| 1. |
- Sarneel, Judith M., et al.
(författare)
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Reading tea leaves worldwide : decoupled drivers of initial litter decomposition mass-loss rate and stabilization
- 2024
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Ingår i: Ecology Letters. - : John Wiley & Sons. - 1461-023X .- 1461-0248. ; 27:5
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Tidskriftsartikel (refereegranskat)abstract
- The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models.
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| 2. |
- Björkman, Anne, 1981, et al.
(författare)
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Plant functional trait change across a warming tundra biome
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 562:7725, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
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| 3. |
- Cornelissen, Johannes H C, et al.
(författare)
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Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 4. |
- Eklof, B., et al.
(författare)
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The role of self-reported stressors in recovery from Exhaustion Disorder: a longitudinal study
- 2022
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Ingår i: Bmc Psychiatry. - : Springer Science and Business Media LLC. - 1471-244X. ; 22
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Tidskriftsartikel (refereegranskat)abstract
- Background Exhaustion disorder (ED) is a stress-induced disorder characterized by physical and mental symptoms of exhaustion that can be long-lasting. Although stress exposure is essential for the development of ED, little is known regarding the role of stressors in the maintenance of ED. The aim of the study was to investigate the role of work-related stressors, private-related stressors, and adverse childhood experiences in long-term recovery from ED. Methods A mixed methods design was used. The design was sequential, and data analysis was performed in two parts, where the first part consisted of qualitative analysis of patient records, and the second part consisted of statistical analysis of the data retrieved from the qualitative coding. Patient records from 150 patients with ED was analysed regarding work-related stressors, private-related stressors, and adverse childhood experiences. For each patient, two patient records were analysed, one from the time of diagnosis (baseline) and one from the follow-up clinical assessment, 7-12 years after diagnosis (follow-up). Out of the 150 patients, 51 individuals still fulfilled the diagnostic criteria for ED at follow-up (ED group) and 99 individuals no longer fulfilled the diagnostic criteria and were thus considered recovered (EDrec). Percentages in each group (ED and EDrec) reporting each stressor at baseline and follow-up were calculated as well as the differences in percentage points between the groups along with the 95% confidence intervals for the differences. Results At baseline, significantly more EDrec patients reported quantitative demands (73% EDrec, 53% ED) and managerial responsibilities (14% EDrec, 2% ED). Private-related stressors did not differ at baseline. At follow-up, significantly more ED patients reported managerial responsibilities (8 ED, 0% EDrec) and caregiver stress (child) (24% ED, 6% EDrec) and significantly more EDrec patients reported caregiver stress (parent) (6% EDrec, 0% ED). There were no differences regarding adverse childhood experiences. Conclusions The main conclusion is that neither adverse childhood experiences nor any of the stressors at baseline are associated with long-term ED. Ongoing stressors related to having responsibility for other people, such as managerial responsibilities or caring for a child with a chronic disease or psychiatric disorder, may be associated with long-term exhaustion.
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| 5. |
- Gulin, S., et al.
(författare)
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Is obsessive–compulsive personality disorder related to stress-related exhaustion?
- 2021
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Ingår i: Brain and Behavior. - : Wiley. - 2162-3279. ; 11:6
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Recovery from stress-related diagnoses can, in some cases, be long-lasting, and several different factors could be related to such a lengthy recovery. One plausible aspect is obsessive–compulsive personality disorder (OCPD), which has previously been seen to be related to stress-related mental health. Thus, the aim of this study was to investigate whether recovery from exhaustion disorder (ED) is associated with OCPD. Methods: This study includes data from 147 patients (78% women, mean age 52.4±9.8years) who have been treated for ED. Clinical assessment was performed 7–10years after first seeking care identifying patients with residual exhaustion. Symptoms of OCPD were concomitantly measured and several aspects of work- and private-related stress exposure. Results: The main result of this study is that patients with residual clinical ED report OCPD to a greater extent, compared with patients who no longer fulfill the clinical criteria for ED, 7–10years after seeking care. Patients with OCPD that have not recovered report “excessive devotion to work” to a higher degree than patients with OCPD that have recovered. Conclusion: The results indicate that factors related to OCPD may be of clinical importance for the patient's recovery from ED. However, prospective studies should be conducted and studies elucidating whether symptoms of exhaustion among patients with OCPD can be affected by therapeutic interventions. © 2021 The Authors. Brain and Behavior published by Wiley Periodicals LLC
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| 6. |
- Arvidsson, Elin, et al.
