The interpolated abundance estimated from DAFOR scores of Calluna vulgaris from all surveys. Interpolation was conducted using universal kriging with altitude used as the covariable. The variogram was constructed using a width of 2,000m and a cutoff of 40,000m.  
  Part of: Groom Q, Durkin J, O'Reilly J, Mclay A, Richards A, Angel J, Horsley A, Rogers M, Young G (2015) A benchmark survey of the common plants of South Northumberland and Durham, United Kingdom. Biodiversity Data Journal 3: e7318.