Abstract: Light penetration measurements of blue (Schott filter BG 12), green (VG 9), and red (RG 630) light was made in 30 Finnish lakes with different degree of humus content and eutrophy for the comparison of the structure of phytoplankton communities and the light environment in the waters. The relations between Secchi disc visibility and the penetrations of different spectral regions and relations between the light conditions and the colour of the water was examined. The increase of ɛmin m−1 caused by humus material is 0.008 In units per colour unit (mg Pt l−1). The optical depth was especially in brown waters smaller than calculated by Formula after Talling (1965).

Abstract: In northern Sweden two field experiments with the reforestation techniques soil scarification, ploughing, burning and grass herbicidal treatment were performed. Small rodents were trapped regularly on the managed plots and their stomachs were examined microscopically for diet composition. Both bank voles Clethrionomys glareolus and field voles Microtus agrestis were common on the reforestation areas while only a small number of grey-sided voles Clethrionomys rufocanus were taken. All three species underwent a population cycle during the studies. The management techniques generally resulted in small and irregular effects on the food selection. The most pronounced changes were lower intake of grasses by M. agrestis after herbicidal treatment and of filamentous tree lichens by C. glareolus after most treatments. Both bank voles and field voles ate predominantly forbs in the summer half of the year, whereas the field voles took also a considerable amount of grass. As a complement to green vegetable-matter bank voles ate berries and fungi in summer-autumn and tree lichens at other times of the year, but seeds and animals food only in very small amounts. Ail three species consumed large quantities of dwarf-shrubs in autumn and especially in winter. Considerable amounts of bark were eaten by field voles and a smaller proportion by bank voles in autumn-winter. Both for bank and field voles there were indications of worsening food conditions as the population cycle went on, There were, for example, an increase in grass and bark intake in field voles and a decrease in seeds and berries for the hank vole.

Abstract: Microfungi were isolated by the soil washing technique from 5 soil horizons in each of 3 podzolic coniferous forests: Picea abies at Kongalund, S. Sweden, Pinus sylvestris at Ivantjarnsheden and P. abies/P. sylvestris at Nickobacken (both central Sweden). A total of 126 species was identified, of which 45 were found at 3, and 24 at 2 of the sites. Mortierella and Penicillium were the commonest genera. Species composition differed markedly between the soil layers, but was similar between sites, for a given soil layer. From authors' summary. ADDITIONAL ABSTRACT: Fungi were isolated by the soil washing technique from 5 soil horizons in each of 3 podzols: spruce at Kongalund, pine at Ivantjarnsheden, and spruce and pine at Nickobacken (south, central and central Sweden, respectively). A total of 126 spp. was identified of which 45 were found at 3 and 24 at 2 of the sites. Mortierella and Penicillium predominated. Spp. composition differed markedly between the soil layers but was similar between sites for a given layer [RPP 58, 3694] (Less)

Abstract: Survival of the midge larvae Chironomus plumosus and C. anthracinus in anoxia at 4°C was investigated. C. plumosus survived about twice as long as C. anthracinus. The corresponding LT 50 values were ca 205 and 100 d. There was no statistically significant difference between the survival in anoxia and in aerated water, which indicates that the main reason for death in anoxia is not the absence of oxygen. This main reason is presumed to be starvation. The presence of undissociated H2S in low concentrations (ca 1.2 mg 1−1) did not influence the survival. In anoxia the larvae were usually motionless and did not feed but they increased in weight due to uptake of water. During 43 d C. plumosus and C. anthracinus increased ca. 10%.

Abstract: The interdisciplinary study of the lake ecosystem was carried out under the auspices of the International Biological Programme. The reasons for the choice of the lake and the personnel and institutions involved in the project are described. A brief description is given of the lake itself, its catchment area and its location, together with a short historical review of the development of the area and the degree of human influence.

