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  • 251. Axelsson, Michael
    et al.
    Davison, William
    Franklin, Craig E.
    Cholinergic and adrenergic tone on the heart of the Antarctic dragonfish, Gymnodraco acuticeps, living at sub-zero temperatures2000Ingår i: Experimental Biology Online, ISSN 1430-3418, Vol. 5, nr 3, s. 1-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heart rate and ventral aortic blood pressures were recorded from the Antarctic dragonfish,Gymnodraco acuticeps, a member of the family Bathydraconidae. At −1.0 °C, the resting heart rate was 17.4 beats per minute and the ventral aortic pressure was 3.4 kPa. Cholinergic and adrenergic tone on the heart was determined by administration of the muscarine and ß-adrenoreceptor antagonists, atropine and sotalol, respectively. Neither antagonist influenced ventral aorta blood pressure; however, injection of atropine resulted in a significant increase in heart rate, and sotalol a decrease in heart rate. The cholinergic tone accounted for 30% of intrinsic heart rate and the adrenergic tone 26% of intrinsic heart rate. Comparison of these cardiac data with those for other teleosts from a wide range of thermal environments revealed no significant correlation for either cholinergic or adrenergic tone with body temperature (i.e. thermal independence); however, the resting and intrinsic heart rate of teleosts were strongly correlated with temperature.

  • 252.
    Axelsson, Per
    et al.
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden.;Stockholm Univ, Bert Bolin Ctr Climate Res, S-10691 Stockholm, Sweden..
    Tjernström, Michael
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden.;Stockholm Univ, Bert Bolin Ctr Climate Res, S-10691 Stockholm, Sweden..
    Söderberg, Stefan
    WeatherTech Scandinavia Inc, S-75310 Uppsala, Sweden..
    Svensson, Gunilla
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden.;Stockholm Univ, Bert Bolin Ctr Climate Res, S-10691 Stockholm, Sweden..
    An Ensemble of Arctic Simulations of the AOE-2001 Field Experiment2011Ingår i: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 2, nr 2, s. 146-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An ensemble of model runs with the COAMPS (c) regional model is compared to observations in the central Arctic for August 2001 from the Arctic Ocean Experiment 2001 (AOE-2001). The results are from a 6-km horizontal resolution 2nd, inner, nest of the model while the outermost model domain covers the pan-Arctic region, including the marginal ice zone and some of the land areas around the Arctic Ocean. Sea surface temperature and ice cover were prescribed from satellite data while sea-ice surface properties were modeled with an energy balance model, assuming a constant ice thickness. Five ensemble members were generated by altering the initialization time for the innermost nest, the surface roughness and the turbulent mixing scheme for clouds. The large size of the outer domain means that the model simulations have substantial deviations from the observations at synoptic-scale time scales. Therefore the evaluation focuses on statistical measures, rather than in details of individual ensemble member performance as compared directly to observations. In this context, the ensemble members are surprisingly similar even though details differ significantly. The ensemble average results features two main systematic problems: a consistent temperature bias, with too low temperatures below 2-3 km and slightly high temperatures through the rest of the troposphere, and a significant underestimation of the lowest clouds. In terms of total cloud cover, however, the model produces a realistic result; it is the very lowest clouds that are essentially missing. The temperature bias initially appears to be related to an interaction between clouds and radiation; the shape of the mean radiative heating-rate profile is very similar to that of the temperature bias. The lack of the lowest clouds could be due to the too low temperatures in conjunction with a cloud scheme that overestimates the transfer of cloud droplets to ice particles that precipitate. The different terms in the surface energy balance as well as the surface stress has only small systematic errors and are surprisingly consistent between the members.

  • 253. Axelsson, S.
    Bottenfaunan på grus- och stenbotten i Stugsjön och Hymenjaure sommaren 1972.1972Rapport (Övrigt vetenskapligt)
  • 254. Axheimer, Niklas
    et al.
    Ahlberg, Per
    Cederstrom, Peter
    A new lower Cambrian eodiscoid trilobite fauna from Swedish Lapland and its implications for intercontinental correlation2007Ingår i: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 144, nr 6, s. 953-961Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A lower Cambrian eodiscoid trilobite fauna and an associated holmiid trilobite, Holmia sp., are described from a bioclastic limestone at the top of the Tornetrask Formation in the Luobakti section, south of Lake Tornetrask, northern Sweden. Other associated polymerid trilobites include Orodes? lapponica and Strenuaeva inflata. The precise age of the trilobite fauna cannot be determined, but its generic composition and stratigraphical position at the top of the lower Cambrian suggest that it was recovered from the Ornamentaspis? linnarssoni Assemblage Zone. Two species of eodiscoids are present: Neocobboldia aff. dentata and Chelediscus acifer. The latter species is known previously from England and southeastern Newfoundland, and provides a novel link between upper lower Cambrian successions in Baltica and Avalonia.

  • 255. Ayers, G P
    et al.
    Cainey, J M
    Granek, H
    Leck, C
    Dimethylsulfide oxidation and the ratio of methanesulfonate to non sea-salt sulfate in the marine aerosol1996Ingår i: Journal of Atmospheric Chemistry, ISSN 0167-7764, E-ISSN 1573-0662, Vol. 25, nr 3, s. 307-325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A box model of DMS oxidation in the clean, low-NO, marine atmospheric boundary layer has been used to predict the latitude dependence of the aerosol methanesulfonate to non sea-salt sulfate ratio. The observed latitude dependence of this ratio in the Southern Hemisphere can be reproduced reasonably well if the full suite of reactions proposed by Yin ct al. (1990a) is employed, and a strong temperature dependence is specified in the rates of decomposition of CH3SO2 and CH3SO3 radicals.

