Tree Rings Research Articles

“I Was Born!”: Personal Experience Narratives and Tree-Ring Marker Years

This essay, co-written by a dendrochronologist (Nick) and a narrative theorist (Erin), considers how these two disciplines can meet to illuminate alternative narratives in tree rings. At the basis of our conversation is a desire to tease apart tree experience and the signification entangled within human practices of storytelling. First, Nick explains recent developments in dendrochronology and critical physical geography (CPG) that call attention to the ways in which tree-ring sciences often naturalize imperial narratives and demand alternative methodologies. Second, Erin dives into the imperial narratives of two case study tree bodies, throwing light upon the human and vegetal stories that these dominant narratives obscure and silence. Third, Nick turns to an experiment in critical participatory action research (CPAR) to suggest an approach to tree-ring dating—material dating—that takes its cues not from imperial histories but from a simultaneous interest in community engagement, anticolonial scholarship, and tree agency and signification. Fourth, Erin explains how material dating, via foregrounding personal experience, stands to produce a narrative more sensitive to a particular tree’s situated experience and better able to foment understanding among tree body viewers for the tree as a living and communicating organism. Finally, Nick and Erin use material dating to produce an alternative narrative for one of our case studies and provide directions for other scholars to replicate our process.

Isolation and Identification of Pear Ring Rot Fungus and Resistance Evaluation of Different Pear Varieties

Botryosphaeria dothidea is a significant plant pathogen responsible for causing ulcers, wilt, and fruit decay across a wide range of host plants. One notable fungal disease attributed to B. dothidea is pear tree ring rot, which currently ranks among the most severe diseases affecting pear trees in China. This pathogen primarily targets branches and fruits, occasionally impacting leaves as well, leading to tree weakening, fruit rot, and leaf drop. The annual repercussions of this disease severely affect both the yield and quality of pear fruits, thereby impeding the healthy development of the pear industry. Recent studies have indicated that other species within the B. dothidea complex can also induce pear ring rot; however, specific physiological strains of B. dothidea remain unreported. Consequently, this study collected tissues from pear trees infected with ring rot from orchards located in Liaoning, Hebei, Shandong, and other regions throughout China. Through morphological characterization combined with pathogenicity assessments and DNA sequence comparisons involving partial internal transcribed spacer (ITS), translation elongation factor (TEF), and β-tubulin (TUB) genes, 21 strains belonging to the Botryosphaeria spp. were identified. These 21 strains served as research subjects for inoculating dormant annual branches from 30 germplasm resources of pear trees in vitro. The results demonstrated that all tested strains could induce lesions on the branches which were characterized by dark brown spots. Furthermore, inoculation experiments involving these 21 strains were conducted to evaluate the resistance levels of various pear varieties against ring rot disease. The resistance was assessed by inoculating different isolates onto distinct pear varieties; this approach established the criteria for evaluating resistance while minimizing identification errors stemming from the variable responses exhibited by certain varieties towards individual strains. Ultimately, this study aims to provide a theoretical foundation for effective prevention and treatment strategies against pear ring rot.

Evaluating tree-ring proxies for representing the ecosystem productivity in India.

Terrestrial ecosystems are one of the major sinks of atmospheric CO2 and play a key role in climate change mitigation. Forest ecosystems offset nearly 25% of the global annual CO2 emissions, and a large part of this is stored in the aboveground woody biomass. Several studies have focused on understanding the carbon sequestration processes in forest ecosystems and their response to climate change using the eddy covariance (EC) technique and remotely sensed vegetation indices. However, very few of them address the linkage of tree-ring growth with the ecosystem-atmosphere carbon exchange, and nearly none have tested this linkage over a long-term (> 100 years) - limited by the short-term (< 50 years) availability of measured ecosystem carbon flux. Nevertheless, tree-ring indices can potentially act as proxies for ecosystem productivity. We utilise the Coupled Climate Carbon Cycle Model Intercomparison Project (C4MIP) model outputs for its 140-year-long simulated records of mean monthly gross primary productivity (GPP) and compare them with the tree-ring growth indices over the northwestern Himalayan region in India. In this study, we examine three coniferous tree species: Pinus roxburghii and Picea smithiana wall. Boiss and Cedrus deodara and find that the strength of the correlation between GPP and tree ring growth indices (RWI) varies among the species.

