Species-rich boreal forests grew more and suffered less mortality than species-poor forests under the environmental change of the past half-century (Hisano et al. 2019/Ecology Letters)

Climate and other global environmental changes are major threats to ecosystem functioning and biodiversity. However, the importance of plant diversity in mitigating the responses of functioning of natural ecosystems to long-term environmental change remains unclear. Using inventory data of boreal forests of western Canada from 1958-2011, we found that aboveground biomass growth increased over time in species-rich forests but decreased in species-poor forests, and importantly, aboveground biomass loss from tree mortality was smaller in species-rich than species-poor forests. A further analysis indicated that growth of species-rich (but not species-poor) forests was statistically positively associated with rising CO₂, and that mortality in species-poor forests increased more as climate moisture availability decreased than it did in species-rich forests. In contrast, growth decreased and mortality increased as the climate warmed regardless of species diversity. Our results suggest that promoting high tree diversity may help reduce the climate and environmental change vulnerability of boreal forests.

气候与其他全球环境变化是威胁生态系统功能与生物多样性的主要风险源。然而，植物多样性在缓解自然生态系统功能对长期环境变化的响应过程中的重要性，目前仍未明确。本研究基于1958年至2011年加拿大西部北方针叶林（boreal forests）的清查数据，分析得到如下结果：物种丰富的森林其地上生物量（aboveground biomass）随时间推移呈增长趋势，而物种贫乏的森林则表现为下降；尤为重要的是，物种丰富森林因树木死亡（tree mortality）导致的地上生物量损失，显著低于物种贫乏的森林。进一步分析显示，物种丰富（而非物种贫乏）的森林的生物量增长，与大气CO₂浓度升高呈统计学意义上的显著正相关；同时，随着气候可利用水分减少，物种贫乏森林的树木死亡率的上升幅度，显著高于物种丰富的森林。与之相反，无论物种多样性水平如何，气候变暖均会导致森林生物量增长下降、死亡率上升。本研究结果表明，提升林木多样性或有助于降低北方针叶林对气候与环境变化的脆弱性。