MWRPP Report 15.4: Seaford Wetlands Vegetation Monitoring Program: report on Phragmites expansion and control.

This report details work done to date for the Seaford Wetlands vegetation monitoring program, which has now been running for 2 years. In particular, the report details results from: i) The second resurvey of 24 permanent quadrats – 12 established to monitor the expansion/contraction of Phragmites reed beds, and 12 established to assess the effectiveness of slashing as a means to control Phragmites; and ii) Photos taken at six photo-monitoring points Survey results suggest that Phragmites reed beds have contracted over the last two years, primarily in lowlying areas of wetland cell SCE2.However, there has also been some expansion of reed beds in more elevated areas, e.g. along the northern periphery of SCW1. This pattern of expansion/contraction reflects longer-term trends and the suitability of water regimesat the different elevations, with Phragmites expanding into low-lying areas previously unsuitable during the Millennium drought (~ 1996-2009), and being slowly drowned out of some of these areas during the relatively wetter conditions of recent years.Results from the slashing experiment strongly suggest that the slashing of Phragmites is an effective method of control if remaining stubble is subsequently flooded for a considerable length of time (i.e. at least several months), and ineffective otherwise. In low-lying quadrats of low relief, which would have experienced flooding for several months during the winter-summer periods of the following two years (to a mean depth > 20 cm), Phragmites regrowth has been minimal after two years. In contrast, in more (even slightly) elevated quadrats the recovery of Phragmites was virtually wholesale one year after slashing. This general pattern of response to slashing – successful control when subsequently flooded for several months or full recovery without subsequent flooding – is in accordance with experiences from previous attempts to control Phragmites via slashing at both the Seaford and neighbouring Edithvale Wetlands. For example, attempts to control Phragmites at Edithvale Wetlands were successful when following slashing in 2013, subsequent flooding (~20-30 cm) for around nine months prevented recovery of Phragmites. Apart from Phragmites, photo-point monitoring and general observations highlighted the need for greater vigilance in the control of other invasive plants, particularly Juncus acutus* and Acacia longifolia*. Both these species should be targeted for specific control at Seaford. It remains to be seen, where slashing and flooding have been successful in dramatically reducing Phragmites, whether Phragmites will regrow vigorously as soon as conditions become more favourable, or whether its rhizomatous energy reserves have become depleted such that recovery would be slow. I.e. it is not known how many years of water regime appropriate for Phragmites control are necessary to preclude Phragmites recovery. However, it is likely that over the long-term the containment of Phragmites at Seaford will require regular control efforts involving the slashing of low-lying low relief areas during dry times, with the success of these efforts dependent on subsequent flooding.