Report 307
Guidance on the interpretation of the Biodiversity Broad Habitat Classification (terrestrial and freshwater types): Definitions and the relationship with other classifications
(2000)
Jackson D.L.
This report contains the definitions for each of the terrestrial and freshwater types of the biodiversity Broad Habitat Classification
Summary
This report contains the definitions for each of the
terrestrial and freshwater types of the biodiversity Broad Habitat
Classification. The definitions given are based upon the
descriptions agreed by the UK Biodiversity Group and published in
volume two of the second tranche of action plans (UK Biodiversity
Group 1998b). In addition to the definitions, annex 1 of this
report contains tables which show the correspondence between these
broad habitat types and a number of other standard habitat
classifications and select lists of habitats of conservation
interest commonly used in the UK for collecting and reporting
data.
The information presented in this report will form the basis
of a manual of interpretation for the Broad Habitat Classification
which will be published by the Joint Nature Conservation Committee
at a later date. In addition to the definitions and correspondence
tables, the full manual will contain detailed descriptions
including information on the structure, characteristic species,
distribution and extent of each broad habitat type.
You will need the free Adobe Acrobat Reader to view this
document.
Acknowledgements
Many people have assisted during the review of the
biodiversity Broad Habitat Classification. In particular the
following people have assisted in drafting the definitions of the
terrestrial and freshwater broad habitat types: Colin Barr (Centre
for Ecology and Hydrology), Tim Blackstock (CCW), David Stevens
(CCW), Jeanette Hall (EN), Richard Jefferson (EN), Keith Kirby
(EN), David Horsfield (SNH) and Des Thompson (SNH). In addition the
following people have supplied detailed comments on the definitions
and the relationships with other habitat classifications: Helen
Armstrong (SNH), Phil Boon (SNH), Bob Bunce (CEH), Bill Butcher
(Somerset Environmental Records Centre), Andrew Coupar (SNH),
Catherine Duigan (CCW), Tristan Hatton-Ellis (CCW), Liz Howe (CCW),
David Howell (SNH), Jeff Kirby (on behalf of the Department of the
Environment, Transport and the Regions), Jim Latham (CCW), Angus
MacDonald (SNH), Roger Meade (EN), Carrie Rimes (CCW), Ian Strachan
(JNCC) and Marcus Yeo (JNCC).
1Introduction
1.1 This report
This report contains the definitions for each of the
terrestrial and freshwater types of the biodiversity Broad Habitat
Classification. The definitions given are based upon the
descriptions agreed by the UK Biodiversity Group and published in
volume two of the second tranche of action plans (UK Biodiversity
Group 1998b). In addition to the definitions, annex 1 of this
report contains tables which show the correspondence between these
broad habitat types and a number of other standard habitat
classifications and select lists of habitats of conservation
interest commonly used in the UK for collecting and reporting
data.
The information presented in this report will form the basis
of a manual of interpretation for the Broad Habitat Classification
which will be published by the Joint Nature Conservation Committee
at a later date. In addition to the definitions and correspondence
tables, the full manual will contain detailed descriptions
including information on the structure, characteristic species,
distribution and extent of each broad habitat type.
1.2
Biodiversity Action Plan
The Convention on Biological Diversity was one of the major
initiatives arising from the Earth Summit held in Rio de Janeiro in
1992. The Convention, which has been signed by 150 countries
including the United Kingdom, and European Union, requires each
contracting party:
"...to develop national strategies, plans or programmes
for the conservation and sustainable use of biological diversity,
or adapt for this purpose existing strategies, plans or programmes
which shall reflect, inter alia, the measures set out in this
Convention relevant to the Contracting Party concerned".
The UK Government response to the Convention was set out in
Biodiversity: The UK Action Plan published in January 1994
which sets out the overall goal for biodiversity as:
"To conserve and enhance biological diversity within the
UK and to contribute to the conservation of global biodiversity
through all appropriate mechanisms".
One of the main outcomes of the UK Action Plan was the setting
up of the UK Biodiversity Steering Group (now called the UK
Biodiversity Group), who were given the task of preparing a
detailed programme of action to achieve this objective. This group
has co-ordinated the preparation of action plans for our most
threatened species and wildlife habitats. Costed action plans which
have set quantifiable targets have been produced for 391 species
and 45 habitats of highest priority for conservation. These plans
have been published in Biodiversity: The UK Steering Group
report in 1995 (UK Steering Group, 1995) and five volumes of
UK Biodiversity group: Tranche two action plans during
1998 and 1999 (UK Biodiversity Group 1998; 1998b; 1999b;
1999c).
