Freshwater classifications

Introduction

River Bovey, Devon, England Peter Wakely, Natural England

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: 

 

 

Cover of Vegetation communities of British riversHolmes, N.T.H., Boon, P.J. & Rowell, T.A. 1999.

 

Vegetation Communities of British Rivers: a revised classification.

 

Peterborough, Joint Nature Conservation Committee.

 

 

 

Vegetation Communities of British Lakes cover

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

IntroductionThe River Tarf, Glen Tilt, Scotland © Lorne Gill, Scottish Natural Heritage

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:

  1. 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.
  2. River Community Types.  This second tier of division comprises ten River Community Types (RCTs) (I-X).
  3. 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.
 

 

 

Dystrophic lakes in the Flow Country, northern Scotland © Steve Moore, Scottish Natural HeritageThe 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. 

 

Distribution map of lakes included in the JNCC Lakes ClassificationSince 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:

  • Group B.  Widespread, usually low-lying acid moorland or heathland pools and small lakes, with a limited range of plants, especially Juncus bulbosus, Potamogeton polygonifolius and Sphagnum species.
  • Group C1.  Northern, usually small to medium-sized, acid, largely mountain lakes, with a limited range of plants, but Juncus bulbosus and Sparganium angustifolium constant.
  • Group C2.  North western, predominantly large, slightly acid, upland lakes, supporting a diversity of plant species, Juncus bulbosus constant, often with Littorella uniflora and Lobelia dortmanna, in association with Myriophyllum alterniflorum.
  • Group D.  Widespread, often large, mid-altitude circumneutral lakes, with a high diversity of plants, including Littorella uniflora, Myriophyllum alterniflorum, Callitriche hamulata, Fontinalis antipyretica and Glyceria fluitans.
  • Group E.  Northern, often large, low altitude and coastal, above-neutral lakes with high diversity of plant species, including Littorella uniflora, Myriophyllum alterniflorum, Potamogeton perfoliatus and Chara species.
  • Group F.  Widespread, usually medium-sized,  lowland, above neutral lakes, with a limited range of species, but typified by water-lilies and other floating-leaved vegetation.
  • Group G.  Central and eastern, above neutral, lowland lakes, with Lemna minor, Elodea canadensis, Potamogeton natans and Persicaria amphibia.
  • Group H.  Northern, small, circumneutral, lowland lakes, with low species diversity characterised by the presence of Glyceria fluitans and Callitriche stagnalis.
  • Group I.  Widespread, mostly moderately large, base-rich lowland lakes, with Chara species, Myriophyllum spicatum and a diversity of Potamogeton species.
  • Group J.  Northern coastal, brackish lakes, with Potamogeton pectinatus, Enteromorpha species, Ruppia maritima and fucoid algae.

 

Related publications

* these two publications relate to the original 1992 JNCC Classification of Lake Vegetation Communities