Utilizing Paleoclimate Data to Analyze the Relationship Between Climate Change and Human Activities

Our research aims at finding the relationship between climatic cycle-changes and the human activities in ancient China. Most climatic changes show shifts in the precipitation volume and alternations between warm and cold periods. Through other research findings, we find the precipitation volume is closely connected with alternations of warm and cold periods. This report presents a linear comparison between the population of ancient China and the east Asia climate variables and chooses tree rings as the main indicator of the paleo-climate. Through the literature review and the data analysis, we find that (1) The dominant climate pattern in East Asia is East Asia Summer Monsoon system, causing centennial scaled climate periodicities, affecting the ecosystem and the society. (2) There are certain cycles of climate change, in which the warm period and the cold period have a certain influence on the population change. (3) The precipitation has a certain correlation with the population change. However, single temperature and precipitation cannot directly affect the population change, but also need to be combined with social and historical factors specific analysis.

Spatiotemporal Distribution of Mercury in Tree Rings and Soils Within Forests Surrounding Coal-Fired Power Plants

The release of mercury (Hg) from coal-fired power plants (CPPs) into local ecosystems poses substantial environmental and health hazards. This study was conducted in Chungcheong-nam-do, South Korea, a region featuring over half of the country’s coal power facilities, to estimate the impacts of CPPs on Hg distribution in forest ecosystems. By analyzing Hg concentrations in pine tree rings and soil at 21 locations around CPPs and comparing them to control sites and industrial zones, we present a nuanced understanding of the effects of CPPs on Hg concentration. The analysis of Hg concentrations in tree rings showed a significant decrease in Hg levels as the distance from the power plants increased, suggesting that CPPs primarily influence Hg distribution in trees within a 25 km radius. In contrast, soil Hg concentrations did not exhibit a clear trend. This may reflect the limitations of this study in accounting for the physicochemical properties of the soil at each sampling site. Nevertheless, the Potential Ecological Risk Index for soil Hg contamination indicated a higher risk rating within a 1 km radius of the CPPs compared to other locations. Hg concentrations in tree rings have shown a steady decline since the 1970s, suggesting the positive effects of air pollution regulations. This also highlights the value of tree core samples as effective tools for monitoring historical Hg pollution. Furthermore, the higher historical concentrations of Hg in tree rings imply that trees may have acted as sinks for atmospheric Hg in the past.

Mapping the Normalized Difference Vegetation Index for the Contiguous U.S. Since 1850 Using 391 Tree-Ring Plots

The forests and grasslands in the U.S. are vulnerable to global warming and extreme weather events. Current satellites do not provide historical vegetation density images over the long term (more than 50 years), which has restricted the documentation of key ecological processes and their resultant responses over decades due to the absence of large-scale and long-term monitoring studies. We performed point-by-point regression and collected data from 391 tree-ring plots to reconstruct the annual normalized difference vegetation index (NDVI) time-series maps for the contiguous U.S. from 1850 to 2010. Among three machine learning approaches for regressions—Support Vector Machine (SVM), General Regression Neural Network (GRNN), and Random Forest (RF)—we chose GRNN regression to simulate the annual NDVI with lowest Root Mean Square Error (RMSE) and highest adjusted R2. From the Little Ice Age to the present, the NDVI increased by 6.73% across the contiguous U.S., except during some extreme events such as the Dust Bowl drought, during which the averaged NDVI decreased, particularly in New Mexico. The NDVI trend was positive in the Northern Forest, Tropical Humid Forest, Northern West Forest Mountains, Marin West Coast Forests, and Mediterranean California, while other ecoregions showed a negative trend. At the state level, Washington and Louisiana had significantly positive correlations with temperature (p &lt; 0.05). Washington had a significantly negative correlation with precipitation (p &lt; 0.05), whereas Oklahoma had a significantly positive correlation (p &lt; 0.05) with precipitation. This study provides insights into the spatial distribution of paleo-vegetation and its climate drivers. This study is the first to attempt a national-scale reconstruction of the NDVI over such a long period (151 years) using tree rings and machine learning.

