Community Structure and Water Quality Assessment of Benthic Macroinvertebrates in Hongze Lake.

This study investigated the species, density, biomass and physicochemical factors of benthic macroinvertebrates in Hongze Lake from 2016 to 2020. Redundancy analysis (RDA) was used to analyze the relationship between physicochemical parameters and the community structure of macroinvertebrates. Macroinvertebrate-based indices were used to evaluate the water quality conditions in Hongze Lake. The results showed that a total of 50 benthic species (10 annelids, 21 arthropods and 19 mollusks) were collected. The community structure of benthic macroinvertebrates varied in time and space. The dominant species were Limnodrilus hoffmeisteri (L.hoffmeisteri), Corbicula fluminea (C.fluminea), Nephtys oligobranchia (N.oligobranchia). In 2016, arthropods such as Grandidierella sp. were the dominant species of benthos in Hongze Lake while annelids and mollusks dominated from 2017 to 2020, such as L.hoffmeisteri, N.oligobranchia, C.fluminea. The benthic fauna of Chengzi Lake and Lihewa District were relatively abundant and showed slight variation, while the benthic macroinvertebrates of the Crossing the water area were few and varied greatly. RDA showed that changes in benthic macroinvertebrate structure were significantly correlated with dissolved oxygen (DO), Pondus Hydrogenii (pH) and transparency (SD). The Shannon Wiener, Pielou, and Margalef indices indicate that Hongze Lake is currently in a moderately polluted state. Future studies should focus on the combined effects of various physicochemical indicators and other environmental factors on benthic communities.

"I think that comes with experience": A thematic analysis exploring how dental students at a transitional stage of training understand and engage with reflection.

INTRODUCTION: Reflection is an important skill for dentists but there is little consensus about how reflection can most usefully be integrated into dental education. The aim of this study was to conduct focus groups to explore how students at a transitional point of dental education in one UK dental school had experienced, and conceptualised reflection. METHODS: Students at the beginning of their clinical studies were recruited by email and invited to attend a single focus group. Focus groups were co-facilitated by a team of staff and student researchers and analysed using thematic analysis. Students acted as research partners in planning a topic guide, recruiting students, conducting focus groups and considering the implications of research findings for the curriculum, and contributed their perspectives to other aspects of the research. RESULTS: Students primarily associated reflection with their clinical learning and valued the skill highly in this context. They were less familiar with the potential for reflection to support personal development and deeper learning. Themes were identified of learning, uncertainty, emotions and wellbeing, community and challenges and are discussed in detail. CONCLUSION: Reflection is highly valued within our dental education setting but many students may be missing out on using it to its' full potential. Changes to the undergraduate curriculum, including offering reflection from an early stage of education may be warranted.

Timing of Readmissions After Elective Total Hip and Knee Arthroplasty: Does a 30-Day All-Cause Rate Capture Surgically Relevant Readmissions?

BACKGROUND: The 30-day all-cause readmission rate is a widely used metric of hospital performance. However, there is lack of clarity as to whether 30 days is an appropriate time frame following surgical procedures. Our aim is to determine whether a 90-day time window is superior to a 30-day time window in capturing surgically relevant readmissions after total hip arthroplasty (THA) and total knee arthroplasty (TKA). METHODS: We analyzed readmissions following all primary THAs and TKAs recorded in the English National Health Service Hospital Episode Statistics database from 2008 to 2018. We compared temporal patterns of 30- and 90-day readmission rates for the following types of readmission: all-cause, surgical, return to theater, and those related to specific surgical complications. RESULTS: A total of 1.47 million procedures were recorded. After THA and TKA, over three-quarters of 90-day surgical readmissions took place within the first 30 days (78.5% and 75.7%, respectively). All-cause and surgical readmissions both peaked at day 4 and followed a similar temporal course thereafter. The ratio of surgical to medical readmissions was greater for THA than for TKA, with THA dislocation both being one of the most common surgical complications and clustering early after discharge, with 73.5% of 90-day dislocations occurring within the first 30 days. CONCLUSION: The 30-day all-cause readmission rate is a good reflection of surgically relevant readmissions that take place in the first 90 days after THA and TKA.

