The contribution of small trees to carbon stocks along a recovery gradient in the Amazonia
Luiz Antonio Soares Cardoso, Fernando Elias, Eduardo Queiroz Marques, Lorrayne Aparecida Gonçalves, Joice Nunes Ferreira, Erika Berenguer, Ima Célia Guimarães Vieira, Jos Barlow, Izildinha de Souza Miranda, Marcelo Tabarelli, Rodrigo Oliveira do Nascimento, Luiz Eduardo Oliveira e Cruz de Aragão, Gustavo Schwartz, Divino Vicente SilvérioAbstract
Most ecological knowledge about carbon recovery during natural regeneration in tropical regions has focused on individuals exceeding 10 cm in diameter. However, the contribution of smaller individuals to aboveground carbon (AGC) across successional gradients remains poorly quantified, despite their potentially substantial role during early stages of forest regeneration. While remote sensing technologies provide powerful tools for large‐scale carbon monitoring, their effectiveness in capturing contributions from different size classes across successional gradients requires validation with detailed field data. To understand the role of individuals smaller than 10 cm in diameter in carbon recovery, we conducted two sets of analyses. First, we compared the contribution of small and large individuals along the successional gradient using 126 plots (0.25 ha each) distributed across 16 municipalities in the Eastern Amazon, Brazil. Second, we evaluated the sensitivity of remote sensing‐based carbon estimates from the European Space Agency Climate Change Initiative (ESA CCI‐AGB) to capture these variations across size classes and successional gradients. Smaller individuals played a key role in carbon stocks, storing up to 75% of the total carbon in early succession. This contribution declined to 50% after 10 years and to 18% after 25 years. At 10 years of regeneration, the mean total AGC stock was 24.3 ± 2.3 Mg C ha −1 (mean ± SE), increasing to 41.5 ± 2.0 Mg C ha −1 at 25 years, reflecting the progression of ecological succession. The ESA CCI‐AGB estimates tended to systematically overestimate AGC stocks, with a mean error of approximately 39 Mg C ha −1 . Convergence with field‐measured stocks was 33% when all individuals were included, compared with 29% when only large individuals were considered. Our findings highlight the crucial role of small individuals in AGC stocks, emphasizing the need to include them in carbon recovery estimates, especially in younger secondary forests that make up most of the Amazonian regrowth.