In addition to identifying a suite of 'priority' habitats and
species requiring action it was also considered important to
understand how these are set within the context of the whole land
surface and surrounding sea of the UK. A classification of broad
habitat types has therefore been
developed.
1.3 Biodiversity Broad
Habitat Classification
A framework classification for 37 habitat types across the
whole of the UK was published in the UK steering group report (UK
Steering Group 1995). A brief habitat statement was also published
for each of these to inform national and local policy and action.
Whilst this provided useful contextual information for the initial
action planning process, there were gaps in the classification and
the Biodiversity Steering Group recommended that these and some of
the ambiguity in the habitat descriptions should be
revisited.
The terrestrial and freshwater elements of the classification
were therefore re-examined in 1997 by a cross-sectoral group led by
the JNCC. The findings of this group were published in the second
volume of tranche two action plans along with brief descriptions of
each type (UK Biodiversity Group 1998b). Changes to the marine and
coastal habitat types were reviewed separately by the Marine
Targets Sub-Group and the revised classification and habitat
statements for the coastal and marine types have been published in
the fifth volume of tranche two action plans along with the costed
action plans UK Biodiversity Group 1999c).
In addition to providing the framework for the biodiversity
action plan process, the revised Broad Habitat Classification will
also be used for UK reporting on the condition of protected sites.
The Broad Habitat Classification is also the framework through
which the Government is committed to meet its obligations for
monitoring in the wider countryside. The Countryside Survey 2000
undertaken by the Department of the Environment, Transport and the
Regions (DETR) and the Natural Environment Research Council (NERC)
will provide information on the extent and quality of some of the
more widespread broad habitat types.
1.4 The review of the
terrestrial and freshwater broad habitat types
In reviewing the terrestrial and
freshwater broad habitat types the group gave due regard to the
original basis for the selection of broad habitats types, namely
that (i) there should be a limited number of habitat types and
(ii) the definitions should be simple and easily understood by
a broad range of people. In addition the working group concluded
that the biodiversity Broad Habitat Classification should aim to be
provide:
- a comprehensive framework for surveillance of the UK
countryside and surrounding seas which is compatible with other
widely-used habitat and land-cover classifications, particularly
Phase 1 and the Countryside Survey 2000:
- a means of setting priority habitats in context and a system
for identifying gaps and emerging new priorities in the list of
priority habitats; and
- a means of characterising patterns and mosaics upon which
wide-ranging species are dependent.
The working group used the
following six criteria to re-examine the biodiversity Broad Habitat
Classification:
- Comprehensive - All of the habitat types of the UK should be
described within the classification.
- Exclusive - The habitat types should be discrete to ensure that
there is a "once-only fit" in the classification for each habitat
encountered in the field.
- Structured - The classification should provide a framework for
organising and presenting the priority habitats that are the focus
of action plans.
- Nested - Priority habitats should fit into only one broad
habitat type.
- Measurable - Broad habitats should be easily recognisable, have
a measurable surface area and physical or biological features that
are clearly characterised and wherever possible can be selected
from existing systems for data collection.
- Consistent - There should be consistency in the division of the
broad habitats. The classification should not sub-divide some
ecological units more finely that others.
The changes made to the
terrestrial and freshwater elements of the biodiversity Broad
Habitat Classification are presented in Box 1 below.
