Juliana Atanassova

Predictability of biomass burning in response to climate changes

Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo- fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.

Palaeoecological setting of the western Black Sea area during the last 15000 years

Analysis of pollen, dinoflagellate cysts and lithology was carried out on ten cores from the western deep Black Sea and combined with radiocarbon dating to reconstruct the vegetation, climate and palaeoecological conditions. All the cores record a consistent sequence of Lateglacial and early Holocene steppe vegetation, which persisted until about 7100-7500 yr BP when Quercus, Corylus, Tilia and other temperate trees expanded, at about the same time as the influx of Mediterranean waters that resulted in sapropel deposition in the deep Black Sea. The sequence implies dry climatic conditions and a low level of the Black Sea during the early Holocene.

Chronological framework for the Lateglacial pollen and macrofossil sequence in the Pirin Mountains, Bulgaria: Lake Besbog and Lake Kremensko-5

The sediments of numerous cirque lakes in the Pirin Mountains have yielded several generalized pollen diagrams, but low stratigraphic and temporal resolution has hampered detailed reconstruction of the vegetational history, especially for the Lateglacial. New pollen and macrofossil analyses of high stratigraphic resolution combined with well-controlled time-depth curves for Lake Besbog and Lake Kremensko-5 now permit the firm identification of the Lateglacial interstadial interval (Bølling-Allerød), dated at 13.8-12.6 ka cal. BP at Besbog and 14.1-12.8 ka cal. BP at Kremensko-5 and correlated with the Greenland Interstadial GI-1 (14.5-12.6 ka cal. BP). Macrofossil analyses indicate that during the Bølling-Allerød period Betula and Juniperus occurred around the lakes (at 2124-2250 m a.s.l). Following the Younger Dryas a Betula woodland covered the mountains between 1900 and 2250 m in the early Holocene. Because of higher summer insolation at this time, the temperate deciduous forest reached up to 1900 m, or 800 m above their present limit, producing a regional pollen rain that dominated pollen deposition in the cirque lakes. After about 7000 cal. yr BP conifer forests replaced the birch woodland at middle and high elevations.

Palynological study of Holocene sediments from Lake Doirani in northern Greece

A palynological investigation was conducted on two cores with Holocene sediments collected from the northeastern littoral part of the border Lake Doirani in northern Greece. The radiocarbon dates indicated that the analyzed sediments accumulated during the last 5000 yrs. The pollen-stratigraphic record revealed the environmental changes in the catchment area, starting from a natural undisturbed landscape to one modified by increasing anthropogenic influences. The tree vegetation dominated by Quercus woods in the lowlands and byPinus, Abies, and Fagus at higher altitudes, lasted for the period 2900 - 830 cal. B.C. Subsequently it was replaced by xerothermic herb and tree vegetation as a result of intensive human activity - and farming and stock-breeding. The accumulation of sediments with more sand and gravel in historical time was the result of increased erosion.

Characteristics of Honey from Serpentine Area in the Eastern Rhodopes Mt., Bulgaria

Honey samples collected during 2007–2010 from serpentine and non-serpentine localities in the Eastern Rhodopes Mt. (Bulgaria) were characterized on the basis of their pollen content by qualitative melissopalynological analysis and physicochemical composition. Water content, pH, electrical conductivity, macroelements—K, Ca, Mg, P, and microelements—As, Cd, Co, Cr, Cu, Fe, Mn, Na, Ni, Pb, and Zn were determined after the Harmonised Methods of the International Honey Commission and ICP-AES method. The results from serpentine honey samples were compared with data from bee pollen collected from the same serpentine area. Different elements have different concentrations in honey from the same botanical type even collected from the same geographical region, same locality, and same beehive but in different vegetation season. The elements Mg, Mn, Ni, and P contribute mostly for separation of the serpentine honey samples based on measured elemental concentrations and performed principal component analysis. The element concentrations were higher in bee pollen and above the permissible limits for the toxic metals Cd and Pb. No specific indicator plant species was found for identification of the geographical origin of serpentine honey in relation to the forage of bees.

Plant economy and vegetation of the Iron Age in Bulgaria: archaeobotanical evidence from pit deposits

Major social and economical changes occurred in human societies during the Iron Age of Southeastern Europe: increasing structuring of societies, intensifying production and metal technologies and the establishment of a market economy. However, the related plant economy of the region is still poorly studied and understood. The Iron Age ‘pit field sites’ (groups of pits distributed over a certain area) in south-eastern Bulgaria were recently intensively excavated, and their study provides rich archaeobotanical assemblages, which are used for filling this gap in our knowledge. The current study presents the archaeobotanical information from 196 flotation samples from 50 Iron Age pits. The results show a wide range of annual crops, the most important of which seem to be hulled wheats (mainly einkorn), barley and also millet. A variety of pulses and fruits is retrieved, each in small quantities. Some species like Olea europaea and Cucumis melo are an indication for contacts with adjacent regions (especially the Mediterranean area). The archaeobotanical assemblages also documented the environment and land use, revealing the exploitation of a variety of habitats like cropland, open grassland, shrub land and wetland. The archaeobotanical analyses of the Iron Age pit fields show that this type of structures can be an important source of information on the Iron Age plant economy in the region.

Significant parameters of Bulgarian honeydew honey

Three main physico-chemical parameters (moisture content, pH, and electrical conductivity), 19 elements contents (K, Ca, Mg, P, S, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Na, Ni, Pb, Sr, V, and Zn) and microscopic characteristics of 30 honeydew honey samples from Bulgaria were evaluated. The most abundant elements were K, P, Ca and Mg in the honeydew honey investigated and low concentrations of toxic elements and heavy metals were established. The electrical conductivity – one of the most important parameters for honeydew honey, exceeded 0.8 mS*cmˉ¹. The honeydew index in Bulgarian honeydew honey varied widely and its values were often below 3.