Calcium content and high calcium adaptation of plants in karst areas of southwestern Hunan, China.

Rocky desertification is a major ecological problem of land degradation in karst areas. Its high soil calcium (Ca²⁺) content has become an important environmental factor which can affect the restoration of vegetation in such rocky desertification areas. Consequently, the screening of plant species, which can adapt to soils high Ca²⁺ environment, is a critical step for vegetation restoration. However, the Ca²⁺ dynamics of plants and soil are not well understood. In this study, three different grades of rocky desertification samples areas (LRD, light rocky desertification; MRD, moderate rocky desertification; IRD, intense rocky desertification) were selected in karst areas of southwestern Hunan, China. Each grade of these samples areas had 3 sample plots in different slop positions, each of which had 4 small quadrats (1 in rocky side areas, 3 in non-rocky side areas). We measured the Ca²⁺ content of leaves, branches and roots from 41 plant species, as well as soil total Ca²⁺ (TCa) and exchange Ca²⁺ (ECa) at depths of 0-15, 15-30 and 30-45 cm under each small quadrat. The results showed that the soil Ca²⁺ content in rocky side areas was significantly higher than that in non-rocky side areas (p < 0.05). The mean soil TCa and ECa content increased gradually along with the grade of rocky desertification, in the order IRD > MRD > LRD. For all plant functional groups, the plant Ca²⁺ content of aboveground parts was significantly higher than that of the underground parts (p < 0.05). The soil ECa content had significant effects on plant Ca²⁺ content of the underground parts, but had no significant effects on plant Ca²⁺ content of the aboveground parts. According to the differences in Ca²⁺ content between the aboveground and underground parts of 17 dominant species (important value, IV > 1) and their correlations with soil ECa content, these 17 species can be divided into three categories: Ca-indifferent plants, high-Ca plants and low-Ca plants. Our results can provide a vital theoretical basis and practical guide for vegetation restoration and ecosystem reconstruction in rocky desertification areas. [ABSTRACT FROM AUTHOR]