不同利用方式红壤反硝化势和气态产物排放特征

采用厌氧培养-乙炔抑制法测定了4种不同利用方式红壤的反硝化势和气态产物N₂O和N₂的排放速率。结果表明，不同利用方式红壤反硝化势和N₂O和N₂的排放速率差异明显，土壤反硝化势强弱顺序依次为：竹林>茶园>林地>旱地。反硝化势与土壤有机碳(P<0.05)、厌氧培养期间土壤CO₂累积排放量(P<0.01)、nirS基因丰度( P<0.05)和nirK基因丰度(P<0.05) 呈显著正相关关系。逐步回归分析结果表明，CO₂累积排放量表征的易矿化碳是造成不同利用方式红壤反硝化势差异的主要原因，可以解释反硝化势变化的66%(P<0.01)。不同利用方式红壤N₂O和N₂排放速率差异明显，旱地红壤N₂O和N₂排放速率均最低，表明土壤pH的提升并没有增加旱地红壤的反硝化损失风险和N₂O排放速率。土壤易矿化有机碳含量也是影响不同利用方式红壤N₂O和N₂排放速率的主要因素。反硝化功能基因nirS、nirK和nosZ的丰度均与CO₂累积排放量呈显著正相关关系，进一步支持了土壤易矿化有机碳含量是影响不同利用方式红壤反硝化势和气态产物排放的主要因子。土壤pH是影响不同利用方式红壤反硝化气态产物N₂/N₂O的主要因素，但是pH影响红壤N₂/N₂O的微生物机制仍需要进一步研究。

Denitrification Potential and Gas Emission in Red Soils Under Different Land Use Types

In this study, soil samples were collected from four land use types, i.e. forest (F), bamboo (B), tea plantation (TP) and upland (U), and the denitrification potential and N₂O and N₂ emission were determined by using an anaerobic incubation method. The results showed that there were significant differences in the potential denitrification in soils under different land use types. The denitrification potential was in the following order: B > TP > F > U. The denitrification potential was significantly positively correlated with SOC (P<0.05), CO₂ emission (P<0.01), nirS (P<0.05) and nirK (P<0.05). The stepwise regression analysis showed that the mineralized C was the key factor controlling the denitrification potential, which could explain 66% of variation of the denitrification potential in soils under different land use types. The differences in N₂O and N₂ emission were also significant in soils under different land use types, the lowest N₂O and N₂ emission were observed in soil of upland, indicating the enhancing pH did not increase the potential N loss via denitrification and N₂O emission. The mineralized C was also the key factor controlling N₂O and N₂ emission in soils under different land use types. The significant relationship between nirS, nirK, nosZ and the mineralized C further supported our conclusions. Soil pH was the key factor regulating the ratio of N₂/N₂O, but the mechanisms of pH regulating the ratio of N₂/N₂O need further study.