Models of vegetation dynamics in semi-arid vegetation: Application to lowland Central Otago, New Zealand

Predictions from three conceptual models of the dynamics of semi-arid vegetation (Clementsian succession, alternative stable states and annuation/pulse phenomena) are used to review the available evidence on changes in the vegetation of semi- arid lowland Central Otago, New Zealand. Evidence is presented from Central Otago that corresponds with Clementsian succession and with annuation/pulse phenomena, although there is so far no formal evidence of alternative stable states. A declining- productivity model, which combines aspects of the other models, is also shown to fit the process of vegetation change in vegetation dynamics in Central Otago are insufficient for the employment of management frameworks such as degradation gradient assessment and the state-and-transition model.     

The vegetation of Flat Top Hill: An area of semi-arid grassland/shrubland in Central Otago, New Zealand

An account is given of the vegetation of Flat Top Hill, in the driest part of semi-arid lowland Central Otago, New Zealand. Although highly modified, the area was acquired for conservation in 1992, following almost 150 years of pastoral use. The vegetation was sampled in a composite scheme using permanent monitoring sites placed to include the majority of habitats and communities present. A number of environmental factors were measured in each sample. Native species comprise 53% of the vascular flora of the area (211 species). From multivariate analyses of the data collected over three seasons, fourteen 'communities' are recognised. Although there are few constant or faithful species, strong relationships are shown with certain environmental parameters. Moisture stress is the major environmental influence on the vegetation; soil depth and past disturbance are secondary determinants. The communities differ by a factor of 10 in vascular species richness; the richest communities, and those with the greatest native component, are those around rock tors. Many of the communities present have not been reported from other vegetation surveys in Central Otago Moisture stress at xeric sites in the dry core of the region has excluded some exotic species, and allowed the survival of the native component, including three tiny spring ephemerals. Near elimination of grazing, as a result of reservation, will probably lead to an increase in the cover of taller, palatable exotic grasses and Thymus vulgaris, which may threaten the survival of some native species. Optimum management, for recovery or persistence of native species, may comprise exclusion of grazers in some areas, but continuity of grazing in others.     

Emergence behaviour of rabbits, Oryctolagus cuniculus, in Central Otago, New Zealand

The characteristic emergence behaviour of a rabbit population in Central Otago, New Zealand, involves a steady rise in the number of rabbits active throughout the afternoon to a peak near sunset. This differs from populations in Great Britain and Australia, where emergence occurs later and is more rapid. Young rabbits emerged slightly later than adults and were more susceptible to disturbances. Slightly earlier emergence by male rabbits, particularly between May and September, was possibly related to the increased levels of territoriality and social interaction just before and during the early stages of the breeding season. Three emergence indices (25% of the population feeding, 50% of the population emerged, and maximum number of rabbits emerged) were significantly correlated with season. Rabbits emerged earliest before sunset in winter and spring and latest in autumn. Daily variation in emergence times was considerable and was related to weather factors such as temperature and wind direction. A greater level of diurnal activity in New Zealand rabbit populations than in those in Great Britain and Australia is possibly associated with lower levels of diurnal predation in New Zealand.     

Vegetation change following exclusion of grazing animals in depleted grassland,Central Otago,New Zealand

Abstract. Models of semiarid vegetation dynamics were evaluated to explain changes in the grassland of interior South Island, New Zealand. Annual records were taken for six years of plant species height frequency and percentage ground cover in five plots established in 1986. One subplot at each site was fenced to exclude sheep, one to exclude rabbits and sheep, and one remained unfenced as a control. Records from 1986–1992 were analysed by ordination. The overall pattern of vegetation change shows considerable year-to-year variation. At some sites, variation in vegetation composition between years was as great as, or greater than, that between grazed and ungrazed subplots. Such variation is particularly evident in grazed vegetation, perhaps because it is under greater stress than ungrazed vegetation. At one site changes in vegetation total cover and species composition could be statistically related to rainfall during the first half of the growing season. The only general trends following cessation of grazing were for perennials to increase in frequency, and for year-to-year changes to become smaller with time. Total vegetation cover values seldom changed as a result of cessation of grazing, but tended to follow year-to-year changes in species frequency. The results do not in general support switch/state-and-transition models of semi-arid vegetation dynamics. Vegetation change follows changes in grazing and climate with little lag. This most closely conforms with the Pulse-phase dynamic model.     

