PŘEDBĚŽNÉ VÝSLEDKY STUDIA VZTAHU SUBFOSILNÍCH KMENŮ A FLUVIÁLNÍCH SEDIMENTŮ NA LOKALITÁCH OSEK NAD BEČVOU A TOVAČOV-ANNÍN

There are many subfossil trunks in natural outcrops and especially in gravel pits along the Morava and Bečva rivers. Many of them have their original position in gravel deposits but close to position of quite rapid change into the flood loam especially on the base alternating with sandy layers. More subfossil trunks were sampled at the Osek nad Bečvou locality, partly just from the outcrops on the river Bečva bank and others from small trunk dump. Further locality Tovačov-Annín is situated more down stream and has offered many trunks from dumps along exploitation space of the gravel pit. Only oak tree samples were used as a study material. Both dendrochronological and radiometric studies can be consider as preliminary. But, several results of 14C dating from both localities and their comparison with the others from literature sources, give more precise view of river behaviour during the Late Holocene time. Mass fluvial gravel deposition proceeds in the area of Tovačov (Morava River) minimally up to the Roman Time and more against the stream in Osek (Bečva River) up to the top of the Middle Ages

Organic matter of the fluvial valley bottom infi lling near Osek nad Bečvou and its relation to sedimentary development

Organic matter, like pollen, plant detritus or subfossil woods can be found in sequences of fluvial sediments. Detail study of these remains help to assess age of accumulation processes, especially during the Holocene erosion/accumulation cycle. Two localities with exposed infill of the Bečva River valley were found near Osek nad Bečvou. The first outcrop is a gravel pit 1 km south of Osek nad Bečvou village. The second one is a river-cliff on the left bank of the Bečva River, 1 km westward of Oldřichov village, formed mostly during the extreme flood in 1997. Fluvial sediments, 4–5 m thick, of the the so called “lower flood-plain level” were exposed on both localities. At the base of the Oldřichov river-cliff was encountered a horizon of boggy soil with subfossil trunk at the base. In the gravel pit near Osek nad Bečvou was exposed layer of clay/silt with plant detritus. Up to 2 m thick middle/coarse grained gravel, situated beneath underground water level, underlie the organic-rich sediments in both localities. Badenian clay represents the bedrock of the river valley. Organic-rich layers are overlaid by middle/coarse grained gravel sediments passing gradually to sandy silt of the flood plain. Pollen analyses were made from the organic-rich layers and dendrological analysis, dendrochronology and radiometric dating from subfossil trunk.Organic-rich layer from Osek (sample LS001) was assigned to the early Holocene based on pollen analysis and represents the oldest age found. The Oldřichov samples come from oxbow sediment. The sample LV030V was poor in pollen grains and inconclusive. The sample LV030Z indicates Holocene climate optimum (Atlantic). This supposed age is compatible with radiometric dating of the subfossil trunk from the base of the layer. Radiocarbon dating using wiggle matching method gave age of 7 070–6 775 BC.Based on these data, repeated erosion/accumulation events during Late Pleistocene and Holocene are evident in Bečva River valley fill. Late Pleistocene accumulation was replaced with erosion during Late Pleistocene-Holocene transition. Erosion on the break of the Pleistocene and Holocene partly removed upper Pleistocene gravels so in places left reached level 2 m above the bedrock. The first third of Holocene (time of all interpreted data) seems to be very stable from erosion/accumulation evolution point of view. More dynamic evolution started with accumulation of “higher flood-plain level” (from cca 214 m a. s. l. up to 221 m a. s. l.). Subsequent erosion formed relatively deep cut in the northwest part of the flood plain which was filled relatively quickly by sediments as consequence of deforestation connected with a colonization of upper parts of Bečva River drainage area. This is supported by finds of much younger subfossil trunks dated from 1 century BC up to top of Middle-Age period in this accumulation (Vít et al. 2009). The surface of this