Randomised controlled trial: Shoulder-umbilicus length versus body weight measurement for optimal endotracheal tube depth estimation in ventilated infants.

AIM: The optimal placement of the endotracheal tube (ETT) in ventilated infants is essential, but birthweight may be not the best parameter to predict it. The aim of this study was a direct comparison of shoulder-umbilical length (experimental group) versus birthweight (control group) as predictor of optimal ETT placement in Malaysian ventilated infants. METHODS: All infants requiring ventilation in the neonatal intensive care unit of a tertiary hospital in Malaysia during the 4-month study period were eligible to enter this randomised controlled trial. All participants were randomised into two groups: experimental and control group. The main outcome measure was malposition of the ETT (requiring adjustment), as seen on the chest X-ray performed within 1 h after intubation. Tube placement was assessed by two neonatologists, blinded to the allocation. RESULTS: One hundred and ten infants were randomised, 55 in each group. The ETT was malpositioned in 13 of 55 infants (23%) for the experimental group and 22 of 55 infants (40%) in the control group (P = 0.06). CONCLUSION: In the experimental group, fewer infants showed a need for tube adjustment than in the control group. While a larger study may be necessary to show statistical significance, the difference shown in this study may be large enough to be of clinical significance.

Volume fusion of CT images to measure femoral symmetricity.

PURPOSE: Pre-operative planning is widely used in orthopaedic surgery. In case of trauma with fracture or previous injury with malunion, the contralateral extremity is used as a surrogate for planning with an assumption of symmetry between sides. The aim of this study was to investigate femoral symmetricity in human adults. METHODS: Ten randomly selected lower extremity computerized tomography (CT) images were analyzed for femur symmetry using 3D Trauma and CT motion analysis (CTMA). Mirrored images of the left femur were created using the right as a template. The 3D images from each side were merged, and translational and rotational differences reported. RESULTS: There were no statistically significant differences between mirrored images of the left and right femurs. Differences in rotation and translation of bony segmentation showed a greater variation in internal and external rotation of the distal femur (CI - 0.7° to 4.9°) compared to varus/valgus (CI - 1.3° to 0.8°) or flexion/extension (CI - 0.5° to 0.6°), though none of these differences were significant. CONCLUSION: The left and right femurs of healthy adults are symmetrical. Pre-operative templating relying on the contralateral healthy femur is encouraged.

The Validity of All-Cause 30-Day Readmission Rate as a Hospital Performance Metric After Primary Total Hip and Knee Arthroplasty: A Systematic Review.

BACKGROUND: Risk-adjusted all-cause 30-day readmission rate (ACRR) following total hip arthroplasty (THA) and total knee arthroplasty (TKA) is currently used as a metric of hospital performance as part of the Hospital Readmissions Reduction Program. However, the extent to which it is determined by hospital-related factors and is therefore a fair method of determining reimbursement remains unclear. METHODS: Our aim was to systematically review the available literature pertaining to whether ACRR is a valid metric of hospital performance after elective primary THA or TKA as determined by (1) its association with other performance metrics, (2) the extent to which variation in ACRR can be explained by between-hospital variation, and (3) the relative importance of hospital-related versus surgeon- or patient-related factors in determining ACRR. The MEDLINE, EMBASE, and Health Management Information Consortium databases were searched from inception to November 2018 and reference lists of selected articles scanned. The final list of articles was determined by consensus. RESULTS: Eight articles were included. Correlation of ACRR with established composite metrics of both outcome and process measures was poor. There was a weak positive correlation between ACRR and mortality. Only 1.5% of the variation in readmission rates for THA and TKA was found to be attributable to hospital-level factors, with patient-related factors such as age and comorbidities having much greater influence. Use of composite outcome metrics, for example, combining readmission and mortality, or considering the "surgical" readmission rate, improved the sensitivity to detect important between-hospital variation. CONCLUSION: There is insufficient evidence in the current literature to justify the use of ACRR following elective THA and TKA for financially penalizing hospitals. Further work is needed to define what is acceptable variation. The use of a composite metric or surgical readmission rate may improve the ability to detect between-hospital variation.

