Effects of pH and plant source on lignocellulose biodegradation rates in two wetland ecosystems, the Okefenokee Swamp and a Georgia salt marsh1,2,3

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Abstract
The microbial mineralization of synthetic [14C]lignin, specifically radiolabeled [14C‐lignin]‐lignocellulose and [14C‐polysaccharide]‐lignocellulose from a variety of aquatic herbaceous and woody plants was investigated in water and sediment from a salt marsh on Sapelo Island, Georgia, and from the Okefenokee Swamp, an acidic peat‐forming freshwater swamp in southern Georgia. Rates of microbial degradation of lignocellulose were depressed in the Okefenokee relative to those in the salt marsh. About 50% of the difference in mineralization rates was attributable to the low ambient pH (3.9) of Okefenokee water relative to the pH of salt marsh water (pH 7.1). Rates of mineralization of the lignin component of lignocellulose were only minimally affected within the range of pH 4–8, whereas mineralization of the polysaccharide component increased severalfold with increasing pH. Differences in the biodegradability of the various lignocelluloses were also observed; lignocelluloses from herbaceous plants were mineralized several times faster than lignocellulose from wood.