Direct and Indirect Effects of Precipitation Change and Nutrients Addition on Desert Steppe Productivity in Inner Mongolia, Northern China

Abstract

\n Background and Aims Global changes profoundly impact on structure and function of grassland ecosystem. However, it remains unclear on the mechanism of how multiple limiting resources affect plant community primary productivity (ANPP) in desert steppe.Methods Here, we conducted an experiment to examine the effects of precipitation changes (natural and ± 50% precipitation) and nutrient addition (=N: 0 g·m-2·yr-1; +N: N 10 g·m-2·yr-1; +NPK: N/P/K each for 10 g·m-2·yr-1) on species diversity, ANPP, functional traits and soil properties. We used structural equation model (SEM) to evaluate the effects of precipitation changes and nutrient addition on ANPP.Results Increased precipitation increased species diversity and ANPP under NPK addition, NPK addition increased ANPP under increased precipitation, and the interaction of precipitation changes and nutrient addition was significant for ANPP. Drought reduced plant height and leaf dry matter content (LDMC), but increased leaf nitrogen content (LNC). ANPP was positively correlated with species richness, abundance, height and LDMC, but negatively correlated with specific leaf area (SLA) and LNC. The SEM showed increased precipitation and nutrient addition directly increased ANPP. Altered precipitation indirectly affected ANPP through its effect on abundance and SLA, while nutrient addition indirectly affected ANPP only through its effect on abundance.Conclusion The combined limitations of precipitation and multiple nutrients deserves more attention in studying the effect of global changes on productivity in arid steppe. Our results highlight the importance of species diversity and functional traits in driving short-term responses of ANPP to environmental factors in desert steppe ecosystems.