Predictors of 30-Day Readmission After Total Knee Arthroplasty: Analysis of 566,323 Procedures in the United Kingdom.

BACKGROUND: All-cause 30-day readmission after total knee arthroplasty (TKA) is currently used as a measure of hospital performance in the United States and elsewhere. Readmissions from surgical causes may more accurately reflect preventability and costs. However, little is known about whether predictors of each type of readmission differ. METHODS: All primary TKAs recorded in England's National Health Service administrative database from 2006 to 2015 were included. Multilevel logistic regression analysis was used to describe the effects of patient-related factors on 30-day readmission risk using 3 different readmission metrics: all-cause, surgical (defined using International Classification of Disease-10 primary admission diagnoses), and those resulting in return to theater (RTT). RESULTS: In total, 566,323 procedures were recorded. The comorbidity with the highest odds ratio (OR) for all types of readmission was psychoses (RTT OR 2.52, P < .001). Obesity was a strong independent predictor of RTT (OR 1.36, P < .001) and had the highest population attributable fraction of any comorbidity (4.7%). Unicompartmental arthroplasty was associated with a significantly lower risk of all types of readmission when compared with TKA, with the effect being most pronounced for surgical readmission (OR 0.66, P < .001). RTT in the index episode increased the risk of RTT readmission (OR 2.80, P < .001), as did any emergency admission to hospital in the preceding 12 months (for >2 emergency admissions, all-cause OR 2.38, P < .001). Length of stay either more than or less than 2 days was associated with an increased risk of all-cause and surgical readmission but not RTT readmission. CONCLUSION: Patient-related predictors of surgical and RTT readmission following TKA differ from those for all-cause readmission, but only the latter metric is in widespread use.

Cross-border movement, economic development and malaria elimination in the Kingdom of Saudi Arabia.

Malaria at international borders presents particular challenges with regards to elimination. International borders share common malaria ecologies, yet neighboring countries are often at different stages of the control-to-elimination pathway. Herein, we present a case study on malaria, and its control, at the border between Saudi Arabia and Yemen. Malaria program activity reports, case data, and ancillary information have been assembled from national health information systems, archives, and other related sources. Information was analyzed as a semi-quantitative time series, between 2000 and 2017, to provide a plausibility framework to understand the possible contributions of factors related to control activities, conflict, economic development, migration, and climate. The malaria recession in the Yemeni border regions of Saudi Arabia is a likely consequence of multiple, coincidental factors, including scaled elimination activities, cross-border vector control, periods of low rainfall, and economic development. The temporal alignment of many of these factors suggests that economic development may have changed the receptivity to the extent that it mitigated against surges in vulnerability posed by imported malaria from its endemic neighbor Yemen. In many border areas of the world, malaria is likely to be sustained through a complex congruence of factors, including poverty, conflict, and migration.

Keep your feet warm? A cryptic refugium of trees linked to a geothermal spring in an ocean of glaciers.

Up to now, the most widely accepted idea of the periglacial environment is that of treeless ecosystems such as the arctic or the alpine tundra, also called the tabula rasa paradigm. However, several palaeoecological studies have recently challenged this idea, that is, treeless environments in periglacial areas where all organisms would have been exterminated near the glacier formed during the Last Glacial Maximum, notably in the Scandinavian mountains. In the Alps, the issue of glacial refugia of trees remains unanswered. Advances in glacier reconstructions show that ice domes did not cover all upper massifs, but glaciers filled valleys. Here, we used fossils of plant and malacofauna from a travertine formation located in a high mountain region to demonstrate that trees (Pinus, Betula) grew with grasses during the Lateglacial-Holocene transition, while the glacier fronts were 200-300 m lower. The geothermal travertine started to accumulate more than 14,500 years ago, but became progressively more meteogene about 11,500 years ago due to a change in groundwater circulation. With trees, land snails (gastropods) associated to woody or open habitats and aquatic mollusc were also present at the onset of the current interglacial, namely the Holocene. The geothermal spring, due to warm water and soil, probably favoured woody glacial ecosystems. This new finding of early tree growth, combined with other scattered proofs of the tree presence before 11,000 years ago in the western Alps, changes our view of the tree distribution in periglacial environments, supporting the notion of tree refugia on nunataks in an ocean of glaciers. Therefore, the tabula rasa paradigm must be revisited because it has important consequences on the global changes, including postglacial plant migrations and biogeochemical cycles.

