PARENT SESSION
Poster Session #1: Decomposition and Soil Respiration.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
5
Soil carbon turnover in Antarctic Dry Valley ecosystems, an analytical approach.
Barrett, J*,1, McManus, Catherine1, Virginia, Ross1, Parsons, Andy2, Wall, Diana2, 1 Dartmouth College, Hanover, NH2 Colorado State University, Fort Collins, CO
ABSTRACT- Terrestrial ecosystems of the Antarctic Dry Valleys are among the most inhospitable soil environments on earth due to severe climate and low productivity. In this environment the legacies of previous landscapes and events are thought to drive contemporary ecosystem dynamics. For example, much of the contemporary soil organic matter is likely derived from Pleistocene lake sediments. Due to the existence of this legacy carbon pool, the low productivity of soils and climatic limitations over decomposition, controls over organic matter accumulation and turnover are thought to operate over millennial time scales. However, calculations of carbon turnover using in situ and laboratory estimates of soil respiration yield mean residence times on the order of decades, even when constrained by climatic records. We present an analytical approach to model soil carbon turnover in McMurdo Dry Valley ecosystems of varying complexity, from single pool systems to systems with two to three carbon pools described by distinct turnover kinetics. Rate parameters for carbon turnover are derived from laboratory incubations under a range of temperature and moisture conditions, and from in situ substrate addition experiments and gas exchange measurements. Carbon mineralization in laboratory incubations is well described by first order kinetics, and temperature, soil moisture and substrate availability significantly influenced the observed rates of soil respiration. The effect of temperature on in situ soil respiration was approximately linear, but temperature and moisture had strong interactions over the range of conditions studied These models suggest that a slow turnover pool of soil carbon may be at steady state, and stable over century to millennial time scales, while a smaller active pool has rapid turnover kinetics and may respond to pulses of resources and favorable climates. We conclude that multiple pool models of soil carbon can account for the apparent paradox of rapid carbon turnover in an ecosystem controlled by legacies.
KEY WORDS: Antarctic Dry Valleys, carbon mineralization, soil carbon, soil organic matter