Mechanisms and Patterns of Soil Carbon Storage and Cycling in the Barro Colorado Nature Monument, Panama

This chapter presents soil carbon dynamics in the Barro Colorado Nature Monument (BCNM) and surrounding lowland Panamanian forests. I first review principles in soil carbon science for tropical forests, including soil carbon stocks, fractions, turnover times, inputs, and losses. I then review research on patterns and mechanisms of spatial and temporal variability in soil carbon dynamics, including among-site, seasonal, and depth-related variation as well as findings of experimental studies. Soil carbon stocks vary strongly among sites with soil weathering status, declining with fertility and increasing with clay content within the BCNM and in central Panama more generally. Rainfall seasonality drives seasonal variation in soil carbon inputs and losses. Experimental irrigation, nutrient addition, and litter manipulation studies have provided insight into the role of moisture, nutrient availability, and plant inputs in controlling soil carbon dynamics. Finally, I suggest future research directions, including constraining turnover times for different soil carbon fractions across depths.