Abstract: Catches of Trichoptera from 67 light traps in Great Britain are studied. Two families are excluded: the Limnephilidae because they have been considered in an earlier publication, and the Hydroptilidae. Catches from 148 complete year records, from 1965 to 1971, are grouped in three areas: A. Scotland, 15 sites; B. Wales and Northern England. 18 sites; C. Southern England, 34 sites. The total of over 146000 caddis flies includes 60 of the 109 British species from 14 families. Small or nil catches are explained by limited distribution or dispersal, short adult lives and day-flying habits. The flight periods are related to published information on life cycles. Most species are univoltine, but some small species are bivoltine. In contrast to Limnephilidae, there is no evidence of a summer adult diapause, median weeks for flight periods tend to be earlier in the south, and few species are autumnal fliers. Density distribution maps, produced by computer, are given for six species.

Abstract: The Norwegian subalpine lake. Ovre Heimdalsvatn, has a surface area of 0.78 km2 and a maximum depth of 13 m. It is ice-covered for 7.5–8 months, has a marked spring spate and a mean annual renewal period of about two months. The water is poor in electrolytes. Intensive studies have been made by an interdisciplinary team of the lake's physical and chemical properties, primary production and secondary production under the auspices of IBP/PF from 1969 to 1973, Allochthonous material accounted for 1/3 of utilized plant input. The major lake predator, the brown trout, fed largely on benthic organisms and did not exploit the zooplankton biomass. On account of the long period of ice cover and the rapid rise in temperature after ice break, many organisms (both planktonic and benthic) showed synchronous development. Abiotic conditions, such as the nature of the spring spate and the temperature rise, strongly affect species and community development.

Abstract: Twenty stations were sampled monthly during the ice free period (June-September) in 1972. Emergence traps, emptied daily, were also employed. The major macroinvertebrates in the exposed zone were Ephemeroptera, Gammarus lacustris, Trichoptera, Chironomidae, Plecoptera and Coleoptera, and these constituted over 90% of total numbers. Densities of G. lacustris, Ephemeroptera, Tipulidae and Plecoptera showed a positive correlation with detritus. No significant relationship was found for the other taxa. Nearly 70% of the fauna emerged, and did so during the period from June to September. Chironomidae, Ephemeroptera, Plecoptera, Trichoptera and Tipulidae accounted for nearly all emergence and their total average annual emergence was 372 cal m2. Of this total, Chironomidae constituted 28%, Ephemeroptera 28%, Plecoptera and Trichoptera 15% each and Tipulidae 4%.

Abstract: Biomass and nutrient transfer (N, P, K, Ca, Mg) of overstory (branches and leaves) and understory litter fall were examined over a two year period in four jack pine stands aged 16, 29, 49 and 57 years and four mixed hardwood stands aged 7, 17, 20 and 29 years. Relative amounts of the five nutrients in litter fall for both series of stands were N > K ≷ Ca > P = Mg. Return of mineral elements to the forest floor was generally twice as high on the hardwood stands as for similarly aged pine stands. Overall return of nutrients plotted versus stand age generally exhibited a plateau relationship, with relatively little difference among stands; however, some exceptions occurred. Understory contribution to litter fall was very important on these stands, since in most cases the nutrient mass in understory litter was usually similar to or higher than that from the tree layer. Data on forest floor biomass, nutrient distribution and turnover rates of these stands were also presented; mobility of nutrients in the forest floor was in the order K > Mg ≥ P ≥ Ca ≥ N.

Abstract: The sediments and various organisms in Lake Paijanne were examined for contaminants. The average mercury content of water plants was 9, of plankton 14, of sediment 114, of zoobenthic predators 83, of fish 332–1510 and of birds 240–13685 μg kg−1 (wet weight). The average PCB content of plants was 3, of plankton 21, of the zoobenthos 44, of fish 36-117 and of birds 219–13490 μg kg−1. The average ΔDDT content of plants was 0.5, of plankton 6, of the zoobenthos 14, of fish 7–42 and of birds 144-8262 μg kg−1. Regional differences in mercury content were most pronounced in sediment and fish. PCB concentration was highest near a town. ΔDDT was quite evenly distributed. Water plant species did not differ from each other, nor did the plankton fractions. The zoobenthic predators contained more chlorinated hydrocarbons than did the herbivores. There were clear differences between most species of fish and the chlorinated hydrocarbon content was highest in vendace. In adult birds levels of all residues were significantly higher than in juveniles. In most cases PCB content was positively correlated with ΔDDT and in birds PCB, ΔDDT and mercury levels were correlated. DDT residues occurred mostly as DDE, but in vendace the proportion of DDT was high. At most trophic levels, ΔDDT/PCB was 0.15-0.40 but in birds it reached 1–2.

