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Kristina J Andersonteixeira - One of the best experts on this subject based on the ideXlab platform.
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patterns of tree mortality in a temperate deciduous Forest derived from a large Forest Dynamics plot
Ecosphere, 2016Co-Authors: Erika Gonzalezakre, Victoria Meakem, Alan J. Tepley, Norman A. Bourg, William J. Mcshea, Stuart J. Davies, Kristina J AndersonteixeiraAbstract:Tree mortality is one of the most influential drivers of Forest Dynamics, and characterizing patterns of tree mortality is critical to understanding Forest Dynamics and ecosystem function in the present era of global change. Here, we use a unique data set of mortality in a temperate deciduous Forest to characterize rates and drivers of mortality. At the 25.6-ha Center for Tropical Forest Science—Forest Global Earth Observatory Forest Dynamics plot at the Smithsonian Conservation Biology Institute (Virginia, USA), we conducted two full tree censuses in 2008 and 2013 and then tracked mortality over the next 2 years (2014 and 2015). Overall, the mortality rate, m, of stems ≥10 cm diameter was 1.3–2.1%/yr. Biomass mortality, M, was 1.9–3.4 Mg·ha−1·yr−1 at the stand level (0.6–1.1%/yr of biomass), less than biomass gains from growth and recruitment, resulting in net live biomass accumulation. Small stems died at the highest rate; however, contributions to M increased toward larger size classes. Most species had m < 2%/yr and M < 0.25 Mg·ha−1·yr−1 (<3%/yr of biomass), whereas two to four species had anomalously high mortality rates during each census period, accounting for 15–24% of m (n = 2, Cercis canadensis, Ulmus species) and 39–75% of M (n = 4 Quercus species). Stems that died, whether or not in association with mechanical damage, tended to grow more slowly in preceding years than surviving stems and, for certain shade-intolerant species, tended to be in neighborhoods with higher basal area. These findings show how relatively fine-scale mortality processes contribute to stand-level compositional change and carbon cycling. The mortality patterns reported here will provide a valuable basis for understanding future disturbance events within eastern deciduous Forests and for comparing across Forest types.
Stuart J. Davies - One of the best experts on this subject based on the ideXlab platform.
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Patterns of tree mortality in a temperate deciduous Forest derived from a large Forest Dynamics plot
Ecosphere, 2016Co-Authors: Erika B. Gonzalez-akre, Victoria Meakem, Cheng-yin Eng, Alan J. Tepley, Norman A. Bourg, William J. Mcshea, Stuart J. Davies, Kristina J. Anderson-teixeiraAbstract:Tree mortality is one of the most influential drivers of Forest Dynamics, and characterizing patterns of tree mortality is critical to understanding Forest Dynamics and ecosystem function in the present era of global change. Here, we use a unique data set of mortality in a temperate deciduous Forest to characterize rates and drivers of mortality. At the 25.6-ha Center for Tropical Forest Science—Forest Global Earth Observatory Forest Dynamics plot at the Smithsonian Conservation Biology Institute (Virginia, USA), we conducted two full tree censuses in 2008 and 2013 and then tracked mortality over the next 2 years (2014 and 2015). Overall, the mortality rate, m, of stems ≥10 cm diameter was 1.3–2.1%/yr. Biomass mortality, M, was 1.9–3.4 Mg·ha−1·yr−1 at the stand level (0.6–1.1%/yr of biomass), less than biomass gains from growth and recruitment, resulting in net live biomass accumulation. Small stems died at the highest rate; however, contributions to M increased toward larger size classes. Most species had m
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patterns of tree mortality in a temperate deciduous Forest derived from a large Forest Dynamics plot
Ecosphere, 2016Co-Authors: Erika Gonzalezakre, Victoria Meakem, Alan J. Tepley, Norman A. Bourg, William J. Mcshea, Stuart J. Davies, Kristina J AndersonteixeiraAbstract:Tree mortality is one of the most influential drivers of Forest Dynamics, and characterizing patterns of tree mortality is critical to understanding Forest Dynamics and ecosystem function in the present era of global change. Here, we use a unique data set of mortality in a temperate deciduous Forest to characterize rates and drivers of mortality. At the 25.6-ha Center for Tropical Forest Science—Forest Global Earth Observatory Forest Dynamics plot at the Smithsonian Conservation Biology Institute (Virginia, USA), we conducted two full tree censuses in 2008 and 2013 and then tracked mortality over the next 2 years (2014 and 2015). Overall, the mortality rate, m, of stems ≥10 cm diameter was 1.3–2.1%/yr. Biomass mortality, M, was 1.9–3.4 Mg·ha−1·yr−1 at the stand level (0.6–1.1%/yr of biomass), less than biomass gains from growth and recruitment, resulting in net live biomass accumulation. Small stems died at the highest rate; however, contributions to M increased toward larger size classes. Most species had m < 2%/yr and M < 0.25 Mg·ha−1·yr−1 (<3%/yr of biomass), whereas two to four species had anomalously high mortality rates during each census period, accounting for 15–24% of m (n = 2, Cercis canadensis, Ulmus species) and 39–75% of M (n = 4 Quercus species). Stems that died, whether or not in association with mechanical damage, tended to grow more slowly in preceding years than surviving stems and, for certain shade-intolerant species, tended to be in neighborhoods with higher basal area. These findings show how relatively fine-scale mortality processes contribute to stand-level compositional change and carbon cycling. The mortality patterns reported here will provide a valuable basis for understanding future disturbance events within eastern deciduous Forests and for comparing across Forest types.
Harald Bugmann - One of the best experts on this subject based on the ideXlab platform.
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Projecting Forest Dynamics Across Europe: Potentials and Pitfalls of Empirical Mortality Algorithms
Ecosystems, 2019Co-Authors: Timothy Thrippleton, Lisa Hülsmann, Maxime Cailleret, Harald BugmannAbstract:Mortality is a key process of Forest ecosystem Dynamics and functioning strongly altering biomass stocks and carbon residence times. Dynamic vegetation models (DVMs) used to predict Forest Dynamics are typically based on simple, largely data-free (‘theoretical’) mortality algorithms (MAs). To improve DVM projections, the use of empirically based MAs has been suggested, but little is known about their impact on DVM behavior. A systematic comparison of eight MAs (seven inventory-based, one ‘theoretical’) for the pan-European tree species Pinus sylvestris L. was carried out within the DVM ForClim for present and future climate scenarios at three contrasting sites across Europe. Model accuracy was furthermore evaluated with empirical data from young- and old-growth Forests. We found strongly diverging mortality patterns among the MAs for present climate. Based on their behavior, we identified two distinct empirical MA groups that were related to their structure (i.e., variables considered), but not to their geographic origin (i.e., the environmental conditions they were calibrated to). Under climate change, MAs based on a competition index produced ecologically inconsistent results, while MAs based on growth showed more plausible and less extreme behaviors. Furthermore, MAs based on growth reached a higher accuracy for projecting young- and old-growth Forest Dynamics. Our results demonstrate that using empirical MAs in DVMs has a high potential to better predict Forest Dynamics, but also a risk of yielding implausible results if their structure is inadequate. For DVM applications across large spatiotemporal scales, we thus suggest using MAs based on growth, particularly under future no-analogue climates.
