Askham Bog

European dewberry

The flora of Askham Bog is not only diverse, but also distinctly resembles plant assemblies in southern England.[2] Notable species include greater spearwort, marsh stitchwort, saw sedge, marsh fern, great water dock, meadow thistle, purple small reed, Carex appropinquata and water violet. Askham Bog also holds the largest and most north-eastern colony in England of the rare gingerbread sedge Carex elongata,[9] and is renowned for the presence of royal fern.

The vegetation of Askham Bog can be divided into two main groups, reflecting the broad underlying dichotomy between basic and acidic soil. One is a species-rich fen community around the margins. This includes characteristic species such as meadowsweet, common meadow rue, stinging nettle, marsh bedstraw, dewberry, bittersweet, skullcap, yellow loosestrife, creeping Jenny and rough meadow grass. The other community is a species-poor acid one towards the centre, including species such as Sphagnum palustre, purple moor grass, Rubus fruticosus and honeysuckle.[7] Although the drop in pH and elevational increase on the peat domes is attributable to sphagnum growth,[7] no sphagnum has been found in one vegetation assemblage characterized by honeysuckle and Rubus fruticosus within the acid centre of the bog.[10] This appears to be inconsistent with the usual course of succession and may be explained by unusually high concentration of inorganic phosphate.[10] Low water tables in the raised area may promote mineralization of phosphate, with low pH counteracting microbial conversion to organic phosphate, so that the resultant high inorganic phosphate component in the raised peat favours growth of this plant community.[10]

Over 90 bird species have been recorded on the bog, attracting both winter and summer visitors. Despite nearby potential sources of human disturbance, the bog provides a suitable shelter within a relatively bare surrounding agricultural landscape and has a rich fruit and seed supply in winter and a richness of invertebrates in summer.[2] Known residents include marsh tit, willow tit, treecreeper, kingfisher, goldcrest, bullfinch, tawny owl, buzzard, sparrowhawk and sometimes green woodpecker[11] Winter visitors include fieldfare, redwing, brambling, siskin, lesser redpoll, goldfinch, snipe, jack snipe, woodcock, coot and sometimes grasshopper warbler.[11] All migrant warblers have been found at the bog in spring and summer,[11] with the reed beds in the northeast part in Near Wood comprising an important colony for reed warblers.[2]

Askham Bog is rich in invertebrates, and is nationally known for its diversity of water beetles such as Haliplidae, Noteridae, Dytiscidae and Gyrinidae. Some rare beetle species include Dromius sigma, Agabus undulatus; alongside one record of Pselaphus dresdensis which has been found in moss from pond sides at the bog and nowhere else in England.[2] However, beetle abundance and species richness have been noticeably declining at Askham Bog since the early 20th century,[2] coinciding with the establishment of a municipal dumping ground at the adjacent Challoner's Whin.[1] Other characteristic insect species include the fen square-spot moth[6] and the emperor dragonfly.[1]

Regarding spiders, there is a surprisingly large proportion of wetland indicator species given the relatively dry status of the reserve and gradual encroachment by trees. This may be because the spider community reflects a time when the bog was wetter and is yet to completely respond to the habitat changes.[12] A very rare spider species Cornicularia kochi (O.P.-C) in its hundreds has been recorded in piles of cut-down Phragmites during winter.[3]

Typical amphibians of Askham Bog include common frog, common toad, and smooth newt. Typical mammals include roe deer and red foxes. The water vole was once common at Askham Bog, but has now been largely eradicated by the American mink.[11]

From the early Roman period until the mid-18th century, Askham Bog and its vicinity appeared to be intensely exploited for peat as fuel.[2] The earliest evidence of nearby peat cutting from the Roman period has been found in a Roman well in York in the form of lumps of sphagnum peat.[13]

In the Middle Ages, peat was cut especially by the villagers of Dringhouses and Acomb. Documentary evidence for this exists in the written bylaws of the Manor of Drighouses and Acomb Court Rolls restricting peat cutting by tenants. The severe penalties imposed by these legal restrictions testify to the need to counteract the damaging intensity with which peat would have been extracted from the bog.[2] In fact, intensive peat cutting had probably caused substantial topographical changes on the bog since its original geographic formation. In turn, a lowering of the acid peat layer due to extraction would have allowed the centre to become flooded by base-rich groundwater, thereby re-transforming it into an open fen.[2] Other material evidence exists in the form of dykes surrounding the current main peat domes, of which the former would have been dug to aid removal of peat by boat.[7]

The whole bog reverted to tree cover after cessation of peat cutting around the 1750s.[2] It was then extensively used as game covert from the late 19th century until the Second World War, which probably explains the extensive felling of Far Wood during this time. The bog was acquired in 1946 by Sir Francis Terry and Joseph Rowntree, who subsequently both awarded it to Yorkshire Naturalists' Trust (now Yorkshire Wildlife Trust) in 1946. It is Yorkshire Wildlife Trust's oldest nature reserve.[12]

There is fossil evidence in the form of hemp achenes and pollen found preserved in distinct horizons between layers of fen peat and Scorpidium-Sphagnum peat that this plant was once cultivated at Askham Bog[14][15] These seeds and pollen are possible relics of retting (steeping in water) of hemp because pollen of aquatic plants such as water lilies and cattails have been found together with hemp seeds and pollen in the same peat cores, therefore suggesting that these hemp remnants were submerged during this period.[15]

Although exact time spans are unknown, cultivation of hemp at Askham was probably intense in the Tudor period when the crop was grown and retted extensively and by royal decree in England for hempen ropes for the British navy. There is some documentary evidence for this at Askham Bog in the Acomb Court Roll of 1594, which restricted where hemp could be retted (steeped) owing to the malodour produced by retted fibres and the potential for the retting water to pollute rivers.[2] However, hemp retting ceased in the 19th century with increased importation of hempen rope from Europe and Russia and the increasing reversion to sisal from America and jute from India.[14]

The commitment to preserve and conserve Askham Bog was the original reason for the Trust's establishment.[12] The first management plan aimed to maintain habitat diversity throughout the bog. With the aid of the National Conservation Corps, more open water was created through pond digging and dyke blocking, along with scrub clearance in the damp cotton-grass areas. In 1998, Yorkshire Wildlife Trust obtained a substantial Heritage Lottery Fund for restoration of many of its nature reserves. A considerable proportion of this grant was invested in management of Askham Bog to ensure adequate water quality and level required for the bog wildlife.[12]

Most of the species-rich fen areas are grazed by Exmoor ponies to encourage early successional plants such as marsh orchid and meadow thistle, and to suppress vigorous grasses, reed and saplings.[16] This is considered to be a more effective means of management than cutting. However, some meadows on site are still cut for hay.[1]