Quantitative Evaluation of Site Quality of Pinus sylvetrisl Plantation in Yulin Sandy Area

In order to provide reference for the afforestation cultivation and sustainable management of Pinus sylvetrisl plantation in Yulin sandy area. In this study, 38 sample plots of P. sylvetrisl plantation with 20 m×20 m were set up in Yuyang district of Yulin city, and the growth indexes of DBH and height of P. sylvetrisl plantation at different ages were investigated. Using the prediction model of quantitative theory I, the multivariate regression equation between the average height of dominant trees and site factors in P. sylvetrisl plantation was established, and the site evaluation grade was determined, and the site quality of P. sylvetrisl plantation was quantitatively evaluated. The results showed that: (1) With the growth of forest, the average diameter at breast height and tree height of P. sylvetrisl plantation increased significantly, and the fastest growth rate was in the 10th to 20th years. (2) The P. sylvetrisl plantation was divided into 12 site types with the three dominant factors of slope aspect, elevation and slope position, and the site classification results were evaluated. Based on the site evaluation of the surveyed plots, it could be seen that 75% of the P. sylvetrisl plantation in the surveyed plots had a site evaluation level above the intermediate level, which indicated that the site conditions of the P. sylvetrisl planting area in Yulin area were better and suitable for P. sylvetrisl planting. It showed that the prediction equation had been tested to meet the requirements, indicating that the quantitative theory I could be used to evaluate the site quality and predict the growth trend of the P. sylvetrisl plantation.