Species diversity of soil animals at different desert habitats in Baijitan region of Ningxia and its relationship with environmental factors

Soil animals play an important role in terrestrial ecosystems. It can not only indicate the subtle variation of habitats, but also reflect the trend of ecological communities. Diversity of soil animals is an important part of biodiversity study of soil. In recent years, desert habitat diversity in Baijitan National Nature Reserve of Lingwu in Ningxia has formed along with the development of control engineering. However, there is lack of the information on the diversity and distribution patterns of soil animals, the correlation between distribution patterns of soil animals and process of habitat change.Knowledge of the temporal variability of soil animal populations and species is crucial to understand the soil community dynamics. The main purposes of this study were to elucidate 1) the characteristics and differences of soil animal diversity at different habitats, and 2) the ecological factors affecting the distribution pattern and diversity of soil animals. These studies will have important significance on monitoring and conservation of biological diversity.To understand diversity features of soil faunal community in desert landscape, seven sample plots with the habitat types of desert steppe (DS) , artificial sand-fixation land (AS) and shifting and semi-shifting dune land (SL) were selected as study sites. The area of each plot is about 600 m² (6 m×100 m) . The segregate efficiency of soil animals among the 0-5, 5-10, 10-15 to 15-20 cm layer in different plots was studied using Tullgren and Baermann methods in August, 2013. Plant diversity was surveyed by quadrat method. Soil temperature, nutrients and physico-chemical factors were measured.By preliminary identification, there were 260 specimens of soil animals, which belonged to 2 phyla, 3 classes, 8 orders and 18 families. Tarsonemidae, Carabidae and Cicadellidae were the dominant groups. Density index and species richness index of DS were significantly higher than AS and SL (P<0.05) . Shannon-Wiener diversity index of DS were significantly higher than AS (P<0.05) . Simpson dominance index of SL was significantly higher than DS (P<0.05) . Soil animals were principally assembled on surface layer. The vertical distribution of soil animals decreased with increasing soil depth. The surface aggregation of soil animals in SL was more obvious than that of the AS and DS. The density of soil animals, Simpson dominance index, species richness index and Shannon-Wiener diversity index were highest on 0-5 cm soil layer in DS, SL and AL. Compared with the same soil layer, richness and Shannon-Wiener diversity indices showed DS>AS>SL, which turned out that in succession of SL to DS, the density and the number of soil animals increased. Redundancy analysis showed that soil water content, organic carbon, total nitrogen, total phosphorus, and plant diversity index were sensitive to the diversity of soil animals. Partial correlation analysis showed that the main factors affecting the soil animal diversity of surface soil layer were soil temperature, soil water content, organic carbon, total nitrogen and plant diversity index, and the factors affecting the diversity of animal of deep soil layer was soil water content.It is concluded that soil animals in desert habitats are principally assembled on surface layer. Diversity of soil animals is obviously affected by habitat heterogeneity, which tend to be more complicated with higher habitat heterogeneity and lower desertification degree of soil. Soil water content, organic carbon and plant diversity index are the main ecological factors affecting the diversity of desert soil animals.