Coarse particulate organic matter inputs to a headwater swamp stream

Inputs of allochthonous particulate organic matter were measured during 1992-94 in a headwater conifer swamp stream in southern Ontario, Canada. Litter transported to the stream by surface runoff from saturated areas of the swamp was compared to direct litterfall and lateral transfer from stream banks. Litterfall contributed 61-63 % of the annual litter input to the stream in comparison to 14-16 % and 20-25 % for lateral bank transfer and swamp surface runoff, respectively. Litterfall and bank inputs were seasonal with an autumn peak. In contrast, litter transport by surface runoff occurred mainly in May-September during episodes of rapid overland flow associated with thunderstorms. The annual composition of litterfall was approximately 48 % conifer needles, 32 % woody tissues and 17 % deciduous leaves. Lateral bank transfer contributed a smaller proportion of needles (37.5 %) and a higher proportion of leaves (22 %). Litter transported in runoff from the swamp was mainly woody tissues (70 %) and the needle and leaf fraction comprised <15 %, indicated that retention and decomposition occurred on the swamp surface. These results indicate that surface runoff from headwater swamps increases the amount and alters the composition and seasonality of litter inputs to streams.