亚热带不同林龄次生林与杉木林土壤氮淋溶损失特征OACSCDCSTPCD

To assess whether soil nitrogen leaching would be affected by the planting subtropical evergreen broad-leaved secondary forests of different ages and Chinese fir(Cunninghamia lanceolata)plantations,soil column microcosm in situ culture experiment was used to compare the soil total nitrogen,nitrate and ammonium concentrations and fluxes between 9-year-old and 45-year-old secondary forests(with Castanopsis carlesii as the dominant tree species),and between C.carlesii and C.lanceolata plantations(both 9-year-old).The results showed that:(1)The concentrations of total nitrogen and nitrate in the four forest soils showed a general pattern of 45-year-old secondary forest>9-year-old secondary forest>C.lanceolata plantation>C.carlesii plantation.The concentration of ammonium nitrogen was 45 years old secondary forest>C.lanceolata plantation>9 years old secondary forest>C.carlesii plantation.(2)The fluxes of total nitrogen and nitrate of the four forest types in soil leaching solutions were as follows:9-year-old secondary forest>45-year-old secondary forest>C.lanceolata plantation>C.carlesii plantation,and soil ammonium leaching fluxes varied significantly among the four forest types between may and August,showing a order of C.lanceolata plantation>45-year-old secondary forest>9-year-old secondary forest>C.carlesii plantation.(3)The annual leaching fluxes of total nitrogen were 14.24,13.27,7.26 and 10.97 g/(m2·a),the nitrate leaching fluxes were 10.88,9.97,5.35 and 8.44[g/(m2·a)],and the ammonium leaching fluxes were 1.97,2.18,1.59 and 2.26 g/(m2·a),in the 9-year-old and 45-year-old secondary forests,C.carlesii plantation and C.lanceolata plantation,respectively.In summary,the leaching loss of soil total nitrogen and nitrate decreased along the growth of subtropical evergreen broad-leaved secondary forest age,but the plantations of C.lanceolata accelerate nitrogen leaching loss from soils relative to the native tree species.