growth

Seedlings of five native tussock species grown in the glasshouse on mountain subsoil showed outstanding responses to nitrogen and phosphorus fertiliser in combination. The most vigorous species was silver tussock but this produced less dry matter than an introduced grass, Yorkshire fog, grown on the same soil. Tussocks in general responded positively to applications of magnesium and potassium but growth was depressed by lime.

The ecological impacts of Hydrodictyon reticulatum blooms (1989-94) were studied at Lake Aniwhenua (a constructed lake) in North Island, New Zealand by collating fish, invertebrate and macrophyte data collected towards the end of a four year bloom period and following its decline. Hydrodictyon reticulatum had some localised impacts on the biota of the lake. Some macrophyte beds were smothered to the extent that they collapsed and disappeared, and dense compacted accumulations of H. reticulatum caused localised anoxic conditions while it decayed.

We analysed biomass allocation of Pleurophyllum speciosum (Asteraceae) and Anisotome latifolia (Apiaceae) to explore the 'megaherb' phenomenon, the apparent importance of large-leaved, colourful forbs on southern oceanic offshore islands. The two species had similar shoot dry weights, with high leaf:stem ratios. Even within the megaherb form there are differences in shoot allocations, with Pleurophyllum investing more biomass in rhizome than foliage, compared with Anisotome.

To determine the susceptibility of different forest types to lianes, and to investigate which ecological factors are limiting for lianes, a field survey covering 28 naturally forested sites in Golden Bay (Northwest Nelson) and on Banks Peninsula (Canterbury) was carried out. Results from Detrended Canonical Correspondence Analysis of liane species abundance data in relation to tree and shrub species abundance data and abiotic site variables, showed that the liane community composition was highly correlated with the composition of the tree and shrub community.

Heteroblasty, changes in vegetative phenotype during ontogeny, is unusually common in the New Zealand flora. Some feature(s) unique to the New Zealand situation must have influenced the evolution of this strategy. Similarities were examined between the ontogenetic changes in phenotype and growth strategy in Elaeocarpus hookerianus, Carpodetus serratus and Pseudopanax crassifolius. Variation in hypothesised light capture efficiency of juvenile and adult forms can be related to changes in the light environment that these growth forms experience.

Flowering intensity and plant size were monitored in 155 Festuca novae-zelandiae individuals over four years to determine if trade-offs exist between inflorescence production and vegetative growth, and between inflorescence production in different years. Less than half of the population flowered in any one year, 36% of individuals did not flower at all, and only 17% flowered in all four years of the study. Mean number of inflorescences per individual per year varied from 1.54 to 5.53 (maximum = 85).

Over five years from November 1982 to November 1987, we examined 395 mice collected from unlogged and logged native forest and from exotic forest at Pureora Forest Park, in the central North Island of New Zealand. Sex ratio, litter size, and breeding effort (pregnancy rate in females, proportion of males with visible tubules) were similar in all samples.

Previous work in New Zealand has shewn that genetic variation within populations of Agrostis capillaris can be comparable to that between populations, even between populations over a very wide environmental range. To determine whether this reflects the recent advent of A. capillaris in New Zealand, with a small founding gene pool and a short time for ecotypic differentiation, populations from a comparable range of environments were sampled randomly in the same way in Britain.

Variation in seedling growth and form between provenances of Podocarpus totara from 42 sites throughout New Zealand was investigated. Seedlings were grown for three years under uniform nursery conditions. There were significant differences between provenances in height growth in the first three years after sowing. Early growth was highly correlated with germination rate after sowing. In the third year, growth followed a different pattern and was negatively correlated with provenance latitude, i.e., provenances from southern latitudes grew more slowly than those from further north.

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.