三江平原典型小叶章湿地土壤氮素净矿化与硝化作用

2004年6月—2005年7月,利用PVC顶盖原位培育法研究了三江平原典型草甸小叶章湿地和沼泽化草甸小叶章湿地土壤(0~15cm)无机氮库、净矿化/硝化速率动态、影响因素及年净矿化/硝化量.结果表明:两种湿地土壤的无机氮均呈明显的动态变化特征,其NH4 -N、NO3-N含量均表现为典型草甸小叶章湿地>沼泽化草甸小叶章湿地.两种湿地土壤的净矿化/硝化速率均呈明显的波动变化,生物固持作用、反硝化作用以及雨季较多降水是导致净矿化/硝化速率出现负值的主要原因.温度、降水、土壤有机质含量、C/N和pH是引起二者土壤无机氮库、净矿化/硝化速率存在明显差异的重要原因.典型草甸小叶章湿地的年净矿化量(19.41kg·hm-2)、年净硝化量(4.27kg·hm-2)以及净硝化量占净矿化量的百分比(22.00%)明显高于沼泽化草甸小叶章湿地(5.51kg·hm-2、0.28kg·hm-2和5.08%),说明前者的氮有效性以及维持可利用氮的能力明显高于后者.

Soil nitrogen net mineralization and nitrification in typical Calamagrostis angustifolia wetlands in Sanjiang Plain

From June 2004 to July 2005, the dynamics of soil inorganic N pool and N net mineralization/nitrification rates in typical meadow Calamagrostis angustifolia wetland (TMCW) and marsh meadow C. angustifolia wetland (MMCW) in Sanjiang Plain were studied by top-closed PVC tube in situ incubation method, with the affecting factors and annual N net mineralization/nitrification investigated. The results showed that the soil inorganic N in the two wetlands had evident dynamic characteristics. The NH4 -N and NO3-N contents were much higher in TMCW soil than in MMCW soil, and the soil N net mineralization/nitrification rates in the two wetlands presented significant fluctuations. Biological immobilization, denitrification, and abundant precipitation in rainy season were the main reasons inducing the N net mineralization/nitrification rates to be negative, and temperature, precipitation, soil organic matter content, soil C/N ratio and soil pH were the main factors resulting in the significant differences of soil inorganic N pool and N net mineralization/nitrification rates between the two wetlands. The annual N net mineralization and nitrification and the percentage of nitrified N in mineralized N were much higher in TMCW soil than in MMCW soil, suggesting that TMCW soil was superior to MMCW soil in N availability and available N-maintaining capacity.