Showing papers in "Austral Ecology in 1993"

Non-parametric multivariate analyses of changes in community structure

Abstract: In the early 1980s, a strategy for graphical representation of multivariate (multi-species) abundance data was introduced into marine ecology by, among others, Field, et al. (1982). A decade on, it is instructive to: (i) identify which elements of this often-quoted strategy have proved most useful in practical assessment of community change resulting from pollution impact; and (ii) ask to what extent evolution of techniques in the intervening years has added self-consistency and comprehensiveness to the approach. The pivotal concept has proved to be that of a biologically-relevant definition of similarity of two samples, and its utilization mainly in simple rank form, for example ‘sample A is more similar to sample B than it is to sample C’. Statistical assumptions about the data are thus minimized and the resulting non-parametric techniques will be of very general applicability. From such a starting point, a unified framework needs to encompass: (i) the display of community patterns through clustering and ordination of samples; (ii) identification of species principally responsible for determining sample groupings; (iii) statistical tests for differences in space and time (multivariate analogues of analysis of variance, based on rank similarities); and (iv) the linking of community differences to patterns in the physical and chemical environment (the latter also dictated by rank similarities between samples). Techniques are described that bring such a framework into place, and areas in which problems remain are identified. Accumulated practical experience with these methods is discussed, in particular applications to marine benthos, and it is concluded that they have much to offer practitioners of environmental impact studies on communities.

Environmental impact studies on marine communities: Pragmatical considerations

Abstract: The measurement of changes in the structure of natural marine communities is widely used for the detection and monitoring of man's impact on the sea. Such studies are almost always a compromise between the scientific ideal and political, financial and logistical constraints. This paper considers a number of these constraints, suggests some possible solutions, and discusses the consequences (in terms of loss of information) of adopting strategies which might be considered suboptimal. Identification of all organisms in a community to species level is a major time and cost constraint. Many recent studies have shown that very little information is lost by working at a taxonomic level higher than species (e.g. family or even phylum). This implies a functional coherence of species within each higher taxon. Indeed, there are theoretical reasons, and some empirical evidence, for supposing that community responses to human perturbations may be more easily detected above the noise of natural variability by working at high taxonomic levels. Many environmental impacts, for example oil spillages from tankers, are accidental and it is unusual to have the luxury of a time-series of data from the site prior to the incident. Good spatial control samples may also be difficult to obtain in a heterogeneous environment. Absolute rather than comparative measures of community degradation are valuable in this context. Methods which fall into this category include comparisons of community structure with some theoretical expectation or with empirical‘training’ data, comparing attributes of community structure that respond differently to perturbation, or identifying highly conservative properties of unperturbed communities that are modified in a predictable way by perturbation. All studies are selective with regard to which components and attributes of the biota should be investigated. The choice frequently depends on local expertise and research interests, rather than on an objective decision about what biological data are most appropriate for the problem in hand. The paper concludes by a discussion of the relative merits of the various alternatives.

The mechanics of spatially replicated sampling programmes to detect environmental impacts in a variable world

Abstract: Procedures used to detect environmental impacts that occur as a result of planned disturbances are often inadequate. Widely used designs for univariate measures, such as the abundance of a population, lack proper spatial replication and have unjustified patterns of temporal sampling. Asymmetrical analyses of variance derived from repeated measures models can be used to detect many types of impact that are not identifiable using widely recommended BACI (Before/After, Control/Impact) sampling. These asymmetrical, beyond BACI designs are also more logical because of spatial replication. The mechanics of these procedures are discussed, including worked examples of calculations, considerations of their power to detect impacts of a specified magnitude and the integration of various temporal and spatial scales into the design. Related issues are briefly discussed concerning optimization of sampling and how to proceed when no data are available before a disturbance.

Application of repeated measures designs in environmental impact and monitoring studies

Abstract: Traditional environmental studies have employed sampling at different times, but based on re-randomized ‘replicate’ samples taken at each time. For example, in a 4 year monitoring study of near-shore marine benthic communities there might be three box cores collected annually at each of three depths along each of three transects. Repeated measures designs, long used in medicine and the social sciences, are based on resampling replicates (e.g. sites) at a series of times. In such designs spatial sampling variability is not used for tests of environmental impact. Error for such tests is based on variability of time trends among similar sites (similar with respect to impact). For example in a tropical oil spill study five oiled and five unoiled coral reefs were studied over 5 years. Error for tests of oil impact was based on variability among reefs (within degree-of-oiling category) in the year-to-year trends of biological response variables. It was not based on variability among field samples within reefs at given times. The two approaches (univariate and multivariate) to repeated measures analysis of variance are described. The pros and cons of each are discussed, as are the assumptions and consequences of their violations. Emphasis is especially placed on the adequacy of error degrees of freedom in the two approaches, and some exploration of power to detect impact is presented. Examples of application of repeated measures designs to various impact and monitoring studies are presented and discussed, including (i) interpretation of significant effects; (ii) decomposition of effects by contrasts (e.g. before vs after impact); and (iii) modelling time trends by polynomial and cosine functions.