(författare)
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Exercise training and physiological responses to acute stress: study protocol and methodological considerations of a randomised controlled trial
- 2018
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Ingår i: BMJ Open Sport & Exercise Medicine. - : BMJ. - 2055-7647. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: This paper describes the protocol and methodological prerequisites for a randomised controlled exercise intervention. Selected baseline data from the study are also presented, demonstrating some methodological challenges related to exercise intervention trials. The aim of the trial was to study the effects of exercise training on physiological responses to acute psychosocial stress in untrained individuals. Methods: Individuals with a low level of physical activity were invited to participate in an exercise intervention lasting for 6 months. A total of 119 participants were included and went through a peak oxygen uptake test and a psychosocial stress test at baseline. Adrenocorticotropic hormone (ACTH) and cortisol were measured in connection to the stress test to identify the physiological response. Results: Almost 90% of the participants reported themselves as untrained, but results from the objectively measured oxygen uptake did not seem to correspond to the reported sedentary lifestyle. The primary outcome measures at baseline varied between individuals. The mean change from pre-test to peak value was 214% for ACTH and 94% for cortisol. Of these, 13 individuals did not respond in ACTH and/or and cortisol. Discussion: Supposedly untrained individuals seeking participation in an exercise intervention might not be as untrained as they report, a methodological consideration of importance when evaluating the effects of training. Another important consideration is related to the primary outcome measure, which should be measurable and possible to affect. Absence of reaction at baseline means that changes can only be detected as an increased reaction.
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| 7. |
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| 8. |
- Callaghan, Terry V., et al.
(författare)
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Responses to projected changes in climate and UV-B at the species level
- 2004
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Ingår i: Ambio: a Journal of Human Environment. - : Royal Swedish Academy of Sciences. - 0044-7447. ; 33:7, s. 418-435
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Forskningsöversikt (refereegranskat)abstract
- Environmental manipulation experiments showed that species respond individualistically to each environmental-change variable. The greatest responses of plants were generally to nutrient, particularly nitrogen, addition. Summer warming experiments showed that woody plant responses were dominant and that mosses and lichens became less abundant. Responses to warming were controlled by moisture availability and snow cover. Many invertebrates increased population growth in response to summer warming, as long as desiccation was not induced. CO2 and UV-B enrichment experiments showed that plant and animal responses were small. However, some microorganisms and species of fungi were sensitive to increased UV-B and some intensive mutagenic actions could, perhaps, lead to unexpected epidemic outbreaks. Tundra soil heating, CO 2 enrichment and amendment with mineral nutrients generally accelerated microbial activity. Algae are likely to dominate cyanobacteria in milder climates. Expected increases in winter freeze-thaw cycles leading to ice-crust formation are likely to severely reduce winter survival rate and disrupt the population dynamics of many terrestrial animals. A deeper snow cover is likely to restrict access to winter pastures by reindeer/caribou and their ability to flee from predators while any earlier onset of the snow-free period is likely to stimulate increased plant growth. Initial species responses to climate change might occur at the sub-species level: an Arctic plant or animal species with high genetic/racial diversity has proved an ability to adapt to different environmental conditions in the past and is likely to do so also in the future. Indigenous knowledge, air photographs, satellite images and monitoring show that changes in the distributions of some species are already occurring: Arctic vegetation is becoming more shrubby and more productive, there have been recent changes in the ranges of caribou, and "new" species of insects and birds previously associated with areas south of the treeline have been recorded. In contrast, almost all Arctic breeding bird species are declining and models predict further quite dramatic reductions of the populations of tundra birds due to warming. Species-climate response surface models predict potential future ranges of current Arctic species that are often markedly reduced and displaced northwards in response to warming. In contrast, invertebrates and microorganisms are very likely to quickly expand their ranges northwards into the Arctic.
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| 9. |
- Carlsson, S, et al.
(författare)
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Evidence for an adrenergic innervation of the adrenal cortical blood vessels in rats.
- 1993
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Ingår i: Acta physiologica Scandinavica. - 0001-6772. ; 149:1, s. 23-30
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the blood flow in the adrenal cortex of the rat. Relative changes in the adrenal cortical blood flow were continuously measured by Laser Doppler flowmetry in 33 chloralose-anaesthetized artificially ventilated rats during electrical stimulation (1 ms, 5 V) of the left great splanchnic nerve (LGSN), which conveys both pre- and post-ganglionic nerve fibres to the adrenal gland. Laser Doppler flux (LDF) was decreased and regional resistance (RR) was increased by augmenting nerve stimulation at increasingly higher frequencies (2, 4, 8, 20 and 40 Hz). The decrease in LDF, when compared to pre-drug stimulations at 4 Hz was partially or totally inhibited by the adrenergic blocking agents trimethaphan (TRIM), guanethidine (GUA) and alpha 1-blockade with prazosin (PRAZ). Furthermore, both the decrease in LDF and the increase in RR were either completely or partially blocked by stimulation at 40 Hz after TRIM-treatment and GUA-treatment. It is concluded that the adrenal cortex in the rat is innervated by post-ganglionic adrenergic nerve fibres, which are involved in the regulation of blood flow in the adrenal cortex.
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| 10. |
- Ellbin, S., et al.
