Leaching Losses of Minerals from Leaves of Trees in Montane Forest in Kenya

Abstract

The functions of xeromorphic features in plants of dry forests are fairly well understood but the occurrence of some of the same features, e.g. small leaves and thick cuticles, in moist forests is not easily explained. The uniformity of leaf type in Tropical Lowland Rain forests has long been appreciated. Richards (1952) observed that the texture of the leaves is often leathery, the upper surface generally glabrous and polished, with any tomentum confined to the lower surface. The margin is usually entire or finely serrate, leading to an acumen or 'drip-tip'. Richards (1952) also summarized the evidence that leaf size decreases with increase in altitude. The hard texture of the leaves is maintained and the leaves of Tropical Montane forests may appear markedly xeromorphic. It is possible that the thick cuticle of such leaves has an important role in minimizing loss of nutrients by leaching. The significance of foliar leaching has been recognized by ecologists in many studies on mineral cycling. The literature has been reviewed recently by Tukey (1970) and Jordan & Kline (1972). The present study was designed to provide information on foliar leaching phenomena of species restricted to wet or relatively dry climates (given uniform leaching conditions) and on ecotypic variation in leaching properties of species growing in both wet and relatively dry climates. Very little is known about the foliar nutrient contents of the plants in the vegetation types concerned and it was necessary first to discover the levels of the common nutrients in the species investigated.