The Serra da Estrela (1993 m) is the highest mountain of continental Portugal. It is situated in the central-east of the country and forms the western part of the Sístema Central. The Serra da Estrela has a mediterranean mountain climate with atlantic influences. The mean precipitation is about 2000 mm a year with a dry period in summer, which is crucial for fires. Today, the main plant formations of Serra da Estrela are heathlands, broom scrub, (open) grasslands and tree plantations (especially Pinus pinaster and Castanea sativa).
Because of its species richness and its geographical situation, the area is considered to be an important part of the biogenetic network of European habitats. The largest part of the area is located within the limits of the Parque Natural da Serra da Estrela (101.060 ha), which was founded in 1976. There is palynological evidence that in the western part of the mountain, already ca. 4000 years ago, a Betula-Quercus woodland was destroyed by fire. Thunder striking may have been responsible for this, but it has been proved that anthropogenic influence was noticeable more than 2000 years ago. Since those days fire activities and erosion processes increased and gradually the original forest (mostly consisting of oak species) disappeared, being mainly replaced by heathlands, broom scrub and (open) grasslands.
The tradition of migrating flocks of sheep and goats over long distances, the so-called transhumância, goes way back to medieval or perhaps even to Roman times. However, nowadays, the movements of animals are restricted to travelling from low altitudes to the mountains in spring and the reverse during fall. The pastoral tradition of using fire as a tool to improve grazing grounds or to keep down scrub, is still practised today. Under certain conditions, this tradition may guarantee the conservation of the typical plant cover mosaic of Serra da Estrela. However, for various reasons, burning nowadays is not only practised by shepherds and farmers, but also by barbecuing tourists, pyromaniacs and criminals. Especially these new activities interfere with a relative recent form of landuse, namely the plantation of non-indigenous pine, which was started in the beginning of this century. These industrial pine plantations are extremely susceptible to ignition. Measured over the last thirteen years, about 450 forest fires burnt down each year, approximately 9,000 ha within the territory of the six communities (236,444 ha) which cover the Serra da Estrela (Florestal Nacional, unpublished). Maybe these plantations could benefit from controlled fires to lower the fuel load of the understorey. Another option is to replace them with deciduous trees or to restore the original forests. Pros and cons of both conservation and economic value should be weighed in- and outside the limits of the Nature Park.
Burnt Areas Project
For 1997 there is a bit of financial support to study the effects of fire on vegetation in the Parque Natural da Serra da Estrela. In order to collect useful information on this hot topic, a small programme was designed by our team from four cooperating institutes. Unfortunately the financial budget will not be sufficient to perform experiments. For this reason we will start from previous burnt areas. We will proceed by selecting an appropriate amount of burnt sites which proportionately express the major ecological variation within the area of the Park. The Serra da Estrela has a long fire history and both number and size of fires increased considerably during the last few years. Therefore we expect to find enough sites which reflect the main ecological variation.
Three major climatic belts exist: the oro-, supra- and mesomediterranean zone. Each belt has its own climatic climax series and its typical mosaic of plant cover depending on a number of variables of which the following, if possible, should be taken into account: topography (plateaux and slopes with different angles, exposures), pedology (soil), geology (underlying rock), hydrology and land-use (including history as well as present state of ownership, cattle grazing, cutting, ploughing, crop rotation, plantation, burning, etc.).
Once an area is selected, a general description will be made. This general description includes a.o. delimitation of the area on a detailed geographic map with additional UTM coordinates, date of previous fire, description of the overall vegetation with emphasis on structure, plant species composition, frequency/abundance of plant species according to Tansley and all the ecological variables which were mentioned before. A more detailed description will be made of the separate homogenous patches which build the total mosaic of the burnt area. This detailed description will be made on the basis of sample plots according to the method of Braun-Blanquet, with additional information on lifeform spectra, survival strategies and extra emphasis on cryptogams. Various data analyses will be made after storage in the computer with the programme “Turboveg” (S.M. Hennekens, IBN-DLO, P.O.Box 23, NL-6700 AA Wageningen).
The sites will not only be marked on the map but also be photographed in order to continue the investigation as soon as there is enough financial support again. In this way the procedure functions also as an initial monitoring programme to trace long-term processes of vegetation dynamics.
Except for casual personal observations there never has been a structural study on fire related vegetation dynamics in the Parque Natural da Serra da Estrela. We hope that this small project will generate a pile of information from which precious knowledge for management practices and future experiments with prescribed burning can be drawn. Cooperation is planned with the project group of Natural Vegetation Dynamics and Vegetation Management (F. Rego, Estaçao Florestal Nacional, Rua do Borja 2, P-1350 Lisboa). This group performs already experiments with prescribed burning in the Nature Reserve of Serra da Malcata, which is situated east of the Estrela mountains, near the Spanish border.
From: J. Jansen and L. Lourenço Institute for Forestry and Nature Research (IBN-DLO) P.O Box 23 NL-6700 AA Wageningen Instituto de Estudos Geográficos Faculdade de Letras, Universidade de Coimbra P – 3049 Coimbra Codex M. Sim Sim P. Carvalho Departamento de Biologia Vegetal Faculdade de Ciências da Universidade de Lisboa Campo Grande, Bloco C2, 4° piso P – 1700 Lisboa Museu, Laboratório e Jardim Botânico Rua da Escola Politécnica 58 P – 1294 Lisboa Codex