Adam Walanus

High-resolution lacustrine record of the late glacial/holocene transition in central Europe

Abstract In this paper we present the high-resolution record of proxy climatic data in central Europe during the final stages of the last deglaciation, derived from the annually laminated sediments of Lake Gościaz (central Poland). The isotopic, palynological and other microfossil data confirm sudden changes of climate at the onset and termination of the Younger Dryas (completed within 150 and 70 years, respectively), in close agreement with the previous estimates derived from the polar ice cores and marine sediments. In the upper YD some amelioration of climate took place already about 600 years before the main YD/Preboreal transition. Counting of annual varves in the lake sediments allows a direct estimate of the duration of the Younger sDryas in central Europe; it lasted approximately 1640 years, substantially longer than suggested by previous estimates derived from laminated lake sediments and glacial varves, but agreeing with the radiocarbon calibration data obtained for Barbados corals. The calendar ages of the boundaries of the YD, 12,920 and 11,280 cal BP, are tentatively set.

Anthropogenic changes in the sediment composition of Lake Gości& aogon;ż (central Poland), during the last 330 yrs*

According to historical sources, the development of settlement around Lake Gości& aogon;ż during the last 330 yrs was intense at two time periods: the second half of the 1700s, and from ca. 1880 until 1944. The small farms were then abandoned, following which the lake surroundings were planted with forest trees. The presented study of human influence on the lake ecosystem and surrounding vegetation has been based on analyses of general sediment composition and its chemistry, pollen, Cyanobacteria, Chlorophyceae, Rotatoria, Cladocera, and a preliminary diatom survey. The history of human impact has been divided into four phases: 1. Phase of small local hamlets (before ca. 1770): The human impact was rather moderate then, but the cultivation of Canabis sativa, Secale cereale and later of Fagopyrum is evidenced from that time. 2. Phase of ‘Hollandii’ settlement (ca. 1770-1863). Its influence is indicated first by the recession of deciduous wood (Corylus, Carpinus) stands, which triggered drastic drop of calcium in sediments. The development of rural economy in the area, including, an extension of agriculture (Secale and other cereals, crucifers, potatoes), and animal breeding based partly on grazing in the forest, is evidenced only after 1820. 3. Phase of German colonization (1863-1944): In the early periods (before 1910) the pollen spectra do not document any essential change in the type of farming, however, a serious disturbance of the lake ecosystem and sediment chemistry is evidenced by the blooms of Araphidinae diatoms and Tetraedron minimum, a maximum frequency of Bosmina longirostris, disturbances of the regular spring blooms of Chrysophyceae, appearance of vivianite, distinct maxima of organic matter, potassium, and iron concentration in sediments and an increase of the sedimentation rate. An intensification of agricultural activities commenced around 1910; woods, including also pinewoods, were then heavily devastated, and farming extended on poor soils, what was symptomatic for the general poverty of population. Coincidently in the lake, Centriceae showed blooms, Araphidinae diatoms and Tetraedron minimum developed, and the content of potassium, iron and phosphorus increased substantially, indicating altogether rising eutrophication. 4. Phase of restoration of the natural landscape (after 1945): The farm degradation from ca. 1944 is very weakly expressed in pollen data, which show a substantial fall of farming indicators from 1953/6 only, when the whole area was used for forest plantation. It was accompanied by a certainly spontaneous development of Betula and Alnus woods, this process progressing till recent time. The gradual extinction of farming activity near Lake Gościąż was accompanied by abrupt changes in the lake ecosystem, expressed by the restored blooms of Chrysophyceae expansion of planktonic Cladocera, rapid decline of phosphorus and extinction of vivianite from sediments. As documented by the drop of Cu/Zn ratio, lake hypolimnion has been weakly oxidized since 1949, what was probably responsible for the drop of Fe and Mn content in sediments. Increasing strength of overturns affected preservation of laminae in sediments, which almost completely disappeared after 1966.

Description of the main Poaceae pollen season using bi-Gaussian curves, and forecasting methods for the start and peak dates for this type of season in Rzeszów and Ostrowiec Św. (SE Poland)

Grasses characteristically produce a huge amount of small pollen grains, which pose a risk to allergy sufferers. In many aerobiological studies, great variations in the behaviour of the grass pollen season are stressed. We state that in Rzeszów and Ostrowiec Sw. there is some regularity in the pattern of the main grass pollen seasons, which is clearly double-peaked. The aim of our work was to elaborate the algorithm which defines the main grass pollen season. Next, the null hypothesis was tested about the lack of difference between daily pollen concentrations and meteorological parameters. Grass pollen seasons were defined using the method of fitting two bell curves. The estimated grass pollen season is characterised by two periods of high or relatively high concentrations, separated by a period of low concentration. In order to investigate the time dependence of the correlation between pollen concentration and the weather parameters, the Gaussian-weighted correlation coefficient has been calculated. Maximum temperature, mean temperature and sunshine positively correlated with pollen concentrations, but relative air humidity and rainfall on the previous day had a negative effect. The temperatures of the second and third ten-day periods of April were the best independent variables for forecasting the beginning and peak dates of the main pollen seasons. An analysis of the results shows that the pattern of successive flowering in grass species and meadow cutting dates appear to be the factors which cause the characteristic bimodal behaviour of the grass pollen season.

