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EFFECTS OF ELEVATED CO2 AND TEMPERATURE ON SOIL C AND N: RESULTS OF A DOUGLAS FIR MESOCOSM STUDY
Citation:
Johnson, M G. EFFECTS OF ELEVATED CO2 AND TEMPERATURE ON SOIL C AND N: RESULTS OF A DOUGLAS FIR MESOCOSM STUDY. Presented at American Society of Agronomy 2000 Annual Meeting, Minneapolis, MN, November 5-9, 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 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 and ambient plus 200 mo1/mo1) and two levels of air temperature (ambient and ambient plus 4 C) with three replicates. Full profile soil samples were collected every 6 months beginning in the fall of 1993 until the end of the experiment in the summer of 1997. Bulk density measurements were made at each sampling. Soil samples were analyzed for C and N content and course fragments. Soil C increased over the study and soil N decreased, however, these changes were not due to the experimental treatments. We conclude that moving the soil from high elevation (forest @ 1219 m) to low elevation (Corvallis @ ~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.