Study On Soil Erosion Mechanism Of The Ecoloical Rehabilitation Of Typical Karst Unit In Guizhou

The Water and soil loss is an important factor that an ecological benefit deteriorate on karst area in Guizhou,serious system is roughly the region's national economy keep,stabilization and health development.Environment is friability duo to especial geological background,and the soil erosion mechanism is a difference with other region in China.Enhance study to the water and soil loss mechanism has an important practical meaning in karst area.This study is with three different typical karst physiognomy in Guizhou,prefering to the analysis methods of soil physical and chemical properties of Nanjing Soil Research Institute Chinese Academy of Sciences, while water and soil loss survey methodology according to Water Conservancy Section criterion.There are 41 sample points in the Study Areas. From April 2006 to December 2008,to collect the basic data,field sampling and monitoring have been done nine times in April,August,December of the two years,and using GIS,EXCEL,PHOTOSHOP,SPSS11.0,etc.data analysis software for the maps and data analysis.The studying research the soil erosion mechanism and change rule on space-time from that aspect of such as Bijie tableland and mountain,Qingzhen ableland and basin and Huajiang altiplano and gorge in Guizhou karst,for make macroscopical decision of water and soil loss prevention and control previde gist of theory.the studying get to several cognition as following. (1) The vegetation and topographic and climate in natural factors are the best influence soil erosion.The results of the comparison of vegetation coverage rate and soil erosion modulus in different area,with Yachi demonstrate area in Bijie city,Hongfenghu demonstrate area in Qinzheng city,Huajiang demonstrate area in Zhenfeng and Guanling county,vegetation covering rate from 2006 to 2008 to respectively increase scope by 31.84%, 48.19%,9.01%,decreasing rate of soil erosion modulus by 22.53%, 21.61%,31.25%.Vegetation covering rate and vegetation can to protect and keep water and soil to positively correlated,and with the function of soil erosion is inversely related.The average size slope of three demonstration area are Yachi demonstrate area in Bijie city(20.917°)＞Huajiang demonstrate area in Zhenfeng and Guanling county(19.167°)＞Hongfenghu demonstrate area in Qinzheng city(15.947°),with soil erosion intensity size show consistent relations and terrain is better influence to soil erosion.The climate restricting environment of soil erosion intensity and rainfall is dominative factor to soil erosion.The research areas belong to subtropical monsoon climate with water and heat conditions are abundance,annual rainfall is from 850 to 1200mm.It is concentration distribution from April to October months. Soil erosion occurred concentrated in the period and soil erosion account for 80%.The line of erosion research of field to display that soil erosion is very weak on December in winter to April in second spring.The soil erosion intensity of karst area depends mainly on rainfall and precipitation intensity.Soil erosion with 30 minutes in the heavy rain assume significant correlated on 0.01 levels,correlation coefficient is 0.881,this shows that the rain for 30 minutes of soil erosion intensity.(2) Underground erosion mutual influenced interdependent by factors such geological and physiognomy,lithology,climate,hydrology,soil,vegetation etc.Because rock by tectonic stress produce cranny there are the main channel of fracture water to erosion carbonate rock,and strong karst formation process cause the karst dual structure of surface and underground.Be helpful for vegetation growth in humid climate condition.Vegetation can enhance soil structure stability and improve soil erosion resistance,and can inhibit the underground soil erosion.The soil physical properties of soil is an important factor of influence soil erosion.The soil of underground mechanical components is the highest levels of＜0.001 mm,generally by 41-63%,while 0.25- 0.01 mm content by 15%-45%,the soil sand content is low.Because of the soil of tiny particles was surface runoff carry into underground deposited and its more viscous grain content on＜0.001mm,to explain the surface soil by water erosion for long-term where is showed in the sand more content.(3) According to soil properties the different of karst landform cells,select the soil respiration take this an important indexes to reflects microbial activity for monitoring.Under different vegetation types of soil humidity and temperature,soil respiration intensity is different also.The changes of soil air is mainly consumption of oxygen accumulated and carbon dioxide.Soil through emit carbon dioxide to promote crop of photosynthesis.Soil of high rate of vegetation,the soil respiration intensity is better and soil respiration intensity with vegetation is correlation.Therefore,the soil respiration intensity is the indirect effects of soil erosion an important factor.The change rule of soil respiration intensity in studying area show shrub-meandow＞forest for conserving water supply＞cash tree and fruit-bearing forest＞arable land of slope＞wasteland.(4) The character of physical and chemical of soil changes evidence.The soil mechanical composition in the demonstration area is better soil sand content on＞0.05 mm,average about 40%,to show Huajiang demonstrate area in Zhenfeng and Guanling county＞Yachi demonstrate area in Bijie city＞Hongfenghu demonstrate area in Qinzheng city and with the soil erosion intensity at them same area are consistent relation,and to explain the long-term soil erosion cause the sand soil with tiny grain were washed away.Soil grain content on＜0.01 mm is general about 50%,to explain the soil to drain.Water stability granule structure total content on＞0.25mm show to Yachi demonstrate area in Bijie city＞Hongfenghu demonstrate area in Qinzheng city＞Huajiang demonstrate area in Zhenfeng and Guanling county.Water stability granule structure damage rate is the size relations Yachi demonstrate area in Bijie city＞Huajiang demonstrate area in Zhenfeng and Guanling county＞Hongfenghu demonstrate area in Qinzheng city.The soil total porosity average by 50%,capillary porosity is average by 33.10% and non-capillary porosity is average by 16.32%.The non-capillary porosity and permeability less would cause easy with strong surface runoff.The soil of saturated permeability display surface soil more than underlayer that would intensify greater frequency of soil erosion.The soil bulk density average by 1.04 g/cm~3 and the correlation coefficient of density of soil with soil erosion is 0.881.The organic matter content increase from 2006 to 2008 and its amplitude by 3.53%.So,In the process of ecological control, vegetation growth cause to changes of soil character to affecting soil fertility.