Box 1: Revisions to the
terrestrial and freshwater elements of the Broad Habitat
Classification
| *Original broad habitat
type |
Change made |
New broad habitat type |
| 1 Broadleaved and yew |
redefined to include mixed woodland |
1 Broadleaved, mixed and yew woodland |
| 2 Planted coniferous woodland |
redefined to include native and semi-natural coniferous
woodland |
2 Coniferous woodland |
| 3 Native pine woodland |
now only recognised as a Priority habitat
type |
|
| 4 Lowland wood pastures and
parkland |
now only recognised as a Priority habitat
type |
|
| 5 Boundary features |
redefined to include linear features |
3 Boundary and linear features |
| 6 Arable |
redefined to include horticulture and woody
crops |
4 Arable and horticulture |
| 7 Improved grassland |
unchanged |
5 Improved grassland |
| 8 Unimproved neutral grassland |
redefined to include semi-improved neutral
grassland |
6 Neutral grassland |
| 10 Calcareous grassland |
unchanged |
7 Calcareous grassland |
| 9 Acid grassland |
unchanged |
8 Acid grassland |
| |
added |
9 Bracken |
| 11 Lowland heathland |
redefined to include upland heathland |
10 Dwarf shrub heath |
| 12 Grazing marsh |
Priority habitat |
|
| 13 Fens, carr, marsh, swamp and
reedbed |
redefined to remove carr and include
flushes |
11 Fen, marsh and swamp |
| 14 Lowland raised bog |
redefined to include blanket bogs |
12 Bogs |
| 15 Standing open water |
redefined to include canals |
13 Standing open water and canals |
| 16 Rivers and streams |
unchanged |
14 Rivers and streams |
| 17 Canals |
deleted and incorporated into standing open
water |
|
| 18 Montane |
restricted to only habitats which occur exclusively in
the montane zone |
15 Montane habitats |
| 19 Upland heathland |
deleted and incorporated into Dwarf shrub
heath |
|
| 20 Blanket bog |
deleted and incorporated into Bogs |
|
| 36 Limestone pavements |
now only recognised as a Priority habitat
type |
|
| |
added |
16 Inland rock |
| 37 Urban |
redefined to include all built-up areas |
17 Built-up areas and gardens |
The numbers for the broad habitat
types listed in column 1 are taken from the original
biodiversity Broad Habitat Classification published in
Biodiversity: the UK Steering Group Report (UK
Biodiversity Steering Group 1995).
2 Definitions of the
terrestrial and freshwater biodiversity broad habitat
types
The following definitions are based upon the descriptions of
the revised broad habitat types agreed by the UK Biodiversity
Group.
2.1 Broadleaved, mixed and
yew woodland
This broad habitat type is characterised by vegetation
dominated by trees that are more than 5 m high when mature,
which form a distinct, although sometimes open canopy with a canopy
cover of greater than 20%. It includes stands of both native and
non-native broadleaved tree species and yew Taxus baccata,
where the percentage cover of these trees in the stand exceeds 20%
of the total cover of the trees present. Woodlands that are
dominated by conifer trees with less than 20% of the total cover
provided by broadleaved or yew trees are included in the
'Coniferous woodland' broad habitat type. Stands of
broadleaved, mixed and yew woodland may be either ancient or recent
woodland and either semi-natural arising from natural regeneration
of trees, or planted. Recently felled broadleaved, mixed and yew
woodland is also included in this broad habitat type where there is
a clear indication that it will return to woodland. Otherwise it is
classified according to the field layer composition.
Scrub vegetation, where the woody component tends to be mainly
shrubs usually less than 5 m high, and carr (woody vegetation
on fens and bog margins) is included in this broad habitat type if
the woody species form a canopy cover of greater than 30% and the
patch size of scrub is greater than 0.25ha. Exceptions to this
include dwarf gorse Ulex minor and western gorse Ulex
gallii which are included in the 'Dwarf shrub heath'
broad habitat type, montane willow scrub which is included in the
'Montane habitats' broad habitat type, and scrub on sand
dunes and shingle which is included in 'Supralittoral
sediment' broad habitat type. Stands of bog-myrtle Myrica
gale are included in this broad habitat type as scrub if they
are more than 1.5 m tall. This habitat type does not include
hedges (woody vegetation that has been managed as a linear feature)
as these are included in the 'Boundary and linear
features' broad habitat type.
2.2 Coniferous
woodland
This broad habitat type is characterised by vegetation
dominated by trees that are more than 5 m high when mature,
which form a distinct, although sometimes open canopy which has a
cover of greater than 20%1. It includes stands of both
native and non-native coniferous trees species (with the exception
of yew Taxus baccata) where the percentage cover of these
trees in the stand exceeds 80% of the total cover of the trees
present2. Woodlands that are made up of broadleaved, yew
and conifer trees with less than 80% of the total cover provided by
conifer trees are included in the 'Broadleaved, mixed and yew
woodland' broad habitat type. Recently felled coniferous
woodland is included in this broad habitat type where there is a
clear indication that it will return to woodland. Otherwise it is
classified according to the field layer composition.
Scots pine Pinus sylvestris is the only pine tree
that is native to the UK, and forms native woodland only in
Scotland. Semi-natural woods of Scots pine are normally called
native pinewoods. The majority of coniferous woodlands in the UK
are plantations of species that are either not native to the UK or
to the sites on which they occur.
