Data from: Short-term climate change manipulation effects do not scale up to long-term legacies: effects of an absent snow cover on boreal forest plants

1. Despite time lags and non-linearity in ecological processes, the majority of our knowledge about ecosystem responses to long-term changes in climate originates from relatively short-term experiments.
2. We utilized the longest ongoing snow removal experiment in the world and an additional set of new plots at the same location in northern Sweden to simultaneously measure the effects of long-term (11 winters) and short-term (1 winter) absence of snow cover on boreal forest understorey plants, including effects on root growth and phenology.
3. Short-term absence of snow reduced vascular plant cover in the understorey by 42%, reduced fine root biomass by 16%, reduced shoot growth by up to 53%, and induced tissue damage on two common dwarf shrubs. In the long-term manipulation, more substantial effects on understorey plant cover (92% reduced) and standing fine root biomass (39% reduced) were observed, whereas other response parameters, such as tissue damage, were observed less. Fine root growth was generally reduced, and its initiation delayed by c. 3 (short-term) to 6 weeks (long-term manipulation).
4. Synthesis We show that one extreme winter with a reduced snow cover can already induce ecologically significant alterations. We also show that long-term changes were smaller than suggested by an extrapolation of short-term manipulation results (using a constant proportional decline). In addition, some of those negative responses, such as frost damage and shoot growth, were even absolutely stronger in the short-term compared to the long-term manipulation. This suggests adaptation or survival of only those individuals that are able to cope with these extreme winter conditions, and that the short-term manipulation alone would over-predict long-term impacts. These results highlight both the ecological importance of snow cover in this boreal forest, and the value of combining short- and long-term experiments side by side in climate change research.

1. 尽管生态过程存在时间滞后性与非线性特征，当前我们关于生态系统对气候长期变化响应的认知，大多源自相对短期的实验研究。
2. 本研究采用全球持续时长最长的在研除雪实验（snow removal experiment）平台，并在瑞典北部的同一研究区域增设了一组全新样地，以此同步探究长期（11个冬季）与短期（1个冬季）无雪覆盖对北方针叶林（boreal forest）林下植物（understorey plants）的影响，涵盖根系生长与物候学（phenology）相关的各项效应。
3. 短期无雪覆盖可使林下维管植物（vascular plant）盖度降低42%，细根生物量减少16%，地上部分生长最多下降53%，并对两种常见矮灌木造成组织损伤。在长期人为处理组中，林下植物盖度（降低92%）与现存细根生物量（降低39%）受到的影响更为显著，而其他响应参数（如组织损伤）的观测效应则相对较弱。整体而言，细根生长受到抑制，其起始时间较对照组分别延迟了约3周（短期处理组）至6周（长期处理组）。
4. 研究综合 本研究证实，仅一个降雪量减少的极端冬季即可引发具有生态学意义的显著改变。同时发现，长期气候变化的实际效应小于基于短期处理结果（采用恒定比例下降法）外推得到的预测值。此外，部分负面响应（如冻害与地上部分生长）在短期处理组中的绝对强度甚至高于长期处理组。这表明，仅存的存活个体均为能够适应此类极端冬季条件的类群，单纯依靠短期处理实验会高估长期影响。本研究结果既凸显了该北方针叶林生态系统中雪盖的生态学重要性，也证实了在气候变化研究中同步开展短期与长期实验的研究价值。