西苕溪典型小流域土地利用对氮素输出的影响

在太湖地区的西苕溪流域不同地理位置选择了11个小流域,于2004年分3次野外监测氮素输出浓度.利用多年降雨径流关系估算径流量,用于计算各小流域氮素输出负荷与强度,结合2000年TM遥感影像获得的各小流域土地利用数据,综合分析了土地利用对流域氮素输出的影响.结果表明,流域土地利用结构对氮素输出具有重要影响,流域耕地面积比例与氮素输出水平呈正比,而林地比例与氮素输出水平呈反比;各小流域面积的大小与氮素输出负荷呈正相关,而小尺度流域面积对氮素输出浓度和单位面积氮素输出强度无关.

Influence of land use on nitrogen exports in Xitiaoxi typical sub-watersheds

11 sub-watersheds were selected in different geographic positions of Xitiaoxi watershed in Taihu area. In year 2004 the concentration of nitrogen export was monitored in the field for three times. The nitrogen export load and strength of each sub-watershed were calculated, utilizing raining runoff relation of many years for estimating runoff amount. Combining the land use data of each sub-watershed obtained from TM image in year 2000, the influence of land use on watershed and nitrogen export was analyzed comprehensively. Watershed land use structure possessed important influence on nitrogen export. The cultivated land area ratio was related positively with the nitrogen export level; while the forest land area ratio was related negatively with the nitrogen export level. The size of each sub-watershed area was related positively with nitrogen export load; while the small watershed area was not related with nitrogen export concentration and nitrogen export strength of unit area.