ABSTRACT
Ultramafi c soils, also known as “serpentine soils” in literature, are a weathered product from ultramafi c bedrock that covers less than 1% of the earth’s surface (Coleman and Jove 1992). These soils are characterized by high concentrations of iron oxides (up to 85% w/w), unbalanced calcium-
1IRD, UR040 LSTM, Centre IRD, BPA5, Promenade Roger Laroque, 98848 Nouméa Cedex, Nouvelle-Calédonie. 2Institut Agronomique néo-Calédonien (IAC), Axe 2 ‘Diversités biologique et fonctionnelle des écosystèmes terrestres’, Nouméa IRD research centre, BP18239, 98857 Nouméa, NouvelleCalédonie. 3CIRAD, UMR LSTM, TA A-82 ⁄ J Campus International de Baillarguet, 34398 Montpellier Cedex 5 France. 4Université Montpellier 2, UMR28 LSTM, TA A-82 ⁄ J Campus International deBaillarguet, 34398 Montpellier Cedex 5, France. *Corresponding author: philippe.jourand@ird.fr
to-magnesium ratio (up to 1/30 that consequently may infl uence both Mg and Ca plant nutrition), and the presence of various heavy metals at high concentrations, such as chromium, cobalt, manganese and nickel, all of which are mostly toxic for many plants (Brooks 1987). They are also extremely defi cient in elements that are essential for plant nutrition, including nitrogen, phosphorus and potassium (Brooks 1987, Chiarucci and Baker 2007). Previous studies have shown that ultramafi c soils are characterized by a high biological diversity of plants as described in Proctor (2003) and micro organisms that use various mechanisms to cope with the extreme edaphic conditions, in particular adaptation to toxic heavy metals (Brady et al. 2005, Kazakou et al. 2008, Rajkumar et al. 2009). Recently, major data about the ecological traits of ultramafi c soils have been reviewed to propose these soils as a model system in ecology and conservation,mostly because of their high plant diversity (Harrisson and Rajakaruna 2011).
