基于森林综合质量的红松人工林不同龄级适宜密度OA

[Objective]This study aims to determine the suitable management density for Pinus koraiensis plantations at different age classes based on comprehensive forest quality,providing a reasonable adjustment path for optimizing plantation structure.The management objectives of plantations forests in China have shifted from solely pursuing timber yield to comprehensively enhancing forest quality and efficiency.Therefore,it is of great significance to determine the optimal management density of forest stands based on forest comprehensive quality for establishing healthy stand structure and promoting sustainable management.[Method]Based on the data from 64 plots of P.koraiensis plantations with similar site indexes in Jilin Province,the effects of age and density on stand growth,undercanopy vegetation and soil nutrients were analyzed.Principal component analysis(PCA)was used to establish forest quality assessment model.The suitable density of P.koraiensis plantations of different age classes was determined based on the forest quality comprehensive index.[Result]With the increase in stand density,the growth of diameter at breast height(DBH)significantly decreased,while height and volume gradually increased.The diversity of shrubs increased first and then decreased,while herbaceous diversity significantly decreased.The phosphorus content gradually decreased,and the contents of hydrolyzed nitrogen,organic matter and available potassium showed a trend of first increasing and then decreasing.The evaluation model was constructed using 17 indicators to calculate the comprehensive index of forest quality,and it was determined that the composite index was the highest in the S4 density of Ⅰ age class(0.58),S3 density ofⅡ age class(0.65)and S2 density of Ⅲ age class(0.75),all of which were in the middle and high quality grades.[Conclusion]Based on the forest quality comprehensive index,the suitable density for different age classes is determined,which is 1 233-1 689 tree·hm-2.The DBH growth is inhibited,while height growth is accelerated.Herbaceous plants with strong light requirements become less under the canopy,shrubs with strong shade tolerance and competitiveness begin to grow,and the contents of organic matter,available potassium and hydrolyzable nitrogen content in the soil increase.For Ⅱ age class,the suitable density is 900-1 178 tree·hm-2.Compared to the Ⅰ age class,the growth space increases and light conditions improve,height growth slows down,while DBH growth gradually increases.The richness and diversity index of shrubs under the canopy improve.The well growth of tree and shrub species suppresses the growth of herbaceous plants,leading to a balance between soil nutrient consumption and replenishment.The suitable density for Ⅲ age class is 411-633 tree·hm-2.Compared to the Ⅱ age class,the growth slows down,and the vegetation structure under the canopy stabilizes.The extensive consumption of nutrients leads to a decrease in soil available phosphorus,available potassium and organic matter content.