Labile and Recalcitrant Organic Matter and Microbial Communities in Soil After Conversion of Abandoned Lands in the Loess Plateau, China

To control serious soil erosion in the Loess Plateau of China, many areas are subjected to afforestation and subsequent shifts in the pool of soil organic matter. In this study, we investigated changes of labile and recalcitrant carbon (C) and nitrogen (N) pools, inorganic N, and microbial populations in environments of 5-year abandoned land, Hippophae rhamnoides shrubs, Larix principis-rupprechtii plantation, and a naturally regenerated forest. Soil general physicochemical and microbial characteristics were improved significantly in 30-year restoration compared with 5-year abandoned land. At the soil surface, the highest levels of C, N, and microbes were observed in mixed forest and the lowest on abandoned land in most conditions. Vegetation types, soil depth, and sampling date as well as their interaction produced significant influences on soil properties. Soil characteristics tested in this study indicated that the natural regeneration of forests may be a better restoration method than pure shrub and tree plantations.