CONTENTS & ABSTRACTS
In English. Summaries in Estonia
Proceedings of the Estonian Academy of Sciences.
Volume 49 No. 2 June 2000
Distribution of phosphorus in the sediment core of hypertrophic Lake Ruusmäe and some palaeoecological conclusions; 163–176
Kristjan KRUUSEMENT and Jaan-Mati PUNNING
Abstract. The distribution of phosphorus fractions in the sediments that accumulated in Lake Ruusmäe during the last 4–5 decades was studied. The study focuses on the possible correlations between the vertical distribution of phosphorus fractions in the sediment core and the dynamics of the external load. The results suggest that sedimentation of organic material and its decomposition were the major mechanisms governing the distribution of phosphorus and its fractions in sediments at all depths except the interval of 29–20 cm, where a high phosphorus content was caused by redeposited matter. This general regularity is disturbed by variation in the aeration conditions, reflected in the changes in the content of phosphorus fractions. The fractional composition and increasing content of total phosphorus towards the surface indicate that although the external load decreased sharply in the 1990s, the actual phosphorus content in the lake has not yet been significantly reduced.
Key words: phosphorus, palaeolimnology, lake sediments, external load, trophic history.
Mapping of wetland habitat diversity using satellite data and GIS: An example from the Alam-Pedja Nature Reserve, Estonia; 177–193
Kiira AAVIKSOO, Jaanus PAAL, and Tiina DIŠLIS
Abstract. The experience of compiling a habitat map of the Alam-Pedja Nature Reserve, Estonia, based on integrating remote sensing (Landsat 5 TM, aerial photos), Geographic Information Systems (GIS), and national biological survey data is reported and discussed. Unsupervised and supervised classification and the maximum likelihood algorithm were used for the classification of satellite image pixels. Training polygons for justification of the classification were established after the repetitive checking of all classification units during the classification procedure. On that basis the mapping of different habitats, specific for the temperate zone and especially for Estonian nature, using a classification scheme with an emphasis on spectral separation of wetland and related forest types on satellite images was developed. The resultant map (1 : 50 000, Transverse Mercator Projection) includes 26 mapping units and fits rather well the Estonian habitat classification scheme. The map can be employed for land use conflict resolution, for monitoring at landscape and habitat level, as well as in biodiversity studies.
Key words: GIS, habitat classification, Landsat TM, mapping, remote sensing, wetlands.
Spatio-temporal development of the Soomaa mire system in SW Estonia; 194–208
Abstract. The spatio-temporal development pattern of a mire system and major factors affecting this process were studied. The Soomaa mire system (25 100 ha) in south-western Estonia is one of the largest and best preserved mire systems in Estonia. Using the bulk densities of peat layers and radiocarbon dates average accumulation rates and increments of different peat types were calculated. On the basis of the obtained and already existing stratigraphical data the probable development of the mire system was reconstructed. Paludification of the Soomaa region started about 10 000 BP and ombrotrophication 7000–6000 BP. The expansion rate of the mire system was rather stable during the whole Holocene and no distinct relationship between the climate and the expansion of mires was detected. The results suggest that the expansion of mires was mostly an autogenous process, while ombrotrophication might have been favoured also by climate changes. The spatial dynamics of paludification was mainly determined by local factors – topographical and hydrological characteristics of the area.
Key words: mire system, expansion of mires, paludification, ombrotrophication, Estonia.
A check-list of chironomid larvae (Diptera, Chironomidae) of Estonian streams in 1987–97; 209–220
Abstract. In 173 Estonian streams, studied in 1987–97, a total of at least 184 taxa of larvae of non-biting midges were found, 43 of them registered in Estonia for the first time. The taxa were classified into subfamilies as follows: Tanypodinae – 23 taxa, Diamesinae – 9 taxa, Prodiamesinae – 3 taxa, Orthocladiinae – 72 taxa, and Chironominae – 77 taxa. According to frequency of occurrence, 52 taxa (28.3%) out of 184 belonged to very rare, 90 (48.9%) to rare, 28 (15.2%) to common, 10 (5.4%) to frequent, and 4 (2.2%) to very frequent larvae of chironomids. Altogether, at least 216 taxa of chironomid larvae have been registered in Estonian streams up to now.
Key words: chironomid larvae, streams, Estonia, check-list.
Abbreviations and terms: R. = river, B. = brook, M. d./m. d. = main ditch.
The term streams is in this paper used as the common name for any brook, river, or any other kind of course of running water.
First record of the talitrid amphipod Orchestia cavimana in the northern Baltic Sea; 221–224
Abstract. Orchestia cavimana was found for the first time on the Estonian coast in 1999. The species inhabits Fucus vesiculosus wrack. The high abundance and biomass values indicate that the species has formed a permanent population in the region. In the coming years O. cavimana will likely expand its distribution area in other parts of the Estonian coastal sea.
Key words: Orchestia cavimana, distribution, Baltic Sea.
Viktor Masing 75; 225–226
Instructions to authors; 227–230
Copyright Transfer Agreement; 231