Regional differences in physiographical,climatological and morphological effects on lake trophic status in China

Correlation analysis and curve estimation were used to explore the relationships between eutrophication parameters and natural factors in a large scale using data from 145 lakes across China.Lake eutrophication parameters including total nitrogen(TN),total phosphorus(TP),chemical oxygen demand(CODMn),chlorophyll-a(Chla),Secchi depth(SD),and trophic level index(TLI) were collected and monitored for the period 2008~2010.Natural factors included three of geographic location,two of lake morphology,and three of climate variables.Correlation analysis in SPSS was used to investigate the key drivers of lake eutrophication.The results showed that TLI was negatively related to lake depth and elevation,and positively related to longitude and accumulated temperature(0℃).Chl a was negatively related to lake depth and positively related to annual temperature and accumulated temperature(0℃).Curve estimation indicated that TLI exhibited power function relationships with lake depth and longitude,and exponential function relationships with elevation and accumulated temperature(0℃).The results also showed that oligotrophic lakes were generally located in higher altitude(1000m) and lower longitude(105°).The depth of oligotrophic lakes was deeper than 30m,with annual precipitation less than 1000mm and accumulate temperature(0℃) lower than 5400 ℃.