【作者】 宫春明；

【导师】 陈晓燕；

【作者基本信息】 西南大学 ， 水土保持与荒漠化防治， 2009， 硕士

【摘要】 土壤是地球上生物赖以生存的基本要素之一,土地退化的日益严重成为制约人类发展的重要因素,土壤侵蚀是其中一个重要的因素。我国是世界上土壤侵蚀最为严重的国家之一,土壤侵蚀面积占国土面积的比例高达38.2%,研究土壤侵蚀的机理,有效地对其进行监控、治理已经成为全球关注的焦点国内外学者早在20世纪60年代末就开始对土壤侵蚀相关理论问题及过程机理进行研究,利用核素示踪技术定量研究土壤侵蚀速率具有常规技术无可比拟的优势,准确、快速、精确度高,越来越受到研究者的重视。本研究在对万州区陈家沟流域内的杨家沟小流域进行实地调查的基础上,选取具有代表性的20个采样点进行采样研究,结果表明:（1）小流域内¹³⁷Cs含量的影响因素很多,坡位、坡度和土地利用现状都对¹³⁷Cs的含量存在一定的影响作用,对于水田和坡耕地比较密集的地块,由于人为活动使得土壤颗粒沿坡面迁移比较频繁,造成了¹³⁷Cs含量沿坡面迁移,使得这部分地区¹³⁷Cs分布规律性不明显,而在坡顶和林地范围内,¹³⁷Cs分布规律基本符合地貌的变化规律:随着坡度增大,含量越低,坡度越小,含量越小。（2）通过¹³⁷Cs法计算出的小流域内水田的土壤侵蚀模数值比较大,由于水田坡度为0,所以理论上水田的土壤侵蚀为微度侵蚀,但是根据张信宝提出的¹³⁷Cs侵蚀模型的计算来看,水田的侵蚀模数很不规律,结果偏高,因此可能是公式中对于水田的计算存在一定的偏差,有待进一步探讨。（3）小流域内有机质分布很不平均,与土壤侵蚀模数相关性不大,但不同土地利用现状对有机质分布影响比较明显。有机质分布规律是:坡耕地＜林地＜经果林＜水田。有机质含量分布和¹³⁷Cs分布规律基本吻合。（4） ¹³⁷Cs法计算小流域土壤侵蚀量,是一种比较快速有效的预测水土流失的新方法,通过此种方法计算得出杨家沟小流域年土壤侵蚀总量为3402.12t。（5） ¹³⁷Cs含量与土壤物理性粘粒以及物理性粉粒存在一定的相关性,随着粘粒和粉粒的增多,土壤中的¹³⁷Cs含量随之增多,这是因为¹³⁷Cs主要吸附在粉粒和粘粒等微团聚体上。土壤中物理性砂粒含量越多,¹³⁷Cs含量越少。因此可以通过增加土壤团聚体来减少水土流失。更多还原

【Abstract】 Soil is one of basic factors which life beings in the earth rely on.Soil degradation increasingly restricts human development,and soil erosion is one of the reasons.China is one of the most serious soil erosion Country in the world,and the method that how to control and deal with it have been the focus of the world.Many scholars have studied the theories and mechanism of soil erosion from 1960’s.with the development of computer technique,combined GIS with RS to study soil erosion has been the advanced filed in researching soil erosion quantificationally.Using nucleus tracer technique to quantificationally research soil erosion has unsubstituted advantage,such as exactness, speediness,precision,and so on.Now more and more researchers become to pay attention them.Based on the field survey advanced position and the surrounding area of Yang jiagou small watershed of Chen jiagou watershed in Wanzhou district,this study selected 20 typical soil sampling points.The conclusions of analysis are as follows.（1） There are a lot of factors that affect the ¹³⁷Cs content in small watershed,like slope position,slope,and land use status.As for lands that paddy field and slope soil,¹³⁷Cs content is forced to change because of humane activities.And within the spectrum of top of slope and woodland,the distributing rules of ¹³⁷Cs almost suit that of the physiognomy—the bigger the gradient is,the less the content is,and vice versa.（2） The soil erosion modulus is bigger than that is calculated through nuclide tracing method. And as the slope of paddy field equals zero,the grade scale of soil erosion intensity belongs to micro degree erosion theoretically.However,most of the paddy field locate on the bottom of this area, which is very close to the riverway;and the soil there is comparatively lossen.That is to say,when the rain season comes,as the water level raises,most soil would be washed out,thus produces more soil erosion.（3） The organic matter in small watershed is relatively imbalanced,which has less relativity with soil erosion modulus.But different Soil Utilty Status produce different effect to the distributed of organic matter.The rule of organic matter is:slope soil＜woodland＜economic fruit forest＜paddy field.The distribution rule is almost the same to the content of organic matter.（4） It is a very effective and efficient way to use nuclide tracing method work out the soil erosion quantity of the small watershed.Though this way,we can get that the total amount of Yangjiagou is 3402.12t.（5） The content of ¹³⁷Cs has certain pertinence with soil physical clay and soil physical silt.As the manifold of the clay and silt,the content of ¹³⁷Cs in the soil gets more,for the ¹³⁷Cs are mostly found in microaggregate such as clay and silt,and the more the physical sand in the soil becomes, the less the ¹³⁷Cs content gets.So we could prevent the water loss and soil erosion from increase soil aggregate by using this method.更多还原