Effects Of Climatic Factors And Soil Nutrients On Species Diersity, Productivity And Their Relationship In Desert Steppe

The effects of environmental factors on species diversity and ecosystem function is one of the core issues in ecology. Desert steppe is an extremely important part of grassland ecosystem in Inner Mongolia. It is essential to conduct research on species diversity and ecosystem function and the relationships among them with environmental factors. In this study,80 sampling sites were set to investigate vegatation and soil to get the data of species diversity, productivity and soil nutrients across the desert steppe, Inner Mogolia. Combined with climatic data, we have probed the effects of mean annual precipitation, mean annual temperature, aridity index and soil nutrients on species diversity and productivity, determined the dominant environmental factors which affected diversity and productivity particularly and analyzed the relationship between species diversity and productivity. The main results are as follows:(1) Soil nutrient content of Inner Mongolian desert steppe was very scarce, and soil fertility was at a low level. The content of soil total nitrogen, total phosphorus, available nitrogen, available phosphorus and soil organic carbon was 0.116%,0.036%, 45ppm,29ppm and 1.298%, respectively. According to the second national soil survey, soil total nitrogen was belong to moderate state, soil total phosphorus was extremely lacked, soil available nitrogen was greatly lacked, soil organic carbon was lacked, however, only available phosphorus content was belong to relatively rich state.(2) Species diversity and productivity of Inner Mongolian desert steppe were significantly affected by climatic factors. The results showed that species diversity and productivity were both positively and linearly correlated with mean annual precipitation and aridity index, however, they were both negatively and linearly correlated with mean annual temperature. The coefficients of determination between aridity index with species richness and productivity were higher than other climatic factors.(3) Effects of different soil nutrients on species diversity and productivity were not alike, soil nitrogen had an important impact on species diversity and productivity of desert steppe. The species diversity of the communities rose with increasing soil available nitrogen content and declined with increasing soil total phosphorus content. Productivity of the communities was positively and linearly correlated with soil organic carbon, soil total nitrogen and soil available nitrogen content.(4) This study has clearly pointed out water and temperature were the most influential factors affecting species diversity and productivity of desert steppe. Aridity index is an integrated indicator of water and temperature. Aridity index was introduced into multiple stepwise regression model as the first factor to explain species richness and the single most important factor to explain community productivity, they both showed significant correlation. Mean annual temperature was introduced into model as the first factor to explain shannon-wiener index.(5) Productivity increased significantly with species diversity increasing in desert steppe, Inner Mongolia, and the relationship between productivity and species diversity was constrained by climatic factors and soil nutrients content.