The ecological impact of Phytophthora cinnamomi in the stirling range national park, Western Australia

Abstract: An assessment of the impact of the soil-borne pathogenic fungus, Phytophthora cinnamomi (Oomycetes, Peronosporales), on the plant communities of the Stirling Range National Park was carried out between December 1988 and April 1989. A total of 541 plant species were collected, with the Proteaceae and the Myrtaceae the two largest families in the study region. Of the 330 species assessed for susceptibility to P. cinnamomi, 118 (36%) were recorded as having at least some individuals in a population judged to have been killed by the fungus and 33 (10%) were highly sensitive to the pathogen (more than 80% of plants in a population killed). Several families had large numbers of susceptible species, while others were apparently unaffected by the pathogen. Notably, 85% of proteaceous species assessed were rated as susceptible to P. cinnamomi. Proteaceous elements had a mean projective foliage cover of 40% in healthy plant communities, but had a mean cover of only 10% at sites that had a long history of infestation with the fungus. In contrast, some species with low levels of susceptibility to the pathogen, such as some monocotyledons, were found to be more abundant at old-infested sites than at healthy sites. Growth form may also influence susceptibility, with herbaceous perennials, annuals and geophytes assessed in this survey apparently unaffected by the fungus whereas 48% of woody perennials surveyed were susceptible. Changes in the floristic structure of plant communities may influence the composition of associated animal communities. In particular, vertebrate flower visitors may be vulnerable since 59% of the species with vertebrate-pollinated flowers were found to be susceptible to the pathogen. This research highlights the serious ecological impact of P. cinnamomi on native plant communities and suggests that significant components of the flora and associated fauna of the southwest of Western Australia are endangered by this virulent pathogen.

The intertidal distribution of the grey mangrove (Avicennia marina) in southeastern Australia: The effects of physical conditions, interspecific competition, and predation on propagule establishment and survival

Abstract: The upper and lower limits of the distribution of mature Avicennia marina lie between mean high water and mean sea level in open estuaries in southeastern Australia. Newly established seedlings are highly variable in abundance, but are rarely found in the saltmarsh or on mudflats. Their distribution is unlikely to be limited by dispersal because propagules disperse into the saltmarsh and to intertidal mudflats, but their establishment may be limited by physicochemical conditions, interspecific competition and predation. The model that physicochemical conditions control the intertidal limits of establishment of seedlings was accepted for propagules stranding in the saltmarsh but rejected for those strand- ing on mudflats. No seedlings established on saltmarsh sediments but similar numbers of seedlings established within light gaps in adult mangrove stands and on intertidal mudflats. The model that interspecific interaction with freeliving macroalgae (Hormosira banksii) re- duces the establishment of seedlings on mudflats covered with macroalgae or in stands with a ground cover of macroalgae was accepted. Under controlled conditions five times as many propagules established on cleared ground compared with ground covered with macroalgae. Predators also reduce seedling establishment, but the model that they preferentially act on propagules stranding on the mudflat was rejected. The low number of seedlings found on mudflats without macroalgae appears to relate to wave and current effects on establishment and the effects of waterlogging or fouling on survival.

The biodiversity of arthropods from Australian rainforest canopies: General introduction, methods, sites and ordinal results

Abstract: The arthropod assemblages occurring in the canopies of tropical, subtropical and cool temperate sites have been sampled using a pyrethrum knockdown technique. Details of the techniques used and the climate and vegetation of the areas studied are presented together with an analysis of the distribution of individual arthropods across Orders. An approach using generalized linear modelling partitioned the variance in numbers among sites within forest types and across the three forest types. The effects of both these components were significant. The differences between the ordinal signatures of each forest type are discussed and a number of hypotheses proposed to account for these differences, based on knowledge of the biology of the groups concerned. For the tropical and subtropical sites a comparison was made between samples collected in the low to mid-canopy with ones collected in the high canopy. Numbers of both insects and non-insects collected differed significantly with height in the subtropical forest and the distribution of insects across Orders was also significantly different in this forest type. In the tropical forests numbers of insects differed significantly between the two strata but neither the numbers of non-insects nor the ordinal profiles of either insects or non-insects were shown to be significantly different.

