England's green and pleasant land; a land of grass covered hillsides and lush lowland meadows where cattle graze peacefully. What could be more natural? In fact our grasslands are not at all natural, they are man-made environments and those that exist today only do so through continuing human intervention. That may seem hard to believe when wandering across chalk grassland in summer looking at the diverse array of flowers and the stunning variety of butterflies, bees and hoverflies that visit those flowers.
After the ice receded at the end of the last ice age the bare ground exposed gradually regenerated into woodland known as the 'wild wood'. During the bronze and iron ages some 4,000 years ago our predecessors started making tools that enabled them to clear trees and open up the ground for early farming and stock keeping (just as we still do today in the rain forests of South America and Asia!). Once cleared, grass colonised the cleared areas and livestock were grazed on it and that kept the growth of scrub and trees at bay. To feed cattle during the winter months the grass was cut, dried and stored as hay which also had the effect of stopping the natural cycle of regeneration. That constant annual cycle for centuries kept our grasslands exactly that, grassy and full of flowers too.
Sadly, the recent past has seen much of our grassland lost to agricultural 'improvement'. Much has been ploughed and planted with cereals with herbicides used to poison the naturally occurring flowers that make effective harvesting more difficult. The grassland that remains tends now to be in fragments and in fairly inaccessible places where farm machinery cannot venture. Fortunately, much of it now has protection as nature reserves. It still requires management, however, which is why you will often encounter grazing animals (and conservation work parties) on nature reserves; they are a 'natural' part of the process.
There are various types of grassland that result from differing soil types, moisture levels and management techniques. In Dorset there seem to be five that occur most:
- Acid: grassland that occurs where heather and gorse have either failed to get established or where grazing continue to keep the heather and gorse at bay
- Calcareous: Dorset has some fine areas of calcareous rocks and soils from the limestone of the Jurassic coast to the chalk of the north Dorset ridgeway.
- Neutral: in between acid and calcareous soils one finds neutral soils, often at low levels on clay soils
- Rush: in areas where the soil is generally wet (or damp) by rivers grasses can be joined by rushes and sedges to make a different sort of pasture
- Flood: flood meadows are found towards the lower reaches of the main rivers as they near the sea and are grasslands that are often flooded in winter (sometimes through control by sluice gates) that makes for fertile soil and rich pasture suitable for cattle grazing
Each of these environments differ in the range of plants that will be found. Some plant species are tolerant of soil chemistry variations and occur across several habitat types but others are quite specific in their needs and are indicators of the conditions under foot. This is particularly true of chalk and limestone grassland that has a number of flowers that will not grow elsewhere. This is what makes calcareous grassland unique and priceless.