Controls on the Storage and Loss of Soil Organic Carbon with Reforestation of Abandoned Pastures

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At a global scale, soil carbon storage generally increases with clay content, and carbon loss via soil respiration can be relatively well predicted from mean annual temperature and rainfall. At an ecosystem scale, the mechanisms responsible for C retention and loss are less well understood. This study will use a long-term and well-replicated pasture-to-forest chronosequence to study the factors that contribute to soil C storage and loss. The research will follow C from plant litter inputs through decomposition to storage in soils, and loss via CO2. Chemical properties of plant tissues change during secondary succession, and thus the impact of the litter chemistry on ecosystem processes is also likely to change over time. The research will use field and laboratory experiments and stable- and radioisotopes to compare and contrast the roles of litter chemistry, above- and belowground litter inputs, and soil chemical properties in belowground C cycling over 82 yr of reforestation. This research will contribute to understanding of how plants influence soil C dynamics, and improve the ability to predict the effects of reforestation and afforestation on C sequestration.