  • 256. Backe-Forsberg, Y.
    et al.
    Baudin, K.
    Carlsson, B.
    Åberg, L.
    Turism och service i Abisko-Riksgränsenområdet.1978Rapport (Övrigt vetenskapligt)
  • 257. Backman, J
    Arctic Detailed Planning Group (ADPG) Final Report2001Ingår i: JOIDES Journal, Vol. 27, nr 2, s. 16-27Artikel i tidskrift (Övrigt vetenskapligt)
  • 258. Backman, J
    et al.
    Jakobsson, M
    Lovlie, R
    Polyak, L
    Febo, L A
    Is the central Arctic Ocean a sediment starved basin?2004Ingår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 23, nr 11-13, s. 1435-1454Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Numerous short sediment cores have been retrieved from the central Arctic Ocean, many of which have been assigned sedimentation rates on the order of mm/ka implying that the Arctic Basin was starved of sediments during Plio-Pleistocene times. A review of both shorter-term sedimentation rates, through analysis of available sediment core data, and longer-term sedimentation rates, through estimates of total sediment thickness and bedrock age, suggests that cm/ka-scale rates are pervasive in the central Arctic Ocean. This is not surprising considering the physiographic setting of the Arctic Ocean, being a small land-locked basin since its initial opening during Early Cretaceous times. We thus conclude that the central Arctic Ocean has not been a sediment starved basin, either during Plio-Pleistocene times or during pre-Pliocene times. Rigorous chronstratigraphic analysis permits correlation of sediment cores over a distance of similar to2600 km, from the northwestern Amerasia, Basin to the northwestern Eurasia Basin via the Lomonosov Ridge, using paleomagnetic, biostratigraphic, and cyclostratigraphic data. (C) 2004 Elsevier Ltd. All rights reserved.

  • 259. Backman, J.
    et al.
    Moran, K.
    McInroy, D.
    Scientists, the IODP Expedition 302
    IODP Expedition 302, Arctic Coring Expedition (ACEX): A First Look at the Cenozoic Paleoceanography of the Central Arctic Ocean2005Ingår i: Scientific Drilling, Vol. 1, s. 12-17Artikel i tidskrift (Refereegranskat)
  • 260. Backman, Jan
    et al.
    Fornaciari, Eliana
    Rio, Domenico
    Biochronology and paleoceanography of late Pleistocene and Holocene calcareous nannofossil abundances across the Arctic Basin2009Ingår i: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 72, nr 1-2, s. 86-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Late Pleistocene and Holocene stratigraphic distributions of calcareous nannofossils have been investigated in seven short cores raised from four major ridges in the Arctic Basin and in one core from the Norwegian Sea. Observed assemblages in the Arctic Ocean cores mostly represent the influence of Atlantic shallow waters. On the Gakkel and Lomonosov Ridges, a distinct cross-over in abundance occurs between Emiliania huxleyi and Gephyrocapsa spp. in the upper part of Marine Isotope Stage (MIS) 3. The lowest abundances of indigenous calcareous nannofossils occur in the southern Mendeleev Ridge core and in the two Alpha Ridge cores. These areas show a minor production of calcareous nannoplankton, probably because of the progressively diminishing influence of shallow Atlantic waters with the increasing distance from the Fram Strait gateway, the key conduit of shallow water inflow to the Arctic Ocean. It remains unknown whether or not the observed abundance patterns have been modified by glacial-interglacial scale changes in preservation. Obvious reworking becomes intensified around MIS boundaries. (C) 2009 Elsevier B.V. All rights reserved.

  • 261. Backman, Jan
    et al.
    Jakobsson, Martin
    Djuphavet kring Nordpolen och dess geologiska historia2005Ingår i: Skärgård, nr 3, s. 7-Artikel i tidskrift (Övrigt vetenskapligt)
  • 262. Backman, Jan
    et al.
    Jakobsson, Martin
    Under jordens mössa: en titt på det lilla djuphavet runt Nordpolen2005Ingår i: Geologiskt forum, ISSN 1104-4721, nr 47, s. 24-29Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 263. Backman, Jan
    et al.
    Jakobsson, Martin
    Frank, Martin
    Sangiorgi, Francesca
    Brinkhuis, Henk
    Stickley, Catherine
    O’Regan, Matthew
    Lovlie, Reidar
    Palike, Heiko
    Spofforth, David
    Gattacecca, Jerome
    Moran, Kate
    King, John
    Heil, Chip
    Age model and core-seismic integration for the Cenozoic Arctic Coring Expedition sediments from the Lomonosov Ridge2008Ingår i: Paleoceanography, ISSN 0883-8305, E-ISSN 1944-9186, Vol. 23, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cenozoic biostratigraphic, cosmogenic isotope, magnetostratigraphic, and cyclostratigraphic data derived from Integrated Ocean Drilling Program Expedition 302, the Arctic Coring Expedition (ACEX), are merged into a coherent age model. This age model has low resolution because of poor core recovery, limited availability of biostratigraphic information, and the complex nature of the magnetostratigraphic record. One 2.2 Ma long hiatus occurs in the late Miocene; another spans 26 Ma (18.2 - 44.4 Ma). The average sedimentation rate in the recovered Cenozoic sediments is about 15 m/Ma. Core-seismic correlation links the ACEX sediments to the reflection seismic stratigraphy of line AWI-91090, on which the ACEX sites were drilled. This seismostratigraphy can be correlated over wide geographic areas in the central Arctic Ocean, implying that the ACEX age model can be extended well beyond the drill sites.

  • 264. Backman, Jan
    et al.
    Moran, Kate
    The ACEX science party,
    Arctic Coring Expedition Palaeoceanographic and Tectonic evolution of the central Arctic Ocean: From Hothouse to Icehouse2004Ingår i: ECORD Newsletter, nr 3, s. 4-Artikel i tidskrift (Övrigt vetenskapligt)
  • 265. Backman, Jan
    et al.
    Moran, Kathryn
    Expanding the Cenozoic paleoceanographic record in the Central Arctic Ocean: IODP Expedition 302 Synthesis2009Ingår i: CENTRAL EUROPEAN JOURNAL OF GEOSCIENCES, ISSN 2081-9900, Vol. 1, nr 2, s. 157-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Arctic Coring Expedition (ACEX) proved to be one of the most transformational missions in almost 40 year of scientific ocean drilling. ACEX recovered the first Cenozoic sedimentary sequence from the Arctic Ocean and extended earlier piston core records from similar to 1.5 Ma back to similar to 56 Ma. The results have had a major impact in paleoceanography even though the recovered sediments represents only 29% of Cenozoic time. The missing time intervals were primarily the result of two unexpected hiatuses. This important Cenozoic paleoceanographic record was reconstructed from a total of 339 m sediments. The wide range of analyses conducted on the recovered material, along with studies that integrated regional tectonics and geophysical data, produced surprising results including high Arctic Ocean surface water temperatures and a hydrologically active climate during the Paleocene Eocene Thermal Maximum (PETM), the occurrence of a fresher water Arctic in the Eocene, ice-rafted debris as old as middle Eocene, a middle Eocene environment rife with organic carbon, and ventilation of the Arctic Ocean to the North Atlantic through the Fram Strait near the early-middle Miocene boundary. Taken together, these results have transformed our view of the Cenozoic Arctic Ocean and its role in the Earth climate system.

