The potential for native woodland in Scotland:
the native woodland model Management

Natural Heritage Management

• Executive Summary
• Introduction
• Assumptions and general principles underlying the Native Woodland Model
• The value of modelling potential woodland cover
• Methodology
• How accurate is the NWM?
• How potential woodland types correspond to HAP types
• Use of the Native Woodland Model – case studies
• References
• Appendix 1 The base datasets
• Appendix 2 The National Vegetation Classification
• Appendix 3 Allocation of woodland types to different site conditions
• Appendix 4 Correspondence between NWM and HAP types

How potential woodland types correspond to Habitat Action Plan types

Habitat Action Plans (HAPs) have been developed for each of the main types of native woodland in Scotland. Each category of the NWM output has been classified (Appendix 4) either as one of these types, as overlap or as non-HAP, as follows:

• Where the NWM output is a single NVC type this is generally interpreted following Hall & Kirby (1998). As the NWM does not predict woodland types to sub-community level, there are a few differences:
  • W7 is allocated to ‘Upland mixed ash’
  • W4 is allocated to ‘Northern birchwoods’.
• NWM mosaics are interpreted as single HAP types, or as mixtures of types, in order to preserve the information in the secondary mosaic component:
  • The mosaic ‘W9+W7’ is allocated to ‘Upland mixed ash’, because W9 and W7 both fall within this HAP type.
  • The mosaic ‘W17+W4’ is classified as a mosaic of ‘Upland oak’ and ‘Northern birchwood’.
• Additional rules are needed to deal with non-NVC types:
  • ‘W7+peatland with scattered trees/scrub’ has been assigned to ‘Wet woodland’ because it is associated with a wet, peatland secondary component.
  • Mosaics beginning ‘W4 with open ground’ have been assigned to ‘Northern birchwood’ regardless of the other components of the mosaic.
  • ‘Basin bog woodland/ scrub’ has been assigned to ‘Wet woodland’, although it could also be associated with ‘Native pine woodland’.
• NWM interchangeable types are classified as overlaps between HAP types unless both components fall within a single category:
  • W17/W18 and W18/W17 are classified as ‘Upland oak/Native pine woodland’
  • W10/W8 is assigned to ‘Mixed broadleaved woodland’.
• NWM non-woodland types (unsuitable for tree/scrub growth, developed rural land, built-up land, inland water, peatland with scattered trees/scrub, the various categories of montane scrub and W19 Juniper woodland with wood sorrel) are translated as ‘Non-HAP’. It should be noted that some of these categories may comprise non-woodland HAP types.

This enables the NWM to be used for developing strategies for restoring particular native woodland HAP types. An example is given in the following section, where the potential for restoring and expanding upland ashwood on north Mull is explored.

Upland oak woodland