Prescribed burning consumes key forest structural components: implications for landscape heterogeneity.

Prescribed burning to achieve management objectives is a common practice in fire-prone regions worldwide. Structural components of habitat that are combustible and slow to develop are particularly susceptible to change associated with prescribed burning. We used an experimental, "whole-landscape" approach to investigate the effect of differing patterns of prescribed burning on key habitat components (logs, stumps, dead trees, litter cover, litter depth, and understorey vegetation). Twenty-two landscapes (each ~100 ha) were selected in a dry forest ecosystem in southeast Australia. Experimental burns were conducted in 16 landscapes (stratified by burn extent) while six served as untreated controls. We measured habitat components prior to and after burning. Landscape burn extent ranged from 22% to 89% across the 16 burn treatments. With the exception of dead standing trees (no change), all measures of habitat components declined as a consequence of burning. The degree of loss increased as the extent to which a landscape was burned also increased. Prescribed burning had complex effects on the spatial heterogeneity (beta diversity) of structural components within landscapes. Landscapes that were more heterogeneous pre-fire were homogenized by burning, while those that were more homogenous pre-fire tended to display greater differentiation post-burning. Thus, the notion that patch mosaic burning enhances heterogeneity at the landscape-scale depends on prior conditions. These findings have important management implications. Where prescribed burns must be undertaken, effects on important resources can be moderated via control of burn characteristics (e.g., burn extent). Longer-term impacts of prescribed burning will be strongly influenced by the return interval, given the slow rate at which some structural components accumulate (decades to centuries). Management of habitat structural components is important given the critical role they play in (1) provision of habitat resources for diverse organisms, (2) retention of moisture and nutrients in otherwise dry, low-productivity systems, and (3) carbon storage.

School-Age Test Proficiency and Special Education After Congenital Heart Disease Surgery in Infancy.

OBJECTIVE: To evaluate test proficiency and the receipt of special education services in school-age children who had undergone surgery for congenital heart disease (CHD) at age <1 year. STUDY DESIGN: Data from Arkansas-born children who underwent surgery for CHD at Arkansas Children's Hospital at age <1 year between 1996 and 2004 were linked to state birth certificates and the Arkansas Department of Education longitudinal database containing achievement test scores in literacy and mathematics for grades 3-4 and special education codes. The primary negative outcome was not achieving grade-level proficiency on achievement tests. Logistic regression accounting for repeated measures was used to evaluate for associations between achieving proficiency and demographic data, maternal education, and clinical factors. RESULTS: A total of 362 of 458 (79%) children who underwent surgery for CHD were matched to the Arkansas Department of Education database, 285 of whom had grade 3 and/or 4 achievement tests scores. Fewer students with CHD achieved proficiency in literacy and mathematics (P < .05) compared with grade-matched state students. Higher 5-minute Apgar score, shorter duration of hospitalization, and higher maternal education predicted proficiency in literacy (P < .05). White race, no cardiopulmonary bypass, and shorter hospitalization predicted proficiency in mathematics (P < .05). Sex, gestational age, age at surgery, CHD diagnosis, and type and number of surgeries did not predict test proficiency. Compared with all public school students, more children with CHD received special education services (26.9% vs 11.6%; P < .001). CONCLUSION: Children with CHD had poorer academic achievement and were more likely to receive special education services than all state students. Results from this study support the need for neurodevelopmental evaluations as standard practice in children with CHD.

Do multiple fires interact to affect vegetation structure in temperate eucalypt forests?

