Properties Of Soil In The Mountain Forests-the Arid Valley Ecotone In The Upper Reach Of Minjiang River

In this paper,the returning farmland to forest soil which in mountain forest - the arid valley of ecotone in Li County in the upper Minjiang River was studied. According to altitude,we divide the study area into three parts:typical arid valley area, ecotone area and mountain forest area.In these three parts,we choose representation of vegetation types respectively,and carry out vegetation surveys and soil sampling analysis.Study the soil physical and chemical properties Variability and change under different conditions of vegetation and under different environmental factors.Explore the mountain forest - the arid valley of ecotone vegetation restoration and management of the adjustment mechanism,and enrich Ecotone ecological theory of evolution,and ultimately to provide a theoretical basis in the mountain forest - the arid valley of ecotone vegetation restoration and management of complex ecosystems.The results indicated:①The soil bulk density under different vegetation types is around 0.96-1.65 g/cm~3 in the study area,and with soil depth increased;The soil porosity of surface layer is better than the lower.The PH of surface layer is greater in lower altitude (wasteland and Cupressus chengiana) and with the increase in altitude to reduce.The PH of sub-top soil has the same trend,but the value of its upper(0-10cm) is small than the lower(10-20cm).Due to the change of soil water content,human activities and other reasons,the majority of soil mechanical composition size are d＜0.25mm and 0.25～0.5mm,and variability of soil physical properties,the surface is greater than the lower.②The content of clay size(＜0.002mm) and granule size(0.02-0.002mm) is relatively high,and it increase with the increase in altitude and the increase in vegetation cover.The fine sand content of the second,but it reduces with the increase in altitude and the increase in vegetation cover.As the clay size and granule size can easily form their own micro-aggregates or soil organic matter to form a stable aggregate structure,enhance the corrosion resistance of the soil,this indicate that the increase in altitude soil corrosion resistance gradually enhanced in the study area.③With the increase in altitude and vegetation restoration,the content of soil total nitrogen,total phosphorus,available phosphorus,total potassium,available potassium and organic matter have a marked increase in the study area showed that soil moisture and vegetation are the main factors influencing soil nutrient status.In addition to soil organic matter,the soil nutrient content and the soil bulk density was significantly negatively related to illustrate the higher soil bulk density,soil compaction and Vietnam,the lower the nutrient content of soil.After restoration of vegetation,soil organic matter,total nitrogen,total phosphorus,available phosphorus,total potassium, available potassium increased in four seasons.The soil nutrient content in the stands: autumn＞winter＞spring＞summer.It shows that the restoration of vegetation significantly improved the soil,increase soil nutrient content.For the types of restoration of vegetation,the natural recovery Cyclobalanopsis and birch have the highest nutrient content,which followed by the Plantation,the Cupressus chengiana and wastelanarid in the arid valley of Minjiang River have the lowest nutrient content.④Mountain forest - ecotone area and plantation area where the soil nutrient is superior to the arid valley area shows that the natural conditions of the area is superior to the lower valley,as long as the afforestation,closed forest measure and to reduce the disturbance of grazing,vegetation can be rapid recovery.Therefore,in the process of vegetation restoration,the impact of elevation on the distribution of soil nutrients should be considered.Along ecotone,restoration forest step by step and make the timberline down,and ultimately to achieve the restoration of vegetation in arid valley, is a well-established channel in arid valley vegetation restoration,can be carried out in the arid valley of the promotion of vegetation recovery.⑤The size of soil micro-aggregates of fractal dimension in the stands:secondary forest＞shrub＞Robinia pseudoacacia forest＞mixed forest＞coniferous forest＞Minjiang hodginsii＞wasteland 2＞wasteland 1.In vertical direction,PFD of the aggregate fractal dimension:Mountain secondary forest＞ecotone＞Dry Valley area. That indicate the mountain forest - arid valley ecotone vegetation restoration is high-altitude superior to low-altitude,providing a theoretical basis improve the effectiveness of the restoration of vegetation in arid valley vegetation restoration,of gradually advancing from top to bottom to.Decision is the fractal dimension of the content of fine particles of soil,after vegetation restoration,the leaching of the enhanced role of visco-lake,and with a large number of the return of litter and vegetation on wind erosion and dust of the intercepted material effect on fine particulate matter increased the soil,soil the fractal dimension increased,soil fertility and structural change,and that the fractal dimension can reflect the vegetation in the arid valley of the degree of recovery.PFD of ecotone:shrubs＞Robinia pseudoacacia forest＞mixed forest＞coniferous forest.Due to the impact of a reduction of interference,shrub is superior to the other vegetation types,indicating that in the mountain forest - arid valley of ecotone,closed forest is the one of the important measures in ensuring vegetation recovery.