Spatial data from aerial images
Within the part of the valley which was covered by aerial images, the highest vegetation cover was found in the south-eastern part, in long patches along the elevation gradient of the studied valley (Fig. 1B). The area of mounds varied between 0.87 and 82.81 m2(mean 25.21 ± 17.80). If extrapolated to the whole area of the cluster and all burrows there, mounds cover between 0.06 and 0.35% of the high cluster and between 0.07 and 0.42% of the low cluster. The total vegetation cover in a 20 m buffer around a burrow varied between 0.27 and 34.64% (mean 8.63 ± 8.42%) (Fig. 2B). The mean distance from the closest burrow entrance of bare soil hexagons was similar in all buffers and varied between 13.24 and 14.07 m (mean 13.58 ± 0.19). The mean distance of vegetation hexagons was more variable, between 9.66 and 18.48 m (mean 13.42 ± 1.67). In 17 burrows vegetation hexagons were more than 1 meter closer to the nearest burrow than bare soil hexagons (mean) and in 14 burrows more than 1 meter further (Fig. 2A). The adjusted R2 values of the relationship between vegetation cover and the distance from the closest burrow entrance, based on linear models measured for 47 buffers varied between 0.13 and 0.96 (mean 0.54 ± 0.3) (Fig. 2C). We visually identified four types of relationship: negative linear (18 buffers), positive linear (14), unimodal, with the highest values of vegetation cover at intermediate distances from the burrow entrance (10) and no relationship (R2< 0.1) (Fig. 1D, Fig. 3). We found no significant correlation between any of the parameters measured for each burrow (total vegetation cover, mound area, mean distance of vegetation hexagons, adj R2 from the linear model).