Amy Hahs - Academia.edu (original) (raw)

Papers by Amy Hahs

Austral Ecology, May 24, 2016

Landscape Ecology, Jul 9, 2014

Understanding of how species distributions are driven by landscape-level processes has been obscu... more Understanding of how species distributions are driven by landscape-level processes has been obscured by null or inconsistent findings from poorly designed studies. We explore how differences in the way potential drivers of species distributions are defined can influence their perceived effects. Specifically, we evaluate how much statistical power is lost when continuous variables are discretised, and how the use of qualitatively defined nominal variables impacts biological interpretation of results. We fitted generalized linear models to dependent variables relating to bat distribution (species richness, diversity, relative abundance of functional groups and individual species) obtained from 36 sites across Melbourne, Australia, and independent variables that were continuous (percentage tree cover, dwelling density), ordinal (dichotomised continuous variables) or nominal (land-use, urban context). We found that models fitted with continuous predictors had better fit and explanatory power than those fitted with ordinal predictors for all response variables. Ordinal models failed to detect statistically significant effects for 4 of the 11 response variables that were successfully modelled with continuous data, suggesting Type II errors had occurred. Models fitted with nominal data explained a comparable amount of variation in some dependent variables as continuous models. However, interpretation of the mechanisms behind responses to nominal categorical levels was obscured because environmental conditions within them were confounded and not homogenous. To gain better understanding from nominal predictors would therefore require further investigation. Our findings show that careful consideration must be given to the choice of environmental variables used for species distribution modelling and how those variables are defined.

Urban Ecosystems, 2020

Remnant forests in urban areas are hotspots of urban biodiversity. However, the survival and inte... more Remnant forests in urban areas are hotspots of urban biodiversity. However, the survival and integrity of many remnant forests are currently at risk. Better knowledge of the interactions between remnant forests and urban environments is urgently needed for guiding the conservation effort. In this study, we intend to answer the question: how do patch attributes and landscape patterns of surrounding environments affect the taxonomic diversity of woody plants in urban forest remnants? We surveyed the woody plant species in 240 sample plots in 54 remnant forest patches in Guiyang City, China. We analyzed the taxonomic diversity of woody plants and the effects of influencing factors using multi-level taxonomic diversity indicators and the generalized dissimilarity modeling. The results showed that shrubs had higher within-patch α-diversity than that of trees. However, adult trees had higher among-group β-diversity than those of shrubs and saplings/seedlings. The vegetation type of the patch had more influence than other factors on the compositional dissimilarity of adult trees and sapling/seedling among patches. The patch size had the highest impact on the compositional dissimilarity of shrubs. Besides, small patches had a higher rate of compositional turnover in all woody plants. The percentage of impervious surfaces in surrounding areas and the spatial distance from each other were the main influencing factors for adult trees and saplings/ seedlings, respectively. Based on our results, we recommend that more attention should be paid to preserve the small remnant forest patches and protect sampling/seedlings to maintain the taxonomic diversity of urban remnant forests.

Landscape Research, Apr 12, 2017

Landscape preferences shape decision-making and drive the ecological outcomes of urban landscapes... more Landscape preferences shape decision-making and drive the ecological outcomes of urban landscapes. We investigate how people's landscape preferences are shaped by the green space context (public park vs private residential garden landscapes) and by physical features such as vegetation complexity. A postal questionnaire was sent to households near seven urban parks in Melbourne, Australia. Results showed that landscapes were grouped into four categories based on patterns of preference response. Landscapes with moderate vegetation complexity were placed in separate categories distinguished by green space context (parks vs gardens), while very simple and very complex landscapes were placed in different categories irrespective of green space context. Surprisingly, dense vegetation was highly preferred by respondents. As areas of dense vegetation also provide complex habitats for wildlife, this highlights the possibility of developing policies and designing landscapes that can benefit both people and nature.

Landscape and Urban Planning, Sep 1, 2016

h i g h l i g h t s • We examined three vegetation management approaches used in urban green spac... more h i g h l i g h t s • We examined three vegetation management approaches used in urban green spaces. • Bird and bat assemblages responded positively to increases in native plant richness. • Bird species richness increased with greater understorey vegetation volume. • Bat species richness increased with increasing density of trees >81 cm in diameter. • These measures can be implemented without compromising multiple uses of green space.

Frontiers in Ecology and Evolution, May 24, 2022

Ecography, Aug 29, 2016

According to ecological fi ltering theory (Keddy 1992), only some species will persist in a given... more According to ecological fi ltering theory (Keddy 1992), only some species will persist in a given area following environmental change (Williams et al. 2009). Urbanization is a strong driver of environmental change, and plant species respond to it in diff erent ways (Olden and Poff 2003). Depending on the ability of plants to cope with the altered conditions, some species will become locally extirpated while others will persist. Urbanization will also off er opportunities for new plants, not previously part of the local fl ora, to join the community through changes in local ecological conditions, like increases in resource availability through eutrophication (Shochat et al. 2006, Grimm et al. 2008, McDonnell and Hahs 2015). Plant responses to urbanization-driven changes depend on individual species traits (McGill et al.