Fire plays an important role in structuring vegetation in fire-prone regions worldwide. Progress has been made towards documenting the effects of individual fire events and fire regimes on vegetation structure; less is known of how different fire history attributes (e.g., time since fire, fire frequency) interact to affect vegetation. Using the temperate eucalypt foothill forests of southeastern Australia as a case study system, we examine two hypotheses about such interactions: (1) post-fire vegetation succession (e.g., time-since-fire effects) is influenced by other fire regime attributes and (2) the severity of the most recent fire overrides the effect of preceding fires on vegetation structure. Empirical data on vegetation structure were collected from 540 sites distributed across central and eastern Victoria, Australia. Linear mixed models were used to examine these hypotheses and determine the relative influence of fire and environmental attributes on vegetation structure. Fire history measures, particularly time since fire, affected several vegetation attributes including ground and canopy strata; others such as low and sub-canopy vegetation were more strongly influenced by environmental characteristics like rainfall. There was little support for the hypothesis that post-fire succession is influenced by fire history attributes other than time since fire; only canopy regeneration was influenced by another variable (fire type, representing severity). Our capacity to detect an overriding effect of the severity of the most recent fire was limited by a consistently weak effect of preceding fires on vegetation structure. Overall, results suggest the primary way that fire affects vegetation structure in foothill forests is via attributes of the most recent fire, both its severity and time since its occurrence; other attributes of fire regimes (e.g., fire interval, frequency) have less influence. The strong effect of environmental drivers, such as rainfall and topography, on many structural features show that foothill forest vegetation is also influenced by factors outside human control. While fire is amenable to human management, results suggest that at broad scales, structural attributes of these forests are relatively resilient to the effects of current fire regimes. Nonetheless, the potential for more frequent severe fires at short intervals, associated with a changing climate and/or fire management, warrant further consideration.

Solubility trapping in formation water as dominant CO(2) sink in natural gas fields.

Injecting CO(2) into deep geological strata is proposed as a safe and economically favourable means of storing CO(2) captured from industrial point sources. It is difficult, however, to assess the long-term consequences of CO(2) flooding in the subsurface from decadal observations of existing disposal sites. Both the site design and long-term safety modelling critically depend on how and where CO(2) will be stored in the site over its lifetime. Within a geological storage site, the injected CO(2) can dissolve in solution or precipitate as carbonate minerals. Here we identify and quantify the principal mechanism of CO(2) fluid phase removal in nine natural gas fields in North America, China and Europe, using noble gas and carbon isotope tracers. The natural gas fields investigated in our study are dominated by a CO(2) phase and provide a natural analogue for assessing the geological storage of anthropogenic CO(2) over millennial timescales. We find that in seven gas fields with siliciclastic or carbonate-dominated reservoir lithologies, dissolution in formation water at a pH of 5-5.8 is the sole major sink for CO(2). In two fields with siliciclastic reservoir lithologies, some CO(2) loss through precipitation as carbonate minerals cannot be ruled out, but can account for a maximum of 18 per cent of the loss of emplaced CO(2). In view of our findings that geological mineral fixation is a minor CO(2) trapping mechanism in natural gas fields, we suggest that long-term anthropogenic CO(2) storage models in similar geological systems should focus on the potential mobility of CO(2) dissolved in water.

Academic proficiency in children after early congenital heart disease surgery.

Children with early surgery for congenital heart disease (CHD) are known to have impaired neurodevelopment; their performance on school-age achievement tests and their need for special education remains largely unexplored. The study aimed to determine predictors of academic achievement at school age and placement in special education services among early CHD surgery survivors. Children with CHD surgery at <1 year of age from January 1, 1998 to December 31, 2003, at the Arkansas Children's Hospital were identified. Out-of-state births and infants with known genetic and/or neurologic conditions were excluded. Infants were matched to an Arkansas Department of Education database containing standardized assessments at early school age and special-education codes. Predictors for achieving proficiency in literacy and mathematics and the receipt of special education were determined. Two hundred fifty-six children who attended Arkansas public schools and who had surgery as infants were included; 77.7 % had either school-age achievement-test scores or special-education codes of mental retardation or multiple disabilities. Scores on achievement tests for these children were 7-13 % lower than those of Arkansas students (p < 0.01). They had an eightfold increase in receipt of special education due to multiple disabilities [odds ratio (OR) 10.66, 95 % confidence interval (CI) 4.23-22.35] or mental retardation (OR 4.96, 95 % CI 2.6-8.64). Surgery after the neonatal period was associated with decreased literacy proficiency, and cardiopulmonary bypass during the first surgery was associated with decreased mathematics proficiency. Children who had early CHD surgery were less proficient on standardized school assessments, and many received special education. This is concerning because achievement-test scores at school age are "real-world" predictors of long-term outcomes.

Physiological response after translocation differs between source populations in a threatened mammal.

