Bardgett et al_2007_v3p487

Bardgett et al_2007_v3p487 - Biol. Lett. (2007) 3, 487490

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Biol. Lett. (2007) 3 , 487–490 doi:10.1098/rsbl.2007.0242 Published online 3 July 2007 Community ecology Heterotrophic microbial communities use ancient carbon following glacial retreat Richard D. Bardgett 1, * ,† , Andreas Richter 2,† , Roland Bol 3 , Mark H. Garnett 4 , Rupert Ba ¨umler 5 , Xingliang Xu 2 , Elisa Lopez-Capel 6 , David A. C. Manning 6 , Phil J. Hobbs 3 , Ian R. Hartley 1 and Wolfgang Wanek 2 1 Institute of Environmental and Natural Sciences, Lancaster University, Lancaster LA1 4YQ, UK 2 Department of Chemical Ecology and Ecosystem Research, University of Vienna, 1090 Wien, Austria 3 Institute of Grassland and Environmental Research, North Wyke, Okehampton, Devon EX20 2SB, UK 4 NERC Radiocarbon Laboratory, East Kilbride, Glasgow G75 0QF, UK 5 Institute of Geography, University of Erlangen, Nu ¨rnberg, Kochstrasse 4/4, 91054 Erlangen, Germany 6 School of Civil Engineering and Geoscience, University of Newcastle, Newcastle-upon-Tyne NE1 7RU, UK * Author for correspondence ( r.bardgett@lancaster.ac.uk ). These authors contributed in equal part to this work. When glaciers retreat they expose barren sub- strates that become colonized by organisms, beginning the process of primary succession. Recent studies reveal that heterotrophic micro- bial communities occur in newly exposed glacial substrates before autotrophic succession begins. This raises questions about how heterotrophic microbial communities function in the absence of carbon inputs from autotrophs. We measured patterns of soil organic matter development and changes in microbial community composition and carbon use along a 150-year chronosequence of a retreating glacier in the Austrian Alps. We found that soil microbial communities of recently deglaciated terrain differed markedly from those of later successional stages, being of lower biomass and higher abundance of bacteria relative to fungi. Moreover, we found that these initial microbial communities used ancient and recalcitrant carbon as an energy source, along with modern carbon. Only after more than 50 years of organic matter accumulation did the soil microbial community change to one supported primarily by modern carbon, most likely from recent plant production. Our Fndings suggest the existence of an initial stage of heterotrophic microbial community development that precedes autotrophic community assembly and is sustained, in part, by ancient carbon. Keywords: microbial communities; organic matter; carbon; chronosequence 1. INTRODUCTION The global retreat of glaciers is receiving much attention, especially as a signal of climate change ( Oerlemans 2005 ). When glaciers retreat they expose barren substrates that become colonized by organisms, beginning the process of primary succession. The common view is that primary succession is started by autotrophs, including algae, mosses, lichens and higher plants, owing to a lack of carbon for hetero- trophic organisms ( Walker & del Moral 2003 ).
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Bardgett et al_2007_v3p487 - Biol. Lett. (2007) 3, 487490

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