Investigating the role of topography on the temporal dynamic of trees in mediterranean wooded pasturelands

Iberian dehesas and montados are considered as highly valuable systems and examples of sustainable farmland practices. However, tree aging and the lack of tree recruitment are being mentioned as threads to its long-term conservation. At the same time, shrub encroaching due to land abandonment is happening in some areas, thus facilitating tree recruitment over those places. These farmland systems are highly determined by their history of land use and management. We hypothesized that the recent spatial-temporal dynamic of tree loss and tree recruitment could be adequately explained by land topographic features as final physical drivers of land use/management processes in dehesas and montados. By comparing aerial images taken in 1956 and 2009, we analyzed the temporal tree dynamics of four dehesa farms in Caceres (Spain). Multivariate Adaptive Regression Splines (MARS) were used to build spatial models that explain the susceptibility of farm areas to tree recruitment or tree loss as determined by topography. Based on the high model fitness we conclude that some topographical features satisfactorily explain the recent temporal tree dynamics in dehesas. Areas prone to tree recruitment are mainly restricted to marginal areas of steep slopes and spatially segregated from areas of tree loss, so that no real replacement occurs at the local scale.