The influences of land-use changes on the absorbed nitrogen and phosphorus loadings in the drainage basin of Lake Chaohu, China

摘要

The influences of land-use changes on the absorbed nitrogen and phosphorus loadings in the drainage basin of Lake Chaohu were investigated in this study. Based on the principle of universal soil loss equation, a model was developed for estimating the annual mean soil erosion amount from 1989 to 2008 in Chaohu basin. Applying the GIS and soil data, the absorbed nitrogen and phosphorus loadings were stimulated and quantified for three-time stage (1989-1995, 1996-2000, 2001-2008). Furthermore, the influences of historical land-use changes on the absorbed nitrogen and phosphorus loadings were assessed. The results indicated that the absorbed nitrogen and phosphorus loadings of drainage basin have an obvious spatial difference in the three-time stage because of the different characteristics of climate and geology. Temporally, the absorbed nitrogen and phosphorus loadings in the second stage (1996-2000) are less than the one in the first (1989-1995) and third stage (2001-2008), and the load of third stage is the largest, which was mainly impacted by rainfall and land-use change. Forest and grass can act as a source for the load of absorbed nitrogen or absorbed phosphorus. The paddy land and residential land in these areas act as sinks or transformation zones as expected. Other factors such as slope and geology also play important roles in the transport of nutrients and sediments to streams.