The National Forest Inventory will include:
- Any forest or woodland (urban or rural) that is at least 0.5 hectares in area with a minimum width of 20 m.
- Any forest or woodland area that has at least 20% tree canopy cover (or the potential to achieve this).
This will help to ensure that the Inventory aligns with national and international reporting standards.
The location and extent of all forests and woodlands will be recorded, stored and maintained as digital map data that can be rolled back or forward in time to give estimates of change between reporting periods. The map will distinguish between various forest types, for example conifers, broadleaves or mixed.
Base map data
The base map data has been captured from 1:10,000 aerial photographs. Interim updates will be based on satellite and operational data and confirmed as and when more recent aerial photography is available.
The map data will be capable of being combined with other spatial and attribute data (including planned management intervention) from field surveys.
Measurements collected from field survey will be linked to area data derived from the maps in order to generate quantitative and bounded estimates of woodland structure, composition and size.
Field surveys
Field surveys will be undertaken in 15,000 x 1 hectare sample square plots. The size of the survey has been designed to achieve the desired level of accuracy for key outputs from the Inventory. The plots, selected by a random process designed by Forestry Commission statisticians, will cover forests and woodlands in England, Scotland and Wales.
The majority of plot locations will be permanent, to allow changes to be monitored and so that tree growth can be calculated. This approach gives considerable flexibility for post sampling stratification and analysis. Where more intensive sampling of particular forest or forest habitat types is needed the ’Top up’ principle will apply.
Field data will be collected on a 5-year cycle starting in 2009.
The following animation shows how the base map and the field survey plots link together to generate the inventory information (opens in new window).