2.3 Boundary and linear
features
This broad habitat type covers a diverse range of linearly
arranged landscape features such as hedgerows, lines of trees
(whether constituting part of a hedgerow or not), walls, stone and
earth banks, grass strips and dry ditches. These features may occur
separately or in combinations forming multi-element boundaries.
This habitat type also includes some of the built components of the
rural landscape including roads, tracks and railways and their
associated narrow verges of semi-natural habitat.
This habitat type does not include roads, tracks and railways
in urban areas as these are included in the 'Built-up areas and
gardens' broad habitat type. It also does not include canals
and ditches that are water-filled for the majority of the year,
which are included in the 'Standing open water and canals'
broad habitat type, rivers and streams which are in the 'Rivers
and streams' broad habitat type, and linear features in
woodland such as rides and fire breaks which are included in either
the 'Broadleaved, mixed and yew woodland' or
'Coniferous woodland' broad habitat types. Cereal field
margins managed for nature conservation are included in the
'Arable and horticultural' broad habitat type.
2.4 Arable and
horticultural
This broad habitat type covers arable cropland (including
perennial, woody crops, and intensively managed, commercial
orchards), commercial horticultural land (such as nurseries,
commercial vegetable plots and commercial flower growing areas),
freshly-ploughed land, annual leys, rotational set-aside and
fallow. This habitat type includes cereal field margins but not
field boundaries as these are included in the 'Boundary and
linear features' broad habitat type. This habitat type also
does not include domestic gardens and allotments as these are
included in the 'Built-up areas and gardens' broad habitat
type.
2.5 Improved
grassland
This broad habitat type is
characterised by vegetation dominated by a few fast-growing grasses
on fertile, neutral soils. It is frequently characterised by an
abundance of rye-grass Lolium spp. and white clover
Trifolium repens. Improved grasslands are typically either
managed as pasture or mown regularly for silage production or in
non-agricultural contexts for recreation and amenity purposes; they
are often periodically resown and are maintained by fertiliser
treatment and weed control. They may also be temporary and sown as
part of the rotation of arable crops but they are only included in
this broad habitat type if they are more than one year old. Sown
grasslands which are less than one year old are included in the
'Arable and horticultural' broad habitat type.
2.6 Neutral grassland
This broad habitat type is characterised by vegetation
dominated by grasses and herbs on a range of neutral soils usually
with a pH of between 4.5 and 6.5. It includes enclosed dry hay
meadows and pastures, together with a range of grasslands which are
periodically inundated with water or permanently moist.
Neutral grasslands are sometimes referred to as mesotrophic
grasslands. The plant species assemblages that develop on neutral
soils are different from those that develop on acid soils (acid or
calcifugous grassland) and calcareous soils (calcareous or
calcicolous grassland). For the most part neutral grassland
communities have few diagnostic indicator species but lack strong
calcicoles or calcifuges characteristic of base-rich and acid soils
respectively. The National Vegetation Classification describes 12
types of unimproved and semi-improved neutral grassland (Rodwell
1992).
These types are listed in Box 2
below.
Box 2: NVC types included in the 'Neutral
grassland' broad habitat type
|
| MG1 |
Arrhenatherum elatius grassland |
| MG2 |
Arrhenatherum elatius-Filipendula ulmaria tall-herb
grassland |
| MG3 |
Anthoxanthum odoratum-Geranium sylvaticum
grassland |
| MG4 |
Alopecurus pratensis-Sanguisorba officinalis
grassland |
| MG5 |
Cynosurus cristatus-Centaurea nigra grassland |
| MG6 |
Lolium perenne-Cynosurus cristatus grassland (part
only) |
| MG8 |
Cynosurus cristatus-Caltha palustris grassland |
| MG9 |
Holcus lanatus-Deschampsia cespitosa grassland |
| MG10 |
Holcus lanatus-Juncus effusus rush pasture |
| MG11 |
Festuca rubra-Agrostis stolonifera-Potentilla anserina
grassland |
| MG12 |
Festuca arundinacea grassland |
| MG13 |
Agrostis stolonifera-Alopecurus geniculatus
grassland |
Unimproved or species-rich neutral grasslands are usually
managed traditionally as hay-meadows and pastures. Semi-improved
neutral grasslands are also included in this broad habitat type and
these grasslands are usually managed for pasture or for silage or
hay. Neutral grassland differs from improved grasslands by having a
less lush sward, a greater range and higher cover of herbs, and
usually less than 25% cover of perennial rye-grass Lolium
perenne.
