水氮添加条件下高寒草甸主要植物种氮素吸收分配的同位素示踪研究

Nitrogen uptake and allocation characteristics of alpine meadow main species under water and nitrogen additions based on ^(15)N isotope

资源利用方式的分化可以减小物种间对相同资源的竞争,是群落物种多样性维持的主要机制。在全球变化背景下,土壤温度和水分条件的变化可能影响高寒草甸生态系统植物的氮素(N)营养。该实验在经N、水处理3年的高寒草甸开展,通过15NH415NO3的15N稳定性同位素注射,比较高寒草甸主要植物种对N、水处理的响应方式,以及N吸收能力、分配和根冠比特点,研究其营养吸收和资源分配方式的分化。结果发现不同植物种对N、水处理响应差异显著,N吸收能力、根N含量和根冠比等功能性状种间差异显著;回归分析发现植物种N吸收能力和根N含量之间的关系不显著,和根冠比之间呈显著线性负相关。说明高寒草甸生态系统不同植物种间N吸收具有生态位分化,并且存在N营养吸收能力和资源分配策略的权衡。

Aims Resource-use differentiation among species, which can reduce species competition for the same resources, is the main mechanism to maintain species diversity. Changes in soil temperature and moisture conditions, in the context of global change, may affect nitrogen （N） nutrition of plants of alpine meadow ecosystems. Our objective is to compare the characteristics of N uptake and resource allocation of dominant species of alpine meadow with changes in soil N and water. Methods An alpine meadow was treated with N and water addition for three years using the method of 15N iso- tope injection. We determined the growth responses of dominant species to the N and water additions, as well as the features of N uptake capacity, N allocation and root to shoot ratio. Important findings The species showed significantly different responses to the N and water treatments, with respect to functional traits of species in N absorption capacity, root N content and root to shoot ratio. There was no significant relationship between N absorption capacity and root N content, whereas N absorption capacity was negatively correlated with root to shoot ratio across all plant species. These results indicated there was ecological niche differentiation in N uptake and a trade-off between the N absorption capacity and resource allocation strate- gies among species.