A tree crown ratio prediction equation for eucalypt plantations

Soares, Paula; Tomé, Margarida

doi:10.1051/forest:2001118

Cited by 75 publications

(44 citation statements)

References 16 publications

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“…Initially, it was attempted to fit m and w as model parameters, but model convergence problems were experienced. As suggested by Soares and Tomé (2001), the Richards and Weibull equations are special forms of logistic (eq. 1) and exponential (eq.…”

Section: Model Formsmentioning

confidence: 99%

Development of height to crown base models for thirteen tree species of the North American Acadian Region

Rijal¹,

Weiskittel

Kershaw

2012

The Forestry Chronicle

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Height to live crown base (HCB) is an important input variable for several growth and yield models. Since HCB is rarely measured in the field, it is often predicted using static models. Instead of predicting HCB, the Forest Vegetation Simulator Northeastern Variant (FVS-NE) uses an equation that predicts crown ratio (CR), which has not been well validated. The main goal of the present study was to construct a regional HCB model for thirteen selected tree species of the Acadian Region of North America. The specific objectives were to: 1) evaluate FVS-NE model predictions, 2) compare suitable model forms, and 3) assess influence of various covariates to improve predictions. We evaluated three model forms, namely Holdaway (1986), logistic, and exponential. The findings indicated that FVS-NE models were significantly biased for all species as the overall mean bias and root mean square error (RMSE) were 0.11 m and 1.80 m, respectively. A logistic equation with size (diameter at breast height [DBH], total height [HT] and ratio of DBH to HT), and competition (crown competition factor [CCF] and basal area larger than subject tree [BAL]) gave the best predictions for all species in this analysis. This model had an overall mean bias <0.01 m and an RMSE of 1.59 m, which represents a significant improvement in predictions compared to FVS-NE. Despite the range of species and observed variation in the data, the equations worked well and can be easily calibrated to new stands with a few local observations.

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Section: Model Formsmentioning

confidence: 99%

Development of height to crown base models for thirteen tree species of the North American Acadian Region

Rijal¹,

Weiskittel

Kershaw

2012

The Forestry Chronicle

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“…A full rotation may include up to 2 or 3 coppice cuts, each cut being followed by a stool thinning that may leave an average number of shoots per stool ranging from 1 to 2. Harvest ages typically range from 10 to 12 (Soares & Tomé 2001). Prescriptions further include several shrub cleanings over a rotation (i.e., 1 to 3 fuel treatments per cycle - Duncker et al 2012).…”

Section: Eucalypt Coppice Stand Management Schedulingmentioning

confidence: 99%

Developing wildfire risk probability models for Eucalyptus globulus stands in Portugal

Botequim¹,

García-Gonzalo²,

Marques³

et al. 2013

iForest

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© iForest -Biogeosciences and Forestry IntroductionFire is a major disturbance impacting the Mediterranean landscape (Rundel 1998). In recent decades its incidence has increased dramatically in southern Europe (Rego 1992, Moreno 1999, Pausas et al. 2008. The Portuguese territory is characterized by a Mediterranean climate and a rugged topography. Moreover, the Portuguese vegetation cover is mostly evergreen and drought resistant. The country is thus prone to vegetation fires. Recent demographic, socio-economic and climatic trends (e.g., Mather & Pereira 2006, Pereira et al. 2002 have further contributed to the country's vulnerability to wildfires. In Portugal, wildfire is the most important agent of land cover change (Pereira & Santos 2003). In fact, in the period extending from 1975 to 2007 the total burned area approximated 3.8 · 10 6 hectares, representing 40% of the country's area (Marques et al. 2011a).In Portugal, around 90% of the total forest land is managed by private landowners (DGRF 2006) and most stands are monospecific or dominated by one species. Eucalypt is the most important forest species in terms of area as it extends over 8.12 · 10 3 ha, corresponding to 26% of the country's forestland (ICNF 2013). Further, it provides key raw material to the export driven pulp and paper industry (about 5.75 million m 3 of pulpwood per year -DGRF 2007). Wildfires constrain the economic viability of eucalypt in commercial forestry and the competitiveness of this industry (Nogueira 1990, Moreira et al. 2001. The development of forest plans that may mitigate wildfire impacts on the profitability of eucalypt management scheduling is thus a key factor to the sustainability of this forestry sub-sector. This prompted the research of models to assess wildfire occurrence probability in eucalypt plantations as a function of variables that may be controlled by forest managers. The forestry literature has associated the term risk with the probability of occurrence of a natural hazard (González et al. 2006, Jactel et al. 2009. In this research, we will refer to risk as the probability of a stand to be affected by a wildfire (i.e., probability of burning) if an ignition exists ). Thus, rather than modeling fire ignition probability, the focus of this research is on modeling at stand level the probability of wildfire occurrence at stand level. This is understood as a spatial process related to forest structure as potential fire spread is impacted by fuel presence/composition (Fernandes 2009).In Portugal, former studies have focused on the characterization of wildfire ignition or of wildfire risk as a function of environmental or socioeconomic variables (Vasconcelos et al. 2001, Pereira & Santos 2003, Nunes et al. 2005, Catry et al. 2008, Marques et al. 2011a. It was demonstrated that in general wildfire impacts depend on the forest cover types where they occur (Moreira et al. 2001, Godinho-Ferreira et al. 2005, Nunes et al. 2005. The characterization of these impacts on eucalypt plantations was addressed recently by Fernande...

