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以我国小兴安岭地区凉水国家级自然保护区30年林龄的人工红松林为研究对象,建立对照(0 kg hm~(-2)a~(-1))、低氮(20 kg hm~(-2)a~(-1))、中氮(40 kg hm~(-2)a~(-1))和高氮(80 kg hm~(-2)a~(-1))四种模拟氮沉降水平的样地;采用室内培养试验,研究了短期模拟氮沉降对人工红松林土壤氮净矿化、净硝化速率和氧化亚氮排放的影响。结果表明,与对照处理相比,经过2年的模拟氮沉降处理,土壤的净矿化、净硝化速率都有降低趋势。与对照相比,低氮、中氮、高氮土壤净矿化速率分别降低了16.9%、20.6%和25.2%,土壤净硝化速率分别降低了16.7%、20.9%和25.5%,但是处理间差异没有达到显著水平。净硝化速率与净矿化速率呈显著正相关关系(P<0.05),表明净矿化速率降低减少铵态氮供应量可能是氮沉降处理降低净硝化速率重要原因。另外,模拟氮沉降处理导致土壤p H降低也不利于硝化作用。中氮和高氮处理土壤氧化亚氮累积排放量分别比对照高84%和40%,但是差异不显著。高的氮沉降量使硝化过程中氧化亚氮的排放比例增加,可能是中氮和高氮处理下净硝化速率下降而土壤氧化亚氮排放量却增加主要原因。研究结果表明,氮沉降会影响我国小兴安岭地区森林土壤氮矿化和硝化过程,但是由于实验开展观测时间较短,其影响规律还需长期实验验证。
Taking 30 - year - old artificial Korean pine forests of Liangshui National Nature Reserve in Xiao Hinggan Mountains as the research object, the control (0 kg hm -2 -2 a -1) and the low nitrogen (20 kg hm - 2) a ~ (-1), four simulations of medium nitrogen (40 kg hm ~ (-2) a ~ (-1)) and high nitrogen (80 kg hm ~ (-2) a ~ Nitrogen deposition. The effects of short-term simulated nitrogen deposition on net N mineralization, net nitrification rate and N2O emission in artificial Korean pine forests were studied using laboratory culture experiments. The results showed that net mineralization and net nitrification rate decreased after two years of simulated nitrogen deposition compared with the control. Compared with the control, the net mineralization rates of low, medium and high nitrogen decreased by 16.9%, 20.6% and 25.2%, respectively, and the net nitrification rates decreased by 16.7%, 20.9% and 25.5%, respectively. However, Did not reach a significant level. There was a significant positive correlation between the net nitrification rate and the net mineralization rate (P <0.05), indicating that reducing the net mineralization rate and decreasing the supply of ammonium nitrogen may be the important reason for the net nitrification rate reduced by nitrogen deposition. In addition, the reduction of soil p H caused by simulated nitrogen deposition is not conducive to nitrification. The cumulative N2O emission from soil treated with medium and high nitrogen was 84% and 40% higher than that of the control respectively, but the difference was not significant. The high nitrogen deposition rate increased the proportion of nitrous oxide emissions during nitrification, which may be the main reason for the decrease of net nitrification rate and soil N2O emission under medium and high nitrogen treatments. The results show that nitrogen deposition will affect soil nitrogen mineralization and nitrification process in the forest of the Xiaoxing’an Mountains in our country. However, due to the short observation time, the influence rule needs long-term experimental verification.