Investigating Moira Grass at the Ramsar listed Barmah Forest in Victoria
Moira Grass seed bank study (Barmah Forest)
Goulburn Broken Catchment Management Authority(from funding supplied by the Victorian Environmental Water Holder, and MDBA, The Living Murray Intervention Monitoring program).
The Living Murray is a joint initiative funded by the New South Wales, Victorian, South Australian, Australian Capital Territory and Commonwealth governments, coordinated by the Murray–Darling Basin Authority.
To assess if environmental watering of Barmah Forest has resulted in Moira Grass replenishing a viable seed bank.
Moira Grass plains form part of the Ramsar ecological character description of Barmah Forest. The extent of Moira Grass has declined over time, thought to be a result of changes in frequency, duration and depth of flooding in the forest. Continued reduction or loss of Moira Grass has implications under the Ramsar agreement. The documented rate of decline indicates the species may no longer dominate any area of the open plains. Conservation of Moira Grass plains is therefore of great concern.
Environmental watering at Barmah Forest regularly targets and supports the germination, flowering and growth requirements of Moira Grass. Published evidence indicates that Moira Grass best responds to seasonal inundation during the winter-spring period, followed by a summer drying phase (Roberts & Marston 2011; Colloff et al. 2013; Vivian et al. in prep.). Managed flooding in Barmah Forest in spring 2013 specifically targeted Moira Grass (MDBA 2014; VEWH 2014). Successful growth and widespread flowering resulted, but plants were only observed from locations where established Moira Grass beds were known to have occurred prior to flooding. This suggests that the species grew only from existing rootstock and not from seed. If the species is only reproducing via vegetative propagation re-colonisation of its former extent on the plains may be very slow, if it occurs at all.
More information is required to determine the extent and viability of the Moira Grass seed bank. Germination from seed bank is preferable, not only for improving genetic diversity, but also to greatly enhance the distribution and dispersal throughout former ranges. This information will help to determine the appropriateness of current environmental water targets, specifically duration of inundation to promote flowering and ability to achieve recolonisation via seed dispersal and germination.
The millennium drought, which was followed by unusually deep and protracted flooding in 2011-2012 did not result in substantial germination or re-growth of Moira Grass. The subsequent successful flowering of Moira Grass following flooding in 2013-14 provided an opportunity to determine if Moira Grass existed within the seed bank and if present, are these seeds viable.
In this study we undertook two complementary methods to assess the extent and viability of Moira Grass seeds in Barmah Forest:
We targeted wetlands in which Moira Grass has recently flowered thereby potentially replenishing the seed bank and compared these results to results from wetlands where Moira Grass has previously occurred but did not grow in response to flooding. Seeds were also collected opportunistically from mature plants in the southern Murray–Darling Basin and tested for viability.
Very few monocotyledon seedlings germinated from the wetlands in which Moira Grass is absent compared with wetlands in which Moira Grass is present. None of these were identified as Moira Grass. Direct counting of seeds within the seed bank indicated that seeds with Moira Grass morphology were present in all wetlands, although their viability was assessed as being less than 2% viable in wetlands in which Moira Grass is present and non-viable in wetlands where it is absent. In comparison, the proportion of viable seeds collected from mature plants ranged from 16 to 27%.
These results indicate that the seed bank of Moira Grass within Barmah Forest is limited, with no indication of a long-term viable seed bank. Recruitment of this plant is likely coming from below-ground stolons and/or existing rootstock.
These outcomes could assist with filling a knowledge gap of sexual versus vegetative reproduction for the site, which is one of the most southerly-distributed localities for Moira Grass (as identified by Colloff et al. 2013). This in turn has significance for determining the relative ease of maintaining ecological character (Moira Grass extent) for Ramsar reporting.
Roberts J, Marston F (2011) Water regime for wetland and floodplain plants: a source book for the Murray–Darling Basin, National Water Commission, Canberra.
Colloff, M.J., Ward, K.A. & Roberts, J. (2013) Ecology and conservation of grassy wetlands dominated by spiny mudgrass Pseudoraphis spinescens in the southern Murray-Darling Basin, Australia. Aquatic Conservation: Marine and Freshwater Ecosystems. DOI: 10.1002/aqc.2390.
MDBA (2014) Annual Report 2013-14. Murray-Darling Basin Authority, Canberra. URL address: http://www.mdba.gov.au/sites/default/files/MBDA-Annual-Report-2013-14.pdf.
VEWH (2014) Annual Report 2013-14. Victorian Environmental Water Holder, Melbourne. URL: http://www.vewh.vic.gov.au/__data/assets/pdf_file/0005/280688/VEWH_Annual_Report_2013-2014_web.pdf.
Vivian, L.M., Ward, K.A., Marshall D.J. and Godfree, R.C. (in prep.) Pseudoraphis spinescens (Poaceae) grasslands at Barmah Forest, Victoria, Australia: current distribution and implications for floodplain conservation. CSIRO Canberra & GB CMA Shepparton.