Analysis On The Characteristics Of Soil Physical And Chemical Properties And Soil Quality Along The Altitude Gradient In The East And West Slopes Of Ailao Mountains National Nature Reserve

Forest soil is the foundation for plant growth and development,and an important hub for the conversion of nutrient elements in forest ecosystems.In this paper,the southern part of Ailaoshan National Nature Reserve is taken as the research object.In the east and west slopes,the altitude is 1500~3137.6m,and the altitude difference is 100 m.The plot area is 10 × 10 m,and the height difference is 50 m apart.Three plots are randomly selected in each plot,and soil mixed samples and ring knife samples are collected at 0~20cm and 20~40cm.According to the data obtained from the experimental measurements,the comparative analysis of the changes in the physical and chemical properties of the east and west slopes of the reserve along the elevation gradient;based on the principal component analysis,combined with Norm value,correlation and sensitivity analysis,the soil quality evaluation index system was constructed and applied The comprehensive index method of soil quality provides a comparative analysis of the changes in the soil quality of the eastern and western slopes with the elevation gradient.the result shows:(1)Soil physical properties: With the increase of altitude,the moisture content,silt content,silty ratio,and powder-to-viscosity ratio of capillary soil in the dry and wet seasons of the east and west slopes increase,the clay content decreases,and the bulk density shows "Increasing" trend,the total porosity and non-capillary porosity showed a trend of "increasing first and then decreasing";the soil sand content of the east slope showed a decreasing trend,and the MWD(average weight diameter)showed an increasing trend,and the total agglomerates(diameter 10~0.25 mm The content of water-stable aggregates)did not change significantly.The total soil aggregates in the west slope showed an increasing trend,while the sand content and MWD did not change significantly.From the depth of the soil layer,the moisture content,total porosity,non-capillary porosity and MWD of the surface layer(0~20cm)of the soil at different altitudes on the east and west slopes are higher than that of the subsurface layer(20~40cm),clay content,powder Viscosity ratio and bulk density are lower than the subsurface layer;the content of silt grains on the surface soil of the eastern slope is higher than that of the subsurface layer.The content of sand and total agglomerates is higher than that of subsurface layer,and there is little difference between the content of silt and the porosity of capillaries between different soil layers.At the same altitude gradient,except for the total soil porosity,bulk density and non-capillary porosity,the physical properties of other soils on the east and west slopes are significantly different.From an altitude of 1800 m to 3137.6m,the soil moisture content on the east slope is lower than that on the west slope in the wet and dry seasons From 1500 m to 2200 m above sea level,the sand content and silt-viscosity ratio on the east slope are higher than those on the west slope,while the silt,clay content,total aggregate content and MWD are lower than the west slope;from 1800 m to 2600 m above sea level,the soil capillary porosity on the east slope Less than Xipo.This is because the west slope is a windward slope with abundant rainfall,high vegetation coverage,and a thick layer of litter on the surface,which makes the soil water conservation capacity,stability and development degree better than the east slope,and the east slope is especially 1500 m above sea level Outside the protected area up to 2200 m,the human disturbance is large,the soil erosion is strong,and the slope is large,and the physical properties of the soil are poor.(2)Soil chemical properties: As the altitude increases,the soil pH on the east and west slopes tends to increase first and then decrease,the soil alkaline nitrogen and available phosphorus content increase,the soil total phosphorus content decreases,and soil C/N The change was not significant;the content of organic carbon,total nitrogen and available potassium in the east slope did not change significantly,the content of total potassium in the soil showed a decreasing trend,and the content of organic carbon,total nitrogen and available potassium in the west slope showed a significant increase,and the content of total potassium in soil The trend is "decrease first and then increase".From the depth of the soil layer,the surface soil pH and total potassium of the east and west slopes are lower than that of the subsurface layer.The contents of soil organic carbon,total nitrogen,total phosphorus,alkali-decomposed nitrogen,available phosphorus and available potassium are higher than the subsurface layer,and the soil C/N The change is not significant.At the same altitude gradient,except for soil pH,available phosphorus and available potassium,the chemical properties of other soils on the east and west slopes are significantly different.From 1500 m to 2200 m above sea level,the content and spatial variability of soil organic carbon,total nitrogen and total phosphorus in the east slope are significant It is higher than the west slope;the elevation of 2200 m to 3137.6m,the soil organic carbon,total nitrogen and total phosphorus content of the east slope is less than that of the west slope;the altitude of 1600 m to 2900 m,the total soil potassium of the east slope is higher than that of the west slope.The difference in vegetation coverage is related.(3)Soil quality evaluation: select soil clay,silt,non-capillary porosity,MWD,organic carbon,total phosphorus and available phosphorus to construct an index system for evaluating soil quality on the east and west slopes.With the increase of altitude,the soil quality of Ailao Mountain and the west slope both showed an upward trend,which was mainly due to the increase of precipitation,the decrease of temperature,and the strong biological accumulation process.From the depth of the soil layer,the surface soil quality of the east and west slopes is at a medium to high level,and the subsurface layer is at a medium level.On the same altitude gradient,there are differences in the soil quality of the east and west slopes,from 2200 m to 2700 m above sea level.