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

欧洲中部的气候变暖在冬季最为严重。然而，较少的降雪可能会抵消不断上升的土壤温度。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，雪盖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)允许合理扩大和推广的条件的现实主义。因此，我建议进行详细的实验室试验，以确定生态和生物地球化学过程的相关方面，即霜冻的大小、持续时间、突发性或频率。此外，我建议在成熟的森林中进行新的积雪操作实验，沿着冬季条件的梯度进行复制，以扩大和推广。积雪庇护所和绝缘处理是新技术，允许研究由于表面绝缘改变而导致的积雪覆盖变化，而不会造成物理干扰或水和养分输入的改变。这项田间实验将包括成熟树木的反应，这是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，涵盖许多生态和生物地球化学过程，如成年树和幼树的生长、树木再生、林下物种组成、根系动态、分解、矿化、氮循环和微量气体通量。这项实地实验旨在作为跨学科研究的平台，将邀请对更多过程感兴趣的合作伙伴加入。在受控环境室内的试验将集中在两个关键参数上，即优势树种(Fagus Sylvatica)的萌发/建立和矿化。这些试验将旨在确定冬季温度制度的生态相关方面。这一知识对于推断对未来状况的影响很重要。优势树种是森林生态系统适应变化环境的关键。它们在其物种范围内的种群内和种群之间具有相当大的种内表型和遗传变异性。因此，将在实验室和野外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可塑性。综合而言，拟议的实验将提高对冬季气候影响的生态学和生物地球化学的理解。在非常受控的条件下和在几个地点的实地条件下收集这类信息，以便在景观范围内进行概括，对于改进大气-生物圈耦合模型以及积极主动地管理气候变化具有重要意义。

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.