Some of the definitions below will require some explanation.
• Superficial deposits – Soil deposits typically from the Quaternary age.
• Gleying – Soils that get waterlogged and de-oxygenated. The microbe action that ensues removes iron from the soil.
Ill-drained permanent pastures In many mesotrophic soils, particularly those derived from impervious bedrocks such as clays and shales, and from superficials like till and alluvium, the maintenance of moderately high soil moisture is associated with some ground-water gleying.
Demarcation Areas
The demarcation between tended farmland and unkept and untended areas of grassland forms a fascinating and unique layer of change. A unique opportunity for various phenomena that encourages specific soil and flora types.
On the more frequently waterlogged and less fertile of these profiles, towards the boundary between agricultural improvement and neglect, mesotrophic grasslands grade into mires and inundation vegetation and among these swards we have characterised three communities. The general floristic feature of these assemblages is the preponderance of moisture-tolerant or moisture-loving plants.
Among the Molinio-Arrhenatheretea species, the most frequent and abundant are Holcus lanatus and Poa trivialis, while the common occurrence of Agrostis stolonifera, Ranunculus repens, Potentilla anserina and Rumex crispus provides a link with the vegetation of periodically flooded ground. The dominants, too, are among those species which occur most commonly on very moist, often waterlogged soils, with Juncus effusus, Deschampsia cespitosa, Filipendula ulmaria and Caltha palustris figuring prominently.
In contrast with the previously described communities, then, which are best located in the Arrhenatheretalia, these three vegetation types have strong affinities with the grassy, rushy and tall-herb assemblages of the Molinietalia, the other major order of the Molinio-Arrhenatheretea.
The Holcus lanatus-Deschampsia cespitosa grassland (MG9) and the Holcus lanatus-Juncus effusus rush-pasture form a pair of rather similar communities in which there is a trend towards dominance by D. cespitosa or J. effusus (with some J. inflexus on more base-rich soils) within a matrix of pasture grasses and dicotyledons. These are very widespread vegetation types of heavy unimproved or neglected agricultural land and their distinctive features have led some to suggest that they should be placed in special higher units such as a Deschampsion alliance and a Calthion sub-alliance, the Holco-Juncion.
The sad inference here is twofold.
Frequency of Testing Surveying
Firstly, that the unique definition and distinction of agricultural land is being homogenised by best practice farming methods with little consideration for agricultural heritage.
Secondly that the process that are changing the landscape are not being monitored as closely as they might be. It is entirely possible that new factors that influence these changes re being introduced and not being monitored given the low frequency of surveying and the lack of surveying resource,
In fact, the definition of these groups towards the Atlantic coast of Europe is rather indistinct and much in need of reassessment in the light of our increasing knowledge of British vegetation of this type: the Holco-Juncetum, for example, comprises just one element in a continuum of rush-dominated meadows and pastures across Britain with complex and shifting relationships to climate, soils and treatment.
A further community, the Cynosurus cristatus-Caltha palustris grassland (MG8), has a better representation of Molinio-Arrhenatheretea plants than the above swards and shows clearer affinities with our richer meadows and pastures of better-drained ground. It is, though, a very local community nowadays, surviving as a traditionally treated pasture on seasonally-flooded ground by rivers and streams in a few parts of lowland Britain.
Of further interest is the fact that it may represent the naturally occurring vegetation that formed the basis of the highly specialised swards of water-meadows.
At this point it is worth considering mans impact on the farming environment. The introduction of organised farming methods. The division of labour and the adoption of a distinct food supplier work type.
First created in the sixteenth and seventeenth centuries to supplement spring grazing on our southern Chalklands, these developed into complex systems of irrigated lands along valley bottoms where laborious hand-weeding selected for a grass-dominated herbage that was very productive and palatable.
European equivalents of our Cynosurus-Caltha grassland have been assigned to the Calthion, though here again the affinities are somewhat ill-defined and further sampling is needed to relate this vegetation to grassier fen-meadows.
