NWSS - Glossary of Terms

This glossary is intended to cover the full range of means by which the results of the Native Woodland Survey of Scotland (NWSS) are being communicated and so some terminology is only used in specific routes, i.e. some terms required for web browsers will not be found in reports.

Symbols used

* indicates a species which is classed as native for the purpose of the survey.

+ indicates a species is a shrub not a tree.


attribute: descriptive data in a polygon.


BAP: a UK Biodiversity Action Plan broad habitat type. e.g. acid grassland.

base map: the polygons used for locating additional layers, or types, of georeferenced information.

browser: A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web.


canopy cover: the % of the polygon area covered by trees/shrubs.

component: a row of attribute data in a table, belonging to a polygon: there can be more than one component per polygon in a table.

condition: shorthand for an expression of ecological or nature conservation condition which relates to the ecological processes, structure and species composition within a woodland.


database: data record structure and repository: a GIS database contains the spatial location and shape of geographic features recorded as points, lines and polygons, as well as their attributes.

deadwood volume: deadwood is woody material that is no longer alive, both on trees or and on the woodland floor. Volume has been calculated using a count of snags (standing dead stems) and fallen dead stems and branches, including stumps, over 0.5m in length and 10cm diameter.

DBH: the diameter of a tree at breast height.

Dominant: >50% of a polygon.


established regeneration: trees >1m height and <7cm DBH (up to and including large sapling but not ‘pole stage’ trees). Usually <5m height but DBH overrides height in determining this class.


geo-referenced: establishing a feature’s location in terms of map projections or coordinate systems.

GIS: a Geographic Information System is an organized collection of computer hardware, software, and geographic data designed to capture, store, update, manipulate, analyse and display all forms of geographically referenced information.

green cover (for all PAWS sites): The overall proportion of the polygon covered by non-woody green vegetation. This assessment was confined to PAWS sites and included both the combined overall cover of the “ground” layer (predominantly bryophytes) and the field layer (herbaceous plants/forb). Estimated growth is based on anticipated summer growth, if not highly visible during winter.


habitat: a woodland unit (polygon) that are defined by both their priority woodland type and NVC woodland communities (if identifiable) or are open areas, defined by broad habitat types.

herbivore impact: a description of the overall impact of herbivores on a woodland. It is based on visual estimates of the extent of browsing (epicormic shoot or basal shoots), bark stripping/fraying on trees and some shrub species, the extent of any visible poaching or ground disturbance caused by herbivores and an assessment of the canopy fragmentation. This is reported as an overall rating on a scale from A (lowest impact) to F (highest impact).


IFT: Interpreted Forest Types are woodland categories defined in the digital woodland map and National Forest Inventory (NFI) from the interpretation of aerial photography, e.g. conifer (C), new planting or young trees (N).


landscape type: describes the land form where a minority habitat is found e.g. gorge.

layer: thematic data described and stored in a map format and organized by subject matter, e.g. soils and roads which extend over the defined geographic area.


mature: reproductive trees where growth has begun to significantly slow down & whose DBH is greater than the “maturity threshold” for the species.

metadata: data which describes and documents the survey and its attributes; how, when, where, and by whom the data was collected; availability and distribution of information as well as the projection, scale, resolution, and accuracy.

minority: a “0% woodland component” exists where a small unmappable (<0.5ha) NVC woodland community/HAP type occurs within a larger mappable polygon that is a different NVC/HAP type. A minority NVC/HAP can occur as a single small “patch” (<0.5ha), or multiple small patches which are each <0.5ha but which together may cover an area ≥0.5ha. To qualify as a minority each discrete unmappable NVC/HAP type CANNOT occupy 3% or more of the larger mappable “surveyed” polygon within which it occurs.

mosaic: an intimate mix of NVC/ woodland communities where the different communities cannot easily be separated from each other as mappable unit ≥0.5ha. Mosaics of woodland habitats occur regularly in the NWSS data.


native species: broadly defined as those native to Scotland and to the region.

native woodland: woods where the canopy cover is composed mainly of native species (ie over 50% ).

nearly native woodland: where native species make up between 40% and 50% of the canopy. These are woods that could have potential to be converted into native woodlands by altering their species mix.

