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    Island biogeography : a study of habitat islands of mountain beech forest (Nothofagus solandri, var. cliffortioides) in Tongariro National Park : a thesis presented in partial fulfilment of the requirement for the degree of Master of Science in Zoology at Massey University
    (Massey University, 1982) Seden, Moyra
    MacArthur and Wilson's (1967) model for island biogeography is examined, particularly with regard to the proposed species-area relationship. The first chapter includes a consideration of the theoretical background. Nine habitat islands and corresponding mainland regions of similar area were selected. All the sites possess a canopy of mountain beech trees, (Nothofagus solandri var. cliffortioides), and are located in the western segment of Tongariro National Park. Plants and litter animals were sampled from within these sites to determine the possible relationship between species and area. Forest plant species numbers as well as proportions, assessed using a modification of the Point-centred quarter method, revealed a statistically significant species-area relationship. Litter Crustacea collected in one thousandth of a square metre core samples, and removed from cores by wet extraction, show a gradation in habitat preference, hence a species-area relationship cannot be determined. A wide range of animals collected in pitfall traps appear also not to produce a significant species-area relationship. Possible reasons for the obscurity of such a relationship are considered. An overall assessment of the information gathered in the light of island biogeographic theory is presented, and some more recent thought on the causal explanations for the species-area relationship are discussed.
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    Gap regeneration and forest dynamics in a lowland podocarp-broadleaved forest remnant, Keeble's Bush, Manawatu : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science at Massey University
    (Massey University, 1996) Whaley, Kathryn Janet
    Gap phase regeneration and forest dynamics were investigated in a lowland podocarp-broadleaved forest remnant, Keeble's Bush, Manawatu, in order to assess its ecological integrity. To this end the seed rain (i.e., viability and diversity of fresh seed input), seedling diversity and survival, and soil seed bank composition were all assessed. A total of 40 different species were trapped in the seed rain, contributing a total of 2398 seeds/m2/yr. A high coefficient of variation for seed number and diversity was recorded between traps, illustrating the spatial heterogeneity of the seed rain. Strong seasonal patterns were recorded in the fruiting phenology of the species trapped. A lack of red-arilled viable seeds suggested that 1992 was not a mast year for rimu. Most of the seeds likely originated from individuals less than 50 m from the seed traps, reflecting the paucity of native frugivores to disperse seeds further, particularly those less than 10 mm in size. Virtually all the adventive species trapped were herbaceous with most having wind dispersed seeds. All of them were local in origin; i.e., already present within the gaps at the time of trapping. The total number of seedlings, and the seedling densities in the two gap sites studied were very similar in both 1992 and 1993. Despite the flux of seedlings into and out of the populations at each site seedling numbers remained stable. Species diversity and number of species/m2, varied between gaps, with the species population in Gap Two species poor compared with that in Gap One (10 species were shared, with 9 exclusive to Gap One, and 3 present only in Gap Two). Seedling mortality in Gap One fitted the well documented phenomenon of huge mortality during the initial period of establishment and growth. Seedlings in Gap Two, however, showed equal probability of mortality in all height classes. Competition (both above and below ground), browsing by exotic herbivores, drought stress, and litter burial all likely contribute to seedling mortality. The results suggest that the seedling populations in gaps differ between those gaps within the forest interior (Gap One), and those at the forest margin (Gap Two). Seedlings from 36 species emerged and were identified from the sampled soil seed bank, contributing a total of 821 seedlings. Herbs were the most important life-form in the soil seed bank, making up 77.5% of the total seedlings. Adventive species accounted for 16 of the 36 species, 14 of which were herbaceous. Seedlings of primary forest trees contributed only 1.2% of the seedlings, and emerged from only three of the eight sampling sites. Germination was rapid with the first seedlings emerging from the soil samples within seven days of the start of the experiment; over 86% of the seedlings emerged within the first month. Adventive species dominated the seedlings emerging for the first five weeks. The number of species and individuals which germinated decreased with soil sample depth. The highest number of seedlings and species occurred in the top 2 cm of soil, with 80% of the seedlings within the top 4 cm. The soil seed banks of the gaps were more diverse, with greater numbers of species and seedlings, compared with sites beneath intact canopy. The results of the longevity experiment suggest tawa and titoki may maintain a short-term transient seed bank, if the seeds are buried rapidly. Kawakawa seeds appear to suffer high predation/decomposition and are likely to last for a shorter period in the soil. Radiata pine does not maintain a seed bank in the soil. Management implications for Keeble's Bush were discussed, and directions for future research suggested.
