| Hebei Bashang is one of the important regions for controlling Beijing-Tianjin sandstorm source.Due to the special climate and irrational land use and so on,soil erosion problem is very serious in Hebei Bashang.After going through population growth,land reclamation and returning farmland to grassland and forestry and other acitivities,the land use in this region has been formed into three kinds including natural grassland,farmland,and returning-farmland in inter-distribution state.At present,there are less comparative study among three kinds land in Hebei Bashang.By field investigation and lab test,this master thesis plans to have a series of comparative analysis on the interrelationship among soil physicochemical properties,dry-soil aggregate stability(DASt)and soil erosion degree(EF).The purposes are to quantify soil wind erosion and furthermore to have some advice for controlling wind erosion in Hebei Bashang.The main ideas as follows:(1)by comparing the three different land use types of soil sieving and rotary sieving,it is found that the soil with fine and easily damaged soil is destroyed by flat screen.Therefore,we should choose the rotary sieve to carry out the analysis experiment.(2)By significance test,there is significant difference for farmland and natural grassland between DASt and EF(P<0.05);however,it is not significant about difference between farmland and returned farmland(P=0.387),natural grassland and returned farmland(P=0.077);the difference of erodibility for farmland is higher than natural land and returned farmland.(3)There are common results for some sorts of EF(soil erodibility)and DASt(soil-dry aggregate stability): natural grassland>farmland>returned farmland;these results shows that land cover has an important impact for soil erodibility,the higher soil surface cover is,the stronger soil erodibility is.(4)There are different content for clay,silt and gravel in different soil.By soil test analysis,there are common results for clay and silt content in three soils: natural grassland>returned farmland>farmland;however,gravel content is:farmland>returned farmland>natural grassland,which shows tillage has an important impact on soil texture..(5)A analysis on the average content of organic matter among three soils is:natural grassland>returned farmland>farmland,the minimus content is: natural grassland>returned farmland>farmland,the maximum content is: returned farmland >natural grassland> farmland;The average content of total nitrogen is: natural grassland>returned farmland> farmland,the minimum content is: natural grassland> farmland>returned farmland,the maximum content isreturned farmland>natural grassland >farmland >;The average content of calcium carbonate is:natural grassland > returned farmland >farmland,the minimum content is: natural grassland >farmland > returned farmland,the maximum content is: returned farmland > natural grassland > farmland.(6)There are the significant correlationship among the indexes of DASt,EF with gravel content and average paiticle size in farmland,natural grassland and returned farmland.DASt and EF is significant difference between agriculture land and natural grassland(P<0.05),while no significant difference for DASt and EF between natural grassland and returned farmland,returned farmland and farmland.The value of EF and DASt sorts: natural grassland>returned farmland>farmland;the average size sorts:farmland>returned farmland>natural grassland;Soil clay and silt content for mechanical compositon sort:natural grassland>returned farmland>farmland,gravel content sort:farmland>returned farmland>natural grassland;soil organic matter and total nitrogen content sort:natural grassland>returned farmland>farmland;There are significant correlation among DASt and EF with gravel and average particle size,a high significant negative correlation between organic matter and total nitrogen content with DASt in natural grasssland,and a significant negative correlation between EF with organic matter and total nitrogen in natural grassland,returned farmanland and farmland.(7)In a word,the research results show that the grassland and returned farmland have higher soil fertility,but also higher wind erosion potentiality at soil surface in Hebei Bashang.it is necessary for reducing wind erosion to take countermeasures by restricting grassland reclamation,reforestation,increasing vegetation cover. |
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