Improvement of environmental impact analysis by application of principles derived from manipulative ecology: Lessons from coastal marine case histories

Abstract: I discuss briefly how the basic science of ecology contributed to the resolution of environmental problems in eight different cases in which I have been involved over the past few years. I then draw from 2 decades of experience as an academic marine ecologist and biological oceanographer to extract general lessons from each case on how environmental applications could be improved by better use of the wisdom of the field of ecology. The eight cases respresent four pairs of contrasts covering a spectrum of applications of ecological science to environmental problems: (i) two assessments of the environmental impacts from coastal ocean discharges, one evaluated by data collected under traditionally designed, self-monitoring programmes largely mandated by the agency granting the discharge permit and the other employing an academically designed programme of explicit impact testing; (ii) two assessments of the effects of offshore oil and gas development, one done before exploration drilling to assess the adequacy of available environmental information on which to base decisions about drilling permits and the other an analysis of natural resource damages after a coastal oil spill had occurred; (iii) two evaluations of environmental problems conducted by special ad hoc panels created to resolve the environmental disputes; and (iv) two examples of how rule-making commissions employed ecological insights in the establishment of regulations, in one case to preserve environmental quality and in the other to manage natural fishery resources. From the experience of these eight cases, I derive 38 lessons for the future improvement of environmental problem solving by better use of ecological sciences. These lessons fall into four categories: (i) improvements in study design and analysis; (ii) recognition of the importance of the multi-species, multi-factor (‘ecosystem’) context in which populations are nested; (iii) acknowledgement of how social concerns constrain environmental decisions; and (iv) identification of common fallacies in environmental assessment.

Floristics and soil relations of upland swamp vegetation near Sydney

Abstract: We examined relations between vegetation and soils, using multivariate methods, in hitherto poorly-known upland swamps on the Woronora Plateau, south of Sydney. A major trend in floristic composition was related to the height and cover of the herbaceous stratum and reflected a gradient in soil moisture and nutrients. A second trend in floristic composition was related to the height and cover of the shrub stratum, and may reflect the influence of recurring fires on certain dominant shrub species. Five plant communities were recognized on the basis of floristic composition and were distinguishable by their different soil habitats and/or structural characteristics. We report some of the highest species-richness values in the world (at scales of 1–15 m2) for shrub/sedge-dominated vegetation, with up to 70 vascular plant species in 15 m2. Variation in species richness is inversely related to the resource gradient and positively related to the penetration of light through the vegetation canopy. This pattern is consistent with resource-competition models and warrants further investigation.

Litter inputs to a tropical Australian rainforest stream

Abstract: Vertical litterfall and lateral litter movement were monitored in the riparian zone of Birthday Creek, a small upland rainforest stream in north Queensland, from June 1987 to May 1990. Total litterfall (mean = 484 g m−2 year-1) was low in comparison with other tropical sites both within Australia and elsewhere. Litterfall was distinctly seasonal, with maxima occurring in the spring (October-November) and minima in winter (June–July). Tropical storms caused short-term increases in litterfall, especially of the small wood fraction. Overall, laterally transported litter contributed 6.8% of the total litter input to the monitored section of the stream. Lateral movement varied according to bank slope and microtopographic features and was not related to wind. Nitrogen and phosphorus concentration of leaves were low (mean N= 1.26%, P = 0.029% by weight). Nitrogen concentration of laterally transported levels overall was about 19% higher than that of leaves falling directly into the stream.

Interspecific competition: A mechanism for rodent succession after fire in wet heathland

Abstract: A competitive interaction between two species of sympatric native rodents was demonstrated experimentally in Myall Lakes National Park (NSW, Australia). The previously documented replacement of Pseudomys gracilicaudatus by Rattus lutreolus in areas of wet heath in this region implied that competition may be the mechanism facilitating this succession. We present experimental evidence to support this suggestion. Removal of the larger R. lutreolus caused a significant increase in abundance of P. gracilicaudatus on five experimental sites in comparison to five unmanipulated control sites. The sites used in this experiment were chosen from three ages of wet heath regenerating after fire. These three ages represent key stages in the replacement of P. gracilicaudatus by R. lutreolus and the occurrence of competition in each of these ages indicates that competition plays an important role in this succession. In the initial stages of the experiment when R. lutreolus were removed they were replaced by new R. lutreolus individuals. This has been interpreted as evidence of strong intraspecific competition. After removal of R. lutreolus, P. gracilicaudatus expanded its habitat range into microhabitats that had formerly been occupied by R. lutreolus and reduced its range in microhabitats previously occupied by P. gracilicaudatus. This leads us to believe that P. gracilicaudatus was occupying inferior microhabitat before the removal of R. lutreolus, which had excluded it from more preferable microhabitat.