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    Structure and dynamics of alluvial forest in the Pohangina Valley : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Botany
    (Massey University, 1984) Lusk, Christopher Harley
    Species' population structures and replacement patterns are quantitatively described from intensive sampling of forest on alluvial surfaces of three ages. Observations and evidence from a range of other sites are incorporated to assist in tracing the development of forest on alluvial surfaces of the study area, and in examining factors influencing this development. Cockayne's postulate that: " ... the most important principle underlying succession in New Zealand forests is the relation of the different species to light." is investigated with respect to the study area. A Relatively even-aged totara-dominant dense podocarp stands have developed on floodplain surfaces made available by progressive channel down-cutting and lateral migrations. On older surfaces these first generation stands are replaced by forests dominated principally by the angiosperms tawa, titoki and mahoe. On a terrace surface c.2,000 - 3,000 years old, forest variation appears attributable to dynamic processes as well as differences in site drainage. On mesic sites tall tawa-dominant forest prevails, although recent windthrows have produced low groves of mahoe and other small angiosperms, and also apparently stimulated some podocarp regeneration. On xeric terrace sites, titoki and rewarewa dominate the canopy. Low densities of podocarps on the mesic terrace sites attest to very sparse regeneration after the demise of the dense first generation stands. The discontinuous size class distributions of podocarp species on these sites appear at least partially attributable tc speradic regeneration following major windthrows. Podocarp densities are higher on the terrace xeric sites, regeneration of matai and totara apparently being favoured by the lower vegetation density and higher understorey light levels. On these sites matai shows an all - sized stable population structure, and a cyclic discontinuous replacement of totara seems possible. Seedling growth experiments showed both totara and kahikatea to be less shade-tolerant than two large angiosperm species (titoki and pukatea, respectively) typically seen to be replacing them in old growth forests on their respective sites. Except on the terrace xeric sites, light levels measured in forest understoreys were mainly below the compensation point experimentally estimated for totara seedlings. These findings confirm that regeneration of kahikatea and especially totara is likely to be very infrequent in old growth forest on these sites. Cockayne's postulate does not completely explain species establishment patterns within these forests. However, the findings of this study lend support to his interpretation of "light relations" as the primary influence on successional trends, and suggest that regeneration of kahikatea and especially totara is likely to be largely disturbance-dependent.
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    The effects of restoration on the structure and function of litter invertebrate communities in New Zealand native forest remnants : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Costall, Jessica Anne
    Much of New Zealand‘s remaining lowland forest exists as small, often degraded and heavily disturbed remnants on private farmland. Disturbances, such as livestock grazing and browsing by mammalian pests, are known to have a detrimental effect on native vegetation of these remnants. However, it is unclear what impact these disturbances have on the structure and function of forest floor invertebrate communities. Existing studies of forest fragmentation have predominantly focused on the effects of remnant area and shape, rather than remnant condition. This study examines how litter invertebrate habitat, community structure, and leaf litter decomposition, vary between grazed and ungrazed (fenced) remnants of differing size, and nearby forest reserves. Secondly, I examine how invertebrate community structure and function recover with time since livestock exclusion, with and without additional mammalian pest control. I found that grazed remnants provide dramatically altered habitat for litter invertebrates, compared to fenced remnants and large forest reserves. Grazed remnants are typified by having higher soil compaction, minimal understorey vegetation, and reduced litter cover. Consequently, grazed remnants have depauperate, yet highly variable invertebrate communities, compared to fenced remnants and forest reserves. Even very small forest remnants can support litter invertebrate communities very similar to that of larger forest reserves, provided they are protected from livestock grazing. Furthermore, invertebrate communities show strong recovery over time since livestock exclusion, particularly when livestock exclusion is combined with mammalian pest control measures. I found that litter decomposition rates did not differ between management treatments in my first observational study. However, in the second observational study, leaf decomposition rates at the edge of remnants increased with time since livestock exclusion, suggesting that restoration actions can lead to changes in ecological functioning. Small native forest remnants have high ecological value and substantial restoration gains can be made through the relatively simple action of fencing to exclude livestock.
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    Comparison of human modified and native forest habitats in the Hunua Ranges, Auckland : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Auckland, New Zealand
    (Massey University, 2010) Peace, Joanne E.