(författare)
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Self-reported cognitive impairment and daily life functioning 7-12 years after seeking care for stress-related exhaustion
- 2021
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Ingår i: Scandinavian Journal of Psychology. - : Wiley. - 0036-5564 .- 1467-9450. ; 62:4, s. 484-492
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Tidskriftsartikel (refereegranskat)abstract
- The overall aim of this study was to investigate self-reported cognitive difficulties, daily life activities, and health/sleep factors in former patients with exhaustion disorder (ED) who still fulfill the clinical criteria for exhaustion 7-12 years after seeking care. The Sahlgrenska Self-reported Cognitive Impairment Questionnaire (SASCI-Q) was used to measure cognitive difficulties, daily life activities, and health/sleep factors. Three groups were compared: previous patients still judged to be clinically exhausted seven years or more after seeking care (n = 51); previous patients considered clinically recovered (n = 98); and healthy controls (n = 50). Patients who still fulfilled the diagnostic criteria for ED reported widespread problems related to cognition, fatigue, and daily life functioning compared to the clinically recovered group. Furthermore, despite no longer fulfilling the clinical criteria, the recovered patients still reported more problems related to cognitive functioning and fatigue compared to healthy controls. Thus, this group appeared intermediary between the non-recovered group and healthy controls regarding self-reported cognitive functioning. To conclude, ED may have considerable negative long-term effects, and it is possible that some of these residual symptoms, particularly the cognitive problems and persistent fatigue, are permanent in some patients. Preventive measures should be the primary focus for all stakeholders, since the consequences of stress-related mental health problems seem to be extensive and long-lasting.
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| 11. |
- Ellbin, S., et al.
(författare)
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"Who I Am Now, Is More Me." An Interview Study of Patients' Reflections 10 Years After Exhaustion Disorder
- 2021
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Ingår i: Frontiers in Psychology. - : Frontiers Media SA. - 1664-1078. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To achieve a deeper understanding of the patient's perception regarding individual aspects related to the development of exhaustion, hindering and supporting factors in the recovery process, and potential remaining consequences, 7-12 years after receiving an exhaustion disorder diagnosis.Participants and Methods: Twenty patients previously diagnosed with and treated for exhaustion disorder were interviewed 7-12 years after onset of the disease. The semi-structured interviews were transcribed verbatim and analyzed with inductive content analysis.Results: Three main themes with patterns of shared meaning resulted from the analysis: "it's about who I am," "becoming a more authentic me," and "the struggle never ends." The interviewees described rehabilitation from exhaustion disorder as the start of an important personal development toward a truer and more authentic self-image. They perceived this as an ongoing long-lasting process where learned behavior and thought patterns related to overcommitment and overcompliance needed to be re-evaluated. The results also convey long-term consequences such as cognitive difficulties and reduces energy, uncertainty about one's own health, and the need to prioritize among one's relationships.Conclusion: Patients with exhaustion disorder are still struggling with dysfunctional strategies and functional impairments such as cognitive problems which limit their lives, 10 years after receiving their exhaustion disorder diagnosis. While informants describe some positive consequences of ED, the results also emphasize the importance of acknowledging that the patients are embedded in systems of relationships, in working life as well as in family life. This needs to be considered, together with other aspects, when working toward prevention of stress-related mental health problems.
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| 12. |
- Gerber, M, et al.
(författare)
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Concerns regarding hair cortisol as a biomarker of chronic stress in exercise and sport science
- 2012
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Ingår i: Journal of Sports Science and Medicine. - 1303-2968. ; 11, s. 571-581
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Forskningsöversikt (refereegranskat)abstract
- Hair cortisol has the potential to fill the methodological void of long-term cortisol assessment while becoming a widely accepted measure in biopsychology. This review critically examines the applicability and relevance of hair cortisol measurement specifically within the field of exercise and sport science. Current measures of the HPA axis only cover a brief time period, whereas hair cortisol is a unique, non-invasive means to capture long-term cortisol secretion. Studies have shown that individuals who have elevated cortisol secretion (e.g. due to diseases associated with a disturbed activation of the HPA axis or exposure to stressful life events) reveal increased hair cortisol. By contrast, only weak correlations exist between hair cortisol and perceived stress, and the direction of the relationship between hair cortisol levels and mental disorders is unclear. Acute exercise, however, results in increased levels of cortisol that eventually is reflected in higher levels of cortisol in hair samples and studies have shown that exercise intensity is related to hair cortisol level. Thus, elevated hair cortisol levels found among regular exercisers are not necessarily pathological. Thus, one should practice caution when associating athletes’ elevated hair cortisol with poor mental health or disease. Hair cortisol analysis can contribute to a more complete understanding of how long-term cortisol elevation mediates stress-related effects on the health and performance of recreational exercisers and elite athletes. Nevertheless, it is crucial for exercise and sport scientists to consider whether their research questions can be adequately addressed, given that regular intense exercise results in substantially augmented hair cortisol levels.
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| 13. |
- Gerber, M., et al.
