Assessment of Riparian Revegetation Trials on In‐Channel Benches in the Hunter Valley of Southeast Australia

Abstract

Large-scale river training works have been carried out in the Hunter valley since 1955 in response to flood-driven channel changes. Vegetation was planted on in-channel benches induced by river training works to consolidate the deposits and to increase channel boundary roughness. Exotic species of vegetation such as willows and poplars were previously used. In 1983, ten trial sites were planted with various species of native vegetation. Survival rates were evaluated in 1987 and 1997. The most successful species planted was Eucalyptus camaldulensis with an overall survival rate of 77 per cent in 1997. The Acacia species were found to be short-lived, exhibiting a significant decline in survival rates between 1987 and 1997. Survival rates for most species were higher on sand-bed than on gravel-bed sites. This difference may be attributed to better drainage on benches at the sand-bed sites. Investigations of flood disturbance showed that between 1983 and 1997 the sites were flooded between four and 13 times. The survival rates of Grevillea robusta and Eucalyptus melliodora trees were negatively correlated with the total number of recorded floods at each site. Poor natural regeneration of planted species is attributed to a combination of periodic flooding, intensive weed growth, low light intensities at ground level and grazing disturbance. These trials were not well designed for statistical analysis but provide valuable long-term information on the suitability of various species for planting in riparian rehabilitation programs. Such information is of relevance not only to river and catchment management authorities, but also to community groups.

Survival of Casuarina cunninghamiana on a recovering sand-bed stream in the Wollombi Valley of coastal New South Wales.

“…The rate of survival was low, but consistent with other studies of riparian species (Hicks et al 1999;Webb et al 1999) used in river training works in the Hunter Valley. Long-stem planting may improve survival by reducing both the risk of removal and burial by flood (Hicks et al 1999) but further quantitative, longer-term and better designed studies on this planting technique are needed.…”

“…24% of these remain 24 years later and just over half of them produced fruit in 2011; a survival rate within the range found by previous studies of planted riparian trees and shrubs. Webb et al (1999) found survival rates of tree species that typically occur in riparian habitats along sand-bed streams in the Hunter Valley ranged from 33% (Angophora floribunda) to 89% (Eucalyptus camaldulensis) (measured14 years after being planted). Unfortunately there is no comparative data for Casuarina cunninghamiana survival because this species was not usually planted as part of river training works at that time, despite its widespread distribution in the region (Webb et al 1999).…”

“…Webb et al (1999) found survival rates of tree species that typically occur in riparian habitats along sand-bed streams in the Hunter Valley ranged from 33% (Angophora floribunda) to 89% (Eucalyptus camaldulensis) (measured14 years after being planted). Unfortunately there is no comparative data for Casuarina cunninghamiana survival because this species was not usually planted as part of river training works at that time, despite its widespread distribution in the region (Webb et al 1999). However Hicks et al (1999), reporting on the survival of four riparian tree species planted at two sites in the Hunter Valley, compared the performance of long-stem and standard tube-stock and included Casuarina cunninghamiana.…”

Functional trait differences between extant exotic, native and extinct native plants in the Hunter River, NSW: a potential tool in riparian rehabilitation

“…Willows (Salix spp.) were introduced to provide bank stabilization (Webb et al, 1999;Erskine and Webb, 2003), while other exotic plant species have colonized the riparian zone from the surrounding landscape. Today much of the riparian margin in the Upper Hunter catchment is dominated by exotic species with only a handful of natives remaining, the most conspicuous of which is Casuarina cunninghamiana.…”

How Does Restoration of Native Canopy Affect Understory Vegetation Composition? Evidence from Riparian Communities of the Hunter Valley Australia

“…Owing to limited access, incomplete records, or patchy canopy cover as a result of poor survival, only five suitable riparian restoration sites were identified within the study region. Two sites located on the Pages and Hunter Rivers were established in 1983 (Webb et al 1999). A third site located on the Upper Hunter River immediately north of Muswellbrook was established in 1998.…”