385 research outputs found
Modelling confinement experiments in community ecology: Differential mobility among competitors
No full textField experiments in which mobile organisms are confined inside enclosures have been widely used in many areas of marine, freshwater and terrestrial ecology in the past three decades. Some ecologists believe that at least some and possibly most, of the interpretation of this work may be subject to dispute because of potential artefacts associated with the confinement itself. Simulations suggested that moderate or even severe artefacts may arise from using enclosures that are ‘too small’, which could produce inferential nonsense in some circumstances (Mac Nally, 1997). Here, the influence of differential mobility is explicitly considered in a simulated environment, with organisms confined in enclosures of a variety of sizes. Some simulations involve single populations, while others pit together competitors differing only in mobility. Three foraging strategies based on simple movement principles are simulated. Results indicate that the relationships between resource consumption and mobility will depend upon foraging strategy, often in unexpected ways compared with the implications of spatial averaging. Outcomes of interactions among pairs of populations having the same foraging strategy but with different mobilities also are complex, indicating that the results of confinement experiments may involve non-intuitive interactions between mobility and foraging method. There needs to be a refocusing on basic biology of organisms used in confinement experiments (e.g. movement distributions) and, particularly, constructing defensible statements on why the selected scales were used
Balancing the environmental benefits of reforestation in agricultural regions
Get PDFAbstract not available.S.C. Cunningham, R. Mac Nally, P.J. Baker, T.R. Cavagnaro, J. Beringer, J.R. Thomson, R.M. Thompso
Longer-term response to experimental manipulation of fallen timber on forest floors of floodplain forest in south-eastern Australia
No full textThere often are substantial accumulations of fallen timber (logs, large boughs) in many woodlands and forests around the world. However, fallen timber has become a target for removal for use as fuel or for management actions, such as fuel-reduction burning. Many silvicultural practices, such as fast harvesting rotations, coppicing and debris burning prior to re-sowing/re-planting, lead to much reduced fallen-timber loads. Many studies show the ecologically important role fallen timber plays, so its removal is likely to have adverse ecological outcomes. It has previously been shown that a specialized forager on fallen timber, the brown treecreeper Climacteris picumnus, responded strongly over a short-term (20 mo) to a meso-scale (34 ha) manipulation of fallen-timber loads in river red gum Eucalyptus camaldulensis forest in northern Victoria, Australia [Mac Nally, R., Horrocks, G., Pettifer, L., 2002a. Experimental evidence for beneficial effects of fallen timber in forests. Ecol. Appl. 12, 1588–1594]. There were substantially more birds in all treatments in which loads were increased to 40 Mg/ha or more, elevated from averages of ca. 20 Mg/ha across the southern Murray-Darling Basin. Sites were revisited 3 years after the manipulation was conducted and I show here that the changes in density have been sustained. These results suggest that increased fallen-timber loads ≥40 Mg/ha are preferred by the vulnerable treecreeper, and that the bird's responses reported previously were not transient. These elevated densities may translate into increased reproductive success of the treecreepers because larger groupings in this and related cooperative breeders produce more young. I conclude by outlining options for management of fallen timber to provide greater chances of viability for the specie
Catchment zoning for freshwater conservation: refining plans to enhance action on the ground
No full textSummary: Recent advances in freshwater conservation planning allow addressing some of the specific needs of these systems. These include spatial connectivity or propagation of threats along stream networks, essential to ensure the maintenance of ecosystem processes and the biodiversity they sustain. However, these peculiarities make conservation recommendations difficult to implement as they often require considering large areas that cannot be managed under conventional conservation schemes (e.g. strict protection). To facilitate the implementation of conservation in freshwater systems, a multizoning approach with different management zones subject to different management regimes was proposed. So far, this approach has only been used in post hoc exercises where zones were allocated using expert criteria. This might undermine the cost-effectiveness of conservation recommendations, because both the allocation and extent of these zones have never been optimized using the principles of systematic planning. Here, we demonstrate how to create a catchment multizone plan by using a commonly applied tool in marine and terrestrial realms. We first test the capability of Marxan with Zones to address problems in rivers by using a simulated example and then apply the findings to a real case in the Daly River catchment, northern Australia. We also demonstrate how to address common conservation planning issues, such as accounting for threats or species-specific connectivity needs in this multizone framework, and evaluate their effects on the spatial distribution and extent of different zones. We found that by prioritizing