2.7 Calcareous grassland
This broad habitat type is characterised by vegetation
dominated by grasses and herbs on shallow, well-drained soils which
are rich in bases (principally calcium carbonate) formed by the
weathering of chalk and other types of limestone or base-rich rock.
Although the base status of such soils is usually high, with a pH
of above 6, it may also be more moderate and calcareous grassland
communities can occur on soils with a pH as low as 5.
Calcareous grasslands are also called calcicolous grasslands
and are sometimes referred to as chalk or limestone grasslands. The
plant species assemblages that develop on calcareous soils are
different from those that occur on neutral soils (neutral or
mesotrophic grassland) and acid soils (acid or calcifugous
grassland), and characteristically include a range of strict
calcicoles. The National Vegetation Classification describes 14
types of calcareous grassland (Rodwell 1992). These types are
listed in Box 3 below.
Box 3: NVC types included in the
'Calcareous grassland' broad habitat type
|
| CG1 |
Festuca ovina-Carlina vulgaris grassland |
| CG2 |
Festuca ovina-Avenula pratensis grassland |
| CG3 |
Bromus erectus grassland |
| CG4 |
Brachypodium pinnatum grassland |
| CG5 |
Bromus erectus-Brachypodium pinnatum grassland |
| CG6 |
Avenula pubescens grassland |
| CG7 |
Festuca ovina-Hieracium pilosella-Thymus
praecox/pulegioides grassland |
| CG8 |
Sesleria albicans-Scabiosa columbaria grassland |
| CG9 |
Sesleria albicans-Galium sterneri grassland |
| CG10 |
Festuca ovina-Agrostis capillaris-Thymus praecox
grassland |
| CG11 |
Festuca ovina-Agrostis capillaris-Alchemilla alpina
grass-heath |
| CG12 |
Festuca ovina-Alchemilla alpina-Silene acaulis
dwarf-herb community |
| CG13 |
Dryas octopetala-Carex flacca heath |
| CG14 |
Dryas octopetala-Silene acaulis ledge community |
2.8 Acid grassland
This broad habitat type is characterised by vegetation
dominated by grasses and herbs on a range of lime-deficient soils
which have been derived from acidic bedrock or from superficial
deposits such as sands and gravels. Such soils usually have a low
base status, with a pH of less than 5.5. This habitat type includes
a range of types from open communities of very dry sandy soils in
the lowlands, which may contain many annual species, through closed
pastures on red brown earths, to damp acidic grasslands typically
found on gleys and shallow peats.
Acid grasslands are also referred to as calcifugous swards.
The plant species assemblages that develop on acid soils are
different from those that develop on neutral soils (neutral or
mesotrophic grassland) and calcareous soils (calcareous or
calcicolous grassland) and are characterised by the presence of a
combination of calcifuge species. The National Vegetation
Classification describes six types of acid grassland (Rodwell
1992). These types are listed in Box 4 below. This habitat
type also includes inland sand dune communities (Rodwell 2000).
Acid grassland types and snow-bed communities which occur
exclusively in the montane (Alpine) zone are included in the
'Montane habitats' broad habitat type and acid grassland
types found on shingle habitats are included in the
'Supralittoral sediment' broad habitat type.
Box 4 NVC types included in the 'Acid
grassland' broad habitat type
|
| U1 |
Festuca ovina-Agrostis capillaris-Rumex acetosella
grassland |
| U2 |
Deschampsia flexuosa grassland |
| U3 |
Agrostis curtisii grassland |
| U4 |
Festuca ovina-Agrostis capillaris-Galium saxatile
grassland |
| U5 |
Nardus stricta-Galium saxatile grassland |
| U6 |
Juncus squarrosus-Festuca ovina grassland |
| SD10 |
Carex arenaria dune (inland sub-communities only) |
| SD11 |
Carex arenaria-Cornicularia aculeata dune (inland
sub-communities only) |
2.9 Bracken
This broad
habitat type covers areas dominated by a continuous canopy cover of
bracken Pteridium aquilinum at the height of the growing season. It
does not include areas with scattered patches of bracken or areas
of bracken which are less than 0.25 ha which are included in the
broad habitat type with which they are associated. It also does not
include areas of bracken under forest or woodland canopy which are
included in either the 'Broadleaved, mixed and yew woodland' or the
'Coniferous woodland' broad habitat types.
