| 1. |
- Gaillard, Marie-José, et al.
(författare)
-
Causes of Regional Change : Land Cover
- 2015
-
Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - Cham : Springer. - 9783319160054 - 9783319160061 ; , s. 453-477
-
Bokkapitel (refereegranskat)abstract
- Anthropogenic land-cover change (ALCC) is one of the few climate forcings for which the net direction of the climate response over the last two centuries is still not known. The uncertainty is due to the often counteracting temperature responses to the many biogeophysical effects and to the biogeochemical versus biogeophysical effects. Palaeoecological studies show that the major transformation of the landscape by anthropogenic activities in the southern zone of the Baltic Sea basin occurred between 6000 and 3000/2500 cal year BP. The only modelling study of the biogeophysical effects of past ALCCs on regional climate in north-western Europe suggests that deforestation between 6000 and 200 cal year BP may have caused significant change in winter and summer temperature. There is no indication that deforestation in the Baltic Sea area since AD 1850 would have been a major cause of the recent climate warming in the region through a positive biogeochemical feedback. Several model studies suggest that boreal reforestation might not be an effective climate warming mitigation tool as it might lead to increased warming through biogeophysical processes.
|
|
| 2. |
- Rasmussen, Magnus, et al.
(författare)
-
From contamination to infective endocarditis—a population-based retrospective study of Corynebacterium isolated from blood cultures
- 2020
-
Ingår i: European Journal of Clinical Microbiology and Infectious Diseases. - : Springer Science and Business Media LLC. - 0934-9723 .- 1435-4373. ; 39:1, s. 113-119
-
Tidskriftsartikel (refereegranskat)abstract
- Corynebacterium is a genus that can contaminate blood cultures and also cause severe infections like infective endocarditis (IE). Our purpose was to investigate microbiological and clinical features associated with contamination and true infection. A retrospective population-based study of Corynebacterium bacteremia 2012–2017 in southern Sweden was performed. Corynebacterium isolates were species determined using a matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Patient were, from the medical records, classified as having true infection or contamination caused by Corynebacterium through a scheme considering both bacteriological and clinical features and the groups were compared. Three hundred thirty-nine episodes of bacteremia with Corynebacterium were identified in 335 patients of which 30 (8.8%) episodes were classified as true infection. Thirteen patients with true bacteremia had only one positive blood culture. Infections were typically community acquired and affected mostly older males with comorbidities. The focus of infection was most often unknown, and in-hospital mortality was around 10% in both the groups with true infection and contamination. Corynebacterium jeikeium and Corynebacterium striatum were significantly overrepresented in the group with true infection, whereas Corynebacterium afermentans was significantly more common in the contamination group. Eight episodes of IE were identified, all of which in patients with heart valve prosthesis. Six of the IE cases affected the aortic valve and six of seven patients were male. The species of Corynebacterium in blood cultures can help to determine if a finding represent true infection or contamination. The finding of a single blood culture with Corynebacterium does not exclude true infection such as IE.
|
|
| 3. |
- Smith, Benjamin, et al.
(författare)
-
A model of the coupled dynamics of climate, vegetation and terrestrial ecosystem biogeochemistry for regional applications
- 2011
-
Ingår i: Tellus. Series A: Dynamic Meteorology and Oceanography. - : Stockholm University Press. - 1600-0870. ; 63A:1, s. 87-106
-
Tidskriftsartikel (refereegranskat)abstract
- Regional climate models (RCMs) primarily represent physical components of the climate system, omitting vegetation dynamics, ecosystem biogeochemistry and their associated feedbacks. To account for such feedbacks, we implemented a novel plant individual-based vegetation dynamics-ecosystem biogeochemistry scheme within the RCA3 RCM. Variations in leaf area index (LAI) of seven plant functional type (PFTs) in response to physical forcing and evolving vegetation state feed back to climate via adjustments in surface energy fluxes and surface properties. In an ERA-40-driven simulation over Europe, the model reproduces the recent past climate with comparable accuracy to the standard RCM. Large-scale patterns of LAI, net primary production and vegetation composition were comparable with observations, although winter LAI was systematically overestimated compared to satellite estimates. Analysis of the ERA-40 simulation and an A1B climate-change simulation revealed considerable covariation among dynamic variables of the physical climate and vegetation. At a Mediterranean site, periodic soil water limitation led to fluctuations in leaf cover and a likely positive feedback to near-surface temperature. At an alpine site, rising temperatures led to forest advance onto tundra areas, reducing albedo and effecting a likely positive feedback on temperature. Climate-vegetation coupling was less pronounced but still apparent at intermediate temperate and boreal sites.
|
|
| 4. |
- Wramneby, Anna, et al.
