Abstract
Global changes (precipitation changes and nutrient deposition) profoundly impact structure and function of steppe ecosystem. However, it is unclear the mechanism by which multiple limiting resources affect plant aboveground net primary productivity (ANPP) in desert steppe. We conducted a field experiment manipulating both precipitation (3 levels: ambient and ± 50% precipitation) and nutrients addition (3 levels: ambient; nitrogen (N) addition; N/phosphorus (P)/potassium (K) addition) in a factorial design. We focused on the effects of these treatments on species diversity (species richness, Shannon index, abundance), ANPP, plant functional traits, and soil properties. We used structural equation model (SEM) to evaluate the direct and indirect effects of precipitation amount and nutrient addition on ANPP through affecting species diversity and functional traits. Increasing precipitation increased species diversity and ANPP. NPK addition and increased 50% precipitation significantly increased ANPP over all other treatment combinations. Drought (-50%) reduced plant height and leaf dry matter content (LDMC), but increased leaf nitrogen content (LNC). Species richness, abundance, height and LDMC were positively correlated with ANPP, while specific leaf area (SLA) and LNC were negatively correlated with ANPP. SEM suggested that precipitation amount indirectly affected ANPP through its effect on abundance and SLA, while nutrient addition indirectly affected ANPP only through its effect on abundance. In desert steppe, the interaction of precipitation and nutrient addition had a significant positive effect on ANPP, which was mainly mediated by species diversity and functional traits. 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.
Highlights
Under the influence of human activities, global change has an appreciable impact on terrestrial ecosystems (Chen et al 2013; Hautier et al 2009; Zhang et al 2020)
Our results highlight the importance of species diversity and functional traits in driving short-term responses of affect plant community primary productivity (ANPP) to environmental factors in desert steppe ecosystems
The species diversity was only positively correlated with precipitation, while aboveground net primary production (ANPP) was affected by positively correlated with precipitation and nutrient addition (p < 0.05, Table S1, Fig. 1a-d)
Summary
Under the influence of human activities, global change has an appreciable impact on terrestrial ecosystems (Chen et al 2013; Hautier et al 2009; Zhang et al 2020). Increased precipitation causes soil erosion and organic matter loss, reducing productivity of steppe (Gao et al 2013). Further study is needed to explore the impact of precipitation changes on the productivity of grassland ecosystems. The restriction of other elements caused by nitrogen enrichment further counteracts the positive effect of nitrogen increase on plant growth (Wang et al 2018; Zhan et al 2019). Global changes profoundly impact on structure and function of grassland ecosystem. It remains unclear on the mechanism of how multiple limiting resources affect plant community primary productivity (ANPP) in desert steppe
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