| 1. |
- Bergsten, Johannes, 1975-, et al.
(författare)
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Species delimitation of the Hyphydrus ovatus complex in western Palaearctic with an update of species distributions (Coleoptera, Dytiscidae)
- 2017
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Ingår i: ZooKeys. - : Pensoft Publishers. - 1313-2989 .- 1313-2970. ; 678, s. 73-96
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Tidskriftsartikel (refereegranskat)abstract
- The species status of Hyphydrus anatolicus Guignot, 1957 and H. sanctus Sharp, 1882, previously often confused with the widespread H. ovatus (Linnaeus, 1760), are tested with molecular and morphological characters. Cytochrome c oxidase subunit 1 (CO1) was sequenced for 32 specimens of all three species. Gene-trees were inferred with parsimony, time-free bayesian and strict clock bayesian analyses. The GMYC model was used to estimate species limits. All three species were reciprocally monophyletic with CO1 and highly supported. The GMYC species delimitation analysis unequivocally delimited the three species with no other than the three species solution included in the confidence interval. A likelihood ratio test rejected the one-species null model. Important morphological characters distinguishing the species are provided and illustrated. New distributional data are given for the following species: Hyphydrus anatolicus from Slovakia and Ukraine, and H. aubei Ganglbauer, 1891, and H. sanctus from Turkey.
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| 2. |
- Burgos, Maria A., et al.
(författare)
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A global model-measurement evaluation of particle light scattering coefficients at elevated relative humidity
- 2020
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:17, s. 10231-10258
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Tidskriftsartikel (refereegranskat)abstract
- The uptake of water by atmospheric aerosols has a pronounced effect on particle light scattering properties, which in turn are strongly dependent on the ambient relative humidity (RH). Earth system models need to account for the aerosol water uptake and its influence on light scattering in order to properly capture the overall radiative effects of aerosols. Here we present a comprehensive model-measurement evaluation of the particle light scattering enhancement factor f (RH), defined as the particle light scattering coefficient at elevated RH (here set to 85 %) divided by its dry value. The comparison uses simulations from 10 Earth system models and a global dataset of surface-based in situ measurements. In general, we find a large diversity in the magnitude of predicted f (RH) amongst the different models, which can not be explained by the site types. Based on our evaluation of sea salt scattering enhancement and simulated organic mass fraction, there is a strong indication that differences in the model parameterizations of hygroscopicity and model chemistry are driving at least some of the observed diversity in simulated f (RH). Additionally, a key point is that defining dry conditions is difficult from an observational point of view and, depending on the aerosol, may influence the measured f (RH). The definition of dry also impacts our model evaluation, because several models exhibit significant water uptake between RH = 0% and 40 %. The multisite average ratio between model outputs and measurements is 1.64 when RH = 0% is assumed as the model dry RH and 1.16 when RH = 40% is the model dry RH value. The overestimation by the models is believed to originate from the hygroscopicity parameterizations at the lower RH range which may not implement all phenomena taking place (i.e., not fully dried particles and hysteresis effects). This will be particularly relevant when a location is dominated by a deliquescent aerosol such as sea salt. Our results emphasize the need to consider the measurement conditions in such comparisons and recognize that measurements referred to as dry may not be dry in model terms. Recommendations for future model-measurement evaluation and model improvements are provided.
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| 3. |
- Burgos, María A., et al.
(författare)
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A global view on the effect of water uptake on aerosol particle light scattering
- 2019
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Ingår i: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- A reference dataset of multi-wavelength particle light scattering and hemispheric backscattering coefficients for different relative humidities (RH) between RH = 30 and 95% and wavelengths between lambda = 450 nm and 700 nm is described in this work. Tandem-humidified nephelometer measurements from 26 ground-based sites around the globe, covering multiple aerosol types, have been re-analysed and harmonized into a single dataset. The dataset includes multi-annual measurements from long-term monitoring sites as well as short-term field campaign data. The result is a unique collection of RH-dependent aerosol light scattering properties, presented as a function of size cut. This dataset is important for climate and atmospheric model-measurement inter-comparisons, as a means to improve model performance, and may be useful for satellite and remote sensing evaluation using surface-based, in-situ measurements.
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| 4. |
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| 5. |
- Titos, Gloria, et al.