Recolonization by Collembola of rehabilitated bauxite mines in Western Australia

Abstract: The collembolan faunas of 30 bauxite mines rehabilitated by a range of different methods between 1966 and 1977, and three forest plots were surveyed in the spring and summer of 1978–79 with the aim of studying the restoration of decomposer activity in degraded areas. The rehabilitation methods included seeding and planting with a variety of native or exotic plant species. Physical and botanical parameters of the plots were also measured. Sixty species of Collembola were collected from the rehabilitated areas; nine of the 28 species found in the forest plots were not present on the mined sites. Principal components analysis suggested that the species richness of the collembolan community in rehabilitated areas is positively correlated with plot age. A parametric correlation analysis using a number of collembolan community characteristics revealed that, among other factors, the development of a species rich collembolan fauna is positively correlated with plant species richness and diversity, and also with percentage plant cover. These results provide directions for improving rehabilitation practices.

Water relations of the canopy species in a Banksia woodland, Swan Coastal Plain, Western Australia

Abstract: Diurnal and seasonal water relations were measured in selected species of a Banksia woodland at a site with groundwater at a depth of 6–7 m. The canopy co-dominants Banksia attenuata and Banksia menziesii exhibited similar patterns of variation in water relations, both diurnally and seasonally. Stomatal conductance was usually 0.4–0.5 cm s−1 diurnally and seasonally and, generally, did not respond to water deficit and other factors. Transpiration was correlated positively with factors indicative of atmospheric evaporative demand, especially total global radiation and pan evaporation, and was highest in summer when canopy water use reached 2.1 mm d−1. Xylem pressure potential at dawn averaged −0.25 MPa in both species throughout the year. Minimum xylem pressure potential varied seasonally and was negatively correlated with transpiration. Seasonal means of minimum xylem pressure potential varied from −1.0 MPa in winter to −1.5 MPa in early summer. Both Banksia species appeared to function as phreatophytes, utilizing groundwater which enabled them to maintain high rates of water use in late summer. Water use over a 12 month period totalled 635 mm, of which the canopy and understorey contributed 61% and 39%, respectively. Water use in the woodland was dominated by the canopy in late summer and the understorey at other times.

Links between ecology and ecophilosophy, ethics and the requirements of environmental management

Abstract: This paper concerns the ways that our philosophical attitudes to the environment can influence the appropriateness of methodologies for solving environmental problems. Sometimes a public perception is expressed that science takes scant regard of the concerns of the people affected. Is it possible for scientists and managers to respond to such concerns and still fulfil the logical and methodological rigour that their discipline demands? I believe we have to address fundamental issues of definitions and meaning before useful debate can occur among parties interested in environmental decision-making. Delving into the ideas behind our everyday practices of environmental management should promote re-evaluation of our beliefs, attitudes and concerns about nature. I examine environmental science from both ethical and managerial perspectives. I explore how our assumptions and attitudes might influence ecology, in particular issues raised by environmental impacts and conservation. The major points argued here are: 1 Any legal requirements of environmental investigations must be met, but perhaps we should act more in line with the spirit of legislation. 2 The managerial imperatives of environmental investigations need to be examined closely because of widely perceived problems with the use of science in impact assessment. We must change either our methods of assessment or the regulations and administration of environmental impact assessment (EIA). 3 Science is not paramount in the processes of environmental decision-making. We need to be aware of how psychosocial factors affect the ultimately political decisions about environmental problems. 4 Philosophy and ethics offer a range of perspectives that may benefit ecology. Scientists need to be aware of these just as they should be of their own leanings about how we treat nature. 5 Scientists need to translate social concerns or demands about the environment into properly defined scientific questions, and then study them as a matter of urgency. 6 Ecology needs to guide ecophilosophers and environmental ethicists as to how nature works, why we expect variability in ecosystems, what is naturalness, and other issues where a scientific understanding of nature has progressed beyond the point where these observers of ecology have so far taken inspiration.

Pollen as a marker for migration of Helicoverpa armigera and H. punctigera (Lepidoptera: Noctuidae) from western Queensland

Abstract: Pollen carried on the probosces of Helicoverpa punctigera (Wallengren) and H. armigera (Hubner) trapped in western Queensland and in cropping areas of eastern Australia in September 1989 and 1990 was identified by scanning electron microscopy. Ninety-five per cent of moths carried pollen. A total of 19 morphological pollen species’, representing 14 plant families, was found. Up to six pollen species were found on individual moths, and 61% carried more than one. Pollen from plants unsuitable for larval survival was common. Pollen loads generally reflected the abundance of locally flowering plants, but there were exceptions which suggested migration. Pollen of Ptilotus (Amaranthaceae), Velleia (Goodeniaceae) and Eremophila (Myoporaceae), and the Asteraceae (Tubuliflorae) were found on moths trapped in the east. These plants either did not occur in the areas where the moths were caught, or did not flower there at the time the moths were caught. However, they were abundant in possible source areas such as western Queensland. Among moths caught in eastern regions, 30% of H. punctigera and 18% of H. armigera carried pollen from such plants. The value and limitations of moth-borne pollen as a marker for migration are discussed.