NFI: the National Forest Inventory. An ongoing project to determine the extent, location, composition and condition of all woodland across GB which will replace the current National Inventory of Woodland and Trees (NIWT)(2000). The NFI will collect, maintain and analyse a standard set of core data on all forests so that comparable information exists across Scotland, England and Wales, and ownerships (FC or private).

NVC: the National Vegetation Classification. The standard classification used for describing vegetation in GB (Rodwell 1991).

NWSS: the Native Woodland Survey of Scotland. A survey of all native woodlands, nearly native woodlands and non native plantations on ancient woodland sites in Scotland. A woodland map links to spatial data showing the type, extent and attributes of these woods.


open land: polygons with <20% canopy cover of trees and shrubs adjoining a native woodland.

other_traits: additional attributes such as invasive species or browsing by animals that are not found in all woodlands but are noted when found and may be relevant to the condition or management needs of the woodland. [for browser/GIS]


PAWS: Plantations on Ancient Woodland Sites. These are surveyed in the NWSS where they are recorded in the Scottish ancient woodland inventory (SAWI). These woodlands appear to have originated through natural regeneration sometime before the mid-19th century, but were later converted to planted woods.

pinewood zone: an area in Scotland where Scots pine (Pinus sylvestris) is believed to be a native species. The zone used in the NWSS is based on the work by McVean and Ratcliffe (McVean, D.N. and Ratcliffe, D.A. (1962). Plant Communities of the Scottish Highlands. HMSO, London) and Forest Research, though for the purposes of the NWSS a 1km buffer was added. In any polygon intersecting the pine zone Scots pine is recorded as native. Outside of this zone pine is regarded as not native.

pole immature: a structural stage or maturity class in the survey. Trees are at the thicket stage ( ≥7cm DBH & < the maturity threshold for the species) and usually above 5m height but not yet mature.

polygon: a multi-sided figure that represents a mapped area with specific attributes that describe it and differentiate it from adjoining areas, referred to as a “mappable unit” or “woodland unit”.

priority woodland type: a priority habitat type defined under the UK Biodiversity Action Plan e.g. Upland mixed ashwoods.


relate: an operation that establishes a temporary connection between corresponding records in map layers and tables using an index common to both. A relate gives access to additional feature attributes that are not stored in a single layer. [for browser/GIS]


SCDB: a sub compartment database. The FC’s SCDB is the record of information on the FC’s land holding that contains the attributes and spatial data for the woodlands on the National Forest Estate.

SCPTDATA_ID: a unique index for each NWSS polygon. [for browser/GIS]

semi-naturalness: in woodland this is indicated a structure containing a range of age and/or size classes of trees, a range of species with differing form and the appearance of being unevenly spaced or in dense clumps. Other evidence is trees with open ground habitats or other natural features or an absence of cultivation drainage. The woodlands usually have ill defined edges following natural lines rather than man-made features.

shrubs: woody plants often (but not always) branching abundantly from the base, >1m tall and usually <5m tall. (Depending on the species these are defined in one of the following two categories: (i) shrubs that are considered as part of the canopy and (ii) shrubs that do not count as part of the canopy cover estimate and are recorded as a proportion of the polygon. The latter category includes the invasive species of Japanese knotweed, rhododendron ponticum and snowberry.

stocking density: the number of stems per hectare given as a range e.g. <100 stems/ha or ≥100 and <600 stems/ha.

structure: a woodland can be composed of a variety of plants of differing sizes. Distinct layers can develop e.g. mature, pole immature, shrub or regeneration.


type: description of the NWSS polygon in relation to the main outcomes of the survey e.g. native, nearly-native, PAWS or open land.


veteran tree: a tree that meets both the minimum DBH threshold for its species and displays at least 3 of the growth & decay attributes specified in the survey protocol.

visible regeneration: trees above the predominant field layer height but <1m tall and still susceptible to browsing damage.


woodland: an area of trees and shrubs which has a canopy ≥20% cover.