中国中东部平原亚热带湿润区湖泊营养物生态分区

湖泊营养物生态分区是实现湖泊分区控制的前提和基础。以中国中东部平原亚热带湿润区为案例区,根据区域特点,从自然地理要素、生态系统和人类活动三方面建立指标体系,对各指标进行归一化得到各指标数据的分值;采用AHP方法确定各指标的权重值,结合各指标分值计算栅格尺度上湖泊营养物生态分区综合评价分值;根据研究区域DEM数据划分小流域,将栅格尺度的湖泊营养物生态分区综合评价分值投影到小流域尺度上,采用双约束空间聚类算法对小流域尺度上湖泊营养物生态分区评价分值进行聚类得到湖泊营养物生态分区结果。结果表明:(1)AHP可以用来确定复杂指标体系中各指标的权重,适合用于确定湖泊营养物生态分区指标体系中各指标的权重;(2)采用双约束空间聚类进行湖泊营养物生态分区,保证了分区结果在空间上的连续性和评价分值上的接近性;(3)根据自然地理条件、土地利用和人类活动强度的不同,可以将中东部平原亚热带湿润区划分为长江中下游平原湖区、湘赣平原丘陵湖区、湘渝山地湖区、四川盆地湖区、川西—大巴山山地湖区5个营养物生态区。

Lake nutrient ecosystems in the east-central moist subtropical plain of China

Our study objective was to investigate the factors creating spatial variation in lake nutrient concentrations, and the formation of ecological zones. Nutrient enrichment (eutrophication) has been observed in lakes in China, and it can be caused by multiple factors including physical, chemical, and biological factors. Ecological zoning of lakes according to nutrient concentration can be useful for the development and application of nutrient control standards and measures specific to each zone. We studied nutrients and the effects of nutrient concentrations in the eastern Lake Plain to aid in the development of control measures by the district government. We used an index based on three aspects: physical environment, ecological characteristics and human activities. Our study area was the east-central subtropical plains of China. The physical environment factors in the index, which were considered as most important for the ecological effects of nutrients, included annual precipitation, annual temperature, elevation, landform type, soil nitrogen and soil phosphorus content. Ecological characteristics that were included were the proportions of forest land, grassland, water area and unused land. In terms of human activities, we selected the proportions of developed land and cultivated land, and the specific proportion of GDP and population density. For each of the physical, ecological and human indices, we normalized the index data to obtain an index evaluation score. The analytic hierarchy process (AHP) method was used to determine the weight of each index and evaluate the importance of different scores in a matrix that made pairwise comparisons of the evaluation scores of each index. The watershed of the lake was divided into small partitions according to a digital elevation model and the total score on the grid scale was projected onto the small watershed partitions using dual-constrained spatial clustering. The results from the clustering analysis provide some preliminary results on the nutrient zonation within the lake. Based on these results, and the views of economic experts, the results of the initial partition appropriate adjustments, Case finally get the lakes nutrient ecoregion results. We suggest that AHP is a useful method that allows policymakers to develop rationales and engage in quantitative decision-making. Particularly for complex systems such as the lake nutrient system, AHP can be used to decide the relative importance of the multiple factors involved. Ecological zonation of lakes by nutrient concentration as revealed by the dual-constrained spatial clustering algorithm ensures spatial continuity and score proximity in the partition results. The spatial clustering analysis as applied to the two bound lake ecological zones of this paper can also be used in other regions or at a national scale to define the zonation in lakes. Using the nutrient level data from this study, the east-central subtropical plain of China can be divided into the middle and lower lake plains of the Yangtze River ecoregion, the hilly plains Lake ecoregion in Hunan and Jiangxi, the Hunan and Chongqing Mountain Lakes ecoregion, the Lakes Basin ecoregion, and in western Sichuan, the Daba Mountain Lakes ecoregion.