disturbance

Vegetation on the edge: a gradient analysis of the riparian zone, Poerua River, New Zealand

Forest vegetation patterns alongside the Poerua River, south Westland, were studied to determine whether a distinct riparian community could be defined either immediately adjacent to the river, or out to the limit of overbank flooding. Ten randomly located 100 m transects were established perpendicular to the river at each of two sites. Ground cover of alluvial sediment indicated that annual overbank flooding occurred up to 20 m into the forest (the flood zone).

An experimental study of the impacts of understorey forest vegetation and herbivory by red deer and rodents on seedling establishment and species composition in Waitutu Forest, New Zealand

Introduced mammalian herbivores are changing the structure and composition of New Zealand’s forest ecosystems and may modify forest succession after natural disturbances. We studied how introduced ungulates (red deer and feral pigs) and rodents (rats and house mice) affected the rate of recovery (i.e. the engineering resilience) of the forest understorey following artificial disturbance.

Vegetation change after artificial disturbance in an alpine Chionchloa pallens grassland in New Zealand

We describe the colonisation of artificially created gaps in an alpine grassland dominated by Chionochloa pallens. Twelve years after their creation, the 50 cm _ 50 cm gaps supported a distinctive vegetation composed of a mixture of perennial forbs, grasses and mosses. Three species (Bryum sp., Epilobium alsinoides and Plantago novae-zelandiae) were recorded only in the gaps.

Species richness of indigenous beetles in restored plant communities on Matiu-Somes Island, Wellington Harbour, New Zealand

Previous studies have shown that indigenous beetle diversity reflects indigenous plant diversity in modified and remnant habitats. This study examines the indigenous: introduced relationship at a locality where degraded pasture has been progressively revegetated. Pitfall traps were used to collect beetles from three revegetated sites of different ages (5, 17 and 100 years) and in a coastal Muehlenbeckia habitat on Matiu- Somes Island (25 ha), Wellington Harbour, New Zealand. A total of 78 morphospecies were found over 12 months.

A pragmatic approach to characterising insect communities in New Zealand: Malaise trapped beetles

Insect communities from a range of successional vegetation stages on the central North Island volcanic plateau were characterised and compared using Malaise trapped beetle samples. Results were derived from sampling series conducted in a total of ten sites over three separate summers. Divisive classification successfully grouped samples according to four main habitat types despite temporal and spatial separation of samples within these groups. A four-week period in early summer was found to be optimum for sample discrimination according to the main vegetation types.

Liane distribution within native forest remnants in two regions of the South Island, New Zealand

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.

Spider density and diversity in relation to disturbance in agroecosystems in New Zealand, with a comparison to England

Spider assemblages were sampled by quantitative sampling in pasture and arable habitats under different management regimes in the lower North Island of New Zealand. Density and species diversity increased with decreasing frequency and/or intensity of disturbance from two species and 1.8 individuals per m in wheat to 16 species and 130 indiv. per m in an abandoned, ungrazed pasture. The spider fauna was dominated by introduced species of money spiders (Linyphiidae). The most abundant species, Lepthyphantes tenuis, is also the most abundant one in British cultivated habitats.

Introduced species: A significant component of human-caused global change

Biological invasions are a widespread and significant component of human-caused global environmental change. The extent of invasions of oceanic islands, and their consequences for native biological diversity, have long been recognized. However, invasions of continental regions also are substantial. For example, more than 2,000 species of alien plants are established in the continental United States. These invasions represent a human-caused breakdown of the regional distinctiveness of Earth's flora and fauna—a substantial global change in and of itself.

Modelling relationships between environment and canopy composition in secondary vegetation in central North Island, New Zealand

Relationships between composition of secondary vegetation and environment were studied in central North Island, New Zealand. A classification procedure was used to identify broad compositional groups which included forest, broadleaved scrub, shrub-fernland, sclerophyllous scrub and shrubland, and tussock-shrubland. Generalised additive models (GAMs) were used to examine relationships between species' distributions and mean annual temperature and rainfall, stand age, distance from intact forest, slope, topography, and drainage.

Predicting the impacts of biological and physical disturbances: Does theoretical ecology hold any answers?

Biological and physical disturbance has had a severe impact on New Zealand's endemic flora and fauna. Along with the lessons of the past, predicting the sensitivity of communities to disturbance in the future may help direct more attention to those communities with a greater need for preservation (i.e., a lower ability to recover from any such disturbances). In theory it is possible to measure the resilience (or local stability) of a community by constructing a matrix to describe that community and then examining its eigenvalues.

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