Ecology and management of South Island beech forests: Insects damaging beech (Nothofagus) forests.
The main purpose of biological reserves in the northern West Coast and western Southland beech forest management regions and some factors affecting their selection are described. Their total area is about 30,000 ha in the West Coast region and about 5,000 ha in western Southland (excluding Waitutu State Forest).
The Forest Service proposals for fuller use of some South Island beech forests have focussed unparalleled attention on the management of indigenous forests; and the fact that the New Zealand Ecological Society has conducted a symposium on the ecology of beech forests is a manifestation of this widespread interest. This paper is an attempt to place the proposals directly before ecologists so that final evaluation can follow a reasonably complete understanding.
We quantified brushtail possum (Trichosurus vulpecula) diet in a mixed Nothofagus fusca-N. menziesii forest in north Westland. Diet comprised 49 food items of which four (Aristotelia serrata, Muehlenbeckia australis and Weinmannia racemosa foliage, and W. racemosa flowers) contributed 68%. The canopy dominant Nothofagus species were a minor diet component (<1%), while wood, fungi and bark were a small but consistent part of diet (10.1%).
The effect of honeydew density on arthropod community structure was investigated in the Nothofagus forest of Nelson Lakes National Park, New Zealand. Pitfall trapping revealed no community response to honeydew density, whereas sticky trapping showed the community composition of trunk-dwelling arthropods varied along a honeydew gradient. Mycetophilidae, Staphylinidae, Pteromalidae and Margarodidae were classified as high honeydew biased, while Diapriidae and Platygasteridae were non-honeydew biased.
Stoat (Mustela erminea) density was estimated by live-trapping in a South Island Nothofagus forest, New Zealand, at 8-9 (Jan/Feb 1996) and 15-16 (Aug/Sep 1996) month intervals after significant beech seedfall in autumn 1995. Absolute densities were 4.2 stoats per km² (2.9-7.7 stoats per km², 95% confidence intervals) in Jan;Feb 1996 and 2.5 stoats per km² (2.1-3.5 stoats per km²) in Aug/Sep 1996. Trappability of stoats increased in the latter sampling period, probably because mice (Mus musculus) had become extremely scarce.
We studied the ecology of a high-density population of stoats in Fiordland, New Zealand, in the summer and autumn of 1990-91 following a Nothofagus seeding in 1990. Results are compared with findings from the same area in 1991-92, a period of lower stoat density. In the high-density year, minimum home ranges (revealed by radio-tracking) of four females averaged 69 ha and those of three males 93 ha; range lengths averaged 1.3 km and 2.5 km respectively. Neither difference was statistically significant.
Home range and diet of stoats inhabiting beech forest were examined by trapping and radio-tracking. Eleven stoats (6 female, 5 male) were fitted with radio-transmitters. Minimum home ranges of five females averaged 124 ± 21 ha and of four males 206 ± 73 ha. Range lengths of females averaged 2.3 ± 0.3 km and of males 4.0 ± 0.9 km. These differences were not statistically significant. Adult female stoats appeared to have mutually exclusive home ranges. Two females and one male had home ranges that were bisected by the Eglinton River.
Prey collected by Vespula vulgaris and V. germanica were sampled by intercepting foragers returning to nests at two sites in scrubland-pasture near Hamilton. About 12% of returning foragers carried animal prey and 5% carried wood pulp. The remaining 83% carried no external load. The most common prey item for both species was Diptera, followed by Lepidoptera and Araneae (spiders). Even in similar habitats the two species collected different prey, with V. germanica collecting more Diptera and V. vulgaris more Lepidoptera.
Honeydew is produced by a scale insect (Ultracoelostoma assimile, Margarodidae) in some Nothofagus forests of South Island, New Zealand. The quantity of honeydew present and its sugar concentration varies through the year. Honeydew is a valuable resource for bellbirds (Anthornis melanura), tuis (Prosthemadera novaesealandiae) and silvereyes (Zosterops lateralis). Bellbirds and tuis were commoner in forests with more honeydew. Bell- birds spent more time feeding on honeydew when its sugar concentration was low.