(författare)
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Objectively assessed physical activity is associated with increased hair cortisol content in young adults
- 2013
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Ingår i: Stress-the International Journal on the Biology of Stress. - : Informa UK Limited. - 1025-3890. ; 16:6, s. 593-599
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Tidskriftsartikel (refereegranskat)abstract
- Assessing long-term cortisol secretion presents difficulties when cortisol measurement is carried out by saliva, plasma and urine analyses. Hair cortisol has gained increased interest as an alternative biological marker. So far, one study has been published studying hair cortisol in endurance athletes, showing higher levels compared to controls. Using accelerometer data in the present study, we cross-sectionally explored the relationship between moderate physical activity (MPA) and vigorous physical activity (VPA) levels and hair cortisol concentrations after taking into account age, gender, and perceived stress. Hair specimens were collected from 46 university students (20 males, 26 females, M-age +/- SD = 21.2 +/- 1.87 years). Participants provided information about their socio-demographic background and levels of perceived stress. Accelerometer data were collected to assess physical activity. Cortisol concentrations were measured in the first 3-cm hair segment nearest to the scalp. MPA was not correlated with hair cortisol content (r = -0.08). A significant correlation was found between VPA and hair cortisol (r = 0.34, p < 0.05). A regression analysis revealed that participants with higher VPA had elevated hair cortisol concentrations even after taking into account age, gender and perceived stress (beta = 0.33, p < 0.05, Delta R-2 = 0.106). This is the first study showing that objectively assessed VPA is associated with increased hair cortisol levels in young adults. As VPA can be regarded as a physical stressor, it seems imperative that researchers consider participants' levels of VPA if they examine the relationship between stress exposure, hair cortisol and health.
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| 14. |
- Jonsdottir, Ingibjörg H, 1966, et al.
(författare)
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Cognitive impairment in patients with stress-related exhaustion
- 2013
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Ingår i: Stress-the International Journal on the Biology of Stress. - : Informa UK Limited. - 1025-3890 .- 1607-8888. ; 16:2, s. 181-190
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Tidskriftsartikel (refereegranskat)abstract
- Patients who seek medical care for stress-related mental health problems frequently report cognitive impairments as the most pronounced symptom. The purpose of the present study was to compare cognitive function in patients with stress-related exhaustion with that in healthy controls, using a comprehensive battery of cognitive tests. We also explored whether neuropsychological findings were related to severity of illness measured using the Shirom–Melamed burnout questionnaire and hospital anxiety and depression scale. Thirty-three patients (15 males) and 37 healthy controls (11 males), mean age 46 years [standard deviation (SD) 3.9] and 47 years (SD 4.3), respectively, were included in the final analysis. Five cognitive domains were assessed: (1) speed, attention and working memory, (2) learning and episodic memory, (3) executive functions, (4) visuospatial functions and (5) language. The most pronounced difference between patients and controls was seen on executive function, when tested with a multidimensional test, including aspects of speed, control and working memory. The patients also performed poorer on Digit span, measuring attention span and working memory as well as on learning and episodic memory, when measured as delayed recall and the difference between immediate and delayed recall. Delayed recall was the only test that was significantly related to severity of burnout symptoms among the patients. This could reflect poor cognitive sustainability in the patients with the highest burnout scores, as this particular test was the last one performed during the test session. This study clearly shows that cognitive impairment should be considered when evaluating and treating patients who seek medical care for stress-related exhaustion.
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| 15. |
- Jonsdottir, Ingibjörg H, 1966, et al.
(författare)
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Endocrine and immunological aspects of burnout: a narrative review
- 2019
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Ingår i: European Journal of Endocrinology. - : Oxford University Press (OUP). - 0804-4643 .- 1479-683X. ; 180:3
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Forskningsöversikt (refereegranskat)abstract
- Burnout has several different definitions, and attempts have been made to discriminate between burnout as a psychological construct and burnout as a clinical entity. A large body of research has focused on elucidating the biological link between stress exposure and burnout and/or finding a clinically usable biomarker for burnout. The objective of this narrative review is to summarize the main end ocrine and immune findings in relation to burnout. The literature has primarily focused on dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis. However, albeit the large body of studies, it cannot be concluded that clear effects are seen on HPA axis function in people with burnout. The HPA axis and anabolic acute reactivity to stress might be affected in clinical burnout. Plausible, effects of chronic stress might rather be seen when measuring responses to acute stress rather than resting state hormonal levels. Studies on other hormones, including thyroid hormones, prolactin and growth hormone in burnout subjects are inconclusive. It is important to note that this field is faced with many methodological challenges, one being the diurnal and pulsatile nature of many of the hormones of interest, including cortisol, which is not always considered. Another challenge is the heterogeneity regarding definitions and measurements of stress and burnout. Existing studies on burnout and immune function are heterogeneous regarding the results and no firm conclusion can be made if clinically relevant immune changes are present in burnout subjects. An overall conclusion is that existing research cannot confirm any homogenous reliable endocrinological or immunological changes related to burnout.
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| 16. |
- Jonsdottir, Ingibjörg H, 1966, et al.
(författare)
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Muscle contractions induce interleukin-6 mRNA production in rat skeletal muscles.
