The new forests of Spain 1956-2008: an assessment of landscape structure and connectivity

After centuries of incremental loss of forest lands in Spain, new forests began to appear in the 20^th century. Several reasons led to this trend shift, including the implementation of the first national reforestation plan in the 1940´s, the decline of silvo-pastoral practices, and the abandonment of less productive agricultural lands. New forests have been established as a result of tree planting and natural regeneration.

Our aim was to describe the current status of these new forests, at the national scale, and assess if they have produced major changes in the composition and structure of the landscapes where they occur. Furthermore, we analysed their landscape ecological impact by considering resultant changes in forest habitat connectivity.

Accordingly, we used data from the Spanish Rural Landscapes Monitoring System: SISPARES project (González-Ávila & Elena-Rosselló 2009; www.sispares.com). SISPARES data were obtained from a network composed of 206 4x4 km² landscape sample plots. These samples were identified using the Spanish biogeoclimatic classification CLATERES, which allowed a national stratified design. In each sample, land-use and land-cover types, including woodland, re-forestation and scrubland, have been photo-interpreted. Geodata have been produced for four dates: 1956, 1984, 1998 and 2008. Table 1 shows the trend followed by the re-forestation patches in the studied period.

In order to identify the areas where new forests have appeared, we quantified their associated processes in each sample and each of the three SISPARES periods. A change-patch characterization was produced to better understand the linkages between the landscape structures and the processes that resulted in new forests. Moreover, changes in forest habitat connectivity, in terms of habitat availability, were also quantified using the Probability of Connectivity (PC) index, which is particularly suited for landscape-conservation planning and change-monitoring applications (Pascual-Hortal & Saura 2006; Saura & Pascual-Hortal 2007). We used Conefor software (Saura & Torné 2009) to calculate the required values. Results are of importance to discussions about the role played by the new forests at the landscape level (structure, function and dynamics) and potential future changes in the country.