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Carbon and nutrients stocks in even-aged maritime pine stands from Portugal
Publication . Nunes, Luís; Patrício, Maria Sameiro; Tomé, José; Tomé, Margarida
To comply with the demands of the Kyoto Protocol, industrialized countries must reliably estimate the stored carbon (C) in different pools of forest ecosystems. The main objective of this study was to quantify the biomass, C and nutrients stocks in the forest floor, understory, downed dead wood (DDW) and mineral soil of even-aged maritime pine (Pinus pinaster Ait.) stands from three contrasting regions of Portugal. Assessing the specific contribution of DDW to the C and nutrients stocks and how C concentration in the plant material differs from 0.50, the reference value used in many practical applications, were also objectives of this research. Biomass content of forest floor was determined by a quadrat method. Sampling units of 1 m2 were used for the understory. The line intersection method was adopted for sampling DDW and the mineral soil was sampled at three depths. Concentrations of C and nutrients were obtained by chemical analysis of samples from soil and milled plant material. Biomass and C in the trees were obtained using published equations. Total C stocks ranged between 100.6 Mg ha–1 and 308.6 Mg ha–1. Mineral soil shared up to 70-74% of global stored C, being the main cause of the global C stock differences among regions. Phosphorous and potassium were at low to very low levels in the mineral soil and plant material. The contribution of DDW to the C and nutrients pools was negligible. The percentage of C in the plant material ranged between 52% and 54%.
Prediction of annual tree growth and survival for thinned and unthinned even-aged maritime pine stands in Portugal from data with different time measurement intervals
Publication . Nunes, Luís; Tomé, José; Tomé, Margarida
An annual individual tree survival and growth model was developed for pure even-aged stands of maritime
pine in Portugal, using a large data set containing irregularly time-spaced measurements and considering
thinning effects. The model is distance-independent and is based on a function for diameter
growth, a function for height growth and a survival function. Two approaches are compared for modeling
annual tree growth. The first approach directly estimates a future diameter or height using well-known
growth functions formulated in difference form. The second approach estimates diameter or height using
a function in differential form estimating the increment over a year period. In both approaches, the function
parameters were related to tree and stand variables reflecting the competition status of the tree as
well as of a thinning response factor. Variable growth and survival rates were assumed in the modeling
approaches. An iterative method was used to continuously update tree and stand attributes using a cutoff
to convert the survival probability for a living or a dead tree. The individual tree diameter growth
model and the survival probability model were fitted simultaneously using seemingly unrelated regression
(SUR). Parameters of the height function were obtained separately as the number of observations for
height was much lower than the number of observations for diameter, which may affect the statistical
inference and the estimation of contemporaneous cross-equation error correlation inherent to the system
of equations. PRESS residuals were used to evaluate the predictive performance of the diameter and the
height growth functions. Additional statistics based in the log likelihood function and also in the survival
probability were computed to evaluate the survival function. The second modeling approach, which integrates
components of growth expansion and decline, performed slightly better than the first approach. A
variable accounting for the thinning response that was tested proved to be significant for predicting
diameter growth, even if the model already included competition-related explanatory variables, namely
the basal area of trees larger than the subject tree. However, this thinning response factor was not significant
for predicting height growth.
Sistema de predição de volumes total e mercantil compatível com diferentes definições de volume
Publication . Nunes, Luís; Tomé, José; Tomé, Margarida
O volume é a variável dendrométrica que mais tem sido utilizada para expressar o quantitativo lenhoso, sendo uma das mais importantes variáveis a obter em qualquer inventário florestal. É frequente, nos inventários florestais nacionais de diferentes países, observar-se a utilização de diferentes definições do volume da árvore individual. Neste trabalho desenvolve-se um sistema compatível de equações para estimar volume total e volumes mercantis, o qual foi concebido de forma a facilitar a conversão e subsequente comparação dos resultados de inventários florestais que utilizem diferentes definições de volume da árvore. O sistema contém também uma função de perfil do tronco que, quando devidamente integrada, garante a compatibilidade entre equações de perfil do tronco, volume total e volume percentual. O sistema apresenta bons resultados quando aplicado a dados de pinheiro bravo em Portugal representativos de todo o país e cobrindo árvores de diferentes dimensões.
Equações para estimar factores de expansão de biomassa para as principais espécies florestais em Portugal
Publication . Faias, Sónia; Paulo, Joana; Soares, Paula; Patrício, Maria Sameiro; Freire, João P.; Correia, Alexandra I.; Tomé, Margarida
Para estimar a biomassa do povoamento, usualmente são utilizados dois métodos: aplicação de equações de biomassa ao nível da árvore e aplicação de factores de expansão de biomassa (BEF) constante, pela simples multiplicação destes valores pelo volume do povoamento. A utilização de factores de expansão de biomassa, em relação à determinação da biomassa com recurso a equações alométricas da árvore, tem a vantagem de ser aplicável em dados já processados e em modelos de crescimento de povoamento que não incluem o módulo de biomassa. Diversos estudos concluíram que o factor de expansão de biomassa não é constante ao longo do tempo, mas que depende do estado de desenvolvimento do povoamento. Neste estudo apresenta-se equações para estimar os factores de expansão de biomassa a partir de variáveis do povoamento facilmente obtidas com os dados de inventário florestal, para algumas espécies florestais, nomeadamente: pinheiro bravo, eucalipto, sobreiro, pinheiro manso e castanheiro. Os resultados da sua aplicação são comparados com os resultados obtidos com aplicação dos valores de BEF constantes publicados em Portugal e com aplicação das recentes equações alométricas para estimar o volume e a biomassa da árvore individual.
Modeling dominant height growth of maritime pine in Portugal using GADA methodology with parameters depending on soil and climate variables
Publication . Nunes, Luís; Patrício, Maria Sameiro; Tomé, José; Tomé, Margarida
Background Maritime pine (Pinus pinaster Ait.) is a common conifer species in Portugal that contributes significantly to the national economy. Accurate classification
of forest productivity based on site index and height growth dynamics is the main basis for sustainable forest management of this species.
Objectives The main objective of this study was to develop a new dynamic site-dependent height–age model for the maritime pine in Portugal, using the generalized algebraic difference approach (GADA) methodology, and to explore possible improvements of the model´s performance by expanding its parameters as sub-functions of soil and climate variables.
Methods We tested for this purpose several dynamic equations, including anamorphic, polymorphic with common asymptote, and polymorphic with multiple asymptotes equations. The candidate models were fitted to a large set of stem analysis data, and tested on independent data from permanent sample plots.
Results The two best models with multiple asymptotes, one anamorphic and one polymorphic, showed similar performance; however, upon expanding the parameters as
sub-functions of the climate and soil variables, the polymorphic model outperformed the anamorphic model, as well as other models previously used for the management of this species in Portugal. The results of this study also demonstrated that the maritime pine model, developed with stem analysis data, can accurately predict the dominant height growth measured on permanent sample plot data.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
POCI
Funding Award Number
POCI/AGR/57279/2004