| 1. |
- Cornelissen, Johannes H C, et al.
(författare)
-
Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
-
Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
-
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.
|
|
| 2. |
- Asplund, Disa, 1985-, et al.
(författare)
-
Does uncertainty make cost-benefit analyses pointless?
- 2016
-
Ingår i: Transportation Research Part A. - Stockholm : Elsevier BV. - 0965-8564 .- 1879-2375. ; 92, s. 195-205
-
Tidskriftsartikel (refereegranskat)abstract
- Cost-benefit analysis (CBA) is widely used in public decision making on infrastructure investments. However, the demand forecasts, cost estimates, benefit valuations and effect assessments that are conducted as part of CBAs are all subject to various degrees of uncertainty. The question is to what extent CBAs, given such uncertainties, are still useful as a way to prioritize between infrastructure investments, or put differently, how robust the policy conclusions of CBA are with respect to uncertainties. Using simulations based on real data on national infrastructure plans in Sweden and Norway, we study how investment selection and total realized benefits change when decisions are based on CBA assessments subject to several different types of uncertainty.Our results indicate that realized benefits and investment selection are surprisingly insensitive to all studied types of uncertainty, even for high levels of uncertainty. The two types of uncertainty that affect results the most are uncertainties about investment cost and transport demand. Provided that decisions are based on CBA outcomes, reducing uncertainty is still worthwhile, however, because of the huge sums at stake. Even moderate reductions of uncertainties about unit values, investment costs, future demand and project effects may increase the realized benefits infrastructure investment plans by tens or hundreds of million euros. We conclude that, despite the many types of uncertainties, CBA is able to fairly consistently separate the wheat from the chaff and hence contribute to substantially improved infrastructure decisions.
|
|
| 3. |
- Lundkvist, Sven-Olof, et al.
(författare)
-
Tillståndsmätningar av vägmarkeringars funktion år 2012 : Trafikverket Region Mitt
- 2013
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I föreliggande notat redovisas tillståndsmätningar av vägmarkeringars funktion. Det är en av sex notat som redovisar mätningar i olika delar av landet. Mätningarna har utförts med det mobila systemet Road Marking Tester, vars två centrala komponenter är en reflektometer av typ LTL-M och en optokator för mätning av vägmarkerings makrotextur. Från retroreflexionen och texturen har våta vägmarkeringar skattats på vägar med ÅDT > 4000 fordon. Sammanlagt har mätningar gjorts på 292 cirka 10 km långa objekt, vilka hade valts slumpmässigt, jämnt fördelade över hela landet. I varje objekt på tvåfältsväg mättes de tre delobjekten höger och vänster kantlinje samt mittlinjen.
|
|
| 4. |
- Jägerbrand, Annika K, 1972-, et al.
(författare)
-
Plant community responses to 5 years of simulated climate change in meadow and heath ecosystems at a subarctic-alpine site
- 2009
-
Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 161:3, s. 601-610
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change was simulated by increasing temperature and nutrient availability in an alpine landscape. We conducted a field experiment of BACI-design (before/after control/impact) running for five seasons in two alpine communities (heath and meadow) with the factors temperature (increase of ca. 1.5-3.0°C) and nutrients (5 g N, 5 g P per m 2) in a fully factorial design in northern Swedish Lapland. The response variables were abundances of plant species and functional types. Plant community responses to the experimental perturbations were investigated, and the responses of plant functional types were examined in comparison to responses at the species level. Nutrient addition, exclusively and in combination with enhanced temperature increase, exerted the most pronounced responses at the species-specific and community levels. The main responses to nutrient addition were increases in graminoids and forbs, whereas deciduous shrubs, evergreen shrubs, bryophytes, and lichens decreased. The two plant communities of heath or meadow showed different vegetation responses to the environmental treatments despite the fact that both communities were located on the same subarctic-alpine site. Furthermore, we showed that the abundance of forbs increased in response to the combined treatment of temperature and nutrient addition in the meadow plant community. Within a single-plant functional type, most species responded similarly to the enhanced treatments although there were exceptions, particularly in the moss and lichen functional types. Plant community structure showed BACI responses in that vegetation dominance relationships in the existing plant functional types changed to varying degrees in all plots, including control plots. Betula nana and lichens increased in the temperature-increased enhancements and in control plots in the heath plant community during the treatment period. The increases in control plots were probably a response to the observed warming during the treatment period in the region. © Springer-Verlag 2009.
|
|
| 5. |
|
|
| 6. |
- Jägerbrand, Annika K, 1972-, et al.
(författare)
-
Effects of neighboring vascular plants on the abundance of bryophytes in different vegetation types
- 2012
-
Ingår i: Polar Science. - Oxford : Elsevier BV. - 1873-9652 .- 1876-4428. ; 6:2, s. 200-208
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the climate change, vegetation of tundra ecosystems is predicted to shift toward shrub and tree dominance, and this change may influence bryophytes. To estimate how changes in growing environment and the dominance of vascular plants influence bryophyte abundance, we compared the relationship of occurrence of bryophytes among other plant types in a five-year experiment of warming (T), fertilization (F) and T + F in two vegetation types, heath and meadow, in a subarctic–alpine ecosystem. We compared individual leaf area among shrub species to confirm that deciduous shrubs might cause severe shading effect. Effects of neighboring functional types on the performance of Hylocomium splendens was also analyzed. Results show that F and T + F treatments significantly influenced bryophyte abundance negatively. Under natural conditions, bryophytes in the heath site were negatively related to the abundance of shrubs and lichens and the relationship between lichens and bryophytes strengthened after the experimental period. After five years of experimental treatments in the meadow, a positive abundance relationship emerged between bryophytes and deciduous shrubs, evergreen shrubs and forbs. This relationship was not found in the heath site. Our study therefore shows that the abundance relationships between bryophytes and plants in two vegetation types within the same area can be different. Deciduous shrubs had larger leaf area than evergreen shrubs but did not show any shading effect on H. splendens.
|
|
| 7. |
- Selander, Helena, 1975-, et al.
