干旱与半干旱区红砂枯落物分解初期节肢动物群落结构特征

Two desertified grasslands in semi-arid Yanchi County of Ningxia and in arid Urat Rear Banner of Inner Mongolia were selected as sites to study litter decomposition of Reaumuria soongorica. Litter bags were set up between shrub microhabitats beneath the shrub canopy and in the open spaces. The litter arthropod community composition and diversity were investigated, as well as the litter chemical composition and soil conditions. The objective of the present study was to explore the differences in litter arthropod community composition and diversity between shrub microhabitats in semi-arid Yanchi County and a more arid Urat site. It was found that: 1) There were 3 dominant taxa of litter arthropods beneath shrub canopy and 2 dominant taxa in the open spaces in semi-arid Yanchi; there were 3 dominant taxa in both microhabitats in arid Urat. There were 7 commonly occurring taxa beneath shrub canopy, and 3 found in the open spaces in semi-arid Yanchi; while there were 7 commonly occurring taxa beneath shrub canopy and 4 in the open spaces in arid Urat. Rare species were found in the open spaces only in semi-arid Yanchi, and beneath shrub canopy only, in arid Urat. 2) The abundance and species richness of litter arthropods was found to be significantly higher in the open spaces than beneath shrub canopy in semi-arid Yanchi, but followed the reverse distribution in arid Urat (P<0.05). There were no significant differences in Shannon-Wiener index, Simpson index, Margalef index, and Pielou index between the two shrub microhabitats at either of the study sites. 3) The abundance of litter arthropods was found to be positively correlated with soil pH and negatively correlated with soil sand content. Species richness was negatively correlated with soil sand content in semi-arid Yanchi only (P<0.05). The abundance of litter arthropods and species richness were uncorrelated with environmental factors in the arid area of Urat Rear Banner (P>0.05). From the results of redundancy analysis and partial redundancy analysis showed that litter K content of litter was the main factor driving the distribution of litter arthropods in arid and semi-arid areas. In conclusion, both shrub microhabitats and climatic factors affected the abundance and group richness of litter deposition, while there was little effect on litter arthropod diversity. With increased aridity, there was a transition from an 'overflow' effect towards a 'facilitative' effect of shrubs on the distribution of litter arthropod abundance and species richness.