Boreal forests cover vast areas of the permafrost zones of North America, and changes in their composition and structure can lead to pronounced impacts on the regional and global climate. We ...partition the variation in regional boreal tree cover changes between 2000 and 2014 across the Taiga Plains, Canada, into its main causes: permafrost thaw, wildfire disturbance, and postfire regrowth. Moderate Resolution Imaging Spectroradiometer Percent Tree Cover (PTC) data are used in combination with maps of historic fires, and permafrost and drainage characteristics. We find that permafrost thaw is equally important as fire history to explain PTC changes. At the southern margin of the permafrost zone, PTC loss due to permafrost thaw outweighs PTC gain from postfire regrowth. These findings emphasize the importance of permafrost thaw in controlling regional boreal forest changes over the last decade, which may become more pronounced with rising air temperatures and accelerated permafrost thaw.
Key Points
Permafrost thaw and fire are equally important controls on tree cover change in the Taiga Plains
Declining tree cover is mostly limited to poorly drained areas at the southern limit of permafrost
Boreal tree cover is increasing in areas with more stable discontinuous and continuous permafrost
The Arctic is a water-rich region, with freshwater systems covering about 16 % of the northern permafrost landscape. Permafrost thaw creates new freshwater ecosystems, while at the same time ...modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic (still) and lotic (moving) systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying factors determine (i) the degree to which permafrost thaw manifests as thermokarst, (ii) whether thermokarst leads to slumping or the formation of thermokarst lakes, and (iii) the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can be considerable, with these modifying factors determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted lakes and streams is also likely to change; these systems have unique microbiological communities, and show differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter, and nutrient delivery. The degree to which thaw enables the delivery of dissolved vs. particulate organic matter, coupled with the composition of that organic matter and the morphology and stratification characteristics of recipient systems will play an important role in determining the balance between the release of organic matter as greenhouse gases (CO2 and CH4), its burial in sediments, and its loss downstream. The magnitude of thaw impacts on northern aquatic ecosystems is increasing, as is the prevalence of thaw-impacted lakes and streams. There is therefore an urgent need to quantify how permafrost thaw is affecting aquatic ecosystems across diverse Arctic landscapes, and the implications of this change for further climate warming.
Birth-related fractures are an important differential diagnosis of child abuse in early infancy. While fractures associated to vaginal deliveries are well known, cesarean section is not necessarily ...known to cause such injuries. Nevertheless neonatal fractures have been described after cesarean sections. To give an overview over the frequency and typical locations of such fractures, the appearance of symptoms and the timespan until diagnosis, a literature research was conducted via Google scholar and Pubmed, using the key words “cesarean section” and “fractures”. Birth-related fractures after cesarean sections are rare but can occur, with the long bones being particularly affected. Therefore, birth injuries should always be considered in the forensic medical assessment of fractures in early infancy, even after cesarean section. To enable a differentiation between birth trauma and physical abuse, birth and operation records should be checked for surgical manoeuvres, possible difficulties during the procedure or other risk factors. Birth-related fractures are usually detected early; in rare cases, the diagnosis is made only weeks after birth.
The vitality of a human being is closely connected to temporal variations of its body geometry. This is quite obvious in the case of walking. But also when resting, the motion of inner organs such as ...lung or heart causes geometric alterations which may be registered by high-resolution ultra-wideband radar. Since the radio waves radiated by such radars are absolutely harmless, they may be deployed for monitoring of resident activities helping to ensure health, safety, and well-being of aged or needy people. These waves may also penetrate most of building materials and snow which makes them useful to detect earthquake and avalanche survivors, too. The most challenging task is the registration of respiration activity of an unconscious person. The principle of breathing motion detection by radar is explained and the major handicaps as well as appropriate counter measures are discussed. The possible structure of a survivor and residential injury detection radar system is considered and some results from field trials are summarized.