Comparison of 3 Types of Readmission Rates for Measuring Hospital and Surgeon Performance After Primary Total Hip and Knee Arthroplasty.

BACKGROUND: All-cause 30-day hospital readmission is in widespread use for monitoring and incentivizing hospital performance for patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, little is known on the extent to which all-cause readmission is influenced by hospital or surgeon performance and whether alternative measures may be more valid. METHODS: This is an observational study using multilevel modeling on English administrative data to determine the interhospital and intersurgeon variation for 3 readmission metrics: all-cause, surgical, and return-to-theater. Power calculations estimated the likelihood of identifying whether the readmission rate for a surgeon or hospital differed from the national average by a factor of 1.25, 1.5, 2, or 3 times, for both average and high-volume providers. RESULTS: 259,980 THAs and 311,033 TKAs were analyzed. Variations by both surgeons and hospitals were smaller for the all-cause measure than for the surgical or return-to-theater metrics, although statistical power to detect differences was higher. Statistical power to detect surgeon-level rates of 1.25 or 1.5 times the average was consistently low. However, at the hospital level, the surgical readmission measure showed more variation by hospital while maintaining excellent power to detect differences in rates between hospitals performing the average number of THA or TKA cases per year in England. In practice, more outliers than expected from purely random variation were found for all-cause and surgical readmissions, especially at hospital level. CONCLUSION: The 30-day surgical readmission rate should be considered as an adjunctive measure to 30-day all-cause readmission rate when assessing hospital performance.

The effect of handover location on trauma theatre start time: An estimated cost saving of £131 000 per year.

BACKGROUND: The National Health Service was estimated to be in £2.45 billion deficit in 2015 to 2016. Trauma theatre utilization and efficiency has never been so important as it is estimated to cost £15/minute. METHODS: Structured questionnaires were given to 23 members of staff at our Trust who are actively involved in the organization or delivery of orthopaedic trauma lists at least once per week. This was used to identify key factors that may improve theatre efficiency. Following focus group evaluation, the location of the preoperative theatre meeting was changed, with all staff involved being required to attend this. Our primary outcome measure was mean theatre start time (time of arrival in the anaesthetic room) during the 1 month immediately preceding the change and the month following the change. RESULTS: Theatre start time was improved on average 24 minutes (1 month premeeting and postmeeting change). This equates to a saving of £360 per day, or £131 040 per year. CONCLUSION: Changing the trauma meeting location to a venue adjacent to the trauma theatre can improve theatre start times, theatre efficiency, and therefore result in significant cost savings.

Strategies to Improve Start Time in the Operating Theatre: a Systematic Review.

Operating theatres represent a significant cost burden for healthcare providers around the world. Theatre start time is widely acknowledged as an important target for efficiency savings. However, there is uncertainty surrounding the effectiveness of strategies to improve start time, and questions regarding the barriers to their implementation. We conducted a systematic review of bibliographic databases to identify primary research papers assessing the effect of interventions on theatre start time. Two hundred and nine papers were found from electronic literature search with 14 being included in the final review. Financial incentives, educational approaches, system-based techniques, communication, the 'golden patient' initiative and 'the productive operating theatre' scheme have all been shown to improve start time. However, questions remain over which is the most effective, the longevity of their effects and whether the results can be extrapolated beyond the context in which they were studied. We summarise the key approaches reported in the literature and identify areas for future research. This is of use to clinicians and hospital managers seeking to improve efficiency and achieve cost savings.

