Aplicación del análisis pedoantracológico para la reconstrucción del área de distribución del paleoendemismo Abies pinsapo

Resumo

The Spanish fir (Abies pinsapo Clemente ex Boiss.) is an endemic fir of the Serranía de Ronda, so it is considered that this tree species is of great singularity and ecological value in the Iberian Peninsula. The ecological exceptionality of this conifer was initially recognised by Simón de Rojas Clemente y Rubio in 1818, and was later disseminated by Edmond Boissier in the 1930s. The reduced spatial distribution of the Spanish fir at present, confined to three disjunct mountainous areas of the Serranía de Ronda, as well as its demanding environmental requirements, make this Mediterranean fir highly vulnerable to any threat, a situation that has led it to be catalogued as an endangered species in danger of extinction. Various protected areas, including the Sierra de las Nieves Natural and National Park, the Sierra de Grazalema Natural Park and Los Reales de Sierra Bermeja Natural Site, together with the numerous Special Areas of Conservation (SAC) present in this territory, help to safeguard this extraordinary relict tree. Likewise, its forests are integrated into the framework of the European Ecological Network NATURA 2000, through the declaration of these forests as "habitat of Community interest" (9520 Abies pinsapo Clemente ex Boiss.) from Directive 92/43/EEC. Along these lines, in recent years various programmes and projects have been developed to combat the main threats affecting this fir tree and to promote its conservation, recovery and sustainability, including the I y II Plan de Recuperación del Pinsapo, both developed by the Andalusian Regional Government, and various actions included in the Estrategia Andaluza de Gestión Integrada de la Biodiversidad. To date, these actions have been justified according to different sources of an imprecise nature, such as species distribution models (SDM), studies of current habitats or historical sources. The contributions derived from the aforementioned sources are relatively abundant. However, the paleobiogeography of the Spanish fir continues to show numerous scientific gaps. This is despite the fact that the study of the distribution of the species, as well as their relationships with the environment in which they develop, inevitably requires knowledge of their historical evolution. It is essential to interpret all the information of a paleoecological nature, as reading it can provide many of the keys that help us to understand the present distribution of certain plant taxa. Even more so when dealing with relict species such as the Spanish fir, the only Iberian Mediterranean fir that has withstood for centuries a series of disturbances in the form of fires, pests, anthropic actions or, more recently, the adverse environmental conditions resulting from climate change. Consequently, it is necessary to implement proven scientific methodologies that allow us to carry out precise paleobiogeographical reconstructions over a broad temporal scale. In view of this consideration, the starting hypothesis is based on the existence of a theoretical area of distribution of Spanish fir forests that was more extensive and continuous than the present one in the western Baetic Cordillera in the past. To corroborate this assertion, in this research pedoanthracological analysis is used as the main methodological basis. Specifically, 35 pedological samples were taken at different locations in the Serranía de Ronda, coinciding with those potential enclaves where A. pinsapo may have been present in the past. The results, after the taxonomic analysis of 4126 charcoal fragments and the radiocarbon dating of a total of 77 samples, with chronologies ranging from 14 013-13 440 cal BP (cal: calibrated age; BP: before present) to the present day, have confirmed the existence of the genus Abies in several locations where this taxon is not currently present. Specifically, Spanish fir charcoal has been found in mountainous reliefs located between the three current populations of the Spanish fir, demonstrating their connection from a paleobiogeographical point of view. Together with the main objective of this thesis project, the large volume of samples analysed has provided complementary information, although of great paleobiogeographical importance, on other singular tree taxa, such as Pinus nigra/sylvestries type, which is currently absent in the Serranía de Ronda, confirming the role that certain mountainous reliefs of the Serrania de Ronda have played as postglacial refuges. The results confirm, once again, how useful the paleobiogeographical approaches are. The information derived from these studies, integrated in a coherent way with that of all other available sources, can be a highly valid resource for the development of actions aimed at the conservation of those forest that are most vulnerable to climate change. In the case of the present research, this applied character has been specified in the proposal for an ecological corridor in Sierra Bermeja, as well as in different reforestation tasks of Spanish firs planned in various locations of the Serranía de Ronda. However, and despite the significant progress made, the present research constitutes a first approach to the past distribution of A. pinsapo; the line of future work involves continuing to obtain paleobiogeographical information that will allow us to know in greater detail the distribution and dynamics experienced by the Spanish firs, as well as the different disturbances that reduced its greater extent in the past to its current distribution. To this end, it is imperative to extend the pedoanthracological sampling network to the whole of the Baetic System.