Plant functional groups regulate soil respiration responses to nitrogen addition and mowing over a decade

1. Nitrogen (N) deposition and land-use practice (e.g. mowing) could have profound effects on soil respiration. However, the changes in other ecosystem components, such as plant functional groups (PFGs), may control soil carbon (C) efflux response to long term global change. 2. A 10-year (2005-2014) field experiment was conducted with both N addition (10g Nm(-2)year(-1)) and mowing (once a year) in a northern Chinese temperate grassland. We collected continuous data on soil respiration over 10years accompanied with data on abiotic and biotic factors, and attempted to determine (i) the temporal variation in soil respiration and its responses to N addition and mowing, (ii) the regulation of soil respiration by PFGs and the underlying long-term mechanisms of control. 3. Soil respiration varied significantly among years. This was mainly caused by changes in precipitation pattern (e.g. frequency and distribution) during the growing-season rather than total rainfall. N addition significantly suppressed soil respiration by 10.4% whereas mowing stimulated it by 8.4% over the 10years. The interaction of N addition with mowing had little effect on soil respiration. However, the significant effects of both N addition and mowing appeared only in the third year and thereafter, indicating the differences between long- and short-term responses. These long-term effects of N addition and mowing were mainly caused by changes in the PFGs of covers (e.g. grasses and forbs) and in soil pH rather than in soil microclimate. Forb-dominant patches had greater soil respiration than grass patches owing to their higher litter quality and photosynthetic capacity. 4. Our results highlight that shifts in above-ground plant community could play an important role in regulating soil respiration responses to N addition and mowing in the long-term. This is potentially important for improving our understanding of the link between above- and below-ground ecological processes.