It remains uncertain how the net ecosystem CO2 exchange (NEE) of diverse peatlands will respond to warming. Here we compare five years of eddy covariance measurements of NEE and estimates of gross ...primary productivity and ecosystem respiration between a fen dominated by deciduous vegetation and an adjacent bog with evergreen vegetation in the Canadian Hudson Bay Lowlands. At the bog, daily net CO2 uptake lasted from snowmelt to snow cover onset, while at the fen, net CO2 uptake was delayed in spring and ended earlier in fall. Greater midsummer net CO2 uptake at the fen compensated for shoulder season net CO2 losses resulting in similar annual NEE at the two sites (fen: −52 ± 16 g C m−2, bog: −80 ± 14 g C m−2). Observations of a satellite‐based productivity index also suggest lower shoulder season and higher peak vegetation productivity at these deciduous versus evergreen plant‐dominated peatlands. The response of NEE to warmer weather differed between sites. Warming during the shoulder seasons increased net CO2 uptake at the evergreen plant‐dominated bog, while it increased net CO2 losses at the fen where deciduous leaves had not yet emerged or had senesced. In contrast, warmer weather during the peak growing season appeared to reduce net CO2 uptake more at the bog than the fen resulting from both increasing ecosystem respiration and decreasing gross primary productivity. In the short term, warming will likely decrease annual net CO2 uptake of these and similar peatlands, although the magnitude will depend on factors including vegetation dynamics and seasonality of warming.
Plain Language Summary
Peatland ecosystems are large reservoirs of carbon as their long‐term productivity slightly exceeds decomposition. Peatlands are also highly diverse ecosystems with some dominated by evergreen vegetation, while others are dominated by deciduous vegetation, which shed leaves in the fall and grow new leaves in spring. Due to these different leaf strategies, we expect that the net exchange of carbon dioxide (CO2) between peatlands and the atmosphere will differ through the year and respond differently to warmer weather. Five years of measurements of CO2 exchange between land and atmosphere at two adjacent peatlands with contrasting vegetation revealed contrasting seasonal patterns in productivity (CO2 uptake) and respiration (CO2 loss to the atmosphere) but similar annual CO2 uptake. During the summer, net CO2 uptake decreased with warmer air temperatures at both sites. In spring, the evergreen plant‐dominated vegetation benefitted more from warmer air temperatures as plants started growing immediately following snowmelt while leaves of deciduous plants had not yet emerged. These contrasting productivity patterns were also reflected in satellite‐based observations throughout the study region of the Canadian Hudson Bay Lowlands. Our study suggests that currently, warmer air temperatures likely reduce the amount of CO2 taken up by these peatlands.
Key Points
Annual CO2 sink strength of two peatland ecosystems are similar despite different evergreen and deciduous vegetation communities
Warmer peak growing season temperature largely decreases net CO2 uptake of both evergreen and deciduous plant‐dominated peatlands
Warmer shoulder season temperature decreases net CO2 uptake at the deciduous‐dominated peatland
Northern peatlands are globally important carbon (C) and nitrogen (N) sinks due to slow decomposition rates resulting in long‐term organic matter accumulation. Despite their large N storage, ...peatlands depend on sources of bio‐available N to sustain their biomass production. Di‐nitrogen (N2) fixation represents an important biological N source in ombrotrophic bogs, but its environmental controls are still poorly understood. We examined seasonal and spatial variability of Sphagnum‐associated N2 fixation across a hydrological transect (hummock‐hollow‐beaver pond edge) in a temperate ombrotrophic bog. We measured N2 fixation in live Sphagnum plants by acetylene reduction assay calibrated with a 15N2 tracer method, bi‐weekly, from May to November over two growing seasons. We found that N2 fixation increased with soil temperature at 5 cm in the living Sphagnum mat explaining the seasonal variability in N2 fixation. Peak N2 fixation rates occur in mid‐August, when N2 fixation rates are about 10 times larger than during the shoulder seasons (May and November). Spatially, N2 fixation was larger in wetter Sphagnum with larger gravimetric water content in Sphagnum. This relationship was most pronounced in the peak growing season when N2 fixation rates were the highest. Finally, we estimated that the Mer Bleue bog receives around 0.3 g N m−2 annually through Sphagnum‐associated N2 fixation, which accounts for about a fourth of the N accumulated annually into Sphagnum. Future contributions from Sphagnum‐associated N2 fixation to N budgets in peatlands will depend on temperature and moisture changes which have contrasting effects on N2 fixation rates.