the allocation of zones subject to different management regimes, we could minimize the total area in need of strict conservation by a twofold factor. This reduction can be further reduced (threefold) when considering species' connectivity needs. The integration of threats helped reduce the average threats of areas selected by a twofold factor. Synthesis and applications. Catchment zoning can help refine conservation recommendations and enhance cost-effectiveness by prescribing different management regimes informed by ecological needs or distribution of threats. Reliable information on these factors is a key to ensure soundness of planning. Freely available software can be used to implement the approach we demonstrate here. Catchment zoning can help refine conservation recommendations and enhance cost-effectiveness by prescribing different management regimes informed by ecological needs or distribution of threats. Reliable information on these factors is a key to ensure soundness of planning. Freely available software can be used to implement the approach we demonstrate here
Forecasting the impacts of habitat fragmentation. Evaluation of species-specific predictions of the impact of habitat fragmentation on birds in the box-ironbark forests of central Victoria, Australia
No full textWe tested forecasts made by Mac Nally and Bennett (Mac Nally, R., Bennett, A.F., 1997. Species-specific predictions of the impact of habitat fragmentation: local extinction of birds in the box-ironbark forests of central Victoria, Australia. Biological Conservation 82, 147–155) of relative vulnerability to habitat fragmentation for 43 species of birds in the box–ironbark system of central Victoria, Australia. The predictions were based on a simple, tripartite model linking habitat specialization, density and mobility, three of the characteristics most widely mooted in the literature to influence vulnerability to habitat fragmentation. For each species, a predicted index of ‘proneness’ to local extinction was calculated by using prior, independent data. The model system consisted of existing fragments of 10, 20, 40 and 80 ha size-classes, with between 5 and 15 ‘replicates’ of each size-class. Replicated ‘reference-areas’ — mapped-out areas of these same size-classes set within large (>10 000 ha) remnant forests of the same general vegetation as the fragments — were surveyed also to provide ‘expectations’ of the likelihood of finding each species in a given size-class. Our results indicated that the simple model had virtually no predictive power: the index-values for proneness to local extinction were no help in forecasting whether a given species was over- or under-represented in a fragment of a given size based on the bird's occurrence in reference-areas of similar size. When the three components of the model were tested separately, measures of habitat specialization and mobility showed no relationship with the observed responses of birds to fragmentation, while for population density there was a significant relationship but in a direction contrary to that expected. Evaluation of assumptions underlying the test revealed two main factors that are likely to have affected the model's performance: (1) differences in anthropogenic impacts between fragments and reference-areas have resulted in differences in habitat quality, and (2) species interactions within fragments differ from those in reference-areas, a result of secondary effects arising from the altered spatial pattern of the habitat (e.g. the expansion of numbers and influence of ‘despotic’ species such as the noisy miner Manorina melanocephala). These two factors appear to be common to most fragmented systems and, therefore, need to be addressed in predictive models of species vulnerability. However, because the nature of anthropogenic impacts and the types of changes to species interactions in fragments differ between ecosystems, we conclude that it will be difficult to develop a model of species' vulnerability to fragmentation that has both strong predictive ability and wide generality among ecosystems
Murray-Darling Basin Environmental Water Knowledge and Research Project: Waterbirds Theme Research Appendix
No full textAppendix 1 McGinness, H. M. (2016) Waterbird responses to flooding, stressors and threats. CSIRO, Australia. Technical literature review report. Appendix 2 McGinness, H.M., Langston, A., Robinson, F., Piper, M., Martin, J., Doerr, V.A.J., Kingsford, R., and Mac Nally, R. Satellite-tracking ibis and spoonbill movements and habitat choices. Appendix 3 McGinness, H.M., Robinson, F., Piper, M., and Hodgson, J., Kingsford, R., Mac Nally, R. and Doerr, V.A.J. Quantifying ibis and spoonbill egg and chick survival rates and mortality drivers using motion-sensing and time-lapse cameras. Appendix 4 Brandis, K., Bellio, M., Callaghan, D., Webster, E., Francis, R. Monitoring ibis and spoonbill nest success through on-ground tagged nest and water depth monitoring.Appendix 5 Brandis, K., McCann, J., Lyons, M. Ibis and spoonbill nest and colony mapping using drone imagery.Appendix 6 Ibis and spoonbill chick energy source assimilation. Current authors include: Paul McInerney, Kate Brandis, Heather McGinness, Ralph Mac Nally. Appendix 7 O’Brien, L. and McGinness, H.M. (in review) Ibis and spoonbill chick energy requirements: Implications for wetland management. Appendix 8 Lucy Wenger and Heather McGinness (2018) Waterbird Chick Development: A Visual Guide to Selected Australian Species. CSIRO, Australia. Appendix 9 Webster, E. (2017) Similarities and differences in breeding ecology of straw-necked ibis Threskiornis spinicollis and Australian white ibis T. moluccus in response to environmental flows. Honours thesis, UNSW. Appendix 10 Theme Data InventoryAppendix 11 Theme OutputsAppendix 12 Theme Engagement and Communications Activitie
