Data_Sheet_1_Effects of Temperature and Water Availability on Northern European Boreal Forests.pdf

Boreal forests are warming faster than the rest of the planet. Do the benefits of higher temperatures and longer growing seasons for forest productivity exceed the negative effects of more frequent dry spells and heat waves, shifting precipitation patterns, and higher evaporative demands? And are the effects uniformly distributed geographically? To answer to these questions, the relationship between climatic variables and NDVI—a proxy of forest productivity at regional scale—was explored via Partial Least Square (PLS) regression analyses. We focused on Northern Europe, where contrasting findings on the effects of warming have been reported and that has so far been overlooked by systematic large-scale explorations of the linkages between boreal forest productivity and climatic conditions. The results show that the effects of warmer temperatures on boreal forest productivity are not uniformly positive and that water stress is already negatively affecting these forests. Indeed, increased temperatures appear beneficial in northern and wetter regions, while warmer temperatures mostly reduce forest productivity in southern and drier areas. These results are suggestive of already existing limitations due to water availability and warm temperatures, even in mesic regions like Northern Europe. These conditions are expected to become more frequent and intense in the future, potentially reducing the ability of boreal forests to provide their essential ecosystem services unless forest management practices are adapted to the new conditions.

北极森林的升温速度超过了地球其他地区。在较高温度和更长的生长季节对森林生产力有益的同时，频繁的干旱期和热浪、降水模式的转变以及更高的蒸发需求所带来的负面影响是否能够得到超越？这些影响在地理上是否均匀分布？为了解答这些问题，本研究通过偏最小二乘回归分析（Partial Least Square, PLS）探讨了气候变量与归一化植被指数（NDVI，区域尺度下森林生产力的代理指标）之间的关系。研究聚焦于欧洲北部，该地区关于升温效应的研究结果相互矛盾，且迄今为止尚未被系统的大规模探索所关注，这些探索旨在研究北极森林生产力和气候条件之间的联系。研究结果揭示，温暖温度对北极森林生产力的影响并非普遍呈正效应，且水分胁迫已经对这些森林产生了负面影响。实际上，温度上升在北部和湿润地区似乎有益，而温暖温度在南部和干旱地区主要降低了森林生产力。这些发现暗示了由于水资源和温暖温度的限制，即使在北欧这样的中生地区，也早已存在。预计未来这些条件将变得更加频繁和剧烈，除非森林管理实践适应新的条件，否则北极森林提供其基本生态系统服务的能力可能会降低。