福建长汀河田土壤侵蚀的研究 Ⅱ.河田土壤侵蚀与侵蚀土壤

<正> 前文对河田土壤侵蚀因素进行了探讨,阐明了河田土壤侵蚀严重性的起因,实由于人为对植被的破环而引起。本文就土壤侵蚀与侵蚀土壤的类型、特点及其治理途径进行探讨。

A STUDY ON SOIL EROSION IN HETIAN,CHANGTING,FUJIAN Ⅱ.Soil Erosion and Eroded Soil

The two main types of soil erosion in Hetian are surface erosion and furrow erosion.Surface erosion may be classified into light,medium,and heavy grades according to the thickness of surface soil or subsoil left.As to the furrow erosion,by judging from the sizes and the developmental morphological characteristics,can be classified into small furrow,shallow furrow,and deep furrow.They represent the three stages of furrow erosion. Shallow furrow type occurs mostly in this district.The destructive condi- tion is so serious that almost 39.32% of the land area investigated appears this type of soil erosion.With the result of surface and furrow erosion, the relief of the moutainous area of Hetian makes so much destruction that not only soil conservation and soil fertility are mutilated,but also the reha- bitation of forestry and agriculture impeded. The sequential formation of the wear and tear in this land district is under the control of soil erosion.Types of sojl can be classitied into three categories,namely,medium organic matter red earth,rare organic matter red earth,and eroded red earth.The last category occurs in most of this area,ranging to 44.91% of the land investigated.As the degree of soil ero- sion becomes more and more in seriousness,the characteristics of soil phy- sics especially its dispersion degree,dispersion ratio all become higher, and the status of essential nutrients in the soil declines.The contents of organic matter,nitrogen,as well as phosphorous of the eroded red earth arr lowered.Taking the medium organic matter red earth as a standard foe comparision,the above three mentioned contents reach only up to the percent- ages of 10,25,and 31 respectivly. The way to control soil erosion must be done according to the regional requirements with a general plan.Slopes below 15 degrees,terraces should be constructed and planted to cash crops.Those with slopes above 15 degrees, having the original vegetation destroyed,the main problems are drought and wanting of soil fertility.Practical experiments show that the best method to employ is reforestation.After trees are planted in trenches,the trenches become a good reservior of moisture and nutrients.The water contents organic matter,nitrogen and phosphorous contents in the trench soils are usually 100% higher than the soils in the eroded slopes.Thus,theshrubt and trees in the trenches grow well.In returns,the vegetation covers the soils from drainage and acting as a biotic factor to improve the physical, chemical,and biological conditions of the soils.However,to gain success, the selection of vegetation varieties must be taken into consideration.The upper slopes are well planted to Pinus,Elaegnus,and Gleichenia,etc.;while the lower slopes should be planted to Cunninghamia and Thea intercropping with leguminous Crotafaria and Lespedeza,i.e.,a combination of trees, shrubs,and grasses.The canopy vegetation soon flourishes and covers the slopes,thus preventing soil erosion and getting back soil fertility.