Studies on the Calcicole-Calcifuge Habit: II. The Influence of Calcium on the Growth and Establishment of Four Species in Soil and Sand Cultures

Evidence which has been presented earlier (Jefferies & Willis 1964) indicates that the calcifuge species Juncus quarrosus L. and Nardus stricta L. are plants possessing an extremely narrow distribution range in respect of levels of exchangeable soil nutrients, especially regarding calcium. Sieglingia decumbens (L.) Bernh. is tolerant of a much wider range, whereas Origanum vulgare L. isrestricted to soils rich in exchangeable calcium. An attempt has been made, using culture techniques, to assess to what extent he distribution patterns of these plants are determined by the availability of nutrients in the soil. Plants of the four species have been grown in different types of soil in order to study their ability to become established in soils from which they are absent under natural conditions. The plants also have been grown in sand cultures to which mineral solutions have been added such that the nutritional status of the cultures probably approximated to conditions found in natural habitats. As the availability of calcium differed considerably in the soils which have been analysed, particular attention has been given to the effect of calcium concentration in relation to the concentration of the other nutrients on the establishment and growth of these species.