Nurse effect and herbivory exclusion facilitate plant colonization in abandoned mine tailings storage facilities in north-central Chile

Abstract

Positive interactions among plants, such as the nurse effect, can attenuate environmental stress (e.g., drought) or reduce the intensity of perturbations (e.g., herbivory), thus enhancing the possibility of regeneration in natural systems. This study analyses the potential use of nurse plants for restoring artificial environments, such as mine hard-rock dumps. We evaluated seedling recruitment and survival in open areas and beneath the canopy of nurse shrubs, with and without grazing exclusion, on an abandoned copper tailings storage facility in north-central Chile. The nurse species was Baccharis linearis (Asteraceae), and seedling species were B. linearis, Haplopappus parvifolius (Asteraceae), Schismus arabicus (Poaceae), and several forb/grass taxa. A field survey showed that seedlings of all species were more abundant beneath the Baccharis shrub canopy coverage than in the open spaces between shrubs. Only Baccharis seedlings produced a significant difference. We found a decreasing sequence of seedling survival under the following conditions: beneath the Baccharis canopy with herbivore exclusion, beneath the canopy without exclusion, in the open field with exclusion, and finally, in the open field without exclusion. Substrates beneath shrubs had higher P and K levels at depths < 10 cm than substrates in open areas. Water content, substrate compaction, and plant diversity did not differ between microenvironments. Our results demonstrate the importance of both the nurse effect and herbivore exclusion in enhancing seedling establishment on abandoned mine tailings storage facilities in semi-arid north-central Chile. Thus shedding light upon the ecological restoration possibilities in such disturbed environments.