Assessing regional species pools for restoration programs in Spain

The relationship between current and potential distribution in 34 main Spanish forest tree species (data from the Third Spanish Forest Inventory) was determined using a Maximum Entropy functional approximation with climatic data as predictive variables. A method for detecting regional species pools at two different scales: biogeoclimatic classes (CLATERES classification), and forest landscape types (WWF classification) has been proposed. Then, the Absence percentage for a species (i.e. the proportion of landscapes types or biogeoclimatic classes in which the species is included in the regional species pool but is actually not present) was determined. Results show higher figures of Potential Species Richness in the Pyrenees and the Cantabrian Range, while inland or coastal Mediterranean semiarid landscapes have lower figures. Using a classification based on biogeoclimatic variables (CLATERES) improves precision when estimating Absent Species Richness. Absence percentage is zero or close to zero for five species ( Pinus uncinata , Quercus robur , Quercus ilex , Quercus humilis and Juniperus communis ), while for other six species ( Acer pseudoplatanus , Fraxinus angustifolia , Alnus glutinosa , Populus alba , Sorbus aucuparia and Pinus pinea ) the figures are higher than 0.6, which means the species is absent in more than 60 % of the landscapes or biogeoclimatic classes that it could inhabit. The relationships between tree life traits and the absence of species from the ecosystems studied is slight but non-dominant species, species not subjected to forest management, or zonal species are less widely distributed that their climatic potentiality indicates.