Soil Respiration Rates for Tomatoes Subjected to Elevated Carbon Dioxide Levels.

Anthropological inputs of CO₂ have increased overall CO₂ concentrations in the atmosphere leading to global climate change. There have been many studies showing a positive correlation between soil respiration and elevated CO₂ levels on C3 photosynthetic plants.  However, additional research is needed to better understand these interactions in open-field agro-systems and to assess the impacts of increased atmospheric CO₂ on soil carbon sequestration.  Therefore, the objective of this study was to evaluate and compare the effects of varying CO₂ levels applied to tomatoes on soil respiration rates.  The experiment was conducted in Fresno, CA, where tomatoes grown in open-fields were subjected to ambient and elevated CO₂ conditions.  The enriched-CO₂ plots received 1.5-2 times the CO₂ levels naturally present in the ambient-CO₂ plots (370 ppm).  In elevated plots, CO₂ was applied through surface drip lines from August 2010 through the end of the growing season.  Daily levels of atmospheric CO₂ within the plant canopy were monitored using a CO₂ Analyzer.  A CIRAS-2 portable photosynthesis system with an attached LED light source and a CO₂ flux analyzer was used to measure the plant CO₂ exchange rates (photosynthesis) and soil respiration rates, respectively.  Additionally, soil moisture and temperature data were recorded daily.  Plant and root samples were taken at the end of the growing season to determine above and below biomass.  The data collected for plant photosynthesis and soil respiration rates as well as for the plant and root biomass will be presented.  The results will include a comparative analysis between the ambient and elevated CO₂ treatments.