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  • ItemAcesso Restrito
    Creating fire smart forests and landscapes
    2010 - Fernandes, P. M.
  • ItemAcesso Restrito
    A site model for Pyrenean oak (Quercus pyrenaica) stands using a dynamic algebraic difference equation
    2005 - Carvalho, J.; Parresol, B.
    This paper presents a growth model for dominant-height and site-quality estimations for Pyrenean oak (Quercus pyrenaica Willd.) stands. The Bertalanffy–Richards function is used with the generalized algebraic difference approach to derive a dynamic site equation. This allows dominant-height and site-index estimations in a compatible way, using any desirable base age and allowing estimations to be time independent, which are important properties for site models. The database contains all possible height-growth intervals. The model is fitted considering residual autocorrelation, giving more efficient parameter estimates. Finally, the model behavior is analyzed by calculating error statistics from dominant-height and site-index estimations at different ages.
  • ItemAcesso Restrito
    Performance of Mechanical Forest Vegetation Clearing Technique and Litter Decomposition
    2010 - Carvalho, J.
    A mechanical technique for forest vegetation treatment is presented and analysed. A brush-cutting machine was used with Mediterranean-type vegetation in a forest vegetation management program to enhance wildlife habitat by promoting vegetation resprouting and grass reestablishment in mature shrublands. The performance of working time components was evaluated. Equipment components are described as well as benefits and applications of the technique. Two sites were compared in terms of vegetation composition and biomass, mechanical working performance, and litter decomposition rates. Litter decomposition was followed over a 2-year period. Changes in litter mass and nutrient content through time are evaluated and discussed. A working productivity between 3 and 4 h.ha-1 was obtained for different site and vegetation conditions. A major reduction of litter dry mass happens in the first 6 month after vegetation cutting. Litter decomposition rates range from -0.32 to -0.14 year-1 and the time for total decomposition ranges between 4 to 6 years. Litter nutrient composition presents the following order N>Ca>K>Mg>P. The relative mobility of these nutrients follows the order N>K>Ca>Mg>P. The estimated annual nutrient net release is about 91.8 kg N.ha-1, 4.5 kg P.ha-1, 52.8 kg K.ha-1, 39.5 kg Ca.ha-1 and 13.7 kg Mg.ha-1. Different litter decomposition rates and nutrient release on both sites and are discussed.
  • ItemAcesso Aberto
    Forest fires in Mediterranean countries: CO2 emissions and mitigation possibilities through prescribed burning
    2011 - Fernandes, Paulo; Terhi, Vilén
    Forest fires are integral to the Mediterranean Basin but fire incidence has increased dramatically during the past decades and fire is expected to become more prevalent in the future due to climate change. Fuel modification by prescribed burning reduces the spread and intensity potential of subsequent wildfires. We used the most recent published data to calculate the average annual wildfire CO2 emissions in France, Greece, Italy, Portugal and Spain following the IPCC guidelines. The effect of prescribed burning on emissions was calculated for four scenarios of prescribed burning effectiveness based on data from Portugal. Results show that prescribed burning could have a considerable effect on the carbon balance of the Land Use, Land Use Change and Forestry (LULUCF) sector in Mediterranean countries. However, uncertainty in emission estimates remains large, and more accurate data is needed, especially regarding fuel load and fuel consumption in different vegetation types and fuel layers and the total area protected from wildfire per unit area treated by prescribed burning, i.e. the leverage of prescribed burning.