An assessment of pollinator visitation to Banksia spinulosa

Abstract: Remote photo-monitoring of Banksia spinulosa inflorescences indicated that birds, mammals and insects were regular visitors. These included the sugar glider, brown antechinus, eastern pygmy possum, eastern spinebill, honeybee and several moth species. Eastern spine-bills were recorded at all inflorescences monitored while visitation by other animals was more sporadic. Inflorescences were visited at least once every 24 h, and visitation frequency was approximately evenly distributed during the day and night. Examination of pollen tube growth from experimental treatments indicated that pollination success was similar from both nocturnal and diurnal visitors. However, nocturnal visitors were more effective at removing pollen from newly opened flowers. The behaviour of mammals at inflorescences was such that they would transfer much more pollen to flowers than other visitors, and probably contact receptive stigmas more often. Overall, mammals were considered to be slightly more effective pollinators than the more obvious daytime visitors, eastern spinebills. Although insects visited regularly, they were thought to be less effective at pollinating flowers than vertebrate visitors. Moths carried very little pollen, and the foraging behaviour of other insects was unlikely to promote much pollination.

Variation between Emex australis populations in seed dormancy/non-dormancy cycles.

Abstract: Seeds of four Western Australian accessions of Emex australis were stored outside and their germinability tested at 4–6 week intervals for 22 months. Accessions showed cyclical behaviour in germinability, with peaks in autumn/early winter and troughs in spring/summer. There was considerable variation between accessions in dormancy/non-dormancy cycles, but when plants from accessions with contrasting cycles were grown in a common environment, the cycles shown by their seeds were virtually identical. Thus, the parameters of seed dormancy/non-dormancy cycles in E. australis appear to be under environmental control. Only part of an E. australis seed population demonstrated cyclical changes in dormancy status, in contrast to many other annual species whose entire seed populations undergo such changes. Populations also contained individuals which were either continuously dormant or continuously non-dormant following a period of after-ripening. The latter seeds give E. australis the flexibility to recruit opportunistically after summer rainfall events in mediterranean-climate environments.

Preliminary environmental reconstructions from late Quaternary pollen and mollusc assemblages at Egg Lagoon, King Island, Bass Strait

Abstract: A late Quaternary environmental record is currently being developed from Egg Lagoon, King Island, Bass Strait, a site which is geographically well situated to contribute towards a history of the Bass Strait region. Environmental reconstructions are based on a stratigraphic survey and pollen, charcoal and mollusc analyses of sediment core samples. The recorded stratigraphy includes five sedimentary units representing estuarine-marine, freshwater lake and swamp depositional environments. Amino-acid racemization analyses of marine shells indicate a greater than last interglacial age for the basal estuarine-marine unit, while radiocarbon analyses of organic muds and wood suggest that a substantial section of the overlying freshwater lake and swamp facies is beyond the conventional limit for this technique. Local pollen assemblages represent freshwater lake and swamp plant communities that have varied presumably according to water level changes at the site. Regional pollen assemblages represent terrestrial herbaceous communities, believed to have existed under cooler and drier climates than today, and Eucalyptus- and Phyllocladus-dom'maied forests and woodlands from periods with greater effective precipitation than at present. A sustained increase in charcoal representation dating from at least 39 000 years before the present may indicate an anthro-pogenically induced change in the fire regime, consistent with the earliest dates for human occupation in mainland Tasmania.

