Effects of Astragalus sinicus manure and fertilizer combined application on biological properties of soil in Anhui double cropping rice areas along the Yangtze River Effects of nitrogen application on carbon metabolism of soil microbial communities in eucalyptus plantations with different levels of soil organic carbon Interactive effects of short-term nitrogen enrichment and simulated grazing on ecosystem respiration in an alpine meadow on the Tibetan Plateau Effects of temperature and moisture on soil nitrogen mineralization of lucerne stands