HR: 1340h
AN: B43A-0251    [Abstracts]
TI: Controls over soil organic matter accumulation and turnover in the McMurdo Dry Valleys, Antarctica
AU: * Barrett, J E
EM: John.E.Barrett@Dartmouth.edu
AF: Environmental Studies Program, Dartmouth College, Hanover, NH 03755 United States
AU: Virginia, R A
EM: Ross.A.Virginia@Dartmouth.edu
AF: Environmental Studies Program, Dartmouth College, Hanover, NH 03755 United States
AU: Wall, D H
EM: diana@nrel.colostate.edu
AF: Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523 United States
AB: Terrestrial ecosystems of the Antarctic Dry Valleys are among the most inhospitable soil environments on Earth due to extreme climate and severe substrate limitation on soil food webs. These ecosystems are a challenge to understanding controls over carbon (C) cycling since some of the major events controlling organic matter accumulation likely occurred during the Last Glacial Maximum when paleo-lakes deposited sediments over much of the presently exposed surfaces. It remains unclear to what extent dry valley soil ecosystems are fueled by legacy organic matter derived from these ancient sediments vs. rapid cycling of contemporary organic matter inputs. We report a model to evaluate controls over the soil organic C in the dry valleys. The model is based upon determinations of standing pools of soil C and is driven by rate parameters estimated from 120 d incubations conducted over a range of soil temperature and moisture. Theoretical values for parameters describing internal C transformations are used to generate predictions about the distribution of C among slow and rapidly cycling pools. Potential levels of contemporary C inputs are derived from a previously published primary production model for Antarctic cryptobiotic communities. Simulations (100 y) run under average climate conditions indicated initially high rates of C turnover with mean residence times of 20-50 y followed by equilibration of soil organic C at 25% to 80% of initial standing stocks. The model is very sensitive to temperature resulting from the high Q10 values calculated from the 120 d incubations; hence steady state soil C levels are determined largely by regional differences in climate. Sensitivity analyses indicated that steady state C levels are also very responsive to variation in simulated primary production, microbial efficiency, the distribution of C into labile and recalcitrant pools, and soil moisture. Model simulations run under recently observed climate suggest that C dynamics are sensitive to inter-annual variability in summer temperature and soil moisture. These results underscore the sensitivity of polar desert soil ecosystems to climate variability and potential climate change.
DE: 0400 BIOGEOSCIENCES
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
SC: Biogeosciences [B]
MN: Fall Meeting 2005