三峡库区2种土地利用方式下土壤盐基离子及碳氮含量对氮添加的响应

Response of Soil Based Cations and Carbon and Nitrogen Contents to Nitrogen Addition Under Two Land Use Patterns in the Three Gorges Reservoir Area

为探究三峡库区2种土地利用方式下土壤交换性盐基离子及土壤碳氮含量对氮添加的响应,以湖北省秭归县的林地和果园土壤为研究对象,进行室内土柱淋溶模拟试验,研究4种不同氮添加量(0,50,120,200 kg/(hm^(2)·a))下,土壤中交换性Ca^(2+)、Mg^(2+)、Na^(+)、K^(+)以及NO_(3)^(-)-N、DOC的变化。结果表明:随着氮添加量的增加,林地土壤中的交换性盐基离子淋失量显著增加(p<0.05),而果园土壤中的交换性盐基离子淋失量无显著变化,且林地土壤中交换性盐基离子淋失总量与各盐基离子淋失量均高于果园土壤;经N1、N2、N3处理后,与对照组(N0)相比,林地土壤中的交换性盐基离子淋失总量分别增加1.78%,4.45%,8.49%,且NO_(3)^(-)-N淋失量分别增加89.21%,77.73%,157.25%,说明氮添加通过加剧土壤中NO_(3)^(-)-N的淋失带走土壤中交换性阳离子;林地土壤DOC累计淋失量经N2、N3处理分别降低1.15%,9.53%,果园土壤DOC累计淋失量经N1、N2、N3处理分别降低15.55%,5.88%,17.16%;氮添加下,与人为干扰的果园土壤相比,相对自然状态下的林地土壤中交换性盐基离子淋失量对氮添加的响应更敏感。研究表明氮添加量的增加提高林地土壤交换性盐基离子与NO_(3)^(-)-N的淋失量,减少林地与果园土壤DOC的淋失量。

To investigate the response of soil exchangeable salt-based ions and soil carbon and nitrogen content to nitrogen addition under two land use modes in the Three Gorges reservoir area,the changes of soil exchangeable Ca^(2+),Mg^(2+),Na^(+),K^(+)and NO_(3)^(-)-N,DOC in forest and orchard soils in Zigui County,Hubei Province were investigated by indoor soil column leaching simulation experiments at four different nitrogen additions[0,50,120 and 200 kg/(hm^(2)·a)].The results showed that with the increasing of nitrogen addition amount,the leaching loss amount of exchangeable base cations in the forest soil increased significantly(p<0.05),while that in the orchard soil did not change significantly.The total leaching loss amount of exchangeable base cations and the leaching loss amount of each base ion in the forest soil were higher than those in the orchard soil.Compared with the blank control(N0),in the forest soil under the three nitrogen additions(N1,N2 and N3),the total leaching loss amount of exchangeable base cations increased by 1.78%,4.45%and 8.49%,respectively,and the leaching loss amount of NO_(3)^(-)-N increased by 89.321%,77.73%and 157.25%,respectively,indicating that nitrogen addition increased the leaching loss of NO_(3)^(-)-N from the soil and thus took away exchange cations from the soil.The cumulative loss of DOC from forest soils decreased by 1.15%and 9.53%under N2 and N3 treatment,respectively,while it in orchard soils decreased by 15.55%,5.88%and 17.16%under N1,N2 and N3 treatment,respectively.Compared with orchard soils disturbed by human,the leaching amount of exchangeable based cations in forest under a relatively natural state was more sensitive to nitrogen addition.The research showed that the increasing of nitrogen addition increased the leaching loss amount of exchangeable base cations and NO_(3)^(-)-N in forest soil and decreased the leaching loss amount of DOC in forest and orchard soils.