    Understanding the trophic structure of a habitat is vital to understanding the species composition and interactions of species and individuals within that habitat. It dictates which organisms may survive, their abundance, and biotic interactions. Pine (Pinus radiata) (hereafter pine) plantations in New Zealand are the most common type of silviculture, and, although primarily a commercial forestry enterprise, they are recognised as an ecosystem able to provide habitat for some native species. It is therefore pertinent to evaluate the ecological value of this habitat while keeping in mind its lack of permanence. New Zealand’s native forests are a natural comparison for mature pine plantation, and I have tracked the diet and behaviour of selected species across both habitats and their contiguous boundary. This study utilised multiple techniques and collected two years of behavioural and prey availability data to compare the habitats of interest on a variety of trophic levels (TLs) and temporal scales. Research was conducted in the Hunua Ranges, New Zealand, between March 2006 and June 2009 and considered three habitats (pine plantation, native forest, and the contiguous boundary of these habitats). Vegetation samples from leaf litter (hereafter vegetation), Lepidopteran larvae (hereafter caterpillars), predacious adult Coleoptera (hereafter beetles), rats (Rattus rattus) (hereafter rats), house mice (Mus musculus) (hereafter mice), and North Island tomtits (Petroica macrocephala toitoi) (hereafter tomtits) were analysed in terms of δ 13C, and δ 15N values. Comparisons between habitats, taxa, seasons, and sexes were conducted. Stable isotope analyses showed samples from native habitat had the lowest δ 15N levels within taxa, with boundary samples usually showing an intermediate value, and pine plantation samples commonly having the highest δ 15N levels. This suggests that the native forest provides a lesser amount of available nitrogen to the fauna inhabiting it, whereas the pine plantation (potentially due to fertilisation) contains a higher level of available nitrogen. Significant separation of taxa was seen between habitats for δ 13C values of rat and tomtit samples, and for δ 15N values of vegetation, rat, and tomtit samples. Within habitats, taxa were distinctly separated for both δ 13C and δ 15N, and their foraging ranges spanned three to four TLs. The caterpillar and mouse samples collected did not show significant seasonal fluctuations in δ 13C or δ 15N values, and ship rats showed seasonal differences only for δ 13C values. Seasonal difference in ship rat isotope signatures may indicate season related foraging locations with variation occurring between summer and autumn compared to winter and spring. Stomach content analyses for rats and mice did not show separation by habitat within species, but did show significant differences between rat and mouse diet in the boundary habitat. The volume of invertebrates, vertebrate remains, and vegetation in rat stomachs showed significant differences between seasons with a greater proportion of vegetation found during winter; however no evidence of this was seen for mice. Neither technique showed evidence of intersexual dietary differences for rodents, and isotopic values were also similar between tomtit sexes within each major habitat type. The use of stable isotope and stomach content analyses to assess rodent diet was a valuable combination as it clarified this aspect better than either method alone. Tomtit sexes differed in foraging behaviour, with males observed foraging more frequently on the ground than females and females using vegetation (in particular substrates between 0 - 3 m) more than males. Foraging by both sexes varied between breeding and non-breeding season in 2006, with more ground use occurring in the non- breeding season and more vegetation use (males: 3 - 6 m; females: 0 - 3 m) in the breeding season. Tomtit foraging behaviour in three habitats (pine plantation, native forest, and the contiguous boundary of these habitats) was compared. Overall, tomtit foraging in native forest occurred more frequently in vegetation 3 - 6 m compared to the use of this strata in either pine or boundary habitat. Males showed inter-annual differences in foraging, using the ground significantly more in 2006 than 2007. The research described tomtit foraging and habitat use, illustrating the complexity of foraging behaviour and the difficulty of understanding sex, habitat, and season associated foraging variation. The availability of the ground-prey items for tomtits differed most widely between habitats. Annual and seasonal differences were also found within pine and native forest habitat. Prey availability varied between seasons within pine (spring versus summer), native (winter versus spring), and boundary (winter versus summer) habitats. No differences between prey availability were found for male and female tomtits. However, male foraging samples showed annual separation in the pine and native habitats, and between some seasons within the pine (winter versus summer) and native (winter versus spring) forests. No significant seasonal differences were found for female comparisons. Through comparison of habitat and temporal prey availability for tomtits I have begun to determine the role that pine plantation invertebrates play in the diet of insectivorous native birds. Many questions have been raised by this study, and there is much scope for future research into the trophic structure of pine versus native forest.
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    An investigation of the factors regulating house mouse (Mus musculus) and ship rat (Rattus rattus) population dynamics in forest ecosystems at Lake Waikaremoana, New Zealand : a thesis presented in fulfilment of the requirements of the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2000) Blackwell, Grant Leonard
    Factors regulating the eruptive population dynamics of house mice, Mus musculus, and ship rats, Rattus rattus, were investigated over 29 months in mixed forest at Lake Waikaremoana, New Zealand. Mice and rats are generally present at low density, but erupt periodically following synchronous southern beech (Nothofagus spp.) seeding. A range of factors proposed as important in shaping the population dynamics of these species was investigated. These included rodent diet and habitat use, and the roles of food availability and predation pressure. Changes in rodent population dynamics were investigated using three relative density estimates: footprint tracking tunnels; and two kill trapping indices. Tracking tunnels gave reliable density estimates, but were influenced by sampling effort and habitat type. Rats had an opportunistic, omnivorous diet, and had no measurable detrimental effects of stomach parasite infection. Rats were generally more common in forest with the most food, but became equally abundant in all areas following widespread synchronous tree seeding. Rats were more numerous in areas with predators removed. Mice were found in all areas following Nothofagus seeding. Mice became scarce as food levels dropped, suggesting that the forest habitat does not contain enough food to support them in most years. The roles of food limitation and predation in shaping rodent population dynamics were investigated initially by computer modelling. The model showed that predators could not prevent a rodent population eruption, nor limit peak prey-population density. However, predation may be important during the decline and low phases of the eruption. The predictions of the model were tested in a large-scale field experiment. Predators were removed from a 750 ha peninsula in the study area. Rodent population dynamics during an eruption were compared in large areas with and without predators present. Predators did not prevent a prey eruption or limit peak population size as predicted by the computer model. There was evidence that predators limited prey populations during the post-eruption low phase, but the role of predation during the rodent decline remains unclear. Thus, the eruptive population dynamics of mice and rats in forest ecosystems in New Zealand are driven primarily by spatial and temporal variation in food supply, with predation by a single common predator potentially important during the crash and low phases following a population eruption.