Processes at the soil-root interface determine the different responses of nutrient limitation and metal toxicity in forbs and grasses to nitrogen enrichment

Nutrient limitation and metal toxicity have been implicated in changes of grassland communities by nitrogen (N) deposition. Belowground processes, especially those at the soil-root interface, play important roles in determining variation in nutrient concentrations in plants. However, few studies have specifically focused on the roles of these processes in mineral-element acquisition in grassland plants in response to N enrichment. Here we investigated the contributions of belowground processes at the soil-root interface to the differential acquisition of phosphorus (P), calcium (Ca) and manganese (Mn) by forbs and grasses of a temperate steppe in response to N addition by combining field and glasshouse experiments. Nitrogen addition increased the concentrations of both leaf P ([P]) and Mn ([Mn]) and decreased leaf [Ca] of forbs, while it had little effects on leaf concentrations of these elements in grasses. Nitrogen addition led to a higher activity of acid phosphatase in the rh...