Control of the multimillennial wildfire size in boreal North America by spring climatic conditions.

Wildfire activity in North American boreal forests increased during the last decades of the 20th century, partly owing to ongoing human-caused climatic changes. How these changes affect regional fire regimes (annual area burned, seasonality, and number, size, and severity of fires) remains uncertain as data available to explore fire-climate-vegetation interactions have limited temporal depth. Here we present a Holocene reconstruction of fire regime, combining lacustrine charcoal analyses with past drought and fire-season length simulations to elucidate the mechanisms linking long-term fire regime and climatic changes. We decomposed fire regime into fire frequency (FF) and biomass burned (BB) and recombined these into a new index to assess fire size (FS) fluctuations. Results indicated that an earlier termination of the fire season, due to decreasing summer radiative insolation and increasing precipitation over the last 7.0 ky, induced a sharp decrease in FF and BB ca. 3.0 kyBP toward the present. In contrast, a progressive increase of FS was recorded, which is most likely related to a gradual increase in temperatures during the spring fire season. Continuing climatic warming could lead to a change in the fire regime toward larger spring wildfires in eastern boreal North America.

Policy vs. practice in sport and climate change: the perspectives of key actors in global sport and international development.

Despite widespread, scientifically supported recognition of the scope of the climate crisis, and policies in place connecting sport to sustainable development, there remain concerns that the environment and climate change are rarely acknowledged within SDP activity and that even when they are, it is unclear how such policies are implemented, and to what effect. This raises the question of how and why the climate crisis and the attendant relationships between sport and sustainable development are understood and operationalized (or not) by stakeholders within the SDP sector. In this paper, therefore, we explore various perspectives and tensions around the environment and climate crisis within the SDP sector. To do so, we draw on interviews with SDP policy-makers (primarily from the United Nations and the International Olympic Committee) and SDP practitioners living and working in the global South in order to gauge the place of the environment and climate change in their everyday SDP policy-making, programming and practices. Overall, the data shows that while SDP stakeholders recognize the urgency of the climate crisis, the need for action, and the policy agenda linking sport to sustainable development, significant barriers, tensions and politics are still in place that prevent consistent climate action within SDP. Policy commitments and coherence are therefore needed in order to make climate action a core feature of SDP activity and practice.

Tuning Surface, Phase, and Magnetization of Superparamagnetic Magnetite by Ionic Liquids: Single-Step Microwave-Assisted Synthesis.

Achieving colloidal and chemical stability in ferrofluids by surface modification requires multiple steps, including purification, ex situ modification steps, and operation at high temperatures. In this study, a single-step microwave-assisted methodology is developed for iron oxide nanoparticle (IONP) synthesis utilizing a series of imidazolium-based ionic liquids (ILs) with chloride, bis(trifluoromethylsulfonyl)imide, and pyrrolide anions as the reaction media, thus eliminating the use of volatile organics while enabling rapid synthesis at 80 °C as well as in situ surface functionalization. The characterized surface functionality, hydrodynamic particle size, magnetization, and colloidal stability of the IONPs demonstrate a strong dependence on the IL structure, ion coordination strength, reactivity, and hydrophilicity. The IONPs present primarily a magnetite (Fe3O4) phase with superparamagnetism with the highest saturation magnetization at 81 and 73 emu/g at 10 and 300 K, respectively. Depending on the IL coating, magnetization and exchange anisotropy decrease by 20 and 2-3 emu/g (at 35 wt % IL), respectively, but still represent the highest magnetization achieved for coated IONPs by a coprecipitation method. Further, the surface-functionalized superparamagnetic magnetite nanoparticles show good dispersibility and colloidal stability in water and dimethyl sulfoxide at 0.1 mg/mL concentration over the examined 3 month period. This study reports on the intermolecular and chemical interactions between the particle surface and the ILs under synthetic conditions as they relate to the magnetic and thermal properties of the resulting IONPs that are well suited for a variety of applications, including separation and catalysis.

