Background and Aims

Soil bacteria are essential in maintaining multiple grassland ecosystem functions that are significantly altered by mowing. Assembly processes govern bacterial community composition and in turn determine their functions. However, the ecological processes governing bacterial community assembly response to mowing remain largely unexplored.

Methods

In the present study, we characterized soil bacterial community assembly processes under different mowing intensities, including no mowing (CK), light mowing (LM, mowing annually with 8 cm stubble), moderate mowing (MM, mowing annually with 5 cm stubble), and heavy mowing (HM, mowing annually with 2 cm stubble) in typical grassland of Inner Mongolia. We further analyzed multiple environmental factors to explore the drivers of bacterial community assembly under different mowing intensities.

Results

Our results showed that stochastic processes primarily governed the bacterial community assembly in CK, LM, and HM; however, MM was governed by deterministic processes. Our research found that different mowing intensities did not visibly affect the bacterial α-diversity. However, MM and HM significantly altered the bacterial community's overall structure compared to the control. MM possessed the most complex and connective bacterial communities. Soil organic carbon (SOC) was the most critical environmental factor mediating the changes in bacterial community assembly processes induced by mowing. Increased SOC in MM worked as an ecological filter to deterministically select bacterial taxa (Streptomyces and RB41) with carbon metabolism-related function assembly.

Conclusions

Our findings showed that when the grass was mowed annually to a height of 5 cm, it increased the concentration of SOC and governed the deterministic assembly of bacterial communities in the semiarid grassland ecosystem. By studying these findings, we can better understand how bacterial communities support the long-term health of grassland ecosystems.