Content of the Volume 30.
Körmöczi, L.: 30 years of the ecological journal Tiscia
Virágh, K. and Bartha, S. (1996): The effect of current dynamical state of a loess steppe community on its responses to disturbances. - Tiscia 30, 3-13.
Abstract. The impact of site history and current dynamical state of a loess steppe grassland community on its coenological changes caused by different disturbances were studied in permanent plots. Disturbance agents applied were the enclosure by fence and the resumed grazing. We investigated the coenological responses to grazing and lack of this management of 2 stands of a Pulsatillo-Festucetum rupicolae community with different structure, dynamical status and management history. One type of these stands was a species rich, well-organized "intact" stand, usually avoided by sheep. It was considered to be in a dynamically stable state. The other stand was a slightly degraded one, which was more frequented by the animals. This Festuca pseudovina type of the Pulsatillo- Festucetum rupicolae association had been used as a grazing land for a long time, but the regular grazing was stopped about 10 years before our experiments started. Our results demonstrated that effects of enclosure were entirely different in a relatively intact semi-natural dense community and in a formerly grazed degraded community. We pointed out the great importance of site management history and current coenological and dynamical states of the community on its responses to fencing. Drastic coenological changes (significant decrease in species richness, vegetation cover and living phytomass) were detected in a very short time-period (3 years) when sheep were excluded in the formerly regularly grazed stand, while only slight floristic and coenological changes could be measured in the relatively "intact" community even for several years (9 years) after fencing. Our results of resuming grazing experiment in the degraded stand showed that the species richness, species diversity, average vegetation cover, as well as the living and dead parts of plant biomass were relatively unchanged in the slightly grazed plots. It was concluded that slight grazing management in a traditionally grazed old meadow was necessary for maintaining its floristic composition and coenological state. We emphasized that relative importance of grazing also differred between various types of a grassland community and depended on their current floristic and dynamical states and the past grazing pressures.
Keywords: sheep grazing, fencing, site history, coenological changes,
diversity
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Molnár, Zs. and Biró, M. (1996): Vegetation history of the Kardoskút area (S.E. Hungary) I.: Regional versus local history, ancient versus recent habitats. - Tiscia 30, 15-25.
Abstract. Reconstruction of past events and states provides useful information for the explanation of present vegetation patterns. Based on data from historical documents, old survey maps, the living memories of inhabitants and a detailed survey of present vegetation, the local history of the Kardoskút steppe was drawn and compared with the regional history of the Great Hungarian Plain. Special emphasis was put on distinguishing ancient and recent loess grasslands, alkali steppes and woodlands. The Kardoskút steppe landscape was shaped mainly by nomadic animal husbandry till 1847. From that time till the 1970's, fine scale capitalist small-farm agriculture was the main landscape forming force. Cultivation was strongly controlled by soil conditions. Since the 1970's, the combination of a socialist planned economy and nature conservation management induced considerable changes in grassland distribution and quality.
Keywords: 18-20th centuries, map series analysis, landscape history.
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Molnár, Zs. (1996): Vegetation history of the Kardoskút area (SE. Hungary) II.: The lake Fehér-tó in the last 200 years. - Tiscia 30, 27-34.
Abstract. Reconstruction of past vegetation changes provides useful information for the understanding of present vegetation. Based on historical data, old aerial photos and maps, a detailed vegetation survey, and the vegetation description by György Bodrogközy from the 1960's, the vegetation history of the lake Fehér-tó at Kardoskút for the last 200 years was drawn. Historical data indicates that the lake remained in a near-natural state till the late 1970's. Since 1980, climatic drought has induced fundamental vegetation changes which differ in the 3 parts of the lake, probably as a consequence of differences in geological history. Predictions about the future of the lake vegetation, based on historical data and comparisons with other drying alkali lakes, are also given.
Keywords: drought, nature conservation, repeated vegetation mapping,
succession.
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Pujin, V., Djukic, N., Maletin, S., Miljanovic, B. and Ivanc, A. (1996): Changes of zoocoenotic structure in lower reach of river Tisza. - TISCIA 30, 35-38.
