The Growth Response Of Individual Trees In The Larix Principis-rupprechtii Plantation To The Stand Status And Site Environment In The Liupan Mountains

Larix principis-rupprechtii is the main afforestation tree species,we investigated 23 sampling points and collected 116 analytical wood data in Liupan Mountains forest area(semi-humid area)of Ningxia to study the response of tree height,DBH and volume to the tree status,stand structure and site environment.The tree height,DBH and volume growth process of Larix principis-rupprechtii under the influence of multiple factors were obtained by investigating each tree and analyzing wood with different dominance.On the basis of the study,we build the tree height,DBH and volume growth model which can reflect the influence of multiple factors was formed by a continuous multiplication.The model parameters were fitted using the measured data for getting the optimal tree height,DBH and volume growth model.So as to accurately predict the growth of trees and determine the suitable site conditions and stand structure.The results are as follows:1.The growth process of individual tree height of Larix principis-rupprechtii showed a"S"curve with rising tree age,which is slow first,then accelerated and then slow again.Tree height of up to27.68 m at 45 years,DBH up to 36 cm at 45 years.The growth process of individual plant volume with the increase of forest age showed a"J"curve.Based on this study,the tree height,DBH and volume growth of Larix principis-rupprechtii accord with the Richard equation.2.Typical correlation analysis showed that the influence on tree height growth by the factors except tree age followed the order of elevation>canopy density>dominance>stand density>slope aspect>slope;The order of influence on DBH growth of individual plant is:age>dominance>stand density>canopy density>elevation>slope aspect>slope.The order of influence on volume growth of individual plant is:age>dominance>stand density>elevation>canopy density>slope aspect>slope.Overall,the order of the main influencing factors is tree status(age,dominance),stand structure(density,canopy density)and site environment(elevation,slope aspect,slope),among which,age and dominance have a significant effect on the growth of Larix principis-rupprechtii.3.The changes of tree status(age,dominance),stand structure(density,canopy density)and site environment(elevation,slope aspect,slope)of Larix principis-rupprechtii are as follows:(1)The change trend of height growth of Larix principis-rupprechtii with elevation,slope aspect,slope,canopy density and stand density is first increasing and then decreasing,the most suitable conditions for the height growth of Larix principis-rupprechtii is the elevation range of 2000-2400 m,the slope aspect range from shade slope to half shade slope,the slope gradient range of 20-25°,the canopy density range of0.49-0.64,the stand density of 1100-1300 plants/hm~2.In addition,the height of individual trees increases with rising tree dominance but with a leveling-off increase rate after the dominance is higher than 0.2;(2)The change trend of DBH growth of Larix principis-rupprechtii with elevation,slope aspect and slope is first increasing and then decreasing,the optimum elevation range of DBH growth of Larix principis-rupprechtii is 2000-2200 m,the slope direction is the overcast slope and the half overcast slope,at 17.5-22.5,DBH increases and decreases with canopy density,best at 0.45-0.65,the DBH increased with the increase of stand density,the optimum density is 1000-1300 plants/hm~2,the DBH of individual plant increased with the increase of its potential,after the dominance is-0.05,the growth rate slows down and finally tends to flatten,the growth of DBH decreased with the increase of precipitation and increased with the increase of annual average temperature.(3)The change trend of volume growth of Larix principis-rupprechtii with elevation,slope aspect,slope,canopy density and stand density is first increasing and then decreasing,the optimum elevation range of volume growth per plant of Larix principis-rupprechtii is 2400-2600 m,the slope aspect is the overcast slope and the half overcast slope,a slope of 17.5-22.5,the optimum canopy density is 0.49-0.64,the optimum stand density is 800-1100 plants/hm~2.The volume increases with the increase of dominance,when the dominance is-0.2 to 0.05,the growth rate slowed down after the dominance of 0.05.4.A series of tree height,DBH and volume growth models were established according to the correlation analysis coefficient,and the R~2,RMSE,SSE,TRE of the models were compared,it is concluded that the tree height,DBH and volume growth models with comprehensive consideration of site factors and stand structure characteristics are the best.The R~2of the model was greater than 0.9,The potential uses of each growth model were discussed.The coupled model of individual tree growth considering the influencing factors can accurately predict the spatio-temporal variation of individual tree growth,to provide the scientific basis for the rational management of Larix principis-rupprechtii plantation.