Responses of surface soil carbon and nutrients to re-vegetation of an eroded hillslope in southwest China

Abstract

Chinese national re-vegetation on the eroded hilly landscapes may have potential to modify the surface soil carbon (C), nitrogen (N) and phosphorus (P) pools. However, few studies have investigated this relationship. We quantified differences in soil organic carbon (SOC), soil available nitrogen (AN), available phosphorus (AP), and soil bulk density (BD) of the surface soil (0 to 10 cm) among different types of vegetation cover (VC) and slope positions on a re-vegetated hillslope that was previously used as farmland at Xichang, Southwestern China. The four different VC types examined in this study were: a) tree, b) shrub, c) grass and d) bare soil. SOC, AN and AP under vegetation cover, whether tree, shrub, or grass, were higher than that in the bare soil. SOC, AN and AP were highest under shrub and grass followed by tree cover. SOC stock under tree, shrub and grass cover were respectively 1.76, 3.50 and 3.71 times the stock in bare soil, whereas AN concentration was 1.02, 2.60, and 1.39 times the concentration in bare soil. Moreover, AP concentration in soils under tree, shrub and grass cover was 3.91, 5.48 and 6.69 times the concentration in bare soil, respectively. Soil bulk density under shrub and tree cover was slightly lower (11 and 6%, respectively) than that in the bare soil, but not for the soil under grass cover. The relationship between surface SOC, AN, BD and vegetation cover types is irrespective of hillslope positions (excepting a significant higher AP concentration at the lower slope than the top of the hillslope), suggesting a link to re-vegetation. Our results therefore indicate that re-vegetation, specifically with shrubs and grasses, could contribute to ecological restoration of eroded hillslope through modifying surface SOC and nutrients, and hence improving soil quality in southwest China. Key words: Re-vegetation, soil organic carbon, soil nutrients, soil bulk density, eroded hillslope