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Grassland Management for Nature Conservation
Grassland Types
The type of grassland community found on a site will depend on a number of factors:
• soil conditions (nutrient levels, pH and water level),
• climate and altitude,
• past and present management.
Acid grassland communities are most widespread in areas of
more acidic soils and geology. These are generally at higher altitudes
and in the north and west of the UK. There are some areas of lowland
acid grassland and these tend to be more species rich.
Old hay meadows are usually left ungrazed for the spring
and early summer allowing herbs and grasses to flower and set seed
before cutting. The flora is often very rich.
Wet grasslands are poorly draining and/or periodically
flooded. Unimproved wet grasslands have their own distinct, and often
diverse, flora as well as a rich invertebrate fauna. They are also good
habitats for wetland birds.
Calcareous grasslands
are found on soils with higher pH often over chalk or limestone.
Unimproved calcareous grasslands are the most floristically rich of the
grassland communities. Lowland grasslands were often managed by
extensive sheep grazing. Together with rabbits they created a short
turf with many low growing herbs and grasses.
Many
species-rich grasslands have been lost because of agricultural
improvement. Most suitable areas have been ploughed up and reseeded
with a few, more productive species (e.g. Ryegrass). This has often
been accompanied by fertiliser applications, liming (to increase pH),
drainage and changes to grazing pressure. These are also important
factors for a nature conservation manager to be aware of when managing
grasslands.
Nutrients and Fertility
Ecologically
valuable grasslands are generally found on nutrient poor soils.
Increased nutrient levels allows a few more vigorous and competitive
species to dominate (especially grasses). Adding nutrients is not,
therefore, an appropriate management technique, for nature
conservation.
The residual nutrient levels in soil are
the reason why the recreation of species-rich grassland on previously
improved sites can be a very long process.
Removing any cuttings from a site is usually part of conservation management, in part to remove nutrients.
Valuable wet grasslands have been lost because of increased drainage
lowering the water level. The management of water levels through ditch
systems and pumps in areas such as the Somerset Levels is very complex.
It is sometimes difficult to control water levels in these areas
without the agreement and co-operation of other surrounding landowners.
Grazing, Cutting and Burning
Changes
in the nature conservation value of a site can result from changes to
the grazing or cutting regimes. Grassland is a community where natural
succession (through scrub and eventually woodland) is halted by
grazing. Removal or reduction of grazing can cause undesirable
consequences of decreased floristic diversity and invasion of scrub.
Some features of grazing that affect its use in nature conservation management are:
• the intensity of grazing (number of animals),
• the pattern of grazing (e.g. all year, seasonally or just occasionally) and
• the type of grazing animal.
Using
grazing animals for management also requires the conservation manager
to fence or stockproof an area, find suitable stock to use and be aware
of issues such as animal husbandry and welfare. Sheep, cattle, horses
and goats all graze or browse in different ways and animals appropriate
to the objectives of the management should be used.
A simpler option is to cut an area. This does have different ecological
effects since cutting is non-selective whereas most grazers are
selective. Cutting will only be done a few times (maybe less than once)
in a year. The height of cutting also affects the plants and
invertebrates that will be encouraged. As mentioned above, it is
important to remove cuttings since these cause nutrient enrichment and
can smother smaller plants.
Burning of vegetation is a management tool used on heathlands and on
heaths and moors in the uplands. It is occasionally used on some upland
grasslands (e.g. dominated by Purple Moor Grass). However, this not an
appropriate tool for managing most grasslands.
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