Model Test on Acoustic Emission Monitoring of Loess Slope Failure

The three stages of loess collapse are characterized by notable concealment and sudden onset due to the sudden nature of loess collapse and the prolonged duration of the peristaltic deformation stage. Traditional displacement monitoring methods struggle to detect early signals of instability and failure, leading to poor timeliness in disaster warnings. This project begins by examining non-force field information related to the loess collapse process. It focuses on acoustic emission monitoring and employs model tests to identify effective waveguide rods for monitoring loess collapse. Additionally, the project investigates the evolution anomalies of acoustic emission parameters before and after loess collapse failure, aiming to establish early warning criteria for loess collapse based on acoustic emission. This work provides a theoretical basis for monitoring and early warning of loess collapses. This study evaluates five parameters of the active waveguide system: sensor installation method, filling material, waveguide rod wall thickness, outer wrapping material, and outer wrapping wall thickness. The densities of the filler materials were tested using the optimal parameters derived from the tests to identify the best configurations for active acoustic emission (AE) waveguide systems suitable for monitoring loess collapse. Subsequently, a one-sided connected loess collapse model was employed for indoor tests, integrating real-time AE monitoring with the active waveguide method. This model facilitates the exploration of AE response characteristics during loess collapse and the analysis of destructive forms of loess collapse and time-sequence evolution of AE ringing counts throughout the deformation and destruction process. Results indicate that using filler materials with high elasticity modulus, high compactness, and low Poisson’s ratio, along with thin outer wrapping and waveguide rod walls, leads to strong AE signals. As deformation damage of loess collapse intensifies, the number of AE ringing counts notably increases. A rapid rise in cumulative ringing counts can indicate a “sudden increase”, or the b-value may stabilize, providing precursor information for loess collapse.

Ductility and cracking behavior of UHPC-RC composite beam under bending test based on acoustic emission parameters

Ultrahigh-performance concrete (UHPC) possesses improved mechanical properties due to its high strength, durability, and toughness. Currently, there is a single method for detecting the cracking behavior and evaluating the ductility of the UHPC-reinforced concrete (RC) composite beam. As an important part of structural non-destructive monitoring techniques, the acoustic emission (AE) technique can be used to analyze the damage pattern of the structure by the variation characteristics of its individual parameters. On this basis, four-point bending tests were carried out on the RC beam and UHPC-RC composite beam, and the AE technique was used for ductility analysis and cracking behavior monitoring. The results showed that the UHPC material enhanced the flexural capacity of the UHPC-RC composite beam. The AE ring counts and energy parameters could be used to analyze the cracking process of the UHPC-RC composite beam during flexural damage. The proposed new ductility indices, AE ring counts ductility index (ARD) and AE energy ductility index (AED), differed from the displacement ductility indices within the range of 2 %, providing a new method for calculating ductility indices of concrete structures. During the failure stage, the UHPC-RC composite beam produced more tensile cracks at the early stage of cracking and the stage of damage compared to the RC beam. In addition, the b value of the RC beam had a large range of fluctuations during the failure stage, indicating that the RC beam produced more micro-cracks and macro-cracks and more damage compared to the UHPC-RC composite beam.

Monitoring weekly δ 13С variations along the cambium-xylem continuum in the Canadian eastern boreal forest.