  • 266. Backman, Jan
    et al.
    Moran, Kathryn
    Introduction to special section on Cenozoic Paleoceanography of the Central Arctic Ocean2008Ingår i: Paleoceanography, ISSN 0883-8305, E-ISSN 1944-9186, Vol. 23, nr 1Artikel i tidskrift (Refereegranskat)
  • 267.
    Backman, Jan
    et al.
    Stockholms universitet, Institutionen för geologi och geokemi.
    Moran, Kathryn
    New results from ACEX2008Ingår i: ECORD Newsletter, Vol. 10, s. 12-13Artikel, forskningsöversikt (Övrig (populärvetenskap, debatt, mm))
  • 268. Backman, Jan
    et al.
    Moran, Kathryn
    Brinkhuis, Henk
    Cronin, Tom
    Dickens, Jerry
    Jakobsson, Martin
    Kaminski, Mike
    Matthiessen, Jens
    Moore, Ted
    Onadera, Jonaotaro
    O'Regan, Matthew
    Pälike, Heiko
    Rio, Domenico
    Smith, David C
    Suto, Itsuki
    Takahashi, Kozo
    Krylov, Alexey
    IODP Leg 302: Arctic Coring Expedition (ACEX)2005Ingår i: Polarforskningssekretariatets årsbok 2004 / [ed] Josefin Viidas, Stockholm: Polarforskningssekretariatet , 2005, s. 88-91Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 269. Backman, Jan
    et al.
    Moran, Kathryn
    Evans, Dan
    Integrated Ocean Drilling Program, Expedition 302 scientific prospectus; ACEX Arctic Coring Expediton; paleoceanographic and tectonic evolution of the central Arctic Ocean2004Bok (Övrigt vetenskapligt)
    Abstract [en]

    Five drill sites are proposed on the ridge crest of the Lomonosov Ridge in the central Arctic Ocean. The sites are distributed between 88°N and 81°N in water depths ranging between 800 and 1415 m, and are all located in international waters. The ridge was rifted from the Kara/Barents Sea shelves during early Paleogene time and subsequently subsided to its present water depth. Since that time, sediments of biogenic, aeolian and ice-rafted origin have accumulated on the ridge crest. In our primary target area between 87°N and 88°N these sediments are about 450 m thick, indicating an average rate of sedimentation of ∌10 m/my throughout the course of the Cenozoic. Sampling of these sediments would provide an unprecedented and unique opportunity to acquire a first-order knowledge about the paleoceanographic history of the central Arctic Ocean. Sampling of the underlying bedrock provides a similarly unique opportunity to decipher the tectonic history of the Lomonosov Ridge and the formation of the Eurasian Basin. The proposed program epitomizes both the spirit and the science of the new Integrated Ocean Drilling Program, calling upon the creative use of mission specific platforms and directly addressing a number of the key scientific questions raised in the IODP Initial Science Plan. Amongst scientific issues relating to "Environmental Change, Processes and Effects" are: - The long-term (50 Ma) climate history of the central Arctic Ocean, and its role in Earth’s transition from one extreme (Paleogene greenhouse) to another (Neogene icehouse). - The shorter-term (Neogene) climate history, connecting the Neogene history of the Arctic Ocean to that of the North Atlantic Ocean at sub-millennial scale resolution. Scientific issues relating to "Solid Earth Cycles and Geodynamics" are: the composition and origin of the pre-Cenozoic bedrock underlying the sediment drape; and the rifting and subsidence history of the Lomonosov Ridge. Five sites distributed over six degrees of latitude are proposed, partly with overlapping goals, which will make the drilling expedition less vulnerable to severe local ice conditions. The major goals of this proposal can be achieved by completing one site to 450 mbsf. Should ice conditions at this site be prohibited, a suite of sites from other areas along the ridge can be drilled to achieve the proposed science

  • 270. Backman, Jan
    et al.
    Moran, Kathryn
    McInroy, David
    Brinkhuis, Henk
    Clemens, Steve
    Cronin, Thomas
    Dickens, Gerald Roy
    Eynaud, Frederique
    Gattacceca, Jerome
    Jakobsson, Martin
    Jordan, Richard W.
    Kaminski, Michael
    King, John
    Koc, Nalan
    Martinez, Nahysa C.
    Matthiessen, Jens
    Moore, Theodore C., Jr.
    O’Regan, Matthew
    Palike, Heiko
    Rea, Brice
    Rio, Domenico
    Sakamoto, Tatsuhiko
    Smith, David C.
    Stein, Ruediger
    St. John, Kristen E. K.
    Suto, Itsuki
    Suzuki, Noritoshi
    Takahashi, Kozo
    Watanabe, Mahito
    Yamamoto, Masanobu
    Integrated Ocean Drilling Program Expedition 302 preliminary report; Arctic Coring Expedition (ACEX); paleoceanographic and tectonic evolution of the central Arctic Ocean; 7 August-13 September 20042005Bok (Övrigt vetenskapligt)
    Abstract [en]

