Germination and seedling establishment are critical stages for the maintenance of native trees in woodlands affected by wildfires. According to the Janzen-Connell hypothesis, individuals growing in the vicinity of conspecific mature trees will display negative plant-soil feedbacks (PSF) due to soil-borne pathogens adapted to conspecific rhizosphere soil. On the other hand, compatible ectomycorrhizal fungi can favour seedling establishment near conspecifics through positive PSF. We tested the effect of heat on PSF using a fully reciprocal experiment involving two Allocasuarina and two Eucalyptus species co-occurring in heathy woodlands. Seeds and soil were collected in the Cranbourne bushland conservation area in SE Melbourne, Victoria. Each soil type was subjected to heat treatment, resulting in four heated soils and four native soils. We conducted seed germination and pot trials for one month and eight months, respectively, and recorded germination success, plant growth, biomass allocation, as well as soil and root mycobiomes using ITS2 fungal metabarcoding. Germination did not vary with soil type, however, the combined effect of nutrients and microbes significantly affected seedling growth and biomass. All species showed a positive growth response in A. littoralis soil, while seedlings grown in A. paradoxa soil, including A. paradoxa, showed the least performance. Heat treatment reduced both positive and negative PSF, with putative consequences for seedling survival and the maintenance of tree diversity in woodlands affected by wildfire regimes.

Plant-soil interactions are integral to the terrestrial carbon cycle as they underpin photosynthesis and soil respiration. Soil microorganisms rely on resources provided by plants via root exudates and detritus and plants rely on soil microbes for key processes in nutrient cycling such as nitrogen fixation. These interactions are also intimately tied to changes in climate. Climate warming may stimulate plant growth and soil respiration; in contrast, increased drought frequency or intensity is generally predicted to be detrimental for plant growth and to reduce soil respiration. Changes in plant communities, through shifts in biomass, abundance or species composition as a result of warming and drying, have implications for soil communities with follow on effects to the terrestrial carbon cycle. Here, we report on an in situ global change experiment in the Australian sub-alpine investigating the effects of warming and drought on a grassland, simulating a severe drought under a future climate temperature regime (2070-2100). The whole soil profile to 1m depth was warmed using metal heating rods powered by solar panels in the field, and rain-out shelters implemented to block approx. 80% precipitation. We measured plant species composition, above and belowground biomass, soil respiration, substrate induced microbial respiration and net ecosystem exchange. Results suggest there have been shifts in microbial biomass as a result of 2.5 years of treatments while no changes in above or belowground biomass are as yet detectable. Results demonstrate that variation in annual precipitation is a major factor in driving carbon cycling and thus far a more powerful driver than the warming treatment. The results of this study will have relevance to understanding plant-soil interactions of Australia’s alpine grasslands and how this in turn affects carbon dynamics and can be used to draw comparisons with grasslands globally.

Understanding mechanisms of community assembly is a fundamental goal of plant ecological research, yet the processes shaping species assembly along elevational gradients remain poorly understood. Here, we investigated subtropical and tropical montane tree communities to examine how functional trait variation and ecological strategies respond to elevation and how these patterns are influenced by climate and soil conditions. We analyzed key plant functional traits—including leaf morphological and chemical traits, wood density and maximum plant height—to characterize patterns of trait variation along elevation and infer the underlying assembly rules. Additionally, we applied Grime’s CSR (Competitor, Stress-tolerator, Ruderal) framework to assess shifts in community-level ecological strategies and used partial least squares path modeling to quantify how climate and soil affect CSR strategies in these subtropical and tropical forests. Both trait convergence and divergence were observed at low and high elevations, but their patterns differed markedly between biomes, and among traits. Elevational variation in CSR strategies and their drivers also differed between biomes. In subtropical forests, soil primarily shaped CSR strategies, with C and R strategies decreasing then increasing with elevation, while S showed the opposite trend. In tropical forests, climate primarily drove CSR patterns, with C declining and S increasing, while soil influenced R, which decreased with elevation. These findings demonstrate that multiple ecological processes—including environmental filtering, limiting similarity, equalizing fitness processes, and facilitation—jointly shape montane tree community assembly, and that assembly mechanisms depend strongly on regional climatic context.

Fire has been pivotal in shaping much of the Australian landscape, with many native species now dependent on its occurrence to persist. Despite this, fires that diverge from historical regimes are recognised as posing a significant threat to native species and the environment, although the specific mechanisms behind this are poorly understood. With increasing pressures from climate change amplifying the risk of more frequent and severe wildfires, understanding how different fire regimes influence ecosystem recovery is critical to guide future conservation and land management strategies.
This project aims to fill this knowledge gap by investigating the effects of wildfire and prescribed burns on native plant community structure and soil microbial richness, diversity, and putative functions in Marri (Corymbia calophylla) and Jarrah (Eucalyptus marginata) forests of south-west Western Australia (WA) to understand their recovery potential. Vegetation surveys were conducted using transects across four paired burnt and unburnt (control) sites in Meelup Regional Park to assess plant diversity, percentage cover and functional persistence strategies. Soil samples were collected for chemical analysis and high-throughput DNA sequencing to identify microbial communities and their putative ecological functions.
The outcomes from this study will raise awareness of the importance of microbial interactions and their contributions to the resilience and health of ecosystems. In particular, the study will highlight how different fire regime characteristics can influence biodiversity at multiple levels in diverse fire-dependent landscapes such as the Marri-Jarrah forests of south-west WA. By improving our understanding of how different ecosystem components respond to different fire regimes, these findings will support the development of targeted, adaptive fire management strategies to conserve biodiversity and build ecological resilience in a rapidly changing climate.

