Boundary House Fen, Frilford Heath Golf Course - Saturday, 18 January 2025
Blog by Sally, photos by Eleanor and Sally. Credit also to Dr Judy Webb for her fen desciption below.
Thirteen Green Gymmers returned to Boundary House Fen on Saturday, 18 January, for our first ever official all day session, to resume the cutting and raking of reed, rush and other vegetation in order to allow light for seeds to germinate of more delicate and rare fen plants. Many people do not realise, but Oxfordshire is one of the very few places in the world (yes, that's right, the world!) where alkaline (or calcareous) fens exist due to the county's complex geology and where a layer of limestone lies above impervious clay - and this combination of layers does not occur in many places, which makes alkaline fens so rare and precious. Fens are continuously fed by springs. For an alkaline fen to form, rain enters the soil in the catchment area and percolates slowly into the ground, becoming more acidic from the respiration of living plant roots and soil organisms, which produce CO2 (which is slightly acidic). As it percolates further, the acidified groundwater dissolves porous limestone and the water becomes "hard" (similar to that which makes limescale in your kettle). When it reaches the impervious clay layer beneath, the water then seeps sideways and downwards until it emerges continually from the spring or seepage zones. The continuous water emergence (which has occurred over tens or perhaps even hundreds of thousands of years) encourages wetland vegetation and the accumulation of dead plant remains forms peat, which is a huge wet carbon store (a 30cm deep peat layer over a certain area contains more carbon than the same area of rainforest.)
The calcium in the water causes alkaline conditions and deposits in the form of a crust of whitish limescale (or tufa) on the fen surfaces, encouraging a great biodiversity, supporting a community of plants and invertebrates (with many now rare species, as these fens are under threat due to draining (by creating ditches) and development on the catchment area, as well as excavation by quarrying.
So, we continue with the good work at Boundary House Fen, by cutting down tall, dense species such as reed and rush, which choke out many other species and by packing the cut material into the ditch that was created in the middle of the fen, we are gradually re-wetting it, storing vital carbon (thus helping to combat climate change) and creating favourable conditions for the fen specialists to thrive.
Adrian had arrived early with the tools, but unfortunately, we had to wait to be let through the gate. The last time we were here, Judy Webb had brought some maiden pinks along, which had been nurtured by Michele, and she planted them out on one of the heathland areas of the Golf Course, which the Green Keepers had removed a lot of gorse. To ensure they thrive, she needed a couple of volunteers to help her remove some sprouting brambles and other scrub, using small mattocks and a tree popper, away from the last known patch where the maiden pinks grew last year. Eleanor and Lesley put their hands up to help and off they went, whilst the rest of us trooped off with Adrian to meet Rod on the Fen. Rod had already started digging out a leat, monitoring it after every spadeful, the intention being to divert water around the fen area so as to help re-wet it instead of encouraging it to flow in the man-made stream, which is acting like a ditch. The rakers and pitchforkers set off to carry on raking the cut vegetation from our session in December, and Rod directed the scythers to continue cutting.
It was rather chilly, but we only felt the cold (some people had even taken off a layer or two!) when we stopped working for a very welcome break, when we were joined by Judy, Eleanor and Lesley fresh from their digging. The geology of the Golf Course is very rich, with the mix of heathland and fen and the sandy soils of the heath favour completely different plants, such as the delicate maiden pink. It is this complex geology, which has allowed specialist flora and fauna to evolve and thrive over time, that makes this a SSSI - Site of Special Scientific Interest.
After break, Rod asked if anyone wished to change what they were doing and give him a helping hand with the digging out of the leat. Henry volunteered for this and the wheelbarrow and spade was put to good use, using a spirit level to follow the contours around a couple of trees.
At our customary finish time of 12.30pm, those who weren't staying on said their farewells. The rest of us stopped with our packed lunches and when suitably fortified, we got back to it. We finished at about 2.30pm, having achieved a lot of good work. Unfortunately, the fen, heath and much of the Golf Course is currently under threat from the proposed Tubworth Quarry on nearby fields, but in the meantime we continue to do what we can to restore it and look forward to returning again soon.
A heap of the pulled up vegetation
Comments
Post a Comment