(författare)
-
Older drivers: On-road and off-road test results
- 2011
-
Ingår i: Accident Analysis and Prevention. - : Elsevier Science B.V., Amsterdam.. - 0001-4575 .- 1879-2057. ; 43:4, s. 1348-1354
-
Tidskriftsartikel (refereegranskat)abstract
- Eighty-five volunteer drivers, 65-85 years old, without cognitive impairments impacting on their driving were examined, in order to investigate driving errors characteristic for older drivers. In addition, any relationships between cognitive off-road and on-road tests results, the latter being the gold standard, were identified. Performance measurements included Trail Making Test (TMT), Nordic Stroke Driver Screening Assessment (NorSDSA), Useful Field of View (UFOV), self-rating driving performance and the two on-road protocols P-Drive and ROA. Some of the older drivers displayed questionable driving behaviour. In total, 21% of the participants failed the on-road assessment. Some of the specific errors were more serious than others. The most common driving errors embraced speed: exceeding the speed limit or not controlling the speed. Correlations with the P-Drive protocol were established for NorSDSA total score (weak), UFOV subtest 2 (weak), and UFOV subtest 3 (moderate). Correlations with the ROA protocol were established for UFOV subtest 2 (weak) and UFOV subtest 3 (weak). P-Drive and self ratings correlated weakly, whereas no correlation between self ratings and the ROA protocol was found. The results suggest that specific problems or errors seen in an older persons driving can actually be "normal driving behaviours".
|
|
| 8. |
- Selander, Helena, et al.
(författare)
-
The Nordic Stroke Driver Screening Assessment as predictor for the outcome of an on-road test.
- 2010
-
Ingår i: Scandinavian Journal of Occupational Therapy. - : Informa UK Limited. - 1103-8128 .- 1651-2014. ; 17:1, s. 10-17
-
Tidskriftsartikel (refereegranskat)abstract
- The use of the cognitive test battery Nordic Stroke Driver Screening Assessment (NorSDSA) has increased, sometimes as a stand-alone test to evaluate fitness to drive, also for non-stroke patients such as patients suffering from cognitive deficits/dementia, approaches that may be questioned. The objective of the study was to determine whether the NorSDSA could predict an on-road test result, for large sets of stroke ( n=74) and cognitive deficits/dementia participants ( n=116), respectively. The percentage of correctly classified was 62% for the stroke group and 50% for the cognitive deficits/dementia group. A discriminant analysis with pass/fail on the on-road test as grouping variable could classify 62% of the stroke participants and the cognitive deficit/dementia participants. Hence, the NorSDSA could not predict the outcome of the on-road test. Therefore, NorSDSA should not be used as a stand-alone test to determine the fitness to drive of individual participants. Also, its use with participants suffering from cognitive deficits/dementia appears to be less successful than for clients with stroke.
|
|
| 9. |
- Ahlström, Christer, 1977-, et al.
(författare)
-
The impact of driver sleepiness on fixation-related brain potentials
- 2020
-
Ingår i: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 29:5
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of driver sleepiness are often quantified as deteriorated driving performance, increased blink durations and high levels of subjective sleepiness. Driver sleepiness has also been associated with increasing levels of electroencephalogram (EEG) power, especially in the alpha range. The present exploratory study investigated a new measure of driver sleepiness, the EEG fixation-related lambda response. Thirty young male drivers (23.6 +/- 1.7 years old) participated in a driving simulator experiment in which they drove on rural and suburban roads in simulated daylight versus darkness during both the daytime (full sleep) and night-time (sleep deprived). The results show lower lambda responses during night driving and with longer time on task, indicating that sleep deprivation and time on task cause a general decrement in cortical responsiveness to incoming visual stimuli. Levels of subjective sleepiness and line crossings were higher under the same conditions. Furthermore, results of a linear mixed-effects model showed that low lambda responses are associated with high subjective sleepiness and more line crossings. We suggest that the fixation-related lambda response can be used to investigate driving impairment induced by sleep deprivation while driving and that, after further refinement, it may be useful as an objective measure of driver sleepiness.
|
|
| 10. |
- Anund, Anna, et al.
(författare)
-
The effects of driving situation on sleepiness indicators after sleep loss : A driving simulator study
- 2009
-
Ingår i: Industrial Health. - : National Institute of Industrial Health. - 0019-8366 .- 1880-8026. ; 47:4, s. 393-401
-
Tidskriftsartikel (refereegranskat)abstract
- Almost all studies of sleepy driving are carried out in driving simulators and with monotonous road conditions (no interaction with other cars). The present study investigated indicators of sleepy driving in a more challenging scenario after a night awake. 17 participants drove a high fidelity moving base driving simulator experiment while sleepiness was monitored physiologically and behaviourally. Short periods of situations of free driving (no other vehicles) alternated with short periods of following another vehicle (car following) with and without the possibility to overtake. The result showed that a night of prior sleep loss increased sleepiness levels at the wheel (eye closure duration and lateral variability) compared to after a night of normal sleep. Blink duration while overtaking was significantly lower compared to the other situations, it was at the same level as after night sleep. Speed when passing a stopped school bus was not significantly affected by sleepiness. However the warning caused a more rapid reduction of speed. In conclusion, a moderately challenging driving contest did not affect sleepiness indicators, but a very challenging one did so (overtaking). This suggests that it is important to monitor the driving situation in field operational tests of sleepy driving.
|
|
