water to evaluate differences in FWU among three common TMCF tree species. We also measured the effect of regular fog exposure on the leaf water potential of plants subjected to soil drought and used these data to model species' response to long-term drought. All species were able to absorb water through their leaf cuticles and/or trichomes, although the capacity to do so differed between species. During the drought experiment, the species with higher FWU capacity maintained leaf turgor for a longer period when exposed to fog, whereas the species with lower FWU exerted tighter stomatal regulation to maintain leaf turgor. Model results suggest that without fog, species with high FWU are more likely to lose turgor during seasonal droughts. We show that leaf-wetting events are essential for trees with high FWU, which tend to be more anisohydric, maintaining leaf turgor during seasonal droughts.
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Affiliation(s)
- Cleiton B Eller
- Department of Plant Biology, Institute of Biology, CP6109, University of Campinas - UNICAMP, Campinas, SP, 13083-970, Brazil
| | - Aline L Lima
- Center of Studies and Environmental Research - NEPAM, University of Campinas - UNICAMP, Campinas, SP, 13083-862, Brazil
| | - Rafael S Oliveira
- Department of Plant Biology, Institute of Biology, CP6109, University of Campinas - UNICAMP, Campinas, SP, 13083-970, Brazil
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256
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Corlett RT. The Impacts of Droughts in Tropical Forests. TRENDS IN PLANT SCIENCE 2016; 21:584-593. [PMID: 26994658 DOI: 10.1016/j.tplants.2016.02.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Revised: 02/16/2016] [Accepted: 02/20/2016] [Indexed: 05/19/2023]
Abstract
Tropical forests exchange more carbon dioxide (CO2) with the atmosphere than any other vegetation type and, thus, form a crucial component of the global carbon cycle. However, the impacts of anthropogenic climate change on drought occurrence and intensity could weaken the tropical forest carbon sink, with resulting feedback to future climates. We urgently need a better understanding of the mechanisms and processes involved to predict future responses of tropical forest carbon sequestration to climate change. Recent progress has been made in the study of drought responses at the molecular, cellular, organ, individual, species, community, and landscape levels. Although understanding of the mechanisms is incomplete, the models used to predict drought impacts could be significantly improved by incorporating existing knowledge.
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Affiliation(s)
- Richard T Corlett
- Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China.
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257
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Meta-analysis reveals that hydraulic traits explain cross-species patterns of drought-induced tree mortality across the globe. Proc Natl Acad Sci U S A 2016; 113:5024-9. [PMID: 27091965 DOI: 10.1073/pnas.1525678113] [Citation(s) in RCA: 331] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Drought-induced tree mortality has been observed globally and is expected to increase under climate change scenarios, with large potential consequences for the terrestrial carbon sink. Predicting mortality across species is crucial for assessing the effects of climate extremes on forest community biodiversity, composition, and carbon sequestration. However, the physiological traits associated with elevated risk of mortality in diverse ecosystems remain unknown, although these traits could greatly improve understanding and prediction of tree mortality in forests. We performed a meta-analysis on species' mortality rates across 475 species from 33 studies around the globe to assess which traits determine a species' mortality risk. We found that species-specific mortality anomalies from community mortality rate in a given drought were associated with plant hydraulic traits. Across all species, mortality was best predicted by a low hydraulic safety margin-the difference between typical minimum xylem water potential and that causing xylem dysfunction-and xylem vulnerability to embolism. Angiosperms and gymnosperms experienced roughly equal mortality risks. Our results provide broad support for the hypothesis that hydraulic traits capture key mechanisms determining tree death and highlight that physiological traits can improve vegetation model prediction of tree mortality during climate extremes.
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258
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He W, Wu F, Yang W, Zhang D, Xu Z, Tan B, Zhao Y, Justine MF. Gap locations influence the release of carbon, nitrogen and phosphorus in two shrub foliar litter in an alpine fir forest. Sci Rep 2016; 6:22014. [PMID: 26906762 PMCID: PMC4764935 DOI: 10.1038/srep22014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/05/2016] [Indexed: 11/23/2022] Open
Abstract
Gap formation favors the growth of understory plants and affects the decomposition process of plant debris inside and outside of gaps. Little information is available regarding how bioelement release from shrub litter is affected by gap formation during critical periods. The release of carbon (C), nitrogen (N), and phosphorus (P) in the foliar litter of Fargesia nitida and Salix paraplesia in response to gap locations was determined in an alpine forest of the eastern Qinghai-Tibet Plateau via a 2-year litter decomposition experiment. The daily release rates of C, N, and P increased from the closed canopy to the gap centers during the two winters, the two later growing seasons and the entire 2 years, whereas this trend was reversed during the two early growing seasons. The pairwise ratios among C, N, and P converged as the litter decomposition proceeded. Compared with the closed canopy, the gap centers displayed higher C:P and N:P ratio but a lower C:N ratio as the decomposition proceeded. Alpine forest gaps accelerate the release of C, N, and P in decomposing shrub litter, implying that reduced snow cover resulting from vanishing gaps may inhibit the release of these elements in alpine forests.
