Abstract:

Aims：Mowing and mulching are key physical measures for controlling the invasive plant Spartina alterniflora in coastal wetlands. However, their long-term effects on soil physicochemical properties and microbial communities remain unclear. 

Method：This study investigated soil from Spartina alterniflora-invaded tidal flats in Zhanjiang, Guangdong Province. Four treatment combinations were established: removal versus retention of cut Spartina alterniflora residues under mulching conditions, and removal versus retention under non-mulching conditions. Soil physicochemical parameters were measured, and soil bacterial community characteristics were analyzed via amplicon sequencing to examine correlations between bacterial community composition and environmental factors. 

Results：(1) Retaining Spartina alterniflora residues significantly increased soil total nitrogen, total carbon, organic carbon, and available potassium content. (2) Long-term mulching markedly reduced soil bacterial α-diversity, relative abundance of major bacterial phyla and genera, and altered community structure. Under the residue-removal mulching treatment, bacterial Pielou's evenness and Simpson’s diversity indices were significantly lower than in other treatments. Relative abundances of the Campylobacterota phyla and Sulfurovum genera significantly increased under residue-removal mulching. (3) Temperature, total nitrogen, total carbon, organic carbon, and available potassium jointly influenced the abundance of dominant bacteria such as Vibrio and Salinimicrobium, collectively explaining 74.6% of the variation in community structure. 

Conclusion：In summary, mulching after mowing is an effective physical control measure for Spartina alterniflora. However, long-term mulching combined with residue removal significantly reduces soil bacterial community diversity and alters community structure. Therefore, after mowing, a reasonable mulching duration should be established and mowed plant residues retained to avoid substantial negative impacts on soil bacterial community diversity and structure.

Key words: mulching, mowing, coastal wetlands, Spartina alterniflora, soil physichemical properties, bacterial community