H3: Wet Heath
H3: Wet Heath
Wet heath occurs in two situations. Firstly in shallow hollows in surrounding dry heath (these can be quite big hollows!) or, secondly, as a transitional phase between dry heath and valley mire and bog. Wet heath is not generally permanently wet tending to dry out in periods of relative drought.
Formed on acid soils with a thin layer of peat it favours hardy but shallow rooted vegetation with a predominance of sedges and rushes but also some specialist flora features. Cross-leaved heath is often a dominant species as opposed to ling and bell heather in dryer conditions. The intermediary nature of the environment means that species dependant on surface water to be present such as oblong-leaved sundew is not found whereas round-leaved sundew that can survive happily in damp conditions as well as near standing water thrives on bare mud patches.
Insect fauna, being mobile, can move between neighbouring habitat types as water levels vary to suit their requirements. Quite often, pools that never dry out form which are acidic in nature and favour several species on dragonfly and damselfly. The mosaic combination of dry heath, wet heath and valley mire and bog are essential for some quite rare insect species such as the Southern damselfly and the large marsh grasshopper.
In general, wet heath is generally far more accessible than valley bog and mire although after very prolonged wet periods they may become impassible.
Under the Phase 1 habitat survey classification system wet heath is coded as D2 and is described as follow:
"A s with dry dwarf shrub heath (D1) this vegetation type has more than 25% cover of encoides and/or small Ulex (gorse) species. However, it differs from D1 in that Molina caerulea (purple moor grass) is often abundant and it generally contains some Sphagnum compactum 0r Sphagnum tenellum and less frequently other sphagna.
In transition to mires the proportion of Sphagna will increase and the species composition will change often with Sphangum papillosum and Sphagnum subnitens becoming more frequent. Erica tetralix(cross-leaved heath) is common in wet dwarf shrub heath and is often present in significant quantity. Trichophorum cespitosum (deer-grass) is occasionally present at lower levels. Macrolichens such as Cladonia portentosa , Cladonia arbuscula and Cladonia uncialis may be locally abundant. The abundance of Molina and Erica tetralix decreases in the transition from wet to dry heath."
Under the National Vegetation Classification system wet heath is classified primarily as M15/M16 and H5.