| 1. |
- Limpens, J., et al.
(författare)
-
Glasshouse vs field experiments : do they yield ecologically similar results for assessing N impacts on peat mosses?
- 2012
-
Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 195:2, s. 408-418
-
Tidskriftsartikel (refereegranskat)abstract
- Peat bogs have accumulated more atmospheric carbon (C) than any other terrestrial ecosystem today. Most of this C is associated with peat moss (Sphagnum) litter. Atmospheric nitrogen (N) deposition can decrease Sphagnum production, compromising the C sequestration capacity of peat bogs. The mechanisms underlying the reduced production are uncertain, necessitating multifactorial experiments. We investigated whether glasshouse experiments are reliable proxies for field experiments for assessing interactions between N deposition and environment as controls on Sphagnum N concentration and production. We performed a meta-analysis over 115 glasshouse experiments and 107 field experiments. We found that glasshouse and field experiments gave similar qualitative and quantitative estimates of changes in Sphagnum N concentration in response to N application. However, glasshouse-based estimates of changes in production even qualitative assessments diverged from field experiments owing to a stronger N effect on production response in absence of vascular plants in the glasshouse, and a weaker N effect on production response in presence of vascular plants compared to field experiments. Thus, although we need glasshouse experiments to study how interacting environmental factors affect the response of Sphagnum to increased N deposition, we need field experiments to properly quantify these effects.
|
|
| 2. |
- Limpens, J., et al.
(författare)
-
Climatic modifiers of the response to nitrogen deposition in peat-forming Sphagnum mosses : a meta-analysis
- 2011
-
Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 191:2, s. 496-507
-
Tidskriftsartikel (refereegranskat)abstract
- Peatlands in the northern hemisphere have accumulated more atmospheric carbon (C) during the Holocene than any other terrestrial ecosystem, making peatlands long-term C sinks of global importance. Projected increases in nitrogen (N) deposition and temperature make future accumulation rates uncertain. Here, we assessed the impact of N deposition on peatland C sequestration potential by investigating the effects of experimental N addition on Sphagnum moss. We employed meta-regressions to the results of 107 field experiments, accounting for sampling dependence in the data. We found that high N loading (comprising N application rate, experiment duration, background N deposition) depressed Sphagnum production relative to untreated controls. The interactive effects of presence of competitive vascular plants and high tissue N concentrations indicated intensified biotic interactions and altered nutrient stochiometry as mechanisms underlying the detrimental N effects. Importantly, a higher summer temperature (mean for July) and increased annual precipitation intensified the negative effects of N. The temperature effect was comparable to an experimental application of almost 4 g N m(-2) yr(-1) for each 1 degrees C increase. Our results indicate that current rates of N deposition in a warmer environment will strongly inhibit C sequestration by Sphagnum-dominated vegetation.
|
|
| 3. |
- Stokowska, Anna, et al.
(författare)
-
Complement C3a treatment accelerates recovery after stroke via modulation of astrocyte reactivity and cortical connectivity
- 2023
-
Ingår i: Journal of Clinical Investigation. - : American Society for Clinical Investigation. - 0021-9738 .- 1558-8238. ; 133:10
-
Tidskriftsartikel (refereegranskat)abstract
- Despite advances in acute care, ischemic stroke remains a major cause of long-term disability. Approaches targeting both neuronal and glial responses are needed to enhance recovery and improve long-term outcome. The complement C3a receptor (C3aR) is a regulator of inflammation with roles in neurodevelopment, neural plasticity, and neurodegeneration. Using mice lacking C3aR (C3aR-/-) and mice overexpressing C3a in the brain, we uncovered 2 opposing effects of C3aR signaling on functional recovery after ischemic stroke: inhibition in the acute phase and facilitation in the later phase. Peri-infarct astrocyte reactivity was increased and density of microglia reduced in C3aR-/- mice; C3a overexpression led to the opposite effects. Pharmacological treatment of wild-type mice with intranasal C3a starting 7 days after stroke accelerated recovery of motor function and attenuated astrocyte reactivity without enhancing microgliosis. C3a treatment stimulated global white matter reorganization, increased peri-infarct structural connectivity, and upregulated Igf1 and Thbs4 in the peri-infarct cortex. Thus, C3a treatment from day 7 after stroke exerts positive effects on astrocytes and neuronal connectivity while avoiding the deleterious consequences of C3aR signaling during the acute phase. Intranasal administration of C3aR agonists within a convenient time window holds translational promise to improve outcome after ischemic stroke.
|
|
| 4. |
- Tobias, J., et al.
