Ben Averis report

Ben Averis report 2023

Ben Averis NVC report 2023 

Some vegetation types found in Scotland that are not mentioned in the UKHab v2 guidance:

Adding the Common names to thus section if the Avis Reort for Nature Scot.

NVC types

U15 Saxifraga aizoides–Alchemilla glabra banks

(Yellow Saxifrage – Smooth Lady’s-mantle banks)

Main or notable non-NVC vegetation or habitat types:

• Avenella flexuosa snowbed/montane grassland (Wavy Hair-grass snowbed/montane grassland)

• Pohlia ludwigii snowbed (Ludwig’s Thread-moss snowbed)

• Mixed bryophyte snowbed (Mixed moss snowbed)

• Herb-rich north-western form of U4 acid grassland (Fine-leaved Sheep’s-fescue – Common Bent grassland)

• Species-poor neutral grassland dominated by mixtures of Holcus species &/or Festuca rubra (Yorkshire-fog species and/or Red Fescue)

• Elytrigia repens grassland (Common Couch grassland)

• Vegetation dominated by Dryopteris / Athyrium ferns (Buckler-fern / Lady-fern dominated vegetation)

• Neutral small sedge mire (commonly mapped as MX)

• Juncus effusus acid grassland vegetation (Soft Rush acid grassland)

• Juncus acutiflorus acid grassland vegetation (Sharp-flowered Rush acid grassland)

• Herb-rich Juncus squarrosus flush (a form of U6) (Heath Rush flush)

• Equisetum palustre-dominated wetland (Marsh Horsetail-dominated wetland)

• Carex disticha-dominated wetland (Brown Sedge-dominated wetland)

• Ranunculus lingua swamp (Greater Spearwort swamp)

• Menyanthes trifoliata swamp/bog pool vegetation (Bogbean swamp/bog pool vegetation)

• Woodland with Luzula sylvatica-dominated ground layer (WLz) (Great Wood-rush woodland)

• Dry woodland with a species-poor Urtica dioica-dominated ground layer (Common Nettle-dominated ground layer)

• Sambucus nigra scrub (Elder scrub)

• Cytisus scoparius scrub (Broom scrub)

• Rubus idaeus underscrub (Raspberry underscrub)

• Damp non-montane Vaccinium – Sphagnum heath (Bilberry–Sphagnum heath)

• Calluna vulgaris heath with rich flora of mesotrophic herbs (Heather heath)

• Calcicolous Arctostaphylos uva-ursi heath (Bearberry heath)

• Wet heath with abundant dwarf Juniperus communis (Dwarf Juniper wet heath)

• Montane fell-fields

• Montane Racomitrium ericoides heath (Heath-like Racomitrium moss heath)

• Schoenus nigricans – Eupatorium coastal cliff community (Black Bog-rush – Hemp-agrimony coastal cliff community)

• Catabrosa aquatica coastal community (Whorl-grass coastal community)

• Polytrichum commune-dominated vegetation (Common Haircap moss-dominated vegetation)

• Ivy-dominated vegetation (e.g. on cliffs) (Hedera helix – Common Ivy)

• Rumex obtusifolius-dominated vegetation (Broad-leaved Dock-dominated vegetation)

• Petasites hybridus-dominated vegetation (Butterbur-dominated vegetation)

• Impatiens glandulifera-dominated vegetation - Non-Native and Invasive. (Himalayan Balsam-dominated vegetation) - Non-Native and Invasive

NVC Polygons

In the context of the National Vegetation Classification (NVC) system in Great Britain, a 

polygon represents a mapped, enclosed area of land that contains a relatively homogeneous, distinct vegetation community, or a mosaic of communities. These polygons are the fundamental spatial unit in NVC habitat maps, created to delineate specific plant communities based on field surveys, and are often stored in a Geographic Information System (GIS). 

Data.gov.uk +3

Key aspects of NVC polygons include:

• Definition & Purpose: A polygon defines a boundary around vegetation with enough uniformity to be distinguishable from its surroundings. It is used to map 286 different NVC communities and hundreds of sub-communities.

