Bug island effect of shrubs in Horqin Sand Land of North China and related formation mechanisms

In 2008 -2009, an investigation was conducted on the community characteristics of soil macro-fauna within and outside the Caragana microphylla and Salix gordejevii in Horqin Sand Land, aimed to understand whether the shrubs in mobile sand land could gather soil macro-fauna. As compared with those outside the shrubs, the group number, individual density, and Shannon diversity of soil macro-fauna within the shrubs were increased by 125. 0% -175. 0% 52.8% -263.9%, and 34.6% -57. 1%, respectively, indicating that shrubs had obvious '4bug island" effect in mobile sand land. C. microphylla had a greater "bug island" effect than S. gordejevii. Within and outside the shrubs, there were the same dominant groups and a few common groups of soil macro-fauna. However, many soil macro-faunal groups which couldn' t survive outside the shrubs appeared within the shrubs, and the functional group structure of the macro- fauna had obvious change. The "bug island" effect of the shrubs in mobile sand land mainly came from the microclimate effect and "fertile island" effect of shrubs, which reduced wind speed and detained dust, occluded hot sun, improved soil texture and soil moisture, and increased soil nutrient contents, being the main mechanisms of the shrubs in mobile sand land in gathering soil macro-fauna.