Abstract: The Lake Ovre Heimdalsvatn is greatly affected by wind. Precipitation, especially heavy rainfall, has probably a good possibility of eroding and leaching material into the lake. The mean annual temperature is −1.2°C, and the estimated mean annual evapo-transpiration is about 200 mm. The lake is covered by ice from late October to the beginning of June. Run-off, lake level and precipitation are well correlated, indicating that the influence of the catchment is large and rapid.

Abstract: Ninety cultures of heterotrophic organisms were isolated from soils of four acid Norwegian forest sites, which were active in nitrifying. The isolates were tested for ability to form nitrite in a glucose-ammonium-inorganic salts medium. Eleven cultures were found capable of oxidizing ammonium to nitrite. The nitrifying organisms consist of 4 bacteria and 7 fungi.

Abstract: The annual minimum energy consumption of the bird community was 2524 × 103 kcal km−2, of which 44% was consumed by wintering species and 73% by passerines The daily energy consumption was in summer 14–16 × 103 and in winter 1–2 × 103 kcal km−2 In spruce forests and in afforested swamps birds required approximately 012% of the net primary production Their total annual energy consumption was covered by invertebrates (59%), vertebrates (2%) and vegetable matter (39%); the food derived from the ground (55%), from trees (44%) and from the air (1%) Arboreal insectivorous passerines, ground passerines and gallinaceous birds were the most important ecological guilds Among passerines existence metabolism accounted for 73% of the annual energy consumption, extra activity for 17%, breeding activity for 1%, moult for 4% and nestlings for 4%

Abstract: The lotic communities in Ovre Heimdalen were completely dominated by insects. The species distribution of stoneflies (Plecoptera), mayflies (Ephemeroptera) and caddisflies (Trichoptera) is given together with autecological notes on the Plecoptera and certain other major species. The species distribution of these groups, especially the Plecoptera, was clearly related to the deciduous vegetation along the streams. There was a reduction in species parallel to a reduction in Salix vegetation. The main inlet stream to the lake, Ovre Heimdalsvatn, the outlet and the outlet stream had different faunal compositions. The inlet fauna consisted to a large extent of winter growing species, mainly detritus feeders, while the outlet and outlet stream had a fauna dominated by summer growing species, several of which were filter feeders.

Abstract: The size and appearance of the preputial glands of Clethrionomys glareolus showed variations which were associated with season, sex and maturation. The glands were by far largest in mature males followed by mature females, and subadult males and females, in that order. There was a positive relationship between the length, fresh weight and dry weight of the glands. The possible role of the preputial glands in relation to territorially, social status and sexual attraction is discussed.

Abstract: A total of 67 species of chironomids were caught in emergence traps placed at the shoreline. Additional larval records increase the number of species to be at least 75, a high number of species possibly explained by the exposed nature of the lake, which also provides habitats for lotic forms. The species composition and relative abundance of the four main groups of Chironomidac indicate that Ovre Heimdalsvatn is a subarctic lake, with a strong oligotrophic character. The emergence period starts in mid-June and lasts to mid-September. Diversity studies show similarity with mountain lakes in France and with the Bodensee, but the equilability in Ovre Heimdalsvatn is lower. The chironomid faunal composition of Ovre Heimdalsvatn seems to be determined by abiotic ecological factors and not the history of distribution.

Abstract: The paper describes abiotic factors of basic importance for the biological research carried out simultaneously in the lake Ovre Heimdalsvatn.

