Subsequent Disturbance Research Articles

A matter of time: self-regulated tree regeneration in a natural Norway spruce (Picea abies) forest at Mt. Brocken, Germany

European natural mountain Norway spruce (Picea abies) forests are currently subject to extensive disturbances. An improved understanding of the self-regulated regenerative capacity of this forest type is therefore needed. We used the last remnant of natural mountain Norway spruce forests in central northwestern Europe (BNF Brocken natural forest), to analyze (1) the diversity of structure and age distribution of the tree population and (2) the effect of disturbances on self-regulated tree regeneration over the last 264 years. To this end, we combined an assessment of stand structure with dendrochronological investigations and a review of disturbance history. We hypothesized that BNF exhibits a high diversity of tree ages and dimensions and that recruitment and survival of tree regeneration were largely independent from disturbances. BNF showed a high structural and age diversity. Disturbances exhibited no regular temporal pattern. Their effect on tree regeneration was rather complex and changed with observation period. Impeding and facilitating effects of past disturbances on recruitment were significant from 1736 to 1910. From 1911 until 2000, recruitment decoupled from preceding disturbances. Subsequent disturbances facilitated survival of established trees from 1736 to 1820, while afterward no significant influence could be proved. Our study showed that in the course of self-regulated development the tree population of BNF has gradually acquired, or maintained, a diverse structure. Disturbances served as an important driver of diversification. We concluded that increasing deadwood availability and limiting browsing are the key to securing immediate regeneration.

A review and classification of interactions between forest disturbance from wind and fire

Abstract Current research on interactions between ecological disturbances emphasizes the potential for greatly enhanced ecological effects that may occur when disturbances interact. Much less attention has focused on the possibility of disturbance interactions that buffer ecological change. In this review, we discuss and classify evidence for interactions between two forest disturbances common in eastern North America—wind damage and fire—focusing on studies where forest wind damage precedes fire. Interaction mechanisms are classified according to how they influence ecosystem resistance to and resilience from subsequent disturbances and whether interactions have synergistic or antagonistic effects. Several important generalizations emerge from this synthesis of disturbance interactions. First, buffering interactions between wind damage and fire may be more important when fire intensity is low. Second, wind–fire interactions related to changes in fuel may vary with climatic conditions, with regional differences, and with intensity or severity of individual disturbances. Third, both amplifying and buffering effects may co-occur in a spatial mosaic through a variety of interaction mechanisms. In this respect, the concept of ecosystem response to multiple disturbances parallels that of classical models of successional pathways. It is useful to conceptualize ecosystem response to compounded disturbances as a diverse collection of individual, co-occurring mechanisms of interaction rather than considering multiple disturbances to be wholly amplifying or wholly buffering. Future studies on wind–fire disturbances that explicitly examine mechanisms of interactions and the factors that govern them will aid in understanding these ecologically important and ubiquitous forest disturbances.

Strike-slip tectonics during the Neoproterozoic–Cambrian assembly of East Gondwana: Evidence from a newly discovered microcontinent in the Indian Ocean (Batavia Knoll)

The first dredge samples recovered from the Batavia Knoll in the eastern Indian Ocean demonstrate it is a rifted continental fragment that now lies submerged in 2km of water between the Perth Abyssal Plain and Wharton Basin, ~1600km offshore Western Australia. This knoll is the second microcontinent to have been discovered in this region, lying ~180km to the NE of Gulden Draak Knoll; both knolls rifted from the Indian margin at c. 104–101Ma during the breakup of East Gondwana. Dredged rocks include granite, granodiorite, charnockite and quartz-rich pegmatite, preserving igneous microstructure and biotite-schlieren. The composite nature of many samples suggests derivation from a felsic igneous complex. This basement is at least partly covered by Late Cretaceous sedimentary strata. Zircon grains from five representative granitoid samples primarily display modified oscillatory zoning and U-Pb data that spread along concordia over ~50–70m.y., suggesting protracted magmatism and Pb-loss during the latest Neoproterozoic–early Cambrian (c. 580–530Ma). Despite the span in U-Pb zircon ages, the primary igneous populations exhibit a relatively narrow range of initial Hf isotopic ratios (Hfi=0.281290–0.281814; εHfi=−41.40 to −23.32). This evolved nature of the Hf signature suggests derivation of melts from ancient crust (TDM2=4.05–2.92Ga) with very limited juvenile input. Plate models based on sparse paleomagnetic data imply significant relative motion between India and Australia during the late Neoproterozoic–Cambrian. We suggest the new isotopic data from the Batavia Knoll granitic rocks, coupled with other regional geological constraints, are consistent with magmatic intrusion and subsequent disturbance of U-Pb systems along a late Neoproterozoic–Cambrian sinistral strike-slip margin related to Gondwana assembly.