    During a follow-up expedition, we will conduct the first multidimensional, cross-hole experiments attempted in the oceanic crust, including linked hydrologic, microbiological, seismic, and tracer components. After completion of drillship operations, we will initiate multiyear tests using the new network of subseafloor observatories, allowing us to examine a much larger volume of the crustal aquifer system than has been tested previously. By monitoring, sampling, and testing within multiple depth intervals, we can evaluate the extent to which oceanic crust is connected vertically and horizontally; the influence of these connections on fluid, solute, heat, and microbiological processes; and the importance of scaling on hydrologic properties. This work is helping us to understand the nature of permeable pathways, the depth extent of circulation, the importance of permeability anisotropy, and the significance of hydrogeologic barriers in the crust. ACEX’s destination was the Lomonosov Ridge, hypothesized to be a sliver of continental crust that broke away from the Eurasian plate at ∌56 Ma. As the ridge moved northward and subsided, marine sedimentation occurred and continued to the present, resulting in what was anticipated (from seismic data) to be a continuous paleoceanographic record. The elevation of the ridge above the surrounding abyssal plains (∌3 km) ensures that sediments atop the ridge are free of turbidites. The primary scientific objective of ACEX was to continuously recover this sediment record and to sample the underlying sedimentary bedrock by drilling and coring from a stationary drillship. The biggest challenge facing ACEX was maintaining the drillship’s location while drilling and coring 2-4 m thick sea ice that moved at speeds approaching half a knot. Sea-ice cover over the Lomonosov Ridge moves with the Transpolar Drift and responds locally to wind, tides, and currents. Until now, the high Arctic Ocean Basin, known as "mare incognitum" within the scientific community, had never before been deeply cored because of these challenging sea-ice conditions. Initial offshore results, based on analysis of core catcher sediments, demonstrate that biogenic carbonate only occurs in the Holocene-Pleistocene interval. The upper ∌170 m represents a record of the past ∌15 m.y. composed of sediment with ice-rafted sediment and occasional small pebbles, suggesting that ice-covered conditions extended at least this far back in time. Details of the ice cover, timing, and characteristics (e.g., perennial vs. seasonal) await further study. Earlier in the record, spanning a major portion of the Oligocene to late Eocene, an interruption in continuous sedimentation occurred. This may represent a hiatus encompassing a time interval of nondeposition or an erosional episode that removed sediment of this age from the ridge. The sediment record during the middle Eocene is of dark, organic-rich siliceous composition. Isolated pebbles, interpreted as ice-rafted dropstones, are present down to 239 mbsf, well into the middle Eocene section. An interval recovered around the lower/middle Eocene boundary contains an abundance of Azolla spp., suggesting that a fresh/low salinity surface water setting dominated the region during this time period. Although predictions based on geophysical data had placed the base of the sediment column at 50 Ma, drilling revealed that the latest Paleocene to earliest Eocene boundary interval, well known as the early Eocene Thermal Maximum (EETM), was recovered. During the EETM, the Arctic Ocean was subtropical with warm surface ocean temperatures. ACEX penetrated into the underlying sedimentary bedrock, revealing a shallow-water depositional environment of Late Cretaceous age.

  • 271. Backman, Jan
    et al.
    Moran, Kathryn
    McInroy, David
    Brinkhuis, Henk
    Clemens, Steven
    Cronin, Thomas
    Dickens, Gerald Roy
    Eynaud, Frederique
    Gattacceca, Jerome
    Jakobsson, Martin
    Jordan, Richard W.
    Kaminski, Michael
    King, John
    Koc, Nalan
    Martinez, Nahysa C.
    Matthiessen, Jens
    Moore, Theodore C., Jr.
    Onodera, Jonaotaro
    O’Regan, Matthew
    Palike, Heiko
    Rea, Brice
    Rio, Domenico
    Sakamoto, Tatsuhiko
    Smith, David C.
    Stein, Ruediger
    St. John, Kristen E. K.
    Suto, Itsuki
    Suzuki, Noritoshi
    Takahashi, Kozo
    Watanabe, Mahito
    Yamamoto, Masanobu
    Methods2004Ingår i: Proceedings of the Integrated Ocean Drilling Program, ISSN 1930-1014, Vol. 302Artikel i tidskrift (Refereegranskat)
  • 272. Backman, Jan
    et al.
    Moran, Kathryn
    McInroy, David
    Brinkhuis, Henk
    Clemens, Steven
    Cronin, Thomas
    Dickens, Gerald Roy
    Eynaud, Frederique
    Gattacceca, Jerome
    Jakobsson, Martin
    Jordan, Richard W.
    Kaminski, Michael
    King, John
    Koc, Nalan
    Martinez, Nahysa C.
    Matthiessen, Jens
    Moore, Theodore C., Jr.
    Onodera, Jonaotaro
    O’Regan, Matthew
    Palike, Heiko
    Rea, Brice
    Rio, Domenico
    Sakamoto, Tatsuhiko
    Smith, David C.
    Stein, Ruediger
    St. John, Kristen E. K.
    Suto, Itsuki
    Suzuki, Noritoshi
    Takahashi, Kozo
    Watanabe, Mahito
    Yamamoto, Masanobu
    Sites M0001-M00042004Ingår i: Proceedings of the Integrated Ocean Drilling Program, ISSN 1930-1014, Vol. 302Artikel i tidskrift (Refereegranskat)
  • 273. Backman, Jan
    et al.
    Moran, Kathryn
    McInroy, David
    Brinkhuis, Henk
    Clemens, Steven
    Cronin, Thomas
    Dickens, Gerald Roy
    Eynaud, Frédérique
    Gattacceca, JérÎme
    Jakobsson, Martin
    Jordan, Richard W.
    Kaminski, Michael
    King, John
    Koc, Nalan
    Martinez, Nahysa C.
    Matthiessen, Jens
    Moore, Theodore C., Jr.
    Onodera, Jonaotaro
    O’Regan, Matthew
    Palike, Heiko
    Rea, Brice
    Rio, Domenico
    Sakamoto, Tatsuhiko
    Smith, David C.
    Stein, Ruediger
    St. John, Kristen E. K.
    Suto, Itsuki
    Suzuki, Noritoshi
    Takahashi, Kozo
    Watanabe, Mahito
    Yamamoto, Masanobu
    Expedition 302 summary2004Ingår i: Proceedings of the Integrated Ocean Drilling Program, ISSN 1930-1014, Vol. 302Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The first scientific drilling expedition to the central Arctic Ocean was completed in September 2004. Integrated Ocean Drilling Program Expedition 302, Arctic Coring Expedition (ACEX), recovered sediment cores to 428 meters below seafloor (mbsf) in water depths of ∌1300 m, 250 km from the North Pole. Expedition 302’s destination was the Lomonosov Ridge, hypothesized to be a sliver of continental crust that broke away from the Eurasian plate at ∌56 Ma. As the ridge moved northward and subsided, marine sedimentation occurred and continues to the present, resulting in what was anticipated from seismic data to be a continuous paleoceanographic record. The elevation of the ridge above the surrounding abyssal plains (∌3 km) ensured that sediments atop the ridge were free of turbidites. The primary scientific objective of Expedition 302 was to continuously recover this sediment record and to sample the underlying sedimentary bedrock by drilling and coring from a stationary drillship. The biggest challenge during Expedition 302 was maintaining the drillship’s location while drilling and coring in 2-4 m thick sea ice that moved at speeds approaching 0.5 kt. Sea-ice cover over the Lomonosov Ridge moves with one of the two major Arctic sea-ice circulation systems, the Transpolar Drift, and responds locally to wind, tides, and currents. Until now, the high Arctic Ocean Basin, known as "mare incognitum" within the scientific community, had never before been deeply cored because of these challenging sea-ice conditions. Initial results reveal that biogenic carbonate is present only in the Holocene-Pleistocene interval. The upper 198 mbsf represents a relatively high sedimentation rate record of the past 18 m.y. and is composed of sediment with ice-rafted debris and dropstones, suggesting that ice-covered conditions extended at least this far back in time. Details of the ice type (e.g., iceberg versus sea ice), timing, and characteristics (e.g., perennial versus seasonal) await further study. A hiatus occurs at 193.13 mbsf, spanning a 25 m.y. interval from the early Miocene to the middle Eocene between ∌18 Ma and 43 Ma. The sediment record during the middle Eocene is of dark, organic-rich biosiliceous composition. Isolated pebbles, interpreted as ice-rafted dropstones, are present down to 239 mbsf, well into this middle Eocene interval. Around the lower/middle Eocene boundary an abundance of Azolla spp. occurs, suggesting that a fresh and/or low-salinity surface water setting dominated the region during this time period. Although predrilling predictions based on geophysical data had placed the base of the sediment column at 50 Ma, drilling revealed that the uppermost Paleocene to lowermost Eocene boundary interval, well known as the Paleocene/Eocene Thermal Maximum (PETM), was recovered. During the PETM, the temperature of the Arctic Ocean surface waters exceeded 20°C. Drilling during Expedition 302 also penetrated into the underlying sedimentary bedrock, revealing a shallow-water depositional environment of Late Cretaceous age.