(författare)
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A global study of hygroscopicity-driven light-scattering enhancement in the context of other in situ aerosol optical properties
- 2021
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:17, s. 13031-13050
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Tidskriftsartikel (refereegranskat)abstract
- The scattering and backscattering enhancement factors (f(RH) and fb(RH)) describe how aerosol particle light scattering and backscattering, respectively, change with relative humidity (RH). They are important parameters in estimating direct aerosol radiative forcing (DARF). In this study we use the dataset presented in Burgos et al. (2019) that compiles f(RH) and fb(RH) measurements at three wavelengths (i.e., 450, 550 and 700 nm) performed with tandem nephelometer systems at multiple sites around the world. We present an overview of f(RH) and fb(RH) based on both long-term and campaign observations from 23 sites representing a range of aerosol types. The scattering enhancement shows a strong variability from site to site, with no clear pattern with respect to the total scattering coefficient. In general, higher f(RH) is observed at Arctic and marine sites, while lower values are found at urban and desert sites, although a consistent pattern as a function of site type is not observed. The backscattering enhancement fb(RH) is consistently lower than f(RH) at all sites, with the difference between f(RH) and fb(RH) increasing for aerosol with higher f(RH). This is consistent with Mie theory, which predicts higher enhancement of the light scattering in the forward than in the backward direction as the particle takes up water. Our results show that the scattering enhancement is higher for PM1 than PM10 at most sites, which is also supported by theory due to the change in scattering efficiency with the size parameter that relates particle size and the wavelength of incident light. At marine-influenced sites this difference is enhanced when coarse particles (likely sea salt) predominate. For most sites, f(RH) is observed to increase with increasing wavelength, except at sites with a known dust influence where the spectral dependence of f(RH) is found to be low or even exhibit the opposite pattern. The impact of RH on aerosol properties used to calculate radiative forcing (e.g., single-scattering albedo, ω0, and backscattered fraction, b) is evaluated. The single-scattering albedo generally increases with RH, while b decreases. The net effect of aerosol hygroscopicity on radiative forcing efficiency (RFE) is an increase in the absolute forcing effect (negative sign) by a factor of up to 4 at RH = 90 % compared to dry conditions (RH < 40 %). Because of the scarcity of scattering enhancement measurements, an attempt was made to use other more commonly available aerosol parameters (i.e., ω0 and scattering Ångström exponent, αsp) to parameterize f(RH). The majority of sites (75 %) showed a consistent trend with ω0 (higher f(RH = 85 %) for higher ω0), while no clear pattern was observed between f(RH = 85 %) and αsp. This suggests that aerosol ω0 is more promising than αsp as a surrogate for the scattering enhancement factor, although neither parameter is ideal. Nonetheless, the qualitative relationship observed between ω0 and f(RH) could serve as a constraint on global model simulations.
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| 6. |
- Wirta, Helena K., et al.
(författare)
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Exposing the structure of an Arctic food web
- 2015
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 5:17, s. 3842-3856
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Tidskriftsartikel (refereegranskat)abstract
- How food webs are structured has major implications for their stability and dynamics. While poorly studied to date, arctic food webs are commonly assumed to be simple in structure, with few links per species. If this is the case, then different parts of the web may be weakly connected to each other, with populations and species united by only a low number of links. We provide the first highly resolved description of trophic link structure for a large part of a high-arctic food web. For this purpose, we apply a combination of recent techniques to describing the links between three predator guilds (insectivorous birds, spiders, and lepidopteran parasitoids) and their two dominant prey orders (Diptera and Lepidoptera). The resultant web shows a dense link structure and no compartmentalization or modularity across the three predator guilds. Thus, both individual predators and predator guilds tap heavily into the prey community of each other, offering versatile scope for indirect interactions across different parts of the web. The current description of a first but single arctic web may serve as a benchmark toward which to gauge future webs resolved by similar techniques. Targeting an unusual breadth of predator guilds, and relying on techniques with a high resolution, it suggests that species in this web are closely connected. Thus, our findings call for similar explorations of link structure across multiple guilds in both arctic and other webs. From an applied perspective, our description of an arctic web suggests new avenues for understanding how arctic food webs are built and function and of how they respond to current climate change. It suggests that to comprehend the community-level consequences of rapid arctic warming, we should turn from analyses of populations, population pairs, and isolated predator-prey interactions to considering the full set of interacting species.
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| 7. |
- Wirta, Helena K., et al.
(författare)
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Extensive niche overlap among the dominant arthropod predators of the High Arctic
- 2015
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791 .- 1618-0089. ; 16:1, s. 86-92
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Tidskriftsartikel (refereegranskat)abstract
- In the High Arctic, the species richness of spiders is typically low, but abundances can be very high. Thus, how the few spider species occurring in the region choose their prey, and what prey taxa they focus on, may significantly affect the community structure of arctic arthropods. Here we estimate the ecological imprint of adult spiders of three large-bodied species coexisting in Northeast Greenland: the morphologically similar crab spiders Xysticus deichmanni and X. labradorensis (Thomisidae) and the wolf spider Pardosa glacialis (Lycosidae). To describe an important part of these spiders' diet in detail, we amplified and sequenced DNA from prey remains in their guts, selectively focusing on two of the most abundant prey orders in the area (Diptera and Lepidoptera). By comparing the resultant sequences to a reference library including most taxa encountered in the region, we assigned the prey to species. Among the spider taxa occurring in the region, the wolf spider Pardosa glacialis is dominant in terms of both biomass and density. All three spider species proved to be wide generalists, with no detectable differences in prey choice among either the two crab spiders, or among these crab spiders and the wolf spider. This lack of dietary differentiation among species may be caused by the limited prey availability in the Arctic, forcing the predators to both generalism and opportunism. Given the substantial abundance of spiders and the lack of other predatory arthropods in the region, the opportunistic prey choice observed implies that these High-Arctic spider species have the potential for inflicting a strong influence on their prey community.
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