High Mountain Asia (HMA) has experienced rapid warming and increased climate extremes, yet limited instrumental records constrain understanding of whether recent changes exceed long-term natural variability. Paleoclimate data assimilation offers opportunities to integrate sparse proxy observations with climate model priors, generating spatiotemporally complete reconstructions. We reconstructed gridded temperature and precipitation fields (1501–2000 CE) and identified extreme climate events across HMA by applying three Ensemble Kalman Filter methods to a baseline Pages2k dataset (201 records) and an expanded Combined dataset (297 records). Cross-validation demonstrates skillful temperature reconstruction and modest precipitation skill. The three methods show high consistency, while expanding the baseline dataset with additional proxies enhances extreme event detection by 39

Persistent hydroclimatic extremes strongly affect water resources and ecosystems in Northeast Asia, but instrumental climate and runoff records are too short to characterize multidecadal wet–dry variability. We developed two tree-ring-based seasonal precipitation reconstructions for western and eastern Northeast China and compared them with a moisture-sensitive precipitation record from the Russian Far East. The western reconstruction spans 1829–2022 and targets previous September–current June precipitation, whereas the eastern reconstruction spans 1680–2022 and targets January–July precipitation. Both reconstructions show significant precipitation signals and acceptable verification skill. Comparisons with natural runoff and discharge records indicate that reconstructed precipitation variability is expressed in regional runoff, particularly at low-frequency to decadal timescales.The reconstructions reveal both coherent and regionally divergent hydroclimatic regimes. A common wet interval occurred during 1855–1867, whereas a pronounced common dry interval occurred during 1911–1928, including the well-known 1920s drought. Cross-regional comparison shows that drought extremes were more spatially coherent than pluvial extremes, and duration–severity analysis identifies persistent regimes with large cumulative anomalies. Composite diagnostics associate coherent wet extremes with El Niño-like tropical Pacific warming, positive 500-hPa geopotential height anomalies, and enhanced 850-hPa moisture flux convergence. Coherent droughts were associated with La Niña-like cooling and weaker or displaced moisture convergence. These results show that tree-ring precipitation reconstructions can provide a long-term perspective on runoff-relevant hydroclimatic persistence and moisture-transport variability across Northeast Asia.

Reliable water supply from glacierized mountain catchments is increasingly threatened by climate change, yet instrumental records are too short to assess whether recent hydrological shifts exceed natural variability. Here, we present a 445-year tree-ring-based reconstruction of August-July runoff for the Urumqi River in the eastern Tien Shan, a key water tower for arid Central Asia. The reconstruction shows that runoff since the 1960s, although elevated, has remained within the range of natural variability since 1575 CE, with no significant shift beyond the pre-industrial variability envelope. Attribution analysis identifies glacial buffering as the key stabilizing mechanism: the explanatory contribution of glacier mass balance to runoff variability tripled from similar to 4% (1960-