Soil microbial community response to land-management and depth, related to the degradation of organic matter in English wetlands: Implications for the in situ preservation of archaeological remains Isabel Douterelo a, *, Raymond Goulder b , Malcolm Lillie c a Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK b Department of Biological Sciences, University of Hull, Cottingham Road, Hull, HU6 7RX, UK c Department of Geography, University of Hull, Cottingham Road, Hull, HU6 7RX, UK 1. Introduction Wetlands are defined by groundwater at the soil/sediment surface or above, or within the soil root zone, during all or part of the growing season (Caple, 1996). The soil is frequently saturated for prolonged periods and this leads to the development of anaerobic environments. In wetlands, the soil changes with depth from aerobic and oxidising conditions at the surface to anaerobic and reducing conditions at greater depths (Caple, 1996). When a soil becomes waterlogged there are important changes in abiotic factors such as redox potential (Eh) and pH, which consequently affect microbial community composition and function (McLatchey and Reddy, 1998). In anoxic strata, bacteria are the main inhabitants and the principal agents of organic matter decompo- sition (Bjo ¨ rdal et al., 2000; Blanchette, 2000; Powell et al., 2001; Gregory et al., 2002; Caple, 2004; Helms et al., 2004), for this reason these microorganisms were the main targets of our molecular genomic research. Microorganisms living in the soil subsurface play a vital role in the maintenance of soil ecological function; they are involved in decomposition, nutrient release, maintenance of soil structure, biogeochemical cycles, and groundwater chemistry (Fierer et al., 2003b; Goberna et al., 2005). However, how the structure and activity of microbial communities are modified with Applied Soil Ecology 44 (2010) 219–227 ARTICLE INFO Article history: Received 27 June 2009 Received in revised form 19 December 2009 Accepted 29 December 2009 Keywords: Archaeological remains Bacterial diversity Biolog Cloning–sequencing DGGE Organic matter degradation Wetlands ABSTRACT Wetlands are important habitats not only for their unique ecological value but also because they contain organic material that is fundamental to our understanding of precedent landscape and human past. This study compares the effects of two different land-management regimes on metabolic diversity and bacterial community structure with depth in order to relate them to the process of organic matter degradation and the potential for preservation in situ of organic archaeological artefacts in wetland soils. Soil cores were collected at five depths down to 100 cm from two wetlands sites in England. Environmental variables were monitored and the metabolic capabilities of the microbial community were studied using Biolog Ecoplates 1 . DNA was extracted from soil, and the bacterial community structure was examined by polymerase chain reaction followed by denaturing gradient gel electrophoresis (PCR-DGGE). To determine compositional changes in the bacterial community with depth, information about specific groups of bacteria at the site with higher water table (Hatfield Moor) was obtained by cloning and sequencing of 16S rRNA genes. Biolog and DGGE analyses showed depth variation and between-site variation. Carbon substrate utilization and bacterial diversity decreased with increasing depth. The wetland soil under an arable regime in which the water levels were kept elevated, showed higher metabolic capability and bacterial richness when compared with the soil under pasture and subjected to long-standing drainage. Cloning and sequencing showed that Proteobacteria and Acidobacteria were the predominant taxa within the soil profile, but there was a clear shift in bacterial community composition with increasing depth as several taxonomic groups (d-Proteobacteria and Spirochaetes) were only detectable at 50 cm depth. Because the site with a high and stable water table presented higher metabolic activity and bacterial diversity, it may be that saturated conditions and a high water table are not sufficient to guarantee the preservation in situ of organic material such as archaeological artefacts. ß 2010 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +44 0 2476522697. E-mail addresses: I.Douterelo@warwick.ac.uk, idouterelo_soler@hotmail.com (I. Douterelo). Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil 0929-1393/$ – see front matter ß 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.apsoil.2009.12.009