Mark C. Smale

Dynamics of upland podocarp/broadleaved forest on Mamaku Plateau, central North Island, New Zealand.

Forest composition was examined on one hectare of upland Dacrydium cupressinum‐Prumnopitys taxifolia/Weinmannia racemosa‐Beilschmiedia tawa forest on south Mamaku Plateau, central North Island, New Zealand, a site of catastrophic volcanic disturbance c 1900 years ago The phasic model (gap, building, mature) of the forest growth cycle was used Mean age of sampled stems differed significantly between gap (13 yr), building‐phase (68 yr), and mature forest (252 yr), which comprised 10%, 50%, and 40% respectively of the area and persisted on average for 20 yr (gaps) and 60 yr (building phase) ‘Expanded’ gaps averaged 0 008 ha in size Tree ferns ‐ mostly Dicksoma squarrosa and Cyathea smithn ‐ were numerically dominant throughout, and dominated basal area in younger ( 80 yr) forest Current diameter growth rates among broadleaved species followed the ranking Griselinia littoralis, Elaeocarpus dentatus>B tawa>Ixerba brexioides, W racemosa, and were si...

Secondary woody vegetation patterns in New Zealand’s South Island dryland zone

Abstract Can New Zealand’s indigenous dryland ecosystems be rehabilitated by facilitating inherent successional tendencies to enhance development of indigenous-dominated and often woody communities in the long term? Here, we describe the geographic distribution of woody communities of New Zealand’s South Island drylands to generate hypotheses about successional trajectories to future vegetation states. Presences and absences of woody species in 3880 vegetation plots collated from past surveys were used to predict species potential distributions across drylands. Separate models and spatial predictions were built for each of four classes of woody richness, which were used as surrogates for successional stages. Woody species richness increased significantly from grassland to shrubland and from shrubland to forest cover, and trends in species traits also suggest richness class was related with successional stage. Indigenous woody species outnumbered exotic species in all richness classes. Assuming richness classes represent temporal progressions, our results suggest relatively homogeneous early-successional woody associations succeed to a divergent array of woody associations in different environments. Growth forms of species in our predicted associations suggest transitions from grassland to tall, tree-rich forests in northern and coastal drylands, and to liane-rich open or lightcanopied shrubland, woodland, or low forest in more severe inland environments. These putative communities are novel in species composition but physiognomically broadly similar to pre-settlement analogues. Especially in severe inland environments, unassisted transitions from grassland to indigenousdominated late-successional woody communities may depend on the exclusion of tall exotic trees, Scotch broom, and gorse in early succession.

Dynamics of upland conifer/broadleaved forest at Waihaha, central North Island, New Zealand

Abstract Regeneration in upland Podocarpus hallii‐Prumnopitysferruginea/Quintinia serrata‐Weinmannia racemosa forest, central North Island, New Zealand, was sampled in the three phases of the forest growth cycle. Mean age, determined from the largest stem present, differed significantly between gaps (13 yr), building‐phase (58 yr), and mature forest (221 yr), which comprised 8, 28, and 65%, respectively, of the forest area. Current diameter growth rates among species (Griselinia littoralis > W. racemosa, Q. serrata > P. hallii, P. ferruginea) did not differ between phases. Canopy P. hallii sampled were up to 500 yr old and P. ferruginea were 550 yr old. Broadleaved species were all younger on average (<250 yr). Three replacement strategies among major species involve establishment in different stages of the forest growth cycle, reflecting specific shade tolerances. Relatively intolerant W. racemosa and G. littoralis establish solely in gaps (gap‐phase replacement), Dacrydium cupressinum mostly in gaps. More tolerant P. ferruginea and Q. serrata establish in gaps and building‐phase forest. Shade‐tolerant P. hallii, Nestegis cunninghamii, Elaeocarpus hookerianus, Pseudowintera colorata, and Neomyrtus pedunculata establish throughout the forest growth cycle, Myrsine salicina only in later stages. A conifer “regeneration gap” is locally evident in relatively shade‐intolerant and fertility‐demanding Prumnopitys taxifolia. Basal area recovery after gap formation is slow in relation to overall basal area here and in other forests in the region, and may result from a relatively long history of browsing by introduced mammals.

Structure and dynamics of kanuka (Kunzea ericoides var. ericoides) heaths on sand dunes in Bay of Plenty, New Zealand

Abstract The structure, composition, and dynamics of a rare coastal community, kanuka (Kunzea ericoides var. ericoides) shrub- and tree-heaths on sand dunes, were studied on Whale Island and at Thornton, in Bay of Plenty. Both multi-stemmed, semi-prostrate and erect kanuka is present in virtually pure stands on largely unconsolidated dunes on Whale Island, and multi-stemmed, semi-prostrate kanuka in nearly pure stands on consolidated dunes at Thornton. This and other studies indicate that lack of competition (i.e. establishment at low densities) is primarily responsible for the multi-stemmed habit, but interacting environmental (exposure, drought) and genetic factors may also play a part. All communities are floristically poor compared with other woody communities in New Zealand, with only widespread species present and a large proportion of adventives. Mean annual diameter growth was 3.0 mm/yr at Whale Island and 2.8 mm/yr at Thornton; mean annual height growth ranged from 29.8 cm/yr in younger stands (6...