[Peripheral arterial disease in black African diabetics: epidemioclinical, ultrasonographic profile and determining factors]. / Artériopathie oblitérante des membres inférieurs chez le sujet diabétique noir africain : profil épidémioclinique, ultrasonographique et facteurs déterminants.

BACKGROUND: Diabetes can lead to micro and macro-angiopathies. The peripheral arterial disease (PAD) is a serious and an incapacitating disease. It is still under-estimated and under-treated throughout the world, particularly in sub-Saharan Africa. Doppler ultrasound, and in particular ankle brachial index (ABI), can be used to detect it. The aim was to determine the prevalence of PAD to study the clinical and ultrasonographic aspects and to identify the determining factors. PATIENTS AND METHODS: This was a descriptive and analytical study over a period of 5 years, including a total of 782 diabetic patients hospitalised in the diabetology department of the CHU la Reference Nationale. RESULTS: Among the 782 patients, 166 (21.2%) had an ABI < 0.9 reflected the PAD and 72 (9.2%) had an ABI > 1.3, suggestive of mediacalcosis. PAD of the lower limb was mild in 102 patients (61.4%), moderate in (26.3%) and severe in (12.3%). The mean age of the arteritic patients was 56.4 ± 10.2 years. Male gender predominated (59.6%) with a sex ratio of 1.6. All patients had type 2 diabetes (100%). The mean duration of diabetes was 13 ± 5.9 years. The majority of our patients with arterial disease had diabetes for at least 10 years (54.2%). The other cardiovascular in this population were obesity (45.2%), followed by hypertension and dyslipidaemia (32.5%). Diabetes was unbalanced (HbA ≥7%) in the majority of cases (75.3%). Clinically, the majority of patients had a trophic disorder (68%). Asymptomatic patients accounted for 24.6% of cases and those with intermittent claudication for 7.4%. Duplex doppler of the lower limbs showed that all patients with PAD had atheromatous lesions. The distal location was predominantly in the tibial arteries (54.8%). The determinants of PAD in this diabetic population were hypertension (p = 0.01) and obesity (p = 0.01). CONCLUSION: In our series, PAD was often discovered at an advanced stage, with a non-negligible prevalence. The determining factors found were hypertension and obesity. Screening and control of major cardiovascular risk factors is a priority in the management of this disease.

Physiological and molecular mechanisms of the inhibitory effects of artemisinin on Microcystis aeruginosa and Chlorella pyrenoidosa.

Artemisinin, a novel plant allelochemical, has attracted attention for its potential selective inhibitory effects on algae, yet to be fully explored. This study compares the sensitivity and action targets of Microcystis aeruginosa (M. aeruginosa) and Chlorella pyrenoidosa (C. pyrenoidosa) to artemisinin algaecide (AMA), highlighting their differences. Results indicate that at high concentrations, AMA displaces the natural PQ at the QB binding site within M. aeruginosa photosynthetic system, impairing the D1 protein repair function. Furthermore, AMA disrupts electron transfer from reduced ferredoxin (Fd) to NADP+ by interfering with the iron-sulfur clusters in the ferredoxin-NADP+ reductases (FNR) domain of Fd. Moreover, significant reactive oxygen species (ROS) accumulation triggers oxidative stress and interrupts the tricarboxylic acid cycle, hindering energy acquisition. Notably, AMA suppresses arginine synthesis in M. aeruginosa, leading to reduced microcystins (MCs) release. Conversely, C. pyrenoidosa counters ROS accumulation via photosynthesis protection, antioxidant defenses, and by regulating intracellular osmotic pressure, accelerating damaged protein degradation, and effectively repairing DNA for cellular detoxification. Additionally, AMA stimulates the expression of DNA replication-related genes, facilitating cell proliferation. Our finding offer a unique approach for selectively eradicating cyanobacteria while preserving beneficial algae, and shed new light on employing eco-friendly algicides with high specificity.

