Jane Chambers

Highlights
• Urban woody plantings can be maintained by coppicing, which stimulates resprouting.
• Coppiced and non-coppiced plants had similar survival in a common garden experiment.
• Species from drier regions had higher survival and maintained growth.
• Deeper rooted species had higher survival but lower vigour after coppicing.
• Woody plants from drier regions can create resilient urban plantings.

Woody plants can be used for resilient urban greening in cities with drying climates. Coppicing – regular cutting of plants to 10–20 cm aboveground – can be used to maintain plants in cities by stimulating resprouting and regeneration. Species selection could consider climate adjusted provenancing and the habitat template approach, yet little is known about how these methods translate to coppiced urban plantings. Therefore, we investigated resprouting survival and vigour of species from two bioregions with one representing the future climate of the other, and with a range of root traits. We also compared coppiced and non-coppiced plant survival and vigour under two watering regimes. Twenty-four woody species were grown in a common garden experiment for two years in southwestern Australia. There were four treatments based on water availability (summer watering and not watered) and coppicing (coppiced after one year and non-coppiced) with five replicates. Survival, vigour, and plant traits were measured on all plants after two years, including basal area, height, stem number, specific leaf area, total leaf area ratio, and root:shoot ratio. Coppiced (81 %) and non-coppiced (90 %) plants had similar survival, however survival of individual species was highly variable (range 0–100 %). Coppicing increased stem number and total leaf area. Summer watering increased survival of non-coppiced plants but did not change coppiced plant survival or traits. Species from the warmer and drier bioregion had the greatest survival in all treatments. Species with greater root:shoot ratio and/or with deeper roots had greater survival but lower vigour after coppicing. We found local plant communities were suitable for naturalistic woody plantings in an urban environment, and these could be maintained through coppicing. We suggest using climate adjusted provenancing and the habitat template approach, by using species from warmer and drier regions and with a range of root traits for short-term vigour and long-term survival.

Human activities and climate change are altering wetland hydrology, potentially affecting freshwater turtle habitats. Understanding freshwater turtle habitat requirements is important for conservation. Chelodina oblonga, a freshwater turtle endemic to southwestern Australia, inhabits wetlands undergoing hydrological changes due to reductions in rainfall and urbanisation. Urban populations of C. oblonga are declining, but limited knowledge of their habitat requirements hinders conservation efforts. This study used radio-telemetry to determine the habitat associations of 100 adult female C. oblonga in three urban wetlands with varying hydrological regimes between 2018 and 2020. During wetland inundation, turtles occupied dense stands of two emergent macrophytes: Typha orientalis (naturalised, invasive) and Machaerina articulata (native). When wetlands dried, turtles aestivated in shallow areas beneath these plants, contrasting with previous reports that aestivation occurred within the deepest areas. As inundation was the trigger for emergence from aestivation, some individuals in the shallowest areas aestivated for > 581 consecutive days and missed a reproductive season. This study indicates that complex vegetation is key aquatic and aestivation habitat for female C. oblonga, and alterations to hydro-regimes, particular increased drying, may have severe implications for isolated freshwater turtle populations through limiting recruitment. Hydrological regimes that incorporate an annual wetted period are recommended for conserving C. oblonga, in view of projected ongoing drying of wetlands due to climate change. Maintenance and restoration of dense emergent macrophyte stands, preferably the native M. articulata, is recommended to help conserve C. oblonga populations in wetlands that regularly retain surface water in the future.

Roads affect the connectivity of habitat and inhibit movements of animals as a result of road avoidance and road-related mortalities. Freshwater turtles are particularly vulnerable to mortality on roads, as females must often cross them when they leave the aquatic environment to nest. Ecopassages designed to enable safe movement across roads by wild animals may be an effective measure to reduce adverse impacts. Limited information exists, however, on effective design criteria for freshwater turtles.

A willingness-to-utilize study was used to assess factors that may influence the use of a tunnel underpass by the southwestern snake-necked turtle (Chelodina oblonga), a species whose populations are declining, in part, through road-related mortalities of nesting females. Female C. oblonga were sourced from an urban wetland and placed in an enclosure with exits of varying tunnel lengths (12 and 25 m) and lighting treatments (‘light’ and ‘dark’) to assess the conditions that would promote successful passage.

Generalized linear modelling showed that light treatments had a significantly increased likelihood of successful and faster passage for both 12 and 25 m tunnels than the dark treatments. Tunnel length had no effect either on success or rate of passage.

This study provides the first account of the factors that may optimize successful tunnel passage by C. oblonga to reduce road-related mortality, contributing to the conservation and management of the species and freshwater turtles more generally.

