生物质炭输入对毛竹林土壤有机碳组分与CO2通量的影响及其机理

Results of my previous NSFC funded project revealed that long-term intensive management significantly decreased soil carbon storage and stability in Moso bamboo (Phyllostachys pubescens) forests. Biochar addition is regarded as an important approach to enhance soil carbon sequestration and mitigate global climate change; however, its effects on soil carbon processes and the associated mechanisms in subtropical plantation soils are still unclear. Moso bamboo plantations will be selected as the study object in this project, and nuclear magnetic resonance (NMR), pyrolysis gas chromatography mass spectrometry (Py-GC-MS), Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, phospholipid fatty acid (PLFA), and dynamic chamber-infrared gas analyzer (IRGA) methods will be adopted. Field experiments will be conducted to investigate the effects of biochar (made from bamboo leaf) addition on soil carbon storage, labile carbon pools, and chemical structure of organic carbon fractions. Furthermore, the dynamic changes in soil CO2 fluxes, organic carbon fractions, labile carbon pools, microbial community characteristic and other factors under different application rates of biochar and the synergistic effect of biochar addition and different fertilization practices will be intensively investigated. In addition, laboratory incubation experiments will be conducted to study the effects of different biochar addition rates on soil organic carbon mineralization in Moso bamboo forests under various soil temperature and moisture conditions. This project aims to elucidate the mechanisms associated with the impact of biochar addition on soil carbon sequestration in Moso bamboo plantations, and advance the development of technology for increasing carbon storage in subtropical plantation soils.

申请者在前一基金的研究中发现，长期集约经营显著降低毛竹林土壤碳储量及碳库稳定性。生物质炭输入被认为是增加土壤碳汇应对全球气候变化的重要途径之一；然而，其对亚热带人工林土壤碳过程的影响及其机理尚缺乏深入研究。本项目拟以毛竹人工林为研究对象，综合应用NMR、Py-GC-MS、FT-IR、元素分析、PLFA以及动态气室-IRGA法等分析技术，利用野外控制试验，研究竹叶生物质炭输入对不同集约经营历史毛竹林土壤碳储量、活性碳库、有机碳组分化学结构的影响；在此基础上，深入研究不同用量生物质炭输入及其与施肥措施协同影响下的土壤CO2通量、有机碳组分、活性碳库、微生物群落特征等因素的动态变化规律；再通过室内模拟培养试验，阐明生物质炭输入对毛竹林土壤有机碳矿化特征的影响及其对不同温度、湿度的响应规律；从而较系统地揭示生物质炭输入对毛竹林土壤碳汇功能的影响机理，为亚热带人工林土壤碳储存技术的研发提供科学依据。

本项目系统研究了生物质炭输入对毛竹林土壤呼吸组分、土壤有机碳矿化特征以及土壤N2O通量的影响。取得的主要研究结果如下：.1. 毛竹林土壤总呼吸、自养呼吸速率均随生物质炭输入量的增加而升高，而土壤异养呼吸速率则随生物质炭输入量的增加而降低。5 t hm-2生物质炭处理对毛竹林土壤呼吸CO2年累积排放量无显著影响，15 t hm-2生物质炭处理显著增加土壤呼吸CO2年累积排放量；生物质炭处理显著降低土壤异养呼吸CO2年累积排放量，却显著增加毛竹林土壤自养呼吸CO2年累积排放量。.2. 生物质炭施用显著降低了毛竹林土壤N2O的排放，且随着生物质炭施用量的增加，N2O的排放量显著降低，同时，生物质炭导致的土壤N2O排放量降低，随着时间的推移而减少。结构方程模型结果表明，生物质炭降低毛竹林土壤N2O排放通量的机制在于降低土壤活性氮浓度和土壤氮循环相关酶活性和土壤硝化/反硝化速率。.3. 与对照相比，氮肥处理和生物质炭-氮肥混施处理均增加了毛竹林土壤总呼吸速率，而生物质炭处理则降低了毛竹林土壤总呼吸速率。氮肥处理增加了毛竹林土壤异氧呼吸速率，而生物质炭处理和混施处理均降低了土壤异氧呼吸速率，氮肥和混施处理均增加了土壤自养呼吸速率。.4. 与对照相比，化肥处理显著增加了毛竹林土壤的异养呼吸速率，而生物质炭基肥处理则显著降低了毛竹林土壤异养呼吸速率。化肥处理和生物质炭基肥处理均显著增加了毛竹林土壤自养呼吸速率。化肥处理显著增加了土壤异养呼吸速率的Q10值，而生物质炭基肥处理则对上述指标无显著影响。.5. 生物质炭处理显著降低毛竹林土壤有机碳矿化速率，而竹叶处理显著增加毛竹林土壤有机碳矿化速率；生物质炭处理显著增加土壤真菌群落丰度，而竹叶处理显著降低土壤真菌群落丰度，竹叶和生物质炭处理对土壤细菌群落丰度均无显著影响；全氮、NH4+-N、MBC、β-葡萄糖苷酶、脱氢酶、烷氧碳是影响土壤真菌群落的关键环境因子，NH4+-N、NO3−-N、MBC、WSOC、烷基碳、烷氧碳、芳香碳、脱氢酶是影响土壤细菌群落的关键环境因子。