Abstract: Vegetation restoration following Spartina alterniflora removal is critical for restoring ecological functions in coastal wetlands. However, how different restoration patterns influence soil bacterial communities remains insufficiently understood. In this study, we investigated restored wetlands in the Minjiang River Estuary, southeastern China, including salt marshes dominated by Phragmites australis and Cyperus malaccensis, and Kandelia obovata mangroves of two stand ages (6- and 16-year-old), with unrestored wetlands as control. We used high-throughput sequencing to characterize soil bacterial communities and used structural equation modelling (SEM) to identify the key drivers. The results showed that: 1) Vegetation restoration significantly decreased soil pH relative to the unrestored wetland, but without significant differences among the restoration patterns. Soil total carbon (TC) and total nitrogen (TN) contents showed consistent patterns across restoration patterns, followed the order of C. malaccensis > P. australis ≈ old-growth mangrove (16-year-old) > unrestored wetland > young mangrove (6-year-old). C. malaccensis marsh had significantly higher TC and TN than the unrestored wetland. 2) Vegetation restoration generally enhanced soil bacterial richness and diversity. The number of observed species and the Simpson and Shannon indices differed significantly among treatments, whereas the Chao1 index showed no variation. The observed species richness and Simpson and Shannon indices generally followed the order of old-growth mangrove > young mangrove > P. australis > C. malaccensis > unrestored wetland. Desulfotomaculum was the dominant bacterial genus across all restoration types, with a relative abundance of 9.4%-13.9%. The dominant genera in the unrestored wetland included Alkaliimnicola, Desulfotomaculum, Myxococcus, Pseudomonas, and Thioalkalivibrio, with relative abundances of 7.2%, 9.4%, 5.6%, 7.5%, and 5.3%, respectively. Following vegetation restoration, the relative abundances of Desulfotomaculum and Myxococcus increased by 2.5%-4.5% and 2.6%-4.6%, respectively, whereas those of Alkaliimnicola and Pseudomonas decreased by 3.6%-4.6% and 3.0%-5.5%, respectively. In addition, Thioalkalivibrio and Pseudomonas were more abundant in mangrove wetlands than in salt marshes, whereas Rubrobacter showed the opposite pattern. 3) Soil TC, TN, and microbial biomass nitrogen were key environmental factors associated with the shifts in bacterial community structure. Structural equation modeling further revealed that vegetation restoration primarily altered soil physicochemical conditions, which indirectly drove changes in bacterial diversity and community structure by altering nutrient availability. These findings demonstrated that vegetation restoration after S. alterniflora removal enhances bacterial diversity and restructures bacterial communities by modifying soil environment, with the positive effects of mangrove restoration on bacterial communities becoming more pronounced with increasing restoration age.

Key words: Spartina alterniflora removal, restoration mode, bacterial community, driving factor, Minjiang Estuary Wetland