Low predictability in aboveground biomass accumulation in Brazilian semi‐deciduous seasonal Atlantic Forest restoration sites

Abstract

There are high expectations about the role of active reforestation in mitigating climate change, by means of carbon sequestration and storage, fueling the carbon credit market. Carbon credits are calculated in advance based on the number of planted trees or, at best, the expected size and wood density of planted trees. However, the contribution of tropical reforestations with native species for carbon sequestration in the long term is still unclear, since most sites being monitored are less than 20 years old, thus limiting the ability to make forecasts of what is a dynamic, multifactor restoration outcome. We used a chronosequence to analyze aboveground biomass (AGB) accumulation in 30 Brazilian semi‐deciduous seasonal Atlantic Forest restoration sites sharing the same climate, soil type, and restoration technique. We evaluated the entire age range of 1–19 years, and three age intervals, 1–3 years, 4–8 years, and over 9 years. AGB, basal area, and tree density increased considering all ages (1–19 years). Our results showed, however, that the AGB, tree density, and basal area can increase linearly from 1 to 3 years but present no significant trend after 4 years. Adjusted model r2 values decreased with time, suggesting that the controlled effects of active restoration are quickly replaced by other natural, uncontrolled, and, to some extent, unknown factors. Although continued efforts are needed to make more realistic predictions of long‐term carbon stocks based on tree planting, high levels of biomass estimates for time intervals as short as 20 years may never be achieved.