Spatial Heterogeneity of Lake Eutrophication Characteristics in the Third Topography Ladder in China

In order to clarify the spatial heterogeneity of eutrophication characteristics in different lake regions in the third topography ladder (TTL) and provide scientific evidence for lake nutrients ecologic regionalization, the main geographical factors affecting the trophic status of lakes in the TTL were analyzed, and the spatial heterogeneity of the degree of influence and mechanism affected by geographical factors discussed. The results showed that the relationships between TLI and longitude, altitude (average annual temperature, multi-annual average precipitation) fitted to square or cubic model, and the vertexes of square or cubic curve were the boundaries of Northeast Plain-Mountain and North China Plain (and the Plain of Yangtze River). Great differences existed in the responses of algal biomass to nutrients TN or TP in the three lake regions in the TTL. Responses of algal biomass to TN and TP in the Plain of Yangtze River were stronger than that in North China Plain, leading to lower mean values and discrete degrees of TN and TP and higher mean value and discrete degree of Chl-a than North China Plain. The mean values and discrete degrees of TN, TP and Chl-a in Northeast Plain-Mountain were the lowest among the three lake regions. The response of algal biomass to TP was the highest in Northeast Plain-Mountain among the three lake regions indicating the highest utility efficiencies of TP.