Conservation translocations are an important tool in the prevention of species loss, but the translocation process is associated with numerous stressors. Non-invasively monitoring stress physiology via faecal glucocorticoid metabolites (FGMs) can provide valuable insights into factors impacting translocation success and how to mitigate negative impacts. After validating an assay to measure FGMs in greater stick-nest rats (Leporillus conditor), we examined whether translocation caused a predictable change in physiology. We compared longer-term (one to five months post-translocation) physiological responses across three source populations (remnant-wild, reintroduced-wild, captive-bred), and investigated effects of body condition and sex on FGMs. Notably, FGMs of the remnant-wild population did not significantly change post-translocation, while the reintroduced-wild population exhibited a significant decrease and the captive-bred population a significant increase. Individuals in lower body condition had the highest FGMs in both wild-type populations, whereas the captive-bred population showed the opposite relationship. There was no difference in FGMs between the sexes. Our work highlights that physiological responses after translocation may not be uniform and source population history is an important factor to be considered, emphasizing the need for novel ideas that facilitate successful adaptation. By better understanding how species and individuals respond to translocation, we can improve translocation outcomes.

Seawater subduction controls the heavy noble gas composition of the mantle.

The relationship between solar volatiles and those now in the Earth's atmosphere and mantle reservoirs provides insight into the processes controlling the acquisition of volatiles during planetary accretion and their subsequent evolution. Whereas the light noble gases (helium and neon) in the Earth's mantle preserve a solar-like isotopic composition, heavy noble gases (argon, krypton and xenon) have an isotopic composition very similar to that of the modern atmosphere, with radiogenic and (in the case of xenon) solar contributions. Mantle noble gases in a magmatic CO2 natural gas field have been previously corrected for shallow atmosphere/groundwater and crustal additions. Here we analyse new data from this field and show that the elemental composition of non-radiogenic heavy noble gases in the mantle is remarkably similar to that of sea water. We challenge the popular concept of a noble gas 'subduction barrier'--the convecting mantle noble gas isotopic and elemental composition is explained by subduction of sediment and seawater-dominated pore fluids. This accounts for approximately 100% of the non-radiogenic argon and krypton and 80% of the xenon. Approximately 50% of the convecting mantle water concentration can then be explained by this mechanism. Enhanced recycling of subducted material to the mantle plume source region then accounts for the lower ratio of radiogenic to non-radiogenic heavy noble gas isotopes and higher water content of plume-derived basalts.

High temperature methane emissions from Large Igneous Provinces as contributors to late Permian mass extinctions.

Methane (CH4) emissions induced by Large Igneous Provinces have the potential to contribute to global environmental changes that triggered mass extinctions in Earth's history. Here, we explore the source of methane in gas samples from central Sichuan Basin, which is within the Emeishan Large Igneous Province (ELIP). We report evidence of high methane formation temperatures (between 249-17/+19 and 256-20/+22 °C) from clumped methane measurements and mantle-derived signatures of noble gases, which verify that oil-cracked CH4 and pyrobitumen are by-products within the reservoirs, associated with hydrothermal activity and enhanced heating by the ELIP. We estimate the volume of oil-cracked CH4 induced by the ELIP and argue that CH4 emissions would have been sufficient to initiate global warming prior to the end of the Permian. We also suggest that similar emissions from oil-cracked CH4 associated with the Siberian Traps Large Igneous Province may also have contributed to the end-Permian mass extinction significantly.

The effect of prescribed burning on plant rarity in a temperate forest.

Rare species can play important functional roles, but human-induced changes to disturbance regimes, such as fire, can inadvertently affect these species. We examined the influence of prescribed burns on the recruitment and diversity of plant species within a temperate forest in southeastern Australia, with a focus on species that were rare prior to burning. Floristic composition was compared among plots in landscapes before and after treatment with prescribed burns differing in the extent of area burnt and season of burn (before-after, control-impact design). Floristic surveys were conducted before burns, at the end of a decade of drought, and 3 years postburn. We quantified the effect of prescribed burns on species grouped by their frequency within the landscape before burning (common, less common, and rare) and their life-form attributes (woody perennials, perennial herbs or geophytes, and annual herbs). Burn treatment influenced the response of rare species. In spring-burn plots, the recruitment of rare annual herbs was promoted, differentiating this treatment from both autumn-burn and unburnt plots. In autumn-burn plots, richness of rare species increased across all life-form groups, although composition remained statistically similar to control plots. Richness of rare woody perennials increased in control plots. For all other life-form and frequency groups, the floristic composition of landscapes changed between survey years, but there was no effect of burn treatment, suggesting a likely effect of rainfall on species recruitment. A prescribed burn can increase the occurrence of rare species in a landscape, but burn characteristics can affect the promotion of different life-form groups and thus affect functional diversity. Drought-breaking rain likely had an overarching effect on floristic composition during our study, highlighting that weather can play a greater role in influencing recruitment and diversity in plant communities than a prescribed burn.

