Forest Soil Carbon Lost at a Greater Rate in Warmer Climates
Understanding and predicting the impacts of climate change and the stability of carbon stored in terrestrial ecosystems is an important part of planning future energy strategies. This Oak Ridge National Laboratory-led study compared the turnover time of labile soil carbon, in relation to temperature and soil texture, in several forest ecosystems that are representative of large areas of North America. Carbon (C) and nitrogen (N) stocks and C:N ratios were measured in the forest floor, mineral soil, and two mineral soil fractions (particulate and mineral-associated organic matter) at five AmeriFlux sites (a network that provides continuous observations of ecosystem-level exchanges of CO2, water, and energy across the Americas) along a latitudinal gradient in the eastern United States. With one exception, forest floor and mineral soil carbon stocks increased from warm, southern sites (with fine-textured soils) to cool, northern sites (with more coarse-textured soils). The exception was a northern site, with less than 10% silt-clay content, that had a soil organic carbon stock similar to the southern sites. Moving from south to north, the turnover time of labile soil organic C increased from approximately 5 to 14 years. Consistent with its role in stabilization of soil organic carbon, silt-clay content was positively correlated with stable C at each site. Latitudinal differences in the storage and turnover of soil C were related to mean annual temperature, but soil texture superseded temperature when there was too little silt and clay to stabilize labile soil C and protect it from decomposition. Overall, this study suggests that large labile pools of forest soil C are at risk of decomposition in a warming climate, especially in coarse textured forest soils.
Garten, C. T., Jr. 2011. “Comparison of Forest Soil Carbon Dynamics at Five Sites along a Latitudinal Gradient,” Geoderma 167-168, 30-40, DOI: 10.1016/j.geoderma.2011.08.007.