NFI woodland ecological condition in Great Britain: Methodology National Forest Inventory Issued by: National Forest Inventory, Forestry Commission, 231 Corstorphine Road, Edinburgh, EH12 7AT Date: February 2020 Enquiries: Ben Ditchburn, 0300 067 5561 [email protected] Statistician: David Ross [email protected] Website: www.forestresearch.gov.uk/inventory www.forestresearch.gov.uk/forecast NFI woodland ecological condition methodology Contents Introduction ...................................................................................................... 5 The NFI .......................................................................................................... 6 Why report on woodland ecological condition? ...................................................... 7 Development of the NFI condition monitoring approach .......................................... 9 Assessing broad and priority woodland habitat condition ...................................... 9 NFI WEC indicator selection .......................................................................... 10 Classifying and scoring woodlands ................................................................. 14 A straightforward, transparent and evidence-informed approach ......................... 15 Methodology .................................................................................................... 16 Categorising woodland area for reporting ........................................................... 16 Defining the native woodland population: identifying woodland type .................... 17 Classifying woodland habitat types ................................................................. 20 NFI survey square data structure ..................................................................... 20 Quality assurance ........................................................................................ 22 Extrapolating NFI field survey statistics to a reporting area ................................ 23 The NFI Condition Calculator ........................................................................... 23 Individual indicator assessment details ................................................................ 24 Population-level indicator methods: woodland area and loss ................................. 24 Stand-level indicators ..................................................................................... 25 1. Age distribution of trees .......................................................................... 26 Background ................................................................................................ 26 Data and method used for indicator measurement ............................................ 26 Classification .............................................................................................. 27 2. Wild, domestic and feral herbivore damage ................................................ 27 Background ................................................................................................ 27 Data and method used for indicator measurement ............................................ 28 Classification .............................................................................................. 31 3. Invasive plant species ............................................................................ 32 Background ................................................................................................ 32 Data and method used for indicator measurement ............................................ 33 Classification .............................................................................................. 33 2 NFI woodland ecological condition methodology 4. Number of native tree and shrub species ................................................... 34 Background ................................................................................................ 34 Data and method used for indicator measurement ............................................ 34 Classification .............................................................................................. 35 5. Occupancy of native species .................................................................... 35 Background ................................................................................................ 35 Data and method used for indicator measurement ............................................ 36 Classification .............................................................................................. 36 6. Open Space within woodland ................................................................... 36 Background ................................................................................................ 36 Data and method used for indicator measurement ............................................ 37 Classification .............................................................................................. 39 7. Proportion of favourable land cover around woodland .................................. 41 Background ................................................................................................ 41 Data and method used for indicator measurement ............................................ 41 Classification .............................................................................................. 42 8. Woodland regeneration ........................................................................... 43 Background ................................................................................................ 43 Data and method used for indicator measurement ............................................ 43 Classification (component group- and square-level) .......................................... 44 9. Tree health ........................................................................................... 46 Background ................................................................................................ 46 Data and method used for indicator measurement ............................................ 46 Classification .............................................................................................. 49 10. Vegetation and ground flora .................................................................... 49 Background ................................................................................................ 49 Data and method used for indicator measurement ............................................ 50 Classification .............................................................................................. 51 11. Vertical structure ................................................................................... 53 Background ................................................................................................ 53 Data and method used for indicator measurement ............................................ 53 Classification .............................................................................................. 53 3 NFI woodland ecological condition methodology 12. Veteran trees ........................................................................................ 54 Background ................................................................................................ 54 Data and method used for indicator measurement ............................................ 54 Classification .............................................................................................. 54 13. Volume of deadwood .............................................................................. 55 Background ................................................................................................ 55 Data and method used for indicator measurement ............................................ 55 Classification .............................................................................................. 56 14. Size of woodland ................................................................................... 57 Background ................................................................................................ 57 Data and method used for indicator measurement ............................................ 58 Classification .............................................................................................. 59 15. Overall stand-level condition score ........................................................... 59 Background ................................................................................................ 59 Method used for assessment ......................................................................... 60 Classification .............................................................................................. 60 Applying the NFI WEC scores to decision making .............................................. 61 Future work ..................................................................................................... 62 References ...................................................................................................... 64 Appendices ...................................................................................................... 76 Glossary ....................................................................................................... 107 NFI national reports ........................................................................................ 114 4 Introduction The National