Interaction of water temperature and shredders on leaf litter breakdown: a comparison of streams in Canada and Norway

Author： Taylor Barry Andrushchenko Irene

ISSN： 0018-8158

Source： Hydrobiologia, Vol.721, Iss.1, 2014-01, pp. : 77-88

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Abstract

Litter decomposition in running water sometimes proceeds faster in small, cool tributaries than in warm, wide rivers because stenothermal, leaf-shredding invertebrates are more abundant in the cool streams. Evidence from eastern Canada suggests that the cold-stenothermal stonefly Leuctra has a disproportionate influence on rapid mass loss in upstream reaches of soft-water river systems, but is not replaced by an effective, warm-water shredder downstream. To test the generality of this observation, we compared litter decomposition rates in upstream (second or third order) and downstream (fourth or fifth order) reaches of a medium-size river system in Nova Scotia (Canada) and three river systems in Nordland (Norway). In all river systems, mass loss of nitrogen-rich speckled alder (Alnus incana) leaves and nitrogen-poor red maple (Acer rubrum) leaves proceeded faster at the upstream site only if water temperature there was significantly cooler than downstream. Decomposition rates in all systems were strongly correlated with abundance of Leuctra, and to a lesser extent the caddisfly Lepidostoma. The distribution of Leuctra seems to be driven primarily by water temperature, with a strong peak of abundance at 14°C, but may also be influenced by competition from other shredding species.