Norwegian Institute for Nature Research (NINA), FRAM - High North Research Centre for Climate and the Environment, PO Box 6606 Langnes, NO-9296, Tromsø, Norway.
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, S901-83, Umeå, Sweden.
Glob Chang Biol. 2015 Nov;21(11):4063-75. doi: 10.1111/gcb.13007. Epub 2015 Sep 22.
Climate change impacts are not uniform across the Arctic region because interacting factors causes large variations in local ecosystem change. Extreme climatic events and population cycles of herbivores occur simultaneously against a background of gradual climate warming trends and can redirect ecosystem change along routes that are difficult to predict. Here, we present the results from sub-Arctic heath vegetation and its belowground micro-arthropod community in response to the two main drivers of vegetation damage in this region: extreme winter warming events and subsequent outbreaks of the defoliating autumnal moth caterpillar (Epirrita autumnata). Evergreen dwarf shrub biomass decreased (30%) following extreme winter warming events and again by moth caterpillar grazing. Deciduous shrubs that were previously exposed to an extreme winter warming event were not affected by the moth caterpillar grazing, while those that were not exposed to warming events (control plots) showed reduced (23%) biomass from grazing. Cryptogam cover increased irrespective of grazing or winter warming events. Micro-arthropods declined (46%) following winter warming but did not respond to changes in plant community. Extreme winter warming and caterpillar grazing suppressed the CO2 fluxes of the ecosystem. Evergreen dwarf shrubs are disadvantaged in a future sub-Arctic with more stochastic climatic and biotic events. Given that summer warming may further benefit deciduous over evergreen shrubs, event and trend climate change may both act against evergreen shrubs and the ecosystem functions they provide. This is of particular concern given that Arctic heath vegetation is typically dominated by evergreen shrubs. Other components of the vegetation showed variable responses to abiotic and biotic events, and their interaction indicates that sub-Arctic vegetation response to multiple pressures is not easy to predict from single-factor responses. Therefore, while biotic and climatic events may have clear impacts, more work is needed to understand their net effect on Arctic ecosystems.
气候变化的影响在北极地区并不均匀，因为相互作用的因素导致了当地生态系统变化的巨大差异。极端气候事件和食草动物的种群周期同时发生在气候逐渐变暖的背景下，可能会使生态系统发生变化，其变化路径难以预测。在这里，我们展示了亚北极石南植被及其地下微节肢动物群落对该地区两种主要植被破坏驱动因素的响应：极端冬季变暖事件和随后的落叶秋蛾毛虫（Epirrita autumnata）爆发。常绿矮灌木生物量在经历极端冬季变暖事件后减少了（30%），随后又因秋蛾毛虫取食而减少。以前经历过极端冬季变暖事件的落叶灌木不受秋蛾毛虫取食的影响，而那些没有经历过变暖事件的（对照区）则因取食而生物量减少（23%）。地衣类植物的盖度增加，而不论取食或冬季变暖事件。微节肢动物在冬季变暖后减少了（46%），但对植物群落的变化没有反应。极端冬季变暖与毛虫取食抑制了生态系统的 CO2 通量。在未来的亚北极地区，随着气候和生物随机性事件的增加，常绿矮灌木处于不利地位。由于夏季变暖可能使落叶灌木进一步受益于常绿灌木，因此事件和趋势气候变化可能都会对常绿灌木及其提供的生态系统功能产生不利影响。鉴于北极石南植被通常以常绿灌木为主，这尤其令人担忧。植被的其他组成部分对非生物和生物事件表现出不同的反应，它们的相互作用表明，亚北极植被对多种压力的反应不易从单一因素的反应中预测。因此，虽然生物和气候事件可能会产生明显的影响，但需要更多的工作来了解它们对北极生态系统的净影响。
