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Nematode communities along the transect shelterbelt - ecotone - crop field

Dmowska E.

Polish Journal of Ecology

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2007

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Vol. 55, nr 4

665-680

EN

The study was carried out in western Poland (Turew region) in two shelterbelts of different age (the younger - 6 years old and the older - 11 years old) planted cross croplands, in adjacent field and in the field located in deforested area (control field). Soil samples were taken twice: in the autumn and spring from the centre of each shelterbelt, from the ecotone, and in the field at a distance of 15 and 50 m from the edge of the shelterbelts. The density of nematode communities fluctuated unpredictably, in autumn it was very low and ranged from 276 to 641 x 10[^3] in spring it ranged from 388 to 1931 x 10[^3] individuals per 1 m[^2]. Most numerous trophic groups were: bacterivores, fungivores and obligate plant feeders, while facultative plant feeders, omnivores and predators achieved low level. The abundance of predators in older shelterbelt was significantly (P [less-than or equal to] 0.05) higher than that in the younger one and decreased with increasing distance from the shelterbelt towards the field. The communities in shelterbelt and its ecotone were more diverse, which was reflected by the higher number of genera (19-31) and higher values of Shannon-Wiener diversity index H'(3.3 - 4.0), than those in the fields where the number of genera ranged from 15 to 25 and Shannon-Wiener diversity index H' ranged from 2.5 to 3.5. In the younger shelterbelt and in the control field the soil food-web assessed with indices derived from analysis of nematode communities was considered as composed mainly of basal components, i.e. cosmopolitan species feeding on bacteria and fungi occurring everywhere even in degraded environments. While the web in older shelterbelt was consisted mainly of enrichment components, i.e. bacteria feeding species of very short life cycle, with high food requirements which occur in the environment rich in bacteria. The values of Channel Index which informs about the predominant pathway of decomposition (through bacteria or fungi) showed that in majority of sites bacterial processes predominated. Only in the older shelterbelt the participation of fungal decomposition channel was higher (>50%) and increased with increasing distance from the shelterbelt towards the centre of the field. The results of Correspondence Analysis showed that first two axis explained 40.3% of the variance. The generic composition of nematode communities in the 11 years old shelterbelt differed from that in the 6-years old shelterbelt. Nematode communities inhabiting the ecotone of younger shelterbelt were very similar to the communities in the shelterbelt, while the communities in ecotone of older shelterbelt differed from those in the shelterbelts. Nematode communities inhabiting the control field were similar to those inhabiting the field adjacent to younger shelterbelt.

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Factors describing the distribution of the zooplankton community in the Gulf of Finland in the context of interactions between native and introduced predatory cladocerans

Pollumäe A., Kotta J.

Oceanologia

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2007

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No. 49 (2)

277-290

EN

Mesozooplankton communities were studied monthly at six sites in the Gulf of Finland during six ice-free seasons. The abundances of different zooplankton taxa were related to temperature, salinity, eutrophication level (total nitrogen and phosphorus), phytoplankton Chl a and density of predatory cladocerans, including the non-indigenous Cercopagis pengoi and the native Leptodora kindtii. The results indicated that variability in the zooplankton communities was correlated not only with predation by mesozooplankton but also with bottom-up effects. Predation by the non-indigenous C. pengoi may significantly affect the dynamics of Cladocera and Rotatoria in the Gulf of Finland during the summer season.

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Nematodes colonizing power plant ash dumps. 2, Nematode communities in ash dumps covered with turf - effect of reclamation period and soil type

Dmowska E.

