Modeling Tree Loss Versus Tree Recruitment Processes in SW Iberian Rangelands as Influenced by Topography and Land use and Management

Abstract

AbstractThe sustainability of Iberian open wooded rangelands is threatened by recent land use changes and lack of tree recruitment. As trees are key elements of these systems, the characterization of their spatiotemporal trend is essential for the system's management. Our objective is to develop spatial models reflecting the temporal dynamic of trees in terms of recent tree loss and tree gain processes in farms, evaluating the influence on the models of topography and land use and management. Aerial photographs of 1956 and 2009 were compared, analyzing lost and new trees in five dehesas of Extremadura (Spain). Multivariate adaptive regression splines was used to produce the spatial models that characterize the proneness of an area to undergo tree loss or recruitment. Models showed good performances. Although land use and management intensively influenced on tree dynamics, because it depends on topography, models built by considering just the topographic variables showed only slightly lower fitness. Tree recruitment mostly happened in the marginal places with steep slopes, while tree loss occurred in elevated, gently undulated and more intensively used places of the farms. A spatial polarization of both processes has been observed that leads to the lack of replacement of lost trees. The work provides some clues on the design of tree management procedures for dehesas and montados. The implementation of measures to address the degradation processes in dehesas should take into account the spatial arrangement of the areas where tree loss or gain is actually happening or it is likely to occur. Copyright © 2017 John Wiley & Sons, Ltd.