Short Term Effects of Revegetation on Labile Carbon and Available Nutrients of Sodic Soils in Northeast China

In response to land degradation and the decline of farmers’ income, some low quality croplands were converted to forage or grassland in Northeast China. However, it is unclear how such land use conversions influence soil nutrients. The primary objective of this study was to investigate the influences of short term conversion of cropland to alfalfa forage, monoculture Leymus chinensis grassland, monoculture Leymus chinensis grassland for hay, and successional regrowth grassland on the labile carbon and available nutrients of saline sodic soils in northeastern China. Soil labile oxidizable carbon and three soil available nutrients (available nitrogen, available phosphorus, and available potassium) were determined at the 0–50 cm depth in the five land uses. Results showed that the treatments of alfalfa forage, monoculture grassland, monoculture grassland for hay, and successional regrowth grassland increased the soil labile oxidizable carbon contents (by 32%, 28%, 15%, and 32%, respectively) and decreased the available nitrogen contents (by 15%, 19%, 34%, and 27%, respectively) in the 0–50 cm depth compared with cropland, while the differences in the contents of available phosphorus and available potassium were less pronounced. No significant differences in stratification ratios of soil labile carbon and available nutrients, the geometric means of soil labile carbon and available nutrients, and the sum scores of soil labile carbon and available nutrients were observed among the five land use treatments except the stratification ratio of 0–10/20–30 cm for available phosphorus and the values of the sum scores of soil labile carbon and available nutrients in the 0–10 cm depth. These findings suggest that short term conversions of cropland to revegetation have limited influences on the soil labile carbon and available nutrients of sodic soils in northeastern China.