  • 274.
    Baddeley, J.A.
    Dept of Environmental Biology.
    Effects of atmospheric nitrogen deposition on the ecophysiology of Racomitrium lanuginosum (Hedw. ) Brid.1991Studentuppsats (Examensarbete)
  • 275. Bagge, A.
    Stenåldern vid Torneträsk.1937Ingår i: Norrbotten. Norrbottens Läns Hembygdsförenings Årsbok 1937, 1937, s. 89-106Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 276. Bakker, D. C. E.
    et al.
    Pfeil, B.
    Landa, C. S.
    Metzl, N.
    O’Brien, K. M.
    Olsen, A.
    Smith, K.
    Cosca, C.
    Harasawa, S.
    Jones, S. D.
    Nakaoka, S. -I
    Nojiri, Y.
    Schuster, U.
    Steinhoff, T.
    Sweeney, C.
    Takahashi, T.
    Tilbrook, B.
    Wada, C.
    Wanninkhof, R.
    Alin, S. R.
    Balestrini, C. F.
    Barbero, L.
    Bates, N. R.
    Bianchi, A. A.
    Bonou, F.
    Boutin, J.
    Bozec, Y.
    Burger, E. F.
    Cai, W. -J
    Castle, R. D.
    Chen, L.
    Chierici, M.
    Currie, K.
    Evans, W.
    Featherstone, C.
    Feely, R. A.
    Fransson, A.
    Goyet, C.
    Greenwood, N.
    Gregor, L.
    Hankin, S.
    Hardman-Mountford, N. J.
    Harlay, J.
    Hauck, J.
    Hoppema, M.
    Humphreys, M. P.
    Hunt, C. W.
    Huss, B.
    Ibánhez, J. S. P.
    Johannessen, T.
    Keeling, R.
    Kitidis, V.
    Körtzinger, A.
    Kozyr, A.
    Krasakopoulou, E.
    Kuwata, A.
    Landschützer, P.
    Lauvset, S. K.
    Lefèvre, N.
    Lo Monaco, C.
    Manke, A.
    Mathis, J. T.
    Merlivat, L.
    Millero, F. J.
    Monteiro, P. M. S.
    Munro, D. R.
    Murata, A.
    Newberger, T.
    Omar, A. M.
    Ono, T.
    Paterson, K.
    Pearce, D.
    Pierrot, D.
    Robbins, L. L.
    Saito, S.
    Salisbury, J.
    Schlitzer, R.
    Schneider, B.
    Schweitzer, R.
    Sieger, R.
    Skjelvan, I.
    Sullivan, K. F.
    Sutherland, S. C.
    Sutton, A. J.
    Tadokoro, K.
    Telszewski, M.
    Tuma, M.
    van Heuven, S. M. A. C.
    Vandemark, D.
    Ward, B.
    Watson, A. J.
    Xu, S.
    A multi-decade record of high-quality fCO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT)2016Ingår i: Earth System Science Data, Vol. 8, nr 2, s. 383-413Artikel i tidskrift (Refereegranskat)
  • 277. Bakker, D. C. E.
    et al.
    Pfeil, B.
    Smith, K.
    Hankin, S.
    Olsen, A.
    Alin, S. R.
    Cosca, C.
    Harasawa, S.
    Kozyr, A.
    Nojiri, Y.
    O’Brien, K. M.
    Schuster, U.
    Telszewski, M.
    Tilbrook, B.
    Wada, C.
    Akl, J.
    Barbero, L.
    Bates, N. R.
    Boutin, J.
    Bozec, Y.
    Cai, W. -J
    Castle, R. D.
    Chavez, F. P.
    Chen, L.
    Chierici, M.
    Currie, K.
    de Baar, H. J. W.
    Evans, W.
    Feely, R. A.
    Fransson, A.
    Gao, Z.
    Hales, B.
    Hardman-Mountford, N. J.
    Hoppema, M.
    Huang, W. -J
    Hunt, C. W.
    Huss, B.
    Ichikawa, T.
    Johannessen, T.
    Jones, E. M.
    Jones, S. D.
    Jutterstrom, S.
    Kitidis, V.
    Koertzinger, A.
    Landschuetzer, P.
    Lauvset, S. K.
    Lefevre, N.
    Manke, A. B.
    Mathis, J. T.
    Merlivat, L.
    Metzl, N.
    Murata, A.
    Newberger, T.
    Omar, A. M.
    Ono, T.
    Park, G. -H
    Paterson, K.
    Pierrot, D.
    Rios, A. F.
    Sabine, C. L.
    Saito, S.
    Salisbury, J.
    Sarma, V. V. S. S.
    Schlitzer, R.
    Sieger, R.
    Skjelvan, I.
    Steinhoff, T.
    Sullivan, K. F.
    Sun, H.
    Sutton, A. J.
    Suzuki, T.
    Sweeney, C.
    Takahashi, T.
    Tjiputra, J.
    Tsurushima, N.
    van Heuven, S. M. A. C.
    Vandemark, D.
    Vlahos, P.
    Wallace, D. W. R.
    Wanninkhof, R.
    Watson, A. J.
    An update to the Surface Ocean CO2 Atlas (SOCAT version 2)2014Ingår i: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 6, nr 1, s. 69-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Surface Ocean CO2 Atlas (SOCAT), an activity of the international marine carbon research community, provides access to synthesis and gridded fCO(2) (fugacity of carbon dioxide) products for the surface oceans. Version 2 of SOCAT is an update of the previous release (version 1) with more data (increased from 6.3 million to 10.1 million surface water fCO(2) values) and extended data coverage (from 1968-2007 to 1968-2011). The quality control criteria, while identical in both versions, have been applied more strictly in version 2 than in version 1. The SOCAT website (http://www.socat.info/) has links to quality control comments, metadata, individual data set files, and synthesis and gridded data products. Interactive online tools allow visitors to explore the richness of the data. Applications of SOCAT include process studies, quantification of the ocean carbon sink and its spatial, seasonal, year-to-year and longer-term variation, as well as initialisation or validation of ocean carbon models and coupled climate-carbon models.