Abstract. Hydrotechnical constructions on rivers Danube (Hydroelectric plant Djerdap I and II) and Tisza (Dam Novi Beèej), as well as general industrial development in the Tisza valley caused deterioration of physico-chemical quality of water of river Tisza. The slowing down of its flow and increased inflow of waste water led to a decrease in dissolved oxygen concentration and affected the structure of zoocoenosis. The number of zooplankton species characteristic of smooth waters and tolerant to oxygen depletion increased. These conditions affected, as well, both the composition of bottom fauna and ichthyofauna. Analysis of Oligochaeta community has indicated a sharp reduction in the number of species and decrease in the numbers. The abundance of sterlet and predator fish species has been decreasing as well as phytophils. A slow decrease in carp population occurred despite a permanent stocking with fingerlings. Special changes appear in fish community in relation to introduced species, especially Prussian carp. The decrease in dissolved oxygen concentration below biological minimum caused fish dying in recent years .
Keywords: zooplankton,Oligochaeta, ichthyofauna, hydroecosystem, degradation
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Petrov, B. and Cvetkovic, D. M. (1996): Seasonal dynamics of Triops cancriformis (Bosc, 1801) (Crustacea, Branchiopoda) in the Banat province in Yugoslavia. - Tiscia 30, 39-43.
Abstract. At the territory of Banat province, in the southern part of the Pannonian Plain, about 100 kilometers north of Belgrade, the appearance and seasonal dynamics of a bisexual population of Triops cancriformis over the period 1991-1995 was observed. A population of T. cancriformis appears regularly, i. e. every year when ephemeral ponds are formed. Hatching takes place between the beginning of March and the beginning of April when average temperature varies between 7 and 10 oC. Sexual maturity is reached after one month. A life span of two months is registered. During one year, several generations may appear at one month intervals, i. e. when sexual maturity of a previous one is reached. Up to three generations may be present simultaneously. Males are present during the whole season. They make 15-40 % of the population.
Key words: Crustacea, Branchiopoda, bisexual population of Triops cancriformis,
ephemeral ponds
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Tomanovic, C., Brajkovic, M., Krunic, M. and Stanisavljevic, Lj. (1996): Seasonal dynamics, parasitization and colour polymorphism of the pea aphid, Acyrthosiphon pisum (Harris) (Aphididae, Homoptera) on alfalfa in the south part of the Pannonian area. - Tiscia 30, 45-48.
Abstract. Over the period 1992 to 1994, individuals of the pea aphid, Acyrthosiphon pisum were collected in the localities Kovilovo and Sur(in near Belgrade, in order to analyze its seasonal dynamics, colour polymorphism and parasitization. Samples of pea aphid were collected by sweeping inside the field, and every sample contained ten subsamples. Aphid parasites were obtained by rearing aphids. We found that parasite spectrum of the pea aphid in Yugoslavia includes four species: Aphidius ervi, A. eadyi, A. picipes and Praon barbatum. Dominant species was A. ervi. We have also observed the influence of parasitization on the seasonal dynamics of the pea aphid. The greater the autumn parasitization of the pea aphid population, the greater the number of emerged parasites next spring which also means the greater the parasitization of the pea aphid population. If the autumn parasitization is low, the next spring parasitization of the population is also low. Colour polymorphism is an important self-regulating mechanism of pea aphid population. We found that neither of the four parasite species showed preference to any colour form of pea aphids.
Key words: pea aphid, parasitoid, population density, colour forms.
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Guti, G. (1996): Species composition of juvenile (0+) fish assemblages in the Szigetköz floodplain of the Danube. - Tiscia 30, 49-54.
Abstract. Samples of juvenile fishes were collected with a point abundance sampling strategy using electroshocker at 27 sites in the Szigetköz floodplain in late summer 1992. Species composition of assemblages was examined and related with the habitat types (parapotamon, plesiopotamon) by principal component analysis. From the 27 species recorded the juveniles of 21 species were found. The distribution of juvenile fishes was correlated with the general flowing conditions of the backwaters and their actual connectivity with the main channel.
Keywords: parapotamon, plesiopotamon, backwater, electrofishing, point
abundance sampling, principal component analysis
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Körmöczi, L. (1996): 30 years of the ecological journal Tiscia. - Tiscia 30, 55-64.
Abstract. Tiscia, an ecological journal, succeeded the 30th volume.
A short history of three decades is reported. Major changes and preferences
are also summarized, and the content of the previous 29 volumes is listed.
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