Sedell, J. R.; Triska, F. J.; Hall, J. D.; Anderson, N. H.; Lyford, J. H. 1974. Sources and fates of organic inputs in coniferous forest streams. In: R. H. Waring and R. L. Edmonds (eds.). Integrated research in the coniferous forest biome. Coniferous For. Biome Bull. 5. Seattle, WA: U. S. International Biome Program, University of Washington: 57-69.
A study of the quality and magnitude of particulate organic inputs was undertaken in two streams in the Oregon Cascades. Objectives included estimation of litterfall and lateral movement of organic debris into a stream, estimation of litter breakdown rates, and construction of a first-approximation organic material budget. In this study, approximately 65% of the litterfall input consisted of Douglas-fir and hemlock needles, which fall throughout the year. Deciduous inputs occurred primarily mid-October through November and consisted principally of vine maple and big leaf maple. Preliminary lateral movement data indicated that organic material entering watershed 10 from the bank was 1.5 times the litterfall. The total estimate of litter input is approximately 2.5 g M-2 day-1. Both streams have the capacity to process all types of leaf litter within a year. Needles, the most refractory leaf litter, are processed by microbes and, once conditioned, are consumed readily by invertebrate shredders.Thus the large amounts of needle litter that enter the stream in late summer and fall constitute a food source usable by stream detritivores after deciduous litter has decomposed. Leaf-pack experiments have revealed the danger of extrapolation of biological information from smaller to larger streams. Faster processing times for larger streams have been suggested by information on weight loss, invertebrate biomass, and leaf quality. Changes in litter quality were determined by increases in the percentage of lignin content. Increases in lignin composition were compared with decreases in non-cell-wall constituents to obtain an estimate of microbial activity.Information on litterfall and lateral movement, in conjunction with previously collected data, led to a first-approximation particulate organic matter budget for watershed 10. When compared with a similar budget from a very different stream system, processing capabilities of the two streams were remarkably similar.In both streams almost 990 of the particulate organic material entered from terrestrial systems. About two-thirds of the organic inputs entering each stream were processed within the system, indicating the processing role of small forest streams.