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Estimation of stand crown cover using a generalized crown diameter model: application for the analysis of portuguese cork oak stands stocking evolution
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Orientador(es)
Resumo(s)
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
Descrição
Palavras-chave
Quercus suber stand crown cover tree crown diameter nonlinear mixed effects model nonlinear fixed effects model portuguese national forest inventory
Contexto Educativo
Citação
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
Editora
SISEF