Pseudoraphis spinescens

Pseudoraphis spinescens, called spiny mudgrass or Moira grass is a rhizomatous and stoloniferous aquatic or semi-aquatic perennial grass, with ascending stems forming loose, floating mats in water to 1 m deep or more, or with stems to 50 cm high when not submerged.[1] Moira grass (Pseudoraphis spinescens) was first described in 1810 by Robert Brown as Panicum spinescens,[2] and subsequently transferred to Pseudoraphis by Joyce W. Vickery in 1950.[3]

Pseudoraphis spinescens
Pseudoraphis spinescens
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Clade: Commelinids
Order: Poales
Family: Poaceae
Subfamily: Panicoideae
Genus: Pseudoraphis
Species:
P. spinescens
Binomial name
Pseudoraphis spinescens
Synonyms

Panicum spinescens R.Br.

Pseudoraphis spinescens is native to floodplains in Asia and Australasia,[4] it is a C4 species, requiring seasonal cycles of prolonged, deep flooding interspersed with drying to achieve maximum growth and reproduction.[4][5][6] Between flood events, P. spinescens forms a deep thatch of collapsed dry stems until flooding recurs and growth recommences.[4][6] A study in southeastern Australia found that P. spinescens does not have a viable long-lived seed bank in floodplain soil,[7] presumably regenerating from vegetative propagules and rootstocks.[8]

In the Murray-Darling Basin, prior to regulation of the Murray River, extensive Pseudoraphis spinescens dominated floodplain marshes existed in areas that were typically seasonally flooded for 5-9 months duration in most years, to a minimum water depth of 0.5 m, and completely dry during late summer and autumn.[5][9]

Pseudoraphis spinescens is an important species in floodplain marsh ecosystems, providing habitat and food for a range of fauna including birds,[10] frogs,[11][12] fish and insects,[13] and key ecosystem functions such as nutrient cycling and primary productivity.[6]

Significance in the Murray Darling Basin

The Barmah Forest Ramsar site [14] on the Murray River floodplain in northern Victoria (Australia) is a bioregionally significant seasonal floodplain wetland, historically the most extensive areas of Moira grass (Pseudoraphis spinescens) plains in the Murray-Darling Basin occurred in this region.[14]

The extent of floodplain marshes in Barmah forest has been severely reduced since European settlement, with the introduction of large grazing animals and the diversion of water from the Murray River.[15][16] Floodplain areas previously dominated by aquatic species such as Moira grass (Pseudoraphis spinescens), common reed (Phragmites australis) and cumbungi (Typha spp.) are now covered with species adapted to lower levels of flooding, mainly river red gums (Eucalyptus camaldulensis) and giant rush (Juncus ingens).[15][17][18]

A 2017 CSIRO analysis found that the management changes most likely to result in an increase in the current extent of Moira grass plains in Barmah National Park, over the next 10 years are reducing grazing, and increasing flood duration and depth.[19] Most significantly, the removal of the large population of feral horses in Barmah National Park is estimated to result in a 61% increase in the current extent of the Moira grass plains.[19][20] An analysis of the rate of vegetation change in Barmah Forest, published in 2014, predicted that if no management actions were taken, Pseudoraphis spinescens dominated grassy wetlands would become locally extinct by 2026.[12]

Water regime for vigorous growth [4]
Maintenance: Flooding for vigorous grasslands of Pseudoraphis spinescens should be seasonal, annual and fairly predictable, with a seasonal dry phase. Small variations in water regime favour its competitors, leading to a compositional or structural change. Growth after flooding is from rootstock, rather than fragments or seeds.
Frequency of flooding: Annual or near annual, i.e. every year, occasionally once in two years.
Depth of flooding: Initially depth is not critical: flood peak may exceed 2 m, then water levels should stabilise at about 1 to 1.5 m for two to three months, but not less than 0.5 m until drying out.
Duration of flooding: On average about seven months. Can tolerate less: no less than five months if starting in winter, and no less than three months if starting in spring. Can tolerate longer: but durations of 10 months should happen rarely and not in sequential years.
Timing of flooding: Floods can start at any time from winter to early spring.
Regeneration: Importance of seeds and seed bank is not known. No information on seedling growth.
Critical flood interval: Reflood after two years to maintain vigour. Pseudoraphis spinescens grasslands should not be without flooding for more than five years [4].

