Height-to-diameter ratios with temporal and dendro/morphometric variables for Brazilian pine in south Brazil

Height-to-diameter ratios(HD)are an important measure of the stability,density and competition of forest stands.It refl ects the vertical growth of the trees,the vulnerability of the forest canopy structure and infl uences volumetric production.HD ratios vary according to tree size,availability of resources for growth,stand density and species composition.Data were taken from 210 trees and a regression technique of generalized linear models for the HD ratio applicable for forest structure conservation was developed.The objective of this study was to model the HD ratios of dominant and co-dominant trees of Araucaria angustifolia according to morphometric,dendrometric,annual diameter increment,stand density,and age variables in three sites in southern Brazil.The results show that the HD ratio decreases with increasing age,crown area and basal area,and increases with stand density and annual diameter increment.Accuracy of the developed equations was demonstrated by the values of deviation,Bayesian and Akaike criteria.The results are of interest to forest managers since they make decisions about silvicultural operations.Growth continuity and forest production indicate that any intervention should be directed at younger trees of smaller sizes,and that one of the main management factors for stand stability and growth is the formation of the stand and its capture of light.

Understanding bark thickness variations for Araucaria angustifolia in southern Brazil

This study aimed to understand bark thickness variations of Araucaria angustifolia(Bertol.)Kuntze trees growing in natural forest remnants in southern Brazil,and their relationship with quantitative and qualitative attributes.Bark thickness must be accurately estimated in order to determine timber volume stocks.This is an important variable for the sustainable management and conservation of araucaria forests.In spite of its importance and visibility,bark thickness variations have not been evaluated for this key species in southern Brazil.A total of 104 trees were selected,and their qualitative and quantitative attributes such as diameter at breast height(D_(BH)),height(H),crown base height(C_(BH)),crown length(C_(L)),social position(S_(P)),stoniness(S_(T)),position on the relief(P_(R)),vitality(V_T)and branch arrangement(B_(A))were measured.The trees were categorized into two groups:red bark or gray bark.Regression analysis and artificial neural networks(ANN)were used for modelling bark thickness.The results indicate that:(1)bark thickness showed good correlation to D_(BH),with 0.76 as coefficient of determination(RS_P),0.540 as Mean Absolute Error(M_(AE))and 22.4 root-meansquare error in percentage(R_(MSE%));(2)the trend changed according to bark colour,with significant differences for the intersection(_0–Pr>F:p=0.0124)and slope(β_(1)–Pr>F:p=0.0126)of bark thickness curves between groups;(3)the highest correlation of bark thickness was found with:D_(BH)(ρ=0.88),H(ρ=0.58),C_(BH)(ρ=0.46),S_(P)(ρ=-0.52),and B_(A)(ρ=-0.32);(4)modelling with ANN confirmed high adjustment(R^(2)=0.99)and accuracy(R_(MSE%)=3.0)of the estimates.ANN is an efficient and robust technique for the modelling of various qualitative and quantitative attributes commonly used in forest mensuration.The effective use of ANN to estimate araucaria bark in natural forests reinforces its potential,besides the possibility of application for other forest species.