This lecture talked generally about the geography of New Zealand and Tasmania, and how the flora interrelates to this. An important beginning of conservation comes from an iconic plant ecologist and conservationist, Dunedin-born Alan Mark. Mark has been very influential in the study of New Zealand’s flora. In 1975 he was appointed Professor of Botany, and in 1978 he was elected a Fellow of the Royal Society of New Zealand. In December 2009, he was made a Knight of the New Zealand Order of Merit, the first such for services to conservation.
New Zealand is predominantly well aged lowland rainforest, and young alpine ranges. It is fairly remote, with the nearest landmass being 800 miles away. 80 million years ago flowering plants were evolving within a background of dominant ancient flora, in the great continent of Gondwanaland. Tree ferns epitomize the tropical character of the flora, which experiences much lower temperatures than those of a true rainforest. The flora is characteristically lush and evergreen.
Zealandia is the name given to the New Zealand continent. It is a nearly submerged continental fragment that sank after breaking away from Australia 60–85 million years ago. Previously this was separated from Antarctica between 85 and 130 million years ago. 93% remains submerged beneath the Pacific Ocean. New Zealand is a only just bigger than the United Kingdom.
Plate tectonics define New Zealand’s character, with the alpine faults creating montane regions growing at 2 cm a year. The north island is made of young mudstone. This island contains 75% of the population.
Climate is influenced heavily by moisture laden winds from the equator, funneled by the rotation of the globe into a horizontal band at 40°latitude. Australia has been and is moving north, offering less protection from these winds. These winds and the topography mean that the west gets large amounts of precipitation, that is, 40 inches per annum. The east, being in the rain shadow, is subsequently much drier.
As mentioned earlier, the precursors of plants are thought to be of Antarctic origin. 93% of alpines are endemic, with the remaining 7% of species being distributed to their furthest extent in Australia and Tasmania. New Zealand has some highly evolved and competitive species.
One such group is from the asteraceae and the daisies, for example leptinella and helichrysum. Others include Ericaceae, notable are dracophyllum, examples of old cushion plants. Also, Epacridaceae and the poaceae (the grasses) that exist within the tree line and up to 300m above. Interest is seen in the discovery of plants in New Zealand, but also in the significance of why certain plants cannot be seen there.
Another conundrum is the predominance of white flowers, which account for 70% of species. Interestingly there is a difference between human perceptions of white and the perception of whites within other spectrums. Flower colour also varies with altitude. Sometimes plants adapt white flowers to aid nighttime pollinators, or to radiate heat back towards the flower to promote development.
New Zealand has a relatively impoverished diversity of invertebrates. For example, only 16 species of butterfly inhabit New Zealand, as opposed to 59 native to the United Kingdom. New Zealand invertebrates have no specialized mouthparts so are just generalized pollinators. It has no social bees. Studies concerning the colour preferences of pollinators and the influence of scent are under resourced. Many species have simple floral structures to aid self pollination, with 23% of species being self fertile.
Many plants have adapted divarication. This is a loss of apical dominance creating plants with scrambling tangled habits. 17 families have this parallel evolution. The Māori came to the islands 900 years ago. New Zealand has flightless birds that are responsible for grazing, some now being extinct. For example, the Moa and the kea. The kea are mountain parrots, responsible for the distribution of fruit bearing plants. Interestingly, geckos and skinks have also been seen to be pollinators. It is suggested that divarication may have occurred to provide a beneficial microclimate within the plants that are more sheltered for pollinators, and also allowing earlier reproduction within flowers.
High altitudes are dominated by cushion flora. Cushion fields are adapted to high wind exposure, low summer temperatures, and frequent freeze/thaw cycles. Some remnant tussocks co habit this environment, but most were killed during the burning of grassland areas by European settlers in the 19th and 20th centuries.
Cushions are often found with wet feet in mineral soil. Some have snow tolerances of 5 moths. There is a wide range of species, often with co dominance. New Zealand has some interesting colloquialisms for its flora. Rock outcrops are colonised by alpine carrots, rouleas, and vegetable sheep, with penwipes in the wider landscape.
Many rock formations are fairly friable, incorporating boulder plains and scree slopes.
Scree palnts make up 25% of alpine specialists. These have 20-30 inches of rain per year. Screes have a 32 degree angle of repose and stability. They have large diurnal temperature ranges over the year, that is from 40°C in summer to -20°C in winter.
Scree plants must tolerate high wind exposure and an active surface layer, and wet compacted cemented gravel beneath. Active rhizomatous roots are one adaptation to these challenges. For example, ranunculus haastii who has become a specialist by exhibiting early flowering, and having distinct rhizomes, often 8” long.
Grey leaves are often characteristic of scree plants, an adaption used to decrease the intensity of light. A species of lobelia, at the other colour extreme, has dark compounds within its leaves to also lessen the intensity of light. Light levels are influenced by the ozone layer thinness above. Combined with clear skies almost 80% of the time, and the 30-40 degree angle of latitude of the sun, light is an important evolutionary force.
Notable endemic plants are:
Aciphylla: 40 species
Celmisia: 70 species
Hebes: 60 species
Beech has become the dominant tree species.
As an aside, Celmisias are often difficult to cultivate due to basal rotting of the crown. Adaptations to mist and rain and associated rotting can be seen in some plants that are able to feed on their own cells as they degrade. Some plants can recycle their own matter faster than others. These are ones adapted better to more regular wetting.