accumulation is the so called “lower flood plain level” where periodicity of the inundation during floods is more regular then on the upper one.Organic matter, like pollen, plant detritus or subfossil woods can be found in sequences of fluvial sediments. Detail study of these remains help to assess age of accumulation processes, especially during the Holocene erosion/accumulation cycle. Two localities with exposed infill of the Bečva River valley were found near Osek nad Bečvou. The first outcrop is a gravel pit 1 km south of Osek nad Bečvou village. The second one is a river-cliff on the left bank of the Bečva River, 1 km westward of Oldřichov village, formed mostly during the extreme flood in 1997. Fluvial sediments, 4–5 m thick, of the the so called “lower flood-plain level” were exposed on both localities. At the base of the Oldřichov river-cliff was encountered a horizon of boggy soil with subfossil trunk at the base. In the gravel pit near Osek nad Bečvou was exposed layer of clay/silt with plant detritus. Up to 2 m thick middle/coarse grained gravel, situated beneath underground water level, underlie the organic-rich sediments in both localities. Badenian clay represents the bedrock of the river valley. Organic-rich layers are overlaid by middle/coarse grained gravel sediments passing gradually to sandy silt of the flood plain. Pollen analyses were made from the organic-rich layers and dendrological analysis, dendrochronology and radiometric dating from subfossil trunk.Organic-rich layer from Osek (sample LS001) was assigned to the early Holocene based on pollen analysis and represents the oldest age found. The Oldřichov samples come from oxbow sediment. The sample LV030V was poor in pollen grains and inconclusive. The sample LV030Z indicates Holocene climate optimum (Atlantic). This supposed age is compatible with radiometric dating of the subfossil trunk from the base of the layer. Radiocarbon dating using wiggle matching method gave age of 7 070–6 775 BC.Based on these data, repeated erosion/accumulation events during Late Pleistocene and Holocene are evident in Bečva River valley fill. Late Pleistocene accumulation was replaced with erosion during Late Pleistocene-Holocene transition. Erosion on the break of the Pleistocene and Holocene partly removed upper Pleistocene gravels so in places left reached level 2 m above the bedrock. The first third of Holocene (time of all interpreted data) seems to be very stable from erosion/accumulation evolution point of view. More dynamic evolution started with accumulation of “higher flood-plain level” (from cca 214 m a. s. l. up to 221 m a. s. l.). Subsequent erosion formed relatively deep cut in the northwest part of the flood plain which was filled relatively quickly by sediments as consequence of deforestation connected with a colonization of upper parts of Bečva River drainage area. This is supported by finds of much younger subfossil trunks dated from 1 century BC up to top of Middle-Age period in this accumulation (Vít et al. 2009). The surface of this accumulation is the so called “lower flood plain level” where periodicity of the inundation during floods is more regular then on the upper one

The importance of Arctic driftwood for interdisciplinary global change research (Short Communication / Methodological note)

The Arctic is one of the regions most sensitive to global warming, for which climate and environmental proxy archives are largely insufficient. Arctic driftwood provides a unique resource for research into the circumpolar entanglements of terrestrial, coastal and marine factors and processes – past, present, future. Here, first dendrochronological and wood anatomical insights into 639 Arctic driftwood samples are presented. Samples were collected across northern Norway (n =430) and north-western Iceland (n =209) in 2022. The overall potentials and limitations of Arctic driftwood to improve tree-ring chronologies from the boreal forest, and to reconstruct changes in sea ice extent and ocean current dynamics are discussed. Finally, the role driftwood has possibly played for Arctic settlements in the past hundreds of years is examined

Exploring Growth Variability and Crown Vitality of Sessile Oak (Quercus Petraea) in the Czech Republic

