Rachael H. Nolan

Rachael H. Nolan
Western Sydney University · Hawkesbury Institute for the Environment

PhD

About

62
Publications
29,164
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
2,415
Citations

Publications

Publications (62)
Article
Ecological resilience is the capacity of a system to maintain function following disturbance. With the frequency and severity of wildfire activity increasing due to warmer and drier global climate conditions, there are increasing reports of declines in ecological resilience and ecosystems at risk of collapse due to post-fire recovery failure. Obser...
Article
Each year, wild and managed fires burn roughly 4 million km2 [~400 million hectares (Mha)] of savanna, forest, grassland and agricultural ecosystems. Land use and climate change have altered fire regimes throughout the world, with a trend toward higher‐severity fires found from Australia, the Americas, Europe and Asia, to the Arctic. In 2020, there...
Article
Full-text available
Live Fuel Moisture Content (LFMC) is one of the main factors affecting forest ignitability as it determines the availability of existing live fuel to burn. Currently, LFMC is monitored through spectral vegetation indices or inferred from meteorological drought indices. While useful, neither approach provides mechanistic insights into species-specif...
Article
Full-text available
‘Megafire’ is an emerging concept commonly used to describe fires that are extreme in terms of size, behaviour, and/or impacts, but the term’s meaning remains ambiguous. We sought to resolve ambiguity surrounding the meaning of ‘megafire’ by conducting a structured review of the use and definition of the term in several languages in the peer‐review...
Article
Large forest fires generally occur when the moisture content of fuels is low. For live fuels, our understanding of the physiological basis of variation in moisture content has recently advanced. However, process-based models of live fuel moisture content (LFMC) remain elusive. Here, we aim to further our understanding of the role of physiological m...
Article
To estimate loss of above‐ground carbon (AGC) and conversion of live carbon to dead carbon following understorey and canopy fire. South‐eastern Australia. 2019–2020. Four widespread resprouting eucalypt forests. Above‐ground carbon was measured in 15 plots in each of four forest types one‐year post‐fire. We also assessed topkill, that is, trees sub...
Article
The aims were: (1) to identify the environmental drivers of interannual variation in wildfire extent and severity; (2) to examine temporal trends in climatic potential for large and severe wildfires; and (3) to assess whether environmental conditions experienced during the 2019–2020 mega‐fire season were anomalous. South‐eastern Australia. 1953–202...
Article
Full-text available
Wildfires in 2019–2020 broke global records for extent and severity, affirming the arrival of the megafire era. Frequent megafires reflect changes to fire regimes that can negatively impact species and ecosystems. Here, we offer what we believe to be the first comprehensive analysis of megafire impacts on southeastern Australian vegetation communit...
Article
Existing abiotic and biotic threats to plant species (e.g., disease, drought, invasive species) affect their capacity to recover post‐fire. We use a new, globally applicable framework to assess the vulnerability of 26,062 Australian plant species to a suite of active threats after the 2019–2020 fires. Australia. 2019–2020. Plants. Spatial data for...
Article
Accurate estimation of emissions from biomass burning and their impact on carbon storage requires pre and post-fire plot measurement of fuel consumption across a range of forest types and fire severities, and this information is currently far from comprehensive in Australia or elsewhere. We measured fine and coarse fuels in 44 sites before and afte...
Article
Accurate quantification of fine fuel loads (e.g. foliage and twigs) in forests is required for many fire behaviour models, and for assessing post-fire changes in carbon stocks and modelling smoke emissions. Fine fuels burn readily and are thus often targeted for fuel load assessments. Estimates of fine live fuel loads often rely on visual assessmen...
Article
Full-text available
Mistletoes are emerging as important co-contributors to tree mortality across terrestrial ecosystems, particularly when infected trees are stressed by water limitations during drought. While the mechanistic effects of mistletoe infection on host physiology are reasonably well understood, quantifying the effects of mistletoe infection on stand produ...
Article
Full-text available
The 2019–20 Australian fire season was heralded as emblematic of the catastrophic harm wrought by climate change. Similarly extreme wildfire seasons have occurred across the globe in recent years. Here, we apply a pyrogeographic lens to the recent Australian fires to examine the range of causes, impacts and responses. We find that the extensive are...
Article
Full-text available
The 2019/20 Black Summer bushfire disaster in southeast Australia was unprecedented: the extensive area of forest burnt, the radiative power of the fires, and the extraordinary number of fires that developed into extreme pyroconvective events were all unmatched in the historical record. Australia’s hottest and driest year on record, 2019, was chara...
Article
