Urban forests, integral to Green Infrastructure (GI) and delivering Nature-based Solutions (NbS), play a pivotal role in mitigating the Urban Heat Island (UHI) effect and enhancing urban thermal comfort. The cooling effectiveness of urban trees is influenced by functional traits that determine their shading capacity and evapotranspiration rates. While trait-service relationships have been proposed to guide species selection for improved microclimate outcomes, their interplay with contextual factors, such as solar irradiance, remains underexplored. This study investigates the cooling potential of four morphologically distinctive urban tree species in Canberra, Australia, characterised by a distinctive inland Mediterranean climate. In contrast to many prior studies that rely on single heat metrics and summer midday snapshots, this study analyses seasonal and daytime variations by modelling interactions between seasons and surface materials, and between functional traits and solar irradiance. Linear mixed-effects models were employed to quantify the contribution and significance of these factors to reductions in Surface Temperature (ST) and Wet Bulb Globe Temperature (WBGT). Crown density emerged consistently as a significant trait that was positively correlated with reductions in both ST and WBGT, whereas other traits showed indicator-specific and context-dependent effects. Notably, traits that improve surface cooling might be counterproductive for thermal cooling, revealing potential trade-offs between UHI mitigation and thermal stress reduction. The findings underscore that trait-service relationships can vary with solar irradiance. This study highlights the need for strategic tree species selection, integrating appropriate functional traits within specific urban contexts, to optimise urban microclimatic benefits.

Gaps have a significant influence on forest structure and development. This study analysed characteristics of gaps between secondary and old–growth forests in Kon Ka Kinh National Park, Gia Lai Province, Vietnam. One hectare inventory plots were established in each forest stage. Data on gap size, coordinates, average height of surrounding trees, slope and directions of main axes were recorded. Results showed that the secondary forest had slightly higher number of gaps, compared to old–growth forest. However, the average size of gaps was smaller. Frequency distributions were significantly different between the two forest stages. The size of the gaps correlated with the height of the surrounding forest canopy but there was no correlation with slope. The length direction of gaps was most concentrated at East–North–East in both forest types. The distribution of gaps were regular at a scale of 0 to about 15 m, but were random at larger distances. The gap size spatial distribution was random in the secondary forest, but 60

Increasing drought pressure under anthropogenic climate change may jeopardize the potential of tropical forests to capture carbon in woody biomass and act as a long-term carbon dioxide sink. To evaluate this risk, we assessed drought impacts in 483 tree-ring chronologies from across the tropics and found an overall modest stem growth decline (2.5% with a 95% confidence interval of 2.2 to 2.7%) during the 10% driest years since 1930. Stem growth declines exceeded 10% in 25% of cases and were larger at hotter and drier sites and for gymnosperms compared with angiosperms. Growth declines generally did not outlast drought years and were partially mitigated by growth stimulation in wet years. Thus, pantropical forest carbon sequestration through stem growth has hitherto shown drought resilience that may, however, diminish under future climate change.

Climate change has a negative impact on the vitality of forests, and drought and heatwaves are the most influential abiotic stressors that contribute to tree health decline and mortality. Urban trees are not only vulnerable to climate change, but they also face harsh environmental conditions, including the urban heat island effect, limited soil volume and water availability. Therefore, the long-term sustainability of urban forests relies on healthy and thriving trees and the identification of species that are resilient to climate change. Thus, it is fundamental to understand how urban trees respond to environmental conditions, including climate. This study investigates how urban trees respond to both long-term climatic conditions and episodic extreme climate events. We evaluated variation in urban tree growth across differing climates by reconstructing growth histories and developing drought response indices. We selected 10 tree species planted in seven cities distributed along temperature and precipitation gradients across the Australian continent. We determined spatial and temporal patterns of tree-ring growth in relation to extreme climate events. We found significant differences among cities, suggesting that local environmental conditions significantly influence tree growth. While some species showed fast annual growth in cool and wet cities, other species had similar growth across all cities or even faster growth in hot and dry cities. Urban trees generally responded positively to wetter conditions during the warmest month, which might be related to longer growing seasons and water availability. We found a positive effect of extreme hot conditions on growth, suggesting that urban trees might be well adapted to warm urban environments. Species climate-growth relationships can help guide species selection to maximize benefits delivered by urban forests and minimize environmental and socio-economic losses under current and future climates.