- 2000
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Ingår i: The Journal of physiology. - 0022-3751. ; 528 Pt 1, s. 157-63
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Tidskriftsartikel (refereegranskat)abstract
- 1. The present study explored the hypothesis that interleukin-6 (IL-6) might be locally produced in response to skeletal muscle contractions and whether the production might reflect the type of muscle contraction performed. Rats were anaesthetized and the calf muscles of one limb were stimulated electrically for concentric or eccentric contractions (4 x 10 contractions with 1 min of rest between the 4 series, 100 Hz). The contralateral muscles served as unstimulated controls. The mRNA levels for IL-6, the glucose transport protein GLUT-4 and beta-actin in the rat muscles (white and red gastrocnemius and soleus) were quantified by quantitative competitive RT-PCR. 2. The IL-6 mRNA level, measured 30 min after the stimulation, increased after both eccentric and concentric contractions and there were no significant differences in IL-6 mRNA levels between the different muscle fibre types. No significant increase in IL-6 mRNA level was seen in the unstimulated contralateral muscle fibres. 3. No increase in GLUT-4 mRNA level was detected, indicating that the increase in IL-6 mRNA level was not due to general changes in transcription. 4. We conclude that IL-6 is locally produced after muscle contraction, with no significant differences between different muscle fibre types. This local production of IL-6 is not due to general changes in transcription, since no changes in the level of GLUT-4 mRNA were found. The fact that increased IL-6 mRNA levels were seen after both concentric and eccentric contractions indicates that the production of IL-6 is not solely due to muscle damage, seen primarily after eccentric exercise.
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| 17. |
- Jonsdottir, Ingibjörg H, 1966, et al.
(författare)
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Stress och minnesfunktion
- 2007
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Ingår i: Socialmedicinsk tidskrift. ; årg 84:2
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Forskningsöversikt (refereegranskat)
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| 18. |
- Jonsdottir, Ingibjörg S., et al.
(författare)
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Large scale differentiation and population dynamics in tundra plants and vegetation
- 1999
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Ingår i: Ambio: a Journal of Human Environment. - 0044-7447. ; 28:3, s. 230-238
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Tidskriftsartikel (refereegranskat)abstract
- The inclusion of the botanical projects in the Swedish-Russian Tundra Ecology -94 expedition provided new information on the ecology of tundra plants. The vegetation patterns on different scales were documented, and interpreted as the result of a complex interaction with environmental factors. The distribution of fruticose lichens was studied, and it was shown that these lichens rely on different modes of asexual reproduction for their dispersal. Extreme old genet ages were demonstrated for species of Carex and there were similar strong indications for lichens. Populations of Carex were genetically diverse in spite of old ages and often low levels of flowering. Large differences between sites in flowering and vegetative ramet production (vegetative reproduction) in Carex reflected a asynchronous between-year population fluctuation, which was related to cyclic lemming populations and climate. Important gaps in our knowledge of the ecology of tundra plants are pointed out, some of which will hopefully be resolved during the tundra expedition, Tundra Northwest 1999.
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| 19. |
- Jägerbrand, Annika K, 1972-, et al.
(författare)
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Phenotypic variation at different spatial scales in relation to environment in two circumpolar bryophyte species
- 2005
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Ingår i: Lindbergia. - : ABE-IPS. - 0105-0761 .- 2001-5909. ; 30:3, s. 125-142
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Tidskriftsartikel (refereegranskat)abstract
- Morphology, physiology and biomass in two widespread bryophyte species, Hylocomium splendens and Racomitrium lanuginosum, were studied to examine the extent to which different species exhibit similar phenotypic variation patterns within and across regions. Analyses of nine morphological variables, chlorophyll content, nitrogen content, C/N ratio and biomass were conducted in samples from five sites in two geographically separated and climatically different regions, Iceland and northern Sweden. Both species exhibited large between-site variation in morphology, physiology and biomass, but within-site variation in morphology was substantially higher in Hylocomium splendens than Racomitrium lanuginosum. Morphological patterns were partly similar, partly different between the species, indicating that the two species respond morphologically to external factors on different scales. The lowest concentrations of chlorophyll and nitrogen were found at the same sites for both species, while the site of highest concentration was not the same. In Hylocomium splendens, chlorophyll content was positively correlated with biomass. Many of the observed relationships between morphological, physiological variables and biomass were species-specific. Our results demonstrate that the two bryophytes exhibit different phenotypic responses to environmental variation. Copyright © Lindbergia 2006.
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| 20. |
- Lett, Signe, et al.
(författare)
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Can bryophyte groups increase functional resolution in tundra ecosystems?
- 2022
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Ingår i: Arctic Science. - Ottawa : Canadian Science Publishing. - 2368-7460. ; 8:3, s. 609-637
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Tidskriftsartikel (refereegranskat)abstract
- The relative contribution of bryophytes to plant diversity, primary productivity, and ecosystem functioning increases towards colder climates. Bryophytes respond to environmental changes at the species level, but because bryophyte species are relatively difficult to identify, they are often lumped into one functional group. Consequently, bryophyte function remains poorly resolved. Here, we explore how higher resolution of bryophyte functional diversity can be encouraged and implemented in tundra ecological studies. We briefly review previous bryophyte functional classifications and the roles of bryophytes in tundra ecosystems and their susceptibility to environmental change. Based on shoot morphology and colony organization, we then propose twelve easily distinguishable bryophyte functional groups. To illustrate how bryophyte functional groups can help elucidate variation in bryophyte effects and responses, we compiled existing data on water holding capacity, a key bryophyte trait. Although plant functional groups can mask potentially high interspecific and intraspecific variability, we found better separation of bryophyte functional group means compared with previous grouping systems regarding water holding capacity. This suggests that our bryophyte functional groups truly represent variation in the functional roles of bryophytes in tundra ecosystems. Lastly, we provide recommendations to improve the monitoring of bryophyte community changes in tundra study sites.
