Upland limestone pastures
Limestone grasslands are found across the uplands of Britain.
In the Brecon Beacons, the Yorkshire Dales and the Peak District they extend over large areas of pasture, whereas in other parts of the country smaller areas occur on limestone outcrops within other upland or moorland habitats.
These limestone pastures can be exceptionally rich in wildflowers such as rockrose, salad burnet and wild thyme, with rarer species such as mountain avens, spring gentian and alpine bistort. They also support many species of birds, reptiles and invertebrates. A range of other important habitats occur in limestone pastures including woodland and scrub, heaths and bogs, wet flushes, limestone pavements and scree.
Some of the largest expanses of wildflower-rich grasslands in Britain occur in upland limestone pastures. Steep, rocky or difficult terrain has limited agricultural improvements so many pastures retain a wide range of wildflowers and other wildlife. They provide good nutritional grazing for livestock.
More intensive grazing, along with a move to predominantly sheep grazing has led to many grasslands being harder grazed, creating shorter swards and preventing many plants from flowering. As a result, many wildflowers have been lost or decreased in number. Conversely in other areas, steep-sided limestone pastures have fallen out of agricultural management, resulting in encroachment of scrub and coarse grasses.
Limestone pastures are particularly important for the range of wildflowers which can thrive and bloom under light grazing regimes. When pastures are managed to produce a varied sward structure, they can also support good populations of insects, reptiles and ground-nesting birds such as skylarks, meadow pipits and lapwings.
Limestone pastures with a mixture of habitats such as scattered scrub, flushes or bog areas, and limestone pavements or scree can be particularly valuable to wildlife. Scrub can provide shelter for butterflies, other invertebrates, reptiles and nesting birds. Small areas of bracken can also be valuable for butterflies such as fritillaries. Wet areas support their own range of plants, including the bird’s-eye primrose and insect-eating butterworts, as well as providing home for a number of insects and snails.
Upland limestone pastures can be grazed for most or all of the year, however grazing management will vary according to the location and altitude of the pasture. It is important to consider how different habitats within a pasture will respond to grazing, for example wetter areas may be damaged with heavy winter grazing. The proportions of these different habitats will also alter the quantity and nutritional value of forage available to livestock and hence the stocking rate and period.
Upland limestone pastures provide good grazing for both sheep and cattle. Cattle create a more varied sward which benefits invertebrates and ground-nesting birds, and also enables more wildflowers to flower and set seed. Cattle are also better able to graze areas of coarse grasses such as mat-grass, blue moorgrass and tor grass, so can help to manage or reduce these more unpalatable species. Sheep will preferentially graze the more wildflower-rich ‘sweeter’ areas, leaving other areas relatively untouched.
As limestone pastures generally have thin, free draining soils they can be grazed at most times of the year without damaging the land. Reducing or ideally removing grazing for a 4-8 week period in the spring/summer will allow many plants to flower, which in turn provides valuable pollen and nectar for bees and other insects. Cattle are often the best grazing animal for this period as they are less likely to graze off flower heads. Reduced spring/summer grazing also reduces potential damage to ground-nesting birds and produces a more varied sward for a range of invertebrates, such as web spinning spiders.
Grazing off grass growth in autumn and winter is ideal as this is less likely to have an impact on wildlife. It is important to avoid significant poaching of the ground. Some taller grown tussocks should be left as winter cover for invertebrates. Spring grazing can be useful to manage more unpalatable grasses such as mat-grass and tor grass, however care must be taken to avoid grazing off early flowers such as orchids, and to prevent the trampling of nests.
Stocking levels will depend on the proportion of different habitats present, however suggested stocking levels are 2 ewe/ha (or cattle equivalents), reducing to 0-1 ewe/ha for a 4-8 week period in the spring/summer. Grazing may be higher later in the year in order to remove the vegetation and create a varied sward height. Intensive or ‘mob’ grazing can also be undertaken, to remove any excess grass growth.
Grazing impacts on other habitats of limestone pastures
A range of other habitats can be found alongside the limestone grasslands. Areas of scattered scrub which can develop on steep slopes, limestone pavements and scree provide valuable food, nesting sites and shelter for birds and insects. A cattle-only grazing regime can allow some scrub regeneration, however sheep will readily browse young tree/scrub seedlings. Cattle-only grazing regimes will also allow wildflower and fern growth on areas of limestone pavement and scree, as unlike sheep, cattle will rarely move onto and graze these rocky areas.
Limestone flushes need some grazing to prevent them becoming dominated by vigorous growing sedges and rushes. Grazing must be carefully managed to prevent flushes becoming heavily poached. Providing alternative water supplies can help to prevent livestock concentrating around flushes and other wet habitats.
Areas of limestone heath and other heather/bilberry habitats may be susceptible to autumn/winter grazing as livestock move from grazing unpalatable grasses to more nutritious ‘dwarf shrubs’, so animals may need to be removed in early autumn.
Other farming management
Fertlisers, farmyard manure and lime should not be applied to upland limestone pastures as this will increase fertility to the detriment of wildflowers and other wildlife.
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