Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: June 4, 2007
Publication Date: September 5, 2007
Citation: Jin, V.L. 2007. Elevated CO2 alters root N uptake and C turnover in Larrea tridentata L. In: Proceedings of the Ecological Society of America, August 5-10, 2007, San Jose, California. 2007 CDROM. Technical Abstract: To examine the impact of elevated CO2 on root N uptake, soil N availability and the feedbacks between them, we quantified the effects of elevated CO2 and N additions on root N uptake and leaf C gain in Larrea tridentata seedlings grown in reconstituted Mojave Desert soils. After six months of growth under ambient (380 ppm) or elevated CO2 (600 ppm), plants were photosynthetically-labeled with 13CO2 while soils were labeled simultaneously with 15N (glycine, NH4+, or NO3-). Plants and soils were then harvested over 7 weeks at 0, 2, 10, 24, and 49 days. Elevated CO2 decreased both above- and belowground biomass in Larrea tridentata. Nitrogen additions did not improve plant growth, but did increase root N concentrations under elevated CO2 only. Decreases in root biomass and increases in root N concentrations indicated increased N uptake under elevated CO2. Elevated CO2 enhanced the uptake of glycine and NH4+, but not NO3- which remained high in both CO2 treatments. Elevated CO2 did not affect gross NH4+ fluxes, but did increase soil NH4+ mean residence time and gross NO3- consumption rates. Strong correlations between root biomass and gross mineralization and NO3- consumption rates reflected the tight coupling between organic matter availability and microbial N cycling in Mojave Desert soils. Decreases in plant biomass under elevated CO2 could have profound effects on long-term N cycling by negatively affecting C substrate availability for microbes involved in N mineralization and NO3- consumption. Decreases in both aboveground and belowground inputs, however, could be offset potentially by increases in litter quality.