New Zealand

A plant sociological survey of tall-tussock grasslands in the Mackenzie country was repeated after an interval of 26-28 years. Changes in physiognomy of the grasslands which have been inferred from earlier studies have been found to be continuing on many sites. A noteworthy feature of most sites has been a reduction in number of indigenous species found. An increase in abundance of Hieracium pilosella or H. praealtum has occurred at most sites.

The vegetation of 10 quadrats from each of 26 sites, in and around the Tongariro National Park, which contained the introduced dwarf shrub, Calluna vulgaris (L.) Hull, was analysed using Reciprocal Averaging and Indicator Species Analysis.

Replacement patterns under buddleia (Buddleja davidii) groves aged between 2 and 17 years were studied in streambeds in the western Ikawhenua Range and in the upper Waioeka catchment, Te Urewera National Park. Height and basal diameter growth followed an exponential pattern, with rapid early growth (0.5 m/year and 1 cm/year respectively), levelling off after 15 years or more. Intense self-thinning occurred in younger stands. Typical forest floor vegetation was developing within 15 years of colonisation by buddleia.

In the past 1000 years New Zealand has experienced a major 'extinction event', losing 40-50% of the avifauna, at least 50% of the frog fauna, and unknown proportions of the lizard and invertebrate faunas. During this period, bird species became extinct at different times and rates depending on the particular aspects of their ecology and life history which made them vulnerable to habitat loss, hunting, predation, and competition for food resources. Three groups of species with different levels of vulnerability are recognised within this event:

The history of the New Zealand biota over the last 7000 years may be divided into three phases. BC 5000 to AD 1000 was a period of comparative ecological stasis. That equilibrium was disrupted between AD 1000 and AD 1800 by the destruction of most of the New Zealand plant-herbivore systems, the co-evolutionary relationship between the plants and the vertebrate herbivores being decoupled by about AD 1400. After AD 1800 new plant-herbivore systems were progressively developed and new ecological relationships forged.

The heathland vegetation of northern New Zealand is usually regarded as a "derived" vegetation type resulting from forest destruction during the Maori and European periods of settlement. Plant species cover-abundance data from sample quadrats in the Far North are analysed using Detrended Correspondence Analysis (DCA) and Two-way Indicator Species Analysis (TWINSPAN) and are then correlated with soil nutrient data. Variations in species composition of heaths appear to be related primarily to soil type. Age since last fire is also important but was not examined in detail in this study.

In late 1986 an official deer hunting regime in the Murchison Mountains, Fiordland, was compared with two commerical aerial hunting regimes in the adjacent Stuart Mountains by measuring the density of deer faecal pellet groups. Overall densities in the Stuart Mountains were twice those in the Murchison Mountains. Official hunting appeared to be more effective than commercial hunting at reducing and controlling deer densities in heavily forested catchments, but not in catchments with less extensive forest cover.

Norway rats were eradicated on bush-covered Hawea Island (9 ha) in Breaksea Sound, using the anticoagulant rodenticide "Talon 50 WB" (brodifacoum). The work was done as a conservation measure and to evaluate the feasibility and costs of eradicating rodents quickly from islands. The 50-100 rats present were eradicated in about two weeks by applying a simple strategy that took full account of the characteristics of the poison, he environment, and the behaviour of the target species.

Mineral element concentrations are presented in leaf and bark material from six woody species growing at a single site on the subantarctic Auckland Islands. Foliar total mineral element concentrations range from 5.81% (Olearia lyallii) to 2.71 % (Dracophyllum longifolium), the lowest concentrations occurring in slow growing species tolerant of nutrient-poor soils.

Increased dieback in Westland rata (Metrosideros umbellata)-kamahi (Weinmannia racemosa) forests has been linked to the build-up of populations of the Australian brush-tailed possum (Trichosurus vulpecula). Within these forests young even-aged stands are observed to be more resilient to dieback than older stands. The effect of possum browsing on individual rata trees was related to the level of defoliation. Trees which had been not or only lightly browsed maintained intact canopies.