1. National Forest Inventory for Great Britain

2. Woodland Map NFI Woodland definition for Great Britain:
All woodland (urban and rural) >= 0.5 ha in size.
Canopy cover of >= 20% tree canopy cover (or potential to achieve this).
Minimum width of wood >= 20m
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3. Woodland Map Creation
The map is validated and updated using automated interpretation of satellite imagery, which gives an independent and current cross-check of woodland present. Satellite imagery is also used to identify recently felled areas
Map ‘hand’ created by visual interpretation of 25 cm resolution aerial photography, identifying woodland and interpreted forest types of broadleaved, conifer, felled and uncertain
A few pictures to explain…
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4. Sampling the Woodland Map
Systematic grid
Squares selected from the grid within the map
Selection based upon random sampling
Statistical science used to determine survey design
Same approach whether working at the whole of GB or the microscopic – Academic friend uses same approach for surveying Axons in nerve endings – too many to count – systematic and random grid (~66% : 33%), more accurate than counting them all!!
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5. A Sample Square
Square stratified into woodland and land use types (blue lines)
Each strata has assessments taken (e.g. in box to left of image)
Each woodland strata has sample plots allocated (red circles)
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6. A Sample Plot Each plot located and marked on ground (red circle)
All trees > = 4 cm diameter (DBH) plotted and measured (small circles)
Subset of trees where heights and crown dimensions taken (box to left)
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7. Scaling Up Results
1. Forest Map, broken into interpreted forest types (IFT)
2. 15,000 one Ha Survey Squares
3. Map + Squares brought together and spatial relationships between the two computed
4. Results scaled up within IFT classes, and overall results found from summing or averaging the scaled up results across IFT classes X
MAP
The map gives us:
Area
Interpreted Forest Types
Interpreted Open areas
In the future, it will give us changes in these, by comparing successive maps.
This constitutes a near census of the whole population, which is very accurate. FC can achieve this by making use of Remote Sensing. FC will currently use Aerial Photography, but will also use other forms of RS, as they become usable.
FIELD SAMPLING
We need to know more than just area and the IFT and have to go a step further to find out more detailed information about the forests. We achieve this through sending surveyors out into the field to observe and measure a proportion of the forests. This will tell us things like:
Species
Age
Top height
Dbh
Habitat, etc
The field measurements and the proportion of the samples that they represent are then multiplied by the total forest area from the map, to give a total estimate of that reporting requirement
5. NFI Statistics Produced
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8. Survey Outputs Natura 2000 habitat types Habitat condition
Structure & composition
NVC – vegetation types
Deadwood
General health & invasive species
Ground, field & shrub layer
Natural regeneration
Veteran trees
Rivers, streams and ponds
Boundary & cultural features
Social value
Access factors
Management practice
Woodland area / change
European forest types
Mensuration assessments:
Diameter at breast height
Heights and crown sizes Stocking
Species
Standing metrics of:
Biomass in forest
Carbon stored in forest
Timber
Assessment of growth rates allowing for forecasts of:
Increment
Biomass
Carbon storage
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