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| 21. |
- Lindén, Elin, et al.
(författare)
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Circum-Arctic distribution of chemical anti-herbivore compounds suggests biome-wide trade-off in defence strategies in Arctic shrubs
- 2022
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Ingår i: Ecography. - : John Wiley & Sons. - 0906-7590 .- 1600-0587. ; :11
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Tidskriftsartikel (refereegranskat)abstract
- Spatial variation in plant chemical defence towards herbivores can help us understand variation in herbivore top–down control of shrubs in the Arctic and possibly also shrub responses to global warming. Less defended, non-resinous shrubs could be more influenced by herbivores than more defended, resinous shrubs. However, sparse field measurements limit our current understanding of how much of the circum-Arctic variation in defence compounds is explained by taxa or defence functional groups (resinous/non-resinous). We measured circum-Arctic chemical defence and leaf digestibility in resinous (Betula glandulosa, B. nana ssp. exilis) and non-resinous (B. nana ssp. nana, B. pumila) shrub birches to see how they vary among and within taxa and functional groups. Using liquid chromatography–mass spectrometry (LC–MS) metabolomic analyses and in vitro leaf digestibility via incubation in cattle rumen fluid, we analysed defence composition and leaf digestibility in 128 samples from 44 tundra locations.We found biogeographical patterns in anti-herbivore defence where mean leaf triterpene concentrations and twig resin gland density were greater in resinous taxa and mean concentrations of condensing tannins were greater in non-resinous taxa. This indicates a biome-wide trade-off between triterpene- or tannin-dominated defences. However, we also found variations in chemical defence composition and resin gland density both within and among functional groups (resinous/non-resinous) and taxa, suggesting these categorisations only partly predict chemical herbivore defence. Complex tannins were the only defence compounds negatively related to in vitro digestibility, identifying this previously neglected tannin group as having a potential key role in birch anti-herbivore defence.We conclude that circum-Arctic variation in birch anti-herbivore defence can be partly derived from biogeographical distributions of birch taxa, although our detailed mapping of plant defence provides more information on this variation and can be used for better predictions of herbivore effects on Arctic vegetation.
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| 22. |
- Lindgren, Åsa, 1973-
(författare)
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Effects of herbivory on arctic and alpine vegetation
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions. In this thesis, I investigate interactions among plants and herbivory effects on plant community composition and plant functional traits in three different regions: Swedish Lapland, Beringia (USA/Russia) and Finnmark (Norway). Reindeer grazing was found to be extensive in southern Lapland and had limited effects on plant community composition and seedling germination. However, reindeer presence was found to influence plant functional traits, particularly in the subalpine birch forest. Tall herbs were lower and had lower SLA when reindeer were present, while small herbs showed an opposite pattern. The contrasting effects on the two herb groups are probably explained by a competitive release for small herbs when the tall herbs are suppressed by reindeer. Rodents had the largest relative impact on plant community composition in southern Lapland and this is consistent with the study from Finnmark, where rodents heavily affected dwarf shrubs on predator-free islands. With no predators present, vole densities increased profoundly and almost depleted some dwarf shrub species. These results support the idea that small mammals in arctic and alpine tundra are controlled by predators (i.e. top-down). However, a decrease in the nutritional quality in a sedge after defoliation gives support for the idea that small mammals are regulated by plant quality (i.e. bottom-up). In Beringia, small and large herbivores differed in the relation to plant community composition, since large herbivores were related to species richness and small herbivores were related to plant abundance. Plant functional traits were related only to large herbivores and standing crop of vascular plants.
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| 23. |
- Manni, Luigi, 1962, et al.
(författare)
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Effect of exercise on ovarian morphology and expression of nerve growth factor and alpha(1)- and beta(2)-adrenergic receptors in rats with steroid-induced polycystic ovaries
- 2005
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Ingår i: J Neuroendocrinol. ; 17:12, s. 846-58
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Tidskriftsartikel (refereegranskat)abstract
- Oestadiol valerate (EV)-induced polycystic ovaries (PCO) in rats cause anovulation and cystic ovarian morphology. Denervation of ovarian sympathetic nerves restores ovulatory disruption. In the present study, we determined whether 5 weeks of voluntary exercise influence ovarian morphology and the expression of sympathetic markers in the EV-induced PCO rat model. The effect of exercise on (i) ovarian morphology; (ii) mRNA and protein expression of nerve growth factor (NGF); and (iii) mRNA and number of ovarian-expressing cells for the NGF receptor (p75 neurotrophin receptor) and the alpha(1a)-, alpha(1b)-, alpha(1d)- and beta(2)-adrenergic receptors (ARs) in rats with EV-induced PCO was evaluated. PCO was induced by a single i.m. injection of EV, and controls were injected with oil alone in adult cycling rats. The rats were divided into four groups: (i) control (oil); (ii) exercise group (oil + exercise); (iii) a PCO group (EV); and (iv) a PCO exercise group (EV + exercise). The exercise and PCO exercise groups ran voluntarily for 5 weeks in computer-monitored wheels placed in the cages where they were housed. The results obtained indicated that ovarian morphology was almost normalised in the PCO exercise group; NGF mRNA and protein concentrations were normalised in the PCO exercise group; high numbers of NGF receptor expressing cells in PCO ovaries were lowered by exercise; and the number of immunopositive cells of the different AR subtypes were all reduced after exercise in the PCO group, except for the alpha(1b)- and beta(2)-AR whereas the mRNA levels were unaffected, indicating transcriptional regulation. In conclusion, our data indicate a beneficial effect of regular exercise, as a modulator of ovarian sympathetic innervation, in the prevention and treatment of human PCOS.
