Divergent responses of microbial metabolic limitations to cropland revegetation at erosion and deposition topographies in the hilly-gully region of the northern Loess Plateau, China

Abstract

Aims Cropland revegetation is an effective measure to curb soil erosion on eroding hillslopes and increase farmers’ income at depositional check dams. However, how soil microbial metabolic limitation responds to cropland revegetation in erosion and deposition landscapes remains poorly understood, which has substantial implications for carbon (C) retention and nutrient cycling in the eroding environment. Methods We sampled 0-2 m soils in cropland and revegetated forest and grassland at upslopes and check dams on the hilly-gully region of the Loess Plateau, China. The activities of soil C-, nitrogen (N)-, and phosphorus (P)-acquiring enzymes were analyzed, and the improved V-T model derived from the vector model with the balance point was used to quantify microbial metabolic limitations based on ecoenzymatic stoichiometry. Results Microorganisms suffered from no energy (C) limitation, but the relative microbial C limitation was greater in revegetated land than in cropland in both landscapes. At upslopes, microbial P limitation occurred in the revegetated forest in soils below 20 cm due to the assimilation of P by the root system, while microorganisms were mainly limited by N in cropland and revegetated grassland. At check dams, land-use change had no significant influence on microbial N/P limitations owing to abundant soil C and nutrients and a wet environment. Conclusions Concludingly, this study revealed a non-response phenomenon of cropland revegetation on microbial metabolic limitation at lower-lying depositional topography, which compensates for the current understanding of resource restrictions on microorganisms at slopes or flat areas.