Effects of enclosure on species diversity and soil organic matter of typical steppe

Abstract： The species diversity and soil organic content of typical steppe with different enclosure years in Yunwushan nature reserve of Ningxia were studied. The results showed that：as enclosure years increasing, species richness and diversity index increased first and then decreased, but for evenness index, an opposite trends was observed. Soil organic matter showed a significant difference among different enclosure years in which enclosed 15 years and 25 years attained the highest soil organic matter, followed by enclosed 5 and 20 years, and the lowest appeared in the steppe without enclosure.Soil organic matter content was negatively correlated with species diversity, but positively correlated with evenness index.