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| 24. |
- Naylor, Andrew Stuart, 1977, et al.
(författare)
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Extended voluntary running inhibits exercise-induced adult hippocampal progenitor proliferation in the spontaneously hypertensive rat.
- 2005
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 93:5, s. 2406-14
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Tidskriftsartikel (refereegranskat)abstract
- Previous work has shown that voluntary running increases cell proliferation and neurogenesis in the dentate gyrus of the adult hippocampus. Here we report that long-term running for 24 days results in a down-regulation of hippocampal progenitor proliferation to one-half the level of nonrunning controls compared with a fivefold increase in progenitor proliferation seen after 9 days of voluntary running (short-term running). The negative effects seen on proliferation after 24 days of running were prevented by restricting daily running distances (by 30-50%) during 24 days. Long-term running for 24 days increases the response of the hypothalamic-pituitary-adrenal axis, with an increase in adrenal gland weight and increased plasma corticosterone levels, as well as decreased thymus weight, indicating a stress response as a possible mediator of decreased progenitor proliferation. Furthermore, the negative effects seen on the observed stress response after 24 days of running were prevented by restricting daily running distance. Short-term running did not alter these stress parameters compared with nonrunning controls. However, it increased phosphorylated cyclic AMP response element binding protein (pCREB) in the dentate gyrus, an increase that was not seen in nonrunning controls or after 24 days of running. Taken together, these data suggest that voluntary running does not always enhance proliferation and that the decrease in progenitor proliferation seen in long-term running is possibly mediated by mechanisms involving a stress response in the animal. However, a moderate level of long-term running was able to prevent the negative stress-related changes seen in unrestricted long-term running.
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| 25. |
- Persson, Anders I., 1973, et al.
(författare)
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Differential regulation of hippocampal progenitor proliferation by opioid receptor antagonists in running and non-running spontaneously hypertensive rats.
- 2004
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Ingår i: The European journal of neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 19:7, s. 1847-55
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Tidskriftsartikel (refereegranskat)abstract
- Voluntary running in mice and forced treadmill running in rats have been shown to increase the amount of proliferating cells in the hippocampus. Little is known as yet about the mechanisms involved in these processes. It is well known that the endogenous opioid system is affected during running and other forms of physical exercise. In this study, we evaluated the involvement of the endogenous opioids in the regulation of hippocampal proliferation in non-running and voluntary running rats. Nine days of wheel running was compared with non-running in spontaneously hypertensive rats (SHR), a rat strain known to run voluntarily. On the last 2 days of the experimental period all rats received two daily injections of the opioid receptor antagonists naltrexone or naltrindole together with injections of bromodeoxyuridine to label dividing cells. Brain sections from the running rats showed approximately a five-fold increase in newly generated cells in the hippocampus, and this increase was partly reduced by naltrexone but not by naltrindole. By contrast, both naltrexone and naltrindole increased hippocampal proliferation in non-running rats. In non-running rats the administration of naltrexone decreased corticosterone levels and adrenal gland weights, whereas no significant effects on these parameters could be detected for naltrindole. However, adrenal gland weights were increased in naltrexone- but not in naltrindole-administered running rats. In addition, in voluntary running rats there was a three-fold increase in the hippocampal levels of Met-enkephalin-Arg-Phe compared with non-runners, indicating an increase in opioid activity in the hippocampus during running. These data suggest an involvement of endogenous opioids in the regulation of hippocampal proliferation in non-running rats, probably through hypothalamic-pituitary-adrenal axis modulation. During voluntary running in SHR naltrexone altered hippocampal proliferation via as yet unknown mechanisms.
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| 26. |
- Prevéy, Janet S., et al.
(författare)
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The tundra phenology database: more than two decades of tundra phenology responses to climate change
- 2022
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Ingår i: Arctic Science. - : Canadian Science Publishing. - 2368-7460. ; 8:3, s. 1026-1039
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Tidskriftsartikel (refereegranskat)abstract
- Observations of changes in phenology have provided some of the strongest signals of the effects of climate change on terrestrial ecosystems. The International Tundra Experiment (ITEX), initiated in the early 1990s, established a common protocol to measure plant phenology in tundra study areas across the globe. Today, this valuable collec-tion of phenology measurements depicts the responses of plants at the colder extremes of our planet to experimental and ambient changes in temperature over the past decades. The database contains 150 434 phenology observations of 278 plant species taken at 28 study areas for periods of 1–26 years. Here we describe the full data set to increase the visibility and use of these data in global analyses and to invite phenology data contributions from underrepresented tundra locations. Portions of this tundra phenology database have been used in three recent syntheses, some data sets are expanded, others are from entirely new study areas, and the entirety of these data are now available at the Polar Data Catalogue (https://doi.org/10.21963/13215).
