13 BACTERIAL DEGRADATION OF ARCHAEOLOGICAL WOOD IN ANOXIC WATERLOGGED ENVIRONMENTS

摘要

1 INTRODUCTION Wood contains the most dominant and abundant biopolymers in the global ecosystem. The main chemical components of wood are carbohydrates such as cellulose and hemicellulose and the polyphenol lignin which are all assembled into a complex cell wall matrix. On a yearly basis 80-100 billion tons of wood are produced by photosynthesis and it represents the largest input of biogenic carbon to the global carbon cycle. The biogenic carbon is returned as inorganic carbon after a complex interaction of decay mechanisms of biotic and abiotic origin. Wood decays within years to decades under aerobic conditions, mainly by the action of wood degrading fungi. In anoxic ecosystems such as bogs, marine and freshwater sediments, and waterlogged soils the decay takes place by bacteria and abiotic factors during centuries, millennia and in some extreme cases even millions of years1'2. The resistance of wood to biotic and abiotic decay is caused not only by the anoxic environmental conditions but also by the structure and organisation of the cell wall components; a generic property that is often termed recalcitrance. Anoxic (anaerobic) waterlogged environments are large sinks in the global carbon cycle, but the decay mechanisms acting in these environments are not fully understood.