2.10 Dwarf shrub
heath
This broad habitat type is characterised by vegetation that
has a greater than 25% cover of plant species from the heath family
(ericoids) or dwarf gorse Ulex minor. It generally occurs
on well-drained, nutrient-poor, acid soils. Heaths do occur on more
basic soils but these are more limited in extent and can be
recognised by the presence of herbs characteristic of calcareous
grassland. Dwarf shrub heath includes both dry and wet heath types
and occurs in the lowlands and the uplands.
This habitat type does not include dwarf shrub dominated
vegetation in which species characteristic of peat-forming
vegetation such as cotton-grass Eriophorum spp. and
peat-building sphagna are abundant, or that occurs on deep peat
(greater than 0.5 m) as these are included in the
'Bog' broad habitat type. It also does not include heath
types which are exclusively alpine in distribution as these are
included in the 'Montane habitats' broad habitat type.
Heath types on sand dunes or shingle are included in the
'Supralittoral sediment' broad habitat type and heath
types on maritime cliffs and slopes that are influenced by salt
spray are included in the "Supralittoral rock" broad
habitat type.
2.11 Fen, marsh and swamp
This broad habitat type is characterised by a variety of
vegetation types that are found on minerotrophic (groundwater-fed),
permanently, seasonally or periodically waterlogged peat, peaty
soils, or mineral soils. Fens are peatlands which receive water and
nutrients from groundwater and surface run-off, as well as from
rainfall. Flushes are associated with lateral water movement, and
springs with localised upwelling of water. Marsh is a general term
usually used to imply waterlogged soil; it is used more
specifically here to refer to fen meadows and rush-pasture
communities on mineral soils and shallow peats. Swamps are
characterised by tall emergent vegetation. Reedbeds (i.e. swamps
dominated by stands of common reed Phragmites australis)
are also included in this type.
This habitat type does not include neutral and improved
grasslands on floodplains and grazing marshes which are included in
the 'Neutral grassland' and 'Improved grassland'
broad habitat types respectively, nor ombrotrophic mires (blanket,
raised and intermediate bogs) as these are included in the
'Bogs' broad habitat type. It also does not include areas
of carr (fen woodland dominated by species such as willow
Salix spp., alder Alnus glutinosa or birch
Betula spp.) as these are covered in the 'Broadleaved,
mixed and yew woodland' broad habitat type unless cover is
less than 30%.
2.12 Bog
This broad habitat type covers wetlands that support
vegetation that is usually peat-forming and which receive mineral
nutrients principally from precipitation rather than ground water.
This is referred to as ombrotrophic (rain-fed) mire. Two major bog
types are identified, namely raised bog and blanket bog. These two
types are for the most part fairly distinctive but they are
extremes of what can be considered an ecological continuum and
intermediate (or mixed) types occur.
The vegetation of bogs which have not been modified by surface
drying and aeration or heavy grazing is dominated by acidophilous
species such as bog-mosses Sphagnum spp., cotton-grass
Eriophorum spp. and cross-leaved heath Erica
tetralix. The water-table on these types of bogs is usually at
or just below the surface.
This habitat type also includes modified bog vegetation that
essentially resembles wet or dry dwarf shrub heath but occurs on
deep acid peat which would have once supported peat-forming
vegetation. Modified bog also includes impoverished vegetation
dominated by purple moor-grass Molinia caerulea or
hare's-tail cotton-grass Eriophorum vaginatum. Although
there is no agreed minimum depth of peat that can support
ombrotrophic vegetation, unmodified bog can be identified
floristically by the presence of characteristic species such as
cotton-grass Eriophorum spp. and peat-forming sphagna.
Peat depth, although somewhat arbitrary, is used as the primary
criterion to separate types of modified bog vegetation from the
'Dwarf shrub heath' broad habitat type and certain types
of 'Fen, marsh and swamp' broad habitat type. Therefore
vegetation dominated by dwarf-shrubs, cotton-grass
Eriophorum spp., or purple moor-grass Molinia
caerulea vegetation on peat greater than 0.5 m deep is
classified as bog for the purposes of the Broad Habitat
Classification.
In lowland areas with predominantly acid substrata there are
examples of valley and basin mires that receive acid surface
seepage, which gives rise to vegetation similar to that of bogs.
However, these types are covered in the 'Fen, marsh and
swamp' broad habitat type.