Fire Reduces Fungal Species Richness and In Situ Mycorrhizal Colonization: A Meta-Analysis

Soil fungal communities perform many functions that help plants meet their nutritional demands. However, overall trends for fungal response to fire, which can be especially critical in a post-fire context, have been difficult to elucidate. We used meta-analytical techniques to investigate fungal response to fire across studies, ecosystems, and fire types. Change in fungal species richness and mycorrhizal colonization were used as the effect size metrics in random effects models. When different types of methods for assessing fungal species richness and mycorrhizal colonization were considered together, there was an average reduction of 28 % in fungal species richness post fire, but no significant response in mycorrhizal colonization. In contrast, there was a 41 % reduction in fungal species richness post fire when assessed by sporocarp surveys, but fungal species richness was not significantly affected when assessed by molecular methods. Measured in situ, fire reduced mycorrhizal colonization by 21 %, yet no significant response occurred when assessed by ex situ bioassays. These findings suggest that the putative magnitude of fire effects on soil fungal communities may be dependent on the approach and assessment method used. Furthermore, biome, but not fire type (i.e., wildfire versus prescribed fire) was a significant moderator of our categorical models, suggesting that biome might be a more useful predictor of fungal species richness response to fire than fire type. Reductions in fungal species richness and in situ mycorrhizal colonization post fire declined logarithmically and approached zero (i.e., no effect) at 22 and 11 years, respectively. We concluded that fire reduces fungal species richness and in situ mycorrhizal colonization, but if conditions allow communities to recover (e.g., without subsequent disturbance, favorable growing conditions), soil fungi are resilient on decadal time scales; the resiliency of soil fungi likely contributes to the overall rapid ecosystem recovery following fire.

Simulation of Surface Instability at the Interface of Two Fluids

In this theoretical and numerical study, the physical mechanisms leading to the production of surface waves generated at the interface of two fluids (liquid/gas or liquid/liquid) are investigated. Particular attention is devoted to the Kelvin-Helmholtz (KH) type instability, which appears in the area of high shear located at the fluid-fluid interface. The subsequent disturbances in velocity and pressure associated with the wave motion are assumed to be 2D and sufficiently small to justify the linearization of the equations of the motion. The Navier-Stokes (NS), Orr-Sommerfeld (OS) and KH equations are the primary ones used to investigate of surface instability. During the study, the main characteristics of a surface instability such as wavelength, wave number, frequency, amplitude, wave speed and growth rate are investigated according to fluid viscosity. The effect of gravity is investigated by 2D simulations without these external forces or with them in one of the following configurations:

Dizziness, Unsteadiness, Visual Disturbances, and Sensorimotor Control in Traumatic Neck Pain.

Synopsis There is considerable evidence to support the importance of cervical afferent dysfunction in the development of dizziness, unsteadiness, visual disturbances, altered balance, and altered eye and head movement control following neck trauma, especially in those with persistent symptoms. However, there are other possible causes for these symptoms, and secondary adaptive changes should also be considered in differential diagnosis. Understanding the nature of these symptoms and differential diagnosis of their potential origin is important for rehabilitation. In addition to symptoms, the evaluation of potential impairments (altered cervical joint position and movement sense, static and dynamic balance, and ocular mobility and coordination) should become an essential part of the routine assessment of those with traumatic neck pain, including those with concomitant injuries such as concussion and vestibular or visual pathology or deficits. Once adequately assessed, appropriate tailored management should be implemented. Research to further assist differential diagnosis and to understand the most important contributing factors associated with abnormal cervical afferent input and subsequent disturbances to the sensorimotor control system, as well as the most efficacious management of such symptoms and impairments, is important for the future. J Orthop Sports Phys Ther 2017;47(7):492-502. Epub 16 Jun 2017. doi:10.2519/jospt.2017.7052.