The cover image is based on the Invited Review Limits to post‐fire vegetation recovery under climate change by Rachael H. Nolan et al., https://doi.org/10.1111/pce.14176. The cover image is based on the Invited Review Limits to post‐fire vegetation recovery under climate change by Rachael H. Nolan et al., https://doi.org/10.1111/pce.14176.
Article
Full-text available
Non-technical summary We summarize some of the past year's most important findings within climate change-related research. New research has improved our understanding about the remaining options to achieve the Paris Agreement goals, through overcoming political barriers to carbon pricing, taking into account non-CO 2 factors, a well-designed implem...
Article
Mistletoes are important co-contributors to tree mortality globally, particularly during droughts. In Australia, mistletoe distributions are expanding in temperate woodlands, while their hosts experienced unprecedented heat and drought stress in recent years. We investigated whether the excessive water use of mistletoes increased the probability of...
Article
Full-text available
In Australia, the proportion of forest area that burns in a typical fire season is less than for other vegetation types. However, the 2019−2020 austral spring-summer was an exception, with over four times the previous maximum area burnt in southeast Australian temperate forests. Temperate forest fires have extensive socio-economic, human health, gr...
Article
Full-text available
Record-breaking fire seasons in many regions across the globe raise important questions about plant community responses to shifting fire regimes (i.e., changing fire frequency, severity, and seasonality). Here, we examine the impacts of climate-driven shifts in fire regimes on vegetation communities, and likely responses to fire coinciding with sev...
Article
Full-text available
Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observatio...
Article
Full-text available
Global wildfire activity has experienced a dramatic surge since 2017 [...]
Article
Full-text available
Extreme fire seasons characterised by very large 'mega-fires' have demonstrably increased area burnt across forested regions globally. However, the effect of extreme fire seasons on fire severity, a measure of fire impacts on ecosystems, remains unclear. Very large wildfires burnt an unprecedented area of temperate forest, woodland and shrubland ac...
Article
Eastern Australia was subject to its hottest and driest year on record in 2019. This extreme drought resulted in massive canopy die‐back in eucalypt forests. We examined the role of hydraulic failure and tree size on canopy die‐back in three eucalypt tree species during this drought. We measured pre‐dawn and midday leaf water potential (Ψleaf), per...
Article
Full-text available
Montane ecosystems occur throughout the world, and harbor many endemic species. They also provide key ecological services, including the catchment of water resources and the storage of organic carbon. These ecosystems are vulnerable to global climate change and increasing human pressures, including forestry and their conversion to arable land. In t...
Article
Predicting the impact of wildfires on ecosystem services and habitat values requires quantifying rates of post-fire tree mortality and topkill. For those species that resprout epicormically (i.e. from above-ground buds), rates of post-fire topkill (death of aboveground biomass) can vary considerably. Laboratory studies indicate that bark attributes...
Article
Full-text available
The circadian clock is a molecular timer of metabolism that affects the diurnal pattern of stomatal conductance (gs), amongst other processes, in a broad array of plant species. The function of circadian gs regulation remains unknown and here, we test whether circadian regulation helps to optimize diurnal variations in stomatal conductance. We subj...
Article
Full-text available
Globally, fire regimes are being altered by changing climatic conditions. New fire regimes have the potential to drive species extinctions and cause ecosystem state changes, with a range of consequences for ecosystem services. Despite the co-occurrence of forest fires with drought, current approaches to modelling flammability largely overlook the l...
Article
In a response to our Letter on the causes and consequences of the 2019‐20 forest fires in eastern Australia (Nolan et al. 2020), Adams et al. (XXXX) argued that fuel loads were causal to the occurrence and size of the fires, along with antecedent dryness. They state that fuel levels were ‘extreme everywhere’, resulting from a lack of fuel reduction...
Article
The southern hemisphere and especially Australian arid and semi-arid ecosystems played a significant role in the 2011 global land carbon sink anomaly. Arid and semi-arid regions occupy 70% of the Australian land surface, dominated by two biomes: Mulga woodlands and spinifex grasslands or savannas. We monitored carbon and water fluxes in two of thes...
Article
As the ratio of carbon uptake to water use by vegetation, water‐use efficiency (WUE) is a key ecosystem property linking global carbon and water cycles. It can be estimated in several ways, but it is currently unclear how different measures of WUE relate, and how well they each capture variation in WUE with soil moisture availability. We evaluated...
Article
Full-text available
The 2019‐20 fire season in eastern Australia is attracting considerable national and international attention. At the time of writing c. 3.8 million ha of mainly temperate forest have burnt in the state of New South Wales (NSW; NSW Rural Fire Service, 29/12/2019; Fig. 1a). Major blazes are also occurring in other states, including over 0.5 million h...
