Variability of water fluxes through the black spruce ( Picea mariana) canopy and feather moss ( Pleurozium schreberi) carpet in the boreal forest of Northern Manitoba

Water flux measurements in a stand of black spruce ( Picea mariana) with a feather moss ( Pleurozium schreberi) floor in the boreal forest of Northern Manitoba show that stemflow is volumetrically insignificant, constituting less than 1% of gross precipitation amounts. Canopy interception is shown to be up to 60% of gross precipitation for small events, and approximately 15% for large ones. Season-long canopy interception was 23% of gross precipitation. Moss interception is shown to be approximately 23% of total throughfall amounts, giving a season-long `whole-system' interception of 41% of gross precipitation. The data suggest that approximately 79% of throughfall inputs move through the moss layer within a few days of input events, and that the approximate 21% retained by the moss subsequently evaporate during quiescent periods. Throughfall inputs to the moss layer are strongly spatially variable, resulting in a similar variability of process in the moss layer. The data also suggest that processes occurring at the moss–mineral soil interface are influential in determining the nature of system hydrologic response.