Dynamic height growth model for Spanish and Tunisian cork oak (Quercus suber L.) forests

María De La O Sánchez González,Boutheina Stiti,Hatem Chaar,Isabel Cañellas

doi:10.5424/fs/2010193-8495

Abstract

Seven simple and advanced dynamic polymorphic functions were considered to develop a dominant height growth model for Spanish and Tunisian cork oak forests. Data from 115 stem analyses performed in two regions in each country were used to fit the equations. Parameter estimates were obtained using the Dummy variable method. Both numerical, graphical and biological consistency were used to compare alternative models. The dynamic equation finally selected was derived from the Hossfeld model by considering the shape parameter to be related to site productivity. An analysis of the dominant height growth patterns between the two countries indicated that the same dominant height growth model was valid for both countries. This dominant height growth model allows estimation of dominant height with a level of reliability of at least 83% from an age of 15 years for a prediction interval of less than 40 years.

Highlights

The natural distribution area of cork oak (Quercus suber L.) extends across in the countries of the western Mediterranean basin, covering a total area of over 2 million hectares between latitudes 33°N and 45°N (Pereira, 2007)
Cork oak plays a key role in the economies of the regions in which it is found, due to the direct economic benefits from cork production, but because of indirect benefits derived from activities associated with this type of forests such as hunting and cattle grazing or other forest products, for example, firewood, acorns, etc
Three base equations previously used for cork oak dominant height-age modeling in Spain and Tunisia were considered: the Lundqvist-Korf (Lundqvist, 1957; Korf, 1939) equation, the Richards (1959) function and the Hossfeld model, in particular the base equation was Hossfeld IV (Kiviste, 1998)

Summary

Introduction

The natural distribution area of cork oak (Quercus suber L.) extends across in the countries of the western Mediterranean basin, covering a total area of over 2 million hectares between latitudes 33°N and 45°N (Pereira, 2007). Cork oak forests and woodlands currently occupy considerable areas in Spain (475,000 ha) and Portugal (713,000 ha) as well as in Morocco (348,000 ha), Algeria (230,000 ha) and Tunisia (90,000 ha). Cork oak plays a key role in the economies of the regions in which it is found, due to the direct economic benefits from cork production, but because of indirect benefits derived from activities associated with this type of forests such as hunting and cattle grazing or other forest products, for example, firewood, acorns, etc. The cork oak forests are valued for their ecological role in mitigating desertification and soil erosion, as well as for their contribution to the preservation of biodiversity and carbon storage (Cañellas et al, 2008). Sánchez-González et al / Forest Systems (2010) 19(3), 285-298

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