Shifts in soil microbial diversity and greenhouse gas emission dynamics.

Anthropogenic land formation has been shown to substantially alter terrestrial landscapes, impacting both soil properties and microbial communities. Nevertheless, the impact of anthropogenic land formation on greenhouse gas emissions and the underlying mechanisms were not fully elucidated. In this study, chronological sequences of soil samples were collected from a recently reclaimed land area at multiple intervals over a fifteen-year period. High-throughput sequencing was employed to analyze the composition of microbial communities, including bacteria, fungi, and protists. It was observed that land formation induced profound shifts in soil properties, with notable decreases in soil temperature and increases in moisture content over time. Furthermore, significant increases in greenhouse gas emissions were observed during the land formation process. The soil bacterial diversity exhibited a marked increase at the outset of land formation, followed by a period of relative stability over time. In contrast, fungal diversity was lowest, and protistan diversity was highest, after 7-9 years of reclamation. The impact of land formation on soil microbial communities varied across taxa, with bacteria exhibiting greater sensitivity compared to fungi and protists. Additionally, structural equation modeling (SEM) demonstrated that bacterial diversity directly influences carbon dioxide emissions, while protistan diversity affects methane and nitrous oxide emissions in reclaimed lands. Variations in soil bacterial diversity were driven by changes in soil moisture and nitrate content during land formation, whereas protistan diversity was primarily regulated by total organic carbon levels. These findings suggest that optimizing organic matter inputs, enhancing early-stage vegetation establishment, and steering microbial community succession during hydraulic land reclamation may represent effective strategies to mitigate greenhouse gas emissions and improve the ecological sustainability of reclaimed coastal landscapes.