The Australia-New Zealand Tree-Ring Conference was held January 21-23, 2025, at Waipapa Taumata Rau/University of Auckland, in Aotearoa/New Zealand. It was intended to provide an opportunity for the Australian and New Zealand dendrochronological researchers to meet, present current research, and discuss the challenges and opportunities in working with Southern Hemisphere tree species, but it was open to others outside of Australasia, including some keynote speakers. The meeting brought together many researchers from within and outside academia for the first time since the pandemic, and in addition to providing a look at current interesting and ongoing dendrochronology projects, it promoted camaraderie for this regional tree-ring community.

Subalpine forests worldwide face the synergistic threats of global warming and increased biotic attack, and the collapse or transition of subalpine forests is predicted in south-eastern Australia under future climates. The recent widespread dieback of subalpine snow-gum forests due to increased activity of a native wood-boring longicorn beetle, Phoracantha mastersii, suggests this process may already be underway. We investigated how variation in tree tissue traits and environmental conditions correlated with elevation-dependent spatial patterns of forest mortality. We hypothesized that increased vulnerability of subalpine snow gums to wood-borer-mediated dieback at intermediate elevations was associated with poorly resolved differences in traits between montane (Eucalyptus pauciflora subsp. pauciflora) and subalpine (E. pauciflora subsp. niphophila) snow-gum subspecies. We first sought to characterize variation and elevation-dependent transitions in 20 structural and drought-related functional traits among 120 healthy trees distributed along a 1000 m elevation transect that spanned the subspecies transition zone. Secondly, we surveyed 774 trees across 53 sites between 1280 and 1980 m a.s.l. to explore associations between borer-damage severity, elevation, subspecies and a subset of traits that differed between subspecies. We observed evidence for both continuous trait variation in response to changing elevation (10/20 traits) and discrete shifts in mean trait values across the transition between subspecies distributions (5/20 traits). Increased borer-damage severity across the montane-to-subalpine subspecies transition was correlated with lower bark thickness, whereas reduced borer damage at the highest elevations was associated with greater precipitation and lower temperatures. Our results suggest that due to possessing distinct traits associated with increased borer susceptibility, subalpine snow-gum forests may be subject to an increased risk of severe borer-mediated forest dieback under warmer and drier future climates. Identifying traits contributing to species' distribution limits and biotic-agent vulnerability remains critical for predicting, monitoring and possibly mitigating forest and vegetation declines under future climates. We hypothesized that increased vulnerability of subalpine snow gums to wood-borer-mediated dieback at intermediate elevations may be associated with poorly-resolved differences in traits between montane and subalpine snow-gum subspecies. We found that elevation-dependent patterns of wood-borer-mediated dieback were associated with differences in bark thickness between montane and subalpine snow-gum forests, as well as with elevation-associated variation in precipitation and temperature.image

Observations suggest that sudden canopy decline and death of widely dispersed individual trees, associated with wood-borer infestations, has recently expanded and intensified within high-elevation Eucalyptus pauciflora and E. lacrimans stands on the Kosciuszko massif, southeast Australia. Despite reports of insect infestations and associated tree decline over four decades, the phenomenon has been poorly understood and the identity of the associated wood-borer taxon only anecdotally resolved. We conducted a systematic study of sub-alpine forests in Kosciuszko National Park, NSW, with the intent of building a knowledge base of the phenomenon’s aetiology and guiding ongoing research priorities. Using 10-metre radius plots positioned on elevational transects in areas under shared management for snow-based recreation and conservation and areas managed for conservation-only, we found a strong association between increasing severity of wood-borer feeding galleries and decline of canopy condition. The presence of even the first indicators of insect infestation was associated with a three-fold increase in declining canopy condition. Two-way contingency analysis revealed that increasing severity of feeding galleries corresponded with a highly significant decline in canopy-condition. Indicators of wood-borer infestation held greater explanatory power for deteriorating crown condition, than the converse, indicating that wood-borer infestation more likely precede, than follow, canopy decline and death. Based on insect detections over three years and consistency between observed and previously described wood-borer damage, it is unambiguously clear that the native cerambycid species Phoracantha mastersi is principally responsible for insect galleries in affected trees. Detections were associated with warm daily temperature maxima. Modelling of the incidence and severity of infestations indicated elevation and land-management status were significant predictors for the probability of wood-borer infestation at stand and tree levels. The same predictors were significant for predicting the proportion of stand basal area affected. Combined with temporal patterns in insect detections, our modelling results suggest that low temperatures play a key role in limiting upward migration of infestations. While we suspect that fragmentation of forest cover within shared-management areas favours short-distance dispersal and local intensification, an increase in forest-edges may also account for both greater frequency and severity of stand-level infestations in shared-management areas. Mindful of an apparent lower limit to P. mastersi infestations at the interface of affected/unaffected eucalypt taxa, we advocate for greater understanding of physiological traits affecting tree-level vulnerability to infestation. Further, reflecting their roles in Phoracantha infestations elsewhere, we regard resolving the combined roles of temperature and drought stress in initiating outbreaks as particularly important. Similarly, consistent with the effect of land-management status on P. mastersi infestations, improved knowledge of the spatial and temporal attributes of Phoracantha-induced dieback in snow-gum forests is needed.

