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EFFECTS OF ELEVATED CO2 AND TEMPERATURE ON SOIL C AND N IN A DOUGLAS FIR MESOCOSM STUDY
Citation:
Johnson, M G., P T. Rygiewicz, D T. Tingey, AND D M. Olszyk. EFFECTS OF ELEVATED CO2 AND TEMPERATURE ON SOIL C AND N IN A DOUGLAS FIR MESOCOSM STUDY. Presented at 2000 Fall Meeting of the American Geophysical Union, San Francisco, CA, December 15-19-2000.
Description:
We conducted a 4-year study on the effects of elevated CO2 and elevated air temperature on Douglas fir seedlings growing under controlled climate and exposure conditions in outdoor sun-lit mesocosms. 1+1 seedlings were planted in mesocosms in Corvallis, OR in the spring of 1993 in a reconstructed native forest soil from the Oregon Cascade Mountains. The experimental design was a 2 x 2 factorial experiment with 2 levels of CO2 exposure (ambient CO2 and ambient CO2 plus 200 mol/mol) and two levels of air temperature (ambient temperature and ambient temperature plus 4?C) with three replicates. Full profile soil samples and bulk density samples were collected every 6 months beginning in the fall of 1993 until the end of the experiment in the spring of 1997. Soil samples were analyzed for C and N content and coarse fragments. Soil C increased and soil N decreased over the study, however, these changes were not due to the experimental treatments. We conclude that moving the soil from high elevation (forest located at 1219 m) to low elevation (Corvallis located ~75 m) extended the growing season and caused the observed changes. With warmer temperatures under climate change, extended growing seasons are likely to occur. Consequently, increased C sequestration and reduced soil N are likely outcomes of climate change on forested systems in the Pacific Northwest.