Targeting human telomerase RNA component using antisense oligonucleotide induces rapid cell death and increases ATO-induced apoptosis in APL cells

The impressive advances carried out in designing pharmacological strategies with the aim of telomerase inhibition in cancers emerged a consensus that telomerase-targeted therapies could be exciting prospect in repertoire of future cancer strategies. The results of the present study indicated that targeting telomerase using an oligonucleotide-based molecule against human telomerase RNA template (hTR ASODN) reduced the survival rate of NB4 cells and induced a caspase-3-dependent apoptosis. Our finding was even noticeable in the synergistic experiments, where we found an enhanced reduction in the viability of the cells after short-term treatment with ATO in combination with the inhibitor. The resulting data delineated that short-term treatment of the cells with hTR ASODN either as single agent or in combination with ATO resulted in apoptotic cell death through activation of DNA damage response via up-regulation of p73 and ATM coupled with down-regulation of c-Myc. Moreover, we found that induction of p21 and subsequent disturbance of the death promoter to death repressor genes may contribute to the enhanced growth suppressive effect of the drugs combination. Overall, our findings support the idea that telomerase activity may have pivotal role in attenuating ATO effectiveness and combination of ATO with telomerase inhibitor seems to be a novel promising strategy, which may increase APL cure rates.

Post-Hurricane Successional Dynamics in Abundance and Diversity of Canopy Arthropods in a Tropical Rainforest.

We quantified long-term successional trajectories of canopy arthropods on six tree species in a tropical rainforest ecosystem in the Luquillo Mountains of Puerto Rico that experienced repeated hurricane-induced disturbances during the 19-yr study (1991-2009). We expected: 1) differential performances of arthropod species to result in taxon- or guild-specific responses; 2) differences in initial conditions to result in distinct successional responses to each hurricane; and 3) the legacy of hurricane-created gaps to persist despite subsequent disturbances. At least one significant effect of gap, time after hurricane, or their interaction occurred for 53 of 116 analyses of taxon abundance, 31 of 84 analyses of guild abundance, and 21 of 60 analyses of biodiversity (e.g., richness, evenness, dominance, and rarity). Significant responses were ∼60% more common for time after hurricane than for gap creation, indicating that temporal changes in habitat during recovery were of primary importance. Both increases and decreases in abundance or diversity occurred in response to each factor. Guild-level responses were probably driven by changes in the abundance of resources on which they rely. For example, detritivores were most abundant soon after hurricanes when litter resources were elevated, whereas sap-suckers were most abundant in gaps where new foliage growth was the greatest. The legacy of canopy gaps created by Hurricane Hugo persisted for at least 19 yr, despite droughts and other hurricanes of various intensities that caused forest damage. This reinforces the need to consider historical legacies when seeking to understand responses to disturbance.

Impacts of climate variability on tree demography in second growth tropical forests: the importance of regional context for predicting successional trajectories

AbstractNaturally regenerating and restored second growth forests account for over 70% of tropical forest cover and provide key ecosystem services. Understanding climate change impacts on successional trajectories of these ecosystems is critical for developing effective large‐scale forest landscape restoration (FLR) programs. Differences in environmental conditions, species composition, dynamics, and landscape context from old growth forests may exacerbate climate impacts on second growth stands. We compile data from 112 studies on the effects of natural climate variability, including warming, droughts, fires, and cyclonic storms, on demography and dynamics of second growth forest trees and identify variation in forest responses across biomes, regions, and landscapes. Across studies, drought decreases tree growth, survival, and recruitment, particularly during early succession, but the effects of temperature remain unexplored. Shifts in the frequency and severity of disturbance alter successional trajectories and increase the extent of second growth forests. Vulnerability to climate extremes is generally inversely related to long‐term exposure, which varies with historical climate and biogeography. The majority of studies, however, have been conducted in the Neotropics hindering generalization. Effects of fire and cyclonic storms often lead to positive feedbacks, increasing vulnerability to climate extremes and subsequent disturbance. Fragmentation increases forests’ vulnerability to fires, wind, and drought, while land use and other human activities influence the frequency and intensity of fire, potentially retarding succession. Comparative studies of climate effects on tropical forest succession across biogeographic regions are required to forecast the response of tropical forest landscapes to future climates and to implement effective FLR policies and programs in these landscapes.

