Offwell Wetland Survey
Area C - Swamp Zone
| This area is permanently covered in
standing water. It lies on the edge of the open water zone and gives way to marsh behind
it, where the standing water levels vary and the sediment is not permanently covered by
water.
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On the southern edge of the wetland where the water depth is 1-10 cm deep, plants such as Water Mint (at left), Yellow Iris, Greater Reedmace, Branched Bur-reed, Willow and Common Duckweed are found in abundance. As water depth increases, the emergent vegetation develops into pure stands of Branched Bur-reed, with Canadian Pondweed and Various-Leaved Water-Starwort submerged beneath the water surface and Duckweed floating on the top. Branched Bur-reed dies out where the water depth exceeds 50 cm. |
| In the western swamp region of the wetland the composition of the vegetation is somewhat different. In the shallower regions, Water Mint, Yellow Iris, Greater Reedmace, Branched Bur-reed and Willow are found as in the southern swamp area, although here with the addition of Water-plantain, Greater Spearwort and Bogbean. The deeper water areas here consist of pure stands of Bogbean. In both regions, the substrate is composed of a deep fibrous tangled mass of rhizomes, roots and old leaf bases. The underlying sediment is black and anaeorobic. |
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| Salicaceae | t |
| Salix caprea agg. | Goat Willow |
| Betulaceae | t |
| Alnus glutinosa (L.) Gaertn. | Alder |
| Ranunculaceae | t |
| Ranunculus lingua L. | Greater Spearwort |
| Onagraceae | t |
| Epilobium palustre L. | Marsh Willowherb |
| Callitrichaceae | t |
| Callitriche platycarpa Kutz. | Various-leaved Water-Starwort |
| Callitriche stagnalis Scop. | Common Water-Starwort |
| Menyanthaceae | t |
| Menyanthes trifoliata L. | Bogbean |
| Labiateae | t |
| Mentha aquatica L. | Water Mint |
| Rubiaceae | t |
| Galium palustre agg. | Marsh Bedstraw |
| Alismataceae | t |
| Alisma plantago-aquatica L. | Water-plantain |
| Hydrocharitaceae | t |
| Elodea canadensis Michx. | Canadian Pondweed |
| Potamogetonaceae | t |
| Potamogeton natans L. | Broad-leaved Pondweed |
| Graminae | t |
| Glyceria fluitans (L.) R. Br. | Floating Sweet Grass |
| Juncaceae | t |
| Juncus effusus L. | Soft Rush |
| Iridaceae | t |
| Iris pseudacorus L. | Yellow Iris |
| Lemnaceae | t |
| Lemna minor L. | Common Duckweed |
| Sparganiaceae | t |
| Sparganium erectum L. | Branched Bur-reed |
| Typhaceae | t |
| Typha latifolia L. | Greater Reedmace |
| These species lists are not exhaustive. They represent initial collections and identifications carried out in early autumn. Many species of flowering plants may already have flowered and died back at this time and would therefore have been missed. These lists will be updated periodically. |
Back to Areas page Complete Survey Species List Back to Wetland diagram