1.
Persson, Lars
(författare)
Sandviksmoarna - Gröntjärn
1976
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Föreliggande arbete gäller naturinventering vid Sandviksmoarna inom Ljusdals och Hudiksvalls kommuner. Fältarbetet har utförts i sep-okt 1975 och sammanställningen under vintern 1975-76.Uppdragsgivare har varit länsstyrelsen i Gävleborgs län och syftet med inventeringen att skapa underlag för ett säkerställande av området enligt naturvårdslagen. Området har klassificerats som objekt av riksintresse i programarbetet för den fysiska riksplaneringen.Målsättningen vid inventeringsarbetet har främst varit att ge en detaljerad sammanställning av områdets geologiska, geomorfologiska och hydrologiska förhållanden samt på grundval av detta ge förslag till åtgärder och lämplig form för säkerställande.Hydrologiavsnittet utgör inventeringens tyngdpunkt eftersom de geologiska förhållandena gör hydrologin ovanligt komplicerad och det främst är hydrologiska företeelser som har gjort området känt. Framställningen är inte, som det från början var tänkt, enbart beskrivande utan innehåller även tolkning av bildningsförlopp och olika samband. Det senare har tillkommit därför att en ren beskrivning inte är tillräcklig för att belysa området särart.Framställningen är uppdelad i inventeringsdel, förslagsdel, fotobilaga och kartbilagorna är främst ett komplement till inventeringsdelen och bilderna i fotobilagan är med för att illustrera olika detaljer av intresse inom området.
2.
Hansson, Kenth, et al.
(författare)
Gröntjärn- ett Naturfenomen eller...
1975
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Fältarbetet utfördes under tiden 8/4 - 10/4, 2/5 – 6/7 1974 samt vid ett flertal tillfällen under hösten 1974. Under tiden 5/5 – 6/7 bodde vi i Bergvik och Ala:s stuga vid Gröntjärn.SAMMANFATTNING OCH SLUTSATSERDet undersökta området är beläget i ett mäktigt stråk av isälvsavlagringar norr om Ljusdal. Gröntjärn och Strå sjö-Långtjärn utgörs av dödisgravar på ömse sidor om en hög brant ås. Gröntjärn saknar både ytligt tillopp och ytligt avlopp.En ytvattenförbindelse mellan Gröntjärn och Benbergsbäcken kan uppstå vid mycket höga vattenstånd i tjärnen väster om Gröntjärn. En fåra i den rygg som avskiljer från varandra tyder på att så har varit fallet någon gång.
3.
Hernroth, Lars, et al.
(författare)
The Zooplankton Of The Baltic Proper : A long-term investigation of the fauna, its biology and ecology
1979
Rapport (övrigt vetenskapligt/konstnärligt) abstract
This paper is based on the results from a long-term zooplankton investigation in the Baltic proper in the years 1968—1972. Additional results, obtained by the authors in more recent investigations, have also been used in order to enrich the material with information not obtained in the principal investigation.Seven standard plankton stations, covering seven sub-areas of the Baltic proper have been visited on average four to five times per year. All cruises have been made in connection with ordinary hydrographical expeditions which means that all zooplankton samples are accompanied by a complete list of hydrographical data.The paper describes the zooplankton fauna of the Baltic proper which comprises about 40 regularly appearing species excluding the micro zooplankton. The main part of the fauna in respect of biomass and production consists, however, of only 10—12 species. The most important were the cnidarian Aurelia aurita. the rotifers Synchaeta spp., the cladocerans Bosmina coregoni maritima and Evadne nordmanni, the copepods Pseudocalanus minutas elongatus, Temora longicornis, Acartia bifilosa, A. longiremis and Centropages hamatus and the larvacean Fritillariaborealis.Species of less importance were the larvae of Pleurobrachia pileus, the cladocerans Podon intermedius, P. leuckarti and Pleopsis polyphemodides (the latter is abundant in coastal areas), the copepods Eurytemora sp. and Oithona similis, the larvae of gastropod species, Mytilus edulis, Macoma baltica, Cardium glaucum. C.hauniense and My a arenaria, the chaetognath Sagitta elegans baltica and the larvacean Oikopleura dioica.Occaisonal species were the cnidarians Sarsia tubulosa and Cyanea capillata, the rotifers Keratella quadrata quadrata, K. qu. platei, K. cruciformis eichwaldi and K.cochlearis recurvispina, the larvae of Pygospio elegans and Balanus improvisus, the copepods Calanus finmarchicus, Limnocalanus macrurus and Cyclops sp., the mysidaceans Mysis relicta and M. mixta, the amphipod Hyperia galba and the chaetognath Sagitta setosa.All samples have been collected by vertical, fractionated hauls with a Nansennet. The mesh size was 0.160 mm in the years 1968—1971 and 0.090 mm in 1972. A correction of all results due to the poor filtering capacity of the Nansen net has been made. The