The hydro-geomorphic structure and function of temperate upland swamps in eastern Australia

Geomorphic structure provides the basis that underpins abiotic ecosystem function. Changes in abiotic structure result in profound changes to key functions such as water and carbon storage. Temperate Highland Peat Swamps on Sandstone (THPSS) are a type of upland wetland found in the headwaters of low order streams on the plateau regions of eastern Australia. Similar to fens in the Northern Hemisphere, they are valley bottom swamps and, like their Northern Hemisphere counterparts, have been subject to anthropogenic impacts resulting in changes to both their structure and function. This thesis examines the importance of geomorphic structure to THPSS abiotic functions such as water and carbon storage. THPSS sedimentology comprises organic sandy sediments with high carbon content and peat forming potential, which is inter-related with their high water tables. Depending on swamp/catchment structural characteristics, these systems can be either primarily rainwater - fed or derive some of their water from surrounding groundwater. Hydrological regimes of intact systems are relatively stable, acting as water storage features in the landscape and consistently contributing to downstream base flows. However, once these systems incise and become channelised fills, their function as a water storage system declines, with lowered water holding capacity in the altered swamp sediment contributing to water table drawdowns with concomitant increases in swamp discharges, transforming these systems from a water storage zone into a water throughflow system. In their intact state, THPSS are effective carbon stores with high carbon to nitrogen ratios and low rates of fluvial carbon exports. Once these systems become channelised, their ability to store carbon is compromised, with high volumes of carbon being exported out of the system via the channel, decreasing the carbon content of swamp sediment. This reduced functional capacity in channelised fills emphasises the importance of assessing, monitoring, conserving and restoring the geomorphology of these systems to protect and restore the abiotic functions of these endangered ecological communities