In order to study radiocarbon levels at a clean air location in Slovakia with no significant local anthropogenic effects, we took tree ring samples from a tree in the vicinity of Jasná recreational area in the Low Tatras region in the central part of Slovakia. There are no significant local fossil fuel emission sources, so these samples represent a regional clean air background important for 14C studies in Slovakia and Central Europe. The growth rings from the sampled tree (European spruce, Picea abies) cover the period from 1911 to 2016. The first part of the data (1911-1952) represents natural radiocarbon levels influenced by Suess effect. The following period exhibits an increase in radiocarbon levels due to atmospheric nuclear weapons tests (Δ14C maximum of 850‰ in 1964), and then a gradual decrease characterized by an exponential trend with time constant of 14.3 ± 0.5 years. The Δ14C data from Jasná was used as a reference for comparison with two previously reported modern tree ring data sets from Slovakia. This comparison showed that radiocarbon levels at both locations are lower than clean air reference values, indicating the influence of local fossil fuel emissions.

• MeSH
• fosilní paliva MeSH
• monitorování radiace * MeSH
• smrk * MeSH
• stromy * MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Evropa MeSH
• Slovenská republika MeSH

The globally observed trend of changing intensity of tropical cyclones over the past few decades emphasizes the need for a better understanding of the effects of such disturbance events in natural and inhabited areas. On the Korean Peninsula, typhoon intensity has increased over the past 100 years as evidenced by instrumental data recorded from 1904 until present. We examined how the increase in three weather characteristics (maximum hourly and daily precipitation, and maximum wind speed) during the typhoon activity affected old-growth oak forests. Quercus mongolica is a dominant species in the Korean mountains and the growth releases from 220 individuals from three sites along a latitudinal gradient (33-38°N) of decreasing typhoon activity were studied. Growth releases indicate tree-stand disturbance and improved light conditions for surviving trees. The trends in release events corresponded to spatiotemporal gradients in maximum wind speed and precipitation. A high positive correlation was found between the maximum values of typhoon characteristics and the proportion of trees showing release. A higher proportion of disturbed trees was found in the middle and southern parts of the Korean peninsula where typhoons are most intense. This shows that the releases are associated with typhoons and also indicates the differential impact of typhoons on the forests. Finally, we present a record of the changing proportion of trees showing release based on tree-rings for the period 1770-1979. The reconstruction revealed no trend during the period 1770-1879, while the rate of forest disturbances increased rapidly from 1880 to 1979. Our results suggest that if typhoon intensity rises, as is projected by some climatic models, the number of forest disturbance events will increase thus altering the disturbance regime and ecosystem processes.

• MeSH
• cyklonové bouře * MeSH
• dub (rod) * MeSH
• stromy * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Korejská republika MeSH

BACKGROUND: Coppicing was one of the most important forest management systems in Europe documented in prehistory as well as in the Middle Ages. However, coppicing was gradually abandoned by the mid-20(th) century, which has altered the ecosystem structure, diversity and function of coppice woods. METHODOLOGY/PRINCIPAL FINDINGS: Our aim was to disentangle factors shaping the historical growth dynamics of oak standards (i.e. mature trees growing through several coppice cycles) in a former coppice-with-standards in Central Europe. Specifically, we tried to detect historical coppicing events from tree-rings of oak standards, to link coppicing events with the recruitment of mature oaks, and to determine the effects of neighbouring trees on the stem increment of oak standards. Large peaks in radial growth found for the periods 1895-1899 and 1935-1939 matched with historical records of coppice harvests. After coppicing, the number of newly recruited oak standards markedly grew in comparison with the preceding or following periods. The last significant recruitment of oak standards was after the 1930s following the last regular coppicing event. The diameter increment of oak standards from 1953 to 2003 was negatively correlated with competition indices, suggesting that neighbouring trees (mainly resprouting coppiced Tilia platyphyllos) partly suppressed the growth of oak standards. Our results showed that improved light conditions following historical coppicing events caused significant increase in pulses of radial growth and most probably maintained oak recruitment. CONCLUSIONS/SIGNIFICANCE: Our historical perspective carries important implications for oak management in Central Europe and elsewhere. Relatively intense cutting creating open canopy woodlands, either as in the coppicing system or in the form of selective cutting, is needed to achieve significant radial growth in mature oaks. It is also critical for the successful regeneration and long-term maintenance of oak populations.

• MeSH
• dub (rod) fyziologie   MeSH
• ekosystém * MeSH
• stromy chemie   růst a vývoj   MeSH
• zachování přírodních zdrojů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH

Biological age is typically estimated using biomarkers whose states have been observed to correlate with chronological age. A persistent limitation of such aging clocks is that it is difficult to establish how the biomarker states are related to the mechanisms of aging. Somatic mutations could potentially form the basis for a more fundamental aging clock since the mutations are both markers and drivers of aging and have a natural timescale. Cell lineage trees inferred from these mutations reflect the somatic evolutionary process, and thus, it has been conjectured, the aging status of the body. Such a timer has been impractical thus far, however, because detection of somatic variants in single cells presents a significant technological challenge. Here, we show that somatic mutations detected using single-cell RNA sequencing (scRNA-seq) from thousands of cells can be used to construct a cell lineage tree whose structure correlates with chronological age. De novo single-nucleotide variants (SNVs) are detected in human peripheral blood mononuclear cells using a modified protocol. A default model based on penalized multiple regression of chronological age on 31 metrics characterizing the phylogenetic tree gives a Pearson correlation of 0.81 and a median absolute error of ~4 years between predicted and chronological ages. Testing of the model on a public scRNA-seq dataset yields a Pearson correlation of 0.85. In addition, cell tree age predictions are found to be better predictors of certain clinical biomarkers than chronological age alone, for instance glucose, albumin levels, and leukocyte count. The geometry of the cell lineage tree records the structure of somatic evolution in the individual and represents a new modality of aging timer. In addition to providing a numerical estimate of "cell tree age," it unveils a temporal history of the aging process, revealing how clonal structure evolves over life span. Cell Tree Rings complements existing aging clocks and may help reduce the current uncertainty in the assessment of geroprotective trials.

• MeSH
• biologické markery MeSH
• dlouhověkost MeSH
• fylogeneze MeSH
• leukocyty mononukleární * MeSH
• lidé MeSH
• stárnutí * genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We propose the tree rings of European Larch ( Larix decidua) as a widely available and reliable geochemical archive of local and regional changes in atmospheric mercury (Hg). Mean Hg concentrations in larch tree rings from 8 background sites across the Czech Republic ranged from 2.2 to 4.8 μg kg-1; the maximum concentrations occurred in the period 1951-1970. At 3 sites impacted by Hg-emission sources [gold amalgamation processing, caustic soda production, and lead (Pb) ore smelting] mean larch tree ring Hg concentrations were significantly elevated relative to background sites. Changes in larch tree ring Hg concentrations were temporally coherent with known activities at the sites that would alter Hg emissions; the nearly simultaneous response in tree rings indicated little or no translocation of Hg within the larch bole. Based on the present-day atmospheric Hg concentration of 1.63 ng m-3 at the intensively monitored Czech Global Mercury Observation System site and the most recent mean tree ring Hg concentration of 2.8 μg kg-1 in co-located larch trees, we developed a simple distribution model of Hg between the atmosphere and larch tree rings. We applied the model using observed changes of Hg in larch tree rings from the countrywide background sites to reconstruct past atmospheric Hg concentrations in central Europe. Modeled Hg concentrations were in agreement with annual means from the European Monitoring and Evaluation Programme observatories.

• MeSH
• modřín * MeSH
• monitorování životního prostředí MeSH
• rtuť * MeSH
• zlato MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Česká republika MeSH
• Evropa MeSH

Genetic association studies in forest trees would greatly benefit from information on the response of trees to environmental stressors over time, which can be provided by dendroecological analysis. Here, we jointly analysed dendroecological and genetic data of surviving silver fir trees to explore the genetic basis of their response to the iconic stress episode of the 1970s and 1980s that led to large-scale forest dieback in Central Europe and has been attributed to air pollution. Specifically, we derived dendrophenotypic measures from 190 trees in the Bavarian Forest that characterize the resistance, resilience and recovery during this growth depression, and in the drought year in 1976. By focusing on relative growth changes of trees and by standardizing the dendrophenotypes within stands, we accounted for variation introduced by micro- and macroscale environmental differences. We associated the dendrophenotypes with single nucleotide polymorphisms (SNPs) in candidate genes using general linear models (GLMs) and the machine learning algorithm random forest with subsequent feature selection. Most trees at our study sites experienced a severe growth decline from 1974 until the mid-1980s with minimum values during the drought year. Fifteen genes were associated with the dendrophenotypes, including genes linked to photosynthesis and drought stress. With our study, we show that dendrophenotypes can be a powerful resource for genetic association studies that permit to account for micro- and macroenvironmental variation when data are derived from natural populations. We call for a wider collaboration of dendroecologists and forest geneticists to integrate individual tree-level dendrophenotypes in genetic association studies.

• MeSH
• ekologie MeSH
• fyziologická adaptace genetika   MeSH
• fyziologický stres genetika   MeSH
• genetické asociační studie MeSH
• genotyp MeSH
• jedle genetika   růst a vývoj   MeSH
• jednonukleotidový polymorfismus genetika   MeSH
• období sucha MeSH
• podnebí MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

In coppice-with-standards, once a common type of management in Central European lowland forests, selected trees (standards) were left to grow mature among the regularly harvested coppice stools to obtain construction wood. After the underwood was harvested, the forest canopy opened rapidly, giving standard trees an opportunity to benefit from reduced competition. Although this silvicultural system virtually disappeared after WWII, historical management cycles can still be traced in the tree-rings of remaining standards. Our research aims at answering the question whether tree-ring series of standard trees can be used to reconstruct past management practices. The study was carried out on 117 oak standard trees from five sites situated in formerly coppiced calcareous oak-hornbeam and acidophilous oak forests in the Bohemian Karst Protected Landscape Area, Czech Republic. The evaluation was based on the analysis of growth releases representing the response of the standards to coppicing events, and comparison to the archival records of coppice events. Our results showed that coppicing events can be successfully detected by tree-ring analysis, although there are some limitations. Altogether 241 releases were identified (49% of major releases). Large number of releases could be related to historical records, with the major ones giving better results. The overall probability of correct detection (positive predictive power) was 58%, ranging from 50 to 67%, probability for major releases was 78%, ranging from 63 to 100% for different sites. The ability of individual trees to mirror past coppice events was significantly affected by competition from neighboring trees (their number and the sum of distance-weighted basal areas). A dendro-ecological approach to the study of forest management history can serve as an input for current attempts of coppice reintroduction and for conservation purposes.

• MeSH
• dub (rod) chemie   růst a vývoj   MeSH
• ekosystém * MeSH
• lesy MeSH
• zachování přírodních zdrojů * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Ion-mediated changes in hydraulic conductivity (ΔKh) represent a mechanism allowing plants to regulate the rate of xylem transport. However, the significance of ΔKh for ring-porous (RPS) and diffuse-porous tree species (DPS) remains unknown. Here, we examined ΔKh in young branches of three coexisting, temperate RPS (Fraxinus excelsior, Quercus robur, Robinia pseudoacacia) and three DPS (Acer pseudoplatanus, Carpinus betulus, Fagus sylvatica) across the whole year, and assessed the relationships of ΔKh to branch anatomy. Ring-porous species exhibited twice as high ΔKh (10.3% vs 5.3%) within the growing season (i.e., during wood production) compared with DPS, and the production of the annual ring was identified as a crucial process affecting maximum ΔKh within the season. In addition, xylem in branches of RPS generally contained more axial parenchyma (AP; 18% vs 7%) and was characterized by a greater relative contact fraction between vessels and parenchyma (FVP; 59% vs 18%) than xylem in DPS. Simultaneously, ΔKh measured within the growing season was positively correlated with AP, FVP and bark proportions, suggesting that parenchyma in branches may be important for high ΔKh. Significant increase in ΔKh observed during the growing season may help RPS to restore conductive capacity after winter, better compensate transport loss by drought-induced embolism and thereby improve water delivery to leaves.

• MeSH
• poréznost MeSH
• roční období MeSH
• stromy * MeSH
• voda * MeSH
• xylém MeSH
• Publikační typ
• časopisecké články MeSH

Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-continental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1-100 years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks.

• MeSH
• brouci * MeSH
• fyziologický stres MeSH
• období sucha * MeSH
• stromy růst a vývoj   MeSH
• uhlík MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

BACKGROUND AND AIMS: The increasing frequency of disturbances in temperate forests is responsible for the greater numbers of trees with mechanically damaged cambial zones. Adjustment of wood anatomical structure to balance between safe and efficient water conductivity is one mechanism trees employ to cope with mechanical damage. The relative role of disturbances, tree age and climate in shaping xylem conduits and affecting xylem hydraulic conductivity remains unknown. METHODS: We performed an experiment with five different mechanical treatments simulating natural disturbances of juvenile Betula pendula trees (stem scarring, tilting, decapitation, root exposure and stem-base burial). After 3 years, trees were cut down, conduit size and density were measured, and specific hydraulic conductivity of each tree ring was calculated. Between-tree and between-year variability in xylem conductivity was decomposed into effects of tree age, climate and disturbances using linear mixed-effects models. KEY RESULTS: Xylem-specific hydraulic conductivity decreased significantly after treatment in decapitated, tilted and scarred trees. In the last treatment, wood anatomical adjustment was restricted to the area next to the callus tissue zone; in contrast, specific hydraulic conductivity declined over the entire stem circumference after tilting or decapitation. The response of trees with buried stems and exposed roots was generally weak. The overall effect of disturbances on inter-annual variability of wood anatomical structure was greater than the contribution of tree age and climate. CONCLUSIONS: The results indicate that disturbances are important drivers of xylem hydraulic conductivity. Expected increases in the frequency and intensity of disturbances may alter the theoretical capacity of forest stands for water conductance with a feedback to climate.

• MeSH
• bříza * MeSH
• dřevo MeSH
• podnebí MeSH
• stromy * MeSH
• voda MeSH
• xylém MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH