|
|
|
 |
| |
| Breckland |
| |
| Habitat: Lowland calcareous grassland (of national significance) |
| |
This type has largely developed on shallow lime-rich soils, usually over limestone rocks, and is typically managed as part of a pastoral or mixed farming system. It includes a variety of vegetation types but often has a very rich flora.
|
|
| |
Heather and grass heaths are best treated as a single complex as differences in soil type, oversometimes quite small distances, result in a mosaic of vegetation types from calcareous toacid grasslands. This may mirror underlying patterned ground and soil striping or simply thedepth of the overlying sands and the degree to which these have been leached of their chalkyelements. Alex S Watt's pioneering studies in the 1930s and 1940s on the dynamics of thesecommunities is a milestone in the history of plant ecology. He showed that soil type was themost significant differentiating factor between the five main grassland types (A-E) which hedistinguished. They range from very shallow, highly calcareous, moderately nutrient richsoils (A) to deep acidic heavily leached sands, poor in nutrients (E).
The most calcareous, grassland (A) occurs naturally at Lakenheath Warren and at a number ofother sites where chalk has been brought to the surface by man, notably Deadman's Grave,Thetford Heath and Little Heath Barnham. It has a broken turf of sheep's fescue and bareground on very shallow soil with many lichen and spring flowering annual plants. Specieswith poor competitive ability are favoured including Breckland specialities such as wallbedstraw, Breckland thyme and rare lichens including starry Breck lichen and scaly Brecklichen. Grassland (B) is the Breckland variant of the chalk pasture of the Downs andChilterns. It is more widespread than (A), occurring at Lakenheath Warren, Weeting,Foxhole and Deadman's Grave on deeper less calcareous soils. It has a continuous moss-richsward with up to 80 species of plants including chalk grassland species such as purple milk-vetch, purging flax, squinancywort and hairy rock-cress. The yellow flowering spikes oflady's bedstraw are common in summer with white field mouse ear and common stork's bill. Grassland (C) is similar and is also widespread. It is species poorer (about 60) on deepersoils where leaching allows more acid loving species such as heath bedstraw and shepherd'scress.
A combination of soil type, dry conditions, hard frosts, heather beetle and possiblyatmospheric pollution tend to favour grass rather than heather heath formation. Very heavyrabbit grazing also converts heather heathland to grass heath as is known now at CavenhamHeath and at Weather Heath in the past.
|
| |
|
