The use of mineral magnetism in the reconstruction of fire history: a case study from Lago di Origlio, Swiss Alps

The use of magnetic measurements in the detection of fire signals has been neglected since the work of Rummery et al., (1979), yet considerable developments have been made in the interpretation of magnetic measurements over the last 16 years. This paper presents a study of the fire history of Lago di Origlio in the southern Swiss Alps. The study utilises the technique of mineral magnetism alongside the stratigraphic pollen, spore and charcoal records. Correlation between the various proxy records indicates that a magnetic ‘fire’ record is present within the sediments for the last 4 ka. The magnetic fire record has a distinct mineralogical and magnetic grain size signature that can be recognised against the background sedimentary signal. The results suggest that magnetic measurements may be usefully employed in the reconstruction of fire history. Their application is rapid and non-destructive and the results may provide additional information in relation to the links between catchment fire events and the sedimentary record.

Fire in ice: two millennia of boreal forest fire history from the Greenland NEEM ice core

Biomass burning is a major source of greenhouse gases and influences regional to global climate. Pre-industrial fire-history records from black carbon, charcoal and other proxies provide baseline estimates of biomass burning at local to global scales spanning millennia, and are thus useful to examine the role of fire in the carbon cycle and climate system. Here we use the specific biomarker levoglucosan together with black carbon and ammonium concentrations from the North Greenland Eemian (NEEM) ice cores (77.49° N, 51.2° W; 2480 m a.s.l) over the past 2000 years to infer changes in boreal fire activity. Increases in boreal fire activity over the periods 1000–1300 CE and decreases during 700–900 CE coincide with high-latitude NH temperature changes. Levoglucosan concentrations in the NEEM ice cores peak between 1500 and 1700 CE, and most levoglucosan spikes coincide with the most extensive central and northern Asian droughts of the past millennium. Many of these multi-annual droughts are caused by Asian monsoon failures, thus suggesting a connection between low- and high-latitude climate processes. North America is a primary source of biomass burning aerosols due to its relative proximity to the Greenland Ice Cap. During major fire events, however, isotopic analyses of dust, back trajectories and links with levoglucosan peaks and regional drought reconstructions suggest that Siberia is also an important source of pyrogenic aerosols to Greenland.

The role of human-induced fire and sweet chestnut (Castanea sativa Mill.) cultivation on the long-term landscape dynamics of the southern Swiss Alps

Changes in fire occurrence during the last decades in the southern Swiss Alps make knowledge on fire history essential to understand future evolution of the ecosystem composition and functioning. In this context, palaeoecology provides useful insights into processes operating at decadal-to-millennial time scales, such as the response of plant communities to intensified fire disturbances during periods of cultural change. We provide a high-resolution macroscopic charcoal and pollen series from Guèr, a well-dated peat sequence at mid-elevation (832 m.a.s.l.) in southern Switzerland, where the presence of local settlements is documented since the late Bronze Age and the Iron Age. Quantitative fire reconstruction shows that fire activity sharply increased from the Neolithic period (1–3 episodes/1000 year) to the late Bronze and Iron Age (7–9 episodes/1000 year), leading to extensive clearance of the former mixed deciduous forest (Alnus glutinosa, Betula, deciduous Quercus). The increase in anthropogenic pollen indicators (e.g. Cerealia-type, Plantago lanceolata) together with macroscopic charcoal suggests anthropogenic rather than climatic forcing as the main cause of the observed vegetation shift. Fire and controlled burning were extensively used during the late Roman Times and early Middle Ages to promote the introduction and establishment of chestnut (Castanea sativa) stands, which provided an important wood and food supply. Fire occurrence declined markedly (from 9 to 5–6 episodes/1000 year) during late Middle Ages because of fire suppression, biomass removal by human population, and landscape fragmentation. Land-abandonment during the last decades allowed forest to partly re-expand (mainly Alnus glutinosa, Betula) and fire frequency to increase.

