Analysis of the Factors Impacting on Gap Regeneration of Pinus densata in Shangrila Area

The linear regressive model with multiple objectives was built by taking the basal diameter and the seedling height as evaluation indexes to analyze the impact of 12 influencing factors on the growth of Pinus densata seedlings in the cause of forest gap regeneration. The 12 influencing factors were chosen from five aspects, i.e., the site environmental factors where the seedlings grew, the influence of the trees growing around the forest gap on the seedling growth, the impact of forest litter, the shrub effect and the feature of the gaps. The results showed that the model fitted well, and it could solve the study problem reasonably. In the progress of P. densata seedling regeneration, the age of the forest gap formed was the most influential factor, whereas the altitude was a very important influencing factor upon the basal diameter and height growth of the seedlings. Seven factors, which included the gradient, slope position, coverage and thickness of forest litter, shrub coverage and the average height of the shrub storey, and the distance between P. densata seedlings and the nearest bordering trees, were the major factors affecting the growth of seedling basal diameter in the forest gaps. The height of the nearest bordering trees laid important affect on the height growth of the seedlings.