Article
Full-text available
Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research sp...
Article
Full-text available
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Article
Full-text available
Globe-LFMC is an extensive global database of live fuel moisture content (LFMC) measured from 1,383 sampling sites in 11 countries: Argentina, Australia, China, France, Italy, Senegal, Spain, South Africa, Tunisia, United Kingdom and the United States of America. The database contains 161,717 individual records based on in situ destructive samples...
Article
The deforestation and degradation of natural habitats is the second largest contributor to carbon dioxide (CO2) emissions to the atmosphere. Temperate forests cover ∼16.5% of the Mexican landscape, and are a priority ecosystem for global conservation due to their high rate of endemism and species diversity. These forests also provide valuable ecosy...
Article
Extreme disturbance events, such as wildfire and drought, have large impacts on carbon storage and sequestration of forests and woodlands globally. Here, we present a modelling approach that assesses the relative impact of disturbances on carbon storage and sequestration, and how this will alter under climate change. Our case study is semi-arid Aus...
Article
The moisture content of live fuels is an important determinant of forest flammability. Current approaches for modelling live fuel moisture content typically focus on the use of drought indices. However, these have mixed success partly because of species-specific differences in drought responses. Here we seek to understand the physiological mechanis...
Article
Full-text available
Groundwater-dependent vegetation is globally distributed, having important ecological, social, and economic value. Along with the groundwater resources upon which it depends, this vegetation is under increasing threat through excessive rates of groundwater extraction. In this study we examined one shallow-rooted and two deep-rooted tree species at...
Article
Reforestation schemes, which encompass environmental plantings and natural regeneration of vegetation on cleared land, are increasingly being established for the purposes of mitigating anthropogenic carbon emissions. However, these schemes are themselves at risk from climate change and associated changes in disturbance regimes. Simultaneously, ther...
Article
Arid environments can support the seemingly unlikely coexistence of species tolerant of, or sensitive to, dry soil moisture. Here, we examine water-use and carbon-gain traits in two widespread tree species in central Australia: Acacia aptaneura and Eucalyptus camaldulensis. The former has a shallow root distribution and relies on soil moisture, whi...
Article
Xylem traits such as xylem vessel size can influence the efficiency and safety of water transport and thus plant growth and survival. Root xylem traits are much less frequently examined than those of branches despite such studies being critical to our understanding of plant hydraulics. In this study, we investigated primary lateral and sinker roots...
Article
Carbon abatement schemes that reduce land clearing and promote revegetation are now an important component of climate change policy globally. There is considerable potential for these schemes to operate in drylands which are spatially extensive. However, projects in these environments risk failure through unplanned release of stored carbon to the a...
Poster
Full-text available
Mulga woodlands and hummock grasslands cover vast portions of the Australian interior, where their large fluctuations in carbon budget can have global implications. Abiotic decomposition as a result of photo-degradation (i.e., light-mediated breakdown of lignin in leaf litter) can be a major source of carbon to the atmosphere in these ecosystems, e...
Article
Many ecosystems located within agricultural landscapes are in decline, particularly woodlands, grasslands and wetlands. Surviving remnants are generally fragmented and unrepresentative of pre-disturbance states. Here, we investigate the potential for recovery of ecosystem function in a grassy woodland–wetland mosaic in south-eastern Australia. We f...
Article
Croplands play a vital role in regional carbon budgets. We hypothesized that biophysical factors would be important for soil respiration in a wheat-maize rotation cropping system. Soil CO2 efflux was measured using the closed chamber method, and net CO2 exchange between the cropland and the atmosphere obtained by the eddy covariance technique in a...
Article
Changing frequencies of extreme weather events and shifting fire seasons call for enhanced capability to forecast where and when forested landscapes switch from a non-flammable (i.e. wet fuel) state to the highly flammable (i.e. dry fuel) state required for catastrophic forest fires. Current forest fire danger indices used in Europe, North America...
Article
Partitioning of water resources amongst plant species within a single climate envelope is possible if the species differ in key hydraulic traits. We examined 11 bivariate trait relationships across nine woody species found in the Ti-Tree basin of central Australia. We found that species with limited access to soil moisture, evidenced by low pre-daw...
Article