Mycorrhizal fungi play a critical role in forest nutrient cycling, productivity, carbon sequestration, and overall ecosystem functions. Industrialisation has significantly increased nitrogen (N) deposition in Australian temperate forests. Studies from the Northern Hemisphere show that elevated N can shift forest tree composition through belowground changes in mycorrhizal associations, and these effects can be exacerbated by drought. However, these dynamics remain largely unexplored in Australia, where soils are notoriously nutrient-poor and endemic flora may not respond according to Northern Hemisphere paradigms.
As both N fertilisation and drought can alter the mycorrhizal dependency of trees, their combined impacts likely undermine key mycorrhizal-mediated processes—compromising nutrient exchange, degrading soil structure, and threatening overall forest resilience. Understanding these interactions is therefore essential for guiding adaptive forest management.
To investigate these dynamics, we characterised mycorrhizal fungal communities in 128 soil samples from south‑eastern Australian temperate forests using DNA metabarcoding across soil N and soil moisture gradients. Using a causal‑modelling framework, we will test how soil N and moisture influence mycorrhizal fungal diversity.
To investigate these processes, we characterised mycorrhizal fungal communities from 128 soil samples collected in temperate forests of south-eastern Australia. Using DNA metabarcoding, we captured fungal diversity across soil N and moisture gradients. Through a causal-modelling framework, we aim to test how these environmental drivers influence fungal community composition.
We hypothesise that elevated mineral N (our proxy for N deposition) will disproportionately benefit nitrophilic fungal guilds—those adapted to exploiting inorganic N—at the expense of taxa specialised in acquiring organic N. We further predict that this shift will be amplified under reduced soil moisture (our proxy for drought).

There is great potential to align biodiversity and carbon targets in revegetation projects to combat the climate and biodiversity crises simultaneously. Despite empirical evidence that woody plant diversity can enhance carbon sequestration aboveground, carbon projects often consist of monocultures of fast-growing exotic species. Additionally, projects tend to only account for plant biomass carbon, ignoring the substantial carbon pool in soils. This is partly due to the complex nature of and limited data on soil carbon dynamics. In this study, we tested the relationship between woody plant diversity and soil carbon storage, including underlying mechanisms, in a 14-year-old tree diversity experiment in Western Australia’s wheatbelt region. We found no trade-off in soil carbon storage between York gum monocultures and diverse plantings of York gum, native trees and shrubs. Variations in soil carbon stocks were largely explained by soil properties (e.g., nitrogen concentration). Diverse plantings had higher woody aboveground biomass, resulting in greater overall carbon storage than York gum monocultures, and showed trends towards higher litter quality and decomposition rate. This study provides valuable insights into the role of plant diversity in carbon dynamics in a Mediterranean biome. Next, we will synthesise data from a global network of tree diversity experiments (TreeDivNet) to explore the environmental and climatic conditions influencing the relationship between woody plant diversity, aboveground and soil carbon storage across different biomes. The dataset contains experiments with a wide range of stand ages, soil properties and climatic conditions. The Western Australian site will contribute data from the understudied Mediterranean biome with its unique climatic conditions. Taken together, these datasets will improve our understanding of the role of woody plant diversity in carbon storage above- and belowground and inform the carbon and emerging nature repair markets.

Plant–plant interactions are key determinants of species coexistence, ecosystem functioning, and evolutionary dynamics. Soil microbial communities can alter these interactions by influencing the relative performance and competitive or facilitative abilities of co-occurring species. However, the role of soil microbes in mediating plant–plant interactions, and the mechanisms by which they operate through plant functional traits, remain poorly understood. To address this gap, we investigated how soil microbial communities affect interactions between two co-occurring annual plants, Waitzia acuminata and Pentameris airoides, native to Western Australia. Previous research suggests that P. airoides facilitates the growth of W. acuminata, though the mechanisms underlying this facilitation are unknown. Building on this knowledge, we tested whether soil microbes mediate this positive interaction. We conducted reciprocal transplant experiments, growing the species pair in both native soils and microbe-free soils. We assessed changes in their interaction dynamics and measured above- and belowground functional traits to infer microbial mechanisms driving facilitation. Our results provide direct evidence that soil microbial communities shape plant–plant interactions, with important implications for understanding diversity maintenance and community dynamics in species-rich ecosystems.