The impact of prematurity and maternal socioeconomic status and education level on achievement-test scores up to 8th grade.

BACKGROUND: The relative influence of prematurity vs. maternal social factors (socioeconomic status and education level) on academic performance has rarely been examined. OBJECTIVE: To examine the impact of prematurity and maternal social factors on academic performance from 3rd through 8th grade. METHODS: We conducted a retrospective cohort study of infants born in 1998 at the University of Arkansas for Medical Sciences. The study sample included 58 extremely low gestational age newborns (ELGANs, 23‒<28 weeks), 171 preterm (≥28‒<34 weeks), 228 late preterm (≥34‒<37 weeks), and 967 term ((≥37‒<42 weeks) infants. Neonatal and maternal variables were collected including maternal insurance status (proxy measure for socioeconomic status) and education level. The primary outcomes were literacy and mathematics achievement-test scores from 3rd through 8th grade. Linear mixed models were used to identify significant predictors of academic performance. All two-way interactions between grade level, gestational-age (GA) groups, and social factors were tested for statistical significance. RESULTS: Prematurity, social factors, gender, race, gravidity, and Apgar score at one minute were critical determinants of academic performance. Favorable social factors were associated with a significant increase in both literacy and mathematic scores, while prematurity was associated with a significant decrease in mathematic scores. Examination of GA categories and social factors interaction suggested that the impact of social factors on test scores was similar for all GA groups. Furthermore, the impact of social factors varied from grade to grade for literacy, while the influence of either GA groups or social factors was constant across grades for mathematics. For example, an ELGAN with favorable social factors had a predicted literacy score 104.1 (P <.001), 98.2 (P <.001), and 76.4 (P <.01) points higher than an otherwise similar disadvantaged term infant at grades 3, 5, and 8, respectively. The difference in their predicted mathematic scores was 33.4 points for all grades (P <.05). CONCLUSION: While there were significant deficits in academic performance for ELGANs compared to PT, LPT, and term infants, the deficit could be offset by higher SES and better-educated mothers. These favorable social factors were critical to a child's academic achievement. The role of socioeconomic factors should be incorporated in discussions on outcome with families of preterm infants.

What Determines Habitat Quality for a Declining Woodland Bird in a Fragmented Environment: The Grey-Crowned Babbler Pomatostomus temporalis in South-Eastern Australia?

Understanding what constitutes high quality habitat is crucial for the conservation of species, especially those threatened with extinction. Habitat quality frequently is inferred by comparing the attributes of sites where a species is present with those where it is absent. However, species presence may not always indicate high quality habitat. Demographic parameters are likely to provide a more biologically relevant measure of quality, including a species' ability to successfully reproduce. We examined factors believed to influence territory quality for the grey-crowned babbler (Pomatostomus temporalis), a cooperatively breeding woodland bird that has experienced major range contraction and population decline in south-eastern Australia. Across three broad regions, we identified active territories and determined the presence of fledglings and the size of family groups, as surrogates of territory quality. These measures were modelled in relation to habitat attributes within territories, the extent of surrounding wooded vegetation, isolation from neighbouring groups, and the size of the neighbourhood population. Fledgling presence was strongly positively associated with group size, indicating that helpers enhance breeding success. Surprisingly, no other territory or landscape-scale variables predicted territory quality, as inferred from either breeding success or group size. Relationships between group size and environmental variables may be obscured by longer-term dynamics in group size. Variation in biotic interactions, notably competition from the noisy miner (Manorina melanocephala), also may contribute. Conservation actions that enhance the number and size of family groups will contribute towards reversing declines of this species. Despite associated challenges, demographic studies have potential to identify mechanistic processes that underpin population performance; critical knowledge for effective conservation management.

Association Between Transient Newborn Hypoglycemia and Fourth-Grade Achievement Test Proficiency: A Population-Based Study.

