Annual CO2 flux from a biological soil crust system on the Colorado Plateau: Effects of increased temperature and summer precipitation

Biological soil crusts (BSC’s) consist of a diverse community of organisms including cyanobacteria, lichens and mosses that form a link between above and belowground soil processes. BSC’s fix atmospheric CO₂, and this carbon may then be consumed and respired by underlying soil fauna. In this study we measured CO₂ flux from the soil in areas covered with BSC’s. Five 40cm diameter soil collars were inserted into the ground for each of three treatments: increased temperature (+2 °C), increased summer rainfall (additional 30, 2mm events), and the two combined. Measurements were taken with an automated chamber system every hour over the course of an entire year in order to determine the effect of altered temperature and/or precipitation on CO₂ flux rates. Our preliminary results indicate CO₂ loss from the above treatments was approximately 18%, 30% and 29% greater than the 470 kg C ha^-1 yr^-1 in control plots, respectively.  However, this CO₂ loss was statistically significantly greater from controls in only the summer rainfall treatment. Our preliminary data suggest with increased temperature and rainfall there will be the potential for a net loss of an additional 690 – 870 kg C ha^-1 yr^-1 from this ecosystem. With the vast surface area covered by biological soil crusts this amounts to a greatly increased atmospheric CO₂ source.