CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Volume 51 No. 3 September 2002
Shape and area of simple narrow leaves; 147–162
Matti Mõttus, Juhan Ross †, and Vello Ross
Abstract. New comprehensive models of radiative transfer in plant canopies require detailed information about 3D architecture at the stand and plant levels. In such models, the leaf (or shoot for conifers) has been accepted as the smallest structural unit. Because of the great variability of leaf shape and area of different plant species, different methods have been elaborated for the description of this unit. In this paper, an analytical leaf shape function is proposed for flat narrow leaves. The leaf shape function yields the half-width of the leaf at point x if the midrib of the leaf coincides with the x-axis using three parameters: leaf length, maximum leaf width, and a leaf shape parameter. Integration over the x-coordinate of the shape function from the leaf insertion point to the leaf tip yields the area of the leaf.
For the application of the model, measurements of the leaf parameters of two willow species, Salix viminalis and S. dasyclados, were used. The measurements were carried out in 1996–2001 at Tartu Observatory, Estonia. Statistical analysis of the variability of leaf length, maximum leaf width, and leaf area revealed very large variations of these parameters. For example, leaf area varies between 10 and 2700 mm2 for S. viminalis and between 6 and 7000 mm2 for S. dasyclados. Despite the great variability of leaf parameters, the proposed formulas for leaf area and leaf shape follow closely the actual shape of the leaf. Agreement is somewhat better for S. dasyclados than for S. viminalis.
Key words: plant architecture, leaf area, leaf shape, willow leaves.
Partitioning of nutrients and biomass in Scots pine canopy; 163–172
Malle Mandre and Hardi Tullus
Abstract. Spatial partitioning of nutrients in the canopy of Pinus sylvestris L. was evaluated quantitatively and morphological differences between different canopy layers were studied in 45–55-year-old trees in a Myrtillus site type forest stand. A significant variation was revealed in the biomass and growth of pine needles and shoots, density of needles, and number of buds on shoots between different canopy layers. The mass and length of shoots depend significantly on the content of N, K, and Ca in spring, before budbreak. In autumn, when growth has stopped, the content of nutrients plays a less significant role.
Key words: Pinus sylvestris L., partitioning of nutrients, morphology.
History of ice research in the Baltic Sea along the Estonian coast; 173–183
Abstract. The oldest records about ice along the Estonian coast, found in the Tallinn Town Archives, date from the 14th century. Regular observations were organized since the 1860s with a network of observation stations established at coastal lighthouses. Information about ice conditions was recorded in journals, preserved to the present day in the archive of the Estonian Meteorological and Hydrological Institute. These data have been used in many studies and scientific publications.
Key words: Baltic Sea, ice conditions, historical information, regular ice observations.
Meiobenthos in some Estonian small stratified lakes; 184–203
Abstract. At least 120 animal taxa were found in the corer samples taken from sediment in contact with the metalimnion and adjacent water layers in 10 small Estonian lakes. The bulk of them belonged to small individuals of macrobenthic taxa (pseudomeiobenthos) or to plankton. The proportion of eumeiobenthos (Nematoda, Turbellaria, Hydra, Ostracoda, Harpacticoida), and even their frequency, were low. Inclusion of meiobenthic animals found on the sieve with a mesh size of 0.15 mm increased the abundance of total zoobenthos by an order of magnitude compared with the abundance of the macrobenthos picked out without any magnification. Their contribution to the biomass, on the contrary, was insignificant. No distinct metalimnion-related peculiarities were found in zoobenthos. The diversity, number, and biomass of animals usually decreased with increasing depth, although differences were observed for different lakes and years. Only planktic cyclopoids, which spend some part of their life in bottom sediment, were sometimes very abundant at various depths, including the anoxic profundal. Cyclopoids were most often the dominant group in meiobenthos. Among the studied lakes, the poorest both in macro- and meiobenthos was Lake Holstre Linajärv. Lake Verevi was the richest in 1999–2000, in the period of the reconstruction of a swimming pool. A similar taxonomic content and depth distribution of meiobenthos have been found in several lakes of Latvia and Belarus. Northwards, in the small lakes of the Karelian Isthmus and Finland, as well as in some less stratified Masurian lakes, the share of eumeiobenthos is much higher, not to mention Lake Ladoga. In neighbouring large Lake Pihkva (Pskovskoe), eumeiobenthos is very rich on sandy bottom while pseudomeiobenthos becomes more important on mud.
Key words: fauna, zoobenthos, abundance, biomass, small lake, stratification, depth zone.
Land snails in Estonian forests: numbers and species richness; 204–216
Raivo Mänd, Tiina Talvi, Annelie Ehlvest, and Piret Kiristaja
Abstract. A drastic decline in land snail populations has been revealed in the oligotrophic areas of acidified regions of Europe. Since snail shells are an important calcium source for forest passerines, this decline causes severe reductions in forest passerine reproductive rates. In Estonia, about 40% of all woodlands consist of pine forests on poor, naturally acidic soils. It has been shown that birds breeding in such forests suffer calcium deficiency. A research project was carried out to estimate the current situation in Estonian forest land snail populations. This was the first large-scale quantitative investigation of forest snail fauna in the eastern Baltic area. Data about the abundance and species richness of snails are presented by geologically different regions and forest types of Estonia. The effect of industrial forest liming, occurring near some big oil-shale and cement works, was studied. Our data confirm that the number of snails in a substantial portion of Estonian forests is very low, and therefore birds breeding there may be vulnerable to possible increases in acidification. However, atmospheric pollution with calcareous materials in some ecologically problematic industrial regions seems to compensate for calcium deficiency for snail populations.
Key words: land snails, species diversity, forest, calcium shortage, pollution.
Recent distribution of Aglaothamnion roseum (Rhodophyta) in Estonian coastal waters, NE Baltic Sea; 217–221
Kaire Torn and Helen Orav
Abstract. Macrophytobenthos was studied in the Estonian coastal sea. An overview about the historical distribution data of a rare red alga Aglaothamnium roseum is given. In recent years A. roseum was found at three different sites in the southern coastal sea of Saaremaa Island – near the Kaugatuma Cliff, in Kuressaare Bay, and at two different sites of Kõiguste Bay.
Key words: Aglaothamnion, Baltic Sea, distribution, macrophytobenthos.
Instructions to authors; 222–224