References
  1. Royal Botanic Gardens Victoria. "Flora of Victoria: Pseudoraphis spinescens". Flora of Victoria.
  2. Brown, Robert (1810). Prodromus florae Novae Hollandiae et Insulae Van-Diemen, exhibens characteres plantarum. Vol. 1. Londini: Typis R Taylor, veneunt apud J. Johnson.
  3. Vickery, Joyce W. (1950). "Pseudoraphis spinescens (R.Br.) n. comb., and some records of New South Wales grasses". Proceedings of the Royal Society of Queensland. 62 (7): 69–72.
  4. Roberts, Jane; Marston, Frances (2011), Water regime for wetland and floodplain plants: a source book for the Murray-Darling Basin (PDF), National Water Commission
  5. MDBC (2006), The Barmah-Millewa Forest Icon Site Environmental Management Plan 2006-2007. MDBC Publication No. 30/06 (PDF), Murray-Darling Basin Commission
  6. Colloff, Matthew J.; Ward, Keith A.; Roberts, Jane (2014). "Ecology and conservation of grassy wetlands dominated by spiny mud grass Pseudoraphis spinescens in the southern Murray-Darling Basin, Australia". Aquatic Conservation: Marine and Freshwater Ecosystems. 24 (2): 238–255. doi:10.1002/aqc.2390.
  7. Durant, Rebecca A.; Nielsen, Daryl L.; Ward, Keith A. (2016). "Evaluation of Pseudoraphis spinescens (Poaceae) seed bank from Barmah Forest floodplain". Australian Journal of Botany. 64 (8): 669. doi:10.1071/bt15288.
  8. Ward, Keith A. (1991), Investigation of the flood requirements of the Moira grass plains in Barmah Forest, Victoria, Department of Conservation and Environment, Victoria
  9. Bren, L. J.; Gibbs, N. L. (1986). "Relationships between flood frequency, vegetation and topography in a river red gum forest". Australian Forest Research. 16: 357–370.
  10. Leslie, David J. (2001). "Effect of river management on colonially-nesting waterbirds in the Barmah-Millewa forest, south-eastern Australia". Regulated Rivers: Research & Management. 17 (1): 21–36. doi:10.1002/1099-1646(200101/02)17:1<21::AID-RRR589>3.0.CO;2-V.
  11. McGinness, Heather M.; Arthur, Anthony D.; Ward, Keith A.; Ward, Paula A. (2014). "Floodplain amphibian abundance: responses to flooding and habitat type in Barmah Forest, Murray River, Australia". Wildlife Research. 41 (2): 149. doi:10.1071/WR13224. S2CID 83640154.
  12. Colloff, Matthew J.; Ward, Keith A.; Roberts, Jane (2014). "Ecology and conservation of grassy wetlands dominated by spiny mud grass Pseudoraphis spinescens in the southern Murray-Darling Basin, Australia". Aquatic Conservation: Marine and Freshwater Ecosystems. 24 (2): 238–255. doi:10.1002/aqc.2390.
  13. Barton, Philip S.; Colloff, Matthew J.; Pullen, Kimberi R.; Cunningham, Saul A. (2013). "Grassland area determines beetle assemblage dissimilarity from surrounding floodplain forest". Journal of Insect Conservation. 17 (6): 1209–1219. doi:10.1007/s10841-013-9602-8. S2CID 17953069.
  14. Australian Wetlands Database (1982). "Australian Wetlands Database - Barmah Forest".
  15. Dexter, B.D. (1978). "Silviculture of the river red gum forests of the central Murray floodplain". Proceedings of the Royal Society of Victoria. 90 (1): 175–192.
  16. Vivian, L. M.; Ward, K. A.; Marshall, D. J.; Godfree, R. C. (2015). "Pseudoraphis spinescens (Poaceae) grasslands at Barmah Forest, Victoria, Australia: current distribution and implications for floodplain conservation". Australian Journal of Botany. 63 (6): 526. doi:10.1071/BT15090.
  17. Chesterfield, E. A. (1986-01-01). "Changes in the vegetation of the river red gum forest at Barmah, Victoria". Australian Forestry. 49 (1): 4–15. doi:10.1080/00049158.1986.10674458.
  18. Bren, L. J. (1992). "Tree invasion of an intermittent wetland in relation to changes in the flooding frequency of the River Murray, Australia". Austral Ecology. 17 (4): 395–408. doi:10.1111/j.1442-9993.1992.tb00822.x.
  19. Nichol, Sam; Stratford, D.; Joehnk, K.; Chadès, I. (2017), Prioritising the value of information for management of Moira grass at Barmah forest. (PDF), CSIRO Land and Water
  20. Nicol, Sam; Ward, Keith; Stratford, Danial; Joehnk, Klaus D.; Chadès, Iadine (2018). "Making the best use of experts' estimates to prioritise monitoring and management actions: A freshwater case study". Journal of Environmental Management. 215: 294–304. doi:10.1016/j.jenvman.2018.03.068. PMID 29574207.
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