Examining passive riparian revegetation in degraded rivers: livestock exclusion and environmental flows

Passive riparian revegetation techniques are becoming increasingly important tools in river rehabilitation. However the utility of the sediment seed bank as a passive riparian regeneration option is poorly understood. A livestock excluded site has been monitored over a three year period and compared to a continuously grazed site to test the regeneration potential of the seed bank. Livestock exclusion was successful in increasing erosion resistance (roughness) and the regeneration of native species but not successful in restoring communities or regenerating substantial numbers of woody species. The utility of the seed bank does not extend to the restoration of full communities and requires direct plantings to provide a more developed assemblage. A seedling emergence experiment has compared the effects of simulated flood durations on the seedling emergence of desirable riparian species. The inundation of bench units using environmental flows would not significantly increase or decrease recruitment of desirable species from the seed bank. Significant differences in seedling emergence and timing under different inundation periods were found to vary among species. These studies provide greater understanding of how passive revegetation utilising riparian seed banks can best achieve river rehabilitation goals and how revegetation objectives should be framed when utilising riparian seed banks.