Spatio-temporal analysis of oak decline process in open woodlands: A case study in SW Spain
Autor
Fernández Habas, Jesús
Fernández Rebollo, Pilar
Rivas Casado, Mónica
García-Moreno, Alma María
Abellanas Oar, B.
Editor
ElsevierFecha
2019Materia
Phytophthora cinnamomiDehesa ecosystems
Multivariate Adaptive Regression Splines
InhomogeneousRipley's K-function
Afforestation
Disease spread
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This study aims to characterize at landscape level the spatio-temporal dynamics of a
massive oak decline that is occurring in dehesas ecosystems. We are looking at possibilities
of matching with Phytophthora disease behavior, a harmful disease detected in the studied
area, in order to interpret its implications within the context of the disease management.
Spatial locations of affected trees from 2001, 2009 and 2016 identified through
photointerpretation were analyzed with the inhomogeneous Ripley's K-function to assess
their spatial pattern. Multivariate Adaptive Regression Splines (MARS), a non-parametric
data mining method, was used to investigate the influence of a range of landscape
descriptors of different nature on the proneness to oak decline, using the location of affected
trees in comparison with that of healthy spots (points randomly extracted from areas covered
by healthy trees).
Affected trees showed a strong clustering pattern that decreased over time. The reported
spatial patterns align with the hypothesis of Phytophthora cinnamomi Rands. being the main
cause of oak decline in Mediterranean forests. Location of affected trees detected in different
years was found to be spatially related, suggesting the implication of a contagion process.
MARS models from 2001, 2009 and 2016reported Area Under the Curve (AUC) values of
0.707, 0.671and 0.651,respectively. Slope was the most influential landscape descriptor
across the three years, with distance to afforestations being the second for 2001 and 2009.
Landscape descriptors linked to human factors and soil water content seem to influence oak
decline caused by Phytophthora cinnamomi at landscape level. Afforestations carried out as
part of the afforestation subsidy program promoted by the European Commission in 1992
could have acted as an initial source of Phytophthora cinnamomi infection. These findings
together with the consideration of the spatial and temporal scale of the spreading are
essential when planning the management of oak decline in open woodlands.