New Zealand has a unique opportunity to reshape the future of 1.2 million hectares, or 5% of the country. Since 1990, land clearance and development in the South Island high country have removed large areas of native vegetation, destroying already tenuous endemic species populations, and rare and threatened ecosystems. Important ecosystems and ecological values have been subtly or dramatically degraded through tenure review, discretionary consents, and invasions of plant and animal pests.
The effect of different densities of tussocks (Festuca novae-zelandiae, Poa laevis) in short tussock grassland associations was studied using transplanted cocksfoot (Dactylis glomerate) seedlings as indicators of inter-tussock plant growth. The dense tussock associations considerably modified the microclimate, reduced frost damage and initially promoted cocksfoot growth. Sparse tussock associations did not generally promote cocksfoot growth unless plants were near the tussock base and sheltered from the prevailing wind
The Black Rock Scientific Reserve has been set aside to preserve an area of low altitude snow tussock grassland. The reserve consists of gently rolling ridges covered in a narrow-leaved snow tussock (Chionochloa rigida) association, substantially intact or in various stages of degradation, and shallow gullies containing Sphagnum bog and minor grassland communities. To enable changes in the snow tussock association to be studied, four one hectare permanent quadrats have been established and sampled by Scott's height frequency method.
The texture of a plant community, i.e. the range of values in functional characters across the species present, integrates the ecological and evolutionary processes that have led to that communityÕs present species composition. The idealistic prediction of ecological theory is that selection for co-adaptation and competitive sorting will lead to convergence in texture between different patches of vegetation with the same environment. This concept has previously been applied at the continental scale; here it is applied for the first time at a within community scale.
Changes in the vegetation of Flat Top Hill, a highly modified conservation area in semi;arid Central Otago, New Zealand, are described four years after the cessation of sheep and rabbit grazing. Unusually moist weather conditions coincide with the four-year period of change in response to the cessation of grazing. Between 1993 and 1997, the average richness and diversity (H') of species increased, and the average proportion of native species decreased significantly.
Predictions from three conceptual models of the dynamics of semi-arid vegetation (Clementsian succession, alternative stable states and annuation/pulse phenomena) are used to review the available evidence on changes in the vegetation of semi- arid lowland Central Otago, New Zealand. Evidence is presented from Central Otago that corresponds with Clementsian succession and with annuation/pulse phenomena, although there is so far no formal evidence of alternative stable states.
The Humped-back theory of plant species richness, a theory related to Grime's C-S-R 'triangular' model, has been widely discussed, and some evidence has been claimed in support of it. The theory suggests that species richness is maximal at intermediate levels of productivity, i.e., at intermediate positions on a stress/favourability gradient. We sought evidence for the theory from 90 stands of native podocarp/broadleaved and beech forest in the Coastal Otago region, with an adjustment made for the effect of stand area on species richness.
The takahe (Notornis mantelli), an endangered rail once widely distributed through New Zealand, had become restricted to Fiordland, and possibly Nelson and the Ruahine Ranges, by European times. Two contentious viewpoints have been advanced to explain the decline: climate and vegetational changes in the late Pleistocene and Holocene; and ecological changes induced by early Polynesians. These theories are examined in relation to the habitat requirements of takahe in its present restricted range, the historical and sub-fossil record, and the possible age of the sub-fossils.
Understanding the factors that drive population persistence and growth is fundamental to both conservation management and evolutionary biology. Internal (maternal) and external (environmental) factors can affect female reproductive output, and in oviparous reptiles both may strongly influence offspring phenotype and quality. However, the link between these effects, their importance for reproductive output and offspring characteristics of live-bearing lizards, and whether population declines are linked to these factors in modified versus native habitats are unknown.