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Tree mortality submodels drive simulated long-term Forest Dynamics: assessing 15 models from the stand to global scale
Ecosphere, 2019Co-Authors: Harald Bugmann, Rupert Seidl, Maxime Cailleret, Florian Hartig, Friedrich Bohn, Josef Brůna, Louis François, Jens Heinke, Alexandra-jane Henrot, Thomas HicklerAbstract:Models are pivotal for assessing future Forest Dynamics under the impacts of changing climate and management practices, incorporating representations of tree growth, mortality, and regeneration. Quantitative studies on the importance of mortality submodels are scarce. We evaluated 15 dynamic vegetation models (DVMs) regarding their sensitivity to different formulations of tree mortality under different degrees of climate change. The set of models comprised eight DVMs at the stand scale, three at the landscape scale, and four typically applied at the continental to global scale. Some incorporate empirically derived mortality models, and others are based on experimental data, whereas still others are based on theoretical reasoning. Each DVM was run with at least two alternative mortality submodels. Model behavior was evaluated against empirical time series data, and then, the models were subjected to different scenarios of climate change. Most DVMs matched empirical data quite well, irrespective of the mortality submodel that was used. However, mortality submodels that performed in a very similar manner against past data often led to sharply different trajectories of Forest Dynamics under future climate change. Most DVMs featured high sensitivity to the mortality submodel, with deviations of basal area and stem numbers on the order of 10–40% per century under current climate and 20–170% under climate change. The sensitivity of a given DVM to scenarios of climate change, however, was typically lower by a factor of two to three. We conclude that (1) mortality is one of the most uncertain processes when it comes to assessing Forest response to climate change, and (2) more data and a better process understanding of tree mortality are needed to improve the robustness of simulated future Forest Dynamics. Our study highlights that comparing several alternative mortality formulations in DVMs provides valuable insights into the effects of process uncertainties on simulated future Forest Dynamics.
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The agony of choice: different empirical mortality models lead to sharply different future Forest Dynamics.
Ecological applications : a publication of the Ecological Society of America, 2015Co-Authors: Nicolas Bircher, Maxime Cailleret, Harald BugmannAbstract:Dynamic models are pivotal for projecting Forest Dynamics in a changing climate, from the local to the global scale. They encapsulate the processes of tree population Dynamics with varying resolution. Yet, almost invariably, tree mortality is modeled based on simple, theoretical assumptions that lack a physiological and/or empirical basis. Although this has been widely criticized and a growing number of empirically derived alternatives are available, they have not been tested systematically in models of Forest Dynamics. We implemented an inventory-based and a tree-ring-based mortality routine in the Forest gap model ForClim v3.0. We combined these routines with a stochastic and a deterministic approach for the determination of tree status (alive vs. dead). We tested the four new model versions for two Norway spruce Forests in the Swiss Alps, one of which was managed (inventory time series spanning 72 years) and the other was unmanaged (41 years). Furthermore, we ran long-term simulations (-400 years) into the future under three climate scenarios to test model behavior under changing environmental conditions. The tests against inventory data showed an excellent match of simulated basal area and stem numbers at the managed site and a fair agreement at the unmanaged site for three of the four empirical mortality models, thus rendering the choice of one particular model difficult. However, long-term simulations under current climate revealed very different behavior of the mortality models in terms of simulated changes of basal area and stem numbers, both in timing and magnitude, thus indicating high sensitivity of simulated Forest Dynamics to assumptions on tree mortality. Our results underpin the potential of using empirical mortality routines in Forest gap models. However, further tests are needed that span other climatic conditions and mixed Forests. Short-term simulations to benchmark model behavior against empirical data are insufficient; long-term tests are needed that include both nonequilibrium and equilibrium conditions. Thus, there is the potential to greatly improve the robustness of future projections of Forest Dynamics via more reliable tree mortality submodels.
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Gap models, Forest Dynamics and the response of vegetation to climate change
Past and Future Rapid Environmental Changes, 1997Co-Authors: Harald BugmannAbstract:Mathematical models of successional processes in Forests that are based on the concept of gap Dynamics (Watt 1947) are among the most prominent tools to test ecological hypotheses on long-term Forest Dynamics (Botkin et al. 1972; Shugart 1984). Moreover, these models have also gained an important role for studying a wide range of applied environmental problems such as growth enhancement through increasing atmospheric CO2 content (e.g. Shugart & Emanuel 1985), air pollution (e.g. Kercher & Axelrod 1984) and climatic change (e.g. Solomon 1986).
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Simulating Forest Dynamics in a complex topography using gridded climatic data
Climatic Change, 1996Co-Authors: Harald Bugmann, Andreas FischlinAbstract:The Forest model ForClim was used to evaluate the applicability of gap models in complex topography when the climatic input data is provided by a global database of 0.5° resolution. The analysis was based on 12 grid cells along an altitudinal gradient in the European Alps. Forest Dynamics were studied both under current climate as well as under four prescribed 2 × CO2 scenarios of climatic change obtained from General Circulation Models, which allowed to assess the sensitivity of mountainous Forests to climatic change.
