Dorheim Kalyn, Gough Christopher M, Haber Lisa T, Mathes Kayla C, Shiklomanov Alexey N, Bond-Lamberty Ben
Joint Global Change Research Institute Pacific Northwest National Laboratory College Park MD USA.
Department of Biology Virginia Commonwealth University Richmond VA USA.
J Geophys Res Biogeosci. 2022 Jan;127(1):e2021JG006587. doi: 10.1029/2021JG006587. Epub 2022 Jan 13.
Forests dominate the global terrestrial carbon budget, but their ability to continue doing so in the face of a changing climate is uncertain. A key uncertainty is how forests will respond to (resistance) and recover from (resilience) rising levels of disturbance of varying intensities. This knowledge gap can optimally be addressed by integrating manipulative field experiments with ecophysiological modeling. We used the Ecosystem Demography-2.2 (ED-2.2) model to project carbon fluxes for a northern temperate deciduous forest subjected to a real-world disturbance severity manipulation experiment. ED-2.2 was run for 150 years, starting from near bare ground in 1900 (approximating the clear-cut conditions at the time), and subjected to three disturbance treatments under an ensemble of climate conditions. Both disturbance severity and climate strongly affected carbon fluxes such as gross primary production (GPP), and interacted with one another. We then calculated resistance and resilience, two dimensions of ecosystem stability. Modeled GPP exhibited a two-fold decrease in mean resistance across disturbance severities of 45%, 65%, and 85% mortality; conversely, resilience increased by a factor of two with increasing disturbance severity. This pattern held for net primary production and net ecosystem production, indicating a trade-off in which greater initial declines were followed by faster recovery. Notably, however, heterotrophic respiration responded more slowly to disturbance, and it's highly variable response was affected by different drivers. This work provides insight into how future conditions might affect the functional stability of mature forests in this region under ongoing climate change and changing disturbance regimes.
森林主导着全球陆地碳收支，但在气候变化的情况下它们能否继续保持这种状态尚不确定。一个关键的不确定性在于森林将如何应对（抵抗力）以及从不同强度不断增加的干扰中恢复（恢复力）。通过将操纵性田间试验与生态生理模型相结合，能够最佳地填补这一知识空白。我们使用生态系统人口统计学 - 2.2（ED - 2.2）模型来预测一个北方温带落叶林在实际干扰严重程度操纵实验中的碳通量。ED - 2.2运行了150年，从1900年近乎光秃的地面开始（近似当时的皆伐条件），并在一系列气候条件下接受三种干扰处理。干扰严重程度和气候都强烈影响碳通量，如总初级生产力（GPP），并且二者相互作用。然后我们计算了抵抗力和恢复力，这是生态系统稳定性的两个维度。模拟的GPP在死亡率分别为45%、65%和85%的不同干扰严重程度下，平均抵抗力下降了两倍；相反，恢复力随着干扰严重程度的增加而增加了两倍。这种模式在净初级生产力和净生态系统生产力方面也成立，表明存在一种权衡，即初始下降幅度越大，恢复速度越快。然而，值得注意的是，异养呼吸对干扰的响应较慢，并且其高度可变的响应受到不同驱动因素的影响。这项工作为未来条件如何在持续的气候变化和不断变化的干扰 regime 下影响该地区成熟森林的功能稳定性提供了见解。
