铲草和施肥对降香黄檀与印度檀香混交林土壤氮素矿化淋溶的影响

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

珍贵树种降香黄檀与印度檀香混交种植是当前华南地区人工林发展的一种重要模式.本研究设置对照(不做处理)、铲草、施肥、铲草+施肥4个处理,研究抚育措施对林地土壤净矿化速率、净硝化速率、净铵化速率和氮素淋溶速率的影响.结果表明:4个处理0~10 cm土层在春、秋季有最大净氮矿化速率,分别为18.92、18.13 mg·kg^-1·month^-1;在春、秋季有最大硝化速率,分别为20.35、18.85 mg·kg^-1·month^-1;夏、冬季有最大铵化速率,分别为0.22、0.26 mg·kg^-1·month^-1;秋季的氮素淋溶最严重,为15.98 mg·kg^-1·month^-1,全年最大淋溶为86.69 mg·kg^-1.铲草、施肥、铲草+施肥都在一定程度上抑制了土壤氮的净矿化和硝化速率,铲草、施肥、铲草+施肥处理年氮矿化量分别下降26.2%、16.1%、6.3%,年氮硝化量分别下降17.1%、16.6%、1.4%,同时也抑制了土壤铵态氮的累积.铲草、施肥、铲草+施肥处理全年氮素淋溶量依次减少25.2%、8.6%、6.1%.相对于铲草、施肥、铲草+施肥抚育措施,季节因素对土壤氮素矿化和淋溶过程的影响更显著.铲草、施肥、铲草+施肥措施在一定程度上抑制了土壤氮素硝化和铵化过程,减少了土壤氮素的矿化和淋溶损失量,有利于土壤肥力的保存和氮素的累积.

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^-1 in 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.