Forestry effects on headwater ecosystem health: a multi-catchment experiment
As forested stream ecosystems derive most of their energy from leaf-fall, timber harvesting is predicted to affect stream foodwebs and ecosystem health. Forestry Corporation has monitored runoff and turbidity in 5 experimental catchments in northern NSW since 2001 and will harvest 3 of them in 2007 to compare responses with 2 control areas. This is a unique catchment-scale opportunity to supplement these data with ecological information to test how aquatic biodiversity, leaf litter breakdown and foodweb structure respond to potential reductions in organic matter input and altered runoff. Results will improve measures to protect aquatic biodiversity and ecosystem function.
This project aims to test the following relating to whether there are:
- declines in import of organic matter (leaves and wood) in streams after harvesting?
- associated responses by invertebrate detritivores (‘shredders’ – leaf breakdown, ‘collectors’ - feeding on fine particulate organic matter, FPOM < 1mm)?
- detectable declines in overall abundance and diversity due to loss of detrital inputs?
- shifts in invertebrate community composition from detritivores to herbivores (‘grazers’) in response to reduced canopy cover?
- declines in rates of in-stream organic matter breakdown?
- increases in in-stream photosynthesis (algal production)?
- shifts in food web structure from that dominated by terrestrial carbon inputs (e.g., leaf litter) to that dominated by carbon produced in-stream (e.g., algae)?
- increases in in-stream sedimentation rates?
Funded by Forestry Corporation and the Australian Research Council
Dr Ashley Webb