Indicator species for the interpretation of vegetation condition in the St Bathans area, central Otago, New Zealand

Monitoring the effect of management in rangelands is an integral part of the process of adaptive management. An understanding of how individual species react to management has two major benefits. Firstly, monitoring, can be simplified by avoiding species which are reacting mostly to other influences, and secondly the abundance of species can be interpreted in a meaningful way for assessing the influence of previous management. Gradient analysis on a matrix of 69 sample sites and 125 species in the St Bathans area of Central Otago identified a relatively homogenous data set, within which the effects of environmental variation had been minimised so that the major pattern of vegetation composition change was explained by pastoral impact. Ten plant species showed clear responses along the pastoral impact gradient, and were abundant over certain ranges of this gradient. It is recommended that these species be used to monitor trends in vegetation condition.     

Aggregation of avian predators and zooplankton prey in Otago shelf waters, New Zealand

In Otago shelf waters surface swarms of krill (Nyctiphanes australis),hyperiid amphipods (Parathemisto spp.) and galatheid crab larvae(Munida gregaria) provide an abundant summer food source forplanktivores. We tested the hypothesis that aggregation of avianplanktivores depends upon the spatial distribution of theirprey. Gulls (Larus scopulinus, L.bulleri, L.dominicanus), sootyshearwaters (Puffinus griseus) and white-fronted terns (Sternastriata) showed significantly aggregated distributions. Thedistribution of birds sitting on the sea surface was correlatedwith the abundance pattern of krill but was not correlated withthe distribution of smaller hyperiid amphipods. The distributionof flying red-billed gulls (L.scopulinus), black-billed gulls(L.bulleri) and sooty shearwaters was correlated with the krilldistribution but black-backed gulls (L.dominicanus) were not.Stomach contents of black-billed gulls were dominated by krill,in contrast to sooty shearwaters, which ate a higher proportionof Minida, and black-backed gulls, which contained Munida andfish. No amphipods were found in bird stomachs. There was nosignificant correlation between bird distributions and the hydrographicregime, water depth or distance offshore. The distribution ofprey rather than hydrographic regime was a more important determinantof bird distributions at this spatial scale (2.6–12 km)and location.     

Seasonal changes in photosynthetic activity of snow tussocks (Chionochloa spp.) along an altitudinal gradient in Otago,New Zealand

Summary Photosynthetic characteristics were studied in Chionochloa rigida, an altitudinally widespread snow tussock and a closely related high-altitude species C. macra. Along a gradient from near sea level to 1600 m there were no consistent differences in maximum photosynthetic capacity which averaged 4.5 mol CO₂ m^-2s^-1. The photosynthetic temperature optimum ranged between 15 and 18°C and there was only a limited capacity for seasonal adjustment. Net photosynthesis was light-saturated at about 500 mol photons m^-2s^-1. In winter, the photosynthetic capacity decreased significantly with increasing altitude of origin of the snow tussocks. A transplant experiment indicated this was partly genetically controlled.     

