不同恢复阶段热带森林土壤nirS型反硝化微生物群落结构及多样性特征

探明热带森林土壤反硝化微生物群落结构及多样性,对于理解反硝化引起的N₂O排放及缓解全球变暖具有重要意义。本研究以西双版纳3个不同恢复阶段热带森林类型[即白背桐（Mallotus paniculatus,MP）、崖豆藤（Millttia leptobotrya,ML）群落、群落及高檐蒲桃（Syzygium oblatum,SO）群落]为研究对象,揭示土壤nirS型反硝化微生物群落组成及多样性的干湿季变化,分析热带森林恢复过程中土壤理化环境变化对nirS型反硝化细菌群落的影响。结果表明,变形菌门（Proteobacteria）和酸杆菌门（Acidobacteria）相对丰度表现为恢复前期高于恢复后期,而脱氯单胞菌属（Dechloromonas）、嗜盐单胞菌属（Halomonas）和罗思河小杆菌属（Rhodanobacter）表现为恢复后期高于恢复前期;绿弯菌门（Chloroflexi）和放线菌门（Actinobacteria）均随恢复年限增加而增加,而贪铜菌属（Cupriavidus）和假单胞菌属（Pseudomonas）的相对丰度表现为随恢复年限增加而降低。9月份各样地新检测出的属数量表现为：SO （19种） > MP （13种） > ML （7种）。土壤nirS型反硝化微生物群落的Shannon多样性指数表现为：高檐蒲桃群落 > 崖豆藤群落 > 白背桐群落,且9月（湿季） > 3月（干季）。相关分析表明,热带森林恢复引起土壤N库（全氮、NH₄⁺、NO₃^-）、C有效性（微生物量碳、易氧化碳）及微气候（土壤含水率与温度）的改变,能够显著影响nirS型反硝化细菌群落的结构及多样性。主成分分析结果表明,土壤硝态氮、微生物量碳、全氮及易氧化碳是调控不同恢复阶段热带森林土壤nirS型反硝化细菌群落结构及多样性变化的主控因子,其次为土壤水分、温度、水解氮、pH、铵态氮、有机碳、容重及C/N。

The structure and diversity of nirS-denitrifying microbial community across three restoration stages of Xishuangbanna tropical forests

Identifying the structure and diversity of denitrifying microbial community in tropical forest is of great significance for understanding N₂O emissions from soil denitrification as well as for mitigating global warming. In this study, three secondary restoration stages (i.e., Mallotus paniculatus, Millettia leptobotrya, and Syzygium oblatum communities) of Xishuangbanna tropical forests were selected to explore the composition and diversity of nirS-denitrifying microbial community in dry and wet seasons. We also examined the effects of variations in soil physicochemical properties on structure and diversity of nirS-denitrifying bacteria community during tropical forest restoration. Our results showed that the relative abundance of Proteobacteria and Acidobacteria was higher in early recovery stage than in later stage. In contrast, the relative abundance of Dechloromonas, Halomonas, and Rhodanobacter was higher in later stage than in early one. The relative abundance of Chloroflexi and Actinobacteria increased along with the tropical forest restoration, while that of Cupriavidus and Pseudomonas had an opposite tendency. The genus number of nirS-denitrifying bacteria community in September was ranked as S. oblatum (19) > M. paniculatus (13) > M. leptobotrya (7). The order of Shannon diversity of nirS-denitrifying microbial community was S. oblatum > M. leptobotrya > M. paniculatus. The Shannon diversity was higher in wet season (September) than in dry season (March). Correlation analysis showed that the structure and diversity of nirS-denitrifying microbial community had a close association with N pool (i.e., total nitrogen, NH₄⁺, and NO₃^-), C availability (i.e., microbial biomass carbon, easily oxidized carbon), and microclimate (i.e., soil water and temperature) during tropical forest restoration. Principal component analysis (PCA) showed that nitrate nitrogen, microbial biomass carbon, total nitrogen, and easily oxidized carbon were the key factors controlling community structure and diversity of nirS-denitrifying microbial community across three recovery stages of tropical forests. The effect of soil water content, temperature, hydrolytic nitrogen, pH, ammonium nitrogen, organic carbon, bulk density and C/N was ranked the next.