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Vegetation Ecosystem Studies on both hill and wetland species, Great Barrier Island, New Zealand.
Abstract
Vegetation Ecosystem Studies on both hill and wetland species, Great Barrier Island, New Zealand. Author: Liu Huan, Master of Science (First Class Honours), The University of Auckland. Advisor: George Perry, School of Environment, Faculty of Science, The University of Auckland
This article attempted to review the relevant theories on biodiversity conservation at three layers: ecosystem diversity, species diversity and genetic diversity, illustrated by substantial case studies which were updated in recent years and published in China. Then the new theories and its corresponding improvement in conservation methods were discussed in this article.
Whangapoua Estuary, Great Barrier Island, New Zealand, is central to a proposed Marine Reserve, and is currently managed for
conservation by the Department of Conservation. This paper describes the sequential impacts of Maori and European people on
the process of estuarine vegetation succession in time and space, and the rate of estuarine sedimentation. Multiple cores
from one estuary gave confidence in assessing the temporal sequence of vegetation change, but bioturbation and other disturbance
factors made it difficult to interpret 14C dates from the estuarine environment. The modern vegetation zonation pattern on the estuary is an active succession, which
has been generated by rapid estuary in-filling, probably initiated as a consequence of erosion following Maori burning of
the adjacent forest. European forest clearance for agriculture resulted in a further increase in estuarine sedimentation,
and may have re-activated earlier sediments trapped in adjacent swamps. The combined effects of two phases of human exploitation
have resulted in large-scale loss of nutrients and top-soil from catchments throughout Great Barrier Island. Conservation
management of the estuary should take account of the anthropogenic impacts that have driven the plant succession and created
the current vegetation zonation pattern. This pattern is neither static nor ‘natural’, but rather an on-going response to
the changing human activities in the surrounding catchment.
This study reformulates the community-unit and individualistic concepts of plant communities as hypotheses concerning the distribution of species’ boundaries along a gradient. These hypotheses are tested by an analysis of deviance on data derived from a direct-gradient analysis of a freshwater marsh plant community in Breckenridge, Quebec, Canada. Boundaries are clustered at certain intervals along the gradient (p < 0.001), contradicting the individualistic hypothesis. Upper boundaries are not consistently clustered at the same intervals as lower boundaries (p < 0.001), contradicting the community-unit hypothesis. Thus, neither of the two usual models of community structure explain the patterns found in Breckenridge Marsh, suggesting that the historical dichotomy is too limited. Hypotheses of pattern should be tested using inferential statistics. Hypotheses of mechanism should be tested by experimentation. The way out of the community-unit vs. individualistic community debate is to deny the dichotomy and to consider multiple working hypotheses of community structure.
This paper presents a method for testing whether the downslope boundary of one species in a zoned community is followed by the upslope boundary of another significantly often. The test is applied to data collected on transects through zoned communities of marine algae. It was found that the number of contiguities of downslope and upslope boundaries is not generally significantly greater than the number expected on a transect. However, the proportion, 110/139, of transects with more contiguities than expected is significantly greater than one half. /// В данной статье представлен метод проверки, достоверно ли соответствует нкжняя граница обилия одного вида в зонированном сообществе граниице максимума другого. Тесть применим к данным, полученным на трансектах через зонированные сообщества мороских водорослей. Установлено, что число соприкосновений границ исчезновния и максимума одилия в целом не намого больше, чем колчество, ожидаемое на трансекте. Однако, отношение 110/139 трансект с большим числом соприкосновений, чем предполагалось, значительно больше половины.
This study tests several hypotheses relating community structure to environmental disturbance, by testing for changes in the zonation patterns of lakeshore vegetation. Twenty-five transects were examined at different positions along an exposure gradient. The range of water depths tolerated by individual species (realized niche width) changes with exposure. Some (Lobelia dortmanna, Utricularia cornuta) reached their maximum on exposed shores, others (Drosera intermedia, Cladium mariscoides) at intermediate exposure, and others (Pontederia cordata, Triadenum fraseri) on sheltered shores. Species richness peaked significantly at intermediate levels of exposure (P < .01). In spite of changes in both species composition and richness, mean niche width did not change with exposure. The distribution of the upper and lower limits of species along the gradient was examined using measures of boundary clustering. The lower and upper boundaries of species were both significantly clustered (P < .001), suggesting discrete communities exist on the shoreline gradient. As exposure increased, upper boundaries became more cluster (P < .002); lower boundaries were unaffected. The distribution of boundaries shifted landward with increasing exposure. This fact is possibly related to an identical landward shift in the lower boundaries of shoreline shrubs, which appear to have a major influence on the distribution of herbaceous shoreline vegetation.
The vegetation pattern of three mountain mires in the upper Ongarue River catchment, west Taupo, is described and a species list presented. Data were collected from systematically-located plots, using a modified Braun-Blanquet cover scale. Ordination techniques arranged the plots and species in a sequence from sedge-fernland through shrubland to forest, following a gradient of increasingly better drainage. Plot classification identified four mappable floristic groups which reflect drainage conditions and mire nutrient status, the largest mire being oligotrophic, the others mesotrophic.
A simple method for detecting non-random patterns of distribution of the boundaries of species is described. The method uses transects running across a community, where the number of upper and lower boundaries of species in each quadrat is recorded. The expected number of quadrats containing one or more boundaries can be calculated from the binomial distribution. The mean deviation of observed from expected number of such quadrats, for a set of transects, can be tested for departures from zero. Significant departures greater than zero indicate regular dispersion of boundaries. A mean deviation significantly less than zero indicates clustering of the boundaries. The method is unbiased and thus corrects previously published methods.
Zonation patterns of salt marsh vegetation were examined at latitudes ranging from 4440N at Halifax, Nova Scotia, to 5850N at Churchill, Manitoba. It was found that in all areas examined the landward boundaries of the species' zones were more nearly coincident (i.e., more clustered) than their seaward boundaries. A conspicuous latitudinal trend was found: the clustering of both landward and seaward boundaries increased with increasing latitude. Evidence that between-species competition influences the locations of zone boundaries was also obtained. Possible implications of the results in terms of a relationship between intrapopulation polymorphism and latitude are discussed.
The temporal and spatial patterns of rodents at Little Windy Hill, Great Barrier Island
- L Davy
The current vegetation of Kaitoke Swamp
- G N Rutherford
Forest vegetation in Glenfern Sanctuary: Preliminary surveying results
- J Ogden
- J Perry
The individualistic concept of the plant association
- H A Gleason
Great Barrier Island
- E Cameron
Great Barrier Island
- J Ogden