Leaf- and root-associated bacterial communities differ in their resistance and resilience to N disturbance in a...

Enhanced deposition of nitrogen (N) has great impacts on grassland ecosystems. A decline in N deposition has occurred in many regions across the globe. Changes in N deposition alter the structure and functions of grassland ecosystems and bacterial community of soil and rhizosphere. However, the responses of plant microbiomes to N deposition and cessation of N input in terms of resistance and resilience have not been systematically evaluated. We examined the effects of N addition and cessation of N addition on leaf- and root-associated bacterial communities through a consecutive N addition and cessation of N addition experiment in a temperate grassland. We found that leaf-associated bacterial community exhibited lower resistance to N enrichment than root-associated bacterial community, which was mainly steered by leaf soluble sugars and leaf morphology via regulating functional taxa. In contrast, the root-associated bacterial community showed stronger resilience to cessation of N addition than leaf-associated bacterial community, which may be explained by the high N accumulation in roots and root morphology via regulating functional taxa. The greater resistance and resilience in the root-associated bacterial community may be attributed to the presence of host-related factors. Additionally, N enrichment-induced suppression of beneficial symbiotic microbes associated with the N cycle in the leaf-associated bacterial community was not readily recovered after cessation of N input. Conversely, microbes involved in carbon cycle and ecological restoration in the root-associated bacterial community showed a quick recovery after cessation of N enrichment. Our results offer valuable insights into the mechanisms by which changes in N input influence the plant microbial community.IMPORTANCEAs an integral component of ecosystems, the plant microbiome plays an important role in the response of grassland ecosystems to enhanced N deposition. Changes in N deposition influence bacterial communities of soil and rhizosphere of grassland ecosystems. However, whether and how the N deposition and cessation of N input impact microbiomes of plant species of temperate grasslands remain unexplored. Based on a long-term N-addition experiment in a temperate steppe, we discover that leaf- and root-associated bacterial communities respond differently to N addition and subsequent cessation of N addition. The leaf-associated bacterial community exhibits lower resistance to N enrichment than the root-associated bacterial community due to the unique environment of the phyllosphere, whereas the root-associated bacterial community shows stronger resilience to cessation of N addition than the leaf-associated bacterial community due mainly to the higher root N accumulation and morphology. These findings offer valuable insights into the impact and mechanism of N interference on the plant microbial community.