Unraveling climatic effects on growth of oak - Europe’s most ecologically and economically important forest species - has been the subject of many recent studies; however, more insight based on field data is necessary to better understand the relationship between climate and tree growth and to adapt forest management strategies to future climate change. In this report, we explore the influence of temperature, precipitation and drought variability on the productivity and vitality of oak stands in the Czech Highlands. We collected 180 cores from mature oaks (Quercus petraea) at four forest stands in the Czech Drahany Highlands. Standard dendromethods were used for sample preparation, ring width measurements, cross-dating, chronology development, and the assessment of growth-climate response patterns. Crown vitality was also evaluated, using the modified ICP Forests methodology. Late spring precipitation totals between May and June as well as the mean July temperature for the year of ring formation were found to be the most important factors for oak growth, whereas crown condition was significantly affected by spring and summer drought. This study is rep-resentative for similar bio-ecological habitats across Central Europe and can serve as a dendroclima-tological blueprint for earlier periods for which detailed meteorological information is missing

Dendroclimatic study of a mixed spruce-fir-beech forest in the Czech Republic

European forests are undergoing an important transition due to the current climate change, as monocultures are being gradually replaced by mixed forests. Understanding tree growth in mixed forests under a changing climate is challenging because of tree species’ adaptation and long-term forest planning. In this study, we evaluate the long-term behaviour of Norway spruce (Picea abies), silver fir (Abies alba) and European beech (Fagus sylvatica) from a low montane range at the Czech-Austrian border. Species-specific tree-ring width chronologies have revealed significantly decreasing growth trends since the 2000s. Temporally unstable climate–growth relationships showed an increasing negative effect of current growing season drought on spruce growth and a positive effect of dormant season temperature on fir and beech growth. Our results suggest that though species’ response to climate change differs in the mixed forest, growth reduction in the last years has been proved for all species, likely due to frequent climate extremes

Carbon and nitrogen accumulation in common Alder forest (Alnus glutinosa Gaertn.) in plain of Drava river

