PARENT SESSION
Oral Session #76: Ecosystem Ecology: Larger scale processes, geomorphology, soils.
Presiding: W. Straw
Thursday, August 8. 9:00 AM to 11:30 AM. Gila Meeting Room, TCC.
Spatial heterogeneity and carbon cycling in the Patagonian steppe.
SALA, OSVALDO*,1, AUSTIN, AMY1, LAUENROTH, WILLIAM2, BURKE, INDGRID2, 1 University of Buenos Aires, Buenos Aires, Argentina2 Colorado State University, Fort Collins, Colorado
ABSTRACT- The Patagonian steppe is made up of two patch types: (1) shrubs surrounded by a dense ring of grasses (SR); and (2) scattered grass tussocks (ST) in a bare soil matrix. The two patch types are related in time through a cyclical succession process. We examined the consequences of this two-patch type-structure on C cycling. We report on long-term estimates of C input-output processes (primary production, decomposition) and C stocks in biomass, litter, and soil C for both patch types. The shrub-ring patch type, with only 17% of total cover, accounted for 60% of the aboveground primary production (35 g.m-2yr-1 vs 23 g.m-2yr-1 with 82% cover for ST). Decomposition in the shrub-ring patch type was significantly slower than in the scattered tussocks type (kSR=0.15 vs kST=0.3). Consequently, C stocks were much higher in the shrub-ring than in the scattered-tussocks patches. Total litter was 1343g.m-2 in SR and 95 g.m-2 in ST. Soil C in the upper 5 cm of the profile was higher in SR with 544 g.m-2 vs 223 g.m-2. The shrub-ring patches play a disproportionately large role in the cycling of C in the Patagonian steppe as a result of the combined high inputs and low rate of loss. Small changes in land use that affect the abundance of the SR patches will have a disproportionately large effect on total ecosystem C budget.
KEY WORDS: Carbon cycling, Patagonian steppe, Primary production, Soil carbon