Dynamic models and large scale field experiments in environmental impact assessment and management

Abstract: Dynamic numerical models and field experiments play important roles in impact assessment and management. Unfortunately, extreme and simplistic views have developed about whether and how to use these tools, so their complementary values to the manager are often not recognized. We often hear the outrageous claim (or hope) that numerical models can synthesize ‘all’ relevant information for predicting the impact of policy choice, hence making experimental experience unnecessary. From experimentalists, we hear the equally naive criticism that ecological systems are so complex that nothing is predictable without experimental experience. What we usually get from the proponents of these extremes are either models that are dangerously unreliable, or experiments that provide nice scientific answers to the wrong questions. Wise use of modelling begins with the following points: (i) explicit modelling is an excellent way to clarify policy concerns and identify processes that are most likely to be important in making predictions about policy effects; (ii) we can do a very good job of modelling some processes and relationships, particularly those having to do with basic spatial and temporal scales of impact as related to physical transport, chemical transformations, and life history characteristics of indicator populations (longevity, delays and response times due to age structured rates of reproduction and mortality); and (iii) there are some important dynamic processes, such as long-term accumulation of toxic materials in the environment, that unfold over such large space and time scales as to preclude direct experimental study (leaving only the issue of which models to use in making predictions, not whether to model - unless the processes are simply ignored). But points (i) and (ii) represent steps that a good experimentalist will take anyway: be clear about what practical results an experiment is intended to produce, and do not waste effort on experiments to measure things that can be predicted reliably from existing knowledge. The key to successful use of modelling and experimentation in management is in making good judgements about the interface between points (ii) and (iii); that is, in making good judgements about both what variables cannot be reliably predicted, and of these, which to treat experimentally and which to gamble on predicting from models.

Germination and seedling development of two mistletoes, Amyema preissii and Lysiana exocarpi: Host specificity and mistletoe‐host compatibility

Abstract: Potential hosts had no effect on seed germination of the mistletoes, Amyema preissii and Lysiana exocarpi, but affected seedling holdfast formation and leaf emergence. For A. preissii, formation of the holdfast and emergence of leaves occurred most rapidly in seedlings on its usual host, Acacia nyssophylla. Among the six species inoculated with L. exocarpi seeds, formation of the holdfast was quickest on A. nyssophylla and Myoporum platycarpum (usual hosts). Emergence of leaves was quickest in seedlings on A. nyssophylla, and on two non-hosts, Eucalyptus oleosa and Exocarpos aphyllus. For both mistletoe species, seedling mortality was high during the first 3 months, with considerable variation among different host species. After 6 months, little or no mortality was recorded on seedlings growing on their usual hosts. In contrast, seedlings on non-host species suffered continuing mortality and none survived the study period, except for 13% of the L. exocarpi seedlings, which persisted on Geijera linearifolia in a moribund state. The growth of seedlings on host and non-host species varied markedly. After 35 and 47 months, the average length of the longest shoot of two cohorts of A. preissii seedlings was 22 and 75 cm, respectively. After 47 months, the average length of the longest shoot of L. exocarpi seedlings on A. nyssophylla, H. oleifolium and M. platycarpum was 57, 38 and 41 cm, respectively. For both mistletoe species, a proportion of individuals on host species flowered and subsequently set fruits within 3 years. In comparison, none of the plants sown on the non-host species grew beyond seedling stage. The inability of A. preissii and L. exocarpi to establish on non-host species was attributed to mistletoe-host incompatibility.

Distributional patterns of herpetofauna in monsoon rainforests of the Northern Territory, Australia

Abstract: The herpetofauna of 50 monsoon rainforest patches in the Top End of the Northern Territory was surveyed during the dry season of 1990. This fauna contains few obligate monsoon rainforest species, many species which favour this habitat as part of a broad habitat range and a large number of species (indeed most of the regional species pool) that occasionally occur within monsoon rainforests. The taxonomic composition of species favouring monsoon rainforests is a non-random selection from the regional pool, with relatively few species in the families Agamidae and Scincidae occurring commonly in monsoon rainforests. Environmental variation among the rainforest patches sampled was portrayed by ordination, with the first axis corresponding to an environmental gradient from coastal sites to inland rocky rainforests and the second a gradient from relatively dry thickets to tall dense rainforests close to water. The distributions of herpetofauna species were depicted on this ordination space. Most frog species occurred in relatively wet rainforests and most gecko species were relatively restricted to drier rainforests. A substantial component of the herpetofauna was associated with rainforests on rocky substrate. In contrast to this relatively good association with these defined gradients, there was little apparent influence of patch size or level of disturbance on the distribution of individual species of herpetofauna. Sampling month was related to the abundance of many species, with many frog species and some snake and skink species declining (but some skink and one frog species increasing) in abundance in rainforest patches during the late dry season. This seasonal change in abundance is not due to movements from rainforest patches to adjacent vegetation types (or vice versa) but rather to total landscape (cross-habitat) changes in abundance (or detectability). The species composition of patches tended to be idiosyncratic, with substantial variability in composition, even between nearby patches of like environment. Hence it is not possible to nominate a representative rainforest herpetofauna, and indeed a classification of all quadrats (including those from rainforests, rainforest edges and adjacent habitats) based on herpetofauna species composition grouped many non-rainforest quadrats with those from rainforests. There was no rainforest edge herpetofauna assemblage. The herpetofauna from rainforests of the Northern Territory was similar to but somewhat richer than that recorded from the even more attenuated monsoon rainforest area of the Kimberley of northwestern Australia, but shared relatively few species with a sampling from monsoon rainforests from western Cape York. Frog species were more likely to be recorded across these three regions than were snake species. The number of herpetofaunal species per patch was low compared to tropical forests in northeastern Australia, Asia and central America. The long dry season of the Top End may contribute to this impoverishment. However, the small total area of monsoon rainforests in this region, the current scattered network of patches and historical fluctuations in extent and distribution of this habitat are probably at least as important.

