Haihui Chen, Zhipan Lin, Leyu Tian, Yiqing Chen, Zongzhu Chen, Juzhi Liang, Xiangling Lei, Shaofeng Su, Shouqian Nong
During both seasons, SF exhibited significantly higher microbial biomass phosphorus, microbial biomass nitrogen, and microbial biomass carbon than the other forest types. From the dry to wet season, microbial entropy, microbial biomass stoichiometric ratios, and microbial biomass levels increased across all forest stands. The direction of the associations between microbial biomass, its stoichiometric ratios, and environmental factors was generally consistent between seasons, whereas the strength of these associations varied seasonally. RDA identified soil total phosphorus, available phosphorus (AP), and precipitation (PRCP) as the main factors associated with variations in microbial biomass levels and their elemental stoichiometric ratios. Their dominant roles were not altered by seasonal transition. Exploratory supplementary analysis further supported the seasonal reconfiguration of environmental regulatory pathways.
INTRODUCTION: Soil microorganisms regulate plant nutrition through nutrient transformation, and forest soil microbial biomass is crucial for ecosystem health and nutrient cycling. Tropical coastal shelterbelts are essential for coastal ecological security, but seasonal microbial biomass variation and environmental controls in forests remain insufficiently understood.
METHODS: To determine how soil microbial biomass changes seasonally in tropical coastal shelterbelts and which environmental factors regulate this variation, four representative shelterbelt types in Wenchang, Hainan, were examined: secondary forest (SF), mixed forest, Cocos nucifera forest, and Casuarina equisetifolia forest. The differences in soil microbial biomass characteristics between wet and dry seasons were compared. Correlation analysis and redundancy analysis (RDA) were adopted as core analytical approaches to identify associations between environmental factors and microbial biomass. Exploratory structural equation modeling was performed as supplementary analysis to visualize potential regulatory pathways.
RESULTS: During both seasons, SF exhibited significantly higher microbial biomass phosphorus, microbial biomass nitrogen, and microbial biomass carbon than the other forest types. From the dry to wet season, microbial entropy, microbial biomass stoichiometric ratios, and microbial biomass levels increased across all forest stands. The direction of the associations between microbial biomass, its stoichiometric ratios, and environmental factors was generally consistent between seasons, whereas the strength of these associations varied seasonally. RDA identified soil total phosphorus, available phosphorus (AP), and precipitation (PRCP) as the main factors associated with variations in microbial biomass levels and their elemental stoichiometric ratios. Their dominant roles were not altered by seasonal transition. Exploratory supplementary analysis further supported the seasonal reconfiguration of environmental regulatory pathways.
DISCUSSION: These findings demonstrate the stand- and season-specific patterns of soil microbial biomass in tropical coastal shelterbelts and clarify how the responses of microbial biomass to environmental factors are reshaped by seasonal precipitation variations.