(författare)
-
Hot spots of vegetation-climate feedbacks under future greenhouse forcing in Europe
- 2010
-
Ingår i: Journal of Geophysical Research. - 2156-2202. ; 115:D21119, s. 1-12
-
Tidskriftsartikel (refereegranskat)abstract
- We performed simulations of future biophysical vegetation-climate feedbacks with a regional Earth System Model, RCA-GUESS, interactively coupling a regional climate model and a process-based model of vegetation dynamics and biogeochemistry. Simulated variations in leaf area index and in the relative coverage of evergreen forest, deciduous forest, and open land vegetation in response to simulated climate influence atmospheric state via variations in albedo, surface roughness, and the partitioning of the land-atmosphere heat flux into latent and sensible components. The model was applied on a similar to 50 x 50 km grid over Europe under a future climate scenario. Three potential "hot spots" of vegetation-climate feedbacks could be identified. In the Scandinavian Mountains, reduced albedo resulting from the snow-masking effect of forest expansion enhanced the winter warming trend. In central Europe, the stimulation of photosynthesis and plant growth by "CO2 fertilization" mitigated warming, through a negative evapotranspiration feedback associated with increased vegetation cover and leaf area index. In southern Europe, increased summer dryness restricted plant growth and survival, causing a positive warming feedback through reduced evapotranspiration. Our results suggest that vegetation-climate feedbacks over the European study area will be rather modest compared to the radiative forcing of increased global CO2 concentrations but may modify warming projections locally, regionally, and seasonally, compared with results from traditional "off-line" regional climate models lacking a representation of the relevant feedback mechanisms.
|
|
| 5. |
|
|
| 6. |
- Wramneby, Anna, et al.
(författare)
-
Parameter uncertainties in the modelling of vegetation dynamics — effects on tree community structure and ecosystem functioning in European forest biomes
- 2008
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 216, s. 277-290
-
Tidskriftsartikel (refereegranskat)abstract
- Dynamic vegetation models are useful tools for analysing terrestrial ecosystem processes and their interactions with climate through variations in carbon and water exchange. Long-term changes in structure and composition (vegetation dynamics) caused by altered competitive strength between plant functional types (PFTs) are attracting increasing attention as controls on ecosystem functioning and potential feedbacks to climate. Imperfect process knowledge and limited observational data restrict the possibility to parameterise these processes adequately and potentially contribute to uncertainty in model results. This study addresses uncertainty among parameters scaling vegetation dynamic processes in a process-based ecosystem model, LPJ-GUESS, designed for regional-scale studies, with the objective to assess the extent to which this uncertainty propagates to additional uncertainty in the tree community structure (in terms of the tree functional types present and their relative abundance) and thus to ecosystem functioning (carbon storage and fluxes). The results clearly indicate that the uncertainties in parameterisation can lead to a shift in competitive balance, most strikingly among deciduous tree PFTs, with dominance of either shade-tolerant or shade-intolerant PFTs being possible, depending on the choice of plausible parameter values. Despite this uncertainty, our results indicate that the resulting effect on ecosystem functioning is low. Since the vegetation dynamics in LPJ-GUESS are representative for the more complex Earth system models now being applied within ecosystem and climate research, we assume that our findings will be of general relevance. We suggest that, in terms of carbon storage and fluxes, the heavier parameterisation requirement of the processes involved does not widen the overall uncertainty in model predictions. (C) 2008 Elsevier B.V. All rights reserved.
|
|
| 7. |
- Wramneby, Anna
(författare)
-
The Role of Vegetation-Climate Feedbacks in Regional Earth System Dynamics
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The hypothesis of this thesis is that climate models should take structural vegetation changes that operate on interannual to centennial time scales into account in order to simulate climate change in a more realistic manner. To evaluate this hypothesis, a regional Earth System Model (ESM) has been developed, validated and applied over Europe. The model has enabled the identification of a number of regions where vegetation dynamics affect future climate, lending support to the hypothesis. The model, RCA-GUESS, combines the regional climate model RCA with the dynamic vegetation model LPJ-GUESS. RCA is continuously updated with dynamic albedo, leaf area index (LAI) and vegetated tile fractions for broadleaved and needleleaved forest and open land vegetation. These factors influence the radiation balance and the ratio between sensible and latent heat surface fluxes. The results suggest that it is important to account for vegetation-climate feedbacks in the analysis both of changes in mean climate and climate variability. Regarding mean climate, results indicate an accentuated temperature increase (winter, spring) in the Scandinavian Mountains as a result of tree line advance in response to warming. An increased forest fraction masks snow-covered areas, with a resulting albedo reduction. A significant temperature increase (summer) in southern Europe leads to a decline in LAI, resulting in a reduced evapotranspiration that reinforces the temperature increase. A less pronounced temperature rise in central Europe was attributed to the positive effect of "CO2 fertilization" on the simulated vegetation: a favourable effect on LAI positively impacts evapotranspiration, which dampens the temperature increase. The albedo effect in the Scandinavian Mountains dampens temperature variability, since variations in snow characteristics lose their significance beneath an increased forest fraction. In southern and central Europe, variability is strengthened, due to greater variations in temperature and water availability around bioclimatic limits governing establishment, growth and survival. Traditional climate models consider fast energy exchanges between the land surface and the atmosphere, utilizing a prescribed vegetation cover over time. A new generation of global ESMs are now including vegetation and the carbon cycling of the biosphere as interactive components. Such models have demonstrated that vegetation changes can result in strong feedbacks impacting on global climate. The course spatial resolution in global ESMs may, however, miss significant regional feedbacks. Regional ESMs are therefore important tools to consider for more accurate scenarios of future climate change when the focus is on the regional scale of, for example, Sweden or Europe.
|
|
