In the “Pikao (or Pingao) the Golden Sand Sedge

Pikao require active sand movement to thrive1,2, and are therefore primarily a foredune species. Pikao only partially traps sand as a result of the density of its foliage1 and the plants morphology1,3 creating active sand dunes; those that still allow a degree of sand movement. This is opposed to the fixed dune profiles created by marram that traps and prevents all sand movement (see photo). These active pikao dominated sand dunes generally create a low undulating hummocky dune profile1.

Marram foredunes. Photo: Megan Duncan.
Marram foredune

A pikao dominated dune system will be characterised by many low sand mounds with gullies scoured out behind1. These gullies transect the watertable (see photo) creating micro-sites that are moist with reduced sand movement (moist sand is heavier and more 'sticky' and therefore requires greater wind velocities to shift the sand)1. These areas also have reduced exposure to salt spray and wind1. This creates an ideal environment for other coastal species to colonise and these areas will often support diverse communities. For this reason, pikao is regarded as an indicator and keystone species for natural biodiversity.

Haystacks wetland pond. Photo: Mike Hilton.
Wetland pond

Because active sand dunes allow some sand movement, they create a more dynamic environment. Therefore, pikao dominated dunes systems change constantly with sand accretion (build up) and erosion, while retaining diversity by constant creation of various ecological niches at different stages of succession.

For more information of coastal geomorphology see Coastal Sand Dunes Form and Function.

References

  1. DOC (1992). Pingao Recovery Plan. Otago Conservancy 1993-1998. Department of Conservation, Dunedin.
      
  2. Bergin, D.O. and Herbert, J. W. (1998). Pingao on Coastal sand dunes. Guidelines for seed collection, propagation and establishment. CDVN Technical Bulletin No. 1. Forest Research Institute, Rotorua.
      
  3. Holland, L. D. (1981). Plants and sand dube development. Ammophila arenaria vs. Desmoschenus spiralis on Kaitorete Barrier. Unpublished Msc thesis, University of Canterbury. Christchurch, New Zealand.
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