IMPORTANCE: Prolonged neonatal hypoglycemia is associated with poor long-term neurocognitive function. However, little is known about an association between early transient newborn hypoglycemia and academic achievement. OBJECTIVE: To determine if early (within the first 3 hours of life) transient hypoglycemia (a single initial low glucose concentration, followed by a second value above a cutoff) is associated with subsequent poor academic performance. DESIGN, SETTING, AND PARTICIPANTS: A retrospective population-based cohort study of all infants born between January 1, 1998, and December 31, 1998, at the University of Arkansas for Medical Sciences who had at least 1 recorded glucose concentration (a universal newborn glucose screening policy was in effect) was conducted. Medical record data from newborns with normoglycemia or transient hypoglycemia were matched with their student achievement test scores in 2008 from the Arkansas Department of Education and anonymized. Logistic regression models were developed to evaluate the association between transient hypoglycemia and school-age achievement test proficiency based on perinatal factors. Common hypoglycemia cutoffs of a glucose level less than 35 mg/dL (primary) and less than 40 and 45 mg/dL (secondary) were investigated. All 1943 normoglycemic and transiently hypoglycemic infants (23-42 weeks' gestation) were eligible for inclusion in the study. Infants with prolonged hypoglycemia, congenital anomalies, or chromosomal abnormalities were excluded from the study. EXPOSURE: Hypoglycemia as a newborn. MAIN OUTCOMES AND MEASURES: The primary outcome was proficiency on fourth-grade literacy and mathematics achievement tests at age 10 years. We hypothesized a priori that newborns with early transient hypoglycemia would be less proficient on fourth-grade achievement tests compared with normoglycemic newborns. RESULTS: Perinatal data were matched with fourth-grade achievement test scores in 1395 newborn-student pairs (71.8%). Transient hypoglycemia (glucose level <35, <40, and <45 mg/dL) was observed in 6.4% (89 of 1395), 10.3% (143 of 1395), and 19.3% (269 of 1395) of newborns, respectively. After controlling for gestational age group, race, sex, multifetal gestation, insurance status, maternal educational level and socioeconomic status, and gravidity, transient hypoglycemia was associated with decreased probability of proficiency on literacy and mathematics fourth-grade achievement tests. For the 3 hypoglycemia cutoffs, the adjusted odds ratios (95% CIs) for literacy were 0.49 (0.28-0.83), 0.43 (0.28-0.67), and 0.62 (0.45-0.85), respectively, and the adjusted odds ratios (95% CIs) for mathematics were 0.49 (0.29-0.82), 0.51 (0.34-0.78), and 0.78 (0.57-1.08), respectively. CONCLUSIONS AND RELEVANCE: Early transient newborn hypoglycemia was associated with lower achievement test scores at age 10 years. Given that our findings are serious and contrary to expert opinion, the results need to be validated in other populations before universal newborn glucose screening should be adopted.

Activity patterns of free-ranging koalas (Phascolarctos cinereus) revealed by accelerometry.

An understanding of koala activity patterns is important for measuring the behavioral response of this species to environmental change, but to date has been limited by the logistical challenges of traditional field methodologies. We addressed this knowledge gap by using tri-axial accelerometer data loggers attached to VHF radio collars to examine activity patterns of adult male and female koalas in a high-density population at Cape Otway, Victoria, Australia. Data were obtained from 27 adult koalas over two 7-d periods during the breeding season: 12 in the early-breeding season in November 2010, and 15 in the late-breeding season in January 2011. Multiple 15 minute observation blocks on each animal were used for validation of activity patterns determined from the accelerometer data loggers. Accelerometry was effective in distinguishing between inactive (sleeping, resting) and active (grooming, feeding and moving) behaviors. Koalas were more active during the early-breeding season with a higher index of movement (overall dynamic body acceleration [ODBA]) for both males and females. Koalas showed a distinct temporal pattern of behavior, with most activity occurring from mid-afternoon to early morning. Accelerometry has potential for examining fine-scale behavior of a wide range of arboreal and terrestrial species.

Meteorite Kr in Earth's mantle suggests a late accretionary source for the atmosphere.

