以气候变暖为主要特征的全球气候变化的生态学效应越来越受到关注和重视。前期大多数研究表明，气候变化通过改变环境因子（温度、水分等）直接影响陆地生态系统属性，而很少关注升温通过营养级间互作对生态系统功能间接效应。在高海拔和高纬度地区，通常认为植物初级生产力随着温度的升高而增加，因为这些地区常年较低的气温限制了植物生长和养分的矿化速率，全球增温将减弱这种限制，改善这些地区生态系统的服务功能。但增温后的生态系统内部的营养级间互作也可能导致相反的结果。
中国科学院成都生物研究所生态中心孙书存研究员课题组李国勇博士等采用开顶箱装置，对青藏高原东部高寒草甸进行了三年的模拟增温实验。调查发现，群落中鹅绒委陵菜（高原鼢鼠的主要食物之一）的优势度在模拟增温后显著地增加，而其他物种群组的优势度保持不变或减少；模拟增温后的第三年，在增温样地内出现了植物被高原鼢鼠破环的现象，而对照样地的植物几乎都保持完好的状态；增温样地中，植物群落地上生物量也明显小于对照样地，这与前两年的两者对比情况相反。此外，鼢鼠洞穴密度与鹅绒委陵菜在群落中的优势度和生物量成正相关关系，这与野外调查结果一致。因此，研究得出，增温样地内出现的鼢鼠对植物地上生物量的下行效应可能主要是由增温引起物种组成和群落结构变化对鼢鼠取食行为的上行效应引起。
这种由于营养级间互作导致的（至少是短期内）生态系统退化提示，当前应用物种-气候模型预测气候变化对生态系统的影响可能存在缺陷，还意味着需要针对全球增温进行高寒草甸生态系统的适应性管理。作者建议利用提升地下水位、人工种植禾草和适度放牧干扰等管理措施来控制未来暖干化趋势下青藏高原高寒草甸鼠害的发生。
该研究结果发表在Journal of Applied Ecology 。（生物谷Bioon.com）
生物谷推荐原文出处：
Journal of Applied Ecology doi/10.1111/j.1365-2664.2011.01965.x
Experimental warming induces degradation of a Tibetan alpine meadow through trophic interactions
Guoyong Li1, Yinzhan Liu1, Lee E. Frelich2, Shucun Sun1,3,*
Keywords:alpine meadow;bottom-up and top-down control;global warming;Tibetan Plateau;trophic interaction
Summary
1. It is well known that climate change alters abiotic factors (temperature and water availability) that directly affect ecosystem properties. However, less is known about the indirect impacts of climate change on ecosystem structure and function. Here, we show that experimental warming may deteriorate ecosystems via trophic interactions.
2. In a Tibetan alpine meadow, plant species composition, size, coverage and above-ground biomass were investigated to reveal the effect of artificial warming (c. 1 °C mean annual temperature at the soil surface), which was accomplished using warmed and ambient open top chambers. In addition, rodent damage to plants was assessed.
3. The dicot forb silverweed Potentilla anserina increased significantly, while other species groups remained unchanged or decreased in plant community dominance rank after 2 years of artificial warming. The change in community structure was attributed to the difference in biomass allocation and growth form among species.
4. In the third year, plateau zokors Myospalax fontanierii, a widespread rodent herbivore, damaged plants in the warmed chambers, while leaving plants in the ambient chambers mostly undamaged. Above-ground biomass was found to be smaller in the warmed chambers than the controls in the third year, in contrast to the trend of the first 2 years. In addition, zokor burrow density was positively correlated with silverweed biomass and its dominance within communities, which was consistent with findings of independent field investigations that silverweed-dominated plots were more likely to be visited and damaged by the zokors than sites-dominated by grass species.
5. Synthesis and applications. The top-down negative effect of zokor damage on above-ground biomass in the warmed chambers was induced by the bottom-up effect of changes in species composition and community structure on zokor foraging behaviour, which were driven by artificial warming. Such trophic interactions may invalidate some predictions of ecological effects by current species-climate envelope models. Furthermore, because management measures including increasing the water table, planting grass and moderate cattle grazing may prevent silverweed dominance, we suggest that these interventions could be employed to control zokor damage in alpine meadows that are predicted to be drier and warmer in the future.
