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| East Anglian Plain |
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| Habitat: Lowland wood pasture and parkland (of national significance) |
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This is the product of historic land management systems, and is a vegetation structure rather than a specific plant community. This structure consists of large trees (often pollards) at varying densities, in a mosaic of grazed grassland, heathland and/or woodland.
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Many parks were set up in mediaeval times for aesthetic reasons, and also to provide grazing for farm animals or deer and to provide wood from pollarded trees. In later centuries, new landscape parks were made from old mediaeval parks or by enclosing ordinary farmland. Two of the British top forty deadwood invertebrate sites are in the East Anglian Plain. Hatfield Forest National Nature Reserve originated as a Royal forest where deer were protected, and Shrubland Park was a pasture-woodland not used for deer.
The nature conservation interest of parks and pasture-woodlands come from having a continuity of old trees over hundreds of years, or even in some cases back to the post ice-age wildwood. Oaks are found in practically all sites, with sweet chestnut featuring in some places and hornbeam in others. Many parks and pasture-woodlands are associated with ancient coppice woodland or secondary plantation, adding habitat diversity to the core feature.
Rotten wood in the centre of ancient tree-trunks, looking like damp red sawdust, is home to a high number of invertebrates not found elsewhere. Many of these invertebrates are beetles or their larvae. Other dead wood is also valuable invertebrate habitat. Rugged cracked bark has its own range of specialised invertebrates. For example there is a spider Nuctenea umbratica closely related to the common garden cross spider, which has a flattened body to allow it to get underneath bark. Most invertebrates have a dispersal stage. Beetle larvae that live in rotten wood may have nectar-feeding or predatory adults, which fly or walk up to possibly a few hundred metres. As concentrations of ancient trees are few, a beetle leaving its park is unlikely to find another ancient tree. If dead wood is removed, there will be nowhere to go and the whole population will disappear. It is for this reason that only sites with a long history of ancient trees and dead wood have important invertebrate populations. Isolated ancient trees normally have those invertebrates which are good colonisers and so are more common.
Lichens rely on the stability of the surface provided by ancient trees for their support. Most of the uncommon species are found on ancient tree trunks where they have had centuries to grow. Ancient trees are also good places for hole-nesting birds. Woodpeckers find it easy to drill holes in old and/or rotting wood, and there are plenty of holes for other birds such as barn owls to use.
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