Urban vegetation provides many social and environmental benefits, yet integrating diverse vegetation into urban areas can be difficult due to spatial and financial constraints. Naturalistic streetscape plantings have gained popularity as a method to improve vegetation diversity without requiring additional land or maintenance costs. In temperate climates, these plantings are typically meadow-style and informed by research on people’s preferences. Yet in mediterranean-type climates, naturalistic plantings reflect shrub-dominated native vegetation, for which public aesthetic preferences are largely unknown. To address this gap we conducted an online survey in Perth, Australia where respondents (n = 985) rated their preferences for 32 computer-generated images of public streetscape, naturalistic, woody plantings that differed in structure (low (<1 m), mid, and upper (>2 m)), flower presence, foliage colour, and visual symmetry. These were compared to an image of low-input lawn, representing a typical local government-maintained streetscape. We also assessed how environmental worldviews, plant knowledge, demographics, and suburb scale tree cover influenced preferences. Naturalistic woody plantings were liked by 88%, and lawn disliked by 87% of respondents. The most preferred aspects of naturalistic plantings were multiple structural layers, flowers, and both green and grey foliage. Positive preferences for naturalistic plantings and dislike of lawn were stronger from respondents with pro-environmental worldviews, greater plant knowledge, and who resided in suburbs with higher tree cover. Therefore, we recommend naturalistic woody plantings as a publicly acceptable method to improve streetscape quality. Overall, this research provides insights into the nexus between social and ecological values of streetscape plantings for the planning and design of sustainable urban greening in a warming, drying mediterranean-type climate. [Display omitted]

Freshwater turtles are one of the most endangered vertebrate groups, with an estimated 60% of species threatened. The influence of environmental factors on the life cycles of most turtle species is poorly understood, including triggers for nesting movements. Although temperature and rainfall have been identified as triggers for nesting in some species, it is unknown if and how reductions in rainfall arising from climate change may disrupt reproductive movement. We aimed to determine the environmental factors that trigger nesting movements of Southwestern Snake-necked Turtles (Chelodina oblonga) in south-western Australia, a global biodiversity hotspot undergoing severe climatic drying. A citizen science program was implemented to monitor nesting behavior over a 4-yr period. Generalized linear mixed models (GLMM) were used to identify the environmental variables that best explained the number of female turtles exhibiting nesting movements. Daily nesting movements were significantly associated with decreasing average air pressure, consistent with seasonal cold frontal weather systems that bring the majority of annual rainfall to the region. The effect of rainfall on turtle nesting movements varied depending on the spatial scale of modelling. Our results indicate that the projected reductions in frequency of cold fronts and rainfall in southwestern Australia may disrupt nesting movements. This could reduce recruitment success of this turtle and further increase the need for adaptive management to improve conservation of the species. The study highlights the need for further research on the impacts of climate change on environmental triggers of nesting of freshwater turtles in drying regions.

Many regions across the globe are shifting to more arid climates. For shallow lakes, decreasing rainfall volume and timing, changing regional wind patterns and increased evaporation rates alter water regimes so that dry periods occur more frequently and for longer. Drier conditions may affect fauna directly and indirectly through altered physicochemical conditions in lakes. Although many studies have predicted negative effects of such changes on aquatic biodiversity, empirical studies demonstrating these effects are rare. Global warming has caused severe climatic drying in southwestern Australia since the 1970s, so we aimed to determine whether lakes in this region showed impacts on lake hydroperiod, water quality, and α, β and γ diversity of lake invertebrates from 1998 to 2011. Seventeen lakes across a range of salinities were sampled biennially in spring in the Wheatbelt and Great Southern regions of Western Australia. Multivariate analyses were used to identify changes in α, β and γ diversity and examine patterns in physicochemical data. Salinity and average rainfall partially explained patterns in invertebrate richness and assemblage composition. Climatic drying was associated with significant declines in lake depth, increased frequency of dry periods, and reduced α and γ diversity (γ declined from ~300 to ~100 taxa from 1998 to 2011 in the 17 wetlands). In contrast, β diversity remained consistently high, because each lake retained a distinct fauna. Mean α diversity per-lake declined both in lakes that dried and lakes that did not dry out, but lakes which retained a greater proportion of their maximum depth retained more α diversity. Accumulated losses in α diversity caused the decline in γ diversity likely through shrinking habitat area, fewer stepping stones for dispersal and loss of specific habitat types. Biodiversity loss is thus likely from lakes in drying regions globally. Management actions will need to sustain water depth in lakes to prevent biodiversity loss.

Urbanization is one of the most influential land use changes globally and continues to affect wetland ecosystems and their biota. Freshwater turtles, which rely on both terrestrial and aquatic habitats to complete their life cycles, are one of the most endangered vertebrate groups, with approximately 60% of species threatened. Although habitat alteration caused by urbanization is recognized as one of the main threats to freshwater turtles, there is a paucity of studies quantifying the effects of terrestrial habitat change on turtle populations.

The aim of this study was to determine how terrestrial land use change, associated with urbanization, influences the viability of freshwater turtle populations. Thirty‐three wetlands were sampled for the southwestern snake‐necked turtle (Chelodina colliei Gray, 1856) (Chelidae) between October 2016 and February 2017 within a region of continuing urban intensification. Land use and habitat types were classified at the aquatic–terrestrial interface and within a 300‐m band around each wetland. Generalized linear mixed models were used to identify the land use variables that best explained the relative abundance of C. colliei.