Combining charcoal sediment and molecular markers to infer a Holocene fire history in the Maya Lowlands of Petén, Guatemala

Vegetation changes in the Maya Lowlands during the Holocene are a result of changing climate conditions, solely anthropogenic activities, or interactions of both factors. As a consequence, it is difficult to assess how tropical ecosystems will cope with projected changes in precipitation and land-use intensification over the next decades. We investigated the role offire during the Holocene by combining macroscopic charcoal and the molecular fire proxies levoglucosan, mannosan and galactosan. Combining these two different fire proxies allows a more robust understanding of the complex history of fire re- gimes at different spatial scales during the Holocene. In order to infer changes in past biomass burning, we analysed a lake sediment core from Lake Peten Itza, Guatemala, and compared our results with millennial-scale vegetation and climate change available in the area. We detected three periods of high fire activity during the Holocene: 9500 e 6000 cal yr BP, 3700 cal yr BP and 2700 cal yr BP. We attribute the first maximum mostly to climate conditions and the last maximum to human activities. The rapid change between burned vegetation types at the 3700 cal yr BP fire maximum may result from human activity.

Fire ecology north and south of the Alps since the last ice age

Wildfires are very rare in central Europe, which is probably why fire effects on vegetation have been neglected by most central European ecologists and palaeoecologists. Presently, reconstructions of fire history and fire ecology are almost absent. We analysed sediment cores from lakes on the Swiss Plateau (Lobsigensee and Soppensee) for pollen and charcoal to investigate the relationship between vegetation and fire. Microscopic charcoal evidence suggests increasing regional fire frequencies during the Neolithic (7350-4150 cal. BP, 5400-2200 BC) and the subsequent prehistoric epochs at Lobsigensee, whereas at Soppensee burnings remained rather rare until modern times. Neolithic peaks of charcoal at 6200 and 5500 cal. BP (4250 and 3550 BC) coincided with declines of pollen of fire-sensitive taxa at both sites (e.g., Ulmus, Tilia, Hedera, Fagus), suggesting synchronous vegetational responses to fire at regional scales. However, correlation analysis between charcoal and pollen for the period 6600-4400 cal. BP (4650-2650 BC) revealed no significant link between fire and vegetation at Soppensee, whereas at Lobsigensee increases of Corylus and decreases of Fagus were related to fire events. Fire impact on vegetation increased during the subsequent epochs at both sites. Correlation analyses of charcoal and pollen data for the period 4250-1150 cal. BP (2300 BC -AD 800) suggest that fires were intentionally set to disrupt forests and to provide open areas for arable and pastoral farming (e.g., significant positive correlations between charcoal and Cerealia, Plantago lanceolata, Asteroideae). These results are compared with southern European records (Lago di Origlio, Lago di Muzzano), which are situated in particularly fire-prone environments. After the Mesolithic period (I1 200-7350 cal. BP, 9250-5400 BC), charcoal influx was higher by an order of magnitude in the south, suggesting more frequent fires. Neolithic fires caused similar though more pronounced responses of vegetation in the south (e.g., expansions of Corylus). Post-Neolithic land-use practices involving (controlled) burning culminated in both regions at about 2550 cal. BP (c. 600 BC). However, fire-caused disappearances of entire forest communities were confined to the southern sites. Such differences in fire effects among the sites are explained by the dissimilar importance of fire as a result of different climatic conditions and cultural activities. Our results imply that the remaining (fire-sensitive) fragments of central European vegetation north of the Alps are especially endangered by increasing fire frequencies resulting from predicted climatic change.

Vegetation and fire history of coastal north-eastern Sardinia (Italy) under changing Holocene climates and land use

