Study On The Rate Of Dissolution Soil Formation In The Karst Basin Of Haifeng,East Yunnan

In order to study the rate of dissolution soil formation in the karst basin sample area and watershed scale in the East China Sea,the influencing factors of dissolution soil formation were verified,and the rationality of the current vegetation restoration model was confirmed.In a hydrological year from November 7,2018 to November 7,2019,the Yunnan pine pure forest,the Yunnan pine secondary forest,the Yunnan pinemixed forest and the limestone thickets,and the native Yuanjiang alder oak-like underground stone trenches and soils were selected.Surface niche,using standard dissolution test strip method to compare and analyze the dissolution soil formation rate under the soil,and calculate the dissolution soil formation rate of the Lanshipo Haizi small watershed according to the modified watershed dissolution soil formation model.With a view to defining the allowable amount of soil loss and the control of rocky desertification in the karst basin of eastern Yunnan,it provides theoretical guidance and scientific basis.The following conclusions were reached:?1?The difference in dissolution of the three Yunnan pine forests is smaller and faster than that of the native forests and shrubs.In the niche habitats,the dissolution in the rainy season was significantly faster than that in the dry season.On the vertical profile,in the dry season,the ditch and soil surface of the secondary forest Shigou,plantations and pure forests accelerated dissolution with increasing depth.After slowing down,the soil surface of secondary forest and shrubland was opposite to the former.In the rainy season,the artificial forest,pure forest ditch and soil surface,shrubbery ditch accelerate dissolution with increasing depth,and the secondary forest ditch is opposite.The secondary forest and shrub soil surface first accelerate and then slow down with increasing depth,and the primary forest soil surface gradually decreases.In the horizontal direction,the surface dissolution difference is small;Under the soil 20cm,the soil surface of the pure forest dissolves fastest in the rainy season,and the secondary forest is the slowest,with rates of 71.28 t?km^-2a^-11 and 13.41t?km^-2a^-1,respectively.The slowest surface with 13.28 t?km^-2a^-11 and 3.97 t?km^-2a^-1;Under the soil of 40cm,the soil surface dissolves fastest in the rainy and dry seasons,with a rainy season rate of 112.67 t?km^-2a^-1,and the slowest erosion in the native forest soil,with a dry season rate of 3.16 t?km^-2a^-1.?2?The annual soil formation rate of pure forest soil is 0.31 t?km^-2a^-1,which is1.17 times,1.76 times,2.3 times and 4.98 times of the soil formation rate of Yunnan pine plantation,secondary forest,shrub and primary forest plots.Compared with the whole year,the rate of soil formation in rainy season of the same plot or even the same niche is higher and the rate of change is larger,which proves that the karst action is the strongest in rainy season.The rate of soil formation in rainy season of the same plot or even the same niche under the same plot is not only higher,but also the difference is greater than that in the whole year.The secondary forest of Pinus yunnanensis under natural succession and the artificial forest under artificial restoration mode are faster than the primary forest and shrub in the rainy season;the influence of rainy season on the formation of soil in various habitats increases with the increase of soil depth,and the difference of stand and habitat has a very important influence on the formation of soil.Comparing the proportion of soil quality of three Pinus plots in the whole year in rainy season,it can be found that the difference is small,which shows that the physical and chemical properties of soil and the hydrothermal conditions have little influence on the dissolution soil formation under different restoration modes of Pinus yunnanensis.?3?The dissolution rate of Haizi watershed is 43.1 t?km^-2a^-11 in dry season,which first slows down and then speeds up with the increase of soil depth;the dissolution rate of Haizi watershed in rainy season is 812.51 t?km^-2a^-1,which is 427.81 t?km^-2a^-1in the whole year,which gradually speeds up with the increase of soil depth.The soil formation rate during the dry season in the watershed is 3.83 t?km^-2a^-1,which gradually accelerates as the soil depth increases;The soil formation rate is about 16.5times that of the dry season;The annual soil formation rate gradually increases with the increase of soil depth,and the rate is 33.49 t?km^-2a^-1.?4?Soil moisture content and pH are positively correlated with soil formation rate,while porosity,EC,SOC and K₁₀0 are negatively correlated with soil formation rate.PH,water content and so on have a strong correlation with the rate of soil formation,and have a greater impact on soil formation.It can be seen that hydrothermal conditions play a decisive role in the process of karstification,promote the formation of soil,soil porosity,EC and other factors inhibit the formation of soil,all of which act on the carbonate rock and control the karst reaction.Under the recovery model of Pinus yunnanensis,the soil porosity and permeability of each habitat are less than that of primary forest and shrub,the soil viscosity is strong,the soil water retention accelerates the soil formation,and the soil moisture content and the soil formation rate have a good corresponding relationship,that is,the layer with high soil moisture content forms soil quickly.However,there are significant differences in the corresponding relationship between the soil moisture content and the soil forming rate among different sites.The soil moisture content of the primary forest is low?21.23%?,the soil forming rate is low,the soil surface moisture content of the pure forest is low?24.65%?,the soil forming rate is the fastest,the soil moisture content of the artificial forest is high?29.85%?,and the soil forming rate is also fast.With the succession of pine vegetation in Yunnan accelerating the rate of soil formation in karst areas,it has effectively confirmed the rationality of Yunnan pine as a tree species for restoration of rocky desertification.The niche under the soil surface erodes into the soil the fastest,and can be used as a habitat option for planting trees and afforestation and carrying out soil and water conservation in the future.