Intra-annual variations of carbon stable isotope ratios (δ13C) in different tree compartments could represent valuable indicators of plant carbon source-sink dynamics, at weekly time scale. Despite this significance, the absence of a methodological framework for tracking δ13C values in tree rings persists due to the complexity of tree ring development. To fulfill this knowledge gap, we developed a method to monitor weekly variability of δ13C in the cambium-xylem continuum of black spruce species [Picea mariana (Mill.) BSP.] during the growing season. We collected and isolated the weekly incremental growth of the cambial region and the developing tree ring from five mature spruce trees over three consecutive growing seasons (2019-2021) in Simoncouche and two growing seasons (2020-2021) in Bernatchez, both located in the boreal forest of Quebec, Canada. Our method allowed for the creation of intra-annual δ13C series for both the growing cambium (δ13Ccam) and developing xylem cellulose (δ13Cxc) in these two sites. Strong positive correlations were observed between δ13Ccam and δ13Cxc series in almost all study years. These findings suggest that a constant supply of fresh assimilates to the cambium-xylem continuum may be the dominant process feeding secondary growth in the two study sites. On the other hand, rates of carbon isotopic fractionation appeared to be poorly affected by climate variability, at an inter- weekly time scale. Hence, increasing δ13Ccam and δ13Cxc trends highlighted here possibly indicate shifts in carbon allocation strategies, likely fostering frost resistance and reducing water uptake in the late growth season. Additionally, these trends may be related to the black spruce trees' responses to the seasonal decrease in photosynthetically active radiation. Our findings provide new insights into the seasonal carbon dynamics and growth constraints of black spruce in boreal forest ecosystems, offering a novel methodological approach for studying carbon allocation at fine temporal scales.

Inter- and Intra-Annual Variations in Oak Tree Ring δ13C Values across Different Elevations and Their Climatic Responses in Qinling Mountains

The Qinling Mountains, serving as a natural geographical and climatic boundary in China, require comprehensive climatic records to elucidate the trends in climate changes across the country. While stable isotopes in tree rings are widely employed to indicate historical environmental changes, investigations into tree ring isotopes in the Qinling Mountains, particularly within the widespread broad-leaf oaks, remain limited. In this study, we investigated both intra- and inter-annual variations in the δ13C values of tree rings and their correlations with climatic signals over the past two decades for Quercus aliena var. acuteserrata, a dominant species among oak trees on the main peak of the Qinling Mountains. Our results reveal that responses to climate differ among altitudes and individual trees, with trees at higher altitudes exhibiting higher sensitivity to extreme climate, which is low temperatures and rainfall fluctuations during the growth period in intra-annual δ13C variations. Furthermore, the positive correlations are observed between temperature during growing season and both tree growth and the inter-annual δ13C variations. However, the climate signal appears to be hampered by oak-specific factors, such as intense competition among individuals and the age of trees. Therefore, we suggest a more rigorous selection of sampling and propose further investigations into isotopic fractionation processes in oaks for future studies.

Climatic Effects on the Growth of Fagus sylvatica L. in Mixed Stands with Pinus sylvestris L. in Lithuania

Climate change and warming will potentially profoundly affect forest growth and yield. However, climate change is not only a threat but also an opportunity for tree species to be more productive or colonize new territories where previously they were fragmented or absent. European beech (Fagus sylvatica L.) is a dominant and significant tree species in European forests with a pronounced ability to grow on a great variety of sites and to form mixtures with other tree species due to its shade tolerance. So far, only a few studies have analysed its growth and reaction to changing climatic conditions outside its natural gradient in the north. The aim of this study was therefore to clarify the main growth patterns and tree ring formation characteristics of beech (outside their natural distribution) in mixed stands with Scots pine (Pinus sylvestris L.) The analyses were carried out in two-layered stands in the western part of Lithuania with tree-ring data measured on stem disks collected at 1 m height that were available from shelter-cut thinning activities in a number of forest stands in the region. Our results show that higher temperatures during the summer months of July and August generally inhibited the radial growth of beech under given site conditions. In contrast, warmer late-autumn and cooler early-winter periods together with warmer springs positively affected the radial increments. Above-average precipitation during the vegetation period contributed to the beech producing additional amounts of radial increments. The increasing temperature trends of the summer months and decreasing monthly amounts of precipitation during the vegetation period in recent decades tend to have adverse effects on the ecological conditions for beech growth and vitality in Lithuania. Despite these results, the European beech successfully grows in the sample region and has produced 200 m3 ha−1 in the analysed stands.