(författare)
-
A New Strategy Toward B Cell-Based Cancer Vaccines by Active Immunization With Mimotopes of Immune Checkpoint Inhibitors
- 2020
-
Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- Therapeutic monoclonal antibodies (mAbs), targeting tumor antigens, or immune checkpoints, have demonstrated a remarkable anti-tumor effect against various malignancies. However, high costs for mono- or combination therapies, associated with adverse effects or possible development of resistance in some patients, warrant further development and modification to gain more flexibility for this immunotherapy approach. An attractive alternative to passive immunization with therapeutic antibodies might be active immunization with mimotopes (B-cell peptides) representing the mAbs' binding epitopes, to activate the patient's own anti-tumor immune response following immunization. Here, we identified and examined the feasibility of inducing anti-tumor effectsin vivofollowing active immunization with a mimotope of the immune checkpoint programmed cell death 1 (PD1), alone or in combination with a Her-2/neu B-cell peptide vaccine. Overlapping peptides spanning the extracellular domains of human PD1 (hPD1) were used to identify hPD1-derived mimotopes, using the therapeutic mAb Nivolumab as a proof of concept. Additionally, forin vivoevaluation in a tumor mouse model, a mouse PD1 (mPD1)-derived mimotope was identified using an anti-mPD1 mAb with mPD1/mPDL-1 blocking capacity. The identified mimotopes were characterized byin vitroassays, including a reporter cell-based assay, and their anti-tumor effects were evaluated in a syngeneic tumor mouse model stably expressing human Her-2/neu. The identified PD1-derived mimotopes were shown to significantly block the mAbs' capacity in inhibiting the respective PD1/PD-L1 interactions. A significant reduction in tumor growthin vivowas observed following active immunization with the mPD1-derived mimotope, associated with a significant reduction in proliferation and increased apoptotic rates in the tumors. Particularly, combined vaccination with the mPD1-derived mimotope and a multiple B-cell epitope Her-2/neu vaccine potentiated the vaccine's anti-tumor effect. Our results suggest active immunization with mimotopes of immune checkpoint inhibitors either as monotherapy or as combination therapy with tumor-specific vaccines, as a new strategy for cancer treatment.
|
|
| 5. |
- Akgün, J., et al.
(författare)
-
The role of alveolar epithelial type II-Like cells in uptake of structurally different antigens and in polarisation of local immune responses
- 2015
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:4
-
Tidskriftsartikel (refereegranskat)abstract
- Background Our previous studies on intranasal tolerance induction demonstrated reduction of allergic responses with different allergen constructs. The underlying mechanisms varied depending on their conformation or size. Objective The aim of the present study was to compare the uptake of two structurally different allergen molecules within the respiratory tract following intranasal application. Methods The three-dimensional Bet v 1 (Bv1-Protein) and the T cell epitope peptide of Bet v 1 (Bv1- Peptide) were labelled with 5,6-Carboxyfluorescein (FAM) and their uptake was investigated in lung cells and cells of the nasal associated lymphoid tissue from naive and sensitised BALB/c mice. Phenotypic characterisation of FAM+ lung cells after antigen incubation in vitro and after intranasal application was performed by flow cytometry. Impact of Bv1-Protein and Bv1-Peptide on cytokine profiles and gene expression in vivo or in an alveolar epithelial type II (ATII) cell line were assessed in mono- and co-cultures with monocytes using ELISA and quantitative real-time PCR. Results Both antigens were taken up preferably by ATII-like cells (ATII-LCs) in naive mice, and by macrophages in sensitised mice. After intranasal application, Bv1-Peptide was taken up faster and more efficiently than Bv1-Protein. In vivo and in vitro experiments revealed that Bv1-Protein induced the transcription of thymic stromal lymphopoietin mRNA while Bv1- Peptide induced the transcription of IL-10 and MCP1 mRNA in ATII-LCs. Conclusion and Clinical Relevance Both tested antigens were taken up by ATII-LCs under steady state conditions and induced different polarisation of the immune responses. These data may have an important impact for the generation of novel and more effective prophylactic or therapeutic tools targeting the respiratory mucosa. Copyright: © 2015 Akgün et al.
