中文摘要：

通过室内模拟试验,研究40%、70%和110%土壤饱和持水量（WHC）下,不同形态氮（硝态氮和铵态氮）添加对亚热带森林红壤氮素转化的影响.结果表明：70%WHC下土壤净矿化和氨化速率最高,40%WHC下最低;与对照相比,70%WHC下添加硝态氮使土壤净矿化和氨化速率分别降低56.1%和43.0%,110%WHC下分别降低68.2%和19.0%,但提高了氨化速率占矿化速率的比例,表明添加硝态氮抑制了硝化.110%WHC下,添加硝态氮后,土壤净硝化速率最低,但氧化亚氮（N2O）浓度最高,最大值出现在第3~7天,表明N2O产生自反硝化途径,硝态氮也在同时段降低;而40%WHC和70%WHC下,N2O浓度在培养初期最大,即使在铵态氮和硝态氮添加处理下,试验后期N2O浓度也没有显著变化,表明自氧硝化是试验前期N2O产生的主要途径.40%WHC下,土壤可溶性有机碳含量增加最多,且在铵态氮添加处理下增加最多,可见添加铵态氮促进土壤有机质矿化,增加可溶性有机碳,但是土壤水分含量增多不利于有机质矿化.在40%WHC和110%WHC下,铵态氮添加处理土壤可溶性有机氮（SON）变化速率分别显著高于对照73.6%和176.6%,而在硝态氮添加处理下,只有40%WHC下显著高于对照78.7%,表明高水分条件和添加铵态氮有利于SON的形成.

英文摘要：

An incubation experiment was conducted to investigate the effects of the additions of diF- ferent nitrogen forms on nitrogen transformation in red soils of subtropical forest under soil moisture conditions with 40%, 70% and 110% of water holding capacity （ WHC ）. The results showed that soil net mineralization and ammonification rates were maximum at 70%0 WHC and minimum at 40% WHC. Compared with the control, the addition of NO3--N decreased the soil net mineralization and ammonifieation rates by 56.1% and 43.0% under 70% WHC condition, and decreased by 68.2% and 19.0% under 110% WHC, respectively. However, the proportion of ammonification to mineral- ization increased at 70% and 110% WHC, which suggested that nitrate addition inhibited the nitri- fication. With addition of NO3--N at 110% WHC, the net nitrification rate was lowest while N2O emission was highest with the concomitant decrease of nitrate content, indicating that N2O emission was largely derived from denitrification. However, at 40% WHC and 70% WHC, the maximum N2O flux was found at the early stage of incubation. Even with addition of NH4＋-N and NO3--N, N2O flux did not change much at the latter stage of incubation, indicating that autotrophic nitrifica- tion was dominant for N2O production at the early stage of incubation. Under 40% WHC condition, soluble organic carbon increased more and it increased largely with NH4＋-N addition, which meant NH4＋-N addition could enhance the mineralization of soil organic matter. Under 40% and 110% WHC conditions, the addition of NH4＋-N increased significantly the soil soluble organic nitrogen （SON） by 73.6% and 176.6% compared with the control, respectively. A significant increase of 78.7% for SON was only found at 40% WHC under addition of NO3--N compared with the control. These results showed that high soil moisture condition and addition of NH4＋-N were of benefit to SON formation.