Inter- and intra-annual carbon isotope fluctuations in Pinus sylvestris L. tree rings whole wood and cellulose in north-eastern Lithuania

In temperate regions trees typically exhibit growth sensitivity to climatic conditions during the growth season. Annual tree ring growth increments correlate with a variety of environmental factors. As an index of water use efficiency, δ13C is a preferred proxy to allow accurate interpretation of environmental factors critical for the tree growth, including changes in climate patterns, variation in the ambient temperature and precipitation. We assumed that isotopic differences within individual tree rings are likely to produce seasonal isotope fluctuations in the chronology that might be interpreted as response to environmental impacts. To verify the assumption, we measured δ13C in annual tree rings of Pinus Sylvestris L. split into 13 intra-annual segments each and checked δ13C correlations with temperature, precipitation, the number of sunshine hours and relative air humidity. For the investigation, we chose a site in north-eastern Lithuania, Zarasai, located in boreal latitude and remote from industrial pollution sources. The methodology of the research was based on high coherence of δ13C chronologies measured in the whole wood and α-cellulose extracted by means of two different methods. The experiment produced strong δ13C correlations with hydrometeorological parameters, especially in the earlywood formed in June

Evolution and Characterization of Uniaxial Compression Damage of Coal Measure Rock

In order to study the evolution law of uniaxial compression damage and its characterization method, three kinds of rocks with different lithology that commonly exist in coal measure rock were taken as the research objects to explore the relationship between their mineral composition, microstructure and mechanical properties, and the feasibility of acoustic emission (AE) characteristic parameters and AE spatial location to characterize the evolution process of uniaxial compression damage of rocks was compared and analyzed. A damage constitutive model based on AE cumulative ringing count was established and verified by numerical simulation. The results show that the differences in the micromorphology and mineral composition of coal measures with different lithology directly affect their physical and mechanical properties and load damage characteristics. AE characteristic ringing count can effectively represent the damage evolution process of rock during loading. Based on rock porosity characteristics and AE cumulative ringing count during loading, a constitutive model considering initial damage and cumulative damage was established. The theoretical analysis results of the damage constitutive model are in good agreement with the results of laboratory experiments and numerical simulation, which can be used to analyze the damage process of coal measure rock under load.

Bending properties and damage evolution of fiber-reinforced aeolian sand backfill materials

Backfilling is a promising measure for controlling surface subsidence in mined-out areas and disposing solid wastes from the mineral processing, there are increasing demands of enhanced toughness and anti-cracking properties of backfill materials to prolong the service life under the complex loads. In this study, polypropylene (PP) fibers were employed to improve performance of backfills, four-point bending and uniaxial compression tests were conducted to investigate the failure process and damage evolution of fiber-reinforced aeolian-sand backfill materials (FABs) using Digital Image Correlation (DIC) and Acoustic Emission (AE) techniques. The results show that the compressive strength tends to decrease with the increasing fiber volume fractions, while the four-point bending strength shows a tendency to increase initially and then decrease, and the optimum volume fraction of PP fiber is 0.6%. At the optimal fiber volume fraction, PP fibers with lengths of 3 mm and 9 mm resulted in a 65.25% and 81.62% increase in the four-point bending strength of FABs, respectively. As indicated by DIC measurements, PP fibers with a length of 9 mm were more effective in controlling the horizontal and vertical displacements of FABs under four-point bending loads than that of 3 mm, and the cracks developed more slowly at the same deflection. In addition, PP fibers with a length of 9 mm have stronger crack extension delay characteristics due to longer effective anchorage distance, as evidenced by more frequent acoustic emission ringing counts and higher cumulative ringing counts. The results of the study may provide a theoretical basis for the application of FABs materials in backfilling.