2.13 Standing water and canals
This broad habitat type includes natural systems such as
lakes, meres and pools, as well as man-made waters such as
reservoirs, canals, ponds and gravel pits. It includes the open
water zone (which may contain submerged, free-floating or
floating-leaved vegetation) and water fringe vegetation. Ditches
with open water for at least the majority of the year are also
included in this habitat type.
Standing waters are usually classified according to their
nutrient status and this can change naturally over time or as a
result of pollution. There are three main types of standing waters,
namely: oligotrophic (nutrient-poor), eutrophic (nutrient-rich),
and mesotrophic (intermediate). These lake types exist along an
environmental gradient and intermediate types occur. Other types of
standing water include dystrophic (highly acidic, peat-stained
water), marl lakes, brackish-water lakes, turloughs and other
temporary water bodies. Coastal saline lagoons are not included in
this habitat type but are covered by the 'Inshore sublittoral
sediment' broad habitat type.
The transition between open water and land is often occupied
by tall emergent vegetation called swamp or reedbed, or wet
woodland called carr. In practice this vegetation often forms a
continuum but for the purposes of the Broad Habitat Classification
marginal emergent vegetation that is greater than 5 m wide, or
areas of wetland habitat adjacent to the waterbody that are greater
than 0.25 ha, are included in the 'Fen, marsh and
swamp' broad habitat type. Areas of wet woodland greater than
0.25ha are included in the 'Broadleaved, mixed and yew
woodland' broad habitat type unless the cover of the canopy is
less than 30%.
2.14 Rivers and streams
The '
Rivers and streams' broad
habitat type covers rivers and streams from bank top to bank top,
or where there are no distinctive banks or banks are never
overtopped, it includes the extent of the mean annual flood. This
includes the open channel (which may contain submerged,
free-floating or floating-leaved vegetation) water fringe
vegetation and exposed sediments and shingle banks. Adjacent
semi-natural wetland habitats such as unimproved floodplain
grasslands, marshy grassland, wet heath, fens, bogs, flushes,
swamps and wet woodland, although intimately linked with the river,
are covered in other broad habitat types.
2.15 Montane habitats
This broad habitat type includes a range
of vegetation types that occur exclusively in the montane zone such
as prostrate dwarf shrub heath, snow-bed communities, sedge and
rush heaths, and moss heaths. The distinction between the
sub-montane and montane zone is often blurred and the two usually
merge through a band of transitional vegetation. Exclusively
montane habitat types can be recognised by their floristic
composition and their physiognomy (prostrate vegetation).
Widespread arctic-alpine species such as stiff sedge Carex
bigelowii, crowberry Empetrum nigrum hermaphroditum, trailing
azalea Loiseleuria procumbens, dwarf willow Salix herbacea, and
alpine clubmoss Diphasium alpinum, in association with frequent to
abundant woolly fringe-moss Racomitrium lanuginosum or cladonia
lichens Cladonia spp., and other macro-lichens such as Cetraria
islandica, are useful indicators of montane
communities.
Calcareous grasslands including those dominated by mountain
avens Dryas octopetala, fens and springs, blanket bog and
rock habitats which also occur in the montane zone are not included
in this habitat type but in the 'Calcareous grassland',
'Fen, marsh and swamp', 'Bog', and 'Inland
rock' broad habitat types respectively. This type also does
not include dwarf shrub heaths and grasslands that straddle the
notional boundary of the former tree-line with little change in
floristics and physiognomy and these should be treated as
components of other broad habitat types.
2.16 Inland rock
This broad habitat type covers both natural and artificial
exposed rock surfaces which are greater than 0.25ha, such as inland
cliffs, caves, and screes and limestone pavements, as well as
various forms of excavations and waste tips such as quarries and
quarry waste.
A number of vegetation types associated with rock habitats are
also included in this broad habitat type. These are: chasmophytic
vegetation (plant communities that colonise the cracks and fissures
of rock faces); calaminarian grassland (a grassland type which is
found on soils which have levels of heavy metals, such as lead,
chromium and copper, that are toxic to most plant species); and
certain types of tall herb and fern vegetation, which as a result
of grazing pressure are much reduced in extent and confined to
areas inaccessible to grazing animals such as cliff faces and
ledges, and to a lesser extent, on lightly-grazed steep rocky
slopes and boulder fields.
2.17 Built-up areas and gardens
This broad habitat type covers urban and
rural settlements, farm buildings, caravan parks and other man-made
built structures such as industrial estates, retail parks, waste
and derelict ground, urban parkland and urban transport
infrastructure. It also includes domestic gardens and allotments.