Application of the Triple-Photomultiplier Liquid Spectrometer Hidex 300 Sl in Radiocarbon Dating

The Hidex 300 SL is a liquid scintillation analyzer with an automatic sample changer and a triple-photomultiplier tube detection assembly that registers triple- as well as double-coincidence spectra. In the triple mode, the background in the 14C window is 13.7 cpm (14C standard 30.8 cpm; =154.3 cpm/5.01), so the factor of merit equals 8.7. The triple-to-double coincidence ratio (TDCR) allows for determining the 14C counting efficiency, the quench level, and quench correction. However, in the case of very low-activity samples, which is the case even for modern 14C samples, the TDCR is not the best method for the correction of benzene impurities. We propose using the position (channel) of the right slope of the sample (14C) logarithmic pulse-height spectrum. In the case of near-background samples, the cosmic muon peak can be used instead. The Monte Carlo modeling of spectra gave the 14C level below which the muon peak is a better quench correction parameter than the position of the 14C spectrum. The spectrometer, with the proposed quench correction method, was tested with wood samples dated dendrochronologically. For 21 samples, there is no systematic bias observed, and the standard deviation of the age differences scaled by the Poisson errors is 1.24 ± 0.15, which means that the counting statistics account for 80% of the total variability (including sample preparation).

Possibilities for Reconstructing Radiocarbon Level Changes During the Late Glacial by Using a Laminated Sequence of Lake

Laminated sediments of Gościąz Lake can be used as an independent source of material for calibrating the radiocarbon time scale. The varve chronology is based on three long cores from the deepest part of the lake, with one additional core from the second deepest part. From pollen and Cladocera spectra and stable isotope and chemical content sequences, we have determined the Allerod(AL)/Younger Dryas(YD) and Younger Dryas/Preboreal(PB) boundaries in the three long cores with relatively good accuracy, and have tentatively defined the AL/YD boundary in the fourth core. The Younger Dryas period contains at least 1520 varves, with 980 varves in fragments well replicated in all four cores. The duration of the Younger Dryas as recorded in sediments of Gościąz Lake corresponds well to the duration derived from 230Th/234U and 14C dates on Barbados corals, but disagrees with estimates from Soppensee, Lake Holzmaar and Swedish varves. Two AMS dates of terrestrial macrofossils from the PB and YD periods seem to fit both the data obtained for Swiss lake sediments and Barbados corals.

A method of continuous examination of counting efficiency during measurements of natural radiocarbon by a CO2 filled proportional counter

Abstract The paper deals with a method of the control of counting gas purity and continuous examination of the counting efficiency during measurements of natural radiocarbon in carbon dioxide filled proportional counter. The described method is based on the registration of the number N of coincidence muon counts between the two sections of GM guard counters in addition to the commonly used recording of the number L of coincidence counts between the proportional counter and the guard counters taken as a whole. It has been shown that the ratio C = L / N depends only on the proportional counter performance and resembles its overall counting efficiency. The method was checked on three samples of inadequate purity measured in the Gliwice Radiocarbon Laboratory and the results have been found satisfactory.

Systematic Bias of Radiocarbon Method

Systematic bias of dates can became statistically significant regarding the growing global number of dates connected with the calibration curve plateau. For example, samples of true age in the span 800-700 BC are dated to be roughly 100 younger, on average. The curve of expected bias for a given age is presented. To avoid such a bias, the Bayesian paradigm probably must be modified in some way.

Comparison of TL, ESR and 14C dates of speleothems

Abstract A series of speleothems from the Magurska, Miȩtusia and Kasprowa Niznia Caves (Tatra Mts, S. Poland) have been dated using the 14C, TL and ESR methods. A method proposed by T. Goslar and H. Hercman was used to consider radioactive disequilibrium in the uranium series for dose rate calculation. A total of 17 samples were dated; a direct comparison of 14C dates with corresponding TL and ESR dates was possible for 8 samples, while simultaneous TL and ESR dates were available for 6 samples. There was general agreement in both groups. The results obtained were used to set up time boundaries on the last glaciation of the Tatra Mts and to reconstruct climatic changes in this area during the last 100 ka.

Information content of zero pollen counts in Holocene profiles

Percentage-based pollen diagrams display the relative proportions of various taxa in relation to a stated pollen sum. A zero count for a given palynological taxon, as recorded for a given sample, does not mean that the taxon was absent at the time and place represented by the sample, but only that the concentration of palynomorphs is, at most, below the detection limit of the method. Here we apply the statistical concept of the confidence interval to approach this problem. In general, observing zero counts, one can state that there is a 95% probability that the true average for the given sample is simply below 3.0. However, if the sample has a neighboring non-zero sample, the best-fit value for the expected number of counts is 0.6–0.7, as estimated in the statistical analysis of a data base of 39 pollen diagrams from the Carpathian mountains, with a combined total of 4304 pollen curves. We suggest applying the confidence intervals (for a zero as well any positive number of counts) in drawing pollen diagrams, in order to clearly indicate the measurement uncertainties connected with pollen counting.

Asháninka Palm Management and Domestication in the Peruvian Amazon

Palms are a natural resource that has been abundantly used by Amerindians for centuries. Only a few palm domestications have been reported in the American tropics, where there is great diversity of the Arecaceae family. We report the results of a survey combining ethnobotanical and ecological methods to study the past and present management and distribution of palms by the Asháninka indigenous people from the Tambo river region in the Peruvian Amazon. Our objectives were to document palm-related traditional ecological knowledge, to examine correlation between palm abundance and Asháninka management practices and social exchange of palm resources, and to address the question of how the Asháninka have modified palm diversity and distribution in their territory. We found that most palm species have multiple uses; the most intensively managed were palms that provide thatch, notably Attalea phalerata, Oenocarpus mapora and Phytelephas macrocarpa. Of these, Attalea phalerata was the most commonly cultivated and was found only in cultivated stands. Our results have implications for understanding the domestication of Attalea weberbaueri, which is a landrace within the Attalea phalerata complex. A closer understanding of this process would require morphometric and genetic methods to compare wild and managed populations.