Embryonic forebrain transcriptome of mice with polyalanine expansion mutations in theARXhomeobox gene

The Aristaless-related homeobox (ARX) gene encodes a paired-type homeodomain transcription factor with critical roles in embryonic development. Mutations in ARX give rise to intellectual disability (ID), epilepsy and brain malformation syndromes. To capture the genetics and molecular disruptions that underpin the ARX-associated clinical phenotypes, we undertook a transcriptome wide RNASeq approach to analyse developing (12.5 dpc) telencephalon of mice modelling two recurrent polyalanine expansion mutations with different phenotypic severities in the ARX gene. Here we report 238 genes significantly deregulated (Log2FC > +/-1.1, P-value <0.05) when both mutations are compared to wild-type (WT) animals. When each mutation is considered separately, a greater number of genes were deregulated in the severe PA1 mice (825) than in the PA2 animals (78). Analysing genes deregulated in either or both mutant strains, we identified 12% as implicated in ID, epilepsy and autism (99/858), with ∼5% of them as putative or known direct targets of ARX transcriptional regulation. We propose a core pathway of transcription regulators, including Hdac4, involved in chromatin condensation and transcriptional repression, and one of its targets, the transcription factor Twist1, as potential drivers of the ID and infantile spasms in patients with ARX polyalanine expansion mutations. We predict that the subsequent disturbance to this pathway is a consequence of ARX protein reduction with a broader and more significant level of disruption in the PA1 in comparison to the PA2 mice. Identifying early triggers of ARX-associated phenotypes contributes to our understanding of particular clusters/pathways underpinning comorbid phenotypes that are shared by many neurodevelopmental disorders.

The relative importance of tree and stand properties in susceptibility to spruce beetle outbreak in the mid‐20th century

AbstractTree susceptibility to potentially lethal agents is determined not only by attributes of individual trees, but also by neighborhood effects at a range of scales. For example, effects of disturbances on individual trees are often contingent on the size, configuration, and other properties of neighboring trees. Wildfires can modify postfire properties of individual trees as well as of entire forest stands, both of which can affect subsequent ecological processes, including subsequent disturbances. In recent years, much has been learned about how disturbances interact, but numerous questions concerning underlying mechanisms remain unresolved. For example, the relative importance of forest properties at different spatial scales in determining how fires affect forest susceptibility to subsequent disturbances is not well understood. This study explicitly compares the relative importance of tree vs. fine‐scale neighborhood effects (e.g., stand properties at &lt;7 m radii), on susceptibility to a 1940s' spruce beetle outbreak. Attributes of individual trees and of stand structure were spatially reconstructed at five 250‐m2 sites that were partly burned in the late 19th century and then affected by spruce beetle outbreak in the 1940s. Random Forest models and classification trees were used to compare the relative importance of variables for susceptibility to spruce beetle attack. Individual tree properties (diameter at breast height and age) were the most important predictors of susceptibility to the outbreak across all sites combined and at each of the sites individually. In contrast, neighborhood effects were poor predictors of susceptibility. This study suggests wildfires reduce susceptibility to outbreaks primarily by reducing the size of postfire live trees and only secondarily by modifying stand structure. One implication of this is that management strategies that aim to modify stand structure over large areas in order to reduce susceptibility to spruce beetle outbreaks may be unnecessarily intensive.

An Under-Frequency Load Shedding Scheme Design for a Large Steelworks with Self-Generation System

This paper presents a load-shedding scheme for a large steelworks with several self-generation units. The power system of the steelworks can be separated from a utility grid in case of disturbances. Also, some substations with generators in the steelworks can be isolated due to the tie line tripping. These situations cause an under-frequency events as the result of the imbalance between generation and load. A system stabilizing controller (SSC) system is the core of the proposed load shedding scheme for the frequency stabilization. The SSC system performs a pre-calculation for load-shedding (LS) quantity before an event and a post-calculation to provide against a deficient load-shedding in the pre-calculated load-shedding. The back-up protection system is used to counteract situations in which the SSC system does not operate normally. Also, the load-shedding by frequency calculation is carried out for subsequent disturbance such as an additional generator tripping. The hardware based proposed scheme has been applied to the steelworks. The several under-frequency events causing a load-shedding are examined through the transient stability analysis by using ETAP. The simulation results show that the proposed scheme effectively stabilizes the frequency within the continuous frequency operation range of generators.

