气候因子通过土壤微生物生物量氮促进青藏高原高寒草地地上生态系统功能

近年来, 在人类活动和气候变化的影响下, 物种多样性丧失趋势不断加剧, 对生态系统功能带来严重后果。目前, 关于生态系统功能的研究, 忽略了土壤和微生物碳氮养分循环过程对地上生态系统功能(AEF)的重要驱动作用, 而土壤碳氮要素和微生物的任何变化都有可能改变地下群落对生态系统功能的维持作用。该研究旨在探究高寒草地AEF的主要控制因子, 以及其关键要素对AEF的作用机理。2015年7-8月, 对青藏高原地区115个样点进行了草地群落和土壤属性等要素样带调查; 综合植物地上生物量, 叶片碳、氮和磷含量等参数计算AEF值, 分析地下土壤有机碳含量、全氮含量、生物量等关键要素对AEF值的影响。结合取样点年降水量和年平均气温, 深入探讨影响AEF的主要控制因子和作用机理。结果表明降水对AEF有较大影响, 而气温影响相对较低。年降水量、土壤微生物生物量碳含量和干旱指数对AEF值的相对重要性贡献较高(重要值分别为21.1%、10.9%和10.1%), 控制青藏高原高寒草地AEF值的关键是土壤因子。在气候因子对土壤养分和微生物的作用下, 土壤微生物生物量氮含量在调控高寒草地AEF值方面发挥重要作用。

Climatic factors drive the aboveground ecosystem functions of alpine grassland via soil microbial biomass nitrogen on the Qingzang Plateau

Aims In recent years, under the background of climate change and human activities, the trend of biodiversity loss is increasing. Such accelerated loss in biodiversity could bring serious consequences to ecosystem functions. At present, the research on ecosystem function ignores the important driving role of carbon and nitrogen cycling in soil and microorganism on the above ground ecosystem functions. Any changes of soil carbon, nitrogen and microorganism may affect the ability of belowground community, which can have substantial effects on the aboveground ecosystem functions. Our aim was to explore the driving factors and key mechanism of abovegroud ecosystem functions (AEF) in alpine grassland.Methods From July to August 2015, we conducted a transect survey in alpine grasslands to measure plant community and soil properties across Qingzang Plateau. There were in total 115 sample sites. The aboveground ecosystem function was calculated based on the aboveground biomass, leaf carbon, leaf nitrogen and leaf phosphorus. The effects of key elements such as soil organic carbon, total nitrogen and biomass on the aboveground ecosystem function were analyzed. Combined with mean annual precipitation and air temperature, we explored important drivers of AEF and related mechanisms.Important findings Precipitation has a greater impact on aboveground ecosystem functions, while air temperature has a minor impact. Mean annual precipitation, soil microbial nitrogen content and aridity index had relative higher importance to aboveground ecosystem functions. Specificially, mean annual precipitation, soil microbial nitrogen content and aridity index accounted for the variations of 21.1%, 10.9% and 10.1%, respectively. The findings indicated that soil properties might play more important roles than plant community and productivity to aboveground ecosystem functions. Considering the cascading impacts of climate factors on soil nutrients cycling and microorganisms, soil microbial biomass nitrogen content plays an important role in regulating AEF of alpine grassland, Qingzang Plateau.