Abstracts on Global Climate Change
       

Oct 2006

Soil carbon turnover in the McMurdo Dry Valleys, Antarctica

Barrett, JE Virginia, RA Parsons, AN Wall, DH

SOIL BIOLOGY & BIOCHEMISTRY 38:10 3065-3082

Terrestrial ecosystems of the Antarctic Dry Valleys are among the most inhospitable soil environments on Earth due to climate and substrate limitations over biota. These ecosystems present a challenge to understanding controls over carbon (C) cycling because likely sources of organic matter are 10(2)-10(4) yrs old and in situ soil respiration is typically less than 1.0 mu mol CO2 m(-2) s(-1). In this paper we describe an analytical approach to characterize kinetic pools of labile and recalcitrant soil C, and estimate C turnover in dry valley soils based upon these descriptions. Rate parameters for C turnover were derived from laboratory incubations conducted under a range of soil moistures and temperatures. We developed a C flux and reservoir model using these rate parameters along with published estimates of internal C transformations in soil microbial ecosystems, and a previously described primary production (NPP) model for Antarctic endolithic communities. We found that decomposition in 120 d incubations was well described by double-exponential rate kinetics, and that temperature, moisture and substrate availability significantly influenced observed rates of soil respiration. Simulations of soil C cycling based upon these parameters produced initially high rates of soil respiration following inputs of external organic matter, with mean residence times for C of 10-60 yrs. Soil organic C content equilibrated at 44-140% of observed levels within 1000 yrs. Simulations of equilibrium C were sensitive to NPP, microbial efficiency (Y), and the distribution of C inputs into labile and passive pools, indicating that more thorough investigation of microbial influence over the C cycle in dry valley soils is necessary. (c) 2006 Elsevier Ltd. All rights reserved.

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