• Data Representation: A polygon can represent a single NVC community type (e.g., M23 Juncus effusus/acutiflorus rush pasture) or a "mosaic" or "transition" area where multiple communities are mixed together.

• Types of Polygons:

  • Single Habitat Code: Polygons with a single dominant habitat code.

  • Mosaic Polygons: Polygons containing multiple vegetation types, often with the highest conservation value component determining the overall value score.

• TheMap ping Standards: While NVC often involves detailed ground surveys, polygons represent the spatial, aerial extent of these communities.

• Management Use: These polygons are essential for nature conservation, allowing planners to identify areas of interest, such as Annex I habitats, or to monitor change over time. 

Non - NVC Codes

The passage is referring to the informal but widely used “non-NVC” mapping codes that surveyors apply where vegetation falls outside, between, or finer than formal NVC communities. These are not part of Rodwell’s published NVC volumes, but they are well established in professional practice.

Below is a clear, flat explanation of what those non-NVC codes are, and the main types in use, with examples — including several you’ve already used.

What “non-NVC codes” means in practice

They are pragmatic surveyor shorthand codes used when:

• Vegetation is semi-natural but omitted from NVC

• Vegetation is transitional / mosaic / sub-community scale

• Vegetation is structural rather than floristic

• Vegetation is too species-poor or too mixed for a named NVC type

They allow mapping to continue without forcing an inappropriate NVC label.

Main non-NVC code families in common use

1.  MX – Mixed or Mosaic vegetation

Used where no single NVC community can reasonably be assigned.

Examples:

• MX – Mixed vegetation

• MXg – Mixed grassland

• MXm – Mixed mire

• MXw – Mixed wetland

You explicitly mentioned:

• Neutral small sedge mire (commonly mapped as MX)

2.  Structural dominance codes (single-taxon dominance)

Used where vegetation is overwhelmingly dominated by one species or genus.

Common examples:

• Je – Juncus effusus vegetation

• Ja – Juncus acutiflorus vegetation

• Js – Juncus squarrosus vegetation

• Ee – Equisetum-dominated vegetation

• Cd – Carex disticha vegetation

These are exactly the kind of “non-NVC codes” the passage refers to.

3.  WLx / WLz – Woodland ground-layer codes

Used where the canopy is woodland but the ground flora does not fit an NVC W-community.

Examples:

• WLz – Luzula sylvatica-dominated woodland ground layer

• WLn – Nettle-dominated woodland ground layer

• WLf – Fern-dominated woodland ground layer

Again, WLz appears in your list.

4. Non-NVC scrub and underscrub codes

Scrub types that are too species-poor or linear for W-series NVC.

Examples:

• ScrE – Elder scrub

• ScrB – Broom scrub

• ScrR – Raspberry scrub

Often mapped simply as:

• Elder scrub (non-NVC)

• Broom scrub (non-NVC)

5.  Non-NVC wetland / swamp codes

Where vegetation is clearly swamp but doesn’t resolve to S-series.

Examples:

• Ranunculus lingua swamp (non-NVC)

• Menyanthes trifoliata swamp (non-NVC)

• Petasites hybridus swamp (non-NVC)

Surveyors often combine:

• Sw + dominant species
  rather than forcing S4, S27, etc.

6.  Montane and snowbed non-NVC codes

Many Scottish montane communities were deliberately excluded or under-resolved in NVC.

Common non-NVC usages:

• Avenella flexuosa snowbed

• Pohlia ludwigii snowbed

• Mixed bryophyte snowbed

• Racomitrium fell-field / heath

These are widely accepted as non-NVC montane types, despite being semi-natural and well understood.

7.  Invasive / novel vegetation (non-NVC)

Vegetation dominated by species absent when NVC was devised.

Examples:

• Impatiens glandulifera stands

• Fallopia japonica stands

• Rhododendron ponticum scrub

Mapped descriptively, often with a simple dominance code.

Why these codes matter (linking back to your passage)

The passage is making three key points:

1. NVC is the gold standard for British semi-natural vegetation

2. Gaps exist, but they are small and manageable

3. Those gaps are routinely handled using non-NVC codes that are now widely shared and understood

In other words:

👉 Non-NVC codes extend NVC — they don’t undermine it.