Dendroclimatological study of ancient trees integrating non-destructive techniques.

Based on the need to protect previous ancient trees and the development of dendroclimatology, the use of non-destructive technologies in tree-ring research has gained increasing attention. This study focuses on the ancient Pinus tabulaeformis in Yu Xiang Forest Farm in Henan Province. Firstly, samples were collected using the traditional Increment borers and the Resistograph, a non-destructive method. Subsequently, the peak-valley analysis was used to filter the data obtained by the Resistograph to extract the tree ring width sequence, and the data's accuracy was verified by correlation analysis with tree ring width sequence by the Increment borers. Then, the optimal filtering method and an appropriate comprehensive threshold were determined, and tree ring width and density sequences were successfully extracted. Following that, the growth trend and residual resistance in the measurement process were corrected using linear fitting and Ensemble Empirical Mode Decomposition (EEMD) technology, thereby establishing the tree-ring width and density index series, which were further validated through correlation analysis and t-tests. Finally, analysis of the correlation with climatic factors, identified the main limiting factors for tree growth, and the accuracy of the tree-ring information extracted by the Resistograph was further verified. The results showed that spite of certain differences between the tree-ring width indices extracted by the Resistograph and the Increment borer, they were generally reliable. The radial growth of the ancient P.tabulaeformis in Yu Xiang Forest Farm is primarily influenced by temperature, with the maximum density of the tree rings responding more significantly to the mean maximum temperature, while the minimum density of the tree rings responded more significantly to the mean minimum temperature. These results not only provide a scientific and accurate age for the protection of ancient trees and verify the reliability of the data obtained by the Resistograph, but also facilitate the use of non-destructive technology for in-depth study of ancient trees, therefore enhancing our understanding of how climate change affects tree growth and provide valuable insights for the future protection and management of these ancient trees.

Precipitation reconstructions in the northern and southern Qilian Mountains based on tree rings of Picea crassifolia

Precipitation reconstructions in the northern and southern Qilian Mountains based on tree rings of Picea crassifolia

Damage evolution and acoustic emission characteristics of sandstone under different true triaxial cyclic loading and unloading modes

In the process of deep coal mining, the cyclic mining disturbance behavior produces significant cyclic loading and unloading effects, to ensure safe production in the mining area, it is necessary to study the damage characteristics and acoustic emission characteristics of the rock body under different cyclic loading and unloading effects. This study developed a TAWZ-5000/3000 rock true triaxial (disturbance) test system and used it to carry out true triaxial cyclic loading and unloading tests in different modes, with acoustic emission (AE) monitoring of the deformation and damage processes. The test results proved that a large number of cycles weakens the rock’s ability to control deformation, and this weakening ability is also related to the types of cyclic loading and unloading modes. The hysteresis loop characteristics and mechanical parameters show obvious path dependence. Based on the damage equivalence method, it is found that the absolute damage parameter increases with the increase of the number of cycles in the same mode, and the accumulation rate of the cumulative damage parameter is faster; the cumulative damage parameter in the equal amplitude cyclic loading and unloading (EAC) mode is always higher than that in the other two modes. The normalized AE ring count rate in the rock samples under cyclic loading and unloading has a significant relationship with the damage percentage, and the crack extension scale function (b-value) shows the “steady increase – strong fluctuation − significant decline” trend. By analyzing the AE characteristic parameters, namely rise time/amplitude (RA) and ringing count/duration (AF), it is found that the sandstones in EAC, graded cyclic loading and unloading (GC), and stepped cyclic loading and unloading (SC) modes are mainly damaged by tension-shear and shear, respectively. By analyzing the values of the acoustic emission parameters RA-AF, it is found that the sandstone is mainly damaged by tensile shear, tensile tension, and shear under EAC, GC, and SC modes, respectively, corresponding to the rock samples’ damage patterns. The study results have important guiding significance for preventing and controlling disasters in deep mines.