High-resolution palaeoclimate proxies are fundamental to our understanding of the diverse climatic history of the Australian mainland, particularly given the deficiency in instrumental datasets spanning more than a century. Annually resolved, tree-ring-based proxies play a unique role in addressing limitations in our knowledge of interannual to multi-decadal temperature and hydroclimatic variability prior to the instrumental period. Here we present cross-dated ring-width (RW) and minimum blue-intensity (BI) chronologies spanning 70 years (1929–1998) for Podocarpus lawrencei Hook.f., the Australian mainland's only alpine conifer, based on nine full-disc cross-sections from Mount Loch in the Victorian Alps. Correlations with climate variables from observation stations and gridded data across the 1929–1998 period reveal a significant positive relationship between RW and mean monthly maximum temperatures in winter throughout central Victoria (r=0.62, p<0.001) and a significant negative correlation to winter precipitation (r=-0.51, p<0.001). We also found significant negative correlations between RW and monthly snow depth at Spencer Creek in New South Wales (r=-0.60, p<0.001). Of the assessed BI parameters, delta blue intensity (ΔBI; the difference between early- and late-wood BI) displayed the greatest sensitivity to climate, with robust spatial correlations with mean October to December maximum and minimum monthly temperatures (r=-0.43, p<0.001; r=-0.51, p<0.001) and July precipitation (r=0.44, p<0.001), across large areas of northern Victoria. These promising findings highlight the utility of this species for future work. With the very limited availability of suitable long-lived and cross-datable species on the Australian mainland, these results have significant implications for advancing high-resolution palaeoclimate science in southeastern Australia and for improving our understanding of past climate in the region.

High-resolution palaeoclimate proxies are fundamental to our understanding of the diverse climatic history of the Australian mainland, particularly given the deficiency in instrumental datasets spanning greater than a century. Annually resolved, tree-ring based proxies play a unique role in addressing limitations in our knowledge of interannual to multi-decadal temperature and hydroclimatic variability prior to the instrumental period. Here we present cross-dated ring-width (RW) and minimum blue-intensity (BI) chronologies spanning 70 years (1929 – 1998) for Podocarpus lawrencei Hook.f., the Australian mainland's only alpine conifer, based on nine full-disk cross-sections from Mount Loch in the Victorian Alps. Correlations with climate variables from observation stations and gridded data reveal a significant positive relationship between RW and mean monthly maximum temperatures in winter throughout central Victoria (r = 0.62, p < 0.001), and a significant negative correlation to winter precipitation (r = -0.51, p < 0.001). We also found significant negative correlations between RW and monthly snow depth data from Spencer Creek in New South Wales (r = -0.60, p < 0.001). Of the assessed BI parameters, delta blue-intensity (ΔBI; the difference between early- and late-wood BI) displayed the greatest sensitivity to climate, with robust spatial correlations with mean October to December maximum and minimum monthly temperatures (r = -0.43, p < 0.001; r = -0.51, p < 0.001) and July precipitation (r = 0.44, p < 0.001), across large areas of northern Victoria. These promising findings highlight the utility of this species for future work. With the very limited availability of suitable long-lived and cross-datable species on the Australian mainland, these results have implications for the significant advancement of palaeoclimate records in southeastern Australia and the potential for improvement in our understanding of past climate in the region.