Panbiogeography and conservation science in New Zealand

Abstract

New Zealand’s official conservation science framework, the Protected Natural Areas Programme (PNA), is evaluated in relation to current biogeographic/systematic methods and principles with reference to philosophy, taxonomy, information content, and historical geological/biological relations. The PNA Programme and its parent International Union for Conservation of Nature and Natural Resources (IUCN) framework is based on a phenetic system of classification that does not reflect process (phylogenetic) characters of ecological systems. The PNA philosophy of conservation science is shown to be essentialist, rooted in traditional medieval Western metaphysics, and out of step with current developments in biogeography, systematics, and ecology. Panbiogeography is an appropriate global perspective for developing a conservation science because it meets the requirements of homology, monophyly, increased information content, and empirical testability whereas the PNA programme does not. Establishment of a Panbiogeographic Track Atlas is proposed as a suitable conservation framework for historical ecology and biogeography. The atlas could provide an empirical natural resource inventory to identify priority areas for conservation at an economically acceptable cost compared to the PNA Programme. Application of cladistic techniques to ecological and biogeographic patterns in relation to the Atlas can provide aphylogenetically sound hierarchical classification for conservation science. The potential benefits of the panbiogeographic approach for conservation education and tourism are discussed.     

Early Devonian reefs at Reefton, New Zealand: guilds, origin and paleogeographic significance

Study of 35 systematically collected and 10 semi‐random samples (about 100 cm 2 each) from one outcrop of the Lankey Limestone (Emsian) near Reefton, New Zealand indicates that it is a reef framestone built by tabulate (4? spp.) and clonal rugose (one sp.) corals, two species of stromatoporoids, a few bryozoans (2? spp.) and crinoids. The guild structure of the reef community and data on skeleton orientation and growth direction further indicate that there was relatively minor biostratonomic alteration of the original community. Skeletons are either in growth position or tipped, toppled or even overturned, but they have remained in situ. Other clone‐rich Lankey Limestone outcrops in the Reefton area support the notion of an upper shelf reef system and stratigraphic and sedimentologic data suggest that it was located near the Gondwana margin at a paleolatitude of about 35°S.     

Ground invertebrate fauna associated with native shrubs and exotic pasture in a modified rural landscape, Otago, New Zealand

This study examined whether the diversity and relative abundance of ground-dwelling invertebrates changed in relation to type of vegetation cover. Invertebrate taxon diversity and relative abundance were assessed with pitfall traps placed under the native shrubs Olearia bullata and Coprosma propinqua, and in surrounding patches of exotic pasture. A total of 1935 invertebrates and at least 152 invertebrate taxa were recorded from 49 pitfall traps. The number of native taxa was c.63% of all taxa recorded, whereas exotic invertebrates represented only c.9%. The other c.28% were of undetermined origin. Taxon richness and relative abundance under the two shrub species were statistically similar, although all mean values (except for Coleoptera) were higher for traps set beneath C. propinqua. In contrast, taxon richness and relative abundance were significantly higher in the exotic pasture than under either of the shrub species. The same pattern was evident for exotic invertebrates and the relative abundance of native invertebrates, and for some of the most speciose orders. The data indicate that nearly half of native taxa occurred only under native shrubs. In contrast, 7 out of 12 exotic species were found in all three vegetation types, and all but one of them were recorded at least in exotic pasture. We conclude that the value of locally-modified and patchy vegetation cannot be underestimated for its potential in providing native biodiversity reservoirs for New Zealand’s native invertebrate fauna.     

Plant and invertebrate assemblages on waste rock at Wangaloa coal mine, Otago, New Zealand

Natural regeneration on waste rock was investigated at the old Wangaloa coal mine, south-east Otago. A 450-m long waste rock stack had been created 40–50 years ago, and has had little anthropogenic intervention since. The stack is made up of a gradient of three main waste rock types, defined as ‘silt-rich’, ‘mixed’, and ‘quartz-rich’, which reflect different proportions of loess siltstone and quartz gravel conglomerate. Plant species assemblages were quantified in four 5-m² quadrats in each waste rock type. Invertebrates were heat extracted from substrate cores (7 cm diameter; depth 5 cm) collected from quadrats over an eight-week period in spring 2003. Ordination analysis showed statistically distinct plant and invertebrate assemblages had arisen on each waste rock type. Revegetation patterns were dominated by native, woody individuals on all waste rock types, particularly manuka (Leptospermum scoparium) and kanuka (Kunzea ericoides). Plant cover on ‘silt-rich’ waste rock was four-fold that on ‘quartz-rich’ waste rock. Total numbers of invertebrates were highest on ‘quartz-rich’ waste rock, but richness greatest on ‘silt-rich’ waste rock. Collembola dominated the fauna but their numbers were proportionally greatest in poorly vegetated areas. Further work is required to explain the absence of plants and invertebrates from local areas of waste rock.     

