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Below-ground-mediated and phase-dependent processes drive nitrogen-evoked community changes in grasslands

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*
影响因子: 5.687
刊物名称: Journal of Ecology
出版年份: 2020
卷:   期:    页码: DOI: 10.1111/1365-2745.13415

文章摘要 : 

  1. 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 timescales of responses for the different functional groups remain unclear.
  2. We investigated the temporal responses of plant community in a temperate steppe to N enrichment by linking aboveground to belowground processes using a series of field Naddition and greenhouse experiments.
  3. The N enrichmentinduced declines in plant diversity of grasslands were phasebased, functional groupdependent and driven by three belowground processes. The rapid accumulation of NH4 +-N by N addition inhibited photosynthetic rates of broadleaf nonrhizomatous forbs, contributing to loss of these Nsensitive species during early phase of N enrichment (≤3 years). The Ninduced changes in this phase were independent of soil pH as evidenced by results from application of lime to mitigate Nevoked soil acidification. With progression of N addition, manganese (Mn) toxicity to narrowleaf nonrhizomatous forbs due to soil acidificationinduced 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 belowground 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.
  4. Synthesis . The hierarchical mechanisms not only provide a comprehensive explanation for the N enrichmentinduced 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.

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