Crown Ratio Models for Tectona grandis (Linn. f) Stands in Osho Forest Reserve, Oyo State, Nigeria

Abstract

Crown ratio is the ratio of live crown length to tree height. It is often used as an important predictor variable for tree growth equation. It indicates tree vigor and is a useful parameter in forest health assessment. The objective of the study was to develop crown ratio prediction models for Tectona grandis. Based on the data set from the temporary sample plots, several non linear equations including logistics, Chapman Richard and exponential functions were tested. These functions were evaluated in terms of coefficient of determination (R 2 ) and standard error of the estimate (SEE). The significance of the estimated parameters was also verified. Plot of residuals against estimated crown ratios were observed. Although the logistic model had the highest R 2 and the least SEE, Chapman-Richard and Exponential functions were observed to be more consistent in their predictive ability; and were therefore recommended for predicting crown ratio in the stand.

Tree crown size as a measure of tree biosocial position in 135-year-old oak (Quercus L.) stand

“…Investigation on wood of teak trees from Nigeria proved strong correlation of relative crown length with the length of useful wood log, stem length, crown length and volume (Popoola and Adesoye 2012). Interesting findings were published by Chinese researchers (Jiang and Liu 2011) who applied relative crown length in their model of longitudinal cross-section of stems of larch with the determination coefficient 98%.…”

Multilevel Nonlinear Mixed-Effect Crown Ratio Models for Individual Trees of Mongolian Oak (Quercus mongolica) in Northeast China

“…Monserud and Sterba [ 49 ], Temesgen et al [ 10 ], and Leites et al [ 2 ] found that many other stand or tree variables had significant effects on tree CR, such as tree height (H), and H/D, named as tree slenderness coefficient [ 3 ]. In this study, these variables were also examined and it was found that their contributions to the prediction accuracy of the tree CR model were significant.…”

“…Stand density (SD) affects tree growth significantly [ 3 , 31 , 32 ]. Our preliminary analyses revealed that the differences of tree CR among different SD values of the PSPs were significant at a risk level of 0.05.…”

“…Tree crown size is an important variable that is commonly involved in growth and yield models used as decision-support tools in forest management [ 1 – 3 ]. Tree crown size is usually characterized using crown length (CL), crown width (CW), and crown ratio (CR).…”

“…One common approach used to obtain values of tree CR is to develop either deterministic or stochastic models from tree characteristics [ 1 – 3 , 5 , 10 , 11 ]. So far, most of the obtained models (see Table 1 ) are simply linear or nonlinear (e.g., Exponential, logistic and Weibull models) and often developed as a function of diameter at breast height (1.3 m above ground) (D), total tree height (H), age (A) and so on, using ordinary least squares techniques [ 12 , 13 ].…”