- Title
- Age and hydrological significance of lichen limits on sandstone river channels near Sydney, Australia
- Creator
- Sammut, Jesmond; Erskine, Wayne D.
- Relation
- ARC
- Relation
- Geografiska Annaler: Series A Physical Geography Vol. 95, Issue 3, p. 227-239
- Publisher Link
- http://dx.doi.org/10.1111/geoa.12016
- Publisher
- Wiley-Blackwell
- Resource Type
- journal article
- Date
- 2013
- Description
- Trimmed lichen communities (lichen limits) are abrupt changes from a lichen community to a scoured bare rock surface and have been used to determine bankfull channel capacity on bedrock channels and their response to the combined disturbances of flow regulation and climate change. They can also be used to set flushing flows in bedrock channels. In sandstone gorges of the Nepean River, Australia, the crustose lichen, Lecidea terrena Nyl, was common at both gorge and cemetery (sandstone headstones) sites, enabling construction of growth curves for above and below dam areas. Growth curves were used to date lichen colonisation of sandstone surfaces in rivers. The oldest, highest lichen limit at all sites represented the pre-flow regulation lichen community because its characteristics above and below Nepean Dam were similar and were trimmed to a level that produced consistent discharges across a range of catchment areas. They corresponded to return periods of less than 2 years on the annual maximum series and was developed during the flood-dominated regime (FDR) of 1857–1900. Lichen limits form by the phycobiont dominating the mycobiont and hence degrading lichen thalli due to water inundation causing weak or dead thalli to be scrubbed from the rock surface. Trimming to the unregulated lichen limit represents a small flood of frequent occurrence appropriate for flushing bedrock channels. A lower lichen limit was only found below a diversion weir and was formed by frequent dam spills between 1950 and 1952 during an extraordinary wet period at the start of the FDR between 1949 and 1990. Lichens colonised exposed sandstone between the level of frequent flows from 1949 to 1952, and the high lichen limit. On the Avon River, an additional lower limit reflected a massive downward shift in flow duration following the start of interbasin diversions to Wollongong in 1962.
- Subject
- lichen growth curves; Lecidea terrena Nyl; alternating flood- and drought-dominated regimes; flushing flows; flow regulation; phycobiont; mycobiont
- Identifier
- http://hdl.handle.net/1959.13/1300339
- Identifier
- uon:20048
- Identifier
- ISSN:0435-3676
- Language
- eng
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