Analysis And Evaluation Of Stand Structure Characteristics And Soil Physical And Chemical Properties Of Coastal Defense Forest In Low Mountains And Hilly Area Of Shandong Province

In order to select the best forest structure types suitable for coastal defense forest in low mountains and hilly area of Shandong Province,three kinds of pure forest including Pinus thunbergii pure forest,Robinia pseudoacacia pure forest and Pinus densiflora pure forest,and four mixed forest including Pinus thunbergii+Quercus acutissima+Cotinus coggygria,Pinus thunbergii+Quercus acutissima+Robinia pseudoacacia,Pinus thunbergii+Quercus acutissima,Quercus acutissima+Cotinus coggygria were used as materil in this research.The methods of field investigation and indoor measurement were used to determine thirteen indexes of different stands,including age,mixed proportion,density,DBH,crown,height,height under branch and canopy density,and to study the structural characteristics of different stands,eleven indexes including soil moisture content,bulk density,capillary porosity,non capillary porosity,total porosity,maximum capillary water holding capacity,saturated water content,organic matter,total nitrogen,total phosphorus and total potassium were selected to study the physical and chemical properties of soil in different forest types.At the same time,according to the combination characteristics of different stand structure characteristics,combined with the results of soil and water conservation function evaluation,the correlation analysis of stand structure characteristics and soil physical and chemical properties was carried out,Finally,eleven key indexes were obtained,and a comprehensive evaluation index system was established.The entropy weight TOPSIS method was used to evaluate seven kinds of stands,providing scientific basis for selecting excellent stand types.The main results of this study are as follows:(1)Stand structure characteristics:In general,the structural layer number,coverage,litter thickness and other indicators of the mixed forest were better than that of the pure forest.While the broad and broad mixed forest was better than the coniferous and broad mixed forest.The mixed forest of Pinus thunbergii with multiple species was better than the mixed Pinus thunbergii forest with two species.For the mean chest diameter,mean tree height and mean crown width,the difference in five-year was not as significant as that of twenty-year.The five-year mixed forest of Pinus thunbergii is superior to the five-year black pine pure forest in the characteristics of canopy density,number of structural layers,coverage,litter thickness,number of standard branches per meter and so on,Based on the analysis of tree diameter skewness and Tree height kurtosis,it was concluded that the overall stand structure of the mixed forest of Pinus thunbergii + Quercus acutissima+ Robinia pseudoacacia and Pinus densiflora pure forest is reasonable.(2)Analysis and evaluation of soil physical properties:According to principal component analysis,the soil physical properties of twenty-year Robinia pseudoacacia pure forest were better than that of twenty-year Pinus densiflora pure forest;the physical properties of soil in the five-year mixed forest of Pinus thunbergii were better than that in the five-year Pinus thunbergii pure forest;the soil physical properties of the five-year coniferous and broad leaved mixed forest of Pinus thunbergii + Quercus acutissima were better than that of the five-year broad and broad mixed forest of Quercus acutissima + Cotinus coggygria.(3)Analysis and evaluation of soil chemical properties :According to principal component analysis,the soil chemical properties of twenty-year Pinus densiflora pure forest were better than that of twenty-year Robinia pseudoacacia pure forest,the chemical properties of soil in the five-year mixed forest of Pinus thunbergii were better than that in the five-year Pinus thunbergii pure forest,the soil chemical properties of the five-year broad and broad mixed forest of Quercus acutissima and Cotinus coggygria were better than that of five-year coniferous and broad leaved mixed forest of Pinus thunbergii and Quercus acutissima.(4)Correlation between stand structure characteristics and soil physical and chemical propertiesForest age,average DBH,average crown,average tree height,average height under branches,and number of standard branches per meter were significantly correlated with soil bulk density,non capillary porosity and saturated water content;average DBH,average tree height,number of standard branches per meter were significantly positively correlated with total porosity;canopy density and soil water content were significantly positively correlated.Forest age,DBH,crown breadth,height and height under br anches were positively correlated with organic matter and total nitrogen,DBH,crown breadth and coverage were positively correlated with total phosphorus,and canopy density was positively correlated with total potassium.(5)Weight of important factors affecting physical and chemical properties of soilUsing entropy weight method to calculate the weight of each index of soil physical and chemical properties,the weight of soil bulk density is the largest,which is 0.0927.In the soil chemical properties,the weight of total potassium is the largest,which is 0.0922.Combined with the correlation analysis of forest structure characteristics and soil physical and chemical properties,the influence weight of seven forest structure factors on soil physical and chemical properties is greater: forest age,average DBH,average crown width,average tree height,average height under branch,standard branch number per meter and canopy density.(6)Selection and recommendation of excellent stand structure typesBased on the entropy weight method and the TOPSIS principle,the soil and water conservation function of seven stands was comprehensively evaluated.The performance of the comprehensive evaluation was as follows,the twenty-year Robinia pseudoacacia pure forest was better than twenty-year Pinus densiflora pure forest,the five-year mixed forest of Pinus thunbergii were better than that in the five-year Pinus thunbergii pure forest,the five-year broad and broad mixed forest of Quercus acutissima and Cotinus coggygria were better than that of five-year coniferous and broad leaved mixed forest of Pinus thunbergii and Quercus acutissima,the coniferous and broad-leaved mixed forest of Pinus thunbergii with multi species combination was superior to the traditional double tree coniferous and broad-leaved mixed forest of two species of Pinus thunbergii.