Effects of weeding and fertilization on soil nitrogen mineralization and leaching in the mixed forest of Dalbergia odorifera and Santalum album

: The mixed plantation of precious tree species Dalbergia odorifera and Santalum album is an important model for the development of plantations in South China. Based on an experiment with four treatments, i.e., CK (without any treatment), weeding, fertilization, weeding+fertilization, we investigated the effects of weeding and fertilization on soil net mineralization rate, net nitrification rate, net ammonification rate, and nitrogen leaching rate. Among the four treatments, the maximum net nitrogen mineralization rate in the 0-10 cm soil layer was 18.92 and 18.13 mg·kg-1·month-1 in spring and autumn, respectively; the maximum nitrification rate was 20.35 and 18.85 mg·kg-1·month-1in spring and autumn, respectively; the maximum ammonium mineralization rate was 0.22 and 0.26 mg·kg-1·month-1 in summer and winter, respectively; the maximum nitrogen leaching was 15.98 mg·kg-1·month-1 in autumn and 86.69 mg·kg-1·year-1 in the whole year. The treatments of weeding, fertilization, weeding+fertilization reduced net mineralization rate and net nitrification rate. The annual nitrogen mineralization decreased by 26.2%, 16.1% and 6.3%, respectively, and the annual nitrogen nitrification decreased by 17.1%, 16.6%, and 1.4%, respectively. Moreover, the treatments of weeding, fertilization, weeding+fertilization inhibited soil ammonium accumulation and reduced annual nitrogen leaching by 25.2%, 8.6%, and 6.1%, respectively. Compared with weeding, fertilization and weeding+fertilization, seasonal factors had more significant effects on soil nitrogen mineralization and leaching. Weeding, fertilization and weeding+fertilization decreased soil nitrogen nitrification and ammonification to a certain extent, reduced soil nitrogen mineralization and leaching loss, which contribute to the preservation of soil fertility and nitrogen accumulation.