Holm oak wood pastures in SE Portugal: a spatial and temporal multiscale approach

Montados are oak wood-pastures occupying 11% of the Portuguese territory. This agroforestry system has been traditionally used for animal husbandry, agricultural, and forestry purposes. Present day Montados are threatened by land use changes, either intensification or abandonment, and climate global warming that has fostered parasitic plagues and enhanced hydric stress. This study highlights the relevance of holm oak (Quercus rotundifolia) wood-pastures in SE Portugal’s landscape throughout the last 125 years and assesses its health condition for the last two decades aiming to evaluate the chances of its continuity. Spatially, we use the Portuguese territory on the left bank of the Guadiana river for the historical changes on land use, and 6 farmlands located within this region to analyse present day tendencies. Temporally, we consider the intervals 1890–2015 and 2006–2019. We analysed five land use maps from different dates using ArcGIS to access holm oak Montados’ areas in the different dates to analyse its variation over time. We used Google Earth’s images to evaluate the present-day tendencies in tree density and mortality. Results indicate that holm oak woodland distribution in the study area increased during the twentieth century having maintained quite stable from the 1990’s to the present day. However, a negative trend in tree density during the latter period was found. We also verified that tree natural regeneration is not enough to replace dying trees hinting towards a conversion of grazed woodlands into treeless pastures, concluding that if these tendencies persist the continuity of the holm oak agroforestry system in south-eastern Portugal may be threatened.