Water table reduction shapes soil nematode communities in Zoige peatlands

The water table of the Zoige peatland has been reduced in recent decades due to climate change and human activities. However, as the biological indicators of soil environment, how the response of soil nematode communities to water table reduction was no clear. In this study, we conducted an in situ field sampling at low, intermediate, and high water table levels (ranging from −72 cm to −18 cm) in the Zoige peatland. The results showed that water table reduction increased the density of bacterivores and decreased the density of fungivores. Nematode diversity also decreased with water table reduction. The nematode channel ratio increased significantly after the water table reduction, indicating that the soil food web was transformed from a fungal-based channel (low decomposition efficiency) to a bacterial-based energy channel (high decomposition efficiency), especially in deep soil (with a maximum increase of 86 %). Structural equation modeling indicated that soil water table reduction had a negative effect on soil water content, thus increasing the abundance of fungivores, bacterivores and herbivores. Soil water table reduction had a positive effect on soil pH, thus increasing bacterivores, but decreasing fungivores. Our results provide substantial evidence for the degradation of Zoige peatland due to water table reduction caused by climate change and anthropogenic disturbance in the future. • Water table reduction increased the density of bacterivores and decreased the density of fungivores. • The nematode community transformed from K-selected species to r-selected species as the water table reduction. • Water table reduction led to bacterial-based decomposition pathway. • Soil water table reduction had a positive effect on soil pH.