| Land,as important natural resource,is thebasis for human survival and development.The way of land use has an important impact on soil quality and even the entire ecosystem.TuMoChuan plain is a typical salt-affacted area in the semi-arid regionof inland,and is also one of the concentrated areas of saline-alkali soil distributedin Inner Mongolia.As a very sensitive and fragile soil resource,saline-alkali soil iseasily affected by land use mode to a higher degree than other soil types.Therefore,it is of great significanceto studythe impact of land use mode on the quality of saline soil.Itis beneficial for thescientific management and rational development and utilization of saline soil resources,optimization of land use mode,maintenance of land productivity,improvement of regional ecological environmentand promotion of sustainable development of agriculture and animal husbandry.Taking different land use patterns of TuMoChuan plain saline soil(wasteland,forestland,farmland,pastureland,improved land)as the research object,the effects of land use ways on soil characteristics was investigated in this studythrough field sampling and laboratory analysis,and combined commonanalysis and moderrn biological technology.The physical properties of soil including moisture,salinity,nutrients,soil aggregates and aggregates organic carbon and microbial characteristics were determined in thestudy.Themain results are as follows:(1).With the increase of soil layer depth the bulk density increases gradually in various land use modes,the range of variationis between 1.27g·cm-3 and 1.81g·cm-3.The bulk density of 0-20cm soil surface layer is shown as wasteland>pasture land>improved land>farmland>forestland.The capillary pore of soil in various land use modes rangesbetween 26.02%and 31.61%,and the size of which is improved land>forestland>pastureland>farmland and>wasteland.The non-capillary pore range is between 7.72%and 12.14%.The total pore range is between 33.77%and 42.73%,which showed that forestland was the largest and wasteland the smallest.The soil watercontent is between 4.35 and 19.93%,and the value exhibited as forestland>in farmland>in improved land>in pastureland>wasteland.The seasonal dynamics of soil watercontent in wasteland,farmland,pastureland and improved land is consistent,whichshowed asin October>in August>in December>in May;Thesoil watercontent in forestland is in October>in August>in May>in December.(2).The pH of soil in various land use modes ranged from 7.66 to 10.56.Except that the wasteland increased first and then decreased with the increase of soil depth,other land use modes increased with the increase of soil depth.The change range of total soil salinity is between 0.50g·kg-1-8.97g·kg-1.With the increase of soil depth,the total soil salinity in wasteland,farmland and pastureland first increase and then decrease,while improved land and forestland decrease with the increase of soil depth.The variation range of soil alkalinity is between 8.68%and 70.15%.With the increase of soil depth,the soil alkalinityin wasteland,farmland,pasture and forestland first increase and then decrease,while improved land first decreases and then increases with the increase of soil depth.The pH value,total salinity and alkalinity of soil are expressed as wasteland>improved land>pastureland>forestland>farmland.(3).The organic matter,total nitrogen,available nitrogen,ammonium nitrogen,nitrate nitrogen,rapidly available phosphorus and readily available potassium in soil decrease with the increase of soil depth in varnous land use modes,which showedobvious surface enrichment.Compared with wasteland,other land use modes improved soil nutrient content to varying degrees.(4).Thesoil aggregates of different particle sizes are different under different land use patterns.The aggregates number of 0.5-1mm and 1-2mm size fraction is the lowest.The aggregates larger than 5mm dominated the soil aggregates in wasteland,forestland and farmland,accounting for more than 50%.Soil aggregate organic carbon decrease with the increase of particle size,which content ranges 1.16-15.51 g·kg-1.Thesoil organic carbon reserves is between 43.84?82.92t·hm-2,and theressrves is forestland>farmland>pastureland>improved land>wasteland.(5).The number of soil microorganisms decreased with the increase of soil depth under various land use modes,among which the number of bacteria was the highest,accounting for 42.9%to 72.5%of the total number of microorganisms,followed by actinomycetes,accounting for 4.4%to 23.3%,and fungi was the lowest,accounting for 0.06%to 0.31%.The total number of soil microorganisms expressed as farmland>forestland>pasture>wasteland>improved land.(6).The amount of unique OTU(Operational Taxonomic Units)to different soil samples showed in farmland>in wasteland>in forestland>in improved land>in pastureland.The abundance of bacterial species in farmland,pastureland and forestland was higher,and that in wasteland was the lowest.From the perspective of bacterial community structure and diversity at the phylum level,both actinomycetes and proteobacteria account for a larger proportion,which plays an important role in soil microbial community structure under different land use modes.At the genus level,compared with other land use patterns,Arthrobacter and Kaistobacter were the dominant groups in pastureland,followed by farmland and forestland.The composition of bacterial community in pastureland,forestland and farmland was similar,and the structure of community in wasteland and improved land was similar.(7).Indexes for soil quality evaluationof the TuMoChuan plain include 2-5mm aggregate organic carbon,total salinity,saturationmoisture content,bacteria numbers,ammonium nitrogen and chloride ions,whichweights were 0.35,0,23,0.17,0.10,0.08 and 0.06,respectively.The results based on foursoil quality indexes showed that the indexes of farmland,forestland and pastureland are higher.However,consideredthe basic situation of agriculture and animal husbandry production in this regionand arable land reserve resources,it is proposed that the farmland and pasture land are suitable land utilization modes for salinized wasteland developmentin the area which is not only beneficial forthe agriculture production,but also forthe soil quality improvement. |
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