Influence of different tree species on autotrophic and heterotrophic soil respiration in a mined area under reclamation

Planting trees is one of the most effective activities in recovering soil organic carbon (SOC) stocks of degraded areas, but we still lack information on how different tree species can influence soil respiration, one of the main sources of carbon dioxide (CO2) to the atmosphere. This study aimed to explore the influence of different tree species on the autotrophic and heterotrophic components of the total soil respiration in a bauxite mining area under reclamation. We analyzed the soil CO2 efflux under five treatments: (i) monoculture of clonal Eucalyptus; (ii) monoculture of Anadenanthera peregrina (L.); (iii) a mixed plantation of 16 native tree species; (iv) a mined area without vegetation cover as a control site; and (v) a natural forest cover as a reference site. This design allowed exploring the soil CO2 dynamics in a gradient of recovery, from a degraded area to natural vegetation. Additionally, we measured soil temperature, moisture, and soil attributes. Soil CO2 efflux increased with increasing tree species cover in the rainy months. There was no significant change in CO2 efflux among the tree species. However, heterotrophic soil respiration contributed to 64% of total soil CO2 efflux and was associated with litter decomposition. Among the abiotic variables, increases in soil moisture had the most influence on CO2 efflux. Therefore, these results help to understand the factors that underpin the loss of SOC and show that afforestation with different tree species can recovery the soil biological activity by improving litter deposition and is a promising way to restore soil quality in degraded areas.