Community Dynamics of Leaf Litter Breakdown in a Utah Alpine Stream

Leaf litter breakdown was examined in a Rocky Mountain stream in Utah during fall 1976 and winter 1977. Leaf mass loss, changes in macroinvertebrate community structure, and patterns in community respiration were measured on pairs of leaf packs removed from the stream every 2-3 d. Colonization of the leaf packs by macroinvertebrates was rapid. The dominant organisms during the initial colonization were shredders. Highest total oxygen consumption occurred during the initial colonization phase. Macroinvertebrate density, invertebrate biomass, and oxygen consumption adjusted for remaining leaf mass all showed a dramatic increase in variance associated with the final phase of decomposition (<20% leaf material remaining). The final phase of breakdown may have the most interesting biological interactions owing to the high variability in leaf biomass and long residence times that directly affect the utility of the leaf pack as habitat and food.