With CO2 now exceeding 400ppm, strategies for effective carbon sequestration and long-term storage are urgently needed. Deforestation, particularly in the tropics, is one of the largest anthropogenic sources of atmospheric CO2. Nonetheless, tropical forests are still a major sink of CO2, and encouraging forest succession in previously deforested area is considered a promising strategy for sequestering carbon. Invasive grasses are often a major barrier to secondary successful in the tropics. In addition, secondary forests are dominated by fast growing species with low wood density, which stores less carbon than slower growing, late successional species. However, some tropical tree species exhibit both high wood density and fast growth. By using these fast-growing, high wood density species, plantations could be an effective and economically viable strategy for carbon sequestration. In this study, we conducted a controlled experiment using two fast-growing, high wood density native species. We tested whether using these species will significantly enhance aboveground biomass (AGB) compared to control plots in secondary forest in Panama by censusing planted trees and naturally recruiting wood plants.
Six years after planting, the plantation and the paired control plots differed in vegetation structure and biomass. In plantation plots, many planted trees grow to > 15 m tall, which provided shade that suppressed the growth of grasses and aided in recruitment of woody plants. In the control plots, grasses still dominated and fewer recruits were present. As a result, the plantation plots had substantially higher AGB compared to control plots. Our results demonstrates that without shading from our focal species, one of which produces many branches that provide shade, grasses will keep dominating the land for years with little recruitment or increase in AGB. By specifically using native species that are high wood density and fast-growing as in our study, we could foster a cost-effective system to manage secondary forest succession to increase long-term carbon storage. With increasing demands for land and energy, native species plantations that are carbon-efficient both in time and space could be a key component of a comprehensive plan for climate change mitigation.