Polish Journal of Ecology

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2005

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Vol. 53, nr 1

37-51

EN

Changes in the below-ground system of ash dumps reclaimed by covering with turf were estimated using parameters and indices based on analysis of nematode communities. Higher trophic diversity, higher values of Maturity Index (MI), and higher complexity of food-web structure were expected when reclamation proceeded. The study was carried out for three years in chronosequences of ash dumps. Two of the dumps were reclaimed shorter and were studied between the 2tnd and 5th year of reclamation, the first one was reclaimed by covering with turf with mineral soil (S-M), the second one with turf with organogenic soil (S-O). The third ash dump reclaimed in longer time, covered with turf with organogenic soil was studied between the 8th-11th year of reclamation (L-O). Until the fourth year of reclamation S-O site provided better conditions for the development of nematodes than S-M site; trophic diversity and MI were higher in S-O site in comparison with S-M site. Later on most parameters and indices were similar in S-M and S-O site. Longer reclamation resulted in higher total abundance, higher abundance of bacteriovores, plant feeders and omnivores, and also higher biomass of bacteriovores and plant feeders. However, changes in the below-ground system of reclaimed ash dumps were very slow because even after 11 years of reclamation the ash dump had the features of a degraded environment.

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Greenland whales and walruses in the Svalbard food web before and after exploitation

Węsławski J.M., Hacquebord L., Stempniewicz L., Malinga M.

Oceanologia

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2000

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No. 42 (1)

37-56

EN

Between 1600 and 1900 two numerous and ecologically important large marine mammals were extirpated in the Svalbard archipelago. These were the pelagic-feeding Greenland whale (Balaena mysticetus) and the benthic-feeding walrus (Odobaenus rosmarus rosmarus), the initial stocks of which prior to exploitation are estimated to have numbered approximately 46 000 and 25 000 animals respectively. Their annual food consumption at that time is estimated to have been some 4 million tons of plankton and 0.4 million tons of benthic organisms. Assuming that the primary and secondary production of the shelf/coastal ecosystem in the 16th century (before the peak of the Little Ice Age) was similar to that of the present day, the authors have concluded that a major shift in the food web must have occurred after the Greenland whales and walruses were eliminated. Planktonivorous seabirds and polar cod (Boreogadus saida) very probably took advantage of the extirpation of the Greenland whales, while eiders (Somateria mollissima) and bearded seals (Erignathus barbatus) benefited from the walrus's extinction. In turn, the increased amount of pelagic fish provided food for piscivorous alcids and gulls, and may have given rise to the huge present-day seabird colonies on Svalbard.

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Long term effects of liming in a humic lake : ecosystem processes, biodiversity, food web functioning (Lake Flosek, Masurian Lakeland, Poland)

Hillbricht-Ilkowska A., Dusoge K., Ejsmont-Karabin J., Jasser I., Kufel I., Ozimek T., Rybak J.I., Rzepecki M., Węgleńska T.

Polish Journal of Ecology

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1998

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Vol. 46, no 4

347-415

EN

The chemical composition of water and bottom sediments, productivity and decomposition rates as well as the biodiversity and food web functioning (organic suspension, edible algae, bacterio-detrivores, herbivores, grazers, predators) in plankton and benthos were analysed in humuc, weakly acid, mid-forest lake surrounded by peatmoss Sphagnum (Lake Flosek, Masurian Lakeland, Poland) before and 1-4 and 20-23 years after application of powdered lime. Calcium content and pH in water and sediment raised permanently. High water quality variables were main-tained after liming (low production, algal biomass, chlorophyll and nutrient concentration, low release rate of phosphorus from the sediments). Decomposition rate of organic matter increased significantly. The species richness and diversity of algae, rotifers, crustacean and benthic invertebrates increased at least twice as well as the abundance of bacterio-detrivores in plankton (small rotifers) and benthos (chironomids) and herbivores (big daphnids, diaptomids) in plankton. The distinct succession in species composition was observed in many taxa. The predators like larvae of Chaoborus, cyclopids and predatory rotifers became very abundant after 20 years since liming. No evident peatmoss mat spreading over the lake table has been observed since liming but also no detrimental effect on peatmoss surrounding the lake. It was concluded that the moderate liming affects first of all the biodiversity of lake biota then it stimulates the mobilisation of the lake which eventually lead to the greater and more stable complexity of trophic links. The species-rich and top-down controlled food web was installed in the limed lake without interfering with high quality of lake waters (low-productive, high-transparent) and unique, natural values of its surroundings.However, a slight increase in nutrient concentration after 22-23 years was observed which could be related to more efficient recycling mechanism in lake (due to abundant big components in plankton and benthos) or to eutrophication.