For acidity critical loads all unmanaged woodland is treated the same and mapped in a single category. For nutrient nitrogen critical loads unmanaged woodland is mapped in four separate classes: acidophilous oak-dominated woodland; beech woodland; Scots pine woodland; other areas of unmanaged woodland (ie, areas of unmanaged woodland not included in the other three classes). For calcareous grassland, areas with soil acidity critical loads <2.0 keq ha-1 year-1 are excluded from the habitat distribution map used for mapping acidity critical loads.
There are some small differences in the area of habitats mapped for acidity and for nutrient nitrogen as the distributions are restricted to areas for which data exist to calculate critical loads nationally for each habitat type.
Please refer to the UK Status Reports for further information.
It should be noted that the terrestrial habitat area data are based on the habitat distribution maps generated for UK critical loads (acidity, nitrogen) research and (a) only include areas where data exist for the calculation or derivation of critical loads; (b) may differ from other national habitat distribution maps or estimates of habitat areas.