Effects of abiotic and anthropogenic factors on the spatial distribution of Quercus faginea in the Spanish Central Pyrenees

Abstract

Abiotic factors often are the most important factors influencing a species' distribution. Nevertheless, when investigating the underlying causes of a species' distribution, it is important to assess both the abiotic and the anthropogenic factors (land-use variables) that might have influenced the species' distribution. That is especially true in the Mediterranean Basin, where natural ecosystems have undergone significant changes in response to anthropogenic pressures in the region. In this study, we examined the effects of abiotic and anthropogenic factors on the distribution of Quercus faginea in the Spanish Central Pyrenees. Information on the presenceabsence of Q. faginea, and abiotic and anthropogenic variables, were derived using GIS based on digital maps and aerial photographs. To identify and quantify the factors that have affected significantly the spatial distribution of Q. faginea, we used Bayesian Model Averaging and hierarchical partitioning. In the Spanish Central Pyrenees, on a broad scale, abiotic variables; i.e. climate and lithology, were the factors that had the greatest effect on the spatial distribution of Q. faginea; however, recently introduced pine plantations and previous livestock pressure have had a negative effect on the distribution of Q. faginea in the region.

Spatio-temporal dynamics of Quercus faginea forests in the Spanish Central Pre-Pyrenees

“…Accordingly, in the Central Pre-Pyrenees, Q. faginea forests have expanded at lowlands with relative to highlands. Currently, almost all of the areas occupied by these forests are located between 450 m and 1,500 m of altitude (Kouba et al 2010). Furthermore, the results revealed a high probability of loss at sites with low slope.…”

“…Maps of the cost distance to the nearest pasture and cropland were measures of transportation costs, i.e., calculate the least accumulative cost for moving from the source pixel (in this case pasture or cropland) to each of other pixels using slope as cost layer. The cost increase with an increasing of slope values up to 35°, beyond this steepness, areas were considered inaccessible to man and livestock (Kouba et al 2010). All maps were subset to identical extents at a spatial resolution of 20 m. Moran's I correlogram (Legendre and Legendre 1998) was used to assess the spatial autocorrelations (SAC) of the dependent variables.…”

“…On gentle slopes, Q. faginea forests were harvested and the land was used for cereal cultivation (Lasanta-Martínez 1989). These developments restricted Q. faginea to poor soils and stony hillsides (Kouba et al 2010). This finding suggests a difficulty in separating the possible role of abiotic factors from land use changes, as they are closely interrelated (Poyatos et al 2003).…”

“…Moreover, forest fragmentation and loss might have significant ecological implications for species dependent on high-quality habitats situated in the interior regions of forest patches (Echeverria et al 2006). Given that the Q. faginea forests are nowadays highly appreciated in many Mediterranean environments as a consequence of being an invaluable habitat for outstanding biodiversity of plant and animal species, they have recently been of great interest for ecosystem conservation (Rey Benayas et al 2005, Kouba et al 2010. A decline in the amount of Q. faginea forests and increasing fragmentation of Q. faginea patches mean less habitats are available for a multitude of mammalian, bird, insect, bryophyte, and other species associated with these forests.…”

“…In the nineteenth and the early twentieth centuries, an increase in the human population amplified the need for arable lands and pastures. Q. faginea forests were harvested to increase the amount of arable lands available for the production of food, including the grazing of livestock for supporting the growth of human population (Kouba et al 2010). Recently, the proliferation of conifer plantations, especially Pinus sylvestris and P. nigra, has drastically changed the structure and composition of forests (Amo et al 2008) to the detriment of Q. faginea and other indigenous forest species.…”