The meaning and definition of machair

Summary The term machair is commonly applied to the landform/vegetation systems of many dune pasture areas of parts of the Highlands and Islands of Scotland. Definition of such areas appears to rest on locational, morphological, vegetational and soil criteria. Closer examination suggests that the main diagnostic feature is the soil parent material, shell-rich blown sand, which gives rise to high calcium carbonate and pH conditions. Secondary criteria include the morphological maturity of the machair surface, the absence of depositional processes, specific plant associations (notably the elimination of long dune grasses) and a history of grazing and, possibly, cultivation. Machair areas must also be set in a cool, moist maritime climatic regime.