Kristina J. Anderson-teixeira - One of the best experts on this subject based on the ideXlab platform.
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Pervasive Shifts in Forest Dynamics in a Changing World
Science (New York N.Y.), 2020Co-Authors: Nate G. Mcdowell, Kristina J. Anderson-teixeira, Craig D. Allen, Brian H. Aukema, Ben Bond-lamberty, Louise Chini, James S. Clark, Michael Dietze, Charlotte Grossiord, Adam Hanbury-brownAbstract:BACKGROUND Forest Dynamics arise from the interplay of chronic drivers and transient disturbances with the demographic processes of recruitment, growth, and mortality. The resulting trajectories of vegetation development drive the biomass and species composition of terrestrial ecosystems. Forest Dynamics are changing because of anthropogenic-driven exacerbation of chronic drivers, such as rising temperature and CO2, and increasing transient disturbances, including wildfire, drought, windthrow, biotic attack, and land-use change. There are widespread observations of increasing tree mortality due to changing climate and land use, as well as observations of growth stimulation of younger Forests due to CO2 fertilization. These antagonistic processes are co-occurring globally, leaving the fate of future Forests uncertain. We examine the implications of changing Forest demography and its drivers for both future Forest management and forecasting impacts of global climate forcing. ADVANCES We reviewed the literature of Forest demographic responses to chronic drivers and transient disturbances to generate hypotheses on future trajectories of these factors and their subsequent impacts on vegetation Dynamics, with a focus on Forested ecosystems. We complemented this review with analyses of global land-use change and disturbance datasets to independently evaluate the implications of changing drivers and disturbances on global-scale tree demographics. Ongoing changes in environmental drivers and disturbance regimes are consistently increasing mortality and forcing Forests toward shorter-statured and younger stands, reducing potential carbon storage. Acclimation, adaptation, and migration may partially mitigate these effects. These increased Forest impacts are due to natural disturbances (e.g., wildfire, drought, windthrow, insect or pathogen outbreaks) and land-use change, both of which are predicted to increase in magnitude in the future. Atmospherically derived estimates of the terrestrial carbon sink and remote sensing data indicate that tree growth and potentially recruitment may have increased globally in the 20th century, but the growth of this carbon sink has slowed. Variability in growth stimulation due to CO2 fertilization is evident globally, with observations and experiments suggesting that Forests benefit from CO2 primarily in early stages of secondary succession. Furthermore, increased tree growth typically requires sufficient water and nutrients to take advantage of rising CO2. Collectively, the evidence reveals that it is highly likely that tree mortality rates will continue to increase, whereas recruitment and growth will respond to changing drivers in a spatially and temporally variable manner. The net impact will be a reduction in Forest canopy cover and biomass. OUTLOOK Pervasive shifts in Forest vegetation Dynamics are already occurring and are likely to accelerate under future global changes, with consequences for biodiversity and climate forcing. This conclusion is robust with respect to the abundant literature evidence and our global assessment of historical demographic changes, but it also forms the basis for hypotheses regarding the patterns and processes underlying the shifts in Forest Dynamics. These hypotheses will be directly testable using emerging terrestrial and satellite-based observation networks. The existing evidence and newly made observations provide a critical test of Earth system models that continue to improve in their ability to simulate Forest Dynamics and resulting climate forcing. Ultimately, Forest managers and natural resource policies must confront the consequences of changing climate and disturbance regimes to ensure sustainable Forests and accrue their associated benefits.