Water relations of understorey shrubs in a Banksia woodland, Swan Coastal Plain, Western Australia

Abstract: Diurnal and seasonal water relations were measured in understorey species from a Banksia woodland. The shrubs exhibited various responses to summer drought. Stirlingia latifolia had high xylem pressure potential and transpiration in late summer. Adenanthos cygnorum maintained high xylem pressure potential year round with dawn values around − 0.3 MPa and minimum values around −1.3 MPa, but showed severe restriction of transpiration in late summer. Eremaea pauciflora and Jacksonia floribunda had high transpiration and xylem pressure potential levels in early summer, but exhibited water stress in late summer when transpiration rates were low and minimum xylem pressure potentials were as low as − 5.5 MPa. Late summer xylem pressure potentials in 27 other shrub species were, in general, inversely related to root system depth with minimum values below − 5.0 MPa in some species. The water relations of S. latifolia, E. pauciflora and J. floribunda indicated a phreatophytic habit: all possessed deep roots of sufficient size to reach groundwater that was located 6–7 m deep at the study site. Stirlingia latifolia functioned phreatophytically year round, while E. pauciflora and J. floribunda were phreatophytes until the falling water table carried ground-water beyond the reach of their roots in late summer. However, most understorey species depended on soil-stored water. Water use by the understorey was greatest in early summer.

Regeneration and growth of coolibah, Eucalyptus coolabah subsp. arida, a riparian tree, in the Cooper Creek region of South Australia

Abstract: Regeneration patterns of Eucalyptus coolabah Blakely & Jacobs subsp. arida (Blakely) L. Johnson & K. Hill (coolibah), a riparian tree of inland Australia, were inferred from size classes at two locations in South Australia; part of the floodplain of Cooper Creek and a swale in the Strzelecki Desert. These had contrasting water regimes; Cooper Creek floods on average once every 5–6 years whereas the swale has a continual water supply from a bore. A peak in size class distribution showed a regeneration event at each location but at different times. The one in the swale was more recent and was dated to the mid-1970s using aerial photography. Young (< 5 m tall) trees, interpreted as recent regeneration, were concentrated on specific topographic features, the top of a steep riverbank and a sand mound separate from the main dune system. Access to these features would have been difficult after flooding suggesting regeneration is dependent on protection from introduced herbivores. Field observations of reproductive status and canopy die-back showed coolibah condition was better in the swale. The relatively poorer condition of floodplain coolibahs was attributed to saline soils compounded by drier conditions rather than age.

Palaeoecological analysis of an isolated stand of Nothofagus cunninghamii (Hook.) Oerst. in eastern Tasmania

Abstract: Pollen analysis of the sediments of a small bog, supporting a stand of cool temperate rainforest in southeastern Tasmania, was undertaken in order to examine the history of the stand dominant, Nothofagus cunninghamii, presently growing outside its predicted climatic range. The pollen record covers at least the last 9000 years and reveals changes in the bog and in the surrounding vegetation, although pollen percentages of N. cunninghamii are sufficiently high to indicate that the species could have had a local presence throughout the recorded period. It is likely that this N. cunninghamii stand is relictual, surviving not only Holocene climates, but also the cool dry conditions of the last glacial period. This ability to survive changing and sometimes very unfavourable climates leads to the conclusion that great caution must be exercised in using present climates alone to predict the potential distribution of N. cunninghamii.

Relationship Between Types of Prey Captured and Growth Form in Drosera in Southwestern Australia

Abstract: Sympatrically growing species of Drosera were examined, including rosette forms, climbers and upright, self-supporting species, in southwestern Australia, to see whether the height above ground of the capturing leaves influenced the kinds of prey caught. The leaves examined for invertebrate prey remains were all collected at the same time and the results thus represent a snapshot of the prey situation. Although the number of fully opened, active leaves and leaf size among species varied 40-fold and 22-fold, respectively, total catch per unit leaf area was relatively constant, regardless of growth form. Growth form was strongly correlated with the kinds of prey caught. Prostrate species caught mainly walking, non-aerial prey, while self-supporting and climbing species caught predominantly aerial prey.

