Upland Mixed Ashwood BNG Units
High
Woodland and forest
Upland areas of northern and western England, particularly on base-rich soils
Trusted by Developers and Landowners
What is Upland Mixed Ashwood?
Upland mixed ashwoods are species-rich broadleaved woodlands found on base-rich soils in upland landscapes. They are typically dominated by ash, though locally oak, birch, wych elm, rowan, small-leaved lime or hazel may be prominent depending on site conditions.
These woodlands often develop on limestone and other calcareous substrates, including steep slopes, ravines, flushes and rocky outcrops. Many upland mixed ashwoods are ancient woodland, while others represent long-established secondary woodland that retains strong ecological continuity.
Why It Matters for BNG
Upland mixed ashwoods are a high distinctiveness priority woodland. Loss is subject to strict trading rules and normally requires like-for-like or higher replacement, making impacts difficult and costly to offset. Retention and buffering of existing ashwoods is often the most effective way to manage BNG risk on upland or limestone-influenced sites.
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Where You'll Find It
Upland mixed ashwoods occur across upland Britain and Northern Ireland, concentrated over limestone and calcareous substrates in areas such as the Derbyshire Dales, North Wales, the Pennines, and scattered northern limestone regions. They typically occupy ravines, valley sides, limestone pavements, and base-rich flushes, often in mosaic with calcareous grassland and rocky outcrops.
Soil & Site Requirements
Upland mixed ashwoods require base-rich or calcareous soils, typically over limestone, dolomite, or other alkaline bedrock. They can also develop on more acidic soils where base-rich water flushes through. Sites are often steep, rocky, or with shallow, well-drained soils, though some stands occur on damper ground with alder in wet flushes.
How a New Upland Mixed Ashwood is Created
Inputs
• Retain or establish base-rich soil conditions
• Use locally appropriate native broadleaved species
• Avoid fertiliser, soil improvement or conifer planting
• Protect establishing trees from grazing
Management
• Encourage natural regeneration through small canopy gaps
• Control grazing pressure from livestock and deer
• Retain standing and fallen deadwood
• Avoid intensive forestry operations
Landscape
• Focus creation or expansion adjacent to existing ashwoods
• Link woodland to calcareous grassland and scrub
• Maintain natural woodland edges and transitions
How Existing Upland Mixed Ashwoods Is Improved
Inputs
• Reduce grazing pressure to allow regeneration
• Under-plant with appropriate native species where needed
• Remove or thin non-native conifers and invasive species
Management
• Promote mixed age structure and layered canopy
• Retain veteran trees and deadwood
• Manage ash dieback adaptively without wholesale removal
Landscape
• Buffer woodland edges with scrub or grassland
• Improve connectivity between woodland blocks
• Expand woodland onto suitable adjacent base-rich land
Target Condition
Upland mixed ashwoods in their defined BNG condition should:
• Be dominated by native broadleaved species typical of ashwood
• Show mixed age and height structure
• Support active natural regeneration
• Contain standing and fallen deadwood
• Support characteristic ashwood ground flora
• Have low invasive non-native species cover
• Be managed with minimal damaging disturbance
The BNG Value of Upland Mixed Ashwood
• Distinctiveness: High
• Condition Potential: Moderate to high where grazing and regeneration are managed
• Restoration Pathway: Enhancement of existing woodland rather than new creation
• Strategic Value: Key habitat for upland woodland networks and limestone landscapes
Species Typical of Upland Mixed Ashwoods
Canopy or Primary Layer
• Ash (Fraxinus excelsior)
• Wych elm (Ulmus glabra)
• Small-leaved lime (Tilia cordata)
• Oak species (Quercus spp.)
• Birch (Betula spp.)
• Rowan (Sorbus aucuparia)
Shrub or Secondary Layer
• Hazel (Corylus avellana)
• Hawthorn
• Holly
• Guelder rose
• Yew in some stands
Ground Flora or Understorey
• Dog’s-mercury
• Ramsons
• Herb-Paris
• Wood crane’s-bill
• Solomon’s-seal
• Ferns, bryophytes and calcareous mosses
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Frequently Asked Questions
What is Upland Mixed Ashwood?
Upland Mixed Ashwood is a priority broadleaved woodland found on base-rich upland soils, often ancient and species rich.
How is BNG measured here?
By area, high distinctiveness and woodland condition score using the Statutory Biodiversity Metric.
How can I achieve BNG?
Primarily through enhancement of existing ashwoods by improving structure, regeneration and species composition.
What is the BNG target condition?
Moderate to Good condition, reflecting structurally diverse, regenerating woodland.
What management is required?
Grazing control, retention of deadwood, invasive species management and adaptive response to ash dieback.
Exploring Other Habitats?
Line of Trees
A Line of Trees in BNG is a row or corridor of trees forming a clear linear feature in the landscape. It is made up of individual trees spaced closely enough to create a recognisable boundary or route through farmland, estates or river corridors. These lines often follow historic field edges, green lanes or trackways and can include banks or ditches alongside them.
Some lines are simple boundary features, while others hold greater ecological value because they contain mature or veteran trees, standing deadwood, cavities and other natural features that support birds, bats and invertebrates.
Native Hedgerow
A Native Hedgerow BNG habitat is a linear woody habitat where more than 80% of the shrub and tree cover consists of native species. Structurally, native hedgerows consist of a dense shrub layer commonly dominated by species such as hawthorn, blackthorn and hazel, often with standard trees including oak or ash emerging above the canopy.
Ecologically Valuable Line of Trees
An Ecologically Valuable Line of Trees is a high-distinctiveness linear habitat consisting of a continuous or near-continuous arrangement of trees over 20 metres in length, typically less than 5 metres wide between major stems, and distinguished by structural features that support specialist wildlife. Unlike standard lines of trees, this habitat includes at least one tree with veteran characteristics or natural ecological niches such as cavities, standing or attached deadwood, ivy cover or loose bark.
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