Plant mineral nutrition on ultramafic rocks of New Caledonia

Abstract

ABSTRACT In New Caledonia, the environmental heterogeneity on ultramafic rocks is a major driver of plant diversity. Here, the foliar mineral composition of numerous species was analysed to (1) explore plant mineral nutrition in different environments on ultramafic rocks, and (2) characterise the nutritional behaviour of species strictly growing on these rocks. A total of 4,600 samples were analysed, corresponding to more than 500 species, including 350 from maquis, i.e. about a third of the species inventoried on ultramafic rocks. Samples were collected mainly from the Boulinda Massif and the Grand Massif du Sud, where almost all the maquis species were analysed, and from the Koniambo and Tiebaghi massifs. The results confirm the very low P and low N, K and Ca availability for plants in all ultramafic environments. The low stocks in major elements, except for Mg, are undoubtedly one of the main causes, or at least the most constant cause, of the general poor fertility of soils on ultramafic rocks in New Caledonia. The mineral composition of the leaf tissue of species growing on ultramafic rocks reflects, to some extent, the mineral imbalance of the soils. It is particularly marked by abnormal high foliar concentration in trace elements (Ni, Mn, Cr, Co). Ni and Mn accumulator species are recorded in many families. The mineral element concentrations are significantly different from one species to another and reflect the high specificity of mineral nutrition, and the adaptation to specific mineral conditions in different types of environments on ultramafic rocks.