  • 278. Bale, J.S.
    Impacts of climate warming on arctic aphids: a comparative analysis.1999Ingår i: Ecological Bulletins, Vol. 47, s. 38-47Artikel i tidskrift (Övrigt vetenskapligt)
  • 279. Bale, J.S.
    Insects at low temperature: a predictable relationship?.1991Ingår i: Functional Ecology, Vol. 5, s. 291-298Artikel i tidskrift (Övrigt vetenskapligt)
  • 280. Bale, J.S.
    et al.
    Strathdee, A.T.
    Strathdee, F.C.
    Effects of low temperature on the Arctic aphid Acyrthosiphon brevicorne1994Ingår i: Functional Ecology, Vol. 8, s. 621-626Artikel i tidskrift (Övrigt vetenskapligt)
  • 281. Balogianni, Vasiliki G.
    et al.
    Blume-Werry, Gesche
    Wilson, Scott D.
    Root production in contrasting ecosystems: the impact of rhizotron sampling frequency2016Ingår i: Plant Ecology, ISSN 1385-0237, E-ISSN 1573-5052, Vol. 217, nr 11, s. 1359-1367Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Despite their critical role in every terrestrial ecosystem, fine root production and mortality have not been widely compared among systems due to the practical difficulties of belowground research. We examined fine root production and mortality among five contrasting sites: native and invaded grassland in eastern Montana, USA, aspen forest in southern Saskatchewan, Canada, and birch forest and tundra in northern Sweden. Additionally, we investigated the importance of minirhizotron sampling interval on measures of root production and mortality by comparing measures produced from 1-, 7-, 14-, and 21-day sample intervals. Root length and mortality varied significantly among sites, with invaded grassland having the greatest root length (>2 × than any other site) and significantly greater root mortality than native grassland (54 %). In contrast, there were no significant differences in root production among the sites. Sample interval had no significant influence on root production or mortality. Minirhizotron sampling intervals up to 3 weeks did not underestimate the measures of root production and mortality in comparison to measures derived from shorter sampling intervals, regardless of the site studied. The results suggest that 3 weeks can be an accurate and efficient sample interval when studying root production and mortality with minirhizotrons.

