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Tropospheric ozone reduces stable soil carbon formation under elevated carbon dioxide.
Loya, Wendy*,1, Pregitzer, Kurt1, Karberg, Noah 2, King, John1, Giardina, Christian 2, 1 Michigan Technological University, Houghton, MI2 USDA Forest Service, Houghton, MI
ABSTRACT- Tropospheric O3 levels have increased by 35% over the last century across the northern hemisphere, and are steadily increasing in association with development in tropical regions. Elevated tropospheric O3 inhibits forest and agricultural productivity, including CO2-stimulated forest productivity, but the impact of elevated O3 on carbon storage in soil is unknown. We used O3 fumigation coupled with Free-Air CO2 Enrichment (FACE) technology in experimental aspen (Populus tremuloides) and birch (Betula papyrifera) forests to examine the impact of elevated O3 on formation of decay-resistant soil carbon under elevated CO2. We found that increasing O3 reduced formation rates of decay-resistant carbon in soil by 50%, relative to amounts entering this pool due to elevated CO2 alone. This change was driven by reduced detrital inputs to soil and microbial utilization of new carbon inputs. These results suggest that offsetting atmospheric increases in CO2 by increasing carbon sequestration in forest soils may be limited by simultaneous increases in O3.
Key words: elevated CO2, FACE, soil carbon, elevated O3