COARSE PARTICULATE ORGANIC-MATTER INPUTS TO A HEADWATER SWAMP STREAM

Inputs of allochthonous particulate organic matter were measured durin g 1992-94 in a headwater conifer swamp stream in southern Ontario, Can ada. Litter transported to the stream by surface runoff from saturated areas of the swamp was compared to direct litterfall and lateral tran sfer from stream banks. Litterfall contributed 61-63 % of the annual l itter input to the stream in comparison to 14-16 % and 20-25 % for lat eral 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 e pisodes of rapid overland flow associated with thunderstorms. The annu al composition of litterfall was approximately 48 % conifer needles, 3 2 % woody tissues and 17 % deciduous leaves. Lateral bank transfer con tributed a smaller proportion of needles (37.5 %) and a higher proport ion 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 swa mp surface. These results indicate that surface runoff from headwater swamps increases the amount and alters the composition and seasonality of litter inputs to streams.