Istraživanja su provedena u 95-godišnjoj visokoproduktivnoj sastojini crne johe (Alnus glutinosa Gaertn.) u Podravini. Cilj ovoga rada je istražiti glavna obilježja akumulacije i dinamike ugljika i dušika u sastojini crne johe, kao indikatora stabilnosti ekosustava i održivosti gospodarenja ovom sastojinom. Analiza dinamike i akumulacije ugljika i dušika tijekom godine obuhvatila je istraživanje tla, posebice šumske prostirke i A- horizonta, drva i kore crne johe te lista neposredno nakon odbacivanja. Masa šumske prostirke kreće se od 4,71 Mg ha–1 nakon odbacivanja lista, preko 3,36 Mg ha–1 u proljeće, do 0,51 Mg ha–1 u jesen prije ponovnog odbacivanja lista. Od jeseni do proljeća raste sadržaj ugljika i dušika u A- horizontu, a zatim ponovno opada. Akumulacija ugljika u nadzemnoj biomasi sastojine sredinom ljeta je 214,6 Mg ha–1, a u tlu je prosječno 143,5 Mg ha–1. S druge strane akumulacija dušika veća je u tlu – u nadzemnoj biomasi je 2 Mg ha–1, a u tlu dosiže čak i preko 14 Mg ha–1 (prosječno 13,8). Sveukupna akumulacija organskog ugljika u ekosustavu je 359,5 Mg ha–1, a dušika 15,8 Mg ha–1. Istraživanje je pokazalo da se radi o izuzetno vitalnoj sastojini, očito s izuzetno dobrim ekološkim uvjetima za rast crne johe. Njena se vitalnost i dugoročna stabilnost najbolje odražavaju u postojanom indeksu širine godova u posljednjih 80 godina, što potvrđuje i vrlo velika drvna zaliha, koja za sastojinu starosti 93–98 god. iznosi 751 m3 ha–1 (iznad taksacijske granice od 7 cm).This research was conducted in a 95-year-old, highly productive stand of black alder growing in the Drava plain in Croatia. The goal was to investigate the main features of carbon-nitrogen accumulation and dynamics in the stand of black alder (Alnus glutinosa (L.) Gaertn.), as an indicator of ecosystem stability and sustainability of managing such stands. Soil physiography was investigated in a permanent sample plot sized 1 ha with growing stock of 751 m3 ha–1. In the course of one season of leaf litter decomposition, the forest floor and soil from the A horizon were sampled on three occasions; the first sampling took place after leaf drop in 2009, the second at the beginning of vegetation (April 2010), and the third before leaf drop (beginning of November 2010). The forest floor mass was determined and so was the carbon and nitrogen content in the forest floor, in the bark, in the physiologically mature leaf and in the soil, as well as the soil pH value. Dendrochronological analysis was performed on black alder wood specimens to determine wood density and carbon and nitrogen content. Data from piezometers set up within the plot for the period 1997–2000 were used to interpret the water regime. According to the research, the soil is Haplic Gleysol (Endoarenic), with a relatively shallow A horizon, of sandy-clayey to loamy-sandy texture, of weakly acidic and in the deeper part weakly alkaline reaction. The water regime is characterized by a shallow and stable groundwater level which occasionally causes shallow (up to 20–30 cm) flooding in the out-of-vegetation period, and does not drop below 130 cm in the vegetation period. The forest floor mass ranges from 4.71 Mg ha–1 after leaf drop, over 3.36 Mg ha–1 in the spring, to 0.51 Mg ha–1 in the autumn before renewed leaf drop, which indicates complete decomposition of black alder leaf litter in a yearly cycle. During this period the C:N ratio decreases from 19 to 14.8. Carbon and nitrogen content in the A horizon increases from autumn to spring, but drops again afterwards. Simultaneously, the pH value significantly drops from autumn to spring, but rises again by autumn. In mid-summer, carbon accumulation in the above-ground biomass of the stand is 214.6 Mg ha–1, while in the soil it is 143.5 Mg ha–1 on average. On the other hand, nitrogen accumulation is higher in the soil: while it is 2 Mg ha–1 in the above-ground biomass, it reaches over 14 Mg ha–1 (13.8 on average) in the soil. Overall accumulation of organic carbon in the ecosystem is 359.5 Mg ha–1, and of nitrogen it is 15.8 Mg ha–1. The research has confirmed that this is an exceptionally vital stand, evidently with excellent ecological conditions for the growth of black alder. The vitality and long-term stability of this stand is best reflected in the stable ring width index in the past 80 years, as confirmed by the very large growing stock amounting to 751 m3 ha–1 for a stand aged 93–98 (above the taxation limit of 7 cm)

Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE

This study was funded by the WSL-internal COSMIC project (5233.00148.001.01), the ETHZ (Laboratory of Ion Beam Physics), the Swiss National Science Foundation (SNF Grant 200021L_157187/1), and as the Czech Republic Grant Agency project no. 17-22102s.Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the 14C content in 484 individual tree rings formed in the periods 770–780 and 990–1000 CE. Distinct 14C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved 14C measurements are needed.Publisher PDFPeer reviewe

Dendrochronology improves understanding of the charcoal production history, increasing the tourist potential in the Drahany Highlands

Over the last two years, three selected forest sites from Drahany Highlands were examined for traces of human activity. The most frequent traces found, and common to all three sites, were remains of charcoal production. This paper provides an anatomical and dendrochronological analysis of the charcoals found in two charcoal pile remains from each site. The species composition of the charcoals at the southern site was dominated by oak, followed by birch and hornbeam. Fir was more common than oak, beech, poplar, birch and hornbeam at the central site. Fir and beech were found at the northern site. By using dendrochronology, 23 fir, oak and beech charcoals were dated with the oldest sample coming from a central site and dated from the period 1753–1758. Charcoals from the three other charcoal piles fell into the first half of the 19th century. Radiocarbon dating of charcoals selected gave a very wide age range (1640–1955), except for one case (1399–1435). Providing information on the age of a charcoal pile can help raise public awareness and interest in viewing the sites where charcoal burners used to be active in the forests