Use of heathland and adjoining forest by honeyeaters: Results of a radiotracking study

Abstract: New Holland (Phylidonyris novaehollandiae) and White-cheeked (Phylidonyris nigra) Honeyeaters that are resident in heathland during February and March, when there is negligible nectar production in that habitat, are expected to forage for nectar at that time in the adjacent open forest habitat. As nectar production in the heathland increases from then to June, while that in the forest decreases, the proportion of time spent by these birds in the forest should decrease over the same period. Radiotracking revealed that during February the residents did, as expected, spend time feeding on nectar in the forest and more time was spent in the forest in February than in April or June. However, the residents spent time away from the heathland throughout the year and spent more time away in June than in April. The resident honeyeaters spent about 80% of their time on our heathland grid overall. Radiotracking also indicated that there was no sharp distinction in behaviour between residents and other birds because birds that had been resident in the past but were not considered to be so at the time (absent residents), birds that would later be considered resident (future residents) and some birds that were never resident, all spent about half their time on the grid. The area that included 90% of heathland locations, estimated by radiotracking, for P. novaehollandiae and P. nigra averaged 0.48 ha per bird.

A comparison of two methods for sampling assemblages of subterranean, wood-eating termites (Isoptera)

Abstract: Within a 50 × 50 m area of wandoo Eucalyptus capillosa woodland in the Western Australian wheatbelt, the diversity and frequency of occurrence of wood-eating termite species was assessed at two food types. Over a 12 month period, monthly termite activity was determined: (i) at sound/undecayed artificial baits (seasoned wooden stakes of Jarrah, Karri, Pine, Batu, Oregon; Jarrah sawdust; paper rolls); and (li) at naturally occurring timber, fallen logs and branches of wandoo, in varying stages of decay. Termite diversity was 11 species at baits, 18 species at wandoo out of an overall site richness of 21 species. Karri attracted the most species (9); sawdust attracted none. At wandoo, Nasutitermes exitiosus, Coptotermes acinaciformis and Occasitermes occasus accounted for 59% of samples where termites were recorded. At baits, Heterotermes occiduus accounted for a mean of 80% of samples across bait types, but was rarely sampled at wandoo (5% of samples). Only H. occiduus, C. acinaciformis and Amitermes neogermanus ate bait. Pine, Oregon and paper rolls were most effective in attracting foraging termites in terms of highest per cent of replicates showing bait consumption and highest consumption rates. Jarrah and Batu were least attractive to foraging termites. Samples from wandoo underestimated the relative frequency of occurrence of H. occiduus within the study site. Coptotermes acinaciformis, which attack large food items, and certain species of Amitermes, which forage on subterranean food, may have been underestimated by both sampling methods. These findings indicate that a proper understanding of the structure of wood-eating termite assemblages within a given area requires a composite sampling strategy which addresses termites that eat sound or decayed wood, as well as surface and subsurface foragers.

Relationship between nectar production and yearly and spatial variation in density and nesting of resident honeyeaters in heathland near Sydney

Abstract: The maximum density of resident honeyeaters in heathland near Sydney was very similar from one area and year to another, despite large variation in production of nectar-energy. The most likely explanation for this is that density is determined by the spacing behaviour of birds rather than by nectar production or other factors. Within years, nesting by these residents was positively correlated with temporal variation in production of nectar-energy and 90% of nesting occurred when the estimated average amount of energy available in the heathland per pair exceeded that required to support parents and young. Most nesting and the highest nectar production consistently occurred between April and July.

Population increase and nesting patterns of the black noddy Anous minutus in Pisonia forest on Heron Island: Observations in 1978, 1979 and 1992

Abstract: Estimates of the population size of black noddy Anous minutus on Heron Island were made by counting nests in permanently marked plots in Pisonia grandis forest in 1978, 1979 and 1992. The results, and published data, indicate that the population has been increasing at ca 7% per annum since early this century and currently is ca 63 000 ± 7000 pairs. The continued exponential increase in bird numbers poses interesting ecological questions and potential management problems, as more of the island is occupied by the birds and interaction with the vegetation intensifies. Pisonia is by far the most common tree on the island and most nests are in this species. However, there is evidence that Ficus opposita is preferred over Pisonia and the high mortality of this species in the marked plots may be due to excessive use by noddies. Pisonia trees which reach the forest canopy and are in the 40–60 cm stem diameter class have more nests than smaller trees. Larger stems (>60 cm diameter) are also underutilized relative to their size, and it is suggested that this is because they are more liable to windthrow in cyclones.