Plant functional group removal alters root biomass and nutrient cycling in a typical steppe in Inner Mongolia, China

Loss of functional diversity has been demonstrated to have a variety of impacts on ecosystem functioning. However, most studies have been implemented in artificially assembled communities by removing the original vegetation and seeding with desired species or functional group compositions. Such approaches could significantly disturb belowground biomass, especially roots, making it difficult to examine belowground responses to diversity manipulations. To circumvent this issue, plant diversity gradients were established by in situ removal of aboveground biomass of different plant functional groups (PFGs) in a typical steppe, and belowground processes related to roots and soil were examined. Root nutrient pools exhibited contrasting patterns, with the phosphorus (P) pool decreasing linearly upon increased PFG removal while the nitrogen (N) pool had a hump-shaped response. Soil NO3- increased while net N mineralization decreased with PFG removal. In contrast, soil P showed little response to PFG removal. Furthermore, both the identity and number of PFG removed had a significant influence on root and soil properties. The results of this study showed that loss of a combination of PFGs was important in natural grassland, and an approach with minimal influence on belowground processes is promising in studying diversity loss effects in natural ecosystems.