|
|
| 6. |
- Dixon, Christopher J, et al.
(författare)
-
Reciprocal Pleistocene origin and postglacial range formation of an allopolyploid and its sympatric ancestors (Androsace adfinis group, Primulaceae)
- 2009
-
Ingår i: Molecular Phylogenetics and Evolution. - : Academic Press. - 1055-7903 .- 1095-9513. ; 50:1, s. 74-83
-
Tidskriftsartikel (refereegranskat)abstract
- The biogeographic history of polyploids and their lower-ploid ancestors is an important feature to achieve a better understanding of polyploid evolution. This is exemplified here using the ecologically congruent members of the Androsace adfinis group (Primulaceae) endemic to the southwestern European Alps. Employing relative genome size, AFLP fingerprint and chloroplast sequence haplotype data, we show that Androsace brigantiaca is a recent (probably no more than 0.2 million years) allopolyploid derivative of the geographically close A adfinis and A puberula, which formed reciprocally in a comparatively restricted area in the southern Southwestern Alps. Bayesian admixture analysis-also of artificial additive AFLP profiles-shows that the nuclear genome of A. brigantiaca is significantly biased towards the puberula-genome irrespective of maternal parentage. Nevertheless, there is no evidence for genetic interaction (hybridization, introgression) of A brigantiaca with either of its ancestors, including the widely sympatric A. puberula. Sympatry might be facilitated by ecological displacement on a local scale or might be a transitory phase on the way to competitive replacement via, for instance, polyploid superiority.
|
|
| 7. |
- Rammig, A., et al.
(författare)
-
Coincidences of climate extremes and anomalous vegetation responses : comparing tree ring patterns to simulated productivity
- 2015
-
Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 12:2, s. 373-385
-
Tidskriftsartikel (refereegranskat)abstract
- Climate extremes can trigger exceptional responses in terrestrial ecosystems, for instance by altering growth or mortality rates. Such effects are often manifested in reductions in net primary productivity (NPP). Investigating a Europe-wide network of annual radial tree growth records confirms this pattern: we find that 28% of tree ring width (TRW) indices are below two standard deviations in years in which extremely low precipitation, high temperatures or the combination of both noticeably affect tree growth. Based on these findings, we investigate possibilities for detecting climate-driven patterns in long-term TRW data to evaluate state-of-the-art dynamic vegetation models such as the Lund-Potsdam-Jena dynamic global vegetation model for managed land (LPJmL). The major problem in this context is that LPJmL simulates NPP but not explicitly the radial tree growth, and we need to develop a generic method to allow for a comparison between simulated and observed response patterns. We propose an analysis scheme that quantifies the coincidence rate of climate extremes with some biotic responses (here TRW or simulated NPP). We find a relative reduction of 34% in simulated NPP during precipitation, temperature and combined extremes. This reduction is comparable to the TRW response patterns, but the model responds much more sensitively to drought stress. We identify 10 extreme years during the 20th century during which both model and measurements indicate high coincidence rates across Europe. However, we detect substantial regional differences in simulated and observed responses to climatic extreme events. One explanation for this discrepancy could be the tendency of tree ring data to originate from climatically stressed sites. The difference between model and observed data is amplified by the fact that dynamic vegetation models are designed to simulate mean ecosystem responses on landscape or regional scales. We find that both simulation results and measurements display carry-over effects from climate anomalies during the previous year. We conclude that radial tree growth chronologies provide a suitable basis for generic model benchmarks. The broad application of coincidence analysis in generic model benchmarks along with an increased availability of representative long-term measurements and improved process-based models will refine projections of the long-term carbon balance in terrestrial ecosystems.
|
|
| 8. |
- Raymond, Christopher, et al.
