| The classification of forest site is a basic work in forestry production.The scientific and rational forest site classification can better guide cultivateforest,forestation and afforestation.Taking literature research as the main line,The brief history of the development of forest site classification at home and abroad is reviewed,and the main genres have been systematically combed.China currently has two forest site classification system,is a former Ministry of forestry resources division organization research and put forward to the forestry division in China based on the "Six grade forest site classification system",Site units include site area,site region,site sub-region,site type District,group of site type,site type site units,the first three levels are higher level zoning units,and the rest are low-level classification units;another is composed of unit Chinese Academy of forestry and forest site classification system research group proposed "Chinese forest site classification system,site units have forest site region,forest site zone,forest site area,forest site type district,forest site type.The first three units for high grade site units,and the latter two are low level units.The two systems are not exactly the same.Their views are basically the same.There are no essential differences between the site classification results,and they are all continuous distribution of the high level site units in the regional space,and the low grade site units are discontinuous.The two systems have a very high guiding value for China’s forestry production.The existing defects in forest site classification were pointed out,and the methods to solve the problems were put forward.Based on the six level classification system unfolding research,and the following main results are obtained.(1)It points out that there are two defects in the present forest site classification in the south of China,one is the focus on senior level site unit distribution continuous in the horizontal direction,failed to take into account the distribution law of bioclimatic conditions in the vertical direction;the two is confined to the site of high grade units,different forest vegetation climatic zones and soil types in the lower site unit.Based on the vertical zonality distribution law of soil.a new basis for "dividing forest site sub-region based on forest soil vertical zone spectrum" is put forward.There is only one zonal soil type,or other non zonal soils and hidden zonal soils in the new same sub-region.This is consistent with the basis of subdivision of the sub-region based on the "soil type difference" and "mountain vertical character" proposed by the Chinese forest site classification.According to this,the sub-regions are connected to the corresponding sites area respectively,and the distribution in the horizontal direction is continuous.It has enriched the basis of the classification of the Chinese forest site classification.(2)Based on the new subdivision and data collection,Taking the mountainous area in the west edge mountain area of the Sichuan Basin as an example,the feasibility of applying the new method in mountainous areas is explored.The means of specific division are digital expression spectra of vertical soil zones.the soil vertical zone spectrum expression of Mountain Altitudinal belts in a two-dimensional coordinate system.and provides a way to express the same mountain different zonal soil site sub-region width changess in the mountain.Refer to the vertical band data of the western mountain soil given in the Sichuan forest soil,the west edge mountain area is divided into four zonal soil site sub-region.mountain yellow soil site sub-region connect to the south subtropical site area,mountain yellow brown soil site sub-region in the theory of cohesion in North China warm temperate zone site area.mountain dark brown soil site sub-region and mountain brown coniferous forest soil site sub-region in the theory of cohesion in the northeast cold and warm temperate zone site area.(3)According to the new basis and referring to the existing soil vertical spectrum data,Taking east slope of Mount Jiuding as an example,the feasibility of applying the new method in mountainous areas is verified.A total of four sub-regions were divided in the study area.In order to avoid a number of areas with zonal soil site sub-region of the confusion,The name of area and soil is applied to the naming of new sub-region.After the serial number of the original sub-region is added to the Greek alphabet,the serial number of the new sub-region is indicated.So the four new sub-region are smoothly joined to the six level classification system.After the analysis and arrangement of the existing low level site units connect to the new sub-region,a complete forest site classification system has been obtained.Four sub-region name,number and cohesion are around the Sichuan basin on the western edge of mountain yellow soil site sub-region(VII 30A-α)in the theory of cohesion in the south subtropical site area;Sichuan basin on the western edge of mountain yellow brown soil site sub-region(IV 30A-β)in the theory of cohesion in the North China temperate site area.Sichuan basin on the western edge of mountain dark brown soil site sub-region(I 30A-γ)and Sichuan basin on the western edge of mountain brown coniferous forest soil site sub-region(I 30A-δ)in the theory of cohesion in the northeast cold and warm temperate zone site area,and the distribution in the horizontal direction is continuous.The above mentioned sub-regions are linked to the site type districts,site type groups and site type classification units that have been divided in the existing research results,and their spatial distribution is discontinuous.If there are non zonal soils and hidden zonal soils in the sub-regions,we should take the comprehensive consideration of small landforms and lithology,and divide the site type district with typical site type district.The four site sub-regions are both connect to Sichuan basin on the western edge of mountain site region. |
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