Dr M’s field day diary #3 – eXtreme botany in the water!

This week Dr M has been taking his MSc students on a series of field days, visiting a range of sites and habitats. Here is the third post from Dr M’s field day diary:

Day 3: Botany at historical Runnymede

Not far from where the Magna Carta, was sealed by King John way back in 1215 at Runnymede, Dr M and his students investigated a backwater of the River Thames working their way through a mosaic of swamps, fen and aquatic communities.

Calling for Volume 4 of British Plant Communities: aquatic communities, swamps and tall-herb fens. 

Swamps are vegetation types of nutrient-rich wet soils where productivity is high (lots of biomass) but species richness is low. The vegetation is dominated by large emergent monocots characteristic of open-water transitions with permanently or seasonally submerged substrates.

At Runnymede include vegetation variously dominated by Glyceria maxima (Reed Sweet-grass), Phalaris arundinacea (Reed Canary-grass), and Phragmites australis (Common Reed).

Fens occur in similar places to swamps but are more species-rich characterised by a mix of some of the dominant mococots of the swamps combined with a variety of often tall perennial dicot herbs. At Runnymede, fen vegetation includes the following swamp graminoids:

Phalaris arundinacea (Reed Canary-grass)*
Glyceria maxima (Reed Sweet-grass)*
Carex riparia (Greater Pond-sedge)*

And also includes a range of other graminoids and perennial dicots including:
Carex acutiformis (Lesser Pond-sedge)
Carex disticha (Brown Sedge)
Carex otrubae (False Fox-sedge)*
Filipendula ulmaria (Meadowsweet)
Galium palustre (Common Marsh-bedstraw)
Lythrum salicaria (Purple-loosestrife)
Mentha aquatica (Water Mint)
Myosotis scorpioides (Water Forget-me-not)
Oenanthe fistulosa (Tubular Water-dropwort)
Stellaria palustris (Marsh Stitchwort)*

Aquatic communities as the name suggests are communities of open water and are assemblages of submerged or emergent plant species occurring together in transient or more permanent assemblages the composition of which depends on environmental factors such as substrate, water chemistry and water movement.

The aquatic communities of the open water areas at Runnymede are rather diverse and colourful in this relatively undisturbed stretch of slow flowing water and characteristic species are:

Emergent species:
Butomus umbellatus (Flowering-rush)
Glyceria fluitans (Floating Sweet-grass)
Glyceria maxima (Reed Sweet-grass)
Oenanthe aquatica (Fine-leaved Water-dropwort)*
Oenanthe fistulosa (Tubular Water-dropwort)
Rorippa amphibia (Great Yellow-cress)*
Rumex hydrolapathum (Water Dock)*
Sparganium erectum (Branched Bur-reed)

Floating species:
Hydrocharis morsus-ranae (Frogbit)*
Lemna minor (Common Duckweed)*
Persicaria amphibia (Amphibious Bistort)*
Ranunculus peltatus (Pond Water-crowfoot)*

Bankside vegetation also including quantities of the invasive Crassula helmsii (New Zealand Pigmyweed).

Submerged species:
Ceratophyllum demersum (Rigid Hornwort)
Lemna trisulca (Ivy-leaved Duckweed)*

Open water:
The main species of the open water in the centre of the river is beautiful displays of Nymphaea alba (White Water-lily)*