The Function And Mechanism Of Soil Consolidation And Water Purification Of Typical Vegetation In Alpine Region Of Qinghai Province

In order to find out the function of soil fixation and water purification of typical artificial vegetation in the alpine region of Qinghai Province,and to provide theoretical basis for the selection of plant species in the region.In this paper,five typical vegetation and farmland in the alpine region of Qinghai Province are taken as the research objects.Through field investigation and indoor experiments,the diversity characteristics,physical and chemical properties of soil,water and soil loss and nutrient diversion loss are analyzed by means of multiple regression,path analysis,analytic hierarchy process and entropy weight method.And through the systematic evaluation of the functions of vegetation to maintain biodiversity,improve soil fertility,reduce water and soil loss and purify water quality,the order of soil fixation and water purification function of six vegetation is obtained,which provides theoretical basis for selecting vegetation types that meet different functions.The main conclusions of this paper are as follows:1.Forest and grass vegetation can significantly improve the ecological environment,increase species diversity,improve the imbalance of soil vegetation system,and promote the coordinated and healthy development of regional ecosystem.There are 113 species,92 genera and 39 families of vegetation in the study area,including 4 species of trees,11 species of shrubs and 99 species of herbs.The species number of understory vegetation of Populus cathayana Rehd.is the most,and the species number of grassland is the least except the control group.The order of species diversity index of six plantations is consistent,which shows that deciduous species is better than evergreen species.Species diversity index is positively correlated with soil porosity,water conductivity,p H and available K content,and negatively correlated with bulk density,available P and total P.Through the construction of the coupling degree and coupling coordination degree model of vegetation and soil,it is found that the forest and grass vegetation belong to the middle coordinated soil lagging development type,while the contrast farmland belongs to the low coordinated vegetation lagging development type.2.Forest and grass vegetation can significantly improve the physical properties of soil,improve the permeability of soil,especially for the surface soil.The order of the total porosity of soil is just the opposite of the change of bulk density,and the porosity and saturated hydraulic conductivity decrease with the deepening of soil layer.The content of deciduous tree species is higher than that of evergreen tree species,broadleaf forest is better than coniferous forest,and the content of control group is the lowest.3.The runoff yield of vegetation runoff plot is as follows: control group> Populus cathayana Rehd.> Picea crassifolia > Juniperus przewalskii > grassland > Larix principis-rupprechii.The runoff reduction benefits were 44.66%,57.04%,64.53%,73.13% and 98.09% respectively.The sediment yield is as follows: control group> Populus cathayana Rehd.> grassland > Juniperus przewalskii > Picea crassifolia > Larix principis-rupprechii.The benefits of sediment reduction are 67.33%,90.68%,94.98%,95.47% and 98.57% respectively.Forest and grass vegetation can delay the production of rainfall runoff,and the delay effect is worse when the interval time of rainfall is shortened.Rainfall,litter biomass,vegetation coverage,litter thickness,herbage biomass and bulk density have the greatest impact on runoff,while rainfall intensity,runoff and dry weight of litter have the greatest impact on sediment yield.4.Compared with the control group,the loss of soil nitrogen and phosphorus in forest and grass vegetation decreases significantly.The order of loss of nutrient diversion is control group > Populus cathayana Rehd.> Picea crassifolia > Juniperus przewalskii > grassland > Larix principis-rupprechii.Forest and grass vegetation effectively reduce and control the output of soil nutrients,nitrogen and phosphorus nutrients.Larix principis-rupprechii has the strongest capacity,and Populus cathayana Rehd.is the worst.Surface runoff,organic matter content and litter biomass have the greatest impact on nutrient loss.5.Using the method of subjective and objective comprehensive weighting to evaluate the comprehensive benefits of soil and water purification of different vegetation types in the alpine region of Qinghai,the results show that the comprehensive benefits of soil and water purification of Larix principis-rupprechii is the highest,followed by Populus cathayana Rehd.,Juniperus przewalskii and grassland.Except for the control group,the comprehensive benefits of Picea crassifolia are the worst.The comprehensive index of soil and water conservation and biodiversity conservation of Larix principis-rupprechii is the highest,and the comprehensive index of maintaining soil fertility and purifying water quality of Populus cathayana Rehd.is the highest.Through sensitivity analysis,it can be seen that the comprehensive evaluation results are stable within the specified range and have certain credibility.