(författare)
-
Inclusive conservation and the Post-2020 Global Biodiversity Framework : Tensions and prospects
- 2022
-
Ingår i: One Earth. - : Elsevier BV. - 2590-3330 .- 2590-3322. ; 5:3, s. 252-264
-
Tidskriftsartikel (refereegranskat)abstract
- The draft Post-2020 Global Biodiversity Framework commits to achievement of equity and justice outcomes and represents a “relational turn” in how we understand inclusive conservation. Although “inclusivity” is drawn on as a means to engage diverse stakeholders, widening the framing of inclusivity can create new tensions with regard to how to manage protected areas. We first offer a set of tensions that emerge in the light of the relational turn in biodiversity conservation. Drawing on global case examples applying multiple methods of inclusive conservation, we then demonstrate that, by actively engaging in the interdependent phases of recognizing hybridity, enabling conditions for reflexivity and partnership building, tensions can not only be acknowledged but softened and, in some cases, reframed when managing for biodiversity, equity, and justice goals. The results can improve stakeholder engagement in protected area management, ultimately supporting better implementation of global biodiversity targets.
|
|
| 9. |
- Wagner, A., et al.
(författare)
-
Prime-Boost Vaccination with Toxoplasma Lysate Antigen, but Not with a Mixture of Recombinant Protein Antigens, Leads to Reduction of Brain Cyst Formation in BALB/c Mice
- 2015
-
Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 10:5
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction Infection with the ubiquitous parasite Toxoplasma gondii is a threat for immunocompromised patients and pregnant women and effective immune-prophylaxis is still lacking. Here we tested a mixture of recombinant T. gondii antigens expressed in different developmental stages, i.e., SAG1, MAG1 and GRA7 (SMG), and a lysate derived from T. gondii tachyzoites (TLA) for prophylactic vaccination against cyst formation. Both vaccine formulations were applied systemically followed by an oral TLA-booster in BALB/c mice. Systemic priming with SMG and oral TLA-booster did not show significant induction of protective immune responses. In contrast, systemic priming and oral booster with TLA induced higher levels of Toxoplasma-specific IgG, IgG1 and IgG2a in sera as well as high levels of Toxoplasma-specific IgG1 in small intestines. Furthermore, high levels of Toxoplasma-specific Th1-, Th17-and Th2-associated cytokines were only detected in restimulated splenocytes of TLA-vaccinated mice. Importantly, in mice orally infected with T. gondii oocysts, only TLA-vaccination and booster reduced brain cysts. Furthermore, sera from these mice reduced tachyzoites invasion of Vero cells in vitro, indicating that antibodies may play a critical role for protection against Toxoplasma infection. Additionally, supernatants from splenocyte cultures of TLA-vaccinated mice containing high levels of IFN-gamma lead to substantial production of nitric oxide (NO) after incubation with macrophages in vitro. Since NO is involved in the control of parasite growth, the high levels of IFN-gamma induced by vaccination with TLA may contribute to the protection against T. gondii. In conclusion, our data indicate that prime-boost approach with TLA, but not with the mixture of recombinant antigens SMG, induces effective humoral and cellular Toxoplasma-specific responses and leads to significant reduction of cerebral cysts, thereby presenting a viable strategy for further vaccine development against T. gondii infection.
|
|
| 10. |
- Donges, Jonathan F., et al.
