A new approach for restoring tropical dry forests: Using local shrubs as nurse plants to improve the recruitment of Tara spinosa in Lomas de Atiquipa (Andean Region, Perú)

Abstract

Tropical dry forests are among the most threatened ecosystems worldwide, with severe deforestation and regeneration problems compounded by an increasing climate change threat. Lomas de Atiquipa in the Peruvian–Chilean Coastal Desert (Atacama Desert) comprises one of these formations, mainly dominated by the Tara tree (Tara spinosa), which is a Neotropical legume tree with high ecological and commercial value. However, approximately 80% of the original area has been reduced mainly by deforestation. An ecological restoration experience was demonstrated in this study by investigating the use of thorny shrubs as nurse plants to promote forest regeneration. This approach is based on the idea of facilitation between plants and can be a suitable “nature-based solution” to decrease reforestation costs. Accordingly, 170 seedlings and 128 seeds of Tara were installed in two contrasting environments: 1) under the cover of the nurse plant and 2) outside the vegetation cover. Survival rates of the seedlings and germinated seeds were periodically monitored from August to December. We also measured microclimatic conditions outside and under the canopy of the nurse plant, including temperature (°C), relative humidity (%), soil moisture (v:v), and illumination (lux), to assess the recruitment niche. Our results showed the highest seedling survival rates at the end of the experiment under the canopy of the nurse plant (22.4%) vs. outside (8.2%). This could be linked to the better performance of juvenile plants owing to the nursing effect of shrubs, as we detected a significant reduction in the extreme environmental conditions under the canopy of the nurse plant, with the lowest temperatures and highest humidity, as well as a significant reduction in light incidence. Our findings suggest that using local shrubs as nurse plants is a promising method for restoring Tara in the Lomas ecosystem because it reduces the stress of direct insolation and high temperatures and reduces the cost and effort of hand watering the seedlings after planting.