Comparative Study on Lipid Profile of Hypertensive Patients and Non-hypertensive Individuals in Bikaner, Rajasthan, India

Cardiovascular diseases are the highest cause of death in the industrialized world, and many of these deaths may be work related. Hypertension is the most common of the cardio-vascular diseases which is the leading cause of morbidity and mortality in the industrial world. Stress, tension, smoking, liquors, insufficient rest, metabolic disorders, excessive consumption of tea or coffee, emotional disturbance etc. are also associated with high blood pressure. Several previous studies showed the relation between hyperlipidemia and hypertension. An excessive daily intake of saturated fats, cholesterol, and other sources of calories and subsequent disturbance of lipid profile leading to hypertriglyceridemia and hypercholesterolemia are associated with obesity and, consequently, hypertension. The present study was designed to compare the serum triglyceride, cholesterol, High Density Lipo-protein (HDL) and Low Density Lipo-protein (LDL levels in hypertensive and non-hypertensive individuals. While the relation between hyperlipidemia and hypertension is clearly shown, there are only a few studies which have compared the lipid profiles of hypertensive and non-hypertensive cases. The aim and objectives of the present case-control study were to find out the relationship between serum lipids levels of the hypertensive patients with controls in Bikaner, Rajasthan, India. This study was conducted in the Department of Physiology, Sardar Patel Medical College, Bikaner and Department of General Medicine, Kothari Medical and Research Institute, Bikaner. Patients were selected randomly from the city, and the selected subjects were divided into two groups each comprising of 50 patients. Group I: untreated hypertension and served as study group; Group II: normotensive persons having normal Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (BP) and served as a control group. Patients included in both the groups were assessed for lipid profile. Overall, it could be concluded that the serum lipid profile of recently diagnosed untreated hypertensive patient was deranged specially in a middle age group (the study group) as compared to healthy subjects. Based on the results obtained from the present study, it could be further envisaged that serum cholesterol; triglyceride levels are positively correlated with hypertensive patients whereas HDL-cholesterol has no significant changes with hypertension.

Fire Severity Controlled Susceptibility to a 1940s Spruce Beetle Outbreak in Colorado, USA.

The frequency, magnitude, and size of forest disturbances are increasing globally. Much recent research has focused on how the occurrence of one disturbance may affect susceptibility to subsequent disturbances. While much has been learned about such linked disturbances, the strength of the interactions is likely to be contingent on the severity of disturbances as well as climatic conditions, both of which can affect disturbance intensity and tree resistance to disturbances. Subalpine forests in western Colorado were affected by extensive and severe wildfires in the late 19th century and an extensive and severe outbreak of spruce beetle (Dendroctonus rufipennis) in the 1940s. Previous research found that most, but not all, of the stands that burned and established following the late 19th century fires were not susceptible to the 1940s outbreak as beetles preferentially attack larger trees and stands in advanced stages of development. However, previous research also left open the possibility that some stands that burned and established following the 19th century fires may have been attacked during the 1940s outbreak. Understanding how strongly stand structure, as shaped by disturbances of varying severity, affected susceptibility to past outbreaks is important to provide a baseline for assessing the degree to which recent climate change may be relaxing the preferences of beetles for larger trees and for stands in latter stages of structural development and thereby changing the nature of linked disturbances. Here, dendroecological methods were used to study disturbance history and tree age of stands in the White River National Forest in Western Colorado that were identified in historical documents or remotely-sensed images as having burned in the 19th century and having been attacked by spruce beetle in the 1940s. Dendroecological reconstructions indicate that in young post-fire stands only old remnant trees that survived the otherwise stand-replacing fires were killed in the 1940s outbreak. No young post-fire trees (< ca. 128 years) were susceptible to the 1940s outbreak, implying that under the relatively cool and wet conditions of the mid-20th century, susceptibility to and spatial patterns of spruce beetle outbreak were most likely controlled by variations in severity of prior disturbance by fire. This study provides a baseline for comparing linked disturbances under the relatively warmer and drier conditions of recent (e.g. post-1990) outbreaks in order to assess how climate mitigates the degree to which pre-disturbance history and structure affect susceptibility to disturbances.