Little is known about the vegetation and fire history of Sardinia, and especially the long-term history of the thermo-Mediterranean belt that encompasses its entire coastal lowlands. A new sedimentary record from a coastal lake based on pollen, spores, macrofossils and microscopic charcoal analysis is used to reconstruct the vegetation and fire history in north-eastern Sardinia. During the mid-Holocene (c. 8,100–5,300 cal bp), the vegetation around Stagno di Sa Curcurica was characterised by dense Erica scoparia and E. arborea stands, which were favoured by high fire activity. Fire incidence declined and evergreen broadleaved forests of Quercus ilex expanded at the beginning of the late Holocene. We relate the observed vegetation and fire dynamics to climatic change, specifically moister and cooler summers and drier and milder winters after 5,300 cal bp. Agricultural activities occurred since the Neolithic and intensified after c. 7,000 cal bp. Around 2,750 cal bp, a further decline of fire incidence and Erica communities occurred, while Quercus ilex expanded and open-land communities became more abundant. This vegetation shift coincided with the historically documented beginning of Phoenician period, which was followed by Punic and Roman civilizations in Sardinia. The vegetational change at around 2,750 cal bp was possibly advantaged by a further shift to moister and cooler summers and drier and milder winters. Triggers for climate changes at 5,300 and 2,750 cal bp may have been gradual, orbitally-induced changes in summer and winter insolation, as well as centennial-scale atmospheric reorganizations. Open evergreen broadleaved forests persisted until the twentieth century, when they were partly substituted by widespread artificial pine plantations. Our results imply that highly flammable Erica vegetation, as reconstructed for the mid-Holocene, could re-emerge as a dominant vegetation type due to increasing drought and fire, as anticipated under global change conditions.

7000-year human legacy of elevation-dependent European fire regimes

Variability in fire regime at the continental scale has primarily been attributed to climate change, often overshadowing the widely potential impact of human activities. However, human ignition modifies the rhythm of fire episodes occurrence (fire frequency), whereas land use alters vegetation composition and fuel load, and thus the amount of biomass burned. It is unclear, however, whether and how humans have exercised a significant influence over fire regimes at continental and millennial scales. Based on sedimentary charcoal records, we use new alternative estimate of fire frequency and biomass burned for the last 16000 years (here after 16 ky) that we evaluate with outputs from climate, vegetation, land use and population models. We find that pronounced regional-scale land use changes in southern Europe at the beginning of the Neolithic (8–6 ky), during the Bronze Age (5–4 ky) and the medieval period (1 ky) caused a doubling of fire frequency compared to the Holocene average (the last 11.5 ky). Despite anthropogenic influences, southern European biomass burned decreased from 7 ky, which is in line both with changes in orbital parameters leading climate cooling and also reductions in biomass availability because of land use. Our study underscores the role of elevation-dependent parameters, and particularly biomass and land management, as major drivers of fire regime variability. Results attest a determinant anthropogenic driving-force on fire regime and a decrease in fire-carbon emissions since 7 ky in Southern Europe.

A case of homicidal intraoral gunshot and review of the literature

Determination of the manner of death in case of intraoral firearm wounds can be a challenge, especially if the circumstances of the incident are unclear and crime scene investigation is inadequate. It is a well-known fact that the mouth is one of the selected sites for suicide with firearms. Homicidal shooting through the mouth is said to be rare, but does occur, and can be mistaken for a suicide. For discrimination between suicide and homicide in cases of intraoral firearm wounds, some useful points are the site of entry wound, the direction of the internal bullet path, the range of fire and the circumstances of death. We demonstrate these points in a case of a homicidal gunshot to the mouth assessed by both classical autopsy and post-mortem CT (PMCT).

Identification of key residues in virulent canine distemper virus hemagglutinin that control CD150/SLAM-binding activity

Morbillivirus cell entry is controlled by hemagglutinin (H), an envelope-anchored viral glycoprotein determining interaction with multiple host cell surface receptors. Subsequent to virus-receptor attachment, H is thought to transduce a signal triggering the viral fusion glycoprotein, which in turn drives virus-cell fusion activity. Cell entry through the universal morbillivirus receptor CD150/SLAM was reported to depend on two nearby microdomains located within the hemagglutinin. Here, we provide evidence that three key residues in the virulent canine distemper virus A75/17 H protein (Y525, D526, and R529), clustering at the rim of a large recessed groove created by beta-propeller blades 4 and 5, control SLAM-binding activity without drastically modulating protein surface expression or SLAM-independent F triggering.

Predictability of biomass burning in response to climate changes

Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo- fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.

Iatrogenic atrial septal defect, erosion of the septum primum after device closure of a patent foramen ovale as a new medical entity

Iatrogenic atrial septal defects are described in 2 patients. They occurred after implantation of Amplatzer occluders to close a patent foramen ovale. While device erosions to the extra-atrial space have been described, erosion induced atrial septal defects are a new medical entity. They may be fairly common in the situation of an atrial septal aneurysm whipping the rim of the device incessantly. They are clinically silent and benign and require echocardiography for detection. A second device solved the problem in the cases described.

