Browsing by Author "Firmino, Paulo N."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Avaliação do módulo de queda de folhada em eucaliptais no modelo 3PGPublication . Firmino, Paulo N.; Soares, Paula; Tomé, Margarida; Araújo, ClaraA subvalorização das estimativas de biomassa de folhada obtidas com a utilização do modelo 3-PG na análise do ensaio de fertilização e rega, para todos os tratamentos (Testemunha, Fertilização, Rega e Fertilização+Rega) conduziu à instalação de cestos de recolha de folhada em três parcelas, localizadas na Quinta do Furadouro, em Óbidos, em povoamentos de Eucalyptus globulus de origem seminal, em alto fuste e com diferentes idades e localizados em zonas com diferentes índices de qualidade de estação para confirmar as tendências observadas no referido ensaio. As parcelas 1 e 2 foram instaladas num eucaliptal de 4,5 anos, diferindo apenas no índice de qualidade de estação, enquanto a parcela 3 num de 8,5 anos de idade. As recolhas de folhada foram efectuadas com intervalos de 15 dias. Respectivamente, obtiveram-se valores de biomassa seca de folhada acumulada no período de 15 Março a 26 Outubro de 2011 de 1,12 Mg ha-1, 1,86 Mg ha-1 e 2,82 Mg ha-1. A melhor qualidade de estação diferenciou os resultados das parcelas da mesma idade, enquanto que a parcela de 8,5 anos apresentou valores superiores a ambas. Embora o número de recolhas seja reduzido, as estimativas obtidas pelo modelo 3-PG para as parcelas indiciam também a mesma subestimação, parecendo confirmar os resultados do ensaio que justificou este estudo. Embora estejam indiciadas conclusões, é necessário este estudo completar, pelo menos, um ano de recolhas de folhada e/ou possivelmente instalar novas parcelas para confirmar a necessidade de melhorar o submodelo de queda de folhada do modelo 3-PG para Eucalyptus globulus em Portugal
- Drivers for annual cork growth under two understory management alternatives on a podzolic cork oak standPublication . Faias, Sónia; Paulo, Joana Amaral; Firmino, Paulo N.; Tomé, MargaridaUnderstory management practices and stand density characteristics allow one to distinguish a cork oak traditional silvopastoral system (known as a montado) from a cork oak forest system. Although understanding the manner in which different management practices affect cork growth is imperative, there are still only a few outputs from experimental research that contribute to this knowledge. The effect of potential drivers on annual cork growth was analyzed using a linear mixed model approach. Two dimensions of drivers were considered: intraspecific competition, assessed by tree level distance-dependent indices; and interspecific competition, assessed by variables characterizing understory management. The present dataset was collected from an experimental trial established on a cork oak stand in Podzolic soil on the Tagus river basin, covering two different cork growth cycles over the period from 2003 to 2015. The adjusted models considered two understory management alternatives: spontaneous shrubs maintenance and forage application. In both models, annual precipitation displayed a positive effect on annual cork growth, as expected. However, no significant effect of intraspecific competition was found. Additionally, there was a positive effect on annual cork growth associated with the spontaneous shrubs growth and a negative effect associated with lupine presence; both effects linked to different cork ring ages’ thresholds. The study main contributions are the following: (i) the introduction of the interaction between cork growth cycle stage and understory management practices, only possible with cork sample collections from different cork rotation cycles; (ii) the finding that there was no significant effect of intraspecific competition on cork growth
- A tree‑ and climate‑dependent growth model to predict mature annual cork thickness under different climate change scenariosPublication . Paulo, Joana Amaral; Firmino, Paulo N.; Tomé, MargaridaClimatic factors drive the annual growth of cork and the subsequent increase in its thickness, which, in addition to porosity, determines the price of cork. Therefore, the simulation of cork thickness is a crucial module of forest growth simulators for cork oak stands. As the existing cork growth models are independent of climatic factors, cork thickness under different climate change scenarios could not be simulated using these models. The primary objective of this study was to develop a climate-dependent tree model to predict annual cork growth. We also verified the hypothesis that the effects of climate change on cork annual growth are nonlinear, and vary with the cork age and thickness. Due to the limited amount of work developed around this topic, we evaluated three candidate models and selected the one that presented best prediction performance as the base model. A set of climate variables that characterized annual climatic conditions were tested in the base model parameters. The resulting climate-dependent model was referred to as the fixed-effects model, and used to initialize a mixed-effect model which accounted for the nested structure of the data. We considered two random effects—the plot and the trees inside the plot. Annual precipitation and the Lang index (ratio between annual precipitation and mean annual temperature) were the variables that showed best results when included in the model parameters. Using a ratio of the variable to cork thickness recorded during the previous year, in both cases, suggested a decline of the positive effect of annual precipitation and the Lang index for increasing cork thickness. The models developed in this study predicted the cork thickness of individual trees based on the cork age and under different climate change scenarios. Therefore, they can be used in forest growth simulators for forest management and research purposes.