title: The15N/14N ratios of plants in South Africa and Namibia: relationship to climate and coastal/saline environments.
abstract: Data are presented for the15N/14N ratios of 140 indigenous terrestrial plants from a wide variety of natural habitats in South Africa and Namibia. Over much of the area, from high-rainfall mountains to arid deserts, the δ15N values of plants lie typically in the range -1 to +6‰; with no evident differences between C3plants and C4grasses. There is a slight correlation between δ15N and aridity, but this is less marked than the correlation between the δ15N values of animal bones and aridity. At coastal or saline sites, however, the mean δ15N values for plants are higher than those at nearby inland or non-saline sites-e.g.: arid Namib coast (10‰ higher than inland Namib); wet Natal beach (5‰ higher than inland Natal); saline soils 500 km from coast (4‰ higher than non-saline soils). High values were also found at one site where there were no marked coastal or saline influences. These environmental effects on the isotopic composition of plants will extend upwards to the animals and humans they support. They therefore have important consequences for the use of nitrogen isotope data in the study of the dietary habits and trophic structures of modern and prehistoric communities.
authors.affiliation: Natural Isotopes Division, National Physical Research Laboratory, CSIR, PO Box 395, 0001, Pretoria, South Africa.
authors.forename: T H E
authors.initials: TH
authors.lastname: Heaton
keywords: 15N/14N ratios; Climate; Coastal; Plants; Saline