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- Size–density trajectory in regenerated maritime pine stands after firePublication . Enes, Teresa; Lousada, José Luís; Aranha, José; Cerveira, Adelaide; Alegria, C.M.M.; Fonseca, TeresaResearch Highlights: This study bridges a gap of knowledge about the maximum size–density trajectory for juvenile stands of maritime pine. The continuity of the trajectory along the development stages to maturity is assured with a straightforward approach providing support to determine optimum density along all the revolution periods for the species. Background and Objectives: Forest fire is a significant threat to forests in the Mediterranean regions, but also a natural disturbance that plays a vital role in the perpetuation of forest stands. In recent decades, there has been an increase of burnt area in maritime forests in Portugal, followed by an increased interest in managing the natural and usually abundant regeneration occurring after the fires. The gap in the knowledge of growth dynamics for juvenile stages, for these forest systems, currently constrains their correct management, for forest planning, particularly in determining the optimal densities. The study aims to identify the maximum attainable density trajectory at the early stages of development of the species that could support a non-empirical definition of silvicultural prescriptions and thinning decisions, along the revolution. Materials and Methods: A representative data set collected in stands regenerated after fire supports the analysis of the maximum size–density trajectory for the species. Results: The maximum size–density trajectory for the juvenile stands deviates from the expected trajectory defined in the self-thinning line published for the species. Significant deviation occurs at the lower end of the line, indicating the need for a reevaluation of the existing self-thinning line. We propose a new self-thinning model for the species that explicitly considers the behavior of size–density for juvenile stands. The new model assures a logical continuity for the trajectory from the young stages of development to maturity. Conclusions: The proposed model based on the maximum attainable size–density trajectory provides ecological-based support to define silvicultural guidelines for management of the species.
- Assessing forestry biomass by means of field work a geostatistics process : a case in Northern PortugalPublication . Aranha, José; Viana, H.F.; Pedro, Nuno; Rodrigues, RosaliaTo assess Forest Biomass availability requires a hard field work survey and elaborate calculation techniques for vegetation classification and quantification. In March, April and May 2006, 900 sampling plots were surveyed with a help of a portable GIS (Geographical Information System) with GPS (Global Positioning System) capabilities. Within each sampling plot, an extensive field work was made in order to completely classify and quantify available forestry biomass. Data collection was regarding total number of trees within sampling plot, individual trees diameter at breast height, mean tree’s height, mean tree’s volume, mean tree’s canopy height and mean tree’s age. The results showed a range of values from 6.00 up to 21.00 dry ton./ha for adult Pinus pinaster (maritime pine) stands and from 1.00 up to 6.00 dry ton./ha for adult Eucalyptus globulus (eucalyptus) stands, both for thinning stands or for clear cut stands. In a second stage, they were applied geostatistic techniques (e.g. Weighted Inverse Distance, Kriging) in order to extend sampling plot results to fully study area and to create continuous biomass maps.