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| 27. |
- Simrén, Joel, 1996, et al.
(författare)
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Establishment of reference values for plasma neurofilament light based on healthy individuals aged 5-90 years
- 2022
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Ingår i: Brain Communications. - : Oxford University Press (OUP). - 2632-1297. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- The recent development of assays that accurately quantify neurofilament light, a neuronal cytoskeleton protein, in plasma has generated a vast literature supporting that it is a sensitive, dynamic, and robust biomarker of neuroaxonal damage. As a result, efforts are now made to introduce plasma neurofilament light into clinical routine practice, making it an easily accessible complement to its cerebrospinal fluid counterpart. An increasing literature supports the use of plasma neurofilament light in differentiating neurodegenerative diseases from their non-neurodegenerative mimics and suggests it is a valuable biomarker for the evaluation of the effect of putative disease-modifying treatments (e.g. in multiple sclerosis). More contexts of use will likely emerge over the coming years. However, to assist clinical interpretation of laboratory test values, it is crucial to establish normal reference intervals. In this study, we sought to derive reliable cut-offs by pooling quantified plasma neurofilament light in neurologically healthy participants (5-90 years) from eight cohorts. A strong relationship between age and plasma neurofilament light prompted us to define the following age-partitioned reference limits (upper 95(th) percentile in each age category): 5-17 years = 7 pg/mL; 18-50 years = 10 pg/mL; 51-60 years = 15 pg/mL; 61-70 years = 20 pg/mL; 70 + years = 35 pg/mL. The established reference limits across the lifespan will aid the introduction of plasma neurofilament light into clinical routine, and thereby contribute to diagnostics and disease-monitoring in neurological practice. Simren et al. report age-stratified cut-offs for plasma neurofilament light, based on a large material of healthy individuals across the ages 5-90 years. The findings will assist clinical implementation of plasma neurofilament light in clinical routine, by simplifying interpretation of concentrations across the lifespan as neurofilament light increases with age.
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| 28. |
- Tuomi, Maria, et al.
(författare)
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Stomping in silence : Conceptualizing trampling effects on soils in polar tundra
- 2021
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 35:2, s. 306-317
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Forskningsöversikt (refereegranskat)abstract
- Ungulate trampling modifies soils and interlinked ecosystem functions across biomes. Until today, most research has focused on temperate ecosystems and mineral soils while trampling effects on cold and organic matter-rich tundra soils remain largely unknown. We aimed to develop a general model of trampling effects on soil structure, biota, microclimate and biogeochemical processes, with a particular focus on polar tundra soils. To reach this goal, we reviewed literature about the effects of trampling and physical disturbances on soils across biomes and used this to discuss the knowns and unknowns of trampling effects on tundra soils. We identified the following four pathways through which trampling affects soils: (a) soil compaction; (b) reductions in soil fauna and fungi; (c) rapid losses in vegetation biomass and cover; and (d) longer term shifts in vegetation community composition. We found that, in polar tundra, soil responses to trampling pathways 1 and 3 could be characterized by nonlinear dynamics and tundra-specific context dependencies that we formulated into testable hypotheses. In conclusion, trampling may affect tundra soil significantly but many direct, interacting and cascading responses remain unknown. We call for research to advance the understanding of trampling effects on soils to support informed efforts to manage and predict the functioning of tundra systems under global changes. A free Plain Language Summary can be found within the Supporting Information of this article.
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| 29. |
- Wasof, Safaa, et al.
(författare)
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Disjunct populations of European vascular plant species keep the same climatic niches
- 2015
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 24:12, s. 1401-1412
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Tidskriftsartikel (refereegranskat)abstract
- Aim Previous research on how climatic niches vary across species ranges has focused on a limited number of species, mostly invasive, and has not, to date, been very conclusive. Here we assess the degree of niche conservatism between distant populations of native alpine plant species that have been separated for thousands of years. Location European Alps and Fennoscandia. Methods Of the studied pool of 888 terrestrial vascular plant species occurring in both the Alps and Fennoscandia, we used two complementary approaches to test and quantify climatic-niche shifts for 31 species having strictly disjunct populations and 358 species having either a contiguous or a patchy distribution with distant populations. First, we used species distribution modelling to test for a region effect on each species' climatic niche. Second, we quantified niche overlap and shifts in niche width (i.e. ecological amplitude) and position (i.e. ecological optimum) within a bi-dimensional climatic space. Results Only one species (3%) of the 31 species with strictly disjunct populations and 58 species (16%) of the 358 species with distant populations showed a region effect on their climatic niche. Niche overlap was higher for species with strictly disjunct populations than for species with distant populations and highest for arctic-alpine species. Climatic niches were, on average, wider and located towards warmer and wetter conditions in the Alps. Main conclusion Climatic niches seem to be generally conserved between populations that are separated between the Alps and Fennoscandia and have probably been so for 10,000-15,000 years. Therefore, the basic assumption of species distribution models that a species' climatic niche is constant in space and time-at least on time scales 104 years or less-seems to be largely valid for arctic-alpine plants.
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