(författare)
-
Earth system modeling with endogenous and dynamic human societies : the copan
- 2020
-
Ingår i: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 11:2, s. 395-413
-
Tidskriftsartikel (refereegranskat)abstract
- Analysis of Earth system dynamics in the Anthropocene requires explicitly taking into account the increasing magnitude of processes operating in human societies, their cultures, economies and technosphere and their growing feedback entanglement with those in the physical, chemical and biological systems of the planet. However, current state-of-the-art Earth system models do not represent dynamic human societies and their feedback interactions with the biogeophysical Earth system and macroeconomic integrated assessment models typically do so only with limited scope. This paper (i) proposes design principles for constructing world-Earth models (WEMs) for Earth system analysis of the Anthropocene, i.e., models of social (world)-ecological (Earth) coevolution on up to planetary scales, and (ii) presents the copan:CORE open simulation modeling framework for developing, composing and analyzing such WEMs based on the proposed principles. The framework provides a modular structure to flexibly construct and study WEMs. These can contain biophysical (e.g., carbon cycle dynamics), socio-metabolic or economic (e.g., economic growth or energy system changes), and sociocultural processes (e.g., voting on climate policies or changing social norms) and their feedback interactions, and they are based on elementary entity types, e.g., grid cells and social systems. Thereby, copan:CORE enables the epistemic flexibility needed for contributions towards Earth system analysis of the Anthropocene given the large diversity of competing theories and methodologies used for describing socio-metabolic or economic and sociocultural processes in the Earth system by various fields and schools of thought. To illustrate the capabilities of the framework, we present an exemplary and highly stylized WEM implemented in copan:CORE that illustrates how endogenizing sociocultural processes and feedbacks such as voting on climate policies based on socially learned environmental awareness could fundamentally change macroscopic model outcomes.
|
|
| 11. |
- Granath, Gustaf, et al.
(författare)
-
Physiological responses to nitrogen and sulphur addition and raised temperature in Sphagnum balticum
- 2009
-
Ingår i: Oecologia. - New York : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 161:3, s. 481-490
-
Tidskriftsartikel (refereegranskat)abstract
- Sphagnum, the main genus which forms boreal peat, is strongly affected by N and S deposition and raised temperature, but the physiological mechanisms behind the responses are largely unknown. We measured maximum photosynthetic rate (NPmax), maximum efficiency of photosystem II [variable fluorescence (F v)/maximum fluorescence yield (F m)] and concentrations of N, C, chlorophyll and carotenoids as responses to N and S addition and increased temperature in Sphagnum balticum (a widespread species in the northern peatlands) in a 12-year factorial experiment. NPmax did not differ between control (0.2 g N m−2 year−1) and high N (3.0 g N m−2 year−1), but was higher in the mid N treatment (1.5 g N m−2 year−1). N, C, carotenoids and chlorophyll concentration increased in shoot apices after N addition. F v/F m did not differ between N treatments. Increased temperature (+3.6°C) had a small negative effect on N concentration, but had no significant effect on NPmax or F v/F m. Addition of 2 g S m−2 year−1 showed a weak negative effect on NPmax and F v/F m. Our results suggest a unimodal response of NPmax to N addition and tissue N concentration in S. balticum, with an optimum N concentration for photosynthetic rate of ~13 mg N g−1. In conclusion, high S deposition may reduce photosynthetic capacity in Sphagnum, but the negative effects may be relaxed under high N availability. We suggest that previously reported negative effects on Sphagnum productivity under high N deposition are not related to negative effects on the photosynthetic apparatus, but differences in optimum N concentration among Sphagnum species may affect their competitive ability under different N deposition regimes.
|
|
| 12. |
|
|
| 13. |
- Neimert-Andersson, T., et al.