  • 282. Barbier, D.
    et al.
    Chalonge, D.
    Vassy, É.
    Mesure de la teneur en ozone des couches basses de l'atmosphére pendant l'hiver.1936Ingår i: Comptes rendus hebdomadaires des séances de l'Academie des sciences, Vol. 202, s. 1525-1527Artikel i tidskrift (Övrigt vetenskapligt)
  • 283. Barbier, D.
    et al.
    Chalonge, D.
    Vassy, É.
    Mesure del'épaisseur réduite de l'ozone atmospherique pendant l'hiver polaire.1935Ingår i: C R 20lArtikel i tidskrift (Övrigt vetenskapligt)
  • 284. Barbier, D.
    et al.
    Chalonge, D.
    Vassy, É.
    Nouvelles methodes pour la mesure nocturne de l'ozone atmosphérique.1934Ingår i: Revue d'OptiqueArtikel i tidskrift (Övrigt vetenskapligt)
  • 285. Barker, A.J.
    Metamorphic evolution of the Caledonian nappes of north central Scandinavia.1989Ingår i: The Caledonide Geology of Scandinavia / [ed] Gayer, R.A, 1989, s. 193-204Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 286. Barkman, J.J.
    Impressions of the North Swedish forest excursion.1951Ingår i: Vegetation Acta Geobotanica, Vol. 3, nr 3, s. 175-182Artikel i tidskrift (Övrigt vetenskapligt)
  • 287.
    Barnekow, L.
    Department of Quaternary Geology.
    Holocene vegetation dynamics and climate changes in the Torneträsk area, northern Sweden.1999Studentuppsats (Examensarbete)
  • 288. Barnekow, L.
    et al.
    Hammarlund, D.
    Holocene forest dynamics and climate changes recorded in lake sediments in the Abisko area, northern Sweden.1996Ingår i: GFF, Vol. 118, s. 2-Artikel i tidskrift (Övrigt vetenskapligt)
  • 289. Barnekow, L.
    et al.
    Possnert, G.
    Sandgren, P.
    AMS 14C chronologies of Holocene lake sediments in the Abisko area, northern Sweden - a comparison between dated bulk sediment and macrofossil samples.1998Ingår i: GFF, Vol. 120, s. 59-67Artikel i tidskrift (Övrigt vetenskapligt)
  • 290. Barnekow, L.
    et al.
    Sandgren, P.
    Palaeoclimate and tree-line changes during the Holocene based on pollen and plant macrofossil records from six lakes at different altitudes in northern Sweden.2001Ingår i: Review of Palaeobotany & Palynology, Vol. 117, s. 109-118Artikel i tidskrift (Övrigt vetenskapligt)
  • 291. Barreyre, Thibaut
    et al.
    Soule, S. Adam
    Sohn, Robert A.
    Dispersal of volcaniclasts during deep-sea eruptions: Settling velocities and entrainment in buoyant seawater plumes2011Ingår i: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, E-ISSN 1872-6097, Vol. 205, nr 3-4, s. 84-93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use tank experiments to measure settling rates of deep-sea volcaniclastic material recovered from the Arctic (85 degrees E Gakkel Ridge) and Pacific (Juan de Fuca Ridge, Loihi seamount) Oceans. We find that clast size and shape exert a strong influence on settling velocity, with velocities of similar to 30 cm/s for large (similar to 8 mm), blocky clasts, compared to velocities of similar to 2.5 cm/s for small (<0.5 mm), sheet-like clasts. We fit our observations to the generalized model of Ferguson and Church (2004) to establish empirical scaling laws for settling velocity, and then use these results to test the hypothesis that entrainment in a buoyant plume of hot seawater is an important dispersal mechanism for volcaniclastic material in the deep-sea (Clague et al., 2009). We superpose the observed settling rates on velocity fields generated with the Morton et al. (1956) model for turbulent plumes in stratified media to estimate the rise height of the clastic material under water column conditions corresponding to the Gakkel and Juan de Fuca (JdFR) Ridges, and then estimate dispersal distances assuming the grains settle to the seafloor while being advected in lateral currents. Dispersal distances in our model are a function plume strength (i.e., buoyancy flux), lateral current speeds, and clast settling velocity. Our model demonstrates that large (30 GW) eruption ‘megaplumes’ can loft volcaniclastic material more than a kilometer above the seafloor where entrainment in deep-sea currents can advect dominant clast types (similar to 1 mm, blocky grains) up to a few hundred meters from a source vent. Small bubble-wall fragments (e.g., limu o Pele) entrained in a megaplume could be advected as far as a few kilometers from a source region. These results indicate that entrainment in buoyant seawater plumes during an eruption may play an important role in clast dispersal, but it is not clear if this mechanism can explain the distribution of volcaniclastic material at the sites on the Gakkel and Juan de Fuca Ridges where our samples were acquired. In order to understand the dispersal of volcaniclastic material in the deep-sea it will be necessary to rigorously characterize existing deposits, and develop models capable of incorporating explosive gas phases into the eruption plume. (C) 2011 Elsevier B.V. All rights reserved.

  • 292. Barsig, M.
    et al.
    Schneider, K.
    Gehrke, C.
    Effects of UV-B radiation on fine structure, carbohydrates, and pigments in Polytrichum commune.1998Ingår i: The Bryologist, Vol. 101, nr 3, s. 357-365Artikel i tidskrift (Övrigt vetenskapligt)
  • 293.
    Bartels, Pia
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Ask, Jenny
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Umeå marina forskningscentrum (UMF).
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Allochthonous Organic Matter Supports Benthic but Not Pelagic Food Webs in Shallow Coastal Ecosystems2018Ingår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, nr 7, s. 1459-1470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rivers transport large amounts of allochthonous organic matter (OM) to the ocean every year, but there are still fundamental gaps in how allochthonous OM is processed in the marine environment. Here, we estimated the relative contribution of allochthonous OM (allochthony) to the biomass of benthic and pelagic consumers in a shallow coastal ecosystem in the northern Baltic Sea. We used deuterium as a tracer of allochthony and assessed both temporal variation (monthly from May to August) and spatial variation (within and outside river plume). We found variability in allochthony in space and time and across species, with overall higher values for zoobenthos (26.2 +/- 20.9%) than for zooplankton (0.8 +/- 0.3%). Zooplankton allochthony was highest in May and very low during the other months, likely as a result of high inputs of allochthonous OM during the spring flood that fueled the pelagic food chain for a short period. In contrast, zoobenthos allochthony was only lower in June and remained high during the other months. Allochthony of zoobenthos was generally higher close to the river mouth than outside of the river plume, whereas it did not vary spatially for zooplankton. Last, zoobenthos allochthony was higher in deeper than in shallower areas, indicating that allochthonous OM might be more important when autochthonous resources are limited. Our results suggest that climate change predictions of increasing inputs of allochthonous OM to coastal ecosystems may affect basal energy sources supporting coastal food webs.

  • 294. Barth, L.
    et al.
    Angerbjörn, A.
    Tannerfeldt, M.
    Are Norwegian lemmings Lemmus lemmus avioded by arctic Alopex lagopus or red foxes Vulpes vulpes? A feeding experiment2000Ingår i: Wildlife Biology, Vol. 6, nr 2, s. 101-109Artikel i tidskrift (Övrigt vetenskapligt)
  • 295.
    Barthelemy, Hélène
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Herbivores influence nutrient cycling and plant nutrient uptake: insights from tundra ecosystems2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Reindeer appear to have strong positive effects on plant productivity and nutrient cycling in strongly nutrient-limited ecosystems. While the direct effects of grazing on vegetation composition have been intensively studied, much less is known about the indirect effect of grazing on plant-soil interactions. This thesis investigated the indirect effects of ungulate grazing on arctic plant communities via soil nutrient availability and plant nutrient uptake.

