Exploring the impacts of unprecedented climate extremes on forest ecosystems: hypotheses to guide modeling and experimental studies
<p>Climatic extreme events are expected to occur more frequently in the future, increasing the likelihood of unprecedented climate extremes (UCEs) or record-breaking events. UCEs, such as extreme heatwaves and droughts, substantially affect ecosystem stability and carbon cycling by increasing...
| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-06-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/20/2117/2023/bg-20-2117-2023.pdf |
| Summary: | <p>Climatic extreme events are expected to occur more frequently in the future,
increasing the likelihood of unprecedented climate extremes (UCEs) or
record-breaking events. UCEs, such as extreme heatwaves and droughts,
substantially affect ecosystem stability and carbon cycling by increasing
plant mortality and delaying ecosystem recovery. Quantitative knowledge of
such effects is limited due to the paucity of experiments focusing on
extreme climatic events beyond the range of historical experience. Here, we
present a road map of how dynamic vegetation demographic models (VDMs) can
be used to investigate hypotheses surrounding ecosystem responses to one
type of UCE: unprecedented droughts. As a result of nonlinear ecosystem
responses to UCEs that are qualitatively different from responses to milder
extremes, we consider both biomass loss and recovery rates over time by
reporting a time-integrated carbon loss as a result of UCE, relative to the
absence of drought. Additionally, we explore how unprecedented droughts in
combination with increasing atmospheric CO<span class="inline-formula"><sub>2</sub></span> and/or temperature may
affect ecosystem stability and carbon cycling. We explored these questions
using simulations of pre-drought and post-drought conditions at well-studied
forest sites using well-tested models (ED2 and LPJ-GUESS). The severity and
patterns of biomass losses differed substantially between models. For
example, biomass loss could be sensitive to either drought duration or
drought intensity depending on the model approach. This is due to the models
having different, but also plausible, representations of processes and
interactions, highlighting the complicated variability of UCE impacts that still
need to be narrowed down in models. Elevated atmospheric CO<span class="inline-formula"><sub>2</sub></span>
concentrations (eCO<span class="inline-formula"><sub>2</sub></span>) alone did not completely buffer the
ecosystems from carbon losses during<span id="page2118"/> UCEs in the majority of our
simulations. Our findings highlight the consequences of differences in
process formulations and uncertainties in models, most notably related to
availability in plant carbohydrate storage and the diversity of plant
hydraulic schemes, in projecting potential ecosystem responses to UCEs. We
provide a summary of the current state and role of many model processes that
give way to different underlying hypotheses of plant responses to UCEs,
reflecting knowledge gaps which in future studies could be tested with
targeted field experiments and an iterative modeling–experimental conceptual
framework.</p> |
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| ISSN: | 1726-4170 1726-4189 |