Long-term removal of root carbon inputs has a great negative impact on grassland soil bacterial diversity, network stability and carbon and nitrogen cycling function

Human activity and climate change have significantly altered the above and belowground distribution of plant carbon (C). However, the effects of plant root and litter inputs on soil microbial community and their mediated C and nitrogen (N) cycling functions remain unclear. Therefore, we conducted a 10-year (2012-2022) field manipulative experiment. Here, pyrosequencing and FAPROTAX dataset were applied to assess the effects of plants removal, litter addition, and litter removal on soil bacterial community structure, diversity, network stability, and C and N metabolic functional annotations in a semiarid grassland. We found that plants removal significantly changed the relative abundance of almost all phyla, such as Proteobacteria and Bacteroidetes. In addition, plants removal decreased bacterial alpha diversity, the network complexity and stability, and inhibited microbial respiration and most C and N metabolic functions by reducing substrate content. Litter addition enhanced bacterial alpha diversity, network complexity and stability, and promoted ureolysis process, etc. In contrast, litter removal had little impact on the bacterial community, diversity, and network complexity and stability. This study indicates root C inputs have a more significant impact than litter in shaping grassland soil bacterial community and function. The finding highlights that maintaining root C inputs should be central to grasslands management strategies. This means prioritizing vegetation protection to ensure continuous root exudation, thereby optimizing soil microbial function and promoting grassland health under the scenarios of global change.In document, the treatment representing the control group is C4, C12, C17, C23, C30 ,C34. The treatment representing litter addition group is C1, C8, C14, C19, C27, C33. The treatment representing litter removal group is C2, C7, C15, C21, C25, C32. The treatment representing plants removal group is C3, C9, C13, C20, C26, C31. The treatment representing plants removal plus litter addition group is C6, C10, C16, C24, C29, C35. The treatment representing plants removal plus litter removal group is C5, C11, C18, C22, C28, C36.