Turtle abundance and population structure varied widely among wetlands. The percentage of residential land use, and the presence and accessibility of fringing native vegetation, was positively associated with the relative abundance of C. colliei. The association with residential land use may be an artefact of historical land use, whereas the association with native vegetation is probably because adjacent vegetation provides connectivity with suitable nesting sites, and thus facilitates increased recruitment.

This study shows how the modification of terrestrial habitat around wetlands may directly influence the population viability of freshwater turtles. Protection and restoration of native vegetation fringing urban wetlands is crucial to support the viability of remnant freshwater turtle populations

Riparian zones are considered to improve stream condition by providing a buffer between waterways and agricultural land that can intercept nutrients, but is their efficacy universal? This paper develops a conceptual model comparing the interactions of slope, soil, hydrology, vegetation and nutrient dynamics between 1) the riparian zone of an intermittent stream in a low-relief (1.6%) catchment with deep sands of low reactivity (Bingham Creek) and 2) a perennial stream in a sloped (10%) catchment with reactive soils over an impermeable layer (Lennard Brook), with a view to compare and contrast their riparian functionality. This study compared the attributes of groundwater (three rows of nested piezometers) (0.5 m,1.5 m and 2.5 m depth), stream, soil and vegetation across a transect from the stream, through the riparian zone to agricultural paddocks. In the low-relief catchment, water did not flow through the riparian zone as in a sloped catchment. Porous soils, together with a lack of slope or a confining layer meant water oscillated vertically through the soil profile over the season, with minimal horizontal movement and limited interaction with the active root zone of riparian vegetation; the intermittent stream discharged P-rich water into the riparian zone during the first flush of winter rains. The highly unreactive sands resulted in trivial P or C uptake resulting in high dissolved concentrations in adjacent streams (0.6–0.9 vs 0.001–0.002 mg/L TP, 58 vs 3 mg/L DOC for flat vs sloped catchments respectively). The high DOC in slow-moving groundwater resulted in highly reducing conditions, promoting P solubility and potentially denitrification. Litterfall from vegetation marginally improved riparian soils with better P retention relative to the adjacent paddock (3620–268 kg TP/ha storage) and reduced FRP in the groundwater relative to the stream (27 vs 80%). The conceptual model developed highlights an alternative functionality of riparian zones for low-relief catchments that challenges the assumption of riparian efficacy.

Submerged plants are often abundant in lowland streams in agricultural landscapes, but little is known of their role in stream ecosystems compared to riparian vegetation. We investigated the importance of submerged macrophytes as a basal resource of food webs in stream reaches with good and poor riparian vegetation condition, using mixing model analysis with stable carbon and nitrogen isotopes. Epilithic periphyton and terrestrial detritus were important basal resources in good condition reaches, although where macrophytes were present they contributed to food webs. Higher assimilation of either the macrophyte Cycnogeton huegelii or conspicuous epiphytes on C. huegelii leaves was associated with poor riparian condition. Where Potamogeton ochreatus and Ottelia ovalifolia occurred in poor condition reaches, these macrophytes contributed moderately to the food web, but were probably of greater importance as substrates for epiphytic algae. Mixing models indicated invertebrates commonly had generalist feeding strategies, feeding on the most available resource at each reach. Thus, where riparian vegetation is limited, submerged macrophytes may support opportunistic consumers both directly and as a substrate for epiphytes, thereby partially compensating for the loss of allochthonous resources in lowland agricultural streams.

Submerged macrophytes are important structural and biological components of many lowland streams with potential to support ecosystem processes in degraded streams, provided that growth is not excessive. In a low-gradient agricultural landscape, a survey was used to explore associations between submerged macrophyte growth, biodiversity and variables assessing stream condition in seasonally-flowing streams. These variables were sampled across fifty-three reaches on seven adjacent streams in the mediterranean climate region of south-western Australia. Native submerged macrophytes were present in 43 % of sampled reaches, forming two distinct macrophyte assemblages dominated either by Potamogeton spp. together with Otteliaovalifolia, or by Cycnogeton spp. The Potamogeton/Ottelia assemblage was present in degraded reaches with higher light availability and deposition of fine sediments, but did not show excessive growth, even under nutrient-enriched conditions. Conversely, Cycnogeton spp. were associated with shaded conditions and greater flow. Reaches with macrophytes present had significantly higher macroinvertebrate abundance and family richness than those without, although rarefied family richness was similar among reaches with and without submerged macrophytes. The more structurally complex Potamogeton/Ottelia assemblage supported a greater abundance of grazers, shredders and predators than the simpler Cycnogeton spp. In degraded agricultural streams, remnant and colonising populations of submerged macrophytes may compensate for loss of riparian-derived habitat and resources for macroinvertebrates, and thus the food supply for predatory species.