    At high density, the deposition of dung alone increased plant productivity both in nutrient rich and nutrient poor tundra habitats without causing major changes in soil possesses. Plant community responses to dung addition was slow, with a delay of at least some years. By contrast, a 15N-urea tracer study revealed that nutrients from reindeer urine could be rapidly incorporated into arctic plant tissues. Soil and microbial N pools only sequestered small proportions of the tracer. This thesis therefore suggests a strong effect of dung and urine on plant productivity by directly providing nutrient-rich resources, rather than by stimulating soil microbial activities, N mineralization and ultimately increasing soil nutrient availability. Further, defoliation alone did not induce compensatory growth, but resulted in plants with higher nutrient contents. This grazing-induced increase in plant quality could drive the high N cycling in arctic secondary grasslands by providing litter of a better quality to the belowground system and thus increase organic matter decomposition and enhance soil nutrient availability. Finally, a 15N natural abundance study revealed that intense reindeer grazing influences how plants are taking up their nutrients and thus decreased plant N partitioning among coexisting plant species.

    Taken together these results demonstrate the central role of dung and urine and grazing-induced changes in plant quality for plant productivity. Soil nutrient concentrations alone do not reveal nutrient availability for plants since reindeer have a strong influence on how plants are taking up their nutrients. This thesis highlights that both direct and indirect effects of reindeer grazing are strong determinants of tundra ecosystem functioning. Therefore, their complex influence on the aboveground and belowground linkages should be integrated in future work on tundra ecosystem N dynamic.

  • 296. Barthelemy, Hélène
    et al.
    Dorrepaal, Ellen
    Olofsson, Johan
    Defoliation of a grass is mediated by the positive effect of dung deposition, moss removal and enhanced soil nutrient contents: results from a reindeer grazing simulation experiment2019Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 128, nr 10, s. 1515-1524Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Herbivory is one of the key drivers shaping plant community dynamics. Herbivores can strongly influence plant productivity directly through defoliation and the return of nutrients in the form of dung and urine, but also indirectly by reducing the abundance of neighbouring plants and inducing changes in soil processes. However, the relative importance of these processes is poorly understood. We, therefore, established a common garden experiment to study plant responses to defoliation, dung addition, moss cover, and the soil legacy of reindeer grazing. We used an arctic tundra grazed by reindeer as our study system, and Festuca ovina, a common grazing-tolerant grass species as the model species. The soil legacy of reindeer grazing had the strongest effect on plants, and resulted in higher growth in soils originating from previously heavily-grazed sites. Defoliation also had a strong effect and reduced shoot and root growth and nutrient uptake. Plants did not fully compensate for the tissue lost due to defoliation, even when nutrient availability was high. In contrast, defoliation enhanced plant nitrogen concentrations. Dung addition increased plant production, nitrogen concentrations and nutrient uptake, although the effect was fairly small. Mosses also had a positive effect on aboveground plant production as long as the plants were not defoliated. The presence of a thick moss layer reduced plant growth following defoliation. This study demonstrates that grasses, even though they suffer from defoliation, can tolerate high densities of herbivores when all aspects of herbivores on ecosystems are taken into account. Our results further show that the positive effect of herbivores on plant growth via changes in soil properties is essential for plants to cope with a high grazing pressure. The strong effect of the soil legacy of reindeer grazing reveals that herbivores can have long-lasting effects on plant productivity and ecosystem functioning after grazing has ceased.

  • 297. Barthelemy, Hélène
    et al.
    Stark, Sari
    Olofsson, Johan
    Strong Responses of Subarctic Plant Communities to Long-Term Reindeer Feces Manipulation2015Ingår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 18, nr 5, s. 740-751Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Deposition of feces is a key mechanism by which herbivores influence soil nutrient cycling and plant production, but the knowledge about its importance for plant production and community structure is still rudimental since experimental evidence is scarce. We thus performed a 7-year long reindeer feces manipulation experiment in two tundra vegetation types with contrasting nutrient availability and analyzed effects on plant community composition and soil nutrient availability. Despite feces being fairly nutrient poor, feces manipulation had strong effect on both the nutrient-poor heath and the nutrient-rich meadow. The strongest effect was detected when feces were added at high density, with a substantial increase in total vascular plant productivity and graminoids in the two communities. Doubling natural deposition of reindeer feces enhanced primary production and the growth of deciduous shrubs in the heath. By contrast, removal of feces decreased only the production of graminoids and deciduous shrubs in the heath. Although the response to feces addition was faster in the nutrient-rich meadow, after 7 years it was more pronounced in the nutrient-poor heath. The effect of feces manipulation on soil nutrient availability was low and temporarily variable. Our study provides experimental evidence for a central role of herbivore feces in regulating primary production when herbivores are abundant enough. Deposition of feces alone does, however, not cause dramatic vegetation shifts; to drive unproductive heath to a productive grass dominated state, herbivore trampling, and grazing are probably also needed.

  • 298. Bartholin, T.S.
    et al.
    Karlén, W.
    Dendrokronologi i Lappland AD 436-1981.1983Rapport (Övrigt vetenskapligt)
  • 299. Bartsch, A.
    et al.
    Gude, M.
    Jonasson, C.
    Scherer, D.
    Identification of geomorphic process units in Kärkevagge, northern Sweden by remote sensing and digital terrain analysis.2002Ingår i: Geografiska Annaler, Vol. 84A, nr 3-4, s. 171-178Artikel i tidskrift (Övrigt vetenskapligt)
  • 300. Baruah, Gaurav
    et al.
    Molau, Ulf
    Bai, Yang
    Alatalo, Juha M
    Community and species-specific responses of plant traits to 23 years of experimental warming across subarctic tundra plant communities2017Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To improve understanding of how global warming may affect competitive interactions among plants, information on the responses of plant functional traits across species to long-term warming is needed. Here we report the effect of 23 years of experimental warming on plant traits across four different alpine subarctic plant communities: tussock tundra, Dryas heath, dry heath and wet meadow. Open-top chambers (OTCs) were used to passively warm the vegetation by 1.5–3 °C. Changes in leaf width, leaf length and plant height of 22 vascular plant species were measured. Long-term warming significantly affected all plant traits. Overall, plant species were taller, with longer and wider leaves, compared with control plots, indicating an increase in biomass in warmed plots, with 13 species having significant increases in at least one trait and only three species having negative responses. The response varied among species and plant community in which the species was sampled, indicating community-warming interactions. Thus, plant trait responses are both species- and community-specific. Importantly, we show that there is likely to be great variation between plant species in their ability to maintain positive growth responses over the longer term, which might cause shifts in their relative competitive ability.

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