Plain Language Summary
Nitrogen is an important nutrient supporting plant growth. In rain‐fed peatlands (bogs), biological N2 fixation from atmospheric N2 represents an important N input to the ecosystem. There, Sphagnum mosses represent the dominant plant genus and host microbes capable of fixing nitrogen. Despite being an important source of nitrogen, the environmental controls on N2 fixation in bogs are still poorly understood. Here, we find that N2 fixation across the bog increases with temperature in Sphagnum throughout the growing season. Within the bog, areas of high N2 fixation are best characterized by high Sphagnum water content while areas of low N2 fixation are usually drier. N2 fixation most strongly follows these moisture patterns during the peak growing season when temperatures in Sphagnum reach their peak. In the fall and spring, when temperatures are cooler, these relationships become weaker. Our results show that both temperature and moisture in Sphagnum drive Sphagnum‐associated N2 fixation in bogs. Our study helps us to better understand how N2 fixation and thus nutrient availability may change with a warming climate in nutrient‐poor bogs. Through its impact on plant growth, changes in nutrient availability have the potential to modify future long‐term carbon and nitrogen accumulation rates in these ecosystems.
Key Points
N2 fixation in Sphagnum represents an important biological N source in ombrotrophic bogs
Seasonal and spatial variability of N2 fixation was best explained by Sphagnum temperature and moisture, respectively
Future Sphagnum‐associated N2 fixation will depend on temperature and moisture changes which have contrasting effects
•CO2 flux measurement errors (IRGASON & EC150) scale with kinematic temperature flux.•Relative errors are most pronounced when true CO2 flux is small and heat flux large.•Using a fast-response air ...temperature to scale CO2 absorption minimizes bias.•Agreement between open- and closed-path IRGA CO2 fluxes is substantially improved.•Fast-instead of slow-response air temperature should be used to scale CO2 absorption.
Across a global network of eddy covariance flux towers, two relatively new open-path infrared gas analyzers (IRGAs), the IRGASON and the EC150, are increasingly used to measure net carbon dioxide (CO2) fluxes (Fc_OP). Differences in net CO2 fluxes derived from open- and closed-path IRGAs in general remain poorly constrained. In particular, the performance of the IRGASON and the EC150 for measuring Fc_OP has not been characterized yet. These IRGAs measure CO2 absorption, which is scaled with air temperature and pressure before converting it to instantaneous CO2 density. This sensor-internal conversion is based on a slow-response thermistor air temperature measurement. Here, we test if the high-frequency temperature attenuation causes selectively systematic Fc_OP errors that scale with kinematic temperature fluxes. First, we examine the relationship between wintertime Fc_OP and kinematic temperature fluxes for eight northern ecosystems. Second, we investigate how residuals between Fc_OP and CO2 fluxes from co-located closed-path IRGAs (FC_CP) are related to kinematic temperature fluxes for three different ecosystem types (i.e., boreal forest, grassland, and irrigated cropland). We find that kinematic temperature fluxes, but not mean ambient air temperatures or CO2 flux regime, consistently determine the absolute magnitude of Fc_OP errors. This selectively systematic bias causes the most pronounced relative Fc_OP errors to occur when “true” CO2 fluxes are low and kinematic temperature fluxes are high (e.g., northern ecosystems during the winter). The smallest relative errors occur during periods with large “true” CO2 fluxes and low kinematic temperature fluxes. To address this bias, we replace the slow-response air temperature in the absorption-to-CO2 density conversion with a fast-response air temperature derived from sonic anemometer measurements. The use of the fast-response air temperature improves the agreement between half-hourly Fc_OP and FC_CP for all open- versus closed-path IRGA comparisons. Additionally, cumulative Fc_OP and Fc_CP sums are more comparable as differences drop from 63 %–13 % to 20 %–8 %. The improved IRGASON and EC150 performance enhances the ability and confidence to synthesize flux measurements across multiple sites including these two relatively new IRGAs.
Peatlands are globally important long‐term sinks of atmospheric carbon dioxide (CO2). However, there is concern that climate change‐mediated drying will reduce gross primary productivity (GPP) and ...increase ecosystem respiration (ER) making peatlands vulnerable to a weaker carbon sink function and potential net carbon loss. While large and deep peatlands are usually resilient to moderate summer drying, CO2 exchange in shallow Boreal Shield peatlands is likely more sensitive to drying given the reduced groundwater connectivity and water storage potential. To better understand the carbon cycling responses of Boreal Shield peatlands to meteorological conditions, we examined ecohydrological controls on CO2 fluxes using the eddy covariance technique at a shallow peatland during the summer season for 5 years, from 2016–2020. We found lower GPP in dry summer years. Mean summer water table depth (WTD) was found to be significantly correlated with summer total net ecosystem CO2 exchange (R2 = 0.78; p value = 0.046) and GPP (R2 = 0.83; p value = 0.03), where wet summers with a WT close to the peat surface sequestered more than twice the amount of CO2 than dry summers. Our findings suggest that shallow Boreal Shield peatland GPP may be sensitive to climate‐mediated drying as they may switch to a net CO2 source in the summer season when WTDs exceed a critical ecohydrological threshold for a prolonged period of time.
