Agricultural landscape pattern optimization of high intensive agricultural areas based on water quality control
LIHongqing1,, LIULiming2,, ZHENGFei1, ZHAOYaoyang1 1. College of public administration, Hohai university, Nanjing 210098, China2. College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China 通讯作者:通讯作者:刘黎明,E-mail:liulm@cau.edu.cn 收稿日期:2017-05-26 修回日期:2017-10-9 网络出版日期:2018-01-20 版权声明:2018《资源科学》编辑部《资源科学》编辑部 基金资助:中央高校基本科研业务费专项资金(2015B13614)国家自然科学基金重点项目(41130526) 作者简介: -->作者简介: 李洪庆,男,山东烟台人,博士,讲师,主要研究方向为土地利用环境风险控制与景观生态。E-mail:lihongqing163@126.com
关键词:景观格局;水环境质量;回归模型;综合评价 Abstract Agricultural non-point source pollution control has become a bottleneck for sustainable development especially in high intensive agricultural areas in China. Therefore, maintaining economic growth along with water quality improvements is a great challenge for policymakers. Taking Jinjing Town as a case study, we first analyzed water quality dynamics at spatial and temporal scales based on pollution monitoring data. Then, three different width buffer areas along the river were drawn to analyze the correlation between landscape pattern and water quality pollutions according to Pearson's correlation coefficient analysis; catchment was chosen as the suitable scale, and four landscape types forest, tea garden, paddy land and residential were chosen as major landscape parameters. A multiple regression analysis model was adopted to build the relationship between landscape pattern characteristics and water quality pollution for NO3--N, NH4+-N and TN for each season. According to the results, we designed agricultural landscape pattern modes from three aspects, one is landscape pattern optimization by changing land use types, shape and area; another is raising sanitary wastewater and solid waste treatment rate; and the third is livestock industry adjustment by livestock amount control. The assessment results show that water quality improves effectively and nitrogen pollutant concentration meets level V of environmental quality standards for surface water in the new landscape scenario. Biodiversity benefits, agricultural economic value, ecosystem service value and household net agricultural income are higher than in 2010. The relationship model method proposed here not only verifies the relationship between landscape pattern and water quality, but supports landscape pattern design. These landscape pattern optimization results will assist agricultural sustainable development and environmental protection planning for decision-makers.
本研究案例区为湖南省长沙市金井镇(27°55'N-28°40'N,112°56'E-113°30'E)(图1),位于洞庭湖粮食主产区,面积为13 440hm2,其中耕地面积为2313hm2,地貌类型以丘陵为主,属于亚热带季风湿润气候,雨水较为集中,主要河流为金井河与脱甲河。金井镇是国家建设部小城镇建设试点镇,是长沙县工业强镇、农业重镇和商贸中心,融入长沙市“半小时经济圈”,2015年农民人均纯收入约为11 000元,农产品生产及加工主要为稻米、茶叶和蔬菜。 显示原图|下载原图ZIP|生成PPT 图1金井镇土地利用现状及集水单元划分 -->Figure 1Land use and sub-watershed of Jinjing Town -->
确定空间尺度,即确定合理的研究单元。污染物通过地表径流、地下淋溶等方式汇集到河流中,造成水体污染,因此景观构成及其与河流间的距离是影响水环境质量的关键因素。作为污染物主要来源的农田、居民点大部分处于丘陵底部且沿河流分布,故以河流为中心,河流两侧250m、500m和750m距离构建缓冲区,其面积分别占总流域面积的34%、57%和72%。在距离为500m的缓冲区内,面积比例已占稻田总面积的75%、茶园的47%、住宅的73%,并且涵盖了稻田、茶园、林地、住宅、道路、水面等所有的景观类型,所以缓冲区距离分级设置合理。利用SPSS软件分析景观结构、布局与水环境质量的相关性,表2中只列出具有显著相关性的4种景观类型。 Table 2 表2 表2不同缓冲区景观类型与水污染物浓度相关性系数分析 Table 2Pearson's correlation coefficients between landscape types and water quality pollution in different buffer areas
景观格局指数是景观结构与格局的数量化表达,能够反映出一定的生态意义。不同景观类型面积比例(P)对水环境质量影响是不同的,2、9集水单元林地组成面积较大,其污染物浓度明显偏低;最大斑块指数(LPI)有助于确定优势景观类型,河流下游的8、14集水单元耕地斑块面积最大,则优化农业景观格局时应重点调整耕地;斑块密度(PD)和边缘密度(ED)能够反映出景观破碎度和均匀度,一般景观越破碎、类型越复杂、斑块分布越零散,污染物输出越多[24],例如5、7集水单元的茶园、住宅景观破碎化较重,耕地边缘密度大,说明污染源数量增多并且污染物从耕地输出的范围变广,导致水环境质量差。因此本文选取上述4种景观格局指数作为自变量,NO3--N、NH4+-N、TN污染物浓度作为因变量,采用多元线性逐步回归法,模拟了景观格局指数与各污染物浓度在不同季节的关系模型,结果如表3所示。 Table 3 表3 表3景观格局指数与水环境质量关系回归方程 Table 3Regression equations for the water quality variables against the landscape metrics
水环境质量控制作为景观格局优化的主要目的,始终贯穿整个过程,优化后水环境质量如图3所示,结果显示整个流域的水污染物季节平均浓度均低于基准年。 显示原图|下载原图ZIP|生成PPT 图3水污染物季节平均浓度对比分析图 -->Figure 3Comparative analysis of water pollutant average concentration by season -->
本文以洞庭湖高集约化农业区金井镇为案例,分析了景观格局和水体污染特点,构建了农业景观格局与水环境质量回归关系模型,提出基于水环境质量控制的景观格局优化模式,优化后景观格局发生相应变化,水环境质量提升,同时农业经济效益和生态系统服务价值增加,满足经济和生态环境协调发展。本文提出的景观格局优化模式能够为农业规划、生态环境保护政策制定、自然资源管理提供科学依据。 影响水环境质量的因素很多,相关模型涉及大量的参数变量,例如水文、气候、土壤、地形等,考虑到在同一流域一定时期内景观格局、农户行为、自然条件等变化较小,本文从景观生态学角度出发,提出景观格局指数和污染物浓度回归模型构建方法。此方法数据容易获取,方法相对简单,能够合理地评价和预测水环境质量,适用于自然环境相对稳定的小流域地区。 虽然本文通过回归方程构建了景观格局与水环境质量关系,但是由于案例区为小流域,污染采样点位相对较少,对模型模拟精确性具有一定的影响。在景观格局优化过程中,丘陵区质量较差的耕地全部退耕还林,导致耕地面积急剧减少,粮食总产量下降较多,在其他粮食主产区或者耕地较少的地区实现难度较大,操作上具有一定的限制性,同时提出的土地整理措施,实际中面临权属问题、资金问题等,有待在实践中进一步完善。 The authors have declared that no competing interests exist.
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