Litter retention in Tasmanian headwater streams after clear-fell logging |
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Authors: | Anne Watson Leon A Barmuta |
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Institution: | (1) School of Zoology, University of Tasmania, Private Bag 5, Sandy Bay, Tasmania, 7005, Australia;(2) School of Zoology and Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Private Bag 5, Sandy Bay, Tasmania, 7005, Australia |
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Abstract: | Clear-fell logging around small headwater streams in Tasmanian wet eucalypt forests was predicted to affect both the retention
of leaf litter and the composition and size of leaf packs. Retention structures were surveyed in six natural streams and six
streams in forest regenerated 3–5 years after clear-fell and burn logging. Logged streams had more wood, but retained less
leaves than natural streams, and consequently had fewer and smaller leaf packs. Leaf packs from natural streams contained
200% more leaves, bark and twigs than packs from logged streams. The effect of buoyancy on leaf retention was assessed with
release and recapture of marked Eucalyptus obliqua and Nothofagus cunninghamii leaves. Eucalypt leaves were more likely to be trapped by retention structures on the bed of the stream, while smaller, more
buoyant N. cunninghamii leaves were mainly trapped by leaf packs. Leaf packs in natural streams were formed on a matrix of small twigs and long strips
of bark, shed from the upper branches of mature stringybark eucalypts, while leaf retention was reduced in logged streams
because there are no mature trees to provide effective retention structures. Changes to the channel form increase both discharge
and sedimentation. These factors have strong implications for downstream nutrient processing and riverine food webs. |
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