Factors affecting lucerne-rich vegetation under revegetation in a semi-arid environment

Abstract

Understanding the factors contributing to spatial variation in the functional structure of plant is crucial for revegetation and ecosystem management of the Loess Plateau, China. As one of the measures in the “Grain for Green” project, lucerne (Medicago sativa L.) has been widely planted in this seriously-eroded region to improve revegetation and conserve soil and water. However, information on how environmental factors influence the long-term development of lucerne-rich vegetation is scarce. This study aimed to identify the main environmental variables controlling the lucerne-rich vegetation through multivariate analyses. Vegetation and soil surveys were performed in 28 fields containing 11-year-old lucerne. Vegetation variables were total aboveground biomass, aboveground biomass of lucerne, total cover, lucerne cover, total abundance, species richness, Shannon–Wiener’s diversity index, Simpson’s predominance index, and evenness index. Topographic variables were slope, slope position, and slope aspect. Soil variables were soil total nitrogen (N) and phosphorus (P), available P, mineral N, organic carbon (SOC), moisture content (SMC), microbial biomass C and N. Analyses verified that vegetation variables, soil variables, and topographic variables were significantly correlated. One of the most important factors that influence lucerne revegetation process was SOC. SMC, total P, slope, and mineral N were also key factors that influenced vegetation variables. The obtained values of total aboveground biomass and cover were still high after 11 years planting. The fields that in the north– and south–facing slopes did not significantly differ in terms of total cover, and total and lucerne aboveground biomass. The results suggest that soil properties (such as SOC, TN, and mineral N, etc.) and topographic variables (i.e., slope) interacted with each other and acted on plants simultaneously in the lucerne-rich vegetation. To revegetation the degraded ecosystems by lucerne planting, we should consider the effects of the changes of soil properties, such as SOC, SMC, and soil P, on vegetation development.