How warm? How wet? Hydroclimate reconstruction of the past 7500 years in northern Carpathians, Romania

As natural and anthropogenic ecosystems are dependent on the local water availability, understanding past changes in hydroclimate represents a priority in research concerning past climate variability. Here, we used testate amoebae (TA) and chironomid analysis on a radiocarbon dated complex of small pond and peat bog sediment profiles from an ombrotrophic bog (Taut Muced, northern Carpathians, Romania) to quantitatively determine major hydrological changes and July air temperature over the last 7500 years.Wet mire surface conditions with a pH between 23 and 4.5 were inferred for the periods 4500-2700 and 1300400 cal yr BP by the occurrence of Archerella flavum, Amphitrema wrightianum and Hyalosphenia papilio. Dry phases in mire surface conditions and a pH between 2.5 and 5 were inferred for 7550-4500, 2750-1300 and 0 cal yr BP-present by the dominance of Nebela militaris, Difflugia pulex and Phryganella acropodia. The quantitative reconstruction of mean July temperature based on the chironomid communities suggests low summer temperatures for the periods 6550-5600, 4500-3150 and 1550-600 cal yr BP, while periods of slightly higher summer temperatures were observed for 5600-4500,3150-1550 and 100 cal yr BP-present. There is a generally good agreement between drier phases of the peat surface conditions with higher July temperature, suggesting that temperature may have been a controlling factor for water table fluctuation.Our quantitative reconstructions, among the first for central eastern Europe, show a relatively good agreement with other palaeohydrological studies from central eastern Europe, but contrast with others estimates from north-west Europe. Another important aspect of our study is that it provides valuable information on changes in local hydrology and the potential effect of the mean summer temperature over these changes. (C) 2017 Elsevier B.V. All rights reserved

Fire hazard modulation by long-term dynamics in land cover and dominant forest type in eastern and central Europe

Wildfire occurrence is influenced by climate, vegetation and human activities. A key challenge for understanding the risk of fires is quantifying the mediating effect of vegetation on fire regimes. Here, we explore the relative importance of Holocene land cover, land use, dominant functional forest type, and climate dynamics on biomass burning in temperate and boreo-nemoral regions of central and eastern Europe over the past 12 kyr. We used an extensive data set of Holocene pollen and sedimentary charcoal records, in combination with climate simulations and statistical modelling. Biomass burning was highest during the early Holocene and lowest during the mid-Holocene in all three ecoregions (Atlantic, continental and boreo-nemoral) but was more spatially variable over the past 3–4 kyr. Although climate explained a significant variance in biomass burning during the early Holocene, tree cover was consistently the highest predictor of past biomass burning over the past 8 kyr. In temperate forests, biomass burning was high at ~ 45% tree cover and decreased to a minimum at between 60% and 70% tree cover. In needleleaf-dominated forests, biomass burning was highest at ~60 %–65%tree cover and steeply declined at > 65% tree cover. Biomass burning also increased when arable lands and grasslands reached ~15 %–20 %, although this relationship was variable depending on land use practice via ignition sources, fuel type and quantities. Higher tree cover reduced the amount of solar radiation reaching the forest floor and could provide moister, more wind-protected microclimates underneath canopies, thereby decreasing fuel flammability. Tree cover at which biomass burning increased appears to be driven by warmer and drier summer conditions during the early Holocene and by increasing human influence on land cover during the late Holocene. We suggest that longterm fire hazard may be effectively reduced through land cover management, given that land cover has controlled fire regimes under the dynamic climates of the Holocene

Research and Science Today No. 1(5)/2013

Research and Science Today Journal is a publication founded in 2011 and it is dedicated to the students of all levels (license, master and doctoral) of faculties in the country and abroad. We want to offer the participants the opportunity to present their scientific works in the following areas: Social Sciences, Economic Sciences, Legal Sciences, Humanities, Education Sciences, Engineering, Medicine and Sport. This journal provides students the opportunity to create and/or to improve their abilities to write scientific papers. So each appearance (two appearances per year at which we can add supplements) contains a number of papers written by students, masters and doctoral from the faculties from the country or/and abroad. The journal promotes original studies contributing to the progress of knowledge and it is motivated by the need to address issues of theory and practice in the areas mentioned above

Research and Science Today No. 1(5)/2013

Research and Science Today Journal is a publication founded in 2011 and it is dedicated to the students of all levels (license, master and doctoral) of faculties in the country and abroad. We want to offer the participants the opportunity to present their scientific works in the following areas: Social Sciences, Economic Sciences, Legal Sciences, Humanities, Education Sciences, Engineering, Medicine and Sport. This journal provides students the opportunity to create and/or to improve their abilities to write scientific papers. So each appearance (two appearances per year at which we can add supplements) contains a number of papers written by students, masters and doctoral from the faculties from the country or/and abroad. The journal promotes original studies contributing to the progress of knowledge and it is motivated by the need to address issues of theory and practice in the areas mentioned above

Middle to Late Holocene vegetation shifts in the NW Transylvanian lowlands (Romania)

