Physical-chemical Content And Fractal Characteristics Of Soil Particle Size Distribution Of Typical Forest Types In Eastern Liaoning Province

In the hilly areas of eastern Liaoning province,there is sufficient precipitation and high soil nutrient content.Forest trees could absorb various nutrients needed for their growth and development,which can promote their growth.However,as the regional chronic warming trend intensifies,the effects of increasing air temperature and decreasing precipitation increase,soil properties are significantly affected,and trees begin to decline and die.In recent years,such studies were still limited to the unilateral relationship between soil nutrients and plant growth,but little attention has been paid to soil particle size distribution.At present,the quantitative expression of soil hydraulic properties(physical properties),soil fertility(chemical properties)and soil erosion status at complex spatial scales can be realized by means of soil particle size distribution and fractal theory.Therefore,aiming at the above problems,the soil sample of Pinus koraiensis,Larix gmelinii,Quercus mongolica,Juglans mandshurica,mixed needle leaf and natural forests and control check(no forest cover)were collected,compared and studied.Soil physical-chemical properties and their relationship with soil fractal dimension under the depth of 0–10 cm(top soil layer)and 10–20 cm(top soil layer)(sub-top soil layer).The purpose of this study is to control and adjust soil fertility of P.koraiensis,L.gmelinii,Q.mongolica,J.mandshurica,mixed needle leaf and natural forests during stand management,so as to maintain soil fertility under the forest,improve soil physical properties,and finally achieve long-term maintenance of artificial forest and natural forest.It also provides scientific basis and practical reference for the later conservation management and sustainable management of artificial forests and natural forests.The main conclusions were as follows:(1)Top and sub-top soil physi-chemical properties under forests cover were higher than that of no forest(CK);The contents of each index in mixed needle leaf and natural forest were higher than other forests.The top soil physi-chemical properties content was higher than that of sub-top soil.Meanwhile,in terms of p H values,there was no significant difference in the p H values of the soils in the study and no obvious acidification.(2)Pearson correlation analysis was conducted on soil physical and chemical properties of each layer of different forest types.The results showed that all indexes were positively correlated,and there was a strong correlation between soil physical properties and soil chemical properties.Compared with other indexes,saturated water capacity had the highest correlation with each index.The correlation between soil available potassium and each index was the highest.The correlation coefficients of physical and chemical factors in top soil layer were higher than those in sub-to soil p layer.(3)Sand was the main soil particle size,followed by silt and clay,and the average volume fraction was less than 4.0%and 7.4%.From mixed needle leaf and natural forest,Q.mongolica,J.mandshurica,P.koraiensis,L.gmelinii forests to CK,the content of sand in each layer of the understory increased gradually,while the content of clay and powder decreased.The results indicated that mixed forest has an obvious improvement effect on top and sub-top soil,meanwhile,compared with coniferous forest,broad-leaved forest also has an obvious improvement effect on sub-top soil,the results indicated that the stand the existence of the influence of the soil and improve the effect is significant,while CK has a coarsening phenomenon in soil particles compared with top soil under external erosion,and soil particles show coarsening phenomenon.(4)The overall particle size characteristics are coarse,poor sorting,narrow to sharp skewness and peakness,and the soil fractal dimension distribution ranges from 1.800 to2.245.The mean particle size and fractal dimension of soil in each layer under forested forest were larger than those in CK,and the mean particle size and fractal dimension showed an increasing trend from mixed forest to single pure forest,indicating that soil fine particles gradually recovered under the long-term protection of trees,and the recovery rate of top soil layer was higher than that of the sub-top soil layer.(5)The relationship between soil fractal dimension and soil particle content in the top and sub-top soil of each forest type showed that the soil fractal dimension has a significant positive correlation with clay and silt,but a negative correlation with sand,but no significant correlation between soil fractal dimension and very coarse sand.The top soil fractal dimension was positively correlated with the peak value,but negatively correlated with other parameters.The fractal dimension of sub-top soil was negatively correlated with all parameters.The correlation between fractal dimension and all soil physical factors was high,and the correlation coefficient between fractal dimension and bulk density and capillary water holding capacity of top and sub-top soil was the highest,with R~2 above 0.70.The fractal dimension of top soil was strongly correlated with available nitrogen and available potassium(R~2=0.90 and 0.87).The correlation coefficients between sub-top soil fractal dimension and total N,total K and available K were above 0.910.(6)To sum up,P.koraiensis,L.gmelinii,Q.mongolica,J.mandshurica,mixed needle leaf and natural forests under top and sub-top physical and chemical and fractal dimension of soil increases indicated that soil is through the process of refining,increasing the proportion of clay and silt,improve soil structure,soil nutrient content was restored,all the indexes of mixed needle leaf and natural forest reach the maximum.In addition,the index values of top soil are higher than that of sub-top soil layer,which indicated that the construction of mixed forest and the restoration of top soil property are the key direction of forestry work in the future.