不同氮输入梯度下草甸沼泽土反硝化损失和N2O排放

在实验室培养条件下，设计N0，N1，N2，N3 4种氮输入梯度，净氮输入量分别为0，1，2 和5 mg/g，采用乙炔抑制技术，研究草甸沼泽土反硝化损失和N₂O排放. 结果表明:培养期间(23 d)N1，N2和N3梯度的N₂O排放速率平均值分别为12.55，7.59和4.04 μg/(kg·h)，反硝化损失速率平均值分别为11.52，9.87和3.10 μg/(kg·h)，二者均明显高于对照(N0)〔0.09和0.10 μg/(kg·h)〕；但高氮输入(N2和N3梯度)会对N₂O排放速率和反硝化损失速率产生一定的抑制作用，且随着梯度增大而加强，差异达到显著水平(P<0.05). 24 h时土壤有机碳矿化速率随氮输入梯度升高而增大，表明氮输入初期能对土壤有机碳矿化产生激发效应；但在整个培养期，有机碳矿化速率却随氮输入增加而降低，表明只有适当的氮输入才能促进土壤有机碳矿化，过量氮输入反而会对其产生抑制作用. 

Denitrification Loss and N2O Emissions from Different Nitrogen Inputs in Meadow Marsh Soil

A soil incubation experiment controlled by the acetylene inhibition method wasconducted under laboratory conditions to study the denitrification 1oss and N2O emissions from different nitrogen inputs applied to meadow marsh soil. We designed four nitrogen input level of N0, N1, N2, N3, respectively, the net nitrogen input amount is 0, 1, 2 and 5 mg/g. The results showed that the N₂O average emission rates of N1, N2, N3 were 12.55, 7.59, and 4.04 μg/(kg·h) during the incubation period (23 d). The denitrification loss average rates were 11.52, 9.87, and 3.10 μg/(kg·h), respectively. The average N₂O emission and denitrification loss rates were all significantly higher than the control group (0.09 and 0.10 μg/(kg·h)). This indicated that nitrogen input promoted the N₂O emissionand denitrification loss rates; however, higher nitrogen input (N2, N3) restrained N₂O emission and denitrification loss rates. As nitrogen input increased, the restraining effect increased, and the difference among N1, N2 and N3 reacheda significant level (P<0.05). In the incubation period, carbonmineralization rate increased in 24 h, but decreased at other times as nitrogeninput increased. This indicated that carbon mineralization had a priming effectin the short-term following nitrogen input. In the incubation period, appropriate nitrogen input promoted carbon mineralization, but excessive nitrogen input restrained carbon mineralization.