Resumo A capacidade de capturar gás carbônico (CO2) da atmosfera e um dos vários serviços ecossistêmicos oferecidos pelas florestas e a espécie Hevea guianensis Aubl. se destaca como potencial sumidouro de CO2. O objetivo deste trabalho foi estimar o potencial de créditos de carbono na madeira de seringueiras em plantios abandonados na Floresta Nacional do Tapajós. Nos anos de 2013 e 2018 foram realizados inventários 100 %, em que se registrou a circunferência e altura das arvores. Calculou-se o carbono fixo (MgC ha-1), o carbono equivalente (CO2 (eq) ha-1) e foi realizada a conversão em créditos por hectare (US$ ha-1), a partir do Sistema Europeu de Negociação de CO2 eq. Em 2013 foram inventariadas 2.965 seringueiras e, em 2018, foram inventariadas 2.927. Apesar da morte de algumas arvores no intervalo de 5 anos, foi estimado um total de 72,3103 MgC ha-1, em 2013, e 73,3708 MgC. ha-1, em 2018, resultando em um incremento corrente anual de 0,2121 MgC.ha-1, reduzindo 0,7777 CO2(eq) ha-1 ano-1, o que possibilitaria uma receita anual de US$ 515,90. Dessa forma, concluiu-se que o potencial de geração de créditos de carbono identificado nos seringais pode agregar valor a floresta, resultando em uma adicional idade a renda da população tradicional, tornando-se um diferencial para a conservação da Unidade de Conservação.

Abstract The capacity to capture carbon dioxide (CO2) from the atmosphere is one of several ecosystem services offered by forests and the species Hevea guianensis Aubl. stands out as a potential CO2 sink. This study aimed to estimate the carbon credit potential in the wood of rubber trees in abandoned plantings in Tapajos National Forest. In the years 2013 and 2018, 100 % inventories were carried out, in which the circumference and height of the trees were registered. The fixed carbon (MgC ha-1), the equivalent carbon (CO2(eq) ha-1) was calculated and converted into credits per hectare (US$ ha-1) from the European System for the CO2. In 2013, 2,965 rubber trees were registered, and in 2018, 2,927 were inventoried. Despite the death of some trees in the range of 5 years, it was estimated a total of 72.3103 MgC ha-1 in 2013, and 73.3708 MgC ha-1 in 2018, resulting in a current annual increase of 0.2121 MgC ha-1, reducing 0.7777 CO2(eq) ha-1 ano-1, which would make possible an annual revenue of US$ 515.90. Thus, it was concluded that the potential for generating carbon credits identified in the rubber plantations could add value to the forest, resulting in an addition to the income of the traditional population, making it a differential for the conservation of the Conservation Unit.

ABSTRACT The objective of this study was to analyze the adaptive cluster sampling (ACS), simple random sampling (SRS) and systematic sampling (SS) processes to obtain the number of ha-1 trees of Carapa guianensis Aubl. in the Amazon. The data were obtained through 100% inventory and sampling simulations, considering a DBH ≥ 25 cm, a sampling intensity of 4%, a maximum error of 10% and plots of 0.09, 0.16 and 0.25 ha. The last two sizes were only used to analyze their effect on the ACS estimators. The processes were evaluated for accuracy, precision (E%) and confidence interval (CI), while the mean ha-1 of the processes were compared with that of the 100% inventory by the Z test. The ACS process showed no significant difference between its average ha-1 trees and the 100% inventory, and it was also the most accurate and the only one whose CI was true. However, it presented a final sample intensity 3.6 times greater than the simple and systematic random samplings, in addition to E% above 10%, which makes it unacceptable, legally, and economically unfeasible. The other processes had densities significantly higher than the 100% inventory, with sample intensities lower than ACS and E% lower than 10%, making them legally viable. The use of larger plots in the ACS implies larger clusters and a greater tendency to underestimate the number of trees, resulting in larger sample errors and less accuracy.