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 factor