Freshwater classifications
Introduction
Aquatic plant communities are important ecological components of
rivers and lakes. They play a complex role in the structure and
functioning of these habitats. For example, they provide food and
cover for fish and aquatic invertebrates, help oxygenate the water,
and limit erosion.
The statutory nature conservation agencies in
England, Scotland and Wales have a long history of carrying out
routine aquatic plant surveys of rivers and lakes. This
involves identifying and estimating the abundance of emergent,
submerged, floating-leaved, and free-floating aquatic
plants that grow in or near the water.
The primary aim of this survey effort is to
describe the botanical resource of rivers and lakes across Britain,
help in site assessment, management and the selection of key
sites, and help improve ecological understanding. This information
has underpinned the selection of a representative range of river
and lake types as features for protection as Sites of Special Scientific Interest
(SSSIs). The process of selecting such sites requires
comparison to set individual sites in a local and national context,
as provided for by the JNCC classification schemes for rivers and
lakes.
This work has led to the accumulation of two
large datasets held by the JNCC and two JNCC publications, which
classify river and lake vegetation communities according to the
composition of their aquatic plants:
Holmes,
N.T.H., Boon, P.J. & Rowell, T.A. 1999.
Vegetation Communities of
British Rivers: a revised classification.
Peterborough, Joint Nature Conservation
Committee.
Duigan, C., Kovach, W. & Palmer, M.
2006.
Vegetation Communities of
British Lakes: a revised classification.
Peterborough, Joint Nature Conservation
Committee.
The British Rivers Vegetation Communities
Classification
Introduction
The Vegetation Communities of
British Rivers: a revised classification is
based upon the composition of aquatic plant communities in
rivers. It comprises three different levels of classification
(see below). Each of these is described in the publication and
accompanied by a distribution map and details of the physical
features and aquatic plants. A key to classify newly surveyed sites is
included.
Brief history
The first comprehensive classification scheme for British rivers
(Holmes 1983) was based on aquatic plant surveys from 1,055
sites throughout England, Scotland and Wales. These were
carried out between 1978 and 1982 by the Nature Conservancy
Council. The revised classification (Holmes et al. 1999)
improved on and expanded the original version with the addition of
459 new surveys and the use of TWINSPAN (Two-Way Indicator Species
Analysis). In addition to classifying the sites, the TWINSPAN
outputs were used to show relationships between the river groups,
community types and sub-types that were identified (see below), as
well as the environmental variables related to these.
River Groups, Community Types and
Sub-Types
The rivers classification includes three hierarchical
levels:
- River Groups. This highest level consists of
four distinct broad groups (A-D) representing an environmental
gradient from lowland eutrophic rivers, to those that are
essentially upland, torrential and oligotrophic.
- River Community Types. This second tier of
division comprises ten River Community Types (RCTs) (I-X).
- Sub-types. This final sub-division
includes 38 river sub-types (AIa-DXe).
The following list provides a summary description and shows how
the River Groups and Community Types relate to each other:
Group
A Lowland rivers with shallow
gradients and rich geology
Type
I Lowland,
low-gradient rivers
Type
II Lowland,
clay-dominated rivers
Type
III Chalk rivers and
other base-rich rivers with stable flows
Type
IV Impoverished lowland
rivers
Group
B Meso-eutrophic rivers flowing
predominantly over sandstone and hard limestone
Type
V Sandstone,
mudstone and hard limestone rivers of England and Wales
Type
VI Sandstone, mudstone
and hard limestone rivers of Scotland and northern England
Group
C Mesotrophic and oligo-mesotrophic
rivers
Type
VII Mesotrophic rivers
dominated by gravels, pebbles and cobbles
Type
VIII Oligo-mesotrophic rivers
Group
D Acid and nutrient-poor
rivers
Type
IX Oligotrophic
low-altitude rivers
Type
X
Ultra-oligotrophic rivers
Related publications
- Holmes, N.T.H., Boon, P.J. & Rowell, T.A. 1998. A revised
classification system for British rivers based on their aquatic
plant communities. Aquatic Conservation: Marine and Freshwater
Ecosystems, 8: 555-578.
- Holmes, N.T.H. 1983. Typing British rivers according to
their flora. Peterborough, Nature Conservancy Council. (Focus
on nature conservation, No 4.) NB: this is the original 1983
NCC classification for rivers, which is now out of print.
The British Lakes Vegetation Communities
Classification
Introduction
The Vegetation Communities of
British Lakes: a revised classification is based
upon the composition of aquatic plant communities in lakes. It
comprises eleven distinct Groups (see
below), each of which is described in the publication along
with a distribution map. It also includes a scoring scheme,
called the Plant Lake Ecotype Index (PLEX). Changes in this index
reflect the complex response of freshwater plant assemblages to a
large number of environmental variables, especially alkalinity and
pH.
Brief history
The first comprehensive classification scheme for British lakes
(Palmer 1992) was based on macrophyte surveys carried out between
1975 and 1988 by the Nature Conservancy Council (NCC). This was
based on 1,124 lakes throughout England, Scotland and
Wales.
Since then, the NCC and its successor organisations
(Countryside Council for Wales, Natural England and Scottish
Natural Heritage) have commissioned a substantial number of
additional lake surveys, leading to the establishment of a much
larger dataset. This includes records from 3,447 sites (310 in
England, 38 in Wales and 3,099 in Scotland), the distribution of
which is shown right.
The advent of the Habitats Directive and, more recently, the
Water Framework Directive provided the incentive for the production
of a revised classification using this larger dataset, supplemented
by environmental data.
Right: distribution of lake macrophyte
surveys included in the JNCC Lakes
Classification (the gridlines delineate 100-km
squares)
Description of Lake Groups
The lakes classification comprises
eleven distinct Groups (A-J). A large number of lakes fall into
Group C, which is sub-divided into Groups C1 and C2 on the basis of
taxon richness. The following list provides a summary description
of all of these groups:
Related publications
- Duigan, C., Kovach, W. & Palmer, M. 2006. Vegetation communities of
British lakes: a revised classification.
Peterborough, Joint Nature Conservation Committee.
- Duigan, C., Kovach, W. & Palmer, M. 2007. Vegetation
communities of British lakes: a revised classification scheme
for conservation. Aquatic Conservation: Marine and Freshwater
Ecosystems, 17: 147-173.
- Duigan, C., Kovach, W. & Palmer, M. 2008. Aquatic
macrophyte classification, distribution, and traits in British
lakes. Verh. Internat. Verein. Limnol, 30: 477-481.
- Palmer, M. 1992. A botanical classification
of standing waters in Great Britain and a method for the use of
macrophyte flora in assessing changes in water quality.
Peterborough, Joint Nature Conservation Committee. (Research and
Survey in Nature Conservation, No. 19.)*
- Palmer, M.A., Bell, S.A. & Butterfield, I. 1992. A
botanical classification of standing waters in Britain:
applications for conservation and monitoring. Aquatic
Conservation: Marine and Freshwater Ecosystems, 2:
125-143.*
* these two publications relate to the
original 1992 JNCC Classification of Lake Vegetation
Communities