作 者：Tian QY, Yang LY, Ma PF, Zhou HR, Liu NN, Bai WM, Wang H, Ren LF, Lu P, Hanl WW, Schultz PA, Bever JD, Zhang FS, Lambers H, Zhang WH*
刊物名称: Journal of Ecology
卷: 期: 页码: DOI: 10.1111/1365-2745.13415
- Enhanced deposition of atmospheric nitrogen (N) leads to loss of plant diversity in grassland ecosystems. Numerous theories have provided potential explanations for the negative effects of N enrichment on plant diversity. However, the relative importance of each mechanism and the time‐scales of responses for the different functional groups remain unclear.
- We investigated the temporal responses of plant community in a temperate steppe to N enrichment by linking above‐ground to below‐ground processes using a series of field N‐addition and greenhouse experiments.
- The N enrichment‐induced declines in plant diversity of grasslands were phase‐based, functional group‐dependent and driven by three below‐ground processes. The rapid accumulation of NH4 +-N by N addition inhibited photosynthetic rates of broad‐leaf non‐rhizomatous forbs, contributing to loss of these N‐sensitive species during early phase of N enrichment (≤3 years). The N‐induced changes in this phase were independent of soil pH as evidenced by results from application of lime to mitigate N‐evoked soil acidification. With progression of N addition, manganese (Mn) toxicity to narrow‐leaf non‐rhizomatous forbs due to soil acidification‐induced Mn2+ mobilization in soil accounted for their loss in the second phase of N enrichment (~4–9 years). When N addition proceeded longer than ~10 years, N enrichment stimulated below‐ground meristem differentiation and rhizome growth of the rhizomatous species, leading to the dominance by rhizomatous sedges/grasses in the community at the later phase of N enrichment.
- Synthesis . The hierarchical mechanisms not only provide a comprehensive explanation for the N enrichment‐induced diversity decline in grasslands, but can also facilitate us to understand the differential sensitivities of ecosystems to chronic N enrichment, and predict future ecosystem dynamics.