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Affiliation(s)
- Wei He
- Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology &Forestry, Sichuan Agricultural University, Chengdu 611130, China
| | - Fuzhong Wu
- Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology &Forestry, Sichuan Agricultural University, Chengdu 611130, China.,Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangtze River, Chengdu 611130, China
| | - Wanqin Yang
- Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology &Forestry, Sichuan Agricultural University, Chengdu 611130, China.,Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangtze River, Chengdu 611130, China
| | - Danju Zhang
- Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology &Forestry, Sichuan Agricultural University, Chengdu 611130, China.,Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangtze River, Chengdu 611130, China
| | - Zhenfeng Xu
- Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology &Forestry, Sichuan Agricultural University, Chengdu 611130, China.,Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangtze River, Chengdu 611130, China
| | - Bo Tan
- Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology &Forestry, Sichuan Agricultural University, Chengdu 611130, China.,Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangtze River, Chengdu 611130, China
| | - Yeyi Zhao
- Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology &Forestry, Sichuan Agricultural University, Chengdu 611130, China
| | - Meta Francis Justine
- Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology &Forestry, Sichuan Agricultural University, Chengdu 611130, China
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259
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Reed CC, Loik ME. Water relations and photosynthesis along an elevation gradient for Artemisia tridentata during an historic drought. Oecologia 2016; 181:65-76. [DOI: 10.1007/s00442-015-3528-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 12/01/2015] [Indexed: 10/22/2022]
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260
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Wiley E, Rogers BJ, Hodgkinson R, Landhäusser SM. Nonstructural carbohydrate dynamics of lodgepole pine dying from mountain pine beetle attack. THE NEW PHYTOLOGIST 2016; 209:550-562. [PMID: 26256444 DOI: 10.1111/nph.13603] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 07/13/2015] [Indexed: 06/04/2023]
Abstract
Bark beetle outbreaks are an important cause of tree death, but the process by which trees die remains poorly understood. The effect of beetle attack on whole-tree nonstructural carbohydrate (NSC) dynamics is particularly unclear, despite the potential role of carbohydrates in plant defense and survival. We monitored NSC dynamics of all organs in attacked and protected lodgepole pines (Pinus contorta) during a mountain pine beetle (Dendroctonus ponderosae) outbreak in British Columbia, starting before beetle flight in June 2011 through October 2012, when most attacked trees had died. Following attack, NSC concentrations were first reduced in the attacked region of the bole. The first NSC reduction in a distant organ appeared in the needles at the end of 2011, while branch and root NSC did not decline until much later in 2012. Attacked trees that were still alive in October 2012 had less beetle damage, which was negatively correlated with initial bark sugar concentrations in the attack region. The NSC dynamics of dying trees indicate that trees were killed by a loss of water conduction and not girdling. Further, our results identify locally reduced carbohydrate availability as an important mechanism by which stressors like drought may increase tree susceptibility to biotic attack.
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Affiliation(s)
- Erin Wiley
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, T6G 2E3, Canada
| | - Bruce J Rogers
- Omineca Research and Stewardship Team, British Columbia Ministry of Forests Lands and Natural Resource Operations, Prince George, BC, V2N 4W5, Canada
| | - Robert Hodgkinson
- Omineca Research and Stewardship Team, British Columbia Ministry of Forests Lands and Natural Resource Operations, Prince George, BC, V2N 4W5, Canada
| | - Simon M Landhäusser
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, T6G 2E3, Canada
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261
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Berdanier AB, Clark JS. Multiyear drought-induced morbidity preceding tree death in southeastern U.S. forests. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2016; 26:17-23. [PMID: 27039506 DOI: 10.1890/15-0274] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Recent forest diebacks, combined with threats of future drought, focus attention on the extent to which tree death is caused by catastrophic events as opposed to chronic declines in health that accumulate over years. While recent attention has focused on large-scale diebacks, there is concern that increasing drought stress and chronic morbidity may have pervasive impacts on forest composition in many regions. Here we use long-term, whole-stand inventory data from southeastern U.S. forests to show that trees exposed to drought experience multiyear declines in growth prior to mortality. Following a severe, multiyear drought, 72% of trees that did not recover their pre-drought growth rates died within 10 yr. This pattern was mediated by local moisture availability. As an index of morbidity prior to death, we calculated the difference in cumulative growth after drought relative to surviving conspecifics. The strength of drought-induced morbidity varied among species and was correlated with drought tolerance. These findings support the ability of trees to avoid death during drought events but indicate shifts that could occur over decades. Tree mortality following drought is predictable in these ecosystems based on growth declines, highlighting an opportunity to address multiyear drought-induced morbidity in models, experiments, and management decisions.
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262
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Millar CI, Stephenson NL. Temperate forest health in an era of emerging megadisturbance. Science 2015; 349:823-6. [DOI: 10.1126/science.aaa9933] [Citation(s) in RCA: 537] [Impact Index Per Article: 59.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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263
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Allen CD, Breshears DD, McDowell NG. On underestimation of global vulnerability to tree mortality and forest die-off from hotter drought in the Anthropocene. Ecosphere 2015. [DOI: 10.1890/es15-00203.1] [Citation(s) in RCA: 1345] [Impact Index Per Article: 149.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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