以氣候變暖為主要特征的全球氣候變化的生態(tài)學(xué)效應(yīng)越來越受到關(guān)注和重視,。前期大多數(shù)研究表明,，氣候變化通過改變環(huán)境因子（溫度、水分等）直接影響陸地生態(tài)系統(tǒng)屬性,，而很少關(guān)注升溫通過營養(yǎng)級間互作對生態(tài)系統(tǒng)功能間接效應(yīng),。在高海拔和高緯度地區(qū)，通常認(rèn)為植物初級生產(chǎn)力隨著溫度的升高而增加,，因為這些地區(qū)常年較低的氣溫限制了植物生長和養(yǎng)分的礦化速率,，全球增溫將減弱這種限制,，改善這些地區(qū)生態(tài)系統(tǒng)的服務(wù)功能,。但增溫后的生態(tài)系統(tǒng)內(nèi)部的營養(yǎng)級間互作也可能導(dǎo)致相反的結(jié)果,。
中國科學(xué)院成都生物研究所生態(tài)中心孫書存研究員課題組李國勇博士等采用開頂箱裝置,，對青藏高原東部高寒草甸進(jìn)行了三年的模擬增溫實驗,。調(diào)查發(fā)現(xiàn),，群落中鵝絨委陵菜（高原鼢鼠的主要食物之一）的優(yōu)勢度在模擬增溫后顯著地增加,，而其他物種群組的優(yōu)勢度保持不變或減少,；模擬增溫后的第三年,，在增溫樣地內(nèi)出現(xiàn)了植物被高原鼢鼠破環(huán)的現(xiàn)象,，而對照樣地的植物幾乎都保持完好的狀態(tài)；增溫樣地中,，植物群落地上生物量也明顯小于對照樣地,，這與前兩年的兩者對比情況相反。此外,，鼢鼠洞穴密度與鵝絨委陵菜在群落中的優(yōu)勢度和生物量成正相關(guān)關(guān)系,，這與野外調(diào)查結(jié)果一致,。因此，研究得出,，增溫樣地內(nèi)出現(xiàn)的鼢鼠對植物地上生物量的下行效應(yīng)可能主要是由增溫引起物種組成和群落結(jié)構(gòu)變化對鼢鼠取食行為的上行效應(yīng)引起,。
這種由于營養(yǎng)級間互作導(dǎo)致的（至少是短期內(nèi)）生態(tài)系統(tǒng)退化提示，當(dāng)前應(yīng)用物種-氣候模型預(yù)測氣候變化對生態(tài)系統(tǒng)的影響可能存在缺陷,，還意味著需要針對全球增溫進(jìn)行高寒草甸生態(tài)系統(tǒng)的適應(yīng)性管理,。作者建議利用提升地下水位、人工種植禾草和適度放牧干擾等管理措施來控制未來暖干化趨勢下青藏高原高寒草甸鼠害的發(fā)生,。
該研究結(jié)果發(fā)表在Journal of Applied Ecology ,。（生物谷Bioon.com）
生物谷推薦原文出處：
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.