Climate projections indicate that dangerous fire weather will become more common over the coming century. We examine the potential of a network of temperature- and moisture-sensitive tree-ring sites in southeastern Australia to reconstruct the number of high fire-danger days for the January–March season. Using the Forest Fire Danger Index (FFDI), we show that modestly statistically skilful reconstructions for the far southeast of Australia (western Tasmania), where the majority of tree-ring predictors are located, can be developed. According to the averaged reconstructions for the 1590–2008 period, there have been 16 years prior to the start of the FFDI records (1950), and 7 years since 1950, with >48 (mean + 1σ) high fire-danger days in the 3-month season. The western Tasmanian reconstructions indicate extended relatively high fire-danger periods in the 1650s–1660s and 1880s–1890s. Fire danger has also been relatively high since 2000 CE. A persistent increase in the number of high fire-danger days over the past four decades has not been matched over the previous 390 years. This work indicates it is possible to produce statistically useful reconstructions of high seasonal fire danger – as opposed to fire occurrence – but that availability of local proxy records is key.

Increasing [CO2] may influence commercial crop and timber yield. While selection of genotypes sensitive to elevated [CO2] (e[CO2]) appears possible in agricultural crops, there is limited evidence for genotype-by-CO2 (G × CO2) interactions in commercial tree species. We examined [CO2] responsiveness in 124 open-pollinated Eucalyptus globulus ssp. globulus (E. globulus) families with the aim of assessing whether G × CO2 interactions are detectable in seedlings for early-age screening. Plants were grown in ambient (a[CO2]; ~ 405 μmol mol−1) and e[CO2] (640 μmol mol−1) and harvested 25 days after germination. Total, shoot, and root dry weights were determined for each plant. Carbon isotopic discrimination against 13C (Δ13C) was determined at the family level. We observed highly significant (p < 0.0001) increases in mean total, shoot, and root dry weights. Mixed-model equations were used to estimate the main and interaction effects of the G × CO2 for each mass trait. The main effects from the mixed-model output ([CO2] and individual-tree effects) were significant for all traits. However, [CO2]-by-individual tree interactions were non-significant for all traits, indicating little G × CO2 interaction. A secondary aim was to examine the correlation between greenhouse and mature-age growth from breeding trials that use common families conducted under ambient [CO2]. These correlations were non-significant, suggesting early growth is not necessarily indicative of later-age responses. Our results suggest that while early growth of E. globulus is enhanced under e[CO2], genotypes respond relatively uniformly to e[CO2] and little opportunity exists for seedling-based selection at the population level based upon the response of plants during the first weeks of growth.

An understanding of tropical hydroclimate variability, the associated drivers and how it is likely to change is a major scientific and societal challenge that is acutely hampered by short instrumental records. We present a 246year tree-ring drought reconstruction of the Standardised Precipitation Evaporation Index (SPEI) for monsoonal northern Australia for the end of the wet season (March-May; MAM). This reconstruction extends the instrumental record back by 150 years. Around one third of total annual rainfall falls during MAM, making it a crucial component of the monsoonal cycle. MAM is also the season most impacted by the differential decay process of Central Pacific (as opposed to Western Pacific) El Nino events that are linked with dry conditions over northern and northwestern Australia more generally. Our reconstruction therefore provides an opportunity to consider how central Pacific variability has modulated MAM hydroclimate in Australia's monsoonal north over the past two and a half centuries. We found that MAM hydroclimate extremes in the region have a strong, but asymmetric relationship with central Pacific sea surface temperatures (SSTs) and ENSO indices. Extremely wet MAMs in monsoonal north Australia were associated with cooler SSTs, above average rainfall across much of Australia, and often coincided with La Nina events. The spatial relationship between dry extremes and Pacific SSTs during dry events was generally, but weakly, consistent with the SST signature of central Pacific El Nino events. The association between reconstructed dry extremes in the monsoonal north and dry conditions across the rest of Australia is also less extensive and weaker than for wet events. Results suggest that more extreme wet events in the Australian monsoonal north likely reflect cool central Pacific SSTs and later termination of the Australian monsoon. Consecutive years with extremely dry MAMs became more frequent over the latter part of the 20th Century while the probability of an extreme dry MAM followed by an extreme wet MAM the next year peaked in the mid 20th Century and has since declined.

