The Ecological Importance of Winter in Temperate, Boreal, and Arctic Ecosystems in Times of Climate Change
The Ecological Importance of Winter in Temperate, Boreal, and Arctic Ecosystems in Times of Climate Change
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DOI：
10.1007/124_2019_35
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
J. Kreyling
中科院分区：
文献类型：
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作者：
J. Kreyling
气候变暖在冬季和北部生态系统中最为强烈。然而，生态和生物地球化学影响主要取决于土壤温度。由于积雪的重要性，气候变暖会对北部生物群落的冬季土壤条件产生相反的影响：冬季降水增加导致北极土壤变暖，而仲冬融雪事件可能会在北极和北方生态系统中引起更严重的土壤霜冻。由于积雪大幅减少，不再使土壤与仍然寒冷的空气温度隔绝，预计冷温带生态系统将经历更多的土壤霜冻。在冷温带生态系统中，变暖最终会导致土壤霜冻完全消失。土壤变暖和土壤冷却这两种途径对生态和生物圈-大气反馈都有重要影响：在北极和北方生态系统中，分解和矿化的增加可以提高初级生产力，但仲冬融化之后的霜冻和/或雨雪事件可能会抵消这一趋势。地表温度变化较大可能会损害初级生产，而由于积雪减少而导致土壤温度降低，可以显着减少寒温带生态系统的分解。对于冷温带生态系统来说，潮湿的冬季可能会导致养分流失，而尽管空气变暖，休眠模式的改变可能会导致霜冻损害增加。总之，冬季过程显然与生物圈-大气反馈相关，甚至这种反馈的符号，即生态系统作为碳汇或碳源，也取决于温带、北方和北极生态系统的冬季过程。本次审查的结论是，目前的知识不足以以令人满意的确定性量化这种反馈。确定重要过程和关键不确定性，例如地上与地下生长季节的同步性；生态过程中的时间层次，例如根系损伤的作用和根系活动对土壤有机质分解的作用（“启动”）；或由于冬季气候变化而导致的植物物种组成的变化，决定了初级生产以及凋落物数量和可分解性。显然，对未来生态系统功能和生物对气候变化的反馈的合理预测需要全面了解冬季生态过程，而迄今为止，这一过程常常被忽视。
Climate warming is strongest in winter and in northern ecosystems. Ecological and biogeochemical impacts, however, depend mainly on soil temperatures. Climate warming can contrastingly affect winter soil conditions across northern biomes due to the crucial importance of snow cover: Increasing winter precipitation results in soil warming in the arctic, while midwinter snowmelt events can induce more severe soil frost in arctic and boreal ecosystems. Cold-temperate ecosystems are projected to experience increased soil frost due to strongly reduced snow cover no longer insulating the soil against still cold air temperatures. In cool-temperate ecosystems, warming eventually causes the complete loss of soil frost. Both pathways, soil warming and soil cooling, have important implications for ecology and biosphere-atmosphere feedbacks: In arctic and boreal ecosystems, increased decomposition and mineralization allow for enhanced primary production, but midwinter melting followed by frost and/or rain-on-snow events might counteract this trend. More variable surface temperatures can damage primary production, and colder soil temperatures, due to reduced snow cover, can significantly decrease decomposition in cold-temperate ecosystems. For cool-temperate ecosystems, wetter winters could result in nutrient leaching, and altered dormancy patterns could cause increased frost damage despite air warming. In summary, winter processes are clearly relevant for the biosphere-atmosphere feedback, and even the sign of this feedback, i.e., ecosystems acting as carbon sink or as carbon source, depends on winter processes in temperate, boreal, and arctic ecosystems. This review concludes that current knowledge is not sufficient to quantify this feedback with satisfactory certainty. Important processes and the key uncertainties are identified, e.g., synchronicity in above- versus belowground growing season; temporal hierarchies in ecological processes such as the role of root damage and root activity for decomposition of soil organic matter (“priming”); or shifts in plant species composition due to winter climate change determining primary production as well as litter quantity and decomposability. Evidently, sound projections of future ecosystem functioning and biotic feedbacks to climate change require a comprehensive understanding of winter ecological processes, which have so far too often been neglected.