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    Author(s): W.W. Dillon; S.E. Haas; D.M. Rizzo; R.K. Meentemeyer
    Date: 2014
    Source: European Journal of Plant Pathology 138: 449-465
    Publication Series: Scientific Journal (JRNL)
    PDF: View PDF  (6.31 MB)


    The challenge of observing interactions between plant pathogens, their hosts, and environmental heterogeneity across multiple spatial scales commonly limits our ability to understand and manage wildland forest epidemics. Using the forest pathogen Phytophthora ramorum as a case study, we established 20 multiscale field sites to analyze how host-pathogen-environment relationships vary across spatial scales of observation in a wildland pathosystem. We developed statistical models of disease intensity across five nested levels of spatial aggregation, from an individual host through four broader spatial extents of observation. Analyses were conducted from two spatial perspectives: a focal view, where disease intensity at one scale was examined as a function of broader-scale landscape conditions, and an aggregate view, where disease intensity and landscape conditions was observed at the same scale of spatial aggregation. For each perspective, separate models were developed to compare direct field measurements of host density versus less expensive remotely sensed estimates of host habitat as predictors of disease in landscape-scale studies. From both perspectives, models using direct measurements of host density performed better than models using remotely sensed estimates of host habitat across all four spatial extents. We found no significant difference in model performance at the individual level. From the focal view, the performance of host density models declined with increasing spatial extent, whereas the performance of host habitat models improved with spatial extent. These results illustrate how the scale of observation – both spatial extent and measurement detail – can influence conclusions drawn from epidemiological models of wildland pathosystems.

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    Dillon, W.W.; Haas, S.E.; Rizzo, D.M.; Meentemeyer, R.K. 2014. Perspectives of Spatial Scale in a Wildland Forest Epidemic. European Journal of Plant Pathology 138: 449-465.


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    Host density, landscape epidemiology, multilevel, multiscale, Phytophthora ramorum, Sudden oak death

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