Key to Aquatic Communities

Summary

Much aquatic vegetation is relatively poor in species and many of the communities we have defined are overwhelmingly dominated by one or two taxa. In this case, in place of the usual dichotomous key or branching hierarchy of questions used elsewhere in the scheme, we have devised an alternative aid to identification of assemblages based on a synoptic table of species represented in the various vegetation types.

All sub-communities have been included in the table and those species diagnostic at frequency II or more rearranged in alphabetical order (Figure 5). As always, because the major distinctions between the communities and sub-communities are based on interstand frequency, this tabular key will work best where a number of samples of similar composition have been collected and made into a constancy table. It is the frequency values in this which should then be used to check for overall similarity with the vegetation types in the table.

Samples should always be taken from homogeneous stands and by2x2mor4x4m according to the scale of the vegetation or, where stands are narrow or of irregular form, of identical area but different shape. Small stands can be sampled in their entirety unless the vegetation is very fragmentary.

1 Lemnetum gibbae

2a Lemnetum minoris, Typical sub-community

2b Lemnetum minoris, Lemna trisulca sub-community

2c Lemnetum minoris, Riccia fluitans-Ricciocarpus natans sub-community

3 Spirodela polyrhiza-Hydrocharis morsus-ranae community

4 Hydrocharis morsus-ranae-Stratiotes aloides community

5a Ceratophylletum demersi, Ranunculus circinatus sub-community

5b Ceratophylletum demersi, Lemna minor sub-community

7a Nymphaetum albae, Species-poor sub-community

7b Nymphaetum albae, Juncus bulbosus-Potamogeton polygonifolius sub-community

8a Nuphar lutea community, Species-poor sub-community

8b Nuphar lutea community, Callitriche stagnalis-Zannichellia palustris sub-community

8c Nuphar lutea community, Nymphaea alba sub-community

8d Nuphar lutea community, Potemogeton obtusifolius-Juncus bulbosus sub-community

9a Potamogeton natans community, Species-poor sub-community

9b Potamogeton natans community, Elodea canadensis sub-community

9c Potamogeton natans community, Juncus bulbosus-Myriophyllum alterniflorum sub-community

10 Polygonum amphibium community

11a Potamogeton pectinatus-Myriophyllum spicatum community, Potamogeton pusillus sub-community

11b Potamogeton pectinatJs-Myriophyllum spicatum community, Elodea canadensis sub-community

11c Potamogeton pectinatus-Myriophyllum spicatum community, Potamogeton filiformis sub-community

12 Potamogeton pectinatus community

13a Potamogeton perfoliatus-Myriophyllum alterniflorum community, Potamogeton berchtoldii sub-community

13b Potamogeton perfoliatus-Myriophyllum alterniflorum community, Potamogeton filiformis sub-community

14 Myriophylletum alterniflori

15 Elodea canadensis community

16a Callitriche stagnalis community, Callitriche spp. sub-community 16b Callitriche stagnalis community, Potamogeton pectinatus sub-community