A comparison of the seed ecology of Desmoschoenus spiralis and Ammophila arenaria Thesis
- Author
- Pope, P.
- Year
- 2005
- Journal / Source
- Unpublished MSc
- Publisher / Organisation
- University of Otago
- Month
- November
- Pages
- 156
- Species
- Ammophila arenaria, marram, marram grass, Ficinia spiralis, pingao, pikio, golden sand sedge, Desmoschoenus spiralis
- Summary
- The introduction of marram grass (Ammophila arenaria) to the New Zealand dune ecosystem has brought about rapid changes to dune morphology and plant assemblages . The native sand binder Pingao (Desmoschoenus spiralis) has been widely displaced by the invasive A.arenaria in the dune landscape in New Zealand. However, there is very little known about the seed ecology of Ammophila in New Zealand conditions, nor from other overseas research. Seed ecology research for Desmoschoenus has been limited to the understanding of "best practices" for the harvesting of seed and raising plants in restorative efforts in affected dunelands. Dispersal studies of A. arenaria and D. spiralis have not been undertaken, and this has left a gap in our ecological understanding of the invader and competitive plant paradigm in the New Zealand coastal dune context. The seeds from both species were collected during the 2004 and 2005 summer periods for eight weeks from Toko Mouth in South Otago. The Toko Mouth site was monitored for seasonal changes in sand movement, wind regime, temperature, and rainfall during the study period. In 2004, which was hot and dry during the pollination and seed maturation periods, 40.08% of fresh A. arenaria were germinable, whereas, only 1.56% of D. spiralis produced germinable seeds, and exhibited possible drought stress, through premature seed dispersal, and pollination failure due to the prolonged hot weather. The 2005 season saw heavy rain during anthesis and seed maturation, and only 15.90% of fresh A. arenaria seeds were germinable, but D. spiralis germination increased to 11.00%. D. spiralis flowers earlier than A. arenaria and is more sensitive to drought. The low viability of seed in 2004 appears due to possible drought stress triggering premature seed dispersal. Pollination success may also have been low. Reduced seed viability in A.arenaria in 2005 appears to relate to cold wet conditions during its later flowering and seed maturation period. Environmental conditions during the different flowering times between the two species appears likely to effect pollination and seed maturation, and this was observed in the subsequent increase or decrease in the production of germinable seeds.