The Iaz peat bog, located in northwestern Transylvania at 300 m a.s.l., was cored to study the Middle to Late Holocene vegetation shifts in the area. The pollen record is supported by seven 14C datings. The base of the sequence starts in the Middle Holocene, when the outer woodlands were dominated by Corylus avellana together with other components of the Quercetum mixtum. The local establishment of Carpinus betulus occurred at 5700 cal. yr BP with maximum values at around 4900 cal. yr BP. At 4800 cal. yr BP, Fagus sylvatica became locally established and expanded, possibly as a result of moist climatic conditions and dominated the mesothermophilous woodlands from 4300 cal. yr BP onwards. During the periods of greater moisture, the deciduous forest was overgrown by the hygrophilous Alnus glutinosa belt. Indications of human activities in the area were recorded since 6300 cal. yr BP, when Cerealia and Secale pollen and other ruderal taxa start to appear regularly throughout the sequence. Although intense at times, the anthropogenic factor only played a major role in the vegetation changes during the last 635 years

Middle to Late Holocene vegetation shifts in the NW Transylvanian lowlands (Romania)

The Iaz peat bog, located in northwestern Transylvania at 300 m a.s.l., was cored to study the Middle to Late Holocene vegetation shifts in the area. The pollen record is supported by seven 14C datings. The base of the sequence starts in the Middle Holocene, when the outer woodlands were dominated by Corylus avellana together with other components of the Quercetum mixtum. The local establishment of Carpinus betulus occurred at 5700 cal. yr BP with maximum values at around 4900 cal. yr BP. At 4800 cal. yr BP, Fagus sylvatica became locally established and expanded, possibly as a result of moist climatic conditions and dominated the mesothermophilous woodlands from 4300 cal. yr BP onwards. During the periods of greater moisture, the deciduous forest was overgrown by the hygrophilous Alnus glutinosa belt. Indications of human activities in the area were recorded since 6300 cal. yr BP, when Cerealia and Secale pollen and other ruderal taxa start to appear regularly throughout the sequence. Although intense at times, the anthropogenic factor only played a major role in the vegetation changes during the last 635 years

Late Holocene palaeohydrological changes in a \u3ci\u3eSphagnum\u3c/i\u3e peat bog from NW Romania based on testate amoebae

This paper investigates the possibility of reconstructing the palaeohydrological changes in an active Sphagnum peat bog from north-western Romania using testate amoebae fauna and organic matter content determined by loss on ignition (LOI). In total 28 taxa of testate amoebae were identified of which 11 were frequent enough to present a remarkable ecological significance. Based on the relative abundance of these taxa nine zones were identified, crossing from very wet to dry climate conditions. The wet periods identified are characterized by taxa like Centropyxis cassis, Amphitrema flavum and Hyalosphenia papilio, while in the dry periods Difflugia pulex and Nebela militaris thrive. We showed that combining qualitative information regarding hydrological preferences with the quantitative percentage data from the fossil record it is possible to obtain information regarding major surface moisture changes from the peat bog surface. Furthermore we identified a link between distribution of testate amoebae assemblages, organic matter variation and minerogenic material

Late Holocene palaeohydrological changes in a Sphagnum peat bog from NW Romania based on testate amoebae

This paper investigates the possibility of reconstructing the palaeohydrological changes in an active Sphagnum peat bog from north-western Romania using testate amoebae fauna and organic matter content determined by loss on ignition (LOI). In total 28 taxa of testate amoebae were identified of which 11 were frequent enough to present a remarkable ecological significance. Based on the relative abundance of these taxa nine zones were identified, crossing from very wet to dry climate conditions. The wet periods identified are characterized by taxa like Centropyxis cassis, Amphitrema flavum and Hyalosphenia papilio, while in the dry periods Difflugia pulex and Nebela militaris thrive. We showed that combining qualitative information regarding hydrological preferences with the quantitative percentage data from the fossil record it is possible to obtain information regarding major surface moisture changes from the peat bog surface. Furthermore we identified a link between distribution of testate amoebae assemblages, organic matter variation and minerogenic material

How warm? How wet? Hydroclimate reconstruction of the past 7500 years in northern Carpathians, Romania

As natural and anthropogenic ecosystems are dependent on the local water availability, understanding past changes in hydroclimate represents a priority in research concerning past climate variability. Here, we used testate amoebae (TA) and chironomid analysis on a radiocarbon dated complex of small pond and peat bog sediment profiles from an ombrotrophic bog (Taut Muced, northern Carpathians, Romania) to quantitatively determine major hydrological changes and July air temperature over the last 7500 years.Wet mire surface conditions with a pH between 23 and 4.5 were inferred for the periods 4500-2700 and 1300400 cal yr BP by the occurrence of Archerella flavum, Amphitrema wrightianum and Hyalosphenia papilio. Dry phases in mire surface conditions and a pH between 2.5 and 5 were inferred for 7550-4500, 2750-1300 and 0 cal yr BP-present by the dominance of Nebela militaris, Difflugia pulex and Phryganella acropodia. The quantitative reconstruction of mean July temperature based on the chironomid communities suggests low summer temperatures for the periods 6550-5600, 4500-3150 and 1550-600 cal yr BP, while periods of slightly higher summer temperatures were observed for 5600-4500,3150-1550 and 100 cal yr BP-present. There is a generally good agreement between drier phases of the peat surface conditions with higher July temperature, suggesting that temperature may have been a controlling factor for water table fluctuation.Our quantitative reconstructions, among the first for central eastern Europe, show a relatively good agreement with other palaeohydrological studies from central eastern Europe, but contrast with others estimates from north-west Europe. Another important aspect of our study is that it provides valuable information on changes in local hydrology and the potential effect of the mean summer temperature over these changes. (C) 2017 Elsevier B.V. All rights reserved