Effect of tillage systems on community structure of soil mites

Soil mites has been used as an important bio-indicator of soil ecosystem. An experiment was set up to determine the effects of tillage systems on individual number, family number, community structure and vertical distribution of soil mites. The experiment was conducted at the National Observation Station of Hailun Agroecology System in Northeast China. The tillage systems used for the experiment included no-tillage, limited tillage, moldboard plough, combination tillage and rotary tillage. Soil samples were collected from 0~15 cm soil layer under different tillage systems in May, June and July of 2009 and modified Tullgren method used to extract soil mites from the soil samples. The individual and family numbers were significantly affected by different tillage systems. A total of 2 441 soil mites were captured in the study. There were respectively 366, 436, 553, 819 and 267 soil mites under no-tillage, reduced tillage, combination tillage, rotary tillage and moldboard plough, corresponding to 13, 18, 13, 14 and 11 families under each tillage system. The highest individual number of soil mites was in rotary tillage field while the highest family number of soil mites was in limited tillage field. The vertical distribution of soil mites was affected by different tillage systems and sampling times. With the exception of no-tillage, there was faunal accumulation in the soil surface layer in May under the tillage systems. The individual number of soil mites was significantly higher in the 0~5 cm soil layer than in the 5~10 cm and 10~15 cm soil layers (P < 0.05). Also faunal accumulation in the soil surface layer at all the three sampling times was noted under combined tillage and limited tillage systems. Soil mites diversity was preserved under limited tillage. MGP analysis showed that the composition of soil oribate mites changed with season. The dominant family of soil oribate mites changed from senior oribate to junior oribate mites, which was more obvious under no-tillage and limted tillage than the other tillage systems. While the composition type of soil oribate mites was P, G and O under limited tillage at the three sampling times, it was P, O and G under no-tillage system. Conservation tillage systems (i.e., no-tillage and limited tillage) better preserved community diversity and stability of soil mites than the other tillage systems. Conservation tillage was also protective for soil environment.