Growth of calcicole and calcifuge Agulhas Plain Proteaceae on contrasting soil types, under glasshouse conditions

Abstract

Seven species of Proteaceae — Protea compacta, P. obtusifolia, Leucadendron xanthoconus, Ld. meridianum, Leucospermum cordifolium, Ls. truncatum and two populations of Aulax umbellata — from the Agulhas Plain, south-western Cape, were grown in acid sand and neutral limestone sand in pots in a greenhouse. Heights were measured monthly, and after 400 days the plants were harvested and the dry weights of shoots and roots determined. Species normally growing on acid sands showed signs of chlorosis and necrosis when grown on limestone soils, and weights at harvesting were significantly less than for the same species grown on acid sand. Species normally growing on limestone soils were not significantly different in height or weight when grown on either soil type. Mean species root weight in all but one case was more for plants grown on acid sands than on limestone soils. It is suggested that soil type plays the major role in the failure of calcifuge species to establish themselves on limestone soils, but that competition is probably more important in the reverse case. Some suggestions for future research into the physiological tolerances of conspecifics under controlled conditions and field conditions are made.