浙江赋石水库集水区板栗林土壤氮素迁移特征

本研究通过在板栗林地设置径流小区,于2013年1—10月间采集径流水样进行测试,同时结合雨季前后土壤氮素数据,分析了浙江北部赋石水库集水区板栗林土壤氮素迁移特征.结果表明: 板栗林地的10次地表径流事件中,各径流小区径流水量差别较大,最大达0.51 m³;其中氮是主要的流失元素,硝态氮(NO₃^--N)、铵态氮(NH₄⁺-N)、总氮(TN)和化学需氧量(COD_Mn)的浓度分别为0.02～1.87、0.04～3.53、1.69～5.33和5.30～14.07 mg·L^-1,各水质指标受径流水量影响较大,且用一元一次方程可以较好地拟合氮素流失量与径流水量之间的相关关系;雨季前后板栗林地径流场上部、中部和下部3个位置的土壤中,氮素含量差异较大;总的变化趋势是随着海拔升高氮素含量增加,随着土层深度加深氮素含量降低.比较雨季前后4种土壤氮素(NO₃^--N、NH₄⁺-N、TN 和水解性氮Hydro-N)的差异发现,差异较大的为Hydro-N和TN,平均差异值为20.21和307.49 mg·kg^-1.该区氮素随径流流失风险较大,对赋石水库水体富营养化构成潜在压力,需重点关注.

Characteristics of nitrogen transportation in Castanea mollissima forest around the Fushi Reservoir watershed in north Zhejiang Province,China.

In this study, through setting runoff plots in Chinese chestnut (Castanea mollissima) fo-rest, the runoff water samples were collected and tested from January to October, 2013. Combining with soil nitrogen data before and after the rainy season, we analyzed the characteristics of soil nitrogen transportation in chestnut forest around the Fushi Reservoir watershed in north Zhejiang Pro-vince, China. The results showed that among the 10 surface runoff events of Chinese chestnut fo-rest, there exhibited a significant difference in runoff water volume of each runoff plot, and the maximum amount was 0.51 m³. Nitrogen was the major element associated with nutrient loss in the study region. The concentrations of nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), total nitrogen (TN) andchemical oxygen demend (COD_Mn) in the runoff water ranged from 0.02-1.87, 0.04-3.53, 1.69-5.33 and 5.30-14.07 mg·L^-1, respectively. The water quality indexes were greatly affected by the runoff volume, and the relationship between the amount of nitrogen loss and runoff could be well fitted by using a linear equation. The difference in nitrogen contents of the soil in the upper, middle and lower part of the runoff plots was evident both before and after the rainy season. Moreover, the nitrogen content increased with the increasing altitude, but this trend decreased with increasing soil depth. Comparison of the difference between the four forms of soil nitrogen (NO₃^--N, NH₄⁺-N, TN and hydrolyzable nitrogen Hydro-N of soil) before and after the rainy season showed that there existed significant differences in Hydro-N and TN, and the average diffe-rence values were 20.21 and 307.49 mg·kg^-1, respectively. In this area, there was a great risk of nitrogen loss with runoff, and the potential non-point source pollution in Fushi Reservoir should be concerned.