Soil Organic Carbon Turnover Over Time Across a Tropical Forest Edaphic Gradient

Tropical forests store almost one third of the worlds' soil organic carbon (C) and have amongst the highest net primary productivity globally. Large C stocks coupled with fast decomposition rates mean that changing climate could result in globally significant fluxes to or from these C pools. This study explored the fate of C produced in a tropical forest, and used large depositions of organic matter from three large hurricanes in the last thirty years (Hurricanes Maria, Georges, and Hugo) to examine the movement of a large pulse of organic matter and how this affected measured turnover times in soil different C pools.

We took advantage of well-documented archived soils taken from the Bisley Experimental Watersheds in the Luquillo Experimental Forest, Puerto Rico, in 1988. These soils were analyzed for C and N content, δ¹³C, and radiocarbon from bulk soils and density fractions, and compared to soils sampled at the same locations three decades later in 2018. For each time point, we sample three depths between 0 and 60 cm across replicate topographic gradients.