The combination of biotic and abiotic factors (climate, orography, lithology, interspecific competition, etc.) and the pathogenicity of agents such as the fungus Phytophthora cinnamomi Rands has generated the phytosanitary disease known as the oak decline (la seca) in holm oak and cork oak stand of the Iberian Peninsula. The aim of this study is to analyse the role played by environmental variables in the development of this disease, and to determine which have a stronger influence in the spread of the disease. Data has been obtained from Monte de Valdelatas, Alcobendas, Madrid (sheet 534 national topographic map, scale 1:50.000, UTM coordinates X: 442592.51, Y: 4487266.63 zone 30T). Field samples were taken from 100 randomly selected Quercus ilex subsp. ballota individuals (50 with a healthy appearance and 50 that showed disease symptoms), located within 7 transects. In relation to the statistical model, in this work a binomial model was used. On it, the response variable was defined as healthy/unhealthy, depending on the appearance of each tree. Akaike Information Criteria (AIC) was used to define the quality of the model. We selected model obtained a score of 89.68 and accounts for approximately 44% of data variability (D2 = 0,437). The main environmental variables that impact disease were: proximity to river course, topographic wetness index, cover of Daphne gnidium and Quercus ilex subsp. ballota, and the age of the individuals. Given the loss of Quercus forest mass caused by the spread of the oak decline disease, detected in several countries, including Spain, it becomes necessary to adequately understand the different factors that contribute and, in some cases, is the cause of the expansion of the disease, as well as to identify any inhibiting factors.
