Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities
Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities
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DOI：
10.1088/1748-9326/6/4/045509
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发表时间：
2011-10-01
影响因子：
6.7
通讯作者：
Hik, David S.
中科院分区：
文献类型：
--
作者：
Myers-Smith, Isla H.;Forbes, Bruce C.;Hik, David S.
最近的研究使用重复摄影，长期生态监测和树木年代学记录了灌木在北极，高纬度和高山冻原生态系统的扩张。在这里，我们（1）综合这些研究结果，（2）提出一个概念框架，确定机制和灌木增加的限制，（3）探讨原因，反馈和影响增加灌木覆盖苔原生态系统，（4）解决潜在的调查路线，为未来的研究。从北极圈周围进行的卫星观测显示，生产力的提高，以“绿色”的变化来衡量，与高纬度气温的普遍上升相吻合，部分原因是灌木覆盖率的增加。研究表明，气温变暖，积雪覆盖的变化，改变干扰制度的结果，永久冻土融化，苔原火灾，人为活动或草食动物的强度变化都有助于观察到的变化灌木丰富。灌木覆盖的大规模增加将改变苔原生态系统的结构，并改变能量通量、区域气候、土壤-大气水、碳和养分的交换以及物种之间的生态相互作用。为了预测未来的灌木扩展速率，并了解对生态系统和气候过程的反馈，未来的研究应该调查灌木对气候变化的物种或性状特异性反应，包括：（1）灌木生长的温度敏感性，（2）控制新个体补充的因素，以及（3）参与灌木扩展的正反馈和负反馈的相对影响。
Recent research using repeat photography, long-term ecological monitoring and dendrochronology has documented shrub expansion in arctic, high-latitude and alpine tundra ecosystems. Here, we (1) synthesize these findings, (2) present a conceptual framework that identifies mechanisms and constraints on shrub increase, (3) explore causes, feedbacks and implications of the increased shrub cover in tundra ecosystems, and (4) address potential lines of investigation for future research. Satellite observations from around the circumpolar Arctic, showing increased productivity, measured as changes in 'greenness', have coincided with a general rise in high-latitude air temperatures and have been partly attributed to increases in shrub cover. Studies indicate that warming temperatures, changes in snow cover, altered disturbance regimes as a result of permafrost thaw, tundra fires, and anthropogenic activities or changes in herbivory intensity are all contributing to observed changes in shrub abundance. A large-scale increase in shrub cover will change the structure of tundra ecosystems and alter energy fluxes, regional climate, soil-atmosphere exchange of water, carbon and nutrients, and ecological interactions between species. In order to project future rates of shrub expansion and understand the feedbacks to ecosystem and climate processes, future research should investigate the species or trait-specific responses of shrubs to climate change including: (1) the temperature sensitivity of shrub growth, (2) factors controlling the recruitment of new individuals, and (3) the relative influence of the positive and negative feedbacks involved in shrub expansion.