Research On Spatial Optimization Of National Reserve Forest Based On Geo Design

Forests and timber resources are important natural resources and strategic resources of our country and are of great significance to our country's ecological construction and economic development.In order to solve the domestic long-term structural shortage of cherished tree species and large-diameter timber species,China proposed the establishment of national reserve forest system.When establishing a national reserve forest base,the principle of “appropriate site and suitable tree” must be observed,and the optimization of the spatial layout of multiple reserve tree species within the base must be considered.This study is based on the idea of Geodesign.By studying the suitability evaluation of tree species,the spatial connectivity of forest lands and the comprehensive index of the suitability of reserve forests,the spatial optimization and layout method of the tree species in the national reserve forest is proposed.Taking Jiangnan District of Nanning as the experimental area,Cunninghamia lanceolate,Pinus massoniana and Pinus elliottii are selected as target tree species to achieve reasonable distribution of tree species in the national reserve forest base.The main research contents of this study are as follows:1.Establish a solar radiation reference model based on terrain factors.Using the method of DEM and solar radiation to extract the direction of the slope,the solar radiation reference model based on the terrain factor was established by analyzing the relationship between the terrain factor and the solar radiation received by the ground surface.Compared with the DEM-based calculation of slope inconsistency at different resolutions and subjectivity for artificial measuring slope direction,the proposed method makes the calculation of slope direction more scientific and lays a foundation for accurate and effective assessment of forest land suitability.2.Evaluation of species suitability based on random forest models.The terrain,soil and climate data were selected as evaluation factors.Through factor correlation analysis,the factors with strong correlation were removed,and the 36 environmental factors affecting the growth status of tree species were reduced to 20,and a random forest model was established.The results showed that the growth conditions of Cunninghamia lanceolate,Pinus massoniana and Pinus elliottii were mainly affected by three environmental factors such as altitude,litter layer thickness,and average annual precipitation.A random forest model was established using the tree height classification method.The RMSE was 1.732-1.942,and the splitting attribute data was 6-7.This indicates that the model is overall stable,highly integrated,and has a small error.In the end,the lands of three species of Cunninghamia lanceolate,Pinus massoniana and Pinus elliottii were divided into five grades,followed by: the most suitable area,the suitable area,the basic suitable area,the inappropriate area,and the unavailable area.3.Experiment on Optimization of Spatial Distribution of National Reserve Forest in Jiangnan District of Nanning City.Using Cunninghamia lanceolate,Pinus massoniana and Pinus elliottii as target tree species,the method proposed in this paper was used for national reserve forest planning experiments.The results showed that the total area of suitable Cunninghamia lanceolate growing land in Jiangnan District of Nanning City was 842.25 km2,mainly distributed in the northwest of Jiangnan District;the total area suitable for growing Pinus massoniana land was 908.25 km2,mainly distributed in the east of Jiangnan District.With the central region,the total area of suitable sites for the growth of Pinus elliottii is 877.50 km2,mainly distributed in the eastern,northern and central regions of Jiangnan District;the total area suitable for growing Cunninghamia lanceolate,Pinus massoniana and Pinus elliottii is 1007.31 km2.Most of the space divisions of reserve tree species in the three countries are located at the Qipo Forest Farm in the southern part of Jiangnan District of Nanning City.The most suitable areas and suitable areas for tree species are selected to form forest sub-compartment concentration area for each tree species.Among them,Pinus massoniana had the highest proportion of land use,accounting for 63.41% of the total area,followed by Pinus elliottii,accounting for 25.53% of the total area,and the lowest proportion of Cunninghamia lanceolate land,accounting for 11.06% of the division area.4.Based on the idea of Geodesign,put forward the method of optimizing the spatial distribution of tree species in the national reserve forest.Through the assessment results of tree species suitability,the basic regional scope of tree species spatial layout optimization is determined.Based on the basic principle of optimal distribution of tree species land use,the spatial connectivity of forest land is analyzed,and the comprehensive index of suitability index of forest sub-compartment that meets the conditions of national reserve forest classification is calculated and selected.The division area and the sub-priority division area serve as further spatial optimization areas for the tree species of the national reserve forest.Comparing the existing area of tree species with the estimated planned area of national reserve tree species,the area will be expanded in accordance with the principles of “priority for spatial connectivity in forest sub-compartment and second to comprehensive index” until it meets the projected area of the national reserve forest tree species,and the spatial layout of the national reserve forest will eventually be optimized.There are mainly the following innovations:(1)A solar radiation reference model was constructed,and a method for dividing the slope direction using solar radiation was proposed,which made the results of slope direction calculation more scientific and lay the foundation for follow-up research.(2)A national reserve forest planning method based on Geodesign guidance,tree species suitability evaluation,forest land spatial connectivity,and reserve forest suitability index was proposed to provide technical support for the optimization of spatial layout of national reserve forests.