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Title: Exposure to elevated CO2 increases total ecosystem carbon in the Mojave Desert

Author
item EVANS, R.D. - Washington State University
item KOYAMA, AKIHIRO - Colorado State University
item SONDERREGER, DEREK - Northern Arizona University
item CHARLET, THERESE - University Of Nevada
item NEWINGHAM, BETH - University Of Idaho
item FENSTERMAKER, LYNN - Desert Research Institute In Las Vegas
item HARLOW, BENJAMIN - Washington State University
item Jin, Virginia
item OGLE, KIONA - Arizona State University
item SMITH, STANLEY - University Of Nevada
item NOWAK, ROBERT - University Of Nevada

Submitted to: Nature Climate Change
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2014
Publication Date: 4/16/2014
Citation: Evans, R., Koyama, A., Sonderreger, D.L., Charlet, T.N., Newingham, B.A., Fenstermaker, L.F., Harlow, B., Jin, V.L., Ogle, K., Smith, S.D., Nowak, R.S. 2014. Exposure to elevated CO2 increases total ecosystem carbon in the Mojave Desert. Nature Climate Change. 4(2014):394-397. https://doi.org/10.1038/nclimate2184.
DOI: https://doi.org/10.1038/nclimate2184

Interpretive Summary: Deserts and arid rangelands cover about 47% of the terrestrial land surface and could play a major role in taking up atmospheric carbon dioxide (CO2), the major greenhouse gas causing climate change. In this study, we showed that a desert ecosystem stored large amounts of carbon (C) after 10 years of continuously exposure to atmospheric CO2 concentrations predicted for 2050. Forests and grasslands have shown increases in C storage due to greater biomass production. In the desert, biomass did not increase – instead, C storage occurred when plants increased how much carbon was exuded from roots into the soil. Greater root exudation stimulated soil microbial activity, which led to increased storage of organic C in desert soils.

Technical Abstract: Carbon dioxide (CO2) is the major greenhouse gas inducing climate change. Increases in global CO2 emissions, currently estimated at 8.4 Pg C y-1, have accelerated from 1% y-1 during 1990-99 to 2.5% y-1 during 2000-09. The carbon (C) balance of terrestrial ecosystems is the greatest unknown in the global C budget because the actual magnitude, location, and causes of terrestrial sinks are uncertain. Estimates of terrestrial C uptake, therefore, are often based on the residuals between direct measurements of the atmospheric sink and well-constrained models of ocean uptake of CO2. Here, we report significant terrestrial C accumulation caused by CO2-enhancements to net ecosystem productivity (NEP) in an intact, undisturbed arid ecosystem following ten years of exposure to elevated atmospheric CO2 ([CO2]). Although [CO2] enhancements to photosynthesis did not lead to increases in above- or belowground net primary productivity, higher NEP could be attributed to greater root exudation which stimulated microbial activity and subsequent storage of C in these aridland soils.