Faculty of Natural Resources Management, Lakehead University, Thunder Bay, ON, Canada.
Department of Ecosystem Studies, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Japan.
Glob Chang Biol. 2021 Aug;27(16):3846-3858. doi: 10.1111/gcb.15710. Epub 2021 May 30.
Global environmental changes have strongly affected forest demographic rates, particularly amplified tree mortality in high latitude forests (e.g., two to five times greater mortality probability over the half-century). Although forest functional composition is critical for multitrophic biodiversity and ecosystem functioning, it remains unclear how functional composition has changed over time across large high latitude regions, which have been warming twice the rate of the globe as a whole. Using extensive spatial and long-term forest inventory data (17,107 plots monitored 1951-2016) across Canada, we found that after accounting for stand age-dependent functional shifts, functional composition shifted toward fast-growing deciduous broadleaved trees and higher drought tolerance over time. The temporal shift toward deciduous broadleaved trees was consistent across the baseline climate. However, over the study period, drought tolerance increased (or shade tolerance decreased) by 300% in colder boreal regions, while drought tolerance did not shift significantly in warmer temperate climates. A further analysis accounting for temporal changes in atmospheric CO , temperature, and water availability indicated that the functional composition of colder regions shifted toward drought tolerance more rapidly with rising CO than warmer regions, suggesting the greater vulnerability of boreal forests than temperate forests under ongoing global environmental changes. Future ecosystem management practices should consider spatial differences in functional responses to global environmental change, focusing on high latitude forests experiencing higher rates of warming and compositional changes.
全球环境变化强烈影响了森林的生命统计率，特别是在高纬度森林中放大了树木死亡率（例如，在过去半个世纪中，死亡率的概率增加了两到五倍）。尽管森林功能组成对于多营养层生物多样性和生态系统功能至关重要，但目前仍不清楚在整个高纬度地区，随着全球变暖速度的两倍，功能组成随时间发生了怎样的变化。我们利用加拿大广泛的空间和长期森林清查数据（17107 个监测点，1951-2016 年），发现，在考虑到林分年龄相关的功能转变后，功能组成随时间推移逐渐向速生落叶阔叶树种和更高的耐旱性转变。在基线气候下，落叶阔叶树种的时间变化是一致的。然而，在研究期间，在较冷的北方地区，耐旱性增加（或耐荫性下降）了 300%，而在较温暖的温带气候中，耐旱性没有显著变化。进一步考虑到大气 CO2、温度和水分可用性的时间变化的分析表明，与温暖地区相比，较冷地区的功能组成向耐旱性的转变随着 CO2 的升高而更快，这表明在持续的全球环境变化下，北方森林比温带森林更脆弱。未来的生态系统管理实践应考虑到对全球环境变化的功能响应的空间差异，重点关注经历更高升温速度和组成变化的高纬度森林。
