Difference of different treatment on aboveground biomass of plant functional groups.

<p>Aboveground biomass for each treatment was the average of four replicates (error bars denote SEM), and <i>P</i> (N*P) indicates the interaction between N and P addition.</p

Soil properties (means ±SEM) of site I and site II before treatment.

<p>Soil properties (means ±SEM) of site I and site II before treatment.</p

Difference of N&P rate on aboveground biomass of plant functional groups (error bars denote SEM).

<p>Aboveground biomass for each plant functional group of each addition rate was the average of sixteen replicates of the four treatments for N addition, and twelve replicates of three treatments for P addition. Bars with the same letter were not significantly different in Duncan’s multiple range tests reported from ANOVA (<i>P</i> > 0.05). For both site, regression parameters were estimated aboveground biomass using linear model with N or P treatment as a continuous preditor, i.e. Aboveground biomass = Intercept + Slope ×addition rate (N or P). Significant differences are reported as ^*, <i>P</i> < 0.05; ^**, <i>P</i> < 0.01.</p

Multiple linear regression between TB and properities of soil.

<p>Multiple linear regression between TB and properities of soil.</p

Ratio of Gramineae to Compositae (error bars denote SEM).

<p>Medium pattern with grey back indicates the ratio of different N level, and the only grey back indicates the ratio of different P level.</p

The significant of different sites, N and P to functional groups.

<p>The significant of different sites, N and P to functional groups.</p

The physical and chemical properties of soil in site I (error bars indicate SEM).

<p>SOM as soil organic matter, AP as available phosphorus, AK as available kalium.</p

Data_Sheet_1_Soil diazotrophic abundance, diversity, and community assembly mechanisms significantly differ between glacier riparian wetlands and their adjacent alpine meadows.PDF

Global warming can trigger dramatic glacier area shrinkage and change the flux of glacial runoff, leading to the expansion and subsequent retreat of riparian wetlands. This elicits the interconversion of riparian wetlands and their adjacent ecosystems (e.g., alpine meadows), probably significantly impacting ecosystem nitrogen input by changing soil diazotrophic communities. However, the soil diazotrophic community differences between glacial riparian wetlands and their adjacent ecosystems remain largely unexplored. Here, soils were collected from riparian wetlands and their adjacent alpine meadows at six locations from glacier foreland to lake mouth along a typical Tibetan glacial river in the Namtso watershed. The abundance and diversity of soil diazotrophs were determined by real-time PCR and amplicon sequencing based on nifH gene. The soil diazotrophic community assembly mechanisms were analyzed via iCAMP, a recently developed null model-based method. The results showed that compared with the riparian wetlands, the abundance and diversity of the diazotrophs in the alpine meadow soils significantly decreased. The soil diazotrophic community profiles also significantly differed between the riparian wetlands and alpine meadows. For example, compared with the alpine meadows, the relative abundance of chemoheterotrophic and sulfate-respiration diazotrophs was significantly higher in the riparian wetland soils. In contrast, the diazotrophs related to ureolysis, photoautotrophy, and denitrification were significantly enriched in the alpine meadow soils. The iCAMP analysis showed that the assembly of soil diazotrophic community was mainly controlled by drift and dispersal limitation. Compared with the riparian wetlands, the assembly of the alpine meadow soil diazotrophic community was more affected by dispersal limitation and homogeneous selection. These findings suggest that the conversion of riparian wetlands and alpine meadows can significantly alter soil diazotrophic community and probably the ecosystem nitrogen input mechanisms, highlighting the enormous effects of climate change on alpine ecosystems.</p