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Dendrochronological and radiocarbon dating of subfossil wood from the Morava River basin

Kolář T., Rybníček M.

Geochronometria

2011

Vol. 38, no. 2

155-161

The paper deals with dendrochronological and radiocarbon dating of subfossil trunks found in the basin of the Morava River. The research into subfossil trunks had been conducted in the Czech Republic in the past but the research stopped in 2001. 160 records of measurements of subfossil, predominantly oak trunk samples, are preserved from that time. Three years ago the research was reo-pened and again the most trunks were found in the basin of the Morava River. 92 samples of oak trunks and 7 samples of other tree species (poplar, elm, maple, beech) were taken from selected sites. The samples were processed in compliance with the standard dendrochronological methodology. To date the samples, Czech, Austrian, Polish and German standard chronologies were used. In cases when the dendrochronological dating was unsuccessful, the samples were sent for radiocarbon dating. In total, 35 samples were dated, mainly by the radiocarbon method. Subfossil trunks from gravel pit Tovačov were dated and classified into 4 different periods, the oldest being from 2780-2190 BC. In Osek nad Bečvou, the samples were taken from two sites. Whereas from the 4 trunks taken in the riv-er channel each was from a different period, the trunks from the gravel pit come from 981-1015 AD. The trunks found in the Morava River basin near Strážnice were dated to the 10th-15th century. In the future, we expect to extend the amount of the acquired samples with the aim to create a link to the existing standard chronology or to create a long floating average tree-ring curve.

Phytoplankton of the morava river in the Czech Republic and Slovakia: past and present

Marvan P., Heteša J., Hindák F., Hindákowá A.

Oceanological and Hydrobiological Studies

2004

Vol. 33, No. 4

41--60

The amount of industrial waste released into the Morava River has decreased substantially since the late 1950s. This has led to a marked increase in phytoplankton abundance and species diversity. In the past, the Dyje River, a main right-side tributary of the Morava, served as a major source of planktonic algae for the lowermost stretch of the Morava River. At present, production and biological processes in the Nové Mlýny reservoirs significantly influence water quality. The quantity of phytoplankton has decreased but during hot summer periods the floating biomass of bloom forming Cyanophyta has increased significantly. The increase of colonial cyanophytes is an undesirable incidental phenomenon associated with the improvement of water quality in terms of allochthonous organic pollution. This was also promoted by the damming of the Dyje River in its lower floodplain area some fifteen years ago. Observations from 2002 indicate that a bloom of cyanophytes could soon also affect the middle stretch of the Morava. The lower stretch of the Morava supports a species-rich community of planktonic algae and diatoms, but above all, green flagellated and coccal algae. The Morava represents an important source of algal inoculums for the Danube and it contributes to the species diversity at the point where it enters the Pannonian Lowland. In this stretch of the river 25 genera with 58 species of cyanophytes and 181 genera with 634 species and infraspecific taxa of different groups of algae have been identified. Phytoplankton abundance has increased several times in comparison to the late 1950s. The highest values measured in 2002 were close to 100,000 cells per ml, and the chlorophyll–a concentration was 100 μg/l.