Characteristics of nickel accumulation in native plants growing in ultramafic rock areas in Hokkaido

Nickel accumulation in the native plants growing in ultramafic rock areas i n Hokkaido, Japan was studied. The mean soil pH ranged from 6.1 to 8.0. The content of exchangeable Ni in the son was only 3 to 13 mg kg(-1). The lowe st content of total Ni was 1.3 g kg(-1), and the highest value was 2.6 g kg (-1) Thlaspi japonicum was found to accumulate as much as 1,045 mg Ni (kg d ry wt)(-1), although this species is not an ultramafic plant. Five other sp ecies, Allium schoenoprasum var, sibutuense, Viola yubariana (endemic speci es on Mt. Yupari), Lagotis takedana (endemic species on Mt. Yupari), Viola sacchalinensis var. alpina, and Draba japonica were identified as strong Ni accumulators based on measurements using dried herbarium specimens. The Ni content in ultramafic plants exceeded 50 mg (kg dry wt)(-1) in about half of the native plants growing in ultramafic rock areas. The Ni content of dr ied plants of A Ilium schoenoprasum var. sibutuense was 234 mg (kg dry wt)( -1), while that of Allium maximowiczii was only 19 mg (kg dry wt)(-1). Alth ough Deschampsia caespitosa var, levis, Japonolirion osense var, saitoi, Be tula apoiensis, and Primula hidakana are ultramafic plants, the Ni content in these plants was less than 10 mg (kg dry wt)(-1). In all the examined ul tramafic plant species, the Ni content in plants plotted against the exchan geable Ni content in soil was represented by a regression curve and not a s traight line. The Ni content in plants increased markedly with increasing e xchangeable Ni content in soil in a low content range, but slightly in a hi gh content range. In common plants, a similar correlation was observed only in one species, a linear correlation in three species and no correlation i n two species.