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Journal of Desert Research ›› 2025, Vol. 45 ›› Issue (4): 96-108.DOI: 10.7522/j.issn.1000-694X.2025.00197

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Effects of soil nitrogen content and rainfall on vegetation productivity in semi-arid sandy grassland

Jing Zhang(), Xiaoan Zuo(), Peng Lv   

  1. State Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China
  • Received:2025-05-23 Revised:2025-07-10 Online:2025-07-20 Published:2025-08-18
  • Contact: Xiaoan Zuo

Abstract:

Rainfall variation and nitrogen addition significantly influenced the structure and function of grassland ecosystems in semi-arid regions. To elucidate their effects on vegetation community characteristics, soil physicochemical properties, and the regulatory mechanisms underlying biomass formation, a field-controlled experiment was conducted in the sandy grassland of the Horqin Sandy Land during 2021 and 2022. Four rainfall treatments were applied during the growing season (May to September): a 60% reduction (-60%) and a 60% increase (+60%) in precipitation. To further assess the effects of early-season extreme drought, two additional treatments were established: a 100% reduction for 60 days (-60d) and a 100% increase for 60 days (+60d) from May to June. A nitrogen addition treatment (20 g·m-2 per year) was also included. The results revealed that changes in precipitation and nitrogen addition had significant but temporally inconsistent impacts on community structure, biodiversity indices, and soil physicochemical attributes. Rainfall reduction notably decreased vegetation cover and increased species density. Among the drought treatments, early-season extreme drought (-60d) imposed a stronger suppressive effect on aboveground biomass than whole-season rainfall reduction (-60%). Nitrogen addition significantly enhanced vegetation cover and both above- and belowground biomass. However, it also reduced species richness, intensified interspecific competition, and facilitated the dominance of competitive species, resulting in decreased community diversity, lower evenness, and increased dominance. With respect to soil responses, nitrogen addition induced soil acidification, leading to a reduction in clay particle content. Under drought conditions, species with drought-tolerant or drought-avoiding traits and larger individuals became dominant, thereby enhancing community biomass. Nitrogen addition further promoted biomass accumulation by increasing vegetation cover and plant height. Overall, rainfall variability and nitrogen enrichment jointly reshaped vegetation structure, altered resource competition dynamics, and modified soil physicochemical processes, thereby exerting profound effects on the biomass formation mechanisms in semi-arid sandy grasslands.

Key words: semi-arid sandy grassland, rainfall variability, nitrogen addition, biomass

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