Carbon Sequestration and Plant Community Dynamics Following Reforestation of Tropical Pasture

Background

Conversion of abandoned cattle pasture to secondary forest in the tropics is a potential means to increase carbon sequestration as well as to enhance local biodiversity. This study uses data from a long-term tropical reforestation project – Luquillo Experimental Forest in Puerto Rico – to estimate rates of above- and belowground carbon sequestration.

Research goals & methods

The study uses data on soil carbon and diameter-derived tree carbon content from measurements on 15 plots taken in 1992, compared to long-term data from the time of planting in 1937 and compared to measurements taken in adjacent pasture. Soil carbon pools showed little variance by topography or species at approximately 102 ± 10 Mg/ha. By comparison with adjacent pasture, there was a net gain of 33 Mg C/a in reforested sites with a net sequestration rate of 0.54 Mg/ha per year. Aboveground tree biomass held approximately 80 ± 3 Mg C/ha, accumulating at a rate of approximately 1.4 Mg C/ha per year since establishment.

Conclusions & takeaways

Significant carbon sequestration can occur in older reforested ecosystems in the tropics. While the majority of research on carbon sequestration occurs in shorter-term research cycles in forests at or below 20 years of age, the trees in this study exhibited greater rates of carbon sequestration during the later 30 years of growth. Greater levels of soil carbon sequestration also occurred in the latter time period.