Abstract: A phytoplankton investigation was carried out in the subalpine, low-productive Norwegian lake Ovre Heimdalsvatn in 1969–70 and 1972. This paper describes the temporal and spatial distribution of the standing stock of phytoplankton, and phytoplankton primary productivity. The annual average primary productivity in 1972 was 4.0–4.9 mg C m−3 d−1; the annual average standing stock varied from 120 mg m−3 (freshweight) in 1969–70, to 250 mg m−3 in 1972. Phytoplankton species composition and size distribution is discussed. Throughout the year the phytoplankton is dominated by small (ultraplankton) species; μ-algae (< 5 μm) showed cell concentrations up to 15 mill. cells 1−1. The dominating group was chrysophytes; cryptophytes, dinoflagellates or green algae were at times abundant. A phytoplankton monthly budget and a diagram showing annual average carbon flow through the standing stock of phytoplankton are presented; the phytoplankton dynamics in Ovre Heimdalsvatn is compared to that of other low-productive lakes.

Abstract: Auchenorrhyncha of a new polder were sampled by different kinds of traps in four stations in new habitats, one station on the salt marsh and one just outside the polder. In the latter stations 20 species of Auchenorrhyncha were caught in numbers that declined during the four year study. The proportion of macropters of the common Streptanus sordidus was highest in the largest catches. In the polder proper 392 specimens of 13 species were caught, all had moved at least 1500 m, but some could be traced to origins at greater distances. The number of immigrants also declined during the study. The distribution of the leafhoppers over the trapping stations suggests that leafhoppers, although sometimes transported over great distances, as a rule quickly fall out once they are airborne. Probably only one species had founded a resident population in the new polder at the end of the study.

Abstract: About 300 km line transect censuses of breeding land birds were made in northern Norway in 1974–76. The data (1020 pairs in 26 samples) were grouped into seven major habitats: stony ground and oceanic heath (C1), continental dry heath (C2). “′2Calcarius heath”, dry peatland, wet peatland (C5), meagre and average birch forest, and rich birch forest (C7). Bird density ranged from 22 pairs km−2 (C2) to 364 pairs km−2 (C7), but most habitats had 67–96 pairs km−2. The bird communities are described. Defining the Optimal habitat for a species as the maximum-density habitat, the 43 species observed were found to comprise three major groups: tundra species (optimal habitat C1), peatland species (C5) and forest species (C7). Species whose central range includes northern Norway had a broader habitat amplitude than those with a southern or a very northern distribution. A new index was devised for the evaluation of the conservational importance of a habitat or a species. From the North European standpoint. C1 is certainly the most important habitat in northern Norway, as C1 supports many species which are rare in other parts of North Europe. However, population trends should also be taken into account when conservational preferences are judged.

Abstract: For the purpose of benthic studies Ovre Heimdalsvatn was divided into three depth zones. These were the exposed zone (from the shore down to 1–2 m depth), the macrophytic zone (1–2 m to 5–5.5 m depth) and the non-macrophytic zone (5–5.5 m to 13 m). The reasons for this division and the main characteristics of each zone, including the substrata present, are given.

Abstract: The catchment area of Ovre Heimdalsvatn reaches from the upper half of the subalpine birch forest zone to the lowermost part of the high-alpine subzone within the alpine zone. The units dominating the area include mountain birch forest, tall herb meadow, mire vegetation, bilberry heath, snowbed communities, chionophobous heath vegetation, and areas without a continuous vegetation layer. It is shown that the potential natural vegetation corresponds closely to the actual vegetation distribution.