Journal of Environmental Quality, 2016

Journal of Environmental Quality THE URBAN FOREST AND ECOSYSTEM SERVICES SPECIAL SECTION Core Ide... more Journal of Environmental Quality THE URBAN FOREST AND ECOSYSTEM SERVICES SPECIAL SECTION Core Ideas • We sampled soil under tree canopy, tall grass, and short grass in 13 urban greenspaces.

The contribution of urban greenspaces to support biodiversity and provide benefits for people is ... more The contribution of urban greenspaces to support biodiversity and provide benefits for people is increasingly recognised. However, ongoing management practices still favour (1) vegetation oversimplification, often limiting greenspaces to lawns and tree canopy rather than multi-layered vegetation that includes under and midstorey; and (2) the use of nonnative plant species. These practices likely hinder the potential of greenspaces to sustain indigenous biodiversity, particularly for taxa like insects, that rely on plants for food and habitat. Yet, little is known about which plant species may maximise positive outcomes for taxonomically and functionally diverse insect communities in urban greenspaces. Additionally, while urban environments are expected to experience high rates of introductions, quantitative assessments of the relative occupancy of indigenous vs. introduced insect species in greenspace are rare – hindering understanding of how greenspace management may promote indige...

Springer eBooks, 2013

Melbourne, Australia is a city rich in biodiversity. It contains a high proportion of open space ... more Melbourne, Australia is a city rich in biodiversity. It contains a high proportion of open space and supports a large number of fl ora and fauna species, both indigenous to the region and introduced from around the world. The high levels of biodiversity are partly the result of historical planning decisions that did not deliberately consider biodiversity yet inadvertently favoured many plants and animals. However, Melbourne is currently at a tipping point whereby continued urban growth is likely to result in a loss of biodiversity if it is not explicitly and carefully considered in planning, policy and management. Enhancing biodiversity into the future will be aided by a reconciliation of underlying tensions between (1) growth and conservation and (2) the management of 'native' and 'exotic' vegetation that are currently embedded in a range of governance structures and public attitudes. This would enable the implementation of urban design that promotes biodiversity across the city as a whole.

Functional Ecology, Jul 1, 2015

PeerJ, Oct 22, 2015

Habitat complexity is a major determinant of structure and diversity of ant assemblages. Followin... more Habitat complexity is a major determinant of structure and diversity of ant assemblages. Following the size-grain hypothesis, smaller ant species are likely to be advantaged in more complex habitats compared to larger species. Habitat complexity can act as an environmental filter based on species size and morphological traits, therefore affecting the overall structure and diversity of ant assemblages. In natural and semi-natural ecosystems, habitat complexity is principally regulated by ecological successions or disturbance such as fire and grazing. Urban ecosystems provide an opportunity to test relationships between habitat, ant assemblage structure and ant traits using novel combinations of habitat complexity generated and sustained by human management. We sampled ant assemblages in low-complexity and high-complexity parks, and high-complexity woodland remnants, hypothesizing that (i) ant abundance and species richness would be higher in high-complexity urban habitats, (ii) ant assemblages would differ between low-and high-complexity habitats and (iii) ants living in high-complexity habitats would be smaller than those living in low-complexity habitats. Contrary to our hypothesis, ant species richness was higher in low-complexity habitats compared to high-complexity habitats. Overall, ant assemblages were significantly different among the habitat complexity types investigated, although ant size and morphology remained the same. Habitat complexity appears to affect the structure of ant assemblages in urban ecosystems as previously observed in natural and semi-natural ecosystems. However, the habitat complexity filter does not seem to be linked to ant morphological traits related to body size.