MR findings of endocardial fibroelastosis in children

BACKGROUND: Endocardial fibroelastosis (EFE) is characterized by a diffuse white fibrous tissue lining the endocardium. The diagnosis is difficult to establish because clinical symptoms and electrocardiographic findings are nonspecific. Surgical resection of EFE requires the establishment of the diagnosis and delineation of the extent of the fibrotic changes. OBJECTIVE: To describe the use of MRI in the assessment of EFE in children. MATERIALS AND METHODS: Three children after surgery for aortic stenosis who were suspected of having EFE were evaluated by echocardiography and MRI. The MR evaluation consisted of black-blood, triple IR, bright-blood, perfusion and myocardial delayed-enhancement sequences. EFE was confirmed at surgery in all patients. RESULTS: Echocardiograms demonstrated vigorous systolic function but substantial diastolic dysfunction of the left ventricle in all. Mild endocardial brightening of the anterior septum, anterior wall, or papillary muscles was present in two. No study was thought to be diagnostic of endocardial fibrosis. On MRI EFE manifested at the endocardial surface as a rim of hypointense signal in the perfusion sequences and as a rim of hyperintense signal in the myocardial delayed-enhancement sequences. The black-blood, triple IR, and bright-blood sequences were not diagnostic. CONCLUSION: The diagnosis of EFE is difficult to establish by echocardiography. MRI using perfusion and myocardial delayed enhancement can be useful in establishing the diagnosis.

Global biomass burning: a synthesis and review of Holocene paleofire records and their controls

We synthesize existing sedimentary charcoal records to reconstruct Holocene fire history at regional, continental and global scales. The reconstructions are compared with the two potential controls of burning at these broad scales – changes in climate and human activities – to assess their relative importance on trends in biomass burning. Here we consider several hypotheses that have been advanced to explain the Holocene record of fire, including climate, human activities and synergies between the two. Our results suggest that 1) episodes of high fire activity were relatively common in the early Holocene and were consistent with climate changes despite low global temperatures and low levels of biomass burning globally; 2) there is little evidence from the paleofire record to support the Early Anthropocene Hypothesis of human modification of the global carbon cycle; 3) there was a nearly-global increase in fire activity from 3 to 2 ka that is difficult to explain with either climate or humans, but the widespread and synchronous nature of the increase suggests at least a partial climate forcing; and 4) burning during the past century generally decreased but was spatially variable; it declined sharply in many areas, but there were also large increases (e.g., Australia and parts of Europe). Our analysis does not exclude an important role for human activities on global biomass burning during the Holocene, but instead provides evidence for a pervasive influence of climate across multiple spatial and temporal scales.

The nitrogen cycle of tropical montane forest in Ecuador turns inorganic under environmental change

Water-bound nitrogen (N) cycling in temperate terrestrial ecosystems of the Northern Hemisphere is today mainly inorganic because of anthropogenic release of reactive N to the environment. In little-industrialized and remote areas, in contrast, a larger part of N cycling occurs as dissolved organic N (DON). In a north Andean tropical montane forest in Ecuador, the N cycle changed markedly during 1998–2010 along with increasing N deposition and reduced soil moisture. The DON concentrations and the fractional contribution of DON to total N significantly decreased in rainfall, throughfall, and soil solutions. This inorganic turn of the N cycle was most pronounced in rainfall and became weaker along the flow path of water through the system until it disappeared in stream water. Decreasing organic contributions to N cycling were caused not only by increasing inorganic N input but also by reduced DON production and/or enhanced DON decomposition. Accelerated DON decomposition might be attributable to less waterlogging and higher nutrient availability. Significantly increasing NO3-N concentrations and NO3-N/NH4-N concentration ratios in throughfall and litter leachate below the thick organic layers indicated increasing nitrification. In mineral soil solutions, in contrast, NH4-N concentrations increased and NO3-N/NH4-N concentration ratios decreased significantly, suggesting increasing net ammonification. Our results demonstrate that the remote tropical montane forests on the rim of the Amazon basin experienced a pronounced change of the N cycle in only one decade. This change likely parallels a similar change which followed industrialization in the temperate zone of the Northern Hemisphere more than a century ago.