Carbon stocks in riparian forests in the Amazonia-Cerrado transition over 15 years: Effects of restoration methods and edaphoclimatic factors.

Ecological restoration is critical to counteract land degradation and mitigate climate change. Tropical forest restoration offers major carbon sequestration potential due to rapid biomass accumulation and high storage capacity. However, the long-term carbon sequestration efficacy of different methods remains poorly understood in large-scale restoration projects. We investigated the recovery of aboveground biomass (AGB) and soil organic carbon (SOC) over a 15-year chronosequence in the Amazonia-Cerrado transition, comparing direct seeding techniques (broadcast, holes and rows) against seedling planting and natural regeneration. Using linear mixed-effects models, we assessed how restoration age and edaphoclimatic variables influenced these carbon pools. Our results show that AGB accumulation was primarily driven by the restoration age and soil fertility, with row-seeding significantly outperforming other seeding techniques and seedling plantations. This success was linked to the mechanical precision of row-seeding, which favored longer-lived pioneer species with specific seed traits. In contrast, SOC stocks remained stable across the chronosequence and were controlled by edaphoclimatic factors rather than restoration methods, underscoring the decoupling of aboveground biomass accumulation from belowground carbon dynamics. We conclude that direct seeding is a highly cost-effective method for carbon-focused restoration, but the specific technique and soil fertility significantly influenced the outcome. To maximize sequestration at scale, future efforts should prioritize soil amelioration, seeding precision, and species selection.