土壤细菌呼吸对西双版纳热带森林恢复的响应

揭示不同恢复阶段热带森林土壤细菌呼吸季节变化及其主控因素，对于探明土壤细菌呼吸对热带森林恢复的响应机制具有重要的科学意义。以西双版纳不同恢复阶段热带森林(白背桐群落、崖豆藤群落和高檐蒲桃群落)为研究对象，运用真菌呼吸抑制法及高通量宏基因组测序技术分别测定土壤细菌呼吸速率和细菌多样性，并采用回归分析及结构方程模型揭示热带森林恢复过程中土壤细菌多样性、pH、土壤碳氮组分变化对土壤细菌呼吸速率的影响特征。结果表明：1)不同恢复阶段热带森林土壤细菌呼吸速率表现为：高檐蒲桃群落((1.51±0.62)CO₂ mg g^-1 h^-1)显著高于崖豆藤群落((1.16±0.56)CO₂ mg g^-1 h^-1)和白背桐群落((0.82±0.60)CO₂ mg g^-1 h^-1)(P<0.05)。2)不同恢复阶段土壤细菌呼吸速率呈显著的单峰型季节变化(P<0.05),最大值均出现在9月：高檐蒲桃群落((...

Response of soil bacterial respiration to tropical forest restoration in Xishuangbanna, China

This study aimed to explore the seasonal variations and their main controlling factors for soil bacterial respiration rates along secondary tropical forest succession, thus identifying the response mechanism of soil bacterial respiration to tropical forest restoration. In this study, the substrate-induced respiration technique and high-throughput sequencing technology were utilized to determine the soil bacterial respiration rate and bacterial diversity, respectively, at three secondary restoration stages (i.e., Mallotus paniculatus, Mellettia leptobotrya, and Syzygium oblatum communities) of Xishuangbanna. We also analyzed the effects of the shifts in soil bacterial diversity, pH, carbon pool and nitrogen pool on soil bacterial respiration rate, using regression and structural equation model analyses. The results showed that:1) the soil bacterial respiration rates were significantly higher in S. oblatum ((1.51±0.62)CO₂ mg g^-1 h^-1) than in those in M. leptobotrya ((1.16±0.56)CO₂ mg g^-1 h^-1) and M. paniculatus ((0.82±0.60)CO₂ mg g^-1 h^-1). 2) Soil bacterial respiration rates showed an obvious single-peak seasonal trend with the maximum value occurred in September. In September, soil bacterial respiration rates were ranked as S. oblatum community ((2.41±0.29)CO₂ mg g^-1 h^-1)>M. leptobotrya community ((1.75±0.33)CO₂ mg g^-1 h^-1)>M. paniculatus community ((1.60±0.66)CO₂ mg g^-1 h^-1). 3) Soil microbial carbon also showed an increasing trend along the tropical forest restoration; the order of soil microbial carbon was S. oblatum community ((3.06±1.45)g/kg)>M. leptobotrya community ((2.22±1.40)g/kg)>M. paniculatus community ((1.75±1.14)g/kg). Microbial carbon showed a significantly seasonal variation, which could explain 21% to 35% of the variations in soil bacterial respiration rates. 4) Soil bacterial diversity increased along the tropical forest restoration; the contribution of bacterial diversity to soil bacterial respiration dynamics was ranked as S. oblatum (72.60%)>M. leptobotrya (67.90%)>M. paniculatus (64.80%). 5) The concentrations of carbon and nitrogen pools in later restoration stage increased by 4.27%-58.77%, compared with the early restoration stage. Soil bacterial respiration rates were significantly positively correlated with soil organic carbon and ammonium nitrogen (P<0.01), as well as total nitrogen and soil pH (P<0.05). 6) The structural equation modeling showed that bacterial Shannon index, microbial biomass carbon, total nitrogen, ammonium nitrogen, and soil pH could directly regulate bacterial respiration; bacterial Shannon index and microbial biomass carbon primarily contributed to soil bacterial respiration dynamics. In contrast, soil organic carbon, total nitrogen, and ammonium nitrogen indirectly promoted bacterial respiration by increasing Shannon index and microbial biomass carbon. Therefore, the secondary tropical forest succession in Xishuangbanna significantly promoted the soil bacterial respiration. The temporal variations in soil bacterial respiration rates were primarily directly determined by microbial carbon and bacterial Shannon diversity, while they were indirectly regulated by total organic carbon, ammonium nitrogen, and total nitrogen.