ARS | Publication request: PRECIPITATION TIMING ALTERS SOIL C STORAGE IN A GREAT BASIN SHRUB-STEPPE ECOSYSTEM

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract
Publication Acceptance Date: August 10, 2006
Publication Date: February 9, 2007
Citation: Aanerud, Z., James, J.J., Svejcar, A.J. 2007. Precipitation timing alters soil c storage in a great basin shrub-steppe ecosystem [abstract]. Society for Range Management Meeting. Paper No.1

Technical Abstract: Predictions of precipitation responses to global warming vary in timing, magnitude and inter-annual variability. Most research investigating impacts of precipitation timing have focused on plant responses but little is known concerning soil C responses. In a Great Basin shrub-steppe ecosystem, we quantified the effects of precipitation timing on SOC beneath Artemisia tridentata and Pseudoroegneria spicata canopies. For eleven years, plots received either 80% of mean annual precipitation between October-April (winter) or May-July (spring). These two scenarios were evaluated against a control that received the same amount of precipitation distributed according to the site's long-term precipitation pattern. The ability of soils to store SOC varied between winter and spring, perennial grass and shrub species, and SOC pools. Stores of more labile SOC beneath Artemisia declined from 1.1 to 0.79 kg C m-2 when exposed to current versus spring scenarios respectively. This loss of more labile SOC was not recaptured in more recalcitrant SOC. In contrast, SOC beneath Pseudoroegneria was similar between current and spring scenarios. Differences in sensitivity of SOC beneath these species to spring may reflect the slower relative growth rate of Artemisia compared to Pseudoroegneria, and hence the inability of Artemisia to replenish decomposed SOC. When these results were scaled across the community and included changes in vegetation cover, however, SOC beneath Pseudoroegneria decreased 4.1 Mg ha-1 (54% loss), while Artemisia decreased 0.86 Mg ha-1 (26% loss) from current to spring scenarios. Stores of SOC beneath either species did not differ significantly between the control and winter scenarios, possibly due to the similarity in soil moisture patterns induced by these scenarios. Our results demonstrate that cold deserts may experience a loss of SOC if precipitation timing shifts from winter to spring, and emphasizes the importance of evaluating changes in multiple SOC pools in tandem with alterations in species cover.