Rhizosphere soil microbial activity under different vegetation types on the Loess Plateau, China

Severe soil and water loss has led to widespread land degradation of the Loess Plateau, China. During the past two decades, significant efforts have been made to revegetate degraded soil in the region. However, a better understanding of the ability of plants to promote soil microbial processes is important for successful revegetation. The current study was conducted at the Dunshan watershed on the Loess Plateau, with the aim of evaluating the effect of different vegetation types on the microbial properties of rhizosphere soil. Six vegetation types were evaluated: two natural grassland (Artemisia capillaries and Heteropappus altaicus), two artificial (i.e. planted by humans) grassland (Astragalus adsurgens and Panicum virgatum) and two artificial shrubland (Caragana korshinskii and Hippophae rhamnoides) species; an area without vegetation cover was used as a control. The results indicated that the highest values of soil organic C, total nitrogen (TN), microbial biomass carbon (MBC), MBN, saccharase, urease, catalase and peroxidase were recorded for H. altaicus and A. capillaries; of basal respiration (BR), the MBN: TN ratio, alkaline phosphatase and polyphenol oxidase for A. adsurgens; and of the BR: MBC ratio for P. virgatum. A rhizosphere soil microbial index (RSMI) was obtained using principal component analysis, and metabolic quotient (BR/MBC), BR, urease, water-soluble C and cellulase were found to be most important for assessing rhizosphere soil quality. All revegetated soil showed higher RSMI compared with control soil, with soil under natural grassland species (H. altaicus and A. capillaries) recording the highest value. It was concluded that plant species under arid climatic conditions have different effects on the microbial properties of rhizosphere soil owing to their different root exudates and plant debris. In addition, natural grasslands are most effective for revegetation of the Loess Plateau. (C) 2010 Elsevier B.V. All rights reserved.