Decoupled responses of above- and below-ground beta-diversity to nitrogen enrichment in a typical steppe

Increased atmospheric nitrogen (N) deposition affects biodiversity in terrestrial ecosystems. However, we do not know whether the effects of N on above-ground plant β-diversity are coupled with changes occurring in the soil seed bank. We conducted a long-term N-addition experiment in a typical steppe and found that above-ground β-diversity increased and then decreased with increasing N addition, whereas below-ground β-diversity decreased linearly. This suggests decoupled dynamics of plant communities and their soil seed bank under N enrichment. Species substitution determined above- and below-ground β-diversity change via an increasing role of deterministic processes with N addition. These effects were mostly driven by differential responses of the above-ground vegetation and the soil seed bank β-diversities to N-induced changes in environmental heterogeneity, increased soil inorganic N concentrations and soil acidification. Our findings highlight the importance of considering above- and below-ground processes simultaneously for effectively conserving grassland ecosystems under N enrichment.

Methods
Usage notes
These datasets were collected in the field experiment in a steppe grassland in Xilinhot, Inner Mongolia Autonomous Region, China (2019–2020).

Details for each dataset are provided in the README file.

Datasets included:
1) The distance matrix data for pairwise between 10 replicates plots under different treatment

        * Beta diversity, beta deviation and the two components of beta diversity  in above-ground vegetation and soil seed bank
        * The normalised stochasticity ratio  in above-ground vegetation and soil seed bank and soil environmental heterogeneity

2) Soil physical and chemical properties and  abundance and proportation of grasses

       * Six indexes of soil physical and chemical properties (90 plots of 2019-2020)
       * The proportion of grasses to total above-ground vegetation species richness  (90 plots of 2019-2020)
       * The proportion of Leymus chinensis abundance  (90 plots of 2019-2020)

3) A aggregated version of all raw data used to make the figures

Additional details are available in the README file.