Assessment of potential sources of protozoan contamination between two avian feeding guilds in a conservation area

Occasional screening of food and water quality available to organisms in protected areas could be beneficial to their successful conservation. This is important for areas receiving regular human visitors and exhibiting activities that may be detrimental to ecosystem health. This study determined the intestinal protozoan species harboured by insectivorous and granivorous birds within the Jos Wildlife Park, Nigeria and whether the two avian feeding guilds are more susceptible to protozoan infection through water or food (grass seeds and insects). Special boxes were used to collect faecal samples from trapped birds. Samples were later analysed in the laboratory for protozoans. Both food and water utilised by the birds in the area were microscopically screened. The composition and abundance of intestinal protozoans between the two feeding guilds did not show significant differences. However, considering parasite species individually, the degree of infection by protozoans such as Giardia lamblia was highly related to the range of infection sources that a feeding guild was exposed to. The composition of parasites observed in the two feeding guilds was strongly linked to both water bodies and avian diet obtainable in the Park. These observations showed that birds in the Park are orally susceptible to infection with protozoans, some of which have been reported to cause health implications in birds. Thus, any measure to curtail environmental contamination by the parasites may improve ecosystem health and survival of avian species in the Park.     

Declining plant species richness in the tussock grasslands of Canterbury and Otago, South Island, New Zealand

We studied vegetation change on 142 permanently marked transects spread throughout tussock grasslands of Otago and Canterbury, in areas subject to both pastoral and conservation management. The transects were established between 1982 and 1986 and remeasured between 1993 and 1999, providing a record of vegetation change at each site over an interval varying from 10 to 15 years. Each transect consisted of 50 quadrats, each 0.25m(2), in which the presence of all vascular plant species had been recorded. For each transect, we calculated the change between measurements in the mean number of species recorded per quadrat, and the change in the total number of species recorded per transect. Averaged across all transects, there was a significant decline in species richness between measurements at both the quadrat and transect scales. Small herbs (those less than or equal to2 cm tall, excluding Hieracium species) showed the greatest decline. On average, more than one quarter of the small herb species present in a quadrat at the first measurement had disappeared within 10 years. Larger herbs, ferns, rushes, sedges and grasses (excluding Chionochloa species) also declined significantly in species richness, reflecting declines in the abundance of species in these groups. Woody species richness remained constant, while species in the genera Chionochloa and Hieracium increased significantly in mean quadrat species richness, reflecting increases in the abundance of these species along transects. The rate of decline in mean quadrat species richness was unrelated to changes in the abundance of either Chionochloa or Hieracium species, or to an overall increase in total vegetation cover on transects. The rate of decline in species richness was also unrelated to the level of grazing or burning between measurements. However, the rate of decline in species richness was greater at lower elevation, on schist rock and on yellow-brown and yellow-grey soils. Our results suggest that a major compositional change is occurring in these grasslands at a rate that is independent of local variation in management and independent of the widespread invasion of these grasslands by Hieracium species.     

