- Title
- Organic matter dynamics in willow and eucalypt lined central Victorian streams
- Creator
- Wilson, Michael
- Date
- 2001
- Type
- Text; Thesis; PhD
- Identifier
- http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/69168
- Identifier
- vital:4173
- Abstract
- The spread of exotic willows (Salix spp.) in SE Australia, New Zealand and South Africa has provoked widespread debate in scientific, management and broader communities. In Australia, the extent of spread is unknown, but at least 30000 km of river frontage in Victoria are lined by willows. Management and research literature has identified the poor knowledge of willow impacts on Southern Hemisphere aquatic ecosystems. It has been speculated that the major distinction between deciduous willows and evergreen native vegetation will be the timing and quality of litterfall. This would have flow-on consequences for metabolic processes, stream biota and water quality at reach, stream and catchment scales. These two vegetation types were studied through the preparation of partial organic matter budgets for native and willow lined reaches in a central Victorian catchment. Organic matter inputs from litter, groundwater and gross primary production (GPP), organic matter standing crop . and respiratory output were quantified. Total inputs to willow and native reaches were similar (735 and 764 g ash free dry weight m•' yl, respectively). Inputs were dominated by litterfall (-60%) and there were no significant differences in annual litterfall between sites. GPP contributed -20% of total inputs and estimates suggested there were few significant differences in annual GPP, 24 h community respiration, ratio of GPP to community respiration (PIR) or net daily metabolism (NDM) between sites. Groundwater contributed -20% of total inputs with one third of the dissolved organic matter sourced during short flow paths through riparian sediments. Aggradation at willow sites appeared to increase the riparian flow path. Willow and native sites were heterotrophic and similarly dependent on allochthonous organic matter (P/R=O.2, NDM= -.6, and ratio of net primary production to total inputs -0.1). Willow research and management should also focus on retention capacity, including the recruitment and role of LWD and the structure and function of root systems. Removal of willows potentially facilitates native vegetation establishment but simultaneously decreases retention capacity and metabolic control by the canopy. Establishing native vegetation to fulfil broader biodiversity objectives whilst retaining willows for their potentially positive roles is a management challenge. In principle, establishing native species on the upland-sides of fringing willows and under willow canopies will direct succession toward a preferred outcome without destructive disturbance. Understanding of when benefits of willows outweigh their costs is a notable gap.; School of Science & Engineering
- Publisher
- The Author [Mt. Helen, Vic.] :
- Rights
- Open Access
- Rights
- This metadata is freely available under a CCO license
- Subject
- Biology; Freshwater ecology; Willows; Stream ecology
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Australian Digital Thesis | 2 MB | Adobe Acrobat PDF | View Details Download |