Estimating function of earthworm communities based on stoichiometry

人类活动正在改变着全球生态系统中氮磷的循环和气候。蚯蚓是土壤生态系统的工程师，改变凋落物的分解和土壤的物理结构。气候变化和大气氮沉降及施肥对生态系统氮磷循环的干扰可能会改变土壤动物的群落结构，尤其是蚯蚓，因为氮磷往往是陆地生境中的限制性营养元素。研究了土壤和蚯蚓中的N和P含量，并试图估计生态系统水平上的NP平衡干扰的影响。蚯蚓的存在大大提高了土壤N矿化速率，因此，不仅土壤微生物，而且蚯蚓是氮驱动器。在田间条件下，落叶促进了从根系分泌物开始的土壤微食物网，随后观察到土壤细菌和食杆菌线虫的变化。在田间微宇宙条件下，叶片质量影响蚯蚓的生长，蚯蚓体氮磷比与蚯蚓的生长也有很好的相关性。地上型蚯蚓生长速度快，N：P低，而内生型蚯蚓生长缓慢，N：P高，N、P是蚯蚓群落结构的重要决定因素。

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.