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Patterns of tree mortality in a temperate deciduous Forest derived from a large Forest Dynamics plot
Ecosphere, 2016Co-Authors: Erika B. Gonzalez-akre, Victoria Meakem, Cheng-yin Eng, Alan J. Tepley, Norman A. Bourg, William J. Mcshea, Stuart J. Davies, Kristina J. Anderson-teixeiraAbstract:Tree mortality is one of the most influential drivers of Forest Dynamics, and characterizing patterns of tree mortality is critical to understanding Forest Dynamics and ecosystem function in the present era of global change. Here, we use a unique data set of mortality in a temperate deciduous Forest to characterize rates and drivers of mortality. At the 25.6-ha Center for Tropical Forest Science—Forest Global Earth Observatory Forest Dynamics plot at the Smithsonian Conservation Biology Institute (Virginia, USA), we conducted two full tree censuses in 2008 and 2013 and then tracked mortality over the next 2 years (2014 and 2015). Overall, the mortality rate, m, of stems ≥10 cm diameter was 1.3–2.1%/yr. Biomass mortality, M, was 1.9–3.4 Mg·ha−1·yr−1 at the stand level (0.6–1.1%/yr of biomass), less than biomass gains from growth and recruitment, resulting in net live biomass accumulation. Small stems died at the highest rate; however, contributions to M increased toward larger size classes. Most species had m
Victoria Meakem - One of the best experts on this subject based on the ideXlab platform.
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Patterns of tree mortality in a temperate deciduous Forest derived from a large Forest Dynamics plot
Ecosphere, 2016Co-Authors: Erika B. Gonzalez-akre, Victoria Meakem, Cheng-yin Eng, Alan J. Tepley, Norman A. Bourg, William J. Mcshea, Stuart J. Davies, Kristina J. Anderson-teixeiraAbstract:Tree mortality is one of the most influential drivers of Forest Dynamics, and characterizing patterns of tree mortality is critical to understanding Forest Dynamics and ecosystem function in the present era of global change. Here, we use a unique data set of mortality in a temperate deciduous Forest to characterize rates and drivers of mortality. At the 25.6-ha Center for Tropical Forest Science—Forest Global Earth Observatory Forest Dynamics plot at the Smithsonian Conservation Biology Institute (Virginia, USA), we conducted two full tree censuses in 2008 and 2013 and then tracked mortality over the next 2 years (2014 and 2015). Overall, the mortality rate, m, of stems ≥10 cm diameter was 1.3–2.1%/yr. Biomass mortality, M, was 1.9–3.4 Mg·ha−1·yr−1 at the stand level (0.6–1.1%/yr of biomass), less than biomass gains from growth and recruitment, resulting in net live biomass accumulation. Small stems died at the highest rate; however, contributions to M increased toward larger size classes. Most species had m
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patterns of tree mortality in a temperate deciduous Forest derived from a large Forest Dynamics plot
Ecosphere, 2016Co-Authors: Erika Gonzalezakre, Victoria Meakem, Alan J. Tepley, Norman A. Bourg, William J. Mcshea, Stuart J. Davies, Kristina J AndersonteixeiraAbstract:Tree mortality is one of the most influential drivers of Forest Dynamics, and characterizing patterns of tree mortality is critical to understanding Forest Dynamics and ecosystem function in the present era of global change. Here, we use a unique data set of mortality in a temperate deciduous Forest to characterize rates and drivers of mortality. At the 25.6-ha Center for Tropical Forest Science—Forest Global Earth Observatory Forest Dynamics plot at the Smithsonian Conservation Biology Institute (Virginia, USA), we conducted two full tree censuses in 2008 and 2013 and then tracked mortality over the next 2 years (2014 and 2015). Overall, the mortality rate, m, of stems ≥10 cm diameter was 1.3–2.1%/yr. Biomass mortality, M, was 1.9–3.4 Mg·ha−1·yr−1 at the stand level (0.6–1.1%/yr of biomass), less than biomass gains from growth and recruitment, resulting in net live biomass accumulation. Small stems died at the highest rate; however, contributions to M increased toward larger size classes. Most species had m < 2%/yr and M < 0.25 Mg·ha−1·yr−1 (<3%/yr of biomass), whereas two to four species had anomalously high mortality rates during each census period, accounting for 15–24% of m (n = 2, Cercis canadensis, Ulmus species) and 39–75% of M (n = 4 Quercus species). Stems that died, whether or not in association with mechanical damage, tended to grow more slowly in preceding years than surviving stems and, for certain shade-intolerant species, tended to be in neighborhoods with higher basal area. These findings show how relatively fine-scale mortality processes contribute to stand-level compositional change and carbon cycling. The mortality patterns reported here will provide a valuable basis for understanding future disturbance events within eastern deciduous Forests and for comparing across Forest types.