Experimental Establishment of New Species from Seed in Callunetum in North-East Scotland

Abstract

The need to develop the grazing and wildlife values of upland range in Scotland because of past degradation has often been stated (e.g. Eggeling 1964; Miles 1973a, b). However, planning the development and management of range requires a knowledge of the potential of different sites. The concept of site potential is well-established, although it has been used in various senses (Dyksterhuis 1949; Klingebiel & Montgomery 1961; Klemmedson & Murray 1963). In this paper, site potential is used in the sense of floristic or vegetational potential, i.e. the variety of species and alternative vegetation types that a particular site could support (Miles 1973b). Complete specification of the vegetational potential of a site is clearly unrealistic and it is practicable to describe only a few potential noda to indicate the amplitude of site potential. Foresters know quite well what tree species particular kinds of site can support. However, since the pioneering studies of Bonnier (1890, 1920) and MacDougal (1921), ecologists have done little experimental work of this nature. As a result, little is known of the potential of most sites for supporting different herbaceous and dwarf shrub communities other than those observed in existing successions. The few experimental studies on the establishment of new species in Callunetum have been either by foresters dealing with trees and shrubs (Zehetmayr 1954, 1960; Dimbleby 1958; McVean 1966) or by agronomists dealing only with a few grasses and legumes (Hughes & Nicholson 1962; Jones 1967). The aim of this study was to examine experimentally the establishment from seed of 107 species, of varied growth form and ecological tolerance, on bared ground at three sites bearing Callunetum in north-east Scotland. Most of the species did not occur in the existing vegetation and a large proportion probably never occurred at the sites in the past. It was hoped that the results would indicate the extent to which other species and types of vegetation could grow at the sites as additions or alternatives to those already present. The study was an exploratory approach towards defining vegetational potential rather than an attempt to establish particular species. A previous study (Miles 1973b) demonstrated the stability and successional poverty of these sites, and suggested it was caused partly by lack of seed of different species, and partly by soil infertility. A third paper will describe the results of experimental interference with the structure of Callunetum.