Jun Tao¹, Bryan S. Griffiths³, Feng Hu², Yingjun Xu¹, Huixin Li^2*

1.State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China

2.College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China

3.Teagasc, Environment Research Centre, Johnstown castle, Wexford, Ireland

Abstract:The impact of earthworms (Metaphire guillelmi) on nematode and enchytraeid abundance was investigated in soil with added maize (suyu 19) residues in a laboratory experiment. Soil mixed with maize residues and earthworms was placed inside a mesh bag of different mesh size (1 mm or 5 µm), and then surrounded by an outside layer of soil mixed only with maize residues (i.e., no earthworms). The 1-mm diam. mesh would allow the movements of nematodes, enchytraeids, and soluble nutrients between the inner and outer soil but prevent the movements of earthworms. While the 5-µm diam. mesh would prevent the migration of earthworms, nematodes, and enchytraeids. The presence of earthworms significantly decreased the abundance of nematodes and enchytraieds in the inner soils of the different mesh-size treatments compared with that in the outer soils during the 7-wk incubation, except for enchytraeids at 1 wk. The presence of earthworms increased protozoan abundance in the inner soil. There was no significant difference in microbial biomass C between inner and outer soils at the end of experiment. Thus, abundant food resources (microbial biomass and protozoa) in the presence of earthworms indicate that competition for food and forced migration was not the main mechanism for decreased enchytraeid and nematode abundance.

Keywords: Earthworms; Nematodes; Enchytraeids; Protozoa; Food resource