Volunteer labour is often used for planting native seedlings for revegetation projects. The survival of such plantings is seldom monitored and reported. The overall survival of seedlings at three years of age was assessed for eight years of plantings established by nearly 15,000 volunteers in the Lower Cotter River catchment in the Australian Capital Territory. Mean survival was 66.8% across all years. We conclude that volunteers can be effectively integrated into large-scale revegetation projects if they are well trained and organised.

ABSTRACT The study of materials that comprise artworks significantly contributes to understanding of age and provenance. While dendrochronology is a particularly valuable and well-established technique for panel paintings comprising oak timber, conventional practices of resurfacing end-grains to reveal tree rings is becoming less acceptable because it removes material, modifying the painting. Recently, application of non-destructive X-ray fluorescence (XRF) spectroscopy to a portrait of Henry VIII held by the Art Gallery of New South Wales (AGNSW), Sydney, Australia revealed tree-ring boundaries in the resulting high-resolution elastic scatter XRF map. In this study, we examine the dendrochronological potential of that mapping with the aim of contributing to resolving the relationship of the AGNSW portrait to similar paintings elsewhere. Examination of the timber revealed affinities with Quercus petraea (Matt.). We measured tree-ring widths along multiple paths in the XRF scatter map and crossdated the resulting 81-year XRF ring-width (XRF portrait ) series against master chronologies of English, western European, and Baltic origin. Rather than an arbitrarily defined threshold, we used a Bonferroni correction to determine a minimum significance level for crossdating. While the XRF portrait series did not crossdate with the continental European chronologies, we identified a single significant (α = 3.4 × 10−6) dating position with the English chronology (1400–1480 CE). Cross-matching with site-level chronologies revealed a cluster of high t-values in central-southern England. The earliest date of felling precedes the documented date of completion for the AGNSW and two similar Tudor portraits of Henry VIII held by the National Portrait Gallery (NPG), London and one at the Society of Antiquaries, London. While the apparent British provenance of timber used in the AGNSW portrait contrasts to Baltic origin of timbers used for the two NPG portraits and the majority of English panel paintings, it is consistent with the provenance of the timber used for the Society of Antiquaries portrait.

Elevated atmospheric CO2 concentration (e[CO2]) can stimulate the photosynthesis and productivity of C3 species including food and forest crops. Intraspecific variation in responsiveness to e[CO2] can be exploited to increase productivity under e[CO2]. However, active selection of genotypes to increase productivity under e[CO2] is rarely performed across a wide range of germplasm, because of constraints of space and the cost of CO2 fumigation facilities. If we are to capitalise on recent advances in whole genome sequencing, approaches are required to help overcome these issues of space and cost. Here, we discuss the advantage of applying prescreening as a tool in large genome×e[CO2] experiments, where a surrogate for e[CO2] was used to select cultivars for more detailed analysis under e[CO2] conditions. We discuss why phenotypic prescreening in population-wide screening for e[CO2] responsiveness is necessary, what approaches could be used for prescreening for e[CO2] responsiveness, and how the data can be used to improve genetic selection of high-performing cultivars. We do this within the framework of understanding the strengths and limitations of genotype-phenotype mapping.

The ecology of the Australian monsoon tropics is fundamentally shaped by dry conditions between May and October followed by highly variable rainfall over the months of November to April. Due to its crucial ecological importance, a better understanding of past hydroclimate variability in the region is of great interest to land managers and custodians in this region. Short instrumental records also make highly resolved terrestrial palaeoclimate records for northern Australia prior to 1900 CE of considerable scientific importance. Here, we present two new well‐replicated Callitris intratropica ring‐width chronologies from Arnhem Land in northern Australia, one of which extends the tree‐ring record in the region by another 86 years, back to 1761. Both chronologies have clearly defined regional patterns of correlations with temperature, precipitation, potential evapotranspiration and two drought indices (the self‐calibrating Palmer Drought Severity Index ( PDSI ) and the Standardised Precipitation Evapotranspiration Index ( SPEI )) across the lower latitudes of the Northern Territory. Results indicate considerable scope for hydroclimatic reconstructions based on C. intratropica for transitional periods into and out of the wettest time of the year. This suggests that such reconstructions would reflect variability in the duration of the wet period. While precipitation or streamflow reconstructions may be possible for both these transitional periods, drought reconstructions will be best focused on the months of March–May at the end of the wet period. Hydroclimate reconstructions would provide important baseline information for understanding the rate and magnitude of current regional climate change for these ecologically and culturally important transitional periods.