Resilience to fire of Dracophyllum subulatum (Ericaceae) frost flat heathland, a rare ecosystem in central North Island, New Zealand

Abstract We measured secondary succession in permanent plots for 15 years after a lightning-induced fire in a 90-year-old frost flat heathland dominated by Dracophyllum subulatum at Rangitaiki, North Island, New Zealand. We placed this succession in the longer term context provided by earlier published data from the same site. Species re-establishment was rapid, with all of the consistently present species of mature heathland present by 15 years. The new Dracophyllum population has reached its pre-burn density, although cover is still minimal. Vascular plant cover began to decline 11 years after fire, but non-vascular cover continued to increase. Poa cita declined dramatically in abundance after 11 years. Earlier studies at the site demonstrate that nearly the entire species complement of mature heathland is present by 25 years, indication of a direct succession. With substantial resilience to fire, frost flat heathland is a fire-adapted ecosystem in a country where such ecosystems are rare.

Diameter growth rates of tawa (Beilschmiedia tawa) across the middle North Island, New Zealand – implications for sustainable forest management

BackgroundTawa (Beilschmiedia tawa (A. Cunn.) Kirk) remains a minor but significant hardwood timber in New Zealand, currently sourced from tawa-dominant forest on freehold and Maori land where selective harvesting under sustainable management plans is permitted. Sustainable management plans require reliable tree growth estimates, which are used to calculate annual volume increment and harvest levels. The aims of this study were to model the relationship between diameter growth rate and tree size using existing data, and to determine the influences of within-stand competition, local climate and soil parent material on growth rates.MethodsA dataset was compiled on the diameter growth rates of nearly 1800 trees from a wide range of published and unpublished sources for the middle North Island. Non-linear quantile regressions were used to model average growth and growth of the fastest 25% of stems, termed rapid growth.ResultsAcross the middle North Island, average growth of a 400 mm DBH (diameter at breast height) tree was 1.8 mm year−1 and rapid growth was 2.8 mm year−1. Overall, the model accounted for 12% of the total variation in growth rate. The effect of size on diameter growth rate was modest but positive. Within-stand competition reduced tawa diameter growth rates, particularly when basal area exceeded 100 m2 ha−1. Also, climate (winter minimum temperature and annual vapour pressure deficit) had little influence on growth rates and explained <2% of total variation in stem growth. Soil parent material strongly influenced tawa growth rates and explained >10% of variation in stem growth. The fastest growth rates were on soils derived from Tertiary mudstone in inland Taranaki.ConclusionsMost of the existing data on growth rates of tawa are for trees growing on volcanic substrates. This means that the markedly faster growth on some sedimentary rather than volcanic substrates suggests that growth rates and volume increment may be underestimated for many sites in the middle North Island beyond the Volcanic Plateau. A growth dataset more representative of the range of substrates occupied by tawa is needed for management plans elsewhere in the North Island.

A classification of the geothermal vegetation of the Taupō Volcanic Zone, New Zealand

ABSTRACT We undertook stratified random sampling of vegetation, soil chemical fertility and subsurface soil temperature at 38 sites on 15 geothermal fields in the Taupō Volcanic Zone, central North Island, New Zealand, to develop a quantitative classification of geothermal vegetation types and to identify the main environmental drivers of vegetation composition. We implemented this with the fuzzy classification framework of noise clustering. Gradients in composition were derived using Detrended Correspondence Analysis ordination and related to soil physical and chemical parameters using correlation. Of 166 plant species recorded, only seven native species were present in > 20% of plots and only four adventive species in > 5% of plots. Subsurface soil temperatures ranged from ambient (7 °C) to near-boiling (98.5 °C). Classification identified 16 vegetation associations, almost all dominated by indigenous species and unique to geothermal fields. Subsurface soil temperature was the main factor controlling vegetation composition; soil chemistry was less important.

Protecting the Forest from Introduced Herbivores

This chapter describes the arrival of introduced browsing mammals (red deer, feral goats and cattle, and possums) in Pureora Forest Park (PFP), the long-term damage to native vegetation they cause, and the persistent dilemmas surrounding the use of 1080 poison to protect the forest. PFP has developed a new role as a significant open-air laboratory for field research, so this chapter summarises some of the important studies conducted on the fauna and flora of the park, especially on the development of ways to protect them.