(författare)
-
Carbohydrate-based particles reduce allergic inflammation in a mouse model for cat allergy
- 2008
-
Ingår i: Allergy. European Journal of Allergy and Clinical Immunology. - : John Wiley & Sons. - 0105-4538 .- 1398-9995. ; 63:5, s. 518-526
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Allergen-specific immunotherapy (ASIT) is the only treatment of allergic disease that gives long-lasting relief of symptoms. However, concerns for safety and efficiency have highlighted the need for improvement of the therapy. We have previously suggested carbohydrate-based particles (CBPs) as a novel adjuvant and allergen carrier for ASIT. Our aim of this study was to evaluate the therapeutic potential of CBPs in ASIT, employing a mouse model for cat allergy. Methods: BALB/c mice were subcutaneously immunized with the recombinant (r) cat allergen Fel d 1 followed by intranasal challenge with cat dander extract (CDE). The sensitized mice were therapeutically treated with rFel d 1 covalently coupled to CBPs (CBP-rFel d 1). Airway hyper-reactivity (AHR), infiltration of leucocytes in bronchoalveolar lavage (BAL) fluid, allergen-specific serum immunoglobulin levels and in vitro splenocyte responses were evaluated. Results: Mice treated with CBP-rFel d 1 showed reduced features of allergic inflammation. They responded with (i) significantly decreased AHR and infiltration of eosinophils in BAL fluid after CDE challenge, (ii) the serum level of rFel d 1-specific IgE was reduced and the level of IgG(2)a was more pronounced after CBP-rFel d 1 treatment, and (iii) there was also a tendency of decreased allergen-specific cellular response. Conclusions: Carbohydrate-based particles are effective tools as adjuvant and allergen carriers for use in ASIT and constitutes a promising strategy to improve allergy treatment.
|
|
| 14. |
- Otto, Ilona M., et al.
(författare)
-
Human agency in the Anthropocene
- 2020
-
Ingår i: Ecological Economics. - : Elsevier BV. - 0921-8009 .- 1873-6106. ; 167
-
Tidskriftsartikel (refereegranskat)abstract
- The human species has been recognized as a new force that has pushed the Earth's system into a new geological epoch referred to as the Anthropocene. This human influence was not conscious, however, but an unintended effect of the consumption of fossil-fuels over the last 150 years. Do we, humans, have the agency to deliberately influence the fate of our species and the planet we inhabit? The rational choice paradigm that dominated social sciences in the 20th Century, and has heavily influenced the conceptualization of human societies in global human-environmental system modelling in the early 21st Century, suggests a very limited view of human agency. Humans seen as rational agents, coordinated through market forces, have only a very weak influence on the system rules. In this article we explore alternative concepts of human agency that emphasize its collective and strategic dimensions as well as we ask how human agency is distributed within the society. We also explore the concept of social structure as a manifestation of, and a constraint on, human agency. We discuss the implications for conceptualization of human agency in integrated assessment modelling efforts.
|
|
| 15. |
- Wagner, A., et al.
(författare)
-
Paediatricians require more information before they routinely co-administer the meningococcal B vaccine with routine infant vaccines
- 2015
-
Ingår i: Acta Paediatrica. - : Wiley. - 0803-5253. ; 104:10
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: The four-component meningococcal serogroup B (4CMenB) vaccine was licensed by the European Medicines Agency in 2013. We evaluated current practice regarding multiple vaccines and the attitudes of paediatricians towards the 4CMenB before it became available in Austria in 2014. Methods: We sent 1624 Austrian paediatricians an email invitation to participate in our nationwide web-based survey and 231 responded. Results: Most participants regarded the 4CMenB vaccine as a long-needed and necessary tool against meningococcal B disease. However, most participants would not co-administer this vaccine with other routine infant vaccines. The survey showed that 58.9% of paediatricians already co-administered the hexavalent vaccine with the pneumococcal conjugate vaccine, but most of them would not add a third vaccine at the same visit. This was mainly due to lack of experience with the vaccine and also because they assumed that parents would not consent. Importantly, paediatricians said they wanted an explicit recommendation in the Austrian Immunisation Plan on the timing of the 4CMenB vaccine before they would confidently and routinely use it for infants. Conclusion: Paediatricians required more information for themselves and for parents before routinely co-administering the 4CMenB vaccine. They also requested a national recommendation on its timing.
|
|
| 16. |
- Wiedermann, Magdalena M, et al.
