Landscape epidemiology of ash dieback

Ash dieback is induced by Hymenoscyphus fraxineus, an invasive pathogenic fungus. It is causing severe damage to European ash populations. However, the local environment, such as climate or site conditions, is known to affects ash dieback.
We studied the landscape epidemiology of the disease on a 22 km² area in north-eastern France at two stages of the invasion process using Bayesian spatio-temporal models fitted with integrated nested Laplace approximation (INLA). Several features characterizing disease severity, crown dieback, frequency of collar canker, and density of infected leaf debris in the litter were determined on a regular grid over a 3.5 x 6.5 km area. We first analysed the effect of landscape features on the disease establishment stage in 2012, two years after the first report of the disease in the area, and then on further disease development, in 2016–2018.
Landscape features had little impact on the disease at the establishment stage but strongly determined its further d..., Data was collected by ground survey during a period of 7 years on a network of plots located on a systematic grid design.
Plots were established on grid nodes with ash (100–111 depending on the year).
Data were collected:
- Ash basal area: measure of ash tree circumference on plots with fixed surface (128, 800 and 1250 m² depending on their diameter at breast height)  sum of tree basal area weighted by the surface of the plot on which they were measured  This was used to compute the Ash density in the neighbourhood (HAN, host abundance in the neighbourhood)
- rPA100 is a tree cover fragmentation index computed from a polygon of tree cover within 100 m from plot center.  The polygon is derived from the tree cover IGN shape file VEGETATION.shp (http://professionnels.ign.fr).   rPA100 is the perimeter/area ratio for that polygon
- Ash health status: visual assessment of crown condition and of collar canker presence
- Hymenoscyphus fraxineus presence: qPCR test in laboratory on samples take..., Information in the uploaded readme.csv file.