Association of reduced riparian vegetation cover in agricultural landscapes with coarse detritus dynamics in lowland streams
D. J. Reid A C , P. S. Lake A , G. P. Quinn B and P. Reich AA School of Biological Sciences, Monash University, Clayton, Vic. 3800, Australia.
B School of Life and Environmental Sciences, Deakin University, Warrnambool, Vic. 3280, Australia.
C Corresponding author. Email: davidjonreid@hotmail.com
Marine and Freshwater Research 59(11) 998-1014 https://doi.org/10.1071/MF08012
Submitted: 22 January 2008 Accepted: 16 August 2008 Published: 27 November 2008
Abstract
Studies were conducted on streams flowing through agricultural floodplains in south-eastern Australia to quantify whether reductions in riparian canopy cover were associated with alterations to the input and benthic standing stocks of coarse allochthonous detritus. Comparisons were made among three farmland reaches and three reaches within reserves with intact cover of remnant overstorey trees. Detritus inputs to these reaches were measured monthly over 2 years using litter traps. Direct inputs to streams within the reserves were relatively high (550–617 g ash free dry weight (AFDW) m–2 year–1), but were lower at farmland reaches with the lowest canopy covers (83–117 gAFDW m–2 year–1). Only a minor fraction of the total allochthonous input (<10%) entered any of the study reaches laterally. The mean amounts of benthic detritus were lowest in the most open farmland reaches. Standing stocks of benthic detritus were found to be highly patchy across a large number of agricultural streams, but were consistently very low where the streamside canopy cover was below ~35%. Canopy cover should be restored along cleared agricultural streams because allochthonous detritus is a major source of food and habitat for aquatic ecosystems. Given the absence of pristine lowland streams in south-eastern Australia, those reaches with the most intact remnant overstorey canopies should be used to guide restoration.
Additional keywords: allochthonous input, canopy cover, coarse particulate organic matter, Eucalyptus camaldulensis, litter trap.
Acknowledgements
This research was funded by Monash University and the Co-operative Research Centre for Freshwater Ecology while D. J. Reid held a Monash Postgraduate Scholarship. Financial assistance for this study was also provided by the Murray-Darling Basin Commission. Thank you to the Goulburn-Broken CMA, Lachlan CMA, Murray CMA and North Central CMA for supporting this research and to the many landholders who kindly provided access through their properties. Thanks also to all those who helped with field and laboratory work, and to Peter Domelow for help with constructing the litter traps. The suggestions of three anonymous reviewers and Andrew Boulton helped to improve the quality of the manuscript.
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