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ELEVATED CO2 AND TEMPERATURE ALTER THE ECOSYSTEM C EXCHANGE IN A YOUNG DOUGLAS FIR MESOCOSM EXPERIMENT
Citation:
TINGEY, D. T., E. LEE, D. L. PHILLIPS, P. T. RYGIEWICZ, R. S. WASCHMANN, M. G. JOHNSON, AND D. M. OLSZYK. ELEVATED CO2 AND TEMPERATURE ALTER THE ECOSYSTEM C EXCHANGE IN A YOUNG DOUGLAS FIR MESOCOSM EXPERIMENT. PLANT, CELL, AND ENVIRONMENT. Blackwell Publishing, Malden, MA, 30:1400-1410, (2007).
Impact/Purpose:
We investigated the effects of elevated CO2 (EC) [ambient CO2 (AC) + 190 ppm] and elevated temperature (ET) [ambient temperature (AT) + 3.6 °C] on net ecosystem exchange (NEE) of seedling Douglas fir (Pseudotsuga menziesii) mesocosms.
Description:
We investigated the effects of elevated CO2 (EC) [ambient CO2 (AC) + 190 ppm] and elevated temperature (ET) [ambient temperature (AT) + 3.6 °C] on net ecosystem exchange (NEE) of seedling Douglas fir (Pseudotsuga menziesii) mesocosms. As the study utilized seedlings in reconstructed soil–litter–plant systems, we anticipated greater C losses through ecosystem respiration (Re) than gains through gross photosynthesis (GPP), i.e. negative NEE. We hypothesized that: (1) EC would increase GPP more than Re, resulting in NEE being less negative; and (2) ET would increase Re more than GPP, resulting in NEE being more negative. We also evaluated effects of CO2 and temperature on light inhibition of dark respiration. Consistent with our hypothesis, NEE was a smaller C source in EC, not because EC increased photosynthesis but rather because of decreased respiration resulting in less C loss. Consistent with our hypothesis, NEE was more negative in ET because Re increased more than GPP. The light level that inhibited respiration varied seasonally with little difference among CO2 and temperature treatments. In contrast, the degree of light inhibition of respiration was greater in AC than EC. In our system, respiration was the primary control on NEE, as EC and ET caused greater changes in respiration than photosynthesis.