Estimation of stand crown cover using a generalized crown diameter model: application for the analysis of Portuguese cork oak stands stocking evolution
Joana A Paulo , Sónia P Faias, Célia Ventura-Giroux, Margarida Tomé
iForest - Biogeosciences and Forestry, Volume 9, Issue 3, Pages 437-444 (2015)
doi: https://doi.org/10.3832/ifor1624-008
Published: Dec 02, 2015 - Copyright © 2015 SISEF
Research Articles
Abstract
A generalized non-linear tree crown diameter model was developed with the aim of allowing the computation of tree crown diameter over a large range of tree dimensions, and allowing its inclusion in forest growth and yield models. The model was formulated to provide biological meaning to the predicted values. Due to the nested structure of the data analyzed (trees within stands), both mixed- and fixed-effect models were developed. Since tree crown diameter is not frequently measured in forest inventories, the validation of the mixed model was carried out by considering the population specific response. The results demonstrate that when the measurements required for the mixed model calibration are not available, the use of the fixed effect model results in less biased and more accurate estimates. The fixed model was applied to the data from the two last Portuguese National Forest Inventories (NFI) to analyze the change in stand crown cover and assess the stocking evolution of cork oak stands in Portugal between 1996 and 2006. Results showed an increase in the frequency of stands with crown cover lower than 20%, as well as a decrease in the frequency of stands with crown cover between 20 and 40%. Average crown cover values were significantly different in the two NFI, with a decrease from 28.0 to 26.5% over the considered period.
Keywords
Quercus suber, Stand Crown Cover, Tree Crown Diameter, Nonlinear Mixed Effects Model, Nonlinear Fixed Effects Model, Portuguese National Forest Inventory
Authors’ Info
Authors’ address
Sónia P Faias
Célia Ventura-Giroux
Margarida Tomé
Universidade de Lisboa, Instituto Superior de Agronomia, Centro de Estudos Florestais, Forest Ecosystem Management under Global Change research group (ForChange), Tapada da Ajuda, 1349-017 Lisbon (Portugal)
Corresponding author
Paper Info
Citation
Paulo JA, Faias SP, Ventura-Giroux C, Tomé M (2015). Estimation of stand crown cover using a generalized crown diameter model: application for the analysis of Portuguese cork oak stands stocking evolution. iForest 9: 437-444. - doi: 10.3832/ifor1624-008
Academic Editor
Rupert Seidl
Paper history
Received: Feb 27, 2015
Accepted: Jul 28, 2015
First online: Dec 02, 2015
Publication Date: Jun 01, 2016
Publication Time: 4.23 months
Copyright Information
© SISEF - The Italian Society of Silviculture and Forest Ecology 2015
Open Access
This article is distributed under the terms of the Creative Commons Attribution-Non Commercial 4.0 International (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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