OS: 121 • GR: SK 911661 • Map Ref: 69

Whisby Nature Park: Management for Biodiversity

The Grasslands of Whisby Nature Park

Orchid Glade

 

This location in the north-west sector of Grebe Lake, consists of a plateau of waste clay, sand and gravel from the Grebe Lake excavation, lying close to the water table.  The low elevation and compression suffered from years of heavy trucks passing over parts of it, combine to provide generally very wet conditions which favour a specific range of flowering plants.  The pond in the Orchid Glade also rises and falls with the seasons and contains very clear water.  This type of landform is rather rare in gravel pits. The grassland gives way to marginal reeds and other aquatic plants near the lake edge. The habitat is maintained by a small dam which causes flooding during the winter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 This is the conservation triumph of Whisby Nature Park and one of the biggest attractions to visitors during June. During the early 1990's the area was developing a heavy scrub of birch and willow, amongst which a few dozen southern marsh orchids were declining under the increasing canopy.  The decision to remove this scrub has resulted in a colony counted at over 9,000 in 2008.  During this development, it was necessary to transform the coarse growth that followed the initial felling.  The use of chemicals on the tree stumps, followed by regular cutting and removal to encourage grass species gradually allowed the orchids to spread and multiply.  Now that grazing has been added to the management armoury, the process is being transferred to adjacent waterside areas to extend the potential.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Among the plants to be seen in abundance are lady's smock, yellow rattle, marsh bedstraw, meadowsweet, fleabane, cowslip, southern marsh orchid, common spotted orchid and both species of bullrush. Less common species present in small numbers include devil's-bit scabious, sneezewort and betony.

 

 

 

Little Heath

 

This area can be found in the north east corner of Grebe Lake.  A fenced grazing area includes a very small patch of specialised vegetation containing some of the plants that would have been very common on the heathland that originally covered the whole Nature Park site.  The conservation aim has obviously been to extend this 'window on the past' to cover the entire grazing area.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Unfortunately this has not been successful so far because of the mixing of top-soil into the surrounding area. top soil mounds line the entire northern edge of Grebe Lake except at this point and it is clear that the heathland soil has almost all been buried by bulldozing some time before the Nature Park was established.  The tiny remaining fragment contains heather, broom, birch, mountain ash, harebell, heath bedstraw, common spotted orchid, umbellate hawkweed and great burnet.  The remaining 'topsoiled' area is developing into interesting dry grassland under the grazing and cutting regime, but resists the colonisation of the more interesting species.

 

 

 

Wet Heath 

 

This adjacent area comprises the lake edge 'downhill' from the Little Heath, where the acid conditions combined with a high water table have produced a markedly different habitat.  The development of birch and alder scrub had threatened this grassland and winching rather than cutting, was employed to remove the trees which had shallow root systems leaving small depressions as pools.  The pools often develop growths of sphagnum moss, and the surrounding rushy areas have tormentil.  Neither of these plants are found anywhere else on the Nature Park.  The Hebridean sheep graze this area which is too wet for mechanical cutting.

 

 

 

Pylon Enclosure 

 

This is a dry grassland between Coot Lake and West Lake which was subject to invasion by surrounding hawthorn, willow, rose and gorse.  The grasses were also becoming quite coarse with a loss of small flowering plants.  Sheep grazing has turned this around with an increase in fine grasses and in particular the associated anthills.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Grazing Marsh

 

The largest grassland project on the Nature Park is located in the northern part of the Magpie Walk.  The depression which forms the Grazing Marsh was once a gravel pit, but was adapted for use as a settlement lagoon during the extraction years.

 

Liquid mud from the cleaning and sorting process was pumped into the pit so that when the particles had settled out, the clean water could be re-used.  This was necessary owing to the lack of flowing water on the site to bring fresh supplies.  The pit eventually filled up with clay and became a swamp with reedmace, then a willow marsh, until the pumping ceased and the surface gradually firmed up enough to walk on.

