Winkelbury Hill is noted for its species rich, calcicolous grassland – an important habitat because of the rapid decline in unimproved grassland that continues today despite the advances made in conservation of our wildlife in the last centuary. In part, the survival here is due to the earthworks because it is clear that the quality of the turf on the bank is very much better than on the flatter ground. Walking around the monument last Sunday, my impression is that if you were to choose a metre square in the centre, you might find about ten species and most of the vegetation would be coarse grass, such as cock’s foot (Dactylis glomerata). On the earthworks, that metre square would enclose over twenty species and all would be smaller species amongst finer grasses. Back in the summer there would have been a lot more colour on the banks – rockrose, scabious, thyme, salad burnet, orchids and fellwort, for instance – whereas very few flowers would be visible in the centre.
The reasons for these differences are partly due to management and partly the spoils. It is likely that the central part of the monument has been ploughed and reseeded at some time. The soil is probably deeper and less prone to drought in the summer. The better conditions allow the more vigorous species to dominate the sward. This in turn means that cattle and horses spend more time grazing and more dung is deposited. The earthworks were constructed of dug chalk and when new there would be no soil present. Over time, a thin soil (called a rendzina) develops, as it has done on the steep natural slopes of the hill. It is well drained and has little capacity to retain moisture. There are few nutrients available for plants and so the species present are those that are best at seeking out the minerals and can tolerate dry periods. The coarse, fast growing species require a more fertile substrate and are very poor competitors when conditions are tough. With the bullies disadvantaged a much greater plant diversity can develop, and as a consequence, more butterflies, invertebrates and colour.
The species list for the day is from casual observation (I was trying to concentrate on the archaeology) and at a time of year when few plants are flowering or in prime condition. I am sure there are over a hundred species on the site.
Winklebury plant list 25/10/2015
Author: Robin Walls (Project Volunteer)