两种水分含量下生物质炭对黑土N2O排放及硝化反硝化基因丰度的影响

生物质炭对土壤结构改良、土壤肥力提升和农田温室气体排放具有重要意义。本研究以吉林省梨树县典型黑土为研究对象，通过培育实验，研究不同土壤水分含量（40%WHC和100%WHC）下，生物质炭种类（玉米秸秆生物质炭和稻壳生物质炭）和施加量（0%、1%和4%（w/w））对黑土N2O排放及硝化反硝化功能基因丰度的影响。结果表明，随着秸秆生物质炭施加量的增加，土壤N2O排放呈下降趋势，4%高量秸秆生物质炭添加下，土壤N2O排放量仅为1%低量秸秆生物质炭添加下的33.9%。同时土壤NO- 3-N也表现出一致性规律，4%高量生物质炭添加下土壤NO- 3-N含量显著低于1%低量生物质炭。在100%WHC土壤水分状况下，玉米秸秆生物质炭显著增加了土壤N2O排放，而稻壳生物质炭则显著降低了土壤N2O排放。高土壤水分显著促进了土壤N2O排放，进一步为实时荧光定量PCR结果所证实，高土壤水分通过增加nirS基因丰度进而促进了土壤反硝化作用过程，而4%高量稻壳生物质炭添加下nosZ基因丰度显著高于玉米秸秆生物质炭添加，表现出更强的N2O还原潜力。尽管amoA-AOA基因丰度在不同生物质炭添加量下并未发生显著变化，但amoA-AOB基因丰度在高量玉米秸秆生物质炭添加下显著下降。结果说明，土壤水分和生物质炭通过影响土壤硝化反硝化微生物的营养底物和代谢过程，进而影响土壤N2O排放特征。

Effects of Biochar on N2O Emission and Nitrification-denitrification Gene Abundances Under Two Water Status in Black Soils

Biochar returning to the field is important for soil structure improvement, soil fertility enhancement, and greenhouse gas emission. In the laboratory incubation, the effects of biochar types (maize straw biochar, rice husk biochar) and application amounts (0%, 1%and 4% w/w) on N2O emissions and nitrification-denitrification functional gene abundances in black soils under different soil moisture content (40%WHC and 100%WHC) were investigated by soil microcosm experiment in a typical black soil region in Lishu County, Jilin Province. The results showed that soil N2O emissions tended to decrease with increasing straw biochar. High straw biochar addition (4%) resulted in only 33.9% of soil N2O emissions as compared to low straw biochar addition (1%). Soil NO- 3-N also showed a consistent pattern, with soil NO- 3-N levels significantly lower at 4% high biochar addition than at 1% low biochar addition. Under 100%WHC soil moisture conditions, maize straw biochar significantly increased soil N2O emissions, while rice husk biochar significantly reduced soil N2O emissions. Real-time fluorescence quantitative PCR further confirmed that high soil moisture promoted soil denitrification by increasing nirS gene abundance, while nosZ gene abundance was significantly higher under 4% high rice husk biochar addition than maize straw biochar addition, showing greater N2O reduction capacity. Although the amoA-AOA gene has insignificant difference at different biochar additions, the amoA-AOB gene was significantly down-regulated at high levels of maize straw biochar addition. These results consistently suggest that soil moisture content and biochar affect soil N2O emissions by nutrient substrates and metabolic processes.