The final field trip of the year saw the convoy of MSc students, along with the ever present Christian Dunn and NRW’s Justin Hanson and Peter Jones navigate the Cors Bodeilio lime-rich fen once more.
After passing the constructed wetlands (see previous blog), the
group moved along a boardwalk installed during a recent restoration project to
connect the fen with Bodeilio village. Installation called for careful planning
to elevate it off the ground to allow for soligenous (lateral) water movement in
to the fen. Arriving at an area known as fly orchid spring, where one of best
examples of rare M13 Shoenus nigricans
(Black-bog rush) community in the UK is found, its rareness akin to having an
Osprey land on your garden bird table!
The small shed is a water abstraction for the farm house.
A permanent borehole has been placed
into limestone bedrock so any development work can be monitored against baseline
water levels in the future. Ponding of water on the opposite side of a boundary
wall could also be stopping surface water getting into the fen.
A permanent borehole or a drinking fountain for the thirsty wetland scientist?
Site assessment
After
carrying out a site assessment using a rich-fen site condition recording sheet developed by NRW peatland specialists to give
a quick estimate of site quality, it emerged that not only is it important to
assess vegetation condition but important “off-site” features should be noted. Changes
in water quantity and quality both affect the functioning of the fen. For
example, most the houses surrounding the fen are not on mains water. How much
does drinking water abstraction affect water quantity? What if more or less
drinking water is taken in the future? It was assessed that vegetation had a
slightly too high cover of graminoids, not enough dicots, small sedges, brown
mosses. This may have been as a direct of high litter cover (80%) as there was
no immediate evidence of enrichment, however the site margins had high tree
cover indicating drier conditions and surrounding fields were very green in
colour indicting some fertillizer use. The site had little thatch build up and a Dutch
auger found peat depth was 30 cm underlain with clay and sand stratigraphy.
Clay is thought to be constraining groundwater inflow at some of the drier
areas of the fen which, characterised by less hydrophytic species.
Dutch Auger used to make cores in the soil to get a idea of the stratigraphy
Fly orchid
spring is thought to be fed from and sand and gravel aquifer at a rate of
17,000 litres/day. Whilst stable
groundwater temperatures of 10°C keeps the soil warm year round and winter
snowfall immediately melts on landing maintaining an area of exposed vegetation
on the fen for livestock access. The local council have expressed fears that
the wetland water level is too high and this causes seasonal flooding of the
road leading into the village, however a ditch draining the fen could not be
deepened or widened for fear drying the fen too much leading to lost species of
conservation interest such as back bog rush, sweet gale and small flowered rush
as well as the rare dwarf stonewort, narrow –leaved marsh orchid and fly orchid. Ref: SH5e: Thursday 7th May 2014
Weather: Dry but cloudy (90r)
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