Depth of burial, an important factor in controlling bacterial decay of waterlogged archaeological poles

Wood discs from two waterlogged softwood poles were investigated for variat ions in bacterial decay. Exterior and interior degradation was observed usi ng light, transmission and scanning electron microscopy. Maximum water cont ent (U-max) was measured and extent of decay from the surface towards the w ood interior was investigated. Despite a well preserved appearance, the maj ority of the tracheids were heavily degraded. Erosion bacteria were identif ied as the main degraders and a significant difference in degree of decay w as found between the upper and lower parts of each pole. Small differences in oxygen concentration, derived from depth of burial, are suggested as the controlling factor. Active erosion bacterial decay was found in the inner parts of the 1200-year old wooden poles. (C) 2000 Elsevier Science Ltd. All rights reserved.