Effects of vegetation restoration types on soil quality in Yuanmou dry-hot valley, China

Soil erosion has resulted in serious land degradation in Yuanmou dry-hot valley, Yunnan province, China. Vegetation restoration had been widely developed in this hot and arid area. In this work we investigate the quality of rhizosphere soils under four restoration species in the towns of Zuolin (gully bed) and Yuanma (slope area). The vegetation included two trees [ Leucaena leucocephala (Lam.) de Wit. and Eucalyptus camaldulensis L.] for the slope area, one shrubland [ Dodonaea viscosa (Linn.) Jacq. Enum.] and one native, natural grassland [ Heteropogon contortus (L.) Beauv.] for gully bed. Soil physical (bulk density and soil moisture content), chemical [pH, soil organic matter, nitrogen (N), phosphorus (P) and potassium (K) contents], and microbial (microbial biomass and microbe quantity) properties and soil enzyme (catalase, protease and urease) activities were determined. Compared to the soils collected from other vegetation types, the soil under Leucaena leucocephala had the highest content of soil organic matter, total N, available N, total P, available P, available K, microbial biomass carbon (C), and the highest microbe quantity and enzyme activities. Five parameters (organic matter, pH, microbial biomass N, total K and protease activity), which had the greatest weight in the principal components analysis, were selected to calculate the soil quality index (SQI). The final SQI values implied that restoring Leucaena leucocephala greatly improved the soil quality, while restoration with Eucalyptus camaldulensis decreased the soil quality of the slope area. Plant recovery with Dodonaea viscosa and Heteropogon contortus on the gully bed affected the population of soil microbial communities but didn't improve the SQI values. It can therefore be seen that types of plants used for recovery in gully-developed regions in dry-hot valleys must be chosen cautiously: Leucaena leucocephala is a good choice for soil revegetation of the slope area, but the revegetation patterns on the gully bed still need further study.