(författare)
-
Can small-scale experiments predict ecosystem responses? : An example from peatlands
- 2009
-
Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 118:3, s. 449-457
-
Tidskriftsartikel (refereegranskat)abstract
- Oligotrophic, Sphagnum-dominated peatlands have been regarded as long-term stable ecosystems that function as carbon sinks. As a result of environmental perturbations, particularly anthropogenic N deposition, this view is now increasingly questioned. We examined whether small-scale field experiments can predict the direction and magnitude of ecosystem responses to increased N supply. We, therefore, compared data from a 10-year field experiment (involving deposition of 2, 15 and 30 kg N ha-1 year-1) with data from a gradient associated with increased N deposition (2, 8 and 12 kg N ha -1 year-1). We chose to compare: (1) the physiological response of Sphagnum balticum, measured in the form of N accumulation as free amino acids (NAA); and (2) changes in the total Sphagnum cover, the cover of S. balticum, and vascular plant cover. In all cases we found a highly significant correlation between the two data sets. We attribute the high correspondence between the two data sets to the key function of the dominant group of organisms, the Sphagna, that monopolize N availability and control the water balance, creating an environment hostile to vascular plants. Thus the key role of Sphagna as ecosystem engineers seems to supersede the role of other, scale-dependent processes. We also conclude that NAA is a sensitive indicator that can be used to signal the slow and gradual shift from Sphagnum to vascular plant dominance.
|
|
| 17. |
|
|
| 18. |
- Wiedermann, Magdalena M, et al.
(författare)
-
Ecophysiological adjustment of two Sphagnum species in response to anthropogenic nitrogen deposition
- 2009
-
Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 181:1, s. 208-217
-
Tidskriftsartikel (refereegranskat)abstract
- Here, it was investigated whether Sphagnum species have adjusted their nitrogen (N) uptake in response to the anthropogenic N deposition that has drastically altered N-limited ecosystems, including peatlands, worldwide.A lawn species, Sphagnum balticum, and a hummock species, Sphagnum fuscum, were collected from three peatlands along a gradient of N deposition (2, 8 and 12 kg N ha(-1) yr(-1)) The mosses were subjected to solutions containing a mixture of four N forms. In each solution one of these N forms was labeled with N-15 (namely (NH4+)-N-15 (NO3-)-N-15 and the amino acids [N-15] alanine (Ala) and [N-15] glutamic acid (Glu)).It was found that for both species most of the N taken up was from, followed by Ala, Glu, and very small amounts from. At the highest N deposition site N uptake was reduced, but this did not prevent N accumulation as free amino acids in the Sphagnum tissues.The reduced N uptake may have been genetically selected for under the relatively short period with elevated N exposure from anthropogenic sources, or may have been the result of plasticity in the Sphagnum physiological response. The negligible Sphagnum NO3- uptake may make any NO3- deposited readily available to co- occurring vascular plants.
|
|
| 19. |
- Wiedermann, Magdalena M., et al.
(författare)
-
Global change shifts vegetation and plant-parasite interactions in a boreal mire
- 2007
-
Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 88:2, s. 454-464
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to detect vegetation change and to examine trophic interactions in a Sphagnum-dominated mire in response to raised temperature and nitrogen (N) addition. A long-term global-change experiment was established in 1995, with monthly additions of N ( 30 kg.ha(-1).yr(-1)) and sulfur (20 kg.ha(-1)yr(-1)) during the vegetation period. Mean air temperature was raised by 3.6 degrees C with warming chambers. Vegetation responses were negligible for all treatments for the first four years, and no sulfur effect was seen during the course of the experiment. However, after eight years of continuous treatments, the closed Sphagnum carpet was drastically reduced from 100% in 1995 down to 41%, averaged over all N-treated plots. Over the same period, total vascular plant cover ( of the graminoid Eriophorum vaginatum and the two dwarf-shrubs Andromeda polifolia and Vaccinium oxycoccos) increased from 24% to an average of 70% in the N plots. Nitrogen addition caused leaf N concentrations to rise in the two dwarf-shrubs, while for E. vaginatum, leaf N remained unchanged, indicating that the graminoid to a larger extent than the dwarf-shrubs allocated supplemented N to growth. Concurrent with foliar N accumulation of the two dwarf-shrubs, we observed increased disease incidences caused by parasitic fungi, with three species out of 16 showing a significant increase. Warming caused a significant decrease in occurrence of three parasitic fungal species. In general, decreased disease incidences were found in temperature treatments for A. polifolia and in plots without N addition for V. oxycoccos. The study demonstrates that both bryophytes and vascular plants at boreal mires, only receiving background levels of nitrogen of about 2 kg.ha(-1)yr(-1), exhibit a time lag of more than five years in response to nitrogen and temperature rise, emphasizing the need for long-term experiments. Moreover, it shows that trophic interactions are likely to differ markedly in response to climate change and increased N deposition, and that these interactions might play an important role in controlling the change in mire vegetation composition, with implications for both carbon sequestration and methane emission.
