Mortality and recruitment of fire-tolerant eucalypts as influenced by wildfire severity and recent prescribed fire

Mixed-species eucalypt forests of temperate Australia are assumed tolerant of most fire regimes based on the impressive capacity of the dominant eucalypts to resprout. However, empirical data to test this assumption are rare, limiting capacity to predict forest tolerance to emerging fire regimes including more frequent severe wildfires and extensive use of prescribed fire. We quantified tree mortality and regeneration in mixed-species eucalypt forests five years after an extensive wildfire that burnt under extreme fire weather. To examine combined site-level effects of wildfire and prescribed fire, our study included factorial replications of three wildfire severities, assessed as crown scorch and understorey consumption shortly after the wildfire (Unburnt, Low, High), and two times since last preceding fire (30 years since any fire). Our data indicate that while most trees survived low-severity wildfire through epicormic resprouting, this capacity was tested by high-severity wildfire. Five years after the wildfire, percentage mortalities of eucalypts in all size intervals from 10 to >70 cm diameter were significantly greater at High severity than Unburnt or Low severity sites, and included the near loss of the 10–20 cm cohort (93% mortality). Prolific seedling regeneration at High severity sites, and unreliable basal resprouting, indicated the importance of seedling recruitment to the resilience of these firetolerant forests. Recent prescribed fire had no clear effect on forest resistance (as tree survival) to wildfire, but decreased site-level resilience (as recruitment) by increasing mortalities of small stems. Our study indicates that high-severity wildfire has the potential to cause transitions to more open, simplified stand structures through increased tree mortality, including disproportionate losses in some size cohorts. Dependence on seedling recruitment could increase vulnerabilities to subsequent fires and future climates, potentially requiring direct management interventions to bolster forest resilience.Australian Governmen

Measurements of the Higgs boson production and decay rates and coupling strengths using pp collision data at √S=7 and 8 TeV in the ATLAS experiment

Combined analyses of the Higgs boson production and decay rates as well as its coupling strengths to vector bosons and fermions are presented. The combinations include the results of the analyses of the H -> gamma gamma, ZZ*, WW*, Z gamma, b (b) over bar, tau tau and mu mu decay modes, and the constraints on the associated production with a pair of top quarks and on the off-shell coupling strengths of the Higgs boson. The results are based on the LHC proton-proton collision datasets, with integrated luminosities of up to 4.7 fb(-1) at root s = 7 TeV and 20.3 fb(-1) at root s = 8 TeV, recorded by the ATLAS detector in 2011 and 2012. Combining all production modes and decay channels, the measured signal yield, normalised to the Standard Model expectation, is 1.18(-0.14)(+0.15). The observed Higgs boson production and decay rates are interpreted in a leading-order coupling framework, exploring a wide range of benchmark coupling models both with and without assumptions on the Higgs boson width and on the Standard Model particle content in loop processes. The data are found to be compatible with the Standard Model expectations for a Higgs boson at a mass of 125.36 GeV for all models considered

The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms−1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule

Assessing fire impacts on the carbon stability of fire-tolerant forests

17 Pág.The carbon stability of fire-tolerant forests is often assumed but less frequently assessed, limiting the potential to anticipate threats to forest carbon posed by predicted increases in forest fire activity. Assessing the carbon stability of fire-tolerant forests requires multi-indicator approaches that recognize the myriad ways that fires influence the carbon balance, including combustion, deposition of pyrogenic material, and tree death, post-fire decomposition, recruitment, and growth. Five years after a large-scale wildfire in southeastern Australia, we assessed the impacts of low- and high-severity wildfire, with and without prescribed fire (≤10 yr before), on carbon stocks in multiple pools, and on carbon stability indicators (carbon stock percentages in live trees and in small trees, and carbon stocks in char and fuels) in fire-tolerant eucalypt forests. Relative to unburned forest, high-severity wildfire decreased short-term (five-year) carbon stability by significantly decreasing live tree carbon stocks and percentage stocks in live standing trees (reflecting elevated tree mortality), by increasing the percentage of live tree carbon in small trees (those vulnerable to the next fire), and by potentially increasing the probability of another fire through increased elevated fine fuel loads. In contrast, low-severity wildfire enhanced carbon stability by having negligible effects on aboveground stocks and indicators, and by significantly increasing carbon stocks in char and, in particular, soils, indicating pyrogenic carbon accumulation. Overall, recent preceding prescribed fire did not markedly influence wildfire effects on short-term carbon stability at stand scales. Despite wide confidence intervals around mean stock differences, indicating uncertainty about the magnitude of fire effects in these natural forests, our assessment highlights the need for active management of carbon assets in fire-tolerant eucalypt forests under contemporary fire regimes. Decreased live tree carbon and increased reliance on younger cohorts for carbon recovery after high-severity wildfire could increase vulnerabilities to imminent fires, leading to decisions about interventions to maintain the productivity of some stands. Our multi-indicator assessment also highlights the importance of considering all carbon pools, particularly pyrogenic reservoirs like soils, when evaluating the potential for prescribed fire regimes to mitigate the carbon costs of wildfires in fire-prone landscapes.This work was supported the Australian Government's Biodiversity Fund (grant number LSP-943972-876), and by the Victorian Department of Environment, Land, Water and Planning through the Integrated Forest Ecosystem Research program. We thank Richard Loyn (formally of ARI) for leading the Biodiversity Fund application, members of the project's Steering committee for their guidance (Jaymie Norris, Gordon Friend, Steve Leonard, Tim O'Brien, and Peter Wilcock), and Adrian Kitchingman and Matt White for the initial desktop site selection. We also thank two anonymous reviewers for their positive contributions to the paper, and the following individuals for their diligent fieldwork: David Bryant, Benjamin Castro, Garry Cheers, Phoebe Macak, Jessica Millett-Riley, Julio César Nájera-Umaña, Brendan Nugent, Steve Sinclair, Geoff Suter, Arn Tolsma, Liz Wemyss.Peer reviewe

Response of Cool Season Turfs when Overseeded on a Putting Green with a History of Rapid Blight Disease

Rapid blight disease is a potentially devastating disease on cool season overseed turfs when irrigated with saline water. A two year test was conducted on a closely mowed Tifgreen bermudagrass turf which was infected with visual symptoms of necrotic patches of turf, and various degrees of blighting. The test included a broad representation of turf species for overseeding in an effort to (1) determine selected specie/cultivar susceptibility and disease expression to rapid blight in the field and (2) survey and assess the association of laboratory isolate detection from field sampling, with disease occurrence and severity of expression of field maintained overseed turf. Over a two year period, Rapid blight, caused by Labyrinthula terrestris was capable of infesting most cool season grasses in this test. In year one, Dawson CRF, SRX 555 slender creeping red fescue, and SR 105210 slender creeping red fescue showed no positive lab detection results from field plots. In year two (2003-2004), only SRX 555 SLQ had only 1 plot known to carry Labyrinthula throughout the main infestation season. In year two, essentially all turf plots showed some symptomology of disease expression. This was confirmed by lab identification. Tiller infection rates varied from 2% to 80% infection in the lab from field samples. The relationship between tiller infection rates and field plot disease expression was determined by Pearson’s product and Spearman Rank correlation coefficients. Field plot disease scores were correlated with percent tiller infection rates, R² = -0.56 plot basis, and R² = –0.71 treatment mean basis, respectively. Spearman Rank correlation coefficients were R² =; -0.62 on a plot basis, and R² =–0.78 based on treatment means Agreement between the disease condition (yes/no) vs. lab findings (positive/negative) occurred on 51 of 59 plot cases, and was significant compared to chance alone occurrences. Over two years, entries which had low disease scores included Fult’s alkali grass, Dawson creeping red fescue, SRX 555 SLQ slender creeping red fescue, SR 5210 slender creeping red fescue, and Providence creeping bentgrass. Over two years, entries which produced high field disease rating scores included SR 3100 Hard fescue, TransEze intermediate ryegrass, SR 4400 perennial ryegrass, SR 7200 velvet bentgrass, SR 7100 colonial bentgrass, Sabre and Laser Poa trivialis, and Redtop

Bennettetal2017_EcologicalApplications_CarboninFireTolerantEucForests.xlsx

Data relevant to figures in paper published in Ecological Applications (Bennett et al., 2017, Assessing fire impacts on the carbon stability of fire-tolerant forest

Structural diversity underpins carbon storage in Australian temperate forests

Forest carbon storage is the result of a multitude of interactions among biotic and abiotic factors. Our aim was to use an integrative approach to elucidate mechanistic relationships of carbon storage with biotic and abiotic factors in the natural forests of temperate Australia, a region that has been overlooked in global analyses of carbon-biodiversity relations.Department of Energy, Environment and Climate Action, Victoria, Australi