A new method for capturing stem taper variation for trees of diverse morphological types

Abstract

Understanding variation in tree stem form is fundamental to both ecological and economic assessments of forest ecosystem structure and function. Stem taper models (STMs) are widely used to describe tree form, but it can be challenging to apply them to trees with stems that diverge from an idealized norm, often leading to the exclusion of many trees from stem taper studies. Here, new "whole-tree" form type classes are advanced as simple and useful groupings for capturing stem form variation of trees of diverse morphological types and tested with a large tree data set without exclusion criteria. New form type classes explained much more of main stem form variation than knowledge of tree species, while "merchantable" form types explained the most variation between trees and stands. Broad-leaved species were much more likely to have complex stem forms than needle-leaved species, but species "evergreenness" was a very weak predictor of stem form variation when tree-and stand-level form variation was accounted for. A new, generalized framework for stem taper modeling is demonstrated, using both species and merchantable form types to capture tree-level random effects. New form types and the STM approach are relatively easy to apply and should be relatively simple to integrate into any conventional forest inventory system. Overall, the study demonstrates the importance of including and accounting for the diversity of observed stem forms in developing STMs.Résumé : Il est essentiel de comprendre les variations de forme de la tige des arbres tant pour l'évaluation écologique qu'économique de la structure et des fonctions des écosystèmes forestiers. Les modèles de défilement des tiges (MDT) sont largement utilisés pour décrire la forme des arbres, mais il peut être difficile de les appliquer à des arbres dont la tige diverge d'une norme idéalisée, ce qui entraîne souvent l'exclusion de nombreux arbres des études de défilement des tiges. Dans cette étude, de nouvelles classes de type de forme d'arbres entiers sont proposées, sous forme de regroupements simples et utiles pour capter les variations de la forme de la tige de divers types morphologiques, et testées sans critères d'exclusion avec un jeu de données comptant un grand nombre d'arbres. Les nouvelles classes de type de forme ont expliqué une beaucoup plus grande part de variation de la forme de la tige principale que la connaissance des espèces d'arbres, tandis que les types de formes « marchandes » ont expliqué la plupart des variations entre les arbres et les peuplements. Les espèces feuillues étaient beaucoup plus susceptibles d'avoir des formes de tige complexes que les espèces résineuses, mais le caractère sempervirent des espèces était un très mauvais prédicteur des variations de la forme de la tige, lorsqu'on tenait compte de la variation de la forme à l'échelle de l'arbre et du peuplement. Utilisant à la fois l'espèce et le type de forme marchande, un nouveau cadre généralisé permettant de capter les effets aléatoires au niveau des arbres est présenté pour la ...

Neighbour effects on tree architecture: functional trade‐offs balancing crown competitiveness with wind resistance

“…log( H ) vs. log( D )] using linear mixed effects modelling. We tested for significant effects of crowding and shading from neighbours (CC), as well as location and species, on model coefficients, treating them as random variables (MacFarlane & Weiskettel ). The general model was log( Y ) = (β 0 + μ k + μ jk + μ ijk ) + [(β 1 + λ k + λ jk + λ ijk ) × log( X )], where μ and λ are random effects coefficients for the intercept (β 0 ) and slope (β 1 ), respectively, and subscripts i , j and k represent location, species and CC, respectively.…”

Compatible System for Predicting Total and Merchantable Stem Volume over and under Bark, Branch Volume and Whole-Tree Volume of Pine Species

“…Whole-tree volume models that include the volume of fractions such as tree branches are required in order to provide information about the sustainable use of whole trees [2][3][4][5][6]. This could lead to an improvement of our understanding of synergies and tradeoffs between different types of forest ecosystem services, such as carbon storage, versus timber production [7]. Such models would help in decision-making associated with the sustainable extraction of more biologically renewable fuels from forests (e.g., [2,8]).…”

“…Compatible adjustment is also considered important for biomass fractions prediction (e.g., [13,44,45]. In contrast to the relatively large body of literature on compatible stem and taper prediction (e.g., [42,43]), little effort has been made to develop compatible models for predicting the volume of important tree fractions such as branches (e.g., [4][5][6][7]). Clearly, the next phase in tree volume modelling should be to describe the distribution of the volume of the different fractions of the whole tree, not only of tree boles [3].…”

Stem Taper Approximation by Artificial Neural Network and a Regression Set Models

“…To compare models as a complex expert systems without division to the particular tree species we applied ranking method. The sum of ranks for all evaluation criteria was on a [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] scale, which means that the best model obtained the lowest values and the worst model obtained the highest values (Table 4). Ranks have been calculated for the estimation of d and V separately.…”

“…While among most coniferous species, trees of irregular shape are rare, among deciduous species and other species with high plasticity in morphology they can be quite frequent. Removing them might limit the sample to regularly-shaped trees, and so the usefulness of such models would only be limited to such trees-such models, thus, should not be used for irregular trees [23]. If such irregulars constitute a significant part of the population-a likely scenario in the case of deciduous trees-then such models are not useful.…”