Plain Language Summary
Peatlands take in carbon from the atmosphere and store it in the ground as peat, a process that helps to regulate climate change. Peatlands in the Boreal Shield are positioned in bedrock basins. Their water table (WT) is controlled by precipitation, which can trigger water flow over the bedrock between wetland ecosystems. Due to this unique setting, we expected Boreal Shield peatlands to be more sensitive to differences in growing season meteorological conditions from year to year. We used 5 years of carbon dioxide (CO2) exchange measurements between land and atmosphere during the summer season in a Boreal Shield peatland in Ontario, Canada. We found the peatland vegetation took up more CO2 from the atmosphere during summers with more rain which keeps the WT in the peatland closer to the peat surface. The peatland took up less CO2 when the summer was dry. Our findings provide insight into how Boreal Shield peatlands are responding to summer droughts under current climate conditions.
Key Points
Summers with higher rainfall (and lower P‐PET) maintain a water table near the peat surface and have greater net carbon dioxide (CO2) uptake
Interannual differences in summer net ecosystem CO2 exchange are attributable to changes in summer gross primary production
Shallow Boreal Shield peatlands may switch to a net carbon source in the summer season
•Epithelioid trophoblastic tumors are very rare, only ∼120 cases have been published.•Clinical features vary.•The diagnosis of ETT is mostly possible using immunohistochemistry.•The aim of therapy in ...ETT is complete surgical removal.•A multimodal treatment is recommended in advanced disease.
Epithelioid trophoblastic tumor (ETT) is a rare gestational trophoblastic tumor, first described by Shih and Kurman in 1998. ETT often present as abnormal vaginal bleeding in women of reproductive age, but unlike more common forms of GTN tend to produce much less human chorionic gonadotropin (hCG) for the volume of disease present. ETT can occur after any gestational event and can occur in both intrauterine and extrauterine sites. We present a case of a 46-year-old female patient incidentally diagnosed with ETT and hepatic metastasis. Therapy was multimodal and involved chemotherapy, operation, thermoablation of liver metastases and immunocheckpoint inhibitor. The patient remains disease free for almost four years now. ETT presents a diagnostic challenge due to their rarity and histologic resemblance to other pathologies. ETT can be relatively chemo resistant and are therefore often treated surgically. Misdiagnosis might delay effective treatment and affects survival.
•The time for cleaning egg yolk deposits is minimum between pH 7 and 13.•Removal behaviour (cohesive and adhesive) of egg yolk depended on the pH.•Micromanipulation results showed the best ...correlation with cleaning behaviour.•Swelling, diffusion and rheological data provide insight into stages in cleaning.•All stages in cleaning must be considered to predict the cleaning behaviour by a laboratory method.
Cleaning-in-place (CIP) is an established technique for the cleaning of industrial food processing plants. To design CIP protocols, laboratory methods are helpful to predict the cleaning behaviour and to reduce the number of costly in situ cleaning investigations. In this work, laboratory methods (differential scanning calorimetry, rheology, optical swelling measurements and micromanipulation) were used to analyse different aspects and stages of the cleaning process (swelling, chemical and mechanical actions, phase transition and mass transfer). The suitability of these methods to predict the cleaning behaviour was tested by using a representative egg yolk deposit. Temperature (24–60°C) and NaOH concentration (0–1.5%) of the cleaning fluid served as independent factors, and the time necessary to remove the deposit in a flow channel was evaluated using an optical method. Cleaning time decreased with increasing temperature and also depended on NaOH concentration. Within the examined limits, the pushing energy measured by the micromanipulation method showed the best correlation with cleaning time, whereas swelling, diffusion and rheological measurements only reflected tendencies of the cleaning behaviour.
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