Based on data from 148 hydrometric stations in the Yellow River Basin,an analysis of regional scale relationship,or the relationship between specific sediment yield and drainage basin area,has been undertaken in the s...Based on data from 148 hydrometric stations in the Yellow River Basin,an analysis of regional scale relationship,or the relationship between specific sediment yield and drainage basin area,has been undertaken in the study area of the Loess Plateau.For different regions,scale relationship in log-log ordinate can be fitted by two types of lines:straight and parabola,and for each line,a function was fitted using regression analysis.The different scale relationships have been explained in terms of the difference in surface material distribution and landforms.To offset the scale-induced influence,calcu-lation has been done based on the fitted functions,in order to adjust the data of specific sediment yield to a common standard area.Based on the scaled data,a map of specific sediment yield was con-structed using Kriging interpolation.For comparison,a map based on the un-scaled data of specific sediment yield was also constructed using the same method.The two maps show that the basic pattern of specific sediment yield was basically the same.The severely eroded areas(Ys>10000 t km-2a-1)were at the same locations from Hekouzhen to Longmen in the middle Yellow River Basin.However,after the adjustment to a common standard area,the very severely eroded area(Ys>20000 t km-2a-1)became much enlarged because after the adjustment,all the values of Ys in the lower river basin in those regions became much larger than before.展开更多
Under the background of large-scale ecological restoration, China's southwestern karst region has become a hotspot of global vegetation cover “greening” in the past 20 years. However, because of geological const...Under the background of large-scale ecological restoration, China's southwestern karst region has become a hotspot of global vegetation cover “greening” in the past 20 years. However, because of geological constraints, it is difficult to restore the forest landscapes in some areas. It is urgent to understand the impacts of human disturbances during the historical period on the difficult-to-forestation rocky-desertification areas of the karst region in order to guide future afforestation. In this study, we quantified the changes of specific sediment yield in typical karst depressions over the past 500 years by using ^(137)Cs,^(210)Pb, and ^(14)C dating methods in karst depressions, and identified the main human disturbances related to historical erosion and sedimentation by combining with historical data. The results showed that the erosion and sedimentation of the three depressions in 1921–1963 were significantly higher than that in 1963–2021, and the sedimentation rate(0.64–1.33 cm a^(-1)) and the specific sediment yield(2.51–13.11 t ha^(-1)a^(-1)) during Ming and Qing dynasties(1504–1812) were higher than the sedimentation rate(0.26–0.95 cm a^(-1)) and specific sediment yield(0.95–6.99 t ha^(-1)a^(-1)) in the recent century(1921–2021). Reconstruction data and literature from the Ming and Qing dynasties show an empirical link between changes in population, arable land, food, forest area,and deforestation events during the same period. It was found that the population and arable land in Guangxi increased more than three-fold and the forest area decreased significantly in the 17th century after the migration of the Yao ethnic group and the introduction of maize to the region, which may be the main reason for intensifying the erosion of depressions. This study is of great significance to understanding the evolution history of rocky desertification in this region and to answer the potential of afforestation.展开更多
基金Supported by the National Natural Science Foundation of China and the Yellow River Water Conservancy Commission(Grant Nos.50239080 and 40271019)
文摘Based on data from 148 hydrometric stations in the Yellow River Basin,an analysis of regional scale relationship,or the relationship between specific sediment yield and drainage basin area,has been undertaken in the study area of the Loess Plateau.For different regions,scale relationship in log-log ordinate can be fitted by two types of lines:straight and parabola,and for each line,a function was fitted using regression analysis.The different scale relationships have been explained in terms of the difference in surface material distribution and landforms.To offset the scale-induced influence,calcu-lation has been done based on the fitted functions,in order to adjust the data of specific sediment yield to a common standard area.Based on the scaled data,a map of specific sediment yield was con-structed using Kriging interpolation.For comparison,a map based on the un-scaled data of specific sediment yield was also constructed using the same method.The two maps show that the basic pattern of specific sediment yield was basically the same.The severely eroded areas(Ys>10000 t km-2a-1)were at the same locations from Hekouzhen to Longmen in the middle Yellow River Basin.However,after the adjustment to a common standard area,the very severely eroded area(Ys>20000 t km-2a-1)became much enlarged because after the adjustment,all the values of Ys in the lower river basin in those regions became much larger than before.
基金supported by the National Natural Science Foundation of China (Grant Nos. U20A2048 & 41930652)the National Key Research and Development Program of China (Grant No. 2022YFF1300700)。
文摘Under the background of large-scale ecological restoration, China's southwestern karst region has become a hotspot of global vegetation cover “greening” in the past 20 years. However, because of geological constraints, it is difficult to restore the forest landscapes in some areas. It is urgent to understand the impacts of human disturbances during the historical period on the difficult-to-forestation rocky-desertification areas of the karst region in order to guide future afforestation. In this study, we quantified the changes of specific sediment yield in typical karst depressions over the past 500 years by using ^(137)Cs,^(210)Pb, and ^(14)C dating methods in karst depressions, and identified the main human disturbances related to historical erosion and sedimentation by combining with historical data. The results showed that the erosion and sedimentation of the three depressions in 1921–1963 were significantly higher than that in 1963–2021, and the sedimentation rate(0.64–1.33 cm a^(-1)) and the specific sediment yield(2.51–13.11 t ha^(-1)a^(-1)) during Ming and Qing dynasties(1504–1812) were higher than the sedimentation rate(0.26–0.95 cm a^(-1)) and specific sediment yield(0.95–6.99 t ha^(-1)a^(-1)) in the recent century(1921–2021). Reconstruction data and literature from the Ming and Qing dynasties show an empirical link between changes in population, arable land, food, forest area,and deforestation events during the same period. It was found that the population and arable land in Guangxi increased more than three-fold and the forest area decreased significantly in the 17th century after the migration of the Yao ethnic group and the introduction of maize to the region, which may be the main reason for intensifying the erosion of depressions. This study is of great significance to understanding the evolution history of rocky desertification in this region and to answer the potential of afforestation.
