Fine root production and turnover rate responses to long-term warming and nitrogen addition in a semi-arid grassland

Climate warming and nitrogen deposition will continue to increase in many parts of the world this century. Both temperature and nitrogen are key factors to regulate fine roots biomass and turnover. Plant roots could link above- and below-ground carbon processes, and contribute to soil carbon storage. However, the responses of fine roots to simultaneous warming and nitrogen addition, and subsequent changes in soil organic carbon component in dryland grasslands are still uncertain. Moreover, most existing field experiments on fine dynamics had short duration, we need long-term experiments to explore fine roots dynamics under future climate change.We conducted an 8-year field manipulative experiment in a semi-arid grassland on Loess Plateau of China to evaluate the responses of fine roots to increased temperature and nitrogen deposition. We found warming decreased fine roots production but increased fine roots turnover rate. Nitrogen addition increased fine roots production but had no effects on fine roots turnover rate. The interaction of two factors decreased fine roots turnover rate but had no effects on production. Our finding of the different responses of fine roots suggested that future climate change would have different effects on soil carbon cycle through altering fine roots traits.