Phytostabilization Ability of Baccharis linearis and Its Relation to Properties of a Tailings-Derived Technosol

Spontaneous colonization of mine tailing dams by plants is a potential tool for phytostabilization of such reservoirs. However, the physical and chemical properties of each mine tailings deposit determine the success of natural plant establishment. The plant Baccharis linearis is the main native nanophanerophyte species (evergreen sclerophyllous shrub) that naturally colonizes abandoned copper tailings dams in arid to semiarid north-central Chile. This study compare growth of B. linearis against the physical and chemical properties of a Technosol derived from copper mine tailings. Five sites inside the deposit were selected based on B. linearis vegetation density (VD), at two soil sampling depths under the canopy of adult individuals. Physical and chemical properties of tailings samples and nutrient concentrations in tailings and plants were each determined. Some morphological features of the plants (roots and aerial parts) were also quantified. There were significant differences in soil available water capacity (AW) and relative density (Rd) at different VD. Sites with low AW and high Rd had lower nutrient concentrations and higher Zn content in tailings, decreased infection by arbuscular mycorrhizal fungi, and increased fine root abundance and root hair length in individual plants. In contrast, higher AW, which was positively correlated with fine particles and organic matter content, had a positive effect on vegetation coverage, increased N and P contents in tailings, and increased N contents in leaf tissues, even when available N and P levels in tailings were low. Multiple constraints, such as low AW, N, P, and B contents and high Zn concentrations in the tailings restricted vegetation coverage, but no phenotypic differences were observed between individuals. Thus, in order to promote dense coverage by B. linearis, water retention in these tailings must be improved by increasing colloidal particles (organic and/or inorganic) contents, which have a positive effect on colonization by this species.