Keystone microbial phylotypes support plant productivity along a gradient of degradation in alpine wetlands of Tibetan Plateau

Aims

Net primary productivity (NPP) is critical for understanding carbon sink and ecosystem functions, especially in alpine wetlands that degrade rapidly. Soil keystone taxa serve as ecosystem engineers and may influence aboveground NPP (ANPP), but this is poorly understood. Here, we analyzed the ANPP from 2012 to 2014 in alpine wetlands on the Qinghai-Tibetan Plateau to investigate the relationships between soil biodiversity of keystone phylotypes and ANPP.

Methods

The bacterial 16S rRNA gene was amplified using prokaryotic universal primers 515F and 907R, the archaeal 16S rRNA gene was amplified using primers Arch519F and Arch915R, and the eukaryotic 18S rRNA gene was amplified using primers Euk1391f and EukBr.

Results

Plant diversity was positively correlated with ANPP (R² = 0.25, P < 0.001). The diversity of soil archaea was positively correlated with ANPP (R² = 0.24, P < 0.001), with bacteria and eukaryotes showing no significant statistical relationships. The microbial network analysis revealed three major ecological clusters (Clusters 1–3) accounting for 98.8% of the constructed microbial co-occurrence networks. Diversity of Cluster 2 was more strongly positively correlated with ANPP than Cluster 1 and Cluster 3. Structural equation model analysis demonstrated that the contribution of plant diversity to ANPP was offset by soil biodiversity, especially coexisting phylotypes in ecological clusters.

Conclusions

Our results indicate that keystone phylotypes are associated with plant productivity, and highlight the need to conserve them to ensure the sustainable provision of alpine ecosystem services in fragile alpine ecosystems.