Trace Gases - Arizona State University：微量气体-亚利桑那州国家大学.ppt

* Result 3: Elevated CO2 reduces soil NH4+ in N-limiting soils but increases soil NO3- in the N-rich field soil Cheng et al. 2012. Science A: Microcosm Exp. 1; B. Microcosm Exp. 2; C. Field Exp. These results led us to ask: Why do plants not use the increased NO3- under elevated CO2? 2. Does elevated CO2 lead to plant preference of soil NH4+ over soil NO3- ? Bloom et al. 2010. Science Fig. 1. Three methods for assessing nitrate absorption (Absorb) and assimilation (Assim.) in wheat and Arabidopsis plants in hydroponic solutions where the shoots were exposed to atmospheres containing 380-ppm CO2 and 21% O2, 720-ppm CO2 and 21% O2, or 380-ppm CO2 and 2% O2. Does elevated CO2 lead to plant preference of soil NH4+ over soil NO3- ? Step 4 A meta-analysis of elevated CO2 impact on soil N and plant N acquisition in the literature Step 4 A meta-analysis of elevated CO2 impact on soil N and plant N acquisition in the literature. 38 studies that quantified the concentrations of soil NH4+ and NO3– and/or the capacity of plant use of NH4+ and NO3– under eCO2; These studies encompassed more than 58 species of crop, grass, and tree species. Result 4: Elevated CO2 reduced plant NO3- uptake and increased soil NO3- (Net effect %). Cheng et al. 2012. Science 20 40 -20 -40 Step 5 A field experiment to assess the impact of nitrification inhibition on AMF-mediated organic C decomposition under elevated CO2 X Result 5: Inhibition of nitrification offsets CO2-enhancement of AMF-mediated organic C decomposition Cheng et al. 2012. Science The Summary Fig. 4. A conceptual framework of AMF-mediated decomposition driven by CO2-enhancement of plant N acquisition. CO2-enhancement of AMF primes residue decomposition and ammonium (NH4+) release and optimizes NH4+ acquisition, while reducing nitrification. Cheng et al. 2012. Science Potential Implications The contribution of arbuscular mycorhizal fungi to soil C sequestration under future CO2 scenarios may have been over-esti