Murray-Darling Basin Environmental Water Knowledge and Research Project: Waterbirds Theme Research Appendix
No full textAppendix 1 McGinness, H. M. (2016) Waterbird responses to flooding, stressors and threats. CSIRO, Australia. Technical literature review report. Appendix 2 McGinness, H.M., Langston, A., Robinson, F., Piper, M., Martin, J., Doerr, V.A.J., Kingsford, R., and Mac Nally, R. Satellite-tracking ibis and spoonbill movements and habitat choices. Appendix 3 McGinness, H.M., Robinson, F., Piper, M., and Hodgson, J., Kingsford, R., Mac Nally, R. and Doerr, V.A.J. Quantifying ibis and spoonbill egg and chick survival rates and mortality drivers using motion-sensing and time-lapse cameras. Appendix 4 Brandis, K., Bellio, M., Callaghan, D., Webster, E., Francis, R. Monitoring ibis and spoonbill nest success through on-ground tagged nest and water depth monitoring.Appendix 5 Brandis, K., McCann, J., Lyons, M. Ibis and spoonbill nest and colony mapping using drone imagery.Appendix 6 Ibis and spoonbill chick energy source assimilation. Current authors include: Paul McInerney, Kate Brandis, Heather McGinness, Ralph Mac Nally. Appendix 7 O’Brien, L. and McGinness, H.M. (in review) Ibis and spoonbill chick energy requirements: Implications for wetland management. Appendix 8 Lucy Wenger and Heather McGinness (2018) Waterbird Chick Development: A Visual Guide to Selected Australian Species. CSIRO, Australia. Appendix 9 Webster, E. (2017) Similarities and differences in breeding ecology of straw-necked ibis Threskiornis spinicollis and Australian white ibis T. moluccus in response to environmental flows. Honours thesis, UNSW. Appendix 10 Theme Data InventoryAppendix 11 Theme OutputsAppendix 12 Theme Engagement and Communications Activitie
Changes in soil carbon of pastures after afforestation with mixed species: sampling, heterogeneity and surrogates
No full textAccurate and efficient estimation of soil C is vital to understanding and monitoring the role of afforestation in C sequestration. Here, we focused on the potential of mixed-species plantings, for which there is negligible information but expanding investment due to their added environmental benefits. We surveyed soil C and N over a representative chronosequence (5–29 years old) of existing plantings, including measurements in the adjacent pastures to account for differences in soil type and land-use history among properties. Vegetation characteristics of the tree plantings were measured to identify potential surrogates for rapid assessment of soil C. Soil C was highly heterogeneous under the plantings and the adjacent pastures, with up to eight cores required to sample adequately a plot of 400m². Vegetation surrogates had limited success in predicting soil C after afforestation, with the only strong predictors being tree density and planting age. Three decades of afforestation with mixed species had not led to substantial changes in C concentration or content of the soil. The C:N ratio of soils increased with planting age suggesting that the C becomes more resistant to decomposition after afforestation. Over longer time scales, tree plantings are likely to have larger impacts on the amount and forms of soil C.S.C. Cunningham, K.J. Metzeling, R. Mac Nally, J.R. Thomson, T.R. Cavagnar
Interaction strengths and spatial scale in community ecology: Simulated quadrat-sampling and confinement experiments involving animals of different mobilities
No full textMuch recent effort has been directed at quantifying strengths of interactions between competitors, predators and prey, hosts and parasites, and mutualists. These measurements are used to quantify elements of ‘community matrices’, which are coefficients summarizing dynamics. In many cases, experimental manipulations are used to estimate certain interactions that are deemed to be likely to be of most dynamic significance (most ‘intense’), while other relationships within the community are estimated by using correlative means. These data are then linked by using statistical methods such as path analysis. The two forms of data are gathered by using very different methods: (1) experiments, usually involving confinement (or exclosure); and (2) quadrat- or transect-based information. A major issue is whether information from these two different sources are ‘compatible’, especially in relation to whether they have similar scalar responses. Can they be reliably mixed? Here, quadrat- and enclosure-based information are derived for the same model systems to evaluate whether scalar responses are consistent between the two forms of information. Interactions between pairs of three forms of forager are considered. For two of these forms, biases are generally consistent between enclosure and quadrat data indicating that they have similar scalar responses. However, for a third foraging form that has more ‘intelligent’ foraging and decision-making behaviour, major inconsistencies in deductions and biases arise. These latter results are discussed in terms of the implications for construction of community matrices
Trophic relationships of two sympatric species of Ranidella ( Anura).
No full textBreeding males of Ranidella signifera and R. parinsignifera, which are morphologically alike and occupy similar microhabitats, are not differentiated with respect to die
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