This type does not include amenity grassland which should be
included in the 'Improved grassland' broad habitat
type.
3 Relationships with other
standard UK habitat classifications
Correspondence tables which show the relationship between the
broad habitat types and a number of standard habitat
classifications and select lists of habitats of conservation
interest commonly used in the UK are presented in Annex 1 of
this report. Correspondence tables have been produced for the
following classifications and select lists:
- Phase 1 habitat classification (JNCC 1993);
- Countryside Survey 1990 reporting categories (Barr et
al. 1993);
- Biodiversity Priority habitat types (UK Biodiversity Steering
Group 1995);
- EC Habitats Directive Annex I habitat types(Commission of
the European Communities 1997); and
- National Vegetation Classification plant communities (Rodwell
1991a,b; 1992; 1995; 2000).
Differences in the rationale behind the methodologies for the
different habitat classifications mean that most of these
classifications do not bear a consistent or simple relationship to
each other. They use a range of parameters for classification, so
that they are not strictly comparable. For example, the National
Vegetation Classification uses only floristics to define the
different community types, whereas classifications like the
Phase 1 habitat classification and the biodiversity broad
habitat types use a mixture of criteria including environmental
factors, species composition and vegetation physiognomy. Commentary
is provided where one-to-one relationships between the categories
in the different systems do not exist. However, it is not always
possible to provide explicit rules on how the categories should be
separated.
The correspondence tables presented in the annex also include
the coastal and marine broad habitat types.
4
References
Barr CJ, Bunce RGH, Clarke RT, Fuller RM, Furse MT, Gillespie
MK, Groom GB, Hallam CJ, Hornung MJ, Howard DC & Ness MJ 1993
Countryside survey 1990 Main report London, Department of
the Environment. (Countryside 1990 Series volume 2)
Commission of the European Communities 1997 Council Directive
97/62/EC of 27 October 1997 adapting to technical and scientific
progress Directive 92/43/EEC on the conservation of natural
habitats and of wild fauna and flora. Official Journal of the
European Communities, No. L305/42
Horsfield, DA & Thompson, D 1996 The uplands: guidance on
terminology regarding altitudinal zonation and related terms.
Battleby, Scottish Natural Heritage (Information and Advisory Note,
No. 26)
Joint Nature Conservation Committee 1993 Handbook for
Phase 1 habitat survey: a technique for environmental
audit. Peterborough, Joint Nature Conservation Committee
Rodwell JS ed 1991a British plant communities,
volume 1: woodlands and scrub. Cambridge, Cambridge
University Press
Rodwell JS ed 1991b British plant communities,
volume 2: mires and heaths. Cambridge, Cambridge
University Press
Rodwell JS ed 1992 British plant communities,
volume 3: grassland and montane vegetation. Cambridge,
Cambridge University Press
Rodwell JS ed 1995 British plant communities,
volume 4: aquatic communities, swamp and tall herb fens.
Cambridge, Cambridge University Press
Rodwell JS ed 2000 British plant communities,
volume 5: maritime communities and vegetation of open
habitats. Cambridge, Cambridge University Press
UK Biodiversity Steering Group 1995 Biodiversity: The UK
Steering Group Report. Volume 1: Meeting the Rio
challenge. London, HMSO
UK Biodiversity Group 1998a Tranche two action plans.
Volume I: Invertebrates and vascular plants. Peterborough,
published by English Nature on behalf of the UK Biodiversity
Group
UK Biodiversity Group 1998b Tranche two action plans.
Volume II: Terrestrial and freshwater habitats.
Peterborough, published by English Nature on behalf of the UK
Biodiversity Group
UK Biodiversity Group 1999a Tranche two action plans.
Volume III: Plants and fungi. Peterborough, published by
English Nature on behalf of the UK Biodiversity Group
UK Biodiversity Group 1999b Tranche two action plans.
Volume VI: Terrestrial and freshwater species and
habitats. Peterborough, published by English Nature on behalf
of the UK Biodiversity Group
UK Biodiversity Group 1999c Tranche two action plans:
Volume V Maritime species and habitats. Peterborough,
published by English Nature on behalf of the UK Biodiversity
Group
73 pages
ISSN 0963 8091
Please cite as: Jackson D.L., (2000), Guidance on the interpretation of the Biodiversity Broad Habitat Classification (terrestrial and freshwater types): Definitions and the relationship with other classifications, JNCC Report 307, 73 pages, ISSN 0963 8091