红河梯田景观格局的氮磷截留及水体富营养化研究

Nitrogen and Phosphorus Sequestration and Water Eutrophication in Honghe Terraced Landscape

红河梯田的“森林-村寨-梯田-水系贯穿其中”垂直景观格局影响氮磷物质的迁移和转化过程,为揭示其内在联系,以红河梯田“林-寨-田”和“林-田”两种景观格局中的地表水为研究对象,于2017年12月(旱季)和2018年6月(雨季)共采集18个水样测定总氮(TN)和总磷(TP),分析其时空特征,采用截留量和水体营养状态综合指数(EI)对截留和水体富营养化水平进行评价.结果表明:红河梯田的氮磷截留和水体富营养化与景观格局关系密切.(1)“林-寨-田”景观格局对氮和磷的截留(-0.09 mg·L^-1)比“林-田”景观格局(-0.185 mg·L^-1)明显,且在时间上呈现雨季大于旱季,在空间上呈现梯田>村寨>森林的特征;(2)“林-田”景观格局的水体富营养化水平(Ⅲ级)高于“林-寨-田”景观格局(Ⅱ级),且在时间上呈现旱季大于雨季,空间上呈现梯田>森林的特征;(3)梯田既是“源”景观也是“汇”景观,截留量0.08-0.18 mg·L^-1,水体富营养化水平Ⅳ级(62.025≤EI≤66.19),表明梯田截留明显且局部已富营养化.建议对景观格局进行优化,构建“沟渠-水塘-梯田”湿地结构,控制污染物排放量.

The vertical landscape pattern of"forest-village-terrace-water system running through"of Honghe Terraces affects the migration and transformation of nitrogen and phosphorus.In order to reveal its internal connection,the surface water in the two landscape patterns of the Red River Terrace"Lin-Zhai-Tian"and"Lin-Tian"was taken as the research object.In December 2017(dry season)and June 2018(rainy season),a total of 18 water samples were collected for determination of total nitrogen(TN)and total phosphorus(TP),and their spatiotemporal characteristics were analyzed.The interception and the eutrophication index(EI)were used to evaluate the interception and eutrophication of the water.The results showed that nitrogen and phosphorus sequestration and water eutrophication in the Honghe terraced fields were closely related to landscape pattern.(1)Nitrogen and phosphorus retention(-0.09 mg·L^-1)in"Lin-Zhai-Field"landscape pattern is more obvious than in"Lin-Field"landscape pattern(-0.185 mg·L^-1),and in time it presents the characteristics that the rainy season is greater than the dry season,and spatially presents terraces>villages>forests;(2)the level of eutrophication of water bodies in the"forest-field"landscape pattern(level Ⅲ)is higher than the"forest-wall-field"landscape pattern(Ⅱ Level),and in time,the dry season is greater than the rainy season,and the space presents the characteristics of terraces>forests;(3)The terraces are both"source"and"sink"landscapes.The interception amount(0.08-0.18 mg·L^-1)and the level of eutrophication(62.025≤EI≤66.19)indicate that the interception of the terraces was obvious and local eutrophication had occurred.