WOOD DYNAMICS IN COASTAL-PLAIN BLACKWATER STREAMS

Quantified woody debris in the river swamps of the 6th order Ogeechee River and several smaller tributaries in the Coastal Plain of the SE USA, compared swamp wood with woody debris in the channel, and studied wood movement in the swamp and main channel over 20 mo. Woody debris in the swamps was relatively low (0.362-0.880 kg ash-free dry mass (AFDM)/m2) compared to several mixed temperate deciduous forests. Wood in the tributary swamps was low (mean 0.82 kg AFDM/m2), and there were no trends along the river continuum. Wood in the channels of both the Ogeechee (6.46 kg AFDM/m2) and a 4th order tributary (2.24 kg AFDM/m2) were significantly higher than found in their adjacent floodplains. Woody debris appeared to increase in stream channels from smaller tributaries to the 6th order river, opposite of that observed in other river systems. Only 17% of wood in the Ogeechee channel had moved after 3 major floods, much less than in the swamps (21-84%). Abundance and stability of woody debris in the main channel allows it to be a major habitat type and source of food for both riverine invertebrates and fishes. The fate of most swamp wood appears to be decomposition and fragmentation, rather than import to the river channel. -Authors