Abstract: Cooking Lake (113°02′W, 53°26′N), a well-mixed, shallow (mean depth (1.59 m), eutrophic lake in Alberta, Canada, is characterized by eutrophic chlorococcalean and cyanophycean phytoplankton associations, and little change in standing crop with increasing depth. Standing crop and primary productivity are low during the winter but pronounced spring and summer maxima occur. Mean yearly areal standing crop (ΔB) and primary productivity (ΔA) were 212.4 mg m−2 chlorophyll a and 301.8 mg C h−1 m−2 respectively. Annual productivity was estimated at 1322 g C m−2. The mean increase in the extinction coefficient (ɛ) per unit increase in standing crop (B) was 0.03 In units m−1. High non-algal light attenuation (ɛq) occurred avenging 41 which prevented the ratio B/ɛ from attaining more than 65% of the theoretical maximum except once when algal self-shading occurred. Close correlations existed between B (mg m−3 chlorophyll a) and A max (mg h−1 m−3) ΔA and ΔB, ΔA and B, Amax, and Amax/ɛ, and ΔA and Io′, (W m−2). The depth of the euphotic zone (Zeu) varied between 0.5 and 1 25 m; the average relationship between zeu and E was Zeu= 3.74/ɛ, and the mean standing Crop found in the euphotic zone represented 55.2% of the theoretical maximum, The high ɛq, values made the model of Tailing (1957) inapplicable to Cooking Lake. The Q10 value for the lake was 2.2. The maximum rate of photosynthesis per unit of population per h. Omax, (mg C sag chlorophyll a−1 h−1) was more closely related to temperature than irradiance and ma depressed by pH values greater than 9.1. Growth of the phytoplankton was not nutrient limited: instead irradiance and temperature were more important. Indirect evidence that free CO2 limited photosynthetic rates, is provided by the Omax: pH relationship.

Abstract: Ovre Heimdalsvatn is clearly influenced by the geological conditions, and the lake basin and catchment area are determined by the bedrock and the mountain structures. The distribution and characteristics of the loose deposits are decisive for the lake's water budget. The groundwater in the catchment area and the Quaternary deposits near the lake influence the amount and quality of the lake waters.

Abstract: The vegetation of a snow bed has been described by a pin-point method and a modified Raunkiaer frequency analysis. The thawing of the snow has been followed and some soil properties have been investigated. It is concluded that the composition of the vegetation in the snow bed is influenced mainly by the duration of the growth period, but locally the density and the species composition are determined by the downward flow of the melt water.

Abstract: Two sediment cores, 143 cm and 268 cm in length, have been investigated. The oldest dating is 8240 ± 500 radiocarbon years B.P. The variation in the composition of the sediments is probably caused solely by climatic changes. The organic fraction is small, never exceeding 20%, reflecting the low primary production and rapid decomposition of allochthonous organic matter within the lake. The proportions of inorganic constituents indicate that the mineral fraction consists of clay and silt particles flushed into the lake from the drainage area.

Abstract: About one hundred genera with more than 300 species have been identified in water samples, net haul material, periphyton samples from artificial substrate, and benthos and sediment samples collected during 1969–1972. More than 40 taxa of lower rank (subspecies, varieties, forms) were recorded. The most prominent algal groups were diatoms with 138 taxa, and green algae with 122 taxa of which the majority was desmids. The material from the epipelic and epilithic communities in the lake is very scarce, while the list of plankton species is relatively complete, with the exception that a large number of small flagellates could not be identified to species level. The taxa which were identified, are presented in a list with additional notes on occurrence.

Abstract: The small mammals of the Ovre Heimdalen valley were assessed by snap-trapping. Birds were surveyed in the shore zone of the lake. Numbers of domestic animals were collected from existing sources. These data are used in a discussion of the influence of the terrestrial fauna on the lake ecosystem. Aquatic production of food for terrestrial vertebrates, and the fertilizing effect of the terrestrial fauna are the main influences on the lake.

Abstract: Owing to the high altitude of Ovre Heimdalen and the complex topography within the valley, climatic conditions are complicated. The valley is situated in a mountain region with a subarctic or tundra macroclimate, which exists over the lake itself and on the SSW-valley side. However, the favourable combination of slope angle and exposure of the NNE-valley side gives a radiation or continental type of local climate on this side. The large net input of radiant energy onto the NNE-valley side during the summer results in higher air temperatures, greater precipitation and higher air humidity than elsewhere in the valley. This is clearly reflected in the luxuriant vegetation on this side. Thus, the climate of the Ovre Heimdalsvatn area is strongly influenced by terrain irregularities and shows how fundamentally different growth possibilities due to local climates may be over short distances in the uppermost valleys on the eastern side of the central mountain chain.