氮添加对宁夏荒漠草原植物初级生产力的影响机制

许多研究探索了与全球变化相关的生态系统功能的变化，但对生态系统功能变化的机制与途径了解较少。初级生产力是生态系统功能的重要组分，但关于氮(N)添加下荒漠草原植物群落初级生产力如何变化以及变化机制尚未明确，N是否通过影响生物多样性来影响荒漠草原初级生产力?为此，本研究在荒漠草原开展了为期4年的N添加控制实验(2018—2021年),试验处理包括对照和4个N添加水平(5、10、20和40 g m^-2 a^-1),研究了N添加对荒漠草原物种多样性、功能多样性、初级生产力及其关系的影响。结果表明：(1)N添加处理(2018—2021年)改变了植物物种多样性及功能多样性，但年际间变化趋势不同。N添加处理第四年(2021年)荒漠草原植物功能多样性(Rao指数)、群落加权平均值-株高、功能均匀度和功能离散度均显著增加，而荒漠草原植物物种丰富度和Shannon-Wiener指数均显著降低。(2)N添加可以通过影响物种丰富度和功能多样性进而间接地促进荒漠草原初级生产力，但群落加权性状值-株高对初级生产力的影响是正效应，而物种丰富度和功能离散度对初级生产力的影响是...

Effects and mechanism of nitrogen addition on primary productivity in a desert grassland of Ningxia, China

Many studies have explored changes in ecosystem functions related to global environmental changes, but little is known about the mechanisms and pathways behind the changes. Productivity is an important component of ecosystem functions. However, it is not clear how change and the mechanism of change of the primary productivity of desert grassland plant communities under nitrogen (N) addition; does N affect the productivity of desert grassland by affecting biodiversity? A manipulative N addition experiment located in the desert grassland has been conducted since 2018. The experimental treatment included five levels of N addition rate (i.e., control, 5, 10, 20 and 40 g m^-2 a^-1) with four replicates for each treatment. The plant functional traits, species richness and composition, and aboveground productivity were determined. In addition, species diversity, functional diversity and community weighted average traits were calculated. The results showed that: (1) the functional diversity (Rao index), community weighted average-height (CWM-height), functional evenness and functional dispersion of the desert grassland increased significantly in the fourth year of N addition treatment (2021), while the species richness and Shannon-Wiener index of the desert grassland decreased significantly. (2) N addition could indirectly promote the primary productivity of desert grassland by affecting species richness and functional diversity, but the impact of CWM-height on the primary productivity was a positive effect, while species richness and functional dispersion had a negative effect on productivity. (3) The biomass ratio hypothesis could better explain the variation of the primary productivity of desert grassland communities. Our results indicated that N addition regulated the primary productivity of desert grassland mainly by altering the functional traits of dominant species within the community.