Exogenous glutathione protected wheat seedling from high temperature and water deficit damages.

High temperatures (HT) and drought are two major factors restricting wheat growth in the early growth stages. This study investigated the role of glutathione (GSH) amendment (0.0, 0.5, 1.0, and 2.0 mM) to soil in mitigating the adverse effect of HT (33 °C, with 25 °C as a control), water regimes (60% of field capacity and control), and their combinations. HT decreased the length, project area, surface area, volume, and forks of the root, while drought had the reverse effect. Shoot length, leaf area, leaf relative water content, and shoot and root dry matter were significantly decreased by HT and drought, and their combined impact was more noticeable. GSH significantly promoted the root system, shoot growth, and leaf relative water content. The combined treatment reduced chlorophyll a, chlorophyll b, and total chlorophyll. However, 0.5 mM GSH raised chlorophyll a, chlorophyll b, and total chlorophyll by 28.6%, 41.4%, and 32.5%, respectively, relative to 0.0 mM GSH. At combined treatment, 0.5 mM GSH decreased malondialdehyde (MDA) by 29.5% and increased soluble protein content by 24.1%. GSH meaningfully enhanced the activity of superoxide dismutase, catalase, and ascorbate peroxide in different treatments. This study suggested that GSH could protect wheat seedlings from the adverse effects of HT and/or drought stresses.

Vegetation limits the impact of a warm climate on boreal wildfires.

Strategic introduction of less flammable broadleaf vegetation into landscapes was suggested as a management strategy for decreasing the risk of boreal wildfires projected under climatic change. However, the realization and strength of this offsetting effect in an actual environment remain to be demonstrated. Here we combined paleoecological data, global climate models and wildfire modelling to assess regional fire frequency (RegFF, i.e. the number of fires through time) in boreal forests as it relates to tree species composition and climate over millennial time-scales. Lacustrine charcoals from northern landscapes of eastern boreal Canada indicate that RegFF during the mid-Holocene (6000-3000 yr ago) was significantly higher than pre-industrial RegFF (AD c. 1750). In southern landscapes, RegFF was not significantly higher than the pre-industrial RegFF in spite of the declining drought severity. The modelling experiment indicates that the high fire risk brought about by a warmer and drier climate in the south during the mid-Holocene was offset by a higher broadleaf component. Our data highlight an important function for broadleaf vegetation in determining boreal RegFF in a warmer climate. We estimate that its feedback may be large enough to offset the projected climate change impacts on drought conditions.

The role of melatonin in plant growth and metabolism, and its interplay with nitric oxide and auxin in plants under different types of abiotic stress.

Melatonin is a pleiotropic signaling molecule that reduces the adverse effects of abiotic stresses, and enhances the growth and physiological function of many plant species. Several recent studies have demonstrated the pivotal role of melatonin in plant functions, specifically its regulation of crop growth and yield. However, a comprehensive understanding of melatonin, which regulates crop growth and yield under abiotic stress conditions, is not yet available. This review focuses on the progress of research on the biosynthesis, distribution, and metabolism of melatonin, and its multiple complex functions in plants and its role in the mechanisms of metabolism regulation in plants grown under abiotic stresses. In this review, we focused on the pivotal role of melatonin in the enhancement of plant growth and regulation of crop yield, and elucidated its interactions with nitric oxide (NO) and auxin (IAA, indole-3-acetic acid) when plants are grown under various abiotic stresses. The present review revealed that the endogenousapplication of melatonin to plants, and its interactions with NO and IAA, enhanced plant growth and yield under various abiotic stresses. The interaction of melatonin with NO regulated plant morphophysiological and biochemical activities, mediated by the G protein-coupled receptor and synthesis genes. The interaction of melatonin with IAA enhanced plant growth and physiological function by increasing the levels of IAA, synthesis, and polar transport. Our aim was to provide a comprehensive review of the performance of melatonin under various abiotic stresses, and, therefore, further explicate the mechanisms that plant hormones use to regulate plant growth and yield under abiotic stresses.