Spatial oak decline models to inform conservation planning in the Central-Western Iberian Peninsula

Abstract

Abstract In the Iberian Peninsula, Oak Decline (hereafter, OD) is becoming a serious and frequently occurring disease in Mediterranean oaks. Decline processes seem to involve multiple biotic and abiotic factors, which combine to reduce the vigour of oak trees often causing death. However, the exact causes of its extension are still unknown and therefore, given the ecological, economic and social relevance of these trees in Mediterranean countries it is crucial to develop tools that allow us to anticipate its occurrence and to reduce its expansion. In this sense, the present work aims to (i) unravel the relative role of environmental factors on the distribution of one of the most important phenomena that threat the biodiversity of the Iberian oaks, and (ii) to produce a spatially explicit model of OD risk, to assist conservation managers dealing with this phenomenon. To this, we have used a dataset of OD foci gathered during the period 2015–2017 by the program “Methodology for the inventory and monitoring of oak masses affected by the decline of oak in the southwest of Castilla y Leon” (this region is beginning to suffer the damages of this disease). In total, 68 locations were used to assess relationships with environmental factors (topographic conditions, abiotic stress conditions and human influence) using maximum entropy models (hereafter, MaxEnt) and variance-partitioning. OD distribution seems to be principally influenced by land-use (mainly dehesas), followed by dryer areas and areas with low slope gradients facing south or southeast. The resulting model has been used to produce a detailed OD risk map in central-western Spain. Our modelling approach may contribute to inform conservation planning and to establish the adequate management policy for Iberian oak dehesas, by helping to identify regions where the risk of OD is high.