It was a gorgeous sunny day last Sunday when we gathered at the southern edge of Kidbrooke Park to explore some of the wet woods and heath. It is an interesting corner of Forest Row, with a lovely range of habitats. At this time of year the bracken has all died back so it is easy walking (apart from the boggy bits), and it is possible to explore some wonderful hidden corners only a mile from the centre of the village.
Almost as soon as we started we paused to look at some of the diverse bryophyte flora of the woodland floor; along the bank (unsurprisingly) was Bank Haircap (Polytrichastrum formosum), as well as mats of the liverwort Diplophyllum albicans, cushions of the pale green Leucobryum glaucum, the spiky curved leaves of Dicranum scoparium, the darker green Mnium hornum, and shiny sheets of Pseudotaxiphyllum elegans.
The woods here grade into heathy understorey too, and Hypnum jutlandicum, the typical moss of the heathland floor is quite common, as is Pseudoscleropodium purum.
However, we didn’t want to spend too much time on these since we were heading for the wetlands. First off was a patch of woodland bog, a patch of diverse colours, which turned out to include several species of Sphagnum moss. Sphagnum can hold up to 20 times its own weight in water, and actively acidifies the space in which it grows, creating a unique ecosystem, and one which is tough for most other things to live in.
There are about 40 species of Sphagnum in Britain, though many of them are relatively rare and are only found on the west of Scotland. Even so, there are at least 13 in this part of Ashdown Forest, and they tend to have quite specific habitat requirements. Our bog in the wood was quite typical, and contained species that do well in the shade. Sphagnum palustre is unmistakeable; it is a big, chunky species that is often relatively pale and (in the winter months at least) has a darker centre (the capitulum).
Sphagnum denticulatum tends to be a bit smaller and may have some orangey tones to it; its branches often curve (“like cow’s horns” say the books).
Another common species in shady bogs is Sphagnum fallax. It is much more straggly, and has two short, downward-pointing branches between the main branches at the top.
In this bog we also found a smaller moss with a noticeably red centre. This was Sphagnum capillifolium ssp. rubellum. This is a very variable moss, and may be almost completely green in very shady locations, or very red in the open.
Not content with just looking at the mosses, though, we collected a handful of Sphagnum fallax to examine later to see what is living on it. Sphagnum mosses have been much studied since their very special biology makes them home to a unique range of other organisms, a few of which we found once we got home. Some of them are relatively large, like this oribatid mite:
However, if you squeeze the water out of the moss onto a microscope slide you can find a new universe of tiny species, such as nematode worms, testate rhizopods (amoebae with flask-like protective coats), diatoms (algae containing the yellow-brown photosynthetic pigment fucoxanthin, just like the brown seaweeds), fungal spores, and much, much more. Even within a bog pool there will be slightly different micro-habitats, whether at the top of the Sphagnum, or further down the stem in the wetter areas, or under varying degrees of shade, and each place may have different communities of these microorganisms.
Moving on, we followed the Kid upstream. Interestingly, all along its length in this part of the forest can be found the moss Hyocomium armoricum, which often has brighter tips to its regularly-branched form. This is a species with a particularly western distribution (it is very common on Dartmoor, for instance), but is rare in the south east, as the map below makes clear. Recent surveys have shown that it is much more widely distributed along ghyll streams in Ashdown Forest than was thought, so is probably a refuge population left over from after the last ice age.
The rarest plant of the day award had to go to a much smaller moss called Campylostelium saxicola. It can occasionally be found on stones in the forest streams, but only those that are not permanently wet. This colony is one of the biggest in the forest and almost covers a rather large rock.
Up the hill, the now-desiccated Purple Moor-grass (Molinia caerulea) covers a large area, grading from wet heath to valley bog. We were running out of time at this stage, so didn’t have a very thorough look in the bog, but did find some more Sphagnum capillifolium ssp rubellum, here much redder since it is in an open habitat, as well as the very wet and stringy-looking Sphagnum cuspidatum. This species is typical of bog pools and is usually immersed in them, looking a bit like porridge, or (as the books say) like a drowned kitten. Then Tom saw a fly and quickly potted it. It was a hairy, yellow thing, though turned out to be the extremely common Yellow Dung Fly (Scathophaga stercoraria) rather than anything more exciting.Still, heading back, Tom drew our attention to some of the birdsong; this corner of the forest is especially full of song first thing in the morning, though even by the afternoon there was a good range of things to listen to. Our final accompaniment was the repetitive sound of the Coal Tit (Periparus ater). This corner of Forest Row is a very special place, with many of its delights still to be discovered.
 For more detail on these species (which are a bit tricky) see ‘Heathy and boggy bryophytes of Ashdown Forest’ Diversions in Natural History. <https://diversionsinnaturalhistory.wordpress.com/2016/02/21/heathy-and-boggy-bryophytes-of-ashdown-forest/>
 Two useful guides to this environment are: (a) Hingley, Marjorie. Microscopic Life in Sphagnum. Slough: Richmond, 1993. (b) Sarah. A. Corbet (1973) ‘An Illustrated Introduction to the Testate Rhizopods in Sphagnum, with special reference to the area around Malham Tarn, Yorkshire’. Field Studies 3. 801-838. Available from: <http://fsj.field-studies-council.org/media/719711/vol3.5_92.pdf>