Study On Features Of Soil Quality In The Dry-hot Valley Of Jinsha River

Aimed at the frontier problem of the dry-hot valley's ecological constructional requirement and sylvicultural and pedological research,using the theories of pedology restoration ecology and microbiology,taking on the dry-hot valley of Jinsha River research object,choosing grass land on different land use type and elevation as the sample area,through collecting the history data,outdoor's investigation and analytic determination of soil sample,to study the features of variation,discuss how this factors reflect and indicate dry and wet season and establish study area soil quality evaluating index system,then with statistics method putting forward the main sensitive factor among soil quality,thus we can fast meet nation's requirement of ecological construction and environmental effect evaluation,sequentially increasingly provide theoretic and practical sustain to this area ecological reconstruction. The main results are as follows:(1)The soil quality features of variation under different land use mode in the dry-hot valley.â‘ Soil physico-chemical properties:After significant change in soil physiochemical properties after natural water candlenut forest being changed into other land use types, the dry-hot valley's content of soil organic,total nitrogen,total phosphorus and available nitrogen obviously decrease,all in all the impact on soil physiochemical properties was relatively small after transforming to leucocephala land and abandoned grassland.Composite index of soil properties after the natural candlenut forest changing into other land use types showed a decrease to varying degrees, its decline from small to large order is grass land> leucocephala land> sugarcane land>corn land> pepper land>mulberry land. The more disturbed by man, the more destructive influence on soil quality, so one of the important measures to improve the soil quality is to increase the return of the amount of soil material in this region.â‘¡Soil microbial biomass and microbial respiration:With natural water candlenut forest being changed into other land use types, soil microbial biomass and microbial respiration totally appear the tendency of reducing, especially grass land and leucocephala land are least. Seasons changes has different degree effect, among that soil microbial biomass and microbial respiration among wet season is higher than dry season.â‘¢Soil enzymatic activities:After land use types changes,there is obviously change in soil enzyme activity generally speaking the content of urease,ellulose and Phosphatases notably reduce,especially the degree of abandoned grassland leucocephala land are less. SEI shows different degree decreasing as land use types changing, its decline from small to large order is leucocephala land,natural grass land,orn land,pepper land,sugarcane land,mulberry land.Seasons changes has different degree effect,soil enzyme activity and SEI are higher in wet season than dry season.(2) Changing rules of soil quality under different elevation in the dry-hot valley.â‘ Soil physico-chemical properties:With the elevation rising, the effect of dry and hot wind smooth and soil physico-chemical properties gain obviously improving,that is the content of organic,total nitrogen,total phosphorus,available nitrogen,available phosphorus and available potassium increase notably and tend steady over 1005m height.The vegetation has little effect on soil physico-chemical properties at the height between 1500m and 1600m.â‘¡Soil microbial biomass and microbial respiration:With the elevation rising,soil microbial biomass of carbon and nitrogen are increasing quicklly,specially most at the height between 705m and 920m.but smoothing at the height between 920m and 1500m.The rising of Basic and attractive respiration show smoothly increasing tendency as the height promote. qCO2 shows decreasing tendency in the dry season result that the effect of dry and hot wind become smoothly,the menace to microbe become mild and the content of reduce, while low qCO2 assure the high efficiency of metabolizing to make soil gain enough active Dissolved Organic Matter and maintain soil great properties and the potential of Sustainable utility.â‘¢Soil enzyme activity:With the elevation rising,soil enzyme activity improve so much indicate that the activity of soil enzyme enhanced which include Phosphatases,invertase, urease, cellulose and catalase, acid phosphtase, catalase and Polyphenol Oxidase, while the state tend steady at the height over 1005m. As good water condition in wet season, soil enzyme activity is more obviously than dry season. At the same height the content of soil microbial quality is more in wet season than dry.(3)The dry-hot valley's sensitive indicators of soil quality identification and evaluation, a significant relationship proves that soil index characteristics shows different inner relationship and there is great variation between different index.Sensitivity analysis proves that there is big variation between different soil characteristics index,dividing that into high sensitivity,moderate sensitivity,low sensitivity and non-sensitivity index.When the variation ratio of urease,polyphenol oxidase,total nitrogen,basic microbial respiration,organic carbon,invertase,phosphatase,qCO2,. over 40 percentage,we call it moderate sensitivity.When the variation ratio of microbial biomass carbon,total phosphorus,cellulose,available nitrogen,microbial biomass nitrogen,available phosphorus,induced respiration and available potassium between 10 to 40 percentage,we call it low sensitivity.As the least variation ratio is the bulk density and catalase,call it non-sensitivity.According to sensitivity analysis and discrimination analysis,we identify soil sensitive indicators suiting to the dry-hot valley as basic microbial respiration,urease enzyme activity and qCO2. significant relationship analysis proves that what index we identified can reflect comprehensive oil index characteristics.Taking on Weighted Sum Model of fuzzy mathematics set up mode of soil simplify characteristics index and comprehensive characteristics index,then Simulating soil quality under different land use types and elevation,to show that what index we identified can reflect the series of changes of soil characteristics and simulate the quality changes during the process of soil ecology.