Institute of Ecology, Friedrich Schiller University Jena, Dornburger Strasse 159, 07743, Jena, Germany,
Oecologia. 2014 Jun;175(2):713-23. doi: 10.1007/s00442-014-2927-5. Epub 2014 Mar 26.
Global climate warming is one of the key forces driving plant community shifts, such as range shifts of temperate species into boreal forests. As plant community shifts are slow to observe, ecotones, boundaries between two ecosystems, are target areas for providing early evidence of ecological responses to warming. The role of soil fauna is poorly explored in ecotones, although their positive and negative effects on plant species can influence plant community structure. We studied nematode communities in response to experimental warming (ambient, +1.7, +3.4 °C) in soils of closed and open canopy forest in the temperate-boreal ecotone of Minnesota, USA and calculated various established nematode indices. We estimated species-specific coverage of understory herbaceous and shrub plant species from the same experimental plots and tested if changes in the nematode community are associated with plant cover and composition. Individual nematode trophic groups did not differ among warming treatments, but the ratio between microbial-feeding and plant-feeding nematodes increased significantly and consistently with warming in both closed and open canopy areas and at both experimental field sites. The increase in this ratio was positively correlated with total cover of understory plant species, perhaps due to increased predation pressure on soil microorganisms causing higher nutrient availability for plants. Multivariate analyses revealed that temperature treatment, canopy conditions and nematode density consistently shaped understory plant communities across experimental sites. Our findings suggest that warming-induced changes in nematode community structure are associated with shifts in plant community composition and productivity in the temperate-boreal forest ecotones.
全球气候变暖是推动植物群落变化的关键因素之一，例如温带物种向北方森林的分布范围转移。由于植物群落的变化难以观察，生态交错带（两个生态系统之间的边界）成为提供对变暖生态响应的早期证据的目标区域。尽管土壤动物对植物物种有积极和消极的影响，从而影响植物群落结构，但它们在生态交错带中的作用还没有得到充分的探索。我们研究了美国明尼苏达州温带-北方森林生态交错带中封闭和开放林冠下土壤中对线虫群落对实验增温（环境温度，+1.7°C 和+3.4°C）的响应，并计算了各种已建立的线虫指数。我们从同一实验样地估计了林下草本和灌木植物物种的特定物种覆盖率，并测试了线虫群落的变化是否与植物覆盖和组成有关。在增温处理中，单个线虫营养类群之间没有差异，但在封闭和开放林冠区以及两个实验现场，微生物食性和植物食性线虫的比例随着增温显著且一致地增加。这种比例的增加与林下植物物种的总覆盖率呈正相关，这可能是由于对土壤微生物的捕食压力增加，导致植物的养分可用性增加。多元分析表明，温度处理、林冠条件和线虫密度一致地塑造了跨实验地点的林下植物群落。我们的研究结果表明，线虫群落结构的变暖诱导变化与温带-北方森林生态交错带中植物群落组成和生产力的变化有关。
