An interpretation of machair vegetation

Abstract

Synopsis The distinctive ecological elements of the machair environment, calcareous sand and an oceanic climate, which combine to give a lime-rich but unstable habitat, in which machair vegetation develops, are discussed initially. A number of different studies employing both phytosociological and ecological approaches, and drawing data from machairs in the Uists, Monach Islands and South Harris, are summarized. Based upon these, the main characteristics of machair vegetation and its key ecological relationships are described. Finally a model of machair vegetation is advanced in which two distinct types of vegetation, ‘dune’ and ‘pasture’ are recognized, and patterns of vegetation development are explained by means of ‘phases’ and ‘sequences’, terms applied to describe relative location of types of vegetation in both time and space.