additional results are mainly based on samples from the UNESCOWP 2 net.All specimens have been analysed to species and the copepods also to developmental stages. The biomass has been calculated as the sum of all individual volumes.The paper also describes the hydrography of the Baltic proper in general and presents the data for temperature, salinity and oxygen in the years 1968—1972.The relationship between the unique hydrography of the Baltic with its stable, brackish water contidions and the planktonfauna is discussed.The regulating factors for the vertical and horizontal distribution of the fauna were found to be either temperature or salinity or a combination of these factors.The seasonal variation in biomass values showed a rather good correlation with the temperature of the surface layer viz. the lowest biomass values (< 10 g m-2) were usually found in March—April, an increase started in May—June and a maximum (30—60 g m-2) was most often reached in August—September. There were great variations in biomass between the seven stations. The highest mean values (20—25 gm"2) were found in the southern and south-eastern parts of the Baltic proper and the lowest (12—13 gm-2) in the northern and south-western parts. Looking at the biomass values over the whole period of investigation, a remarkable stability has been found. There is no evidence of either increasing or decreasing trend.The production of zooplankton has also been estimated. According to our calculations the production amounts to about 20 gC m-2 year-1 (380 g wwt) in the southern Baltic proper and 10 gC m-2 year-1 (190 g wwt) in the northern part.The last part of the paper discusses the role of zooplankton in the energy flow of the whole pelagic ecosystem, i.e. from primary phytoplankton production to reproduction and recruitment of pelagic fishes.
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6.
Andersson, Ulla-Maria, et al.
(författare)
Hydrochemical investigations in three representative basins in Sweden
1978
Rapport (övrigt vetenskapligt/konstnärligt) abstract
SummaryDuring the IHD-period 1965—1974 chemical investigations were carried out in the three representative basins Velen, Kassjöån and Lappträsket, mainly to obtain balances of common constituents in surface waters, taking into account deposition from the atmosphere.As to the seasonal variation of concentrations in discharge from the basins and sub-basins it is remarkably suppressed compared to variations in discharge rates. This can be explained by the storage in lakes and as groundwater which tend to smooth rapid fluctuations in concentrations. However, it also indicates that surface run-off during snow-melt is in no way a dominant process. The largest fluctuations are found for the nitrogen compounds ammonia and nitrate where complex biological processes may at times either "fix" or release nitrogen compounds from organic matter.Considering balances of incoming — outflowing constituents, sulphur and nitrogen compounds always show a deficit; much more is deposited from the atmosphere than carried away from the basins by run-off. There are two possible mechanisms which explain this. One is a loss as volatile sulphur and nitrogen compounds from soils due to microbiological processes in reducing environments. The other possibility is a steady increase in soil sulphur and nitrogen (bound in organic matter) revealing an ongoing adjustment of soil sulphur and nitrogen to the increasing levels of atmospheric deposition of these.As to the balances of calcium, magnesium, sodium and potassium they indicate losses in the ground due to weathering. There are differences in the rates of weathering in the three basins which can be explained on basis of differences in the mineralogical composition of the hard rocks which are so common in Sweden.
7.
8.
Bengtsson, Lars
(författare)
Mathematical models of wind induced circulation i a lake
1973
Ingår i: IAHS-AISH Publication. - 0144-7815. ; 109, s. 313-320
Tidskriftsartikel (refereegranskat) abstract
Transient and stead y-state models for homogeneous and two-layered water masses are presented. The stationary models have been adapted to Lake Velen. The correspondencebetween theoretical and measured currents was good. A transport of momentum probably takesplace only where the thermocline touches the bottom. Knowledge of Ihe turbulent mechanismsis more important than the analytical approaches made in the model. The time in which thesteady state is reached depends on the depth to the thermocline and on the turbulence. Normally the steady state is reached in a few hours.
9.
10.
Bengtsson, L.
(författare)
Wind Induced Circulation In Lakes
1978
Ingår i: Nordic Hydrology. - 0029-1277 .- 1996-9694. ; 9:2, s. 75-94
Tidskriftsartikel (refereegranskat)