The ecological and biogeochemical importance of snow cover for temperate forest ecosystems

中欧的气候变暖在冬季最为强烈。然而，减少降雪可能会抵消土壤温度的上升。冬季通常是温带森林生态和生物地球化学的关键驱动因素。因此，积雪变化和土壤温度变化的影响需要科学关注，以便更好地了解气候影响。在气候变化实验中，(1)基于过程的理解和(2)条件的现实性允许合理的放大和推广。因此，我建议进行详细的实验室试验，旨在确定生态和生物地球化学过程的相关方面，即霜冻的幅度、持续时间、突然性或频率。此外，我建议在成熟森林中进行新的雪操纵实验，沿着冬季条件的梯度复制，以扩大规模和推广。积雪遮蔽和绝缘处理是一种新技术，它允许研究由于表面绝缘改变而导致的积雪变化，而不需要物理干扰或水和营养输入的改变。该野外试验将包括成熟树木的响应，这是在操纵实验中很少实现的特征。响应参数将提供广泛和一般的结果，包括大量的生态和生物地球化学过程，如成熟和幼树的生长、树木更新、林下物种组成、根系动力学、分解、矿化、氮循环和微量气体通量。此实地实验旨在作为跨学科研究的平台，将邀请对其他过程感兴趣的合作伙伴加入。在受控环境室进行的试验将重点关注两个关键参数，即优势树种（Fagus sylvatica）的萌发/建立和矿化。这些试验的目的是确定冬季温度制度的生态相关方面。这些知识对于推断对未来条件的影响是很重要的。优势树种是森林生态系统适应环境变化的关键。它们在其物种范围内和种群之间具有相当大的种内表型和遗传变异。因此，将在实验室和实地实验中研究当地对冬季条件的适应以及种群内部和种群之间的一般可塑性。综上所述，提出的实验将提高对生态学和生物地球化学冬季气候影响的认识。在非常受控制的条件下收集这些信息，以便了解过程，并在几个地点的实地条件下收集这些信息，以便在景观尺度上进行概括，这对于改进耦合的大气-生物圈模型以及积极主动地管理气候变化是相关的。

Climate warming in central Europe is strongest over winter. Less snow, however, can potentially counteract increasing soil temperature. Winter is generally a crucial driver of ecology and biogeochemistry in temperate forests. Effects of altered snow cover and more variable soil temperatures therefore require scientific attention for a better understanding of climate impacts.In climate change experiments (1) process-based understanding and (2) realism of conditions allowing for sound up-scaling and generalization are sought. Therefore, I propose detailed laboratory trials aiming at the identification of the relevant facets, i.e. magnitude, duration, abruptness, or frequency of frost, for ecological and biogeochemical processes. In addition, I propose novel snow manipulation experiments in mature forests, replicated along a gradient of winter conditions, for up-scaling and generalizations.Snow-out shelters and insulation treatments are novel techniques which allow for the study of alterations in snow cover due to altered insulation of the surface without physical disturbance or alterations of water and nutrient input. This field experiment will include the response of mature trees, a feature rarely achieved in manipulation experiments. Response parameters will provide broad and general results by covering a multitude of ecological and biogeochemical processes such as growth of mature and juvenile trees, tree regeneration, understory species composition, root dynamics, decomposition, mineralization, nitrogen cycling, and trace gas fluxes. This field experiment is intended as a platform for interdisciplinary studies, cooperation partners interested in additional processes will be invited to join.Trials in controlled-environment chambers will focus on two key parameters, i.e. germination/ establishment of the dominant tree species (Fagus sylvatica) and mineralization. These trials will aim at the identification of the ecologically relevant facets of winter temperature regimes. This knowledge is important for the extrapolation of effects to future conditions. Dominant tree species are key in the adaptation of forest ecosystems to altered environments. They harbor considerable intra-specific phenotypic and genetic variability within and among populations in their species ranges. Local adaptations to winter conditions and, generally, plasticity within and among populations will therefore be studied in both, the laboratory and the field experiments.Taken together, the proposed experiments will improve the understanding of winter climate impacts in ecology and biogeochemistry. Gathering such information under very controlled conditions allowing for process-understanding and under field conditions at several sites allowing for generalizations at the landscape scale is relevant for improving coupled atmosphere-biosphere models as well as proactive management of climate change.