Stephen J. Livesley’s research while affiliated with University of Melbourne and other places

Background and aims Wildflower meadows are a low-maintenance landscape treatment that can improve urban biodiversity and achieve conservation outcomes, especially when designed to use plants from threatened grassy ecosystems. Cost-effective approaches to create meadows include direct seeding onto mined sand substrates that are placed onto site soils to supress weed competition and enhance sown plant establishment. However, waste subsoils diverted from landfill could provide a more sustainable alternative. This study compares a mined sand with a clay subsoil to understand the relative differences in sown plant establishment and root growth for a range of south-east Australian grassland species. Methods Germination, seedling emergence and root development were assessed for six species sown in an 80 mm deep cap of two low nutrient substrates (sand and clay subsoil) overlying a simulated site soil. Rhizoboxes were used to assess the rate at which plant roots could access soils beneath capping substrates. Results Sand and clay subsoil supported the establishment of the six sown species. Five species had significantly greater total root length, leaf area and aboveground biomass when sown in recycled subsoil, compared with sand. Conclusion Edaphic conditions affect the establishment of native grassland species in wildflower meadows. Compared to sand, recycled clay subsoils provide a more sustainable alternative for establishing designed wildflower meadows and can support rapid root and plant growth in south-east Australian grassland species.

Combating climate change and achieving the UN Sustainable Development Goals (SDGs) are two important challenges facing humanity. Natural climate solutions (NCSs) can contribute to the achievement of these two commitments but can also generate conflicting trade‐offs. Here, we reviewed the literature and drew on expert knowledge to assess the co‐benefits of and trade‐offs between 150 SDG targets and NCSs within 12 selected ecosystems. We demonstrate that terrestrial, coastal, and marine NCSs enable the attainment of different sets of SDG targets, with low redundancy. Implementing NCSs in various ecosystems would therefore maximize achievement of SDG targets but would also induce trade‐offs, particularly if best practices are not followed. Reliance on NCSs at large scales will require that these trade‐offs be taken into consideration to ensure the simultaneous realization of positive climate outcomes and multiple SDG targets for diverse stakeholders.

Wildflower meadows support biodiversity in urban environments, whilst providing low‐maintenance, amenity landscapes. By moving from international plant palettes to those that include species from threatened plant communities in meadows, we can reintroduce native species to urban landscapes and help achieve conservation objectives. Adapting horticultural techniques from Europe, we determined if such approaches could support the germination and establishment of grasses and wildflowers from critically endangered plant communities in Melbourne, Australia. Working in an urban park, we sowed seed of 27 species on soil capped with two depths of sand (10 and 80 mm) and site soil without sand to determine the impact of sand on weed emergence, slug grazing and growth of sown species. We quantified weed biomass and the time spent weeding unsown species from the emerging meadow. We also tested if covering the sites with a jute mesh enhanced sown species establishment. Twelve months after sowing, the percentage cover of sown species did not differ significantly among treatments. However, the cover of forb species was greater on plots without jute, whereas the cover of grasses was greater on plots with jute. Forb density and species richness were highest on 80 mm sand treatments without jute and lowest on 80 mm sand with jute. We attribute this to greater competition from grasses and higher slug abundance in the presence of jute, leading to the loss of forb species that are more palatable to slugs. Greater sand depths significantly reduced the time to weed and the biomass of weed species removed from the emerging meadow. Synthesis and applications. Using low‐nutrient substrates to cap and bury the weed seed bank, irrigation and direct seeding, we demonstrate it is possible to return plants from threatened grassy ecosystems to urban sites, creating a dense and species‐rich native understorey within 1 year whilst reducing labour requirements during meadow establishment.

The increasing heat stress in cities due to climate change and urbanisation can prevent people from using urban green spaces. Irrigating vegetation is a promising strategy to cool urban green spaces in summer. Irrigation scheduling, such as daytime vs night-time irrigation and the frequency of irrigation in a day, may influence the cooling benefit of irrigation. This study aimed to investigate whether irrigation scheduling can be optimised to increase the cooling benefit and determine how the cooling benefit changes with weather conditions. A field experiment with twelve identical turfgrass plots (three replicates × four irrigation treatments) was set up to measure the afternoon cooling benefits of irrigation. The four treatments included: no irrigation, single night- time irrigation (4 mm d–1), single daytime irrigation (4 mm d–1) and multiple daytime irrigation (4 x 1 mm d–1). The cooling benefit was defined as the air temperature difference measured at 1.1 m above the turfgrass between the irrigated and unirrigated treatments (air temperature sensor accuracy ± 0.2 ◦C). The afternoon (12:00–15:59) mean cooling benefit of multiple daytime irrigation (–0.9 ◦C) which was significantly stronger than that of single night-time irrigation (–0.6 ◦C) and single daytime irrigation (–0.5 ◦C). Regardless of irrigation scheduling, the afternoon mean cooling benefits of irrigation were greater for days when background air temperature, vapour pressure deficit and incoming shortwave radiation were greater. The findings suggested that irrigation scheduling can be optimised to increase the cooling benefit of urban green space irrigation without increasing overall water use.

Urban tree canopy cover is a promising solution for mitigating heat island. • Data-driven guidance on tree selection and planting locations is still limited. • Four research priorities are proposed, requiring a collaborative research effort. • Cross-climate morphological and physiological characteristics are desired. • Integration with atmospheric boundary layer models is suggested.

High temperatures in summer can prevent people from using urban green spaces. Irrigating urban green spaces is a promising strategy to reduce temperatures. In this study, we aimed to a) identify the proportional contribution of different irrigation cooling mechanisms and b) quantify the impacts of different irrigation amounts (from 2 to 30 mm d − 1) on the cooling effect of irrigating turfgrass in Melbourne, Australia. We first used a field experiment in Melbourne to provide empirical data to calibrate and verify the performance of an urban ecohydrological model, UT&C. Then, we used UT&C to predict the impacts of irrigating turfgrass on evapotranspiration, the energy balance and microclimate. UT&C predicted that irrigating turfgrass 4 mm d − 1 would increase the evaporation from grass canopy and soil surface by 0.2 and 0.6 mm d − 1 , respectively, whereas it would reduce transpiration by 0.6 mm d − 1 due to intercepted water covering part of the grass canopy following the irrigation. UT&C predicted that daytime (10:00-16:59) mean air temperature reductions would increase from 0.2 to 0.4 • C when the irrigation amount increased from 2 to 4 mm d − 1. However, increasing the irrigation amount beyond 4 mm d − 1 would not increase the cooling benefits.