不同淹水频率洪泛区湿地土壤氨挥发研究

在向海洪泛区湿地以不同淹水频率划分垂直河道方向的5个典型样区(常年淹水洪泛区、一年一遇洪泛区、五年一遇洪泛区、十年一遇洪泛区和百年一遇洪泛区),应用通气法在芦苇生长季,分别于7,9和11月对各样地土壤氨挥发速率进行测定,结果表明,研究区9月土壤氨挥发速率最高,11月次之,7月土壤氨挥发速率最低,且差异显著,7,9,11月实验期土壤氨挥发平均速率分别为0.175,1.155,0.651 mg/(m²·h);7月不同淹水频率的样地间氨挥发速率无显著差异,9月沿淹水频率增加方向土壤氨挥发速率呈现“U”型,即淹水频率最低和最高的样地土壤氨挥发速率高,五年一遇洪泛区湿地土壤氨挥发速率最低,11月的变化趋势则与9月相反,五年一遇和一年一遇洪泛区湿地土壤氨挥发速率较其他样点略高;此外,放牧等干扰明显加剧了土壤氨挥发。

Ammonia volatilization from marsh soils of typical floodplains with different flooding frequencies

Ammonia volatilization was monitored to investigate the ammonia loss in alkaline wetlands. In-situ airflow enclosure was used to measure the amount of ammonia volatilization of marsh soils in 5 typical zones [including permanently floodplain (B), 1-year floodplain (O), 5-year floodplain (F), 10-year floodplain (T), 100-year floodplain (H)] which are divided by different flooding frequencies along the vertical direction of the river channel in different floodplain wetlands of the Xianghai National Nature Reserve, Jilin Province, in different growing seasons (July, September, and November 2010). The highest ammonia volatilization rate (1.155 mg/m²) was observed in September (0.651 mg/m²) followed by November, while the lowest rate was in July (0.175 mg/m²). There were significant differences in the amount of ammonia volatilization in different sampling seasons. However, no significant differences were observed in ammonia volatilization rates between sites in July. The values of ammonia volatilization appeared “U” style with increasing flooding frequencies in September (i.e. the ammonia volatilization rates were higher in those zones near or far away from the river channel than those in the middle zones). However, the ammonia volatilization rates were higher in both the 5-year and 10-year floodplains in November. Grazing was one of the important factors that influenced increased nitrogen losses through ammonia volatilization from alkaline wetland soils.