Noble gas isotopes are key tracers of both the origin of volatiles found within planets and the processes that control their eventual distribution between planetary interiors and atmospheres. Here, we report the discovery of primordial Kr in samples derived from Earth's mantle and show it to be consistent with a meteorite or fractionated solar nebula source. The high-precision Kr and Xe isotope data together suggest that Earth's interior acquired its volatiles from accretionary material similar to average carbonaceous chondrites and that the noble gases in Earth's atmosphere and oceans are dominantly derived from later volatile capture rather than impact degassing or outgassing of the solid Earth during its main accretionary stage.

What CO2 well gases tell us about the origin of noble gases in the mantle and their relationship to the atmosphere.

Study of commercially produced volcanic CO2 gas associated with the Colorado Plateau, USA, has revealed substantial new information about the noble gas isotopic composition and elemental abundance pattern of the mantle. Combined with published data from mid-ocean ridge basalts, it is now clear that the convecting mantle has a maximum (20)Ne/(22)Ne isotopic composition, indistinguishable from that attributed to solar wind-implanted (SWI) neon in meteorites. This is distinct from the higher (20)Ne/(22)Ne isotopic value expected for solar nebula gases. The non-radiogenic xenon isotopic composition of the well gases shows that 20 per cent of the mantle Xe is 'solar-like' in origin, but cannot resolve the small isotopic difference between the trapped meteorite 'Q'-component and solar Xe. The mantle primordial (20)Ne/(132)Xe is approximately 1400 and is comparable with the upper end of that observed in meteorites. Previous work using the terrestrial (129)I - (129)Xe mass balance demands that almost 99 per cent of the Xe (and therefore other noble gases) has been lost from the accreting solids and that Pu-I closure age models have shown this to have occurred in the first ca 100Ma of the Earth's history. The highest concentrations of Q-Xe and solar wind-implanted (SWI)-Ne measured in meteorites allow for this loss and these high-abundance samples have a Ne/Xe ratio range compatible with the 'recycled-air-corrected' terrestrial mantle. These observations do not support models in which the terrestrial mantle acquired its volatiles from the primary capture of solar nebula gases and, in turn, strongly suggest that the primary terrestrial atmosphere, before isotopic fractionation, is most probably derived from degassed trapped volatiles in accreting material.By contrast, the non-radiogenic argon, krypton and 80 per cent of the xenon in the convecting mantle have the same isotopic composition and elemental abundance pattern as that found in seawater with a small sedimentary Kr and Xe admix. These mantle heavy noble gases are dominated by recycling of air dissolved in seawater back into the mantle. Numerical simulations suggest that plumes sampling the core-mantle boundary would be enriched in seawater-derived noble gases compared with the convecting mantle, and therefore have substantially lower (40)Ar/(36)Ar. This is compatible with observation. The subduction process is not a complete barrier to volatile return to the mantle.

Heightened tropical cyclone activity in the North Atlantic: natural variability or climate trend?

We find that long-period variations in tropical cyclone and hurricane frequency over the past century in the North Atlantic Ocean have occurred as three relatively stable regimes separated by sharp transitions. Each regime has seen 50% more cyclones and hurricanes than the previous regime and is associated with a distinct range of sea surface temperatures (SSTs) in the eastern Atlantic Ocean. Overall, there appears to have been a substantial 100-year trend leading to related increases of over 0.7 degrees C in SST and over 100% in tropical cyclone and hurricane numbers. It is concluded that the overall trend in SSTs, and tropical cyclone and hurricane numbers is substantially influenced by greenhouse warming. Superimposed on the evolving tropical cyclone and hurricane climatology is a completely independent oscillation manifested in the proportions of tropical cyclones that become major and minor hurricanes. This characteristic has no distinguishable net trend and appears to be associated with concomitant variations in the proportion of equatorial and higher latitude hurricane developments, perhaps arising from internal oscillations of the climate system. The period of enhanced major hurricane activity during 1945-1964 is consistent with a peak period in major hurricane proportions.

Extinct 244Pu in ancient zircons.

We have found evidence, in the form of fissiogenic xenon isotopes, for in situ decay of 244Pu in individual 4.1- to 4.2-billion-year-old zircons from the Jack Hills region of Western Australia. Because of its short half-life, 82 million years, 244Pu was extinct within 600 million years of Earth's formation. Detrital zircons are the only known relics to have survived from this period, and a study of their Pu geochemistry will allow us to date ancient metamorphic events and determine the terrestrial Pu/U ratio for comparison with the solar ratio.