The impact of carbon dioxide fertilization, changing land use, and nitrogen-deposition on soil carbon storage

Fossil fuel combustion and changing land use have increased atmospheric and oceanic carbon inventories less dramatically than expected. This discrepancy has been termed the "missing sink." CO{dollar}sb2{dollar} fertilization and N-deposition processes could be sequestering some of this missing carbon. An improved understanding of disturbance and recovery carbon dynamics associated with changing land use may reduce this discrepancy by lowering biospheric release estimates. This research explores how these perturbations alter soil carbon inventories.; Soil carbon responds to perturbations to a greater or lesser extent, depending on the turnover time of the soil organic material. Using radiocarbon measurements and a simple model, I have modelled soil organic material's turnover times, which range from decades to millennia, as a binary system having active and passive components.; CO{dollar}sb2{dollar} fertilization, the plant net primary productivity increase observed at elevated CO{dollar}sb2{dollar} levels, increases soil carbon inventories. This research introduces a "greening" model to estimate this increase, using a CO{dollar}sb2{dollar} fertilization factor, active soil carbon inventory, and turnover time.; This research also uses radio carbon measurements to examine how cultivation reduces the inventory of active soil carbon. Further, the relationships between carbon loss and vegetation type, farming technique, and the clay content of soil have been examined to identify patterns that can be used to develop strategies for mitigating future carbon loss.; Formerly cultivated lands that are undergoing secondary succession can sequester atmospheric carbon. This research extends previous work in this area. One coniferous site in this study had a higher soil carbon inventory than its native deciduous counterpart.; Anthropogenic nitrogen deposition, like CO{dollar}sb2{dollar} fertilization, may also increase soil carbon storage. This research sets limits on the amount of carbon sequestered by nitrogen deposition by determining the amount and fate of anthropogenic nitrogen.; In summary, CO{dollar}sb2{dollar} fertilization and N-deposition can potentially sequester a major portion of the so-called missing sink. This research identifies ways to limit biospheric carbon loss and enhance carbon recovery on formerly disturbed lands. ftn*Originally published in DAI Vol. 55, No. 3. Reprinted here with additional bibliographic information.