Serpentine soils

In addition to anthropogenic pollution, some serpentine soils derived from Fe and Mg-rich ultramafic rocks are enriched in Ni, Cr and Co. In North America, ultramafic rocks form two discontinuous bands along the east and west side of the continent. The largest area of ultramafic terrain is in the Klamath Mountains province of northern California and southern Oregon (Lee et al., 2001). Serpentinite is a metamorphic rock formed from low... 

Pal A, Ghosh S, Paul AK (2006) Biosorption of cobalt by fungi from serpentine soil of Andanan. Bioresource Technol 97 1253-1258... 

Chromium is beneficial but not essential to growth in higher plants. Residues in plants seldom exceed a few mg/kg, except in plants living on infertile serpentine soils containing high chromium... 

Lichen, Compylium polyanum whole from serpentine soils... 

One of the features of areas of the world that have had naturally occurring toxic soils for many thousands or millions of years is that these soils often support species that are found nowhere else so-called edaphic endemics (Kruckeberg and Rabinowitz, 1985). Examples of such soils include the Great Dyke in Zimbabwe and serpentine soils in many areas of the world. It has been argued on many occasions (eg, Proctor and Woodell, 1975 Kruckeberg, 1984) that the phenomenon of metal tolerance provides a model of how these species may have started on the evolutionary route that finally led to full edaphic endemism. 

Most hyperaccumulators are themselves endemic to the type of soil in which they are found. A classical case of this is the Alyssum genus that is widespread in Southern Europe and Asia Minor. Section Odontarrhena of the genus contains about 50 taxa that are endemic to ultramafic (serpentine) soils (Brooks, 1887 Brooks et al., 1979). Due to their endemism they invariably indicate the presence of serpentine soils and thereby act as geobotanical indicators of potential mineralisation in the substrate. Another example is the presence of the Zn hyperaccumulators Viola calaminaria and Thlaspi calaminare confined to Zn deposits in Western Germany and Eastern Belgium. 

Serpentine soils have high levels of heavy metals (Ni, Co, Cr), and low levels of important plant nutrients (P, Ca, N). Because of these inhospitable conditions, serpentine soils support a specialized flora, including such plant species as the nickel hyperaccumulator Alyssum bertolonii. In a study that examined bacterial communities at various distances from A. bertolonii roots in different serpentine areas, it was found that the bacterial communities possessed high genetic diversity... 

Mengoni, A., Grassi, E., Barzanti, R., Biondi, E. G., Gonnelli, C., Kim, C. K., and Bazzicalupo, M. (2004). Genetic diversity of bacterial communities of serpentine soil and of rhizosphere of the nickel-hyperaccumulator plant Alyssum bertolonii. Microb. Ecol. 48, 209-217. 

Wenzel, W.W., Bnnkowski, M., Puschenreiter, M., Horak, O., 2003. Rhizosphere characteristics of indigenonsly growing nickel hyperaccumulator and excinder plants on serpentine soil. Environ. PoU. 123, 131-138. 

Himmelbauer, M.L., Puschemeiter, M., Schnepf, A., Loiskandl, W., Wenzel, W.W., 2005. Root morphology of Thlaspi goesingense Halacsy grown on a serpentine soil. J. Plant Nutr. Sod Sci. 168 138-144. 

Certain plants grown on serpentine soils containing 1000-50,000 mg Cr/kg dry weight (DW) may contain 10.0-100.0 mg Cr g DW -levels that may be toxic to wildlife, although no reports of this phenomenon are known. Most plant and invertebrate species die before accumulating amounts of chromium that are toxic to predators. Some species of terrestrial plants have been proposed for the removal of chromate from wastewaters. Terrestrial plants, such as wheat (Triticum aestivum), accumulate the greatest amount of chromium under conditions of sulfate deficiency or deprivation. Because... 

Nickel-tolerant or accumulator species of plants are likely to be found only on nickel-rich soils. Hyperaccumulator species usually grow on relatively infertile nickel-rich serpentine soils and contain more than 10,000.0 mg Ni/kg DW. Leaves from some genera of nickel hyperaccumulator plants, including Alyssum, Homalium, and Hybanthus, growing on soils derived from volcanic rocks, which are rich in ifickel, accumulate nickel to concentrations of 120,000.0 mg kg DW. Nickel is bound as a citrate complex in hyperaccumulator plants from New Caledonia however, nickel accumulator plants from other locations do not contain unusually high levels of citrate, and nickel is not present as a citrate complex but as a carboxylic acid complex. 

Toxic heavy metal concentrations can have natural reasons naturally heavy metal-rich soils are found in various locations around the world where metal ores come to the surface and decay due to weathering. A few examples of such locations are the Katangan copper belt in Kongo and Zaire [3,4], nickel-rich serpentine soils in Cuba [5], North America [6] as well as Sulawesi and New Caledonia [7] and some zinc and cadmium sites in Europe [8]. While these locations are usually not regarded as agriculturally relevant, and usually no attempts are made to detoxify them (as it would be futile), the plants growing on them still have to detoxify the stream of nutrients they take up from such soils. 

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