Rain pulse response of soil CO2 exchange by biological soil crusts and grasslands of the semiarid Colorado Plateau, United States

David R. Bowling; Edmund E. Grote; Jayne Belnap

doi:10.1029/2011jg001643

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Rain pulse response of soil CO2 exchange by biological soil crusts and grasslands of the semiarid Colorado Plateau, United States

David R. Bowling·Edmund E. Grote·Jayne Belnap

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Abstract

Biological activity in arid grasslands is strongly dependent on moisture. We examined gas exchange of biological soil crusts (biocrusts), the underlying soil biotic community, and the belowground respiratory activity of C 3 and C 4 grasses over 2 years in southeast Utah, USA. We used soil surface CO 2 flux and the amount and carbon isotope composition (δ 13 C) of soil CO 2 as indicators of belowground and soil surface activity. Soil respiration was always below 2 μmol m -2 s -1 and highly responsive to soil moisture. When moisture was available, warm spring and summer temperature was associated with higher fluxes. Moisture pulses led to enhanced soil respiration lasting for a week or more. Biological response to rain was not simply dependent on the amount of rain, but also depended on antecedent conditions (prior moisture pulses). The short-term temperature sensitivity of respiration was very dynamic, showing enhancement within 1-2 days of rain, and diminishing each day afterward. Carbon uptake occurred by cyanobacterially dominated biocrusts following moisture pulses in fall and winter, with a maximal net carbon uptake of 0.5 μmol m -2 s -1 , although typically the biocrusts were a net carbon source. No difference was detected in the seasonal activity of C 3 and C 4 grasses, contrasting with studies from other arid regions (where warm- versus cool-season activity is important), and highlighting the unique biophysical environment of this cold desert. Contrary to other studies, the δ13C of belowground respiration in the rooting zone of each photosynthetic type did not reflect the δ 13 C of C 3 and C 4 physiology.

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Journal of Geophysical Research G: Biogeosciences Article

Source-reported bounding extent: 37.89219554724437° to 38.69408504756833° latitude; -110.3192138671875° to -109.6270751953125° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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David R. Bowling, Edmund E. Grote, Jayne Belnap. 2011-09-08. Rain pulse response of soil CO2 exchange by biological soil crusts and grasslands of the semiarid Colorado Plateau, United States. https://doi.org/10.1029/2011jg001643

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