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“…The total tree aboveground biomass was calculated as the sum of the tree components. Crown length, used as an independent variable in the biomass equations for the leaves and the live branches, was estimated according to Soares and Tomé (2001).…”

Section: Changes In Bef With Stand Characteristicsmentioning

confidence: 99%

Biomass expansion factors for Eucalyptus globulus stands in Portugal

Soares¹,

Tomé²

2012

For. syst.

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One of several procedures for estimating carbon stocks in forests is the estimation of tree or stand biomass based on forest inventory data. The two approaches normally used to convert field measurements of trees to stand biomass values are allometric biomass equations and biomass expansion factors (BEFs). BEFs are used in published National Forest Inventory results in which biomass is not estimated or as a complement of growth models that do not include biomass predictions. In this paper, the effectiveness of BEFs for estimating total stand biomass in Portuguese Eucalyptus globulus plantations was analyzed. Here, BEF is defined as the ratio of total stand biomass (aboveground biomass plus root biomass) to stand volume with bark. To calculate total biomass, an equation was developed to estimate root biomass as a function of aboveground biomass. Changes of BEF with stand variables were analyzed. Strong relationships were observed between BEF and stand age, stand basal area, stand volume and dominant height. Consequently, an equation to predict BEF as a function of stand variables was fitted, and dominant height was selected as the predictor stand variable. Estimates of total stand biomass based on individual tree allometric equations were compared with estimates obtained with a constant BEF (0.77), used in the Portuguese National Inventory Report on Greenhouse Gases, and with estimates obtained using the dominant height-dependent BEF equation developed in this work. The BEF prediction model proposed in this work may be used to improve E. globulus Portuguese biomass estimates when tree allometric equations cannot be used.Key words: root biomass; aboveground biomass; biomass expansion factors; allometric equations. Resumen Factores de expansión de la biomasa de rodales de Eucalyptus globulus en PortugalEl objetivo es estimar las reservas de carbono en los bosques mediante la comparación de dos métodos: ecuaciones alométricas de biomasa y los factores de expansión de la biomasa (BEF). Las estimaciones de la biomasa total del rodal, basado en las ecuaciones alométricas de árboles individuales se compararon con las estimaciones obtenidas con unos factores de expansión constante de la biomasa (BEF) de 0.77, utilizados en el Informe del Inventario Nacional de Portugal de gases de efecto invernadero, y con las estimaciones obtenidas utilizando la ecuación de altura dominante de BEF desarrollada en este trabajo. En este trabajo se analizó la eficacia de la BEF para estimar la biomasa total del stand en portugués plantaciones de Eucalyptus globulus. Aquí, el BEF se define como el cociente de la biomasa total del stand (biomasa aérea más la biomasa de raíces), situándose el volumen con corteza. Para el cálculo de la biomasa total, se desarrolló una ecuación para estimar la biomasa de raíces en función de la biomasa sobre el suelo. Se analizaron los cambios de BEF con las variables del rodal. Se observó una gran relación entre el BEF y la edad del rodal, el área basal, el volumen y la altura dominante. Por lo tanto, ...

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A tree crown ratio prediction equation for eucalypt plantations

Cited by 75 publications

References 16 publications

Development of height to crown base models for thirteen tree species of the North American Acadian Region

Development of height to crown base models for thirteen tree species of the North American Acadian Region

Developing wildfire risk probability models for Eucalyptus globulus stands in Portugal

Biomass expansion factors for Eucalyptus globulus stands in Portugal

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