Low soil water content can limit photosynthesis by reducing stomatal conductance. Here, we explore relationships among traits pertaining to carbon uptake and pre-dawn leaf water potential (as an index of soil water availability) across eight species found in semiarid central Australia.Wefound that as pre-dawn leaf water potential declined, stomatal...
Article
Full-text available
Species are often classified along a continuum from isohydric to anisohydric, with isohydric species exhibiting tighter regulation of leaf water potential through stomatal closure in response to drought. We investigated plasticity in stomatal regulation in an isohydric (Eucalyptus camaldulensis) and an anisohydric (Acacia aptaneura) angiosperm spec...
Article
To better understand water and energy cycles in forests over years to decades, measurements of spatial and long-term temporal variability in evapotranspiration (Ea) are needed. In mountainous terrain, plot-level measurements are important to achieving this. Forest inventory data including tree density and size measurements, often collected repeated...
Article
Full-text available
Mulga, comprised of a complex of closely related Acacia spp., grades from a low open forest to tall shrublands in tropical and sub-tropical arid and semi-arid regions of Australia and experiences warm-to-hot annual temperatures and a pronounced dry season. This short synthesis of current knowledge briefly outlines the causes of the extreme variabil...
Article
The occurrence of large, high-intensity wildfires requires plant biomass, or fuel, that is sufficiently dry to burn. This poses the question, what is "sufficiently dry"? Until recently, the ability to address this question has been constrained by the spatiotemporal scale of available methods to monitor the moisture contents of both dead and live fu...
Article
Spatially explicit predictions of fuel moisture content are crucial for quantifying fire danger indices and as inputs to fire behaviour models. Remotely sensed predictions of fuel moisture have typically focused on live fuels; but regional estimates of dead fuel moisture have been less common. Here we develop and test the spatial application of a r...
Article
Full-text available
The objective of this study was to estimate the recovery trajectory of evapotranspiration (Et) and streamflow (Q) in resprouting forested catchments following wildfire. Recovery dynamics were assessed in mixed species eucalypt forests in south-eastern Australia which recover from disturbance largely via vegetative resprouting, and to a lesser degre...
Article
The moisture content of vegetation and litter (fuel moisture) is an important determinant of fire risk, and predictions of dead fine fuel moisture content (fuel with a diameter <25.4 mm) are particularly important. A variety of indices, as well as empirical and mechanistic models, have been proposed to predict fuel moisture, but these approaches ha...
Article
Full-text available
Forests which recover from disturbance predominately via vegetative resprouting may be expected to have different catchment water balance dynamics following wildfire than forests recovering from seed. However, the impacts of wildfire on forest water use are largely unknown in resprouting forest types. This is despite their dominance across the majo...
Article
Full-text available
Following disturbance many woody species are capable of resprouting new foliage, resulting in a reduced leaf-to-sapwood area ratio and altered canopy structure. We hypothesized that such changes would promote adjustments in leaf physiology, resulting in higher rates of transpiration per unit leaf area, consistent with the mechanistic framework prop...
Article
Fire induced changes to the vegetation dynamics in temperate forests have been demonstrated to affect evapotranspiration (Et) rates through increases in plant size and density and stand-level transpiration and interception. In many cases these transient changes in forest structure result in substantial declines in stream flow for protracted periods...
Article
Full-text available
Broadscale land use changes are occurring rapidly in rural landscapes worldwide, within which revegetation with native plant species to increase the area of suitable habitat is a key activity. Current models for planning revegetation are based solely on the spatial arrangement of new and remnant vegetation. Making wise decisions about revegetation...

Network

Cited By

Projects

Projects (2)
Project
The goal of this project is to test hypotheses regarding plant and ecosystem function with respect to water, carbon, momentum and energy fluxes in the highly variable hydroclimate of semi-arid central Australia. This project encompasses studies of ecohydrology, plant ecophysiology, remote sensing and phenology, the ecosystem carbon cycle and meteorology. Our research focuses upon three widespread biomes across Australia: Mulga (Acacia spp) woodland/savanna, depending upon conditions; very open Bloodwood/Corkwood savanna (Corymbia opaca and Hakea spp., respectively) with a dominant understorey of the drought-tolerant C4 hummock grass Spinifex (Triodia spp.); and Redgum (Eucalyptus camaldulensis) riparian forest, which is groundwater dependent.
Project
This project is an attempt to partition carbon fluxes from a site with a strong source strength due to abiotic decomposition as a result of photo-degradation. Because abiotic decomposition does not respond to environmental conditions in the same way as heterotrophic or autotrophic respiration, traditional methods generate spurious GPP losses to the atmosphere. Thus, alternative methods like correlation analysis must be applied to the problem.