Optimal forest management with sequential disturbances

Previous work in forest management under uncertainty has been based on the assumption that landowners face a risk of only one damaging event during any forest rotation, with the main result being that landowners choose shorter rotation ages. These models are universal in an assumption that, should the disturbance arise in a given rotation, the landowner salvages what is possible through a harvest and replants to begin a new rotation. However, a real possibility exists that multiple disturbances may occur in one rotation, with the landowner retaining the damaged stand thereby waiting through the first or even a subsequent disturbance to harvest and begin a new rotation. We develop a new approach for rotations models and choices that allows more than one event and flexibility in the timing of harvest, where tree recovery and damage may make continuance of the rotation, rather than starting over, a rent maximizing strategy. We thereby generalize the highly-cited body of literature based on Paul Samuelson's and William Reed's seminal contributions. Results demonstrate that failure to consider these new features leads to suboptimal harvest decisions and highly suboptimal land rent values. Important parameters are found to be arrival rates of future disturbances and survival proportions and growth rates after each disturbance.

‘It’s silly these doors don’t open’: a six-year-old girl emerges from a chronic state of emotional withdrawal

This clinical paper explores the way in which the first two years of a long-term psychotherapy helped six-year-old Anna to lessen her retreat into a chronic withdrawn emotional state. Over the course of the first year she would occasionally pick up the fridge from the doll’s house and try to open the doors, but because the fridge was actually a block of wood the doors could not open. In treatment, this inquiry came to represent the difficulties of engaging and making contact with a baby who found it very hard to feed. The author describes how, as Anna entered into a therapeutic relationship, it slowly became clear that there was an inner world jam-packed with persecutory anxieties and a family history of unmourned loss and trauma. Through fear Anna slammed the doors to her mind – to knowing herself – and by not feeding, Anna starved herself of opportunities for mental growth. It took some time for her to state, “it’s silly these doors don’t open, they should”. In the discussion of this clinical material the author draws on the work of Francis Tustin, Alessandra Piontelli and Marguerite Reid to consider the link between intergenerational and prenatal trauma and subsequent emotional disturbance in the child.

Prefire grazing by cattle increases postfire resistance to exotic annual grass (Bromus tectorum) invasion and dominance for decades.

Fire, herbivory and their interaction influence plant community dynamics. However, little is known about the influence of prefire herbivory on postfire plant community response, particularly long‐term resistance to postfire exotic plant invasion in areas that historically experienced limited large herbivore pressure and infrequent, periodic fires.We investigated the long‐term postfire effects of prefire herbivory by cattle, an exotic herbivore, in Artemisia (sagebrush) plant communities in the northern Great Basin, USA. Study areas were moderately grazed or not grazed by cattle since 1936 and then were burned in 1993. Plant community response was measured the 19th through the 22nd year postfire. Prior to burning exotic annual grass presence was minimal (<0.5% foliar cover) and plant community characteristics were similar between grazed and ungrazed treatments, with the exception of litter biomass being two times greater in the ungrazed treatment.Two decades postfire, Bromus tectorum L., an exotic annual grass, dominated the ungrazed treatment. Native bunchgrasses, species richness, and soil biological crusts were greater in prefire grazed areas compared to ungrazed areas.These results suggest that moderate prefire herbivory by cattle increased the resistance of the plant community to postfire invasion and dominance by B. tectorum. We presume that herbivory reduced mortality of large perennial bunchgrasses during the fire by reducing fine fuel (litter) and subsequently burn temperatures. Synthesis: This research demonstrates that a moderate disturbance (herbivory) may mediate the effects of a subsequent disturbance (fire). The effects of disturbances are not independent; therefore quantifying these interactions is critical to preventing oversimplification of complex plant community dynamics and guiding the conservation of endangered ecosystems.

Contingent resistance in longleaf pine (Pinus palustris) growth and defense 10 years following smoldering fires

