Plant distribution and its relationship to extractable boron in naturally-occurring high boron soils in Turkey

Naturally Occurring borax reserves exist in dry climates in several parts of the world. Soils associated with these reserves are high in boron (B) and may host distinctive vegetation with high levels of B toxicity tolerance. In this study, three zones of vegetation with increasing distances from the edge of a boron mine were defined at the Kirka Borax Production Plant (Eskisehir, Turkey), one of the richest borax reserves in the world. The zone with the lowest B concentrations (0.1-2 mg/kg) had the highest species diversity (84 species). Species diversity was much lower (28 species) in the intermediate zone that had moderate B levels (10 mg/kg). Only Catapodium rigidum (L.) C. E. Hubbard ex Dony subsp. rigidum var. rigidum (Poaceae) and Gypsophylla perfoliata L. var. perfoliata (Caryophyllaceae) showed resistance to B levels in excess of the accepted toxic levels; these species had the ability to develop and spread in the zone that had the highest B concentration (35 mg/kg).