|
|
| 20. |
- Wiedermann, M., et al.
(författare)
-
Node-weighted interacting network measures improve the representation of real-world complex systems
- 2013
-
Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 102:2, s. 28007-
-
Tidskriftsartikel (refereegranskat)abstract
- Many real-world complex systems are adequately represented by networks of interacting or interdependent networks. Additionally, it is often reasonable to take into account node weights such as surface area in climate networks, volume in brain networks, or economic capacity in trade networks to reflect the varying size or importance of subsystems. Combining both ideas, we derive a novel class of statistical measures for analysing the structure of networks of interacting networks with heterogeneous node weights. Using a prototypical spatial network model, we show that the newly introduced node-weighted interacting network measures provide an improved representation of the underlying system's properties as compared to their unweighted analogues. We apply our method to study the complex network structure of cross-boundary trade between European Union (EU) and non-EU countries finding that it provides relevant information on trade balance and economic robustness.
|
|
| 21. |
- Winkelmann, Ricarda, et al.
(författare)
-
Social tipping processes towards climate action : A conceptual framework
- 2022
-
Ingår i: Ecological Economics. - : Elsevier BV. - 0921-8009 .- 1873-6106. ; 192
-
Tidskriftsartikel (refereegranskat)abstract
- Societal transformations are necessary to address critical global challenges, such as mitigation of anthropogenic climate change and reaching UN sustainable development goals. Recently, social tipping processes have received increased attention, as they present a form of social change whereby a small change can shift a sensitive social system into a qualitatively different state due to strongly self-amplifying (mathematically positive) feedback mechanisms. Social tipping processes with respect to technological and energy systems, political mobilization, financial markets and sociocultural norms and behaviors have been suggested as potential key drivers towards climate action. Drawing from expert insights and comprehensive literature review, we develop a framework to identify and characterize social tipping processes critical to facilitating rapid social transformations. We find that social tipping processes are distinguishable from those of already more widely studied climate and ecological tipping dynamics. In particular, we identify human agency, social-institutional network structures, different spatial and temporal scales and increased complexity as key distinctive features underlying social tipping processes. Building on these characteristics, we propose a formal definition for social tipping processes and filtering criteria for those processes that could be decisive for future trajectories towards climate action. We illustrate this definition with the European political system as an example of potential social tipping processes, highlighting the prospective role of the FridaysForFuture movement. Accordingly, this conceptual framework for social tipping processes can be utilized to illuminate mechanisms for necessary transformative climate change mitigation policies and actions.
|
|
| 22. |
- Zemp, D. C., et al.
(författare)
-
Node-weighted measures for complex networks with directed and weighted edges for studying continental moisture recycling
- 2014
-
Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 107:5, s. 58005-
-
Tidskriftsartikel (refereegranskat)abstract
- In many real-world networks nodes represent agents or objects of different sizes or importance. However, the size of the nodes is rarely taken into account in network analysis, possibly inducing bias in network measures and confusion in their interpretation. Recently, a new axiomatic scheme of node-weighted network measures has been suggested for networks with undirected and unweighted edges. However, many real-world systems are best represented by complex networks which have directed and/or weighted edges. Here, we extend this approach and suggest new versions of the degree and the clustering coefficient associated to network motifs for networks with directed and/or weighted edges and weighted nodes. We apply these measures to a spatially embedded network model and a real-world moisture recycling network. We show that these measures improve the representation of the underlying systems' structure and are of general use for studying any type of complex network.
|
|
