Growth Characteristic And Management Strategies Of Pinus Tabuliformis Aerial Seeding Forest In The Upper Danjiang River

Pinus tabuliformis is one of the main tree species for aerial seeding afforestation in Shaanxi Province.Aerial seeding forest of Pinus tabuliformis is the main component of artificial forest in the upper reaches of Danjiang River.Liuling aerial seeding forest area in Danfeng,the largest area in Shaanxi Province,has a series of problems at this stage,such as large overall density,poor health status,large individual differences among trees,weak growth,poor stem shape and material quality,and poor soil conditions,due to lagging management measures.In this study,Pinus tabuliformis aerial seeding forest in the upper reaches of Danjiang River was taken as the research object,and the optimal growth model of Pinus tabuliformis aerial seeding forest was fitted;According to the tree height,DBH,volume growth and average growth,the growth law of trees is analyzed;The effects of altitude and slope direction on the growth of Pinus tabuliformis were discussed;Analyze and determine the reasonable thinning intensity,the initial years and intervals of tending thinning,improve the management strategy of Pinus tabuliformis aerial seeding forest,and provide theoretical basis and practical guidance for the existing healthy management of Pinus tabuliformis aerial seeding forest.The study has an important role in promoting the healthy development of Pinus tabuliformis aerial seeding forest.The main results are as follows:（1）Through fitting analysis,logistic growth model is the optimal growth prediction curve of height,DBH and volume of Pinus tabuliformis aerial seeding forest in the upper reaches of Danjiang River.The fitting equations are as follows:=15.846/1+0)^1.909-0.082,R²=0.991=16.053/1+0)^3.332-0.1,R²=0.994（1=0.09/1+0）^7.686-0.22,R²=0.997In the upper reaches of Danjiang River,the continuous annual growth and average growth of tree height of Pinus tabuliformis aerial seeding forest reached the maximum（0.44 m）in the fifth year,and the continuous annual growth and average growth of tree height were the same（0.33 m）in the twenty-five years;The average growth of DBH reached the growth peak（0.27cm）in 40 years,and the annual growth reached the growth peak（0.46 cm）in 10 years;The annual growth of volume reaches the maximum value（0.005 m³）in 40 years,The average growth also reached the maximum at 40 years（0.002 m³）,In the 41st year,the annual growth and average growth of volume intersect（0.0018 m³）,In the late growth process,the annual growth has been lower than the average growth.（2）It is found that altitude has a great impact on the aerial seeding forest of Pinus tabuliformis,and the growth of aerial seeding forest of Pinus tabuliformis is not conducive to the growth of more or less altitude.When the altitude is 800 m～1100 m,the growth indicators（tree height,DBH,volume）of aerial seeding forest of Pinus tabuliformis growth are greater than other altitude gradients;The growth of Pinus tabuliformis aerial seeding forest has a certain correlation with the slope direction.The overall growth on the shady slope is better than that on the sunny slope.The different slope directions within a certain altitude range can not lead to significant differences in the growth of Pinus tabuliformis.（3）The first thinning time of Pinus tabuliformis aerial seeding forest in the upper reaches of Danjiang River was determined as the 10th year and the interval was determined as 8 years by analyzing the change law of tree DBH and volume growth curve;If the management purpose is to cultivate large-diameter step trees,the intensity thinning meets the thinning requirements;However,in order to improve the overall stand volume,it is necessary to adopt moderate or light thinning.（4）Single stand age structure and poor stand resistance are the main problems faced by Pinus tabuliformis aerial seeding forest management in the upper reaches of Danjiang River.At the same time,the problems of single stand structure and low species diversity can not be ignored.In view of the above problems,the following management measures are put forward:（1）reduce interference and improve resistance;（2）Adjustment of forest age structure;（3）Seeding selection and treatment;（4）Improve mixing angle and increase diversity.