Heath creation through the establishment of Calluna vulgaris (L.) Hull on ex-arable land in north-east Scotland
The declining area of heathland in north-west Europe is causing widespread concern amongst conservationists. The aim of the experiments described in this thesis was to investigate methods of heath creation by establishing the dwarf shrub, Calluna vulgaris (L.) Hull, on the ex-arable land. Arable land, surplus to requirement and available through set-aside schemes, could be used to expand or join together small pockets of remnant heath. Field experiments were designed to test various methods of introducing Calluna, but, in all cases, it failed to persist and spread after introduction. The most promising method of introduction was to transplant young plants. The conditions at the field site, in arable production immediately prior to the experiments being set up, were such that Calluna was unable to establish dominance. High residual soil fertility combined with a large weed seed bank produced a dense cover of vegetation in which Calluna did not persist. Pot experiments were carried out to determine whether soil amendments might make the creation of heath more feasible on ex-arable sites. Most amendments reduced the dry matter production of the weed species tested compared to the control treatment (un-amended field soil). One treatment, elemental sulphur, significantly reduced the growth of a major weed species (Trifolium repens) at very low application rates, whilst Calluna grew well on the amended soil. Elemental sulphur lowers soil pH and therefore reduces the availability of most plant nutrients and increases the solubility of some metals. When tested in the field, high rates of sulphur significantly increased the survival of Calluna transplants. The author suggests that soil modification with an acidifying agent is the key to heath creation on agriculturally-improved soils. Vegetation management, such as the use of herbicides may also have a part to play, although once soil conditions are suitable this management would be reduced very much to a secondary role.