Effects of bamboo leaves and their biochar additions on soil N₂O flux in a Chinese chestnut forest

【Objectives】 Nitrous oxide (N2O) is the main component of greenhouse gases, and its warming effect is extremely strong. Terrestrial ecosystem is one of the main sources of N2O emissions. Plantationecosystem is an important component of the terrestrial ecosystem, but effects of management practices onsoil N2O flux in the plantation ecosystem are seldom studied. The objective of this study was to investigate effects of bamboo leaves and their biochar addition on seasonal variation in N2O flux in the soils of Chinese chestnut stands and to provide a theoretical basis and scientific evidence for the modulation of the soil N2Oefflux in the plantation ecosystem. 【Methods】 An experiment was established in the Chinese chestnut forest in Shankou Township, Lin’an City, Zhejiang Province in the period from July, 2012 to July, 2013. The treatments included control, application of bamboo leaves (Leaf), and application of biochar (Biochar). Soil N2O fluxes were analyzed by static closed chamber/GC technique, and soil temperature, the contents of soil water, water soluble organic carbon (WSOC), water soluble organic nitrogen (WSON), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), NH+4-N, and NO-3-N were determined as well.【Results】 Soil N2O flux exhibits a strong seasonal pattern, with the maximum value in July and the minimum in January, regardless of the treatments. Compared to the control, the annual average flux and annual cumulative value of soil N2O emission under the Leaf treatment are increased by 17.2% and 12.8%, respectively, while they are decreased by 27.4% and 20.5%, respectively under the Biochar treatment. In comparison with the Control, the concentrations of soil WSON, MBN, NH+4-N and NO-3-N under the Leaf treatment are increased by 12.4%, 19.1%, 8.3%, and 13%, respectively, while the concentrations of soil NH+4-N and NO-3-N are decreased by 14.1% and 18%, respectively under the Biochar treatment. An exponential relationship between soil temperature and the N2O flux is observed regardless of the treatment. The soil N2O flux correlates to soil temperature and WSOC concentration (P 0.05) but not to soil MBC concentration. Under the Leaf treatment, the soil N2O flux correlates to NH+4-N, NO-3-N and WSON concentrations (P0.05). 【Conclusions】Regardless of the treatment, the soil N2O flux in the Chinese chestnut forest shows significant seasonal variation, with the high value in the summer and low value in the winter. The soil N2O emission in the Chinese chestnut stand is increased under the Leaf treatment, but decreased under the Biochar treatment, and the changes in the soil N2O emission caused by the additions of bamboo leaves and their biochar are probably attributed to the changes in soil C and N pools caused by adding bamboo leaves and their biochar.