Cold desert biological soil crust community influences soil CO2 exchange

Cold deserts, like the Colorado Plateau, US are the understudied relatives of warm deserts (eg. Sonora desert, US) with respect to their carbon cycling dynamics. Most of the rain pulse events measured in the Canyonlands region (Colorado Plateau) were smaller than 5 mm.

The biological soil crust (biocrusts) are an important community in these deserts, found in the first few millimeters of the soil. Because they are located at the soil-air interface, they dry quickly and are quick to respond to short-term changes in moisture and temperature. Bowling et al. (2011) used in-situ subsurface CO2 and CO2 isotope measurements, and soil surface CO2 flux measurements to assess the responses of the grasslands and biocrusts to seasonal variation in precipitation in the Canyonlands (Colorado Plateau).

The authors found that belowground soil respiration was enhanced by rain events, where dry soils were found to have an amplified response to an initial rain event when compared to subsequent events, and was also found to be sensitive to changes in temperature. Species composition of the biocrust communities determined overall rates of carbon gain: moss-lichen dominated communities fixed up to four times the amount of carbon than cyanobacteria-dominated biocrust communities. These findings highlight the extreme temporal variability experienced in biocrust and grassland communities, which require continuous in field measurements in order to be observed.

Bowling et al. (2011), “Rain pulse response of soil CO2 exchange by biological soil crusts and grasslands of the semiarid Colorado Plateau, United States”

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