Mycorrhizal colonisation of exotic conifers in kānuka and mānuka shrublands

Introduced rodents and possums in New Zealand eat flowers, fruits, seeds and seedlings, but little is known about their impact on forest regeneration. We investigated seedling establishment in exclosures with mesh of two different sizes to exclude (1) possums and (2) possums and rats, at two mainland forest sites (beech–podocarp–broadleaved and second-growth broadleaved–podocarp) near Dunedin. We recorded all new woody seedlings that established over the next 2 years. The number of seedlings with true leaves differed significantly between treatments after 1.5 years at both sites and after 2 years in beech–podocarp–broadleaved forest. This effect was broadly consistent across all species including pepper tree (Pseudowintera colorata), whose adult foliage is unpalatable to possums. Cotyledonous seedlings were relatively ephemeral, but differed significantly in abundance between treatments in second-growth broadleaved–podocarp forest after 1.5 and 2 years. In second rowth broadleaved–podocarp forest, possums were present throughout the study but rats were rare. Numbers of seedlings did not differ significantly between exclosures with different mesh sizes which admitted or excluded rats. In beech–podocarp–broadleaved forest, rats were present periodically throughout the study, but possums may have been scarce during the final 7 months as a result of pest control. At this location, 80 seedlings with true leaves occurred in exclosures that excluded possums and rats, 3.6 times as many as on control plots and 2.1 times as many as in exclosures that deterred only possums. The consequences of these pest impacts on seedling recruitment for forest regeneration must be confirmed in longer-term studies. Exclosures can be effectively used to experimentally separate the impacts of different herbivores on seedling establishment.     

The impact of defoliation on the foliar chemistry of southern rātā (

Brushtail possums (Trichosurus vulpecula) tend to eat young canopy foliage in southern rätä (Metrosideros umbellata), and browsing tends to be concentrated on only a few trees. Samples collected as part of an artificial defoliation experiment were analysed for NPK (nitrogen, phosphorus, and potassium), carbohydrate, and polyphenolic concentrations to determine whether changes in foliar chemistry associated with defoliation provide an explanation for these patterns of browsing. In non-defoliated trees, NPK concentrations were highest in young leaves and declined with age, while concentrations of carbohydrates and polyphenolics were independent of leaf age. Nitrogen, phosphorus and polyphenolic concentrations were consistently higher in canopy (sun) versus subcanopy (shade) foliage regardless of leaf age, a trend that was reversed for potassium. Partial (50%) defoliation had little effect on foliar chemistry, regardless of its timing. Total (100%) defoliation stimulated NPK concentrations and depressed condensed tannin concentrations of new foliage produced by the surviving shoots. These results suggest that brushtail possums may focus their feeding on only a few trees because of nutritional changes to leaves as a result of browsing.     

Tūhoe Tuawhenua mātauranga of kererū (

Indigenous peoples? knowledge on changes in wildlife populations and explanations for these changes can inform current conservation and wildlife management systems. In this study, Tūhoe Tuawhenua interviewees provided mātauranga (traditional knowledge) about a repertoire of visual (e.g. decreasing flock size), audible (e.g. less noise from kererū in the forest canopy), and harvest-related (e.g. steep decline in harvests since the 1950) indicators used to assess kererū (New Zealand pigeon; Hemiphaga novaeseelandiae novaeseelandiae) abundance and condition in Te Urewera, New Zealand over the last 100 years. Metaphorical explanations for the decline in kererū included the loss of mana (authority and prestige) by the iwi (tribe) over the kererū and forest, and the retraction of the kererū?s mauri (life force) by Tāne Mahuta (God of the Forest). Interviewees reported that predation and interspecific competition with introduced species, variability in food supply, and loss of habitat were the principal biophysical mechanisms to have caused declines in kererū abundance. Long-term qualitative monitoring by Tūhoe Tuawhenua has the potential to guide the restoration of kererū and wider environmental management in Te Urewera. Allowing iwi the self-determination to make management decisions according to their mātauranga (or science, if desired) is likely to lead to greater application of results and altered practices where required for sustainability.     

Volume 257 (1993), author index

Volume 271 (1993), author index     

Secondary forest succession differs through naturalised gorse and native kānuka near Wellington and Nelson

The dominant native woody species forming early-successional vegetation on formerly forested sites in lowland New Zealand were kānuka (Kunzea ericoides) and mānuka (Leptospermum scoparium) (Myrtaceae). These have been replaced extensively by gorse (Ulex europaeus, Fabaceae), a naturalised species in New Zealand. Because gorse typically gives way to native broadleaved (angiosperm) forest in about 30 years, it is often considered desirable for facilitating native forest restoration. We tested three hypotheses, derived from the New Zealand literature, on gorse and kānuka: (1) kānuka stands have a different species composition and greater species richness than gorse stands at comparable successional stages; (2) differences between gorse and kānuka stands do not lessen over time; and (3) several native plant taxa are absent from or less common in gorse than in kānuka stands. We sampled 48 scrub or low-forest sites in two regions, Wellington and Nelson. Sites were classified into one of four predefined categories – young gorse, young kānuka, old gorse, old kānuka – based on canopy height of the succession and the dominant early-successional woody species. Few characteristics of the sites and surrounding landscapes differed significantly among site categories, and none consistently across regions. The vegetation composition of gorse and kānuka and their immediate successors differed in both regions, mainly in native woody species. Species richness was often lower in gorse and there were fewer smallleaved shrubs and orchids in gorse. Persistent differences at the older sites suggest the successional trajectories will not converge in the immediate future; gorse leads to different forest from that developed through kānuka. Gorse-dominated succession is therefore not a direct substitute for native successions. We suggest areas of early native succession should be preserved, and initiated in landscapes where successions are dominated by gorse or other naturalised shrubs.