In many fire-prone woodlands and forests, fire exclusion has resulted in substantial litter and duff accumulations capable of long-duration smoldering once fire is reintroduced. While previous research has shown that the soil heating from smoldering fires resulted in short-term reductions in coarse root non-structural carbohydrates and latewood growth, information on the long-term effects of smoldering fire is lacking. Our study compared the effects of three smoldering fire treatments (root only, stem only, root and stem) and two control treatments (no fire and surface fire only) on longleaf pine (Pinus palustris) growth and defense ten years after treatments. We cored 17–29 similar sized trees per treatment and measured growth as basal area increment and defense as resin duct properties (e.g., resin duct size, % resin duct area). We used generalized linear mixed models to determine the influence of smoldering treatments and climate on basal area increment and resin duct properties. Variation in basal area increment and resin duct size during the previous ten years were positively correlated with the subsequent ten years, r2=0.71 and r2=0.65, respectively. Additionally, temporal variation in growth and defense were related to climatic factors. Growth had the strongest correlation with current August temperatures (r=−0.50), and defense had the strongest correlation with current December temperatures (r=−0.64). Basal area increment was best predicted by summer and fall Palmer Drought Severity Index, while resin duct size was best predicted by the interaction of treatment and precipitation during the previous November. During the three driest years following treatment smoldering duration had a negative relationship with basal area increment (p<0.0085; r2=0.08) and resin duct size (p<0.0003; r2=0.16). While longleaf pine growth was generally resistant to long-duration soil heating following years of fire exclusion, the proceeding growth response was contingent on the post-fire climate. Longleaf pine resin duct size was sensitive to the effects of smoldering fire, and potential negative impacts may be exacerbated by lower precipitation. Restoring fire to long-unburned sites proceeded by warmer and drier climate conditions may result in reduced longleaf pine growth and defense that may contribute to increased probability of mortality during subsequent disturbances.

Fire severity alters spatio–temporal movements and habitat utilisation by an arboreal marsupial, the mountain brushtail possum (Trichosurus cunninghami)

Understanding how severe wildfires influence faunal movement is essential for predicting how changes in fire regimes will affect ecosystems. We examined the effects of fire severity distribution on spatial and temporal variation in movement of an Australian arboreal mammal, the mountain brushtail possum (Trichosurus cunninghami). We used GPS telemetry to characterise the movements of 18 possums in landscapes burnt to differing extents by a large wildfire. We identified a temporal change in movement patterns in response to fire. In unburnt landscapes, individuals moved greater distances early and late in the night and had less overlap in the areas used for foraging and denning, than in high-severity burnt landscapes. Habitat selection was dependent on the spatial context of fire in the surrounding landscape. Forest recently burnt at high severity may provide suitable habitat for species such as the mountain brushtail possum, if protected from subsequent disturbance, such as salvage logging. However, spatial and temporal patterns of habitat use and selection differ considerably between burnt and undisturbed landscapes. The spatial outcomes of ecological disturbances such as wildfires have the potential to alter the behaviour and functional roles of fauna across large areas.

Low visual cortex GABA levels in hepatic encephalopathy: links to blood ammonia, critical flicker frequency, and brain osmolytes

The pathogenesis of hepatic encephalopathy (HE) is not fully understood yet. Hyperammonemia due to liver failure and subsequent disturbance of cerebral osmolytic balance is thought to play a pivotal role in the emergence of HE. The aim of this in-vivo MR spectroscopy study was to investigate the levels of γ-aminobutyric acid (GABA) and its correlations with clinical symptoms of HE, blood ammonia, critical flicker frequency, and osmolytic levels. Thirty patients with minimal HE or HE1 and 16 age-matched healthy controls underwent graduation of HE according to the West-Haven criteria and including the critical flicker frequency (CFF), neuropsychometric testing and blood testing. Edited proton magnetic resonance spectroscopy ((1)H MRS) was used to non-invasively measure the concentrations of GABA, glutamate (Glu), glutamine (Gln), and myo-inositol (mI) - all normalized to creatine (Cr) - in visual and sensorimotor cortex. GABA/Cr in the visual area was significantly decreased in mHE and HE1 patients and correlated both to the CFF (r = 0.401, P = 0.013) and blood ammonia levels (r = -0.434, P = 0.006). Visual GABA/Cr was also strongly linked to mI/Cr (r = 0.720, P < 0.001) and Gln/Cr (r = -0.699, P < 0.001). No group differences or correlations were found for GABA/Cr in the sensorimotor area. Hepatic encephalopathy is associated with a regional specific decrease of GABA levels in the visual cortex, while no changes were revealed for the sensorimotor cortex. Correlations of visual GABA/Cr with CFF, blood ammonia, and osmolytic regulators mI and Gln indicate that decreased visual GABA levels might contribute to HE symptoms, most likely as a consequence of hyperammonemia.