Organic Contribution of Stream Edge Forest Litter Fall to the Chalk Stream Ecosystem

Litter fall from four species typical of the banks of southern English chalkstreams is given (Salix viminalis, Fraxinus excelsior, Acer pseudoplanatus and Alnus glutinosa). The one way passage of leaves from the stream banks to the stream was insignificant because of their retention amongst bank vegetation below the tree canopy. Production of organic material by aquatic plants (750 g m-2) within the stream was three times that available to the stream ecosystem by litter fall (240 g m-2) in an area with trees Alnus glutinosa on only one bank. The litter fall within an adjacent wood, where aquatic plant production was insignificant, was 466 g m-2. The establishment of a low density tree cover on small chalk streams is suggested as an aid to their management. This canopy would reduce the light available for aquatic plant growth and hence reduce flooding, but would maintain organic material input (litter fall) to the ecosystem.