干旱区生态环境知识资源中心

In this study, we use reservoir deposits to reconstruct sediment yields over the past 50 years from the Quananzi catchment, a small limestone catchment in the Yimeng Mountain region, China. Three sediment cores were collected from the reservoir, and the chronology of each core was established using Cs-137 and Pb-210(ex) dating. The area-specific sediment yields (SSY) for different time periods since dam construction were estimated from each core by referring to the original capacity curves of the reservoir. The estimated SSY from the Quananzi catchment in each core for each period ranged between 0.9 +/- 0.3 and 2.6 +/- 0.9 t ha(-1) y(-1), with a mean value of 1.8 +/- 0.6 t ha(-1) y(-1) which is low compared with reported SSY from catchments worldwide. The mean value was only about 1/7 of the equivalent value reported from the Jiangzhang catchment in the granite area of the Yimeng Mountain region. This low SSY reflects the shortage of erodible Luvisols, resistance to erosion, and the limited effect of human disturbance in this small limestone catchment. The decrease in SSY from 1959 to 1972 suggests that the effect of the deforestation that occurred in 1958 on soil erosion decreased with time. The continual increase of SSY through the two subsequent periods after 1972 reflects the expansion and intensification of cultivation during this time. However, the decreased SSY over the latest period of 1998-2012 can be related to the limitations imposed by the karst landscape on cultivation, and to the impact of increasing numbers of residents leaving the area since the end of the 1990s to become temporary migrant workers elsewhere, resulting in a decrease in human activity in the area. Overall, the trend in SSY reflects the general history of changing human disturbance in this small limestone catchment over the past 50 years. The results indicate that reservoir deposits provide a means of estimating the historical sediment yields from a karstic environment.