三江源区东西样带土壤侵蚀的

运用~(137)Cs和~(210)Pb_(ex)联合示踪技术,考察青藏高原三江源区东西样带~(137)Cs和~(210)Pb_(ex)面积浓度的背景值和变化特征,以及东西样带土壤侵蚀速率、分布特征和主要影响因素. 结果表明:①青藏高原三江源区东西样带~(137)Cs和~(210)Pb_(ex)面积浓度背景值分别为453～1 714和2 612～7 377 Bq/m~2,~(137)Cs和~(210)Pb_(ex)背景值从西向东样带随海拔高度的变化差异明显.~(137)Cs(x)和~(210)Pb_(ex)(y)面积浓度的背景值区域分布呈显著线性相关,相关性关系式为y=3.587 2x+1 463.4,R2=0.951 7.②长江源区沱沱河~(137)Cs的示踪结果表明,以沱沱河为中心的长江源区是典型的风蚀区,年侵蚀速率2.5 t/(hm~2·a),该区是青藏高原重要的沙尘暴源区之一.③黄河源区玛多典型坡面~(137)Cs和~(210)Pb_(ex)的示踪结果表明,近40年来,玛多畜牧业为主的人类活动造成的土壤扰动比自然因素的影响大.④玛沁东倾沟乡和军牧场的比较研究结果表明,玛沁东倾沟乡高山草甸的水土保持效果较好,而玛沁军牧场的畜牧业活动造成了地表土壤的强烈扰动.⑤玛沁军功镇典型水蚀地貌土壤剖面~(137)Cs和~(210)Pb_(ex)的结果表明,20世纪50-60年代,该区的极端暴雨事件导致了严重的水土流失,土壤剖面中出现~(137)Cs和~(210)Pb_(ex)的空白区. 植被破坏导致玛沁军功镇出现了严重水蚀,净侵蚀速率为8.0 t/(hm~2·a).⑥近40年来,随着人类活动的加剧和全球气候变暖,导致青藏高原三江源区出现了沙尘暴的传输源地.

Study of Soil Erosion on the East-West Transects in the Three-Rivers Headwaters Region Using 137Cs and 210Pbex Tracing

A combination of ~(137)Cs and ~(210)Pb_(ex) tracing is applied to ascertain the background value and change characteristics of ~(137)Cs and ~(210)Pb_(ex), soil erosion rate, distribution characteristics and main influencing factors of the East-West transects of the Three-Rivers Headwaters region of the Tibetan Plateau. The results indicate that: (1) in the East-West transects of the Three-Rivers Headwaters region of the Tibetan Plateau, the background values of ~(137)Cs and ~(210)Pb_(ex) are in the range 453-1,714 and 2,612-7,377 Bq/m~2, respectively. With changes in elevation of the East-West transects, differences in the background values of ~(137)Cs and ~(210)Pb_(ex) are evident. The regional distribution of ~(137)Cs (x) and ~(210)Pb_(ex) (y) background values shows significant correlation;the equation of the correlation is y=3.587,2x+1,463.4, R2=0.951,7. (2) The ~(137)Cs tracing result in the Tuotuo River at the Changjiang headstream region indicates that the Changjiang headstream region centered by the Tuotuo River is a typical wind erosion area, with soil erosion rate of 2.5 t/(hm~2·a). This area is one of the important sources of dust storms on the Tibetan Plateau. (3) The results of ~(137)Cs and ~(210)Pb_(ex) tracing in the Maduo typical slope at the Yellow River headstream region indicate that in the last 40 years, livestock-based human activities in Maduo have caused more disturbance to the soil than the impact of natural factors. (4) Comparative study between Dongqinggou and Junmuchang in Maqin indicates that the alpine meadow in Dongqinggou is more effective in soil and water conservation than other vegetation studied, and the animal husbandry activities in Junmuchang have caused serious disturbance to the surface soil. (5) In the Jungongzhen region of Maqin, the ~(137)Cs and ~(210)Pb_(ex) results of soil profile from a typical site with serious water erosion show that the lack of ~(137)Cs and ~(210)Pb_(ex) was caused by heavy rain during extreme weather events in the region during the 1950s to 1960s. The water erosion caused by the destruction of vegetation in the Jungongzhen region of Maqin is serious;the erosion rate is 8.0 t/(hm~2·a). (6) In the past 40 years, increased human activity and global warming have lead to the emergence of the sand-dust source regions in the Three-Rivers Headwaters region of the Tibetan Plateau.