Estimating function of earthworm communities based on stoichiometry

人类活动正在改变全球生态系统和气候中的氮磷循环。蚯蚓是改变凋落物分解和土壤物理结构的土壤生态工程师。气候变化和大气氮沉降和施肥对N、P生态系统循环的干扰可能会改变土壤动物，特别是蚯蚓的群落结构，因为N和P往往限制陆地栖息地的养分。通过对土壤和蚯蚓体内N、P含量的研究，估算了NP平衡扰动对生态系统水平的影响。蚯蚓的存在大大提高了土壤N的矿化速率，不仅土壤微生物，而且蚯蚓也是氮素的驱动力。田间条件下，萨莎叶片的落叶促进了土壤微食物网从根系分泌物开始，土壤细菌和杆状线虫发生变化。在田间微观世界条件下，叶片品质影响蚯蚓的生长，体内N：P与蚯蚓的生长也有很好的相关性。表生蚯蚓生长速度快，N：P低，而内生种生长缓慢，N：P含量高，N、P是决定蚯蚓群落结构的重要因素。

Human activities are now changing global nitrogen and phosphorus cycling in ecosystem as well as climate. Earthworms are soil ecosystem engineers modifying litter decomposition and soil physical structures. Climate change and disturbances in ecosystem cycling of N and P due to atmospheric nitrogen deposition and fertilization may change community structure of soil animals, especially, earthworms, because N and P are often limiting nutrients in terrestrial habitat. I studied N and P contents in soil and earthworms and tried to estimate ecosystem level effects of disturbance in NP balance.Soil N mineralization rates were greatly enhanced by the presence of earthworms, thus not only soil microorganisms but also earthworms are nitrogen driver. Defoliation of Sasa leaves in a field condition promoted soil micro-food web starting from root exudation, and then soil bacteria and bactrivorus nematodes were observed to change. Finally nitrogen mineralization was enhanced.Leaf quality affected earthworm growth in a field microcosm condition, and also there was a good correlation between body N:P and growth of Japanese earthworms. Epigeic earthworms had high growth rate and low N:P, and in contrast to this, endogeic species are slow grower and had high N:P. N and P are thus important determinant for community structure of earthworms.