Austral Ecology, Jun 1, 1999

Plant community composition and its likely environmental controls were investigated for 200 sampl... more Plant community composition and its likely environmental controls were investigated for 200 sample plots (each 100 m 2) from Mediterranean-type vegetation in the Little Desert National Park, Victoria. TWINSPAN classification revealed four readily identifiable vegetation types; mallee-broombush, heathland, stringybark open woodland, and an assemblage intermediate between mallee-broombush and heathland referred to here as broomheath. Mallee-broombush was found on Parilla Sands characterized by high Ca levels relative to heathland and stringybark open woodlands on unconsolidated Lowan Sands. The first axis of a 2 dimensional non-metric MDS ordination also divided heathlands (high axis scores) from mallee-broombush (low scores), while the second separated these vegetation types from stringybark woodlands and broom-heath. Vector-fitting revealed significant correlations between the locations of samples in ordination space and exchangeable soil Ca, soil colour, aspect and Shannon-Weiner diversity. Highest species richness/diversity was associated with the ecotonal area between Parilla and Lowan Sands (i.e. broom-heath) where a number of species characteristic of different assemblages had overlapping ranges. The fire-sensitive conifer, Callitris rhomboidea, was preferentially located in stringybark woodland and broom-heath vegetation types. Its presence was positively associated with high species richness and aspects having a southerly component. Four Callitris stands sampled for population structure were all > 40 years old and showed evidence of interfire recruitment from seeds released by old, serotinous cones. Overall, results suggest that variations in plant community composition and structure in the eastern block of the Little Desert are primarily due to variations in soil properties associated with the distribution of the two dominant substrate types, Parilla Sand and Lowan Sand. However, the interplay of topography and fire behaviour has probably been more important than substrate type in determining the distribution and population structure of longer-lived, fire-sensitive species such as Callitris rhomboidea.

Ecological Applications, Mar 1, 2008

Developing tools to predict the location of new biological invasions is essential if exotic speci... more Developing tools to predict the location of new biological invasions is essential if exotic species are to be controlled before they become widespread. Currently, alpine areas in Australia are largely free of exotic plant species but face increasing pressure from invasive species due to global warming and intensified human use. To predict the potential spread of highly invasive orange hawkweed (Hieracium aurantiacum) from existing founder populations on the Bogong High Plains in southern Australia, we developed an expert-based, spatially explicit, dispersal-constrained, habitat suitability model. The model combines a habitat suitability index, developed from disturbance, site wetness, and vegetation community parameters, with a phenomenological dispersal kernel that uses wind direction and observed dispersal distances. After generating risk maps that defined the relative suitability of H. aurantiacum establishment across the study area, we intensively searched several locations to evaluate the model. The highest relative suitability for H. aurantiacum establishment was southeast from the initial infestations. Native tussock grasslands and disturbed areas had high suitability for H. aurantiacum establishment. Extensive field searches failed to detect new populations. Time-step evaluation using the location of populations known in 1998-2000, accurately assigned high relative suitability for locations where H. aurantiacum had established post-2003 (AUC [area under curve] ¼ 0.855 6 0.035). This suggests our model has good predictive power and will improve the ability to detect populations and prioritize areas for ongoing monitoring.

Cambridge University Press eBooks, Jun 25, 2009

The unprecedented growth of cities and towns around the world, coupled with the unknown effects o... more The unprecedented growth of cities and towns around the world, coupled with the unknown effects of global change, has created an urgent need to increase ecological understanding of human settlements, in order to develop inhabitable, sustainable cities and towns in the future. Although there is a wealth of knowledge regarding the understanding of human organisation and behaviour, there is comparably little information available regarding the ecology of cities and towns. This book brings together leading scientists, landscape designers and planners from developed and developing countries around the world, to explore how urban ecological research has been undertaken to date, what has been learnt, where there are gaps in knowledge, and what the future challenges and opportunities are.

Annual Review of Ecology, Evolution, and Systematics, Dec 4, 2015

Around the world the development and growth of cities and towns are having a significant impact o... more Around the world the development and growth of cities and towns are having a significant impact on local and global biodiversity. There is growing interest in the adaptation of nonhuman organisms to urban environments, and we distinguish between the concepts of adaptation and adaptedness. Most of these studies have focused on animals, especially birds. Commonly recorded responses to urban environments include regulatory and acclimatory responses involving changes in behavior, communication, and physiology. Developmental responses tend to be morphological in nature but can also involve cultural learning. There is growing evidence of microevolutionary changes associated with adaptive responses to urban environments. This review also highlights the urgent need to refine the terminology currently used to describe the adaptation of organisms to urban environments in order to improve scientific understanding and more effectively identify and communicate the actions required to create biodiversity-and adaptation-friendly cities and towns for the future.

bioRxiv (Cold Spring Harbor Laboratory), Nov 16, 2022

The bioblitz phenomenon has recently branched into cities, presenting exciting opportunities for ... more The bioblitz phenomenon has recently branched into cities, presenting exciting opportunities for local governments to channel participants' efforts toward local issues. The City Nature Challenge (CNC) is one such initiative that has been quickly uptaken by hundreds of municipalities worldwide. Despite high participation, we still lack a framework for evaluating how the CNC contributes to local biodiversity knowledge and to inform local government practices. Here, we develop such a tool and present a case study that illustrates its applicability. We demonstrate that the collected records contributed to a better understanding of contemporary, local biodiversity patterns and provided a more realistic representation of understudied groups such as insects and fungi. Importantly, we show that the CNC presented local governments with a cost-effective tool to make informed, evidence-based management and policy decisions, improve education and engagement programs, foster cross-council collaborations, and support a stronger sense of environmental stewardship within the local community.