Bryophyte ecology of a dune area in New Zealand

Summary and conclusions Bryophyte ecology has been little investigated in New Zealand. In the present study a northern dune area (under a dune reclamation and afforestation scheme) on the west coast, is divided into five community zones. Two of these are phases in the artificial sere leading from bare sand to exotic pine plantations. The others are seral stages in the development of the coastal forest climax.The bryophyte flora is investigated both quantitatively and qualitatively for the terrestrial, epixylic and corticolous habitat in each of these communities.It was found that mosses are not pioneers in the psammosere as is frequently the case in the northern hemisphere. They were secondary invaders at a late stage in the Lupinus-Psamma phase when the lupin bushes play an important part. The first bryophytes occupied epixylic stations (on logs and fallen branches). The bryophytic flora showed developmental changes in relation to the nature of the cover communities. Life form and drought tolerance of the bryophyte species are important factors. Long distance migration is by spores, but local dispersal by vegetative growth and the transportation of detached tufts is of great importance.The size and shape of quadrat for terrestrial communities is fully investigated. It was found that shape was of no essential importance in bryocoenological methods The heavy needle litter of the pine plantations had no retarding effect on the moss carpet. Succession within the bryophyte community is from hepatics to acrocarpic and then to pleurocarpic mosses.Corticolous mosses form a group apart and are affected by such factors as drainage patterns, nature of bark and exposure.The bryophyte union is worked out for each cover community and three terrestrial unions and one corticolous union are recognised. It is suggested that one of the terrestrial unions is dynamic and that basically there are two distinct terrestrial unions as a climax to the bryophyte microsere; one for the Leptospermum scrub and the other for coastal forest.My thanks are due to Prof. V. J. Chapman (Auckland University College N.Z.) for his advice and encouragement during the course of this investigation.

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Résumé Les dunes de sable très élevées sur la côte occidentale de la Nouvelle Zelande ont été fixées avec Psamma arenaria et Lupinus et plantées de Pins exotiques (Pinus radiata).Le versant Nord d'une dune a été étudié au point de vue du développement de la végétation. Ce versant comprend une partie plantée de Pinus et une autre abandonnée à l'évolution naturelle de la végétation.La flore bryophytique est divisée en trois catégories selon la station: Mousses vivant sur la terre nue, sur les arbres (Mousses corticoles) et sur le bois mort. Sur cette dune les Mousses n'apparaissent pas comme pionniers; elles s'installent après l'établissement de Lupinus d'abord sur des branches tombées (mortes).Les formes biologiques des différentes Bryophytes et leur résistance contre le desséchement ont été étudiées en rapport avec les types de végétation.Les spores des Mousses sont parfois apportées de très loin, mais dans le territoire même qui a été etudié la dispersion végétative par accroissement et par des parties détachées des touffes joue un grand rôle.Quelques expériments avec des carrés de différente surface montrent que la forme des surfaces étudiées est de peu d'importance pour l'étude bryosociologique.Même la litière épaisse sous le couvert du Pin ne retarde pas le développement des Mousses. Les Hépatiques apparaissent les premiers, suivies des Mousses acrocarpes et ensuite des Mousses pleurocarpes.Les Bryophytes corticoles forment une unité à part. On a discerné en tout quatre groupements, trois groupements terrestres et un groupement corticole. Un des trois groupements terrestres constitue probablement un stage de développement tandis que deux autres semblent être des groupements terminaux permanents: stades terminaux l'un pour la brousse à Leptospermum, l'autre pour la forêt littorale.

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This work was carried out by the author while staying at the Auckland University College, New Zealand.     

Gastrointestinal helminths of little blue penguins,Eudyptula novaehollandiae (Stephens), from Otago,New Zealand

Data regarding helminth communities can provide insights into health, feeding interactions, behaviour and evolution of their host organisms. Penguins (Spheniscidae) are important components of marine food webs and tracking their helminth communities can be indicative of ecosystem health. New Zealand is home to 5 of the world's 19 penguin species and little is known about their gastrointestinal helminths. Here, we provide the first study on the gastrointestinal helminths of little blue penguins from south-eastern South Island, New Zealand. The helminth community consisted of two species of tapeworm; Tetrabothrius lutzi and Tetrabothrius sp.; three nematode species, Contracaecum eudyptulae, Capillaria sp. and Stegophorus macronectes; two acanthocephalans, Andracantha sigma and Bolbosoma balaenae; and one trematode, Galactosomum otepotiense. The most prevalent parasites were T. lutzi, A. sigma, and C. eudyptulae. This work includes three new host records and five new geographic records. This is the first report of B. balaenae occurring in a host other than a marine mammal. This study adds to our knowledge about the helminth community of New Zealand little blue penguins, and includes new genetic data on helminth species, providing a baseline against which future studies may be compared.