Forest restoration in Southern Amazonia by direct seeding: linking functional traits and carbon accumulation

Key message

Sown species dominate aboveground carbon stocks in restored forests, exhibiting traits associated with an acquisitive strategy (higher SLA and lower WD), distinct from those of primary forests.

Abstract

Tropical forest restoration is crucial for enhancing carbon sequestration and mitigating climate change. To optimize large-scale restoration, it is essential to develop methods, such as direct seeding. Despite its ecological and socio-economic benefits, as well as its cost-effectiveness, direct seeding remains underutilized in Amazonian restoration initiatives. Thus, we evaluate the functional and taxonomic aspects of carbon recovery in 23 riparian forest permanent plots restored by direct seeding in southern Amazonia, approximately 12 years after restoration. We assessed aboveground carbon (AGC) stocks and four functional traits—specific leaf area (SLA), wood density (WD), seed size, and plant height—to analyse the effects of trait variation and species abundance on AGC stocks. We compared these parameters at the plot level between restored and primary forests, and at the species level between sown and naturally regenerating species. We found that restored forests after 12 years have AGC stocks 79% lower than regional primary forests. Five species account for up to 50% of the AGC, with sown species accumulating up to seven times more AGC than regenerated species. Restored forests showed a more acquisitive strategy, with higher SLA and lower WD than primary forests. Carbon stocks positively correlated with species abundance and functional trait variation. In conclusion, our results highlight that after 12 years, restored forests have not yet matched the AGC stocks or functional composition of primary forests, remaining dominated by a few species and functional groups. The dominance of AGC stocks by sown species underscores the effectiveness of direct seeding in facilitating revegetation and the positive relationships between carbon stocks and functional trait variation emphasize their importance as indicators of forest recovery.

Graphical abstract