The decision to clear 15 acres of willow was a major one but the prize some nine years later is seeing an unimproved wet clay grassland developing year by year.  Most of the potential has still to be achieved and a few acres are still under willow.  There is a colony of southern marsh orchids and a small community of grassland flowers is developing. Some such as fairy flax, devil's bit scabious and sneezewort are due to seed introductions.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A few species of wildfowl use the marsh during wet winters and woodcock might be seen during the migration periods.  The whole area was fenced for grazing during 1999 and cattle are often to be seen here. Grazing management is augmented by 'hay-meadow' cutting and raking when necessary.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thorpe Lake Peninsula 

 

This obvious feature in the southern shore of Thorpe Lake is maintained as a sanctuary area and is relatively new to the Nature Park.  Parts are very dry but where soil compression and hollows coincide, there are mossy damp patches where snipe occur in winter.  The dry grassland is popular with green woodpeckers as ant hills are frequent.  A wide variety of small flowering plants occur; changing forget-me-not, parsley-piert, common storksbill, bee orchid and common centuary.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Near the water's edge on the eastern shore is a colony of the rare mint pennyroyal.  Rabbits control the advance of willow and birch scrub, which occurs mainly on the western side.  The site is grazed by Hebridean sheep to maintain an open sward.

 

 

 

The Triangle 

 

This piece of land, a failed tree planting scheme, is a new addition to the Nature Park and lies between Grebe Lake and the A46 embankment.  Before grazing commenced in 2000, this was a very coarse grassland.  Some of this coarse grass is outside the fencing and will be retained for the shelter it provides for small invertebrates.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The sward is now quite short and green hay and prepared seed have been spread in order to increase the floral diversity more quickly. Rushy areas attract snipe in wetter winters. This is another site with an outlying colony of southern marsh orchids.

 

 

 

Pike Drain Bank  

 

The south-facing bank of this deep drain has long been known as a haven for insects, especially butterflies, and a variety of flowering plants, and of course the two factors are connected. Greater burnet saxifrage, purple loosestrife, common St. John's wort, field pennycress, lady's bedstraw, common toadflax, cowslip and lesser knapweed are typical flowers to be seen. The bank is mown every autumn in conjunction with the statutary works of Upper Witham internal Drainage Board, and this management helps to keep the sward sufficiently open for natural seeding.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Teal Lake 

 

This young grassland has a sandy substrate, sometimes combined with clay. It is divided into an eastern and western section by a belt of scrub lining a drainage ditch. To the north lies a topsoil mound with tree planting which are outside the cattle fencing and will be allowed to develop.
 
To the east, the present surface was largely formed by bulldozing gravelpit waste left in longitudinal ridges which would have been problematical to manage. Of this newly-formed surface, a substantial area has been lost to scrub over the 7-8 years that have passed negotiating a lease. This is being reclaimed by felling and since 2008, browsing by Shetland cattle. A small proportion of scrub will be retained if a balance can be reached to support warblers and in particular reed buntings which have established there. In 2008 the flora of the drier areas is characterised by plants of open ground with bird’s-foot Ornithopus perpusillus, hare’s-foot clover Trifolium arvense and common centaury Centaurium erythraea. Grass species are still quite sparse. Wetter areas near the waters edge are all too often swathed with Crassula helmsii and it is to be hoped that some control measure can be found beyond spraying. This alien weed has severely restrained native marginal plants.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The western section has been left undisturbed for substantially longer, and grassland has formed, shutting out scrub growth, but the owner planted large numbers of widely-spaced but inappropriate trees such as cherry and mountain ash which have grown poorly and are likely to fall victim to browsing by cattle. To the north the grass is quite coarse but further south there is a heathy element supporting a few plants of the very scarce maiden pink, possibly the only current colony in the county.

Skylark and meadow pipit have both bred here and will benefit from continuing reduction of scrub cover and grazing by cattle. Grasshopper warblers are currently established in heavy bramble north of the eastern section which has been fenced so that cattle cannot browse.

 

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