Tree-ring anomalies as time markers for ice-core chronologies, with special reference to 5281 BCE as the possible date of the Kikai volcanic event

The synchronization of Greenland and Antarctica ice core data with tree-ring data, other proxies, and direct observations of natural processes and events is important to understand past climatic variation and environmental change. One of the methods that is used to correct the dating of ice layers is to match volcanic eruption footprints in ice cores with tree rings, manifested as sulphate spikes and anomalous rings, respectively. In this study, we inventoried the occurrence of tree-ring anatomical anomalies and extremes in ring width during three 200-year periods. These periods included three of the eight largest Holocene volcanic eruptions, each with a Volcanic Explosivity Index (VEI) of 7. The initial period spanned from 6560 to 6360 BCE and included the eruption of Ilyinsky Volcano in Kamchatka. The second period was from 5780 to 5580 BCE, during which Mount Mazama Volcano in North America erupted. The third period was from 5380 to 5180 BCE when the Kikai Volcano in the Japanese Islands erupted. Throughout the first two periods, no substantial tree-ring anomalies were observed suggesting the absence of any significant climate consequences of a major volcanic eruption. However, in the 5380–5180 BCE period, a clear sharp decline in tree growth and an exceptionally high frequency of tree-ring anomalies were identified in 5281 BCE and the subsequent 5 years. We propose that the exceptionally narrow light rings in these 6 years are indicative of the climatic impact resulting from the Kikai volcanic eruption. We suggest utilising the year 5281 BCE as the reference year for synchronising the Greenland and Antarctica ice core chronologies. In the case that our assumption is correct, this would imply the necessity to adjust the time of the event to an earlier date compared to the dates indicated by the existing ice core chronologies of the GICC05 (Greenland Ice Core Chronology 2005), adjusted according to Kobashi (2017), and WD2014 used for creating HolVol 1.0 (Holocene ice-core volcanic eruption catalogue from 9500 BCE - 1900 CE) by 67 and 54 years, respectively, for the period around 5300 BCE. A verification of our assumption could be conducted by examining the nearby Miyake event, a spike in cosmogenic radiocarbon, of 5258 BCE. Ice core layers displaying potential signs of this event should be approximately 25 years later than the markers of the Kikai volcanic eruption.

Tree rings reveal the correlation between the Kaindy Lake submerged forest and the historical 1889 M 8.2 Chilik earthquake (Kazakhstan)

Tree rings reveal the correlation between the Kaindy Lake submerged forest and the historical 1889 M 8.2 Chilik earthquake (Kazakhstan)

Reconciling water-use efficiency estimates from carbon isotope discrimination of leaf biomass and tree rings: nonphotosynthetic fractionation matters.

Carbon isotope discrimination (∆) in leaf biomass (∆BL) and tree rings (∆TR) provides important proxies for plant responses to climate change, specifically in terms of intrinsic water-use efficiency (iWUE). However, the nonphotosynthetic 12C/13C fractionation in plant tissues has rarely been quantified and its influence on iWUE estimation remains uncertain. We derived a comprehensive, ∆ based iWUE model (iWUEcom) which includes nonphotosynthetic fractionations (d) and characterized tissue-specific d-values based on global compilations of data of ∆BL, ∆TR and real-time ∆ in leaf photosynthesis (∆online). iWUEcom was further validated with independent datasets. ∆BL was larger than ∆online by 2.53‰, while ∆BL and ∆TR showed a mean offset of 2.76‰, indicating that ∆TR is quantitatively very similar to ∆online. Applying the tissue-specific d-values (dBL = 2.5‰, dTR = 0‰), iWUE estimated from ∆BL aligned well with those estimated from ∆TR or gas exchange. ∆BL and ∆TR showed a consistent iWUE trend with an average CO2 sensitivity of 0.15 ppm ppm-1 during 1975-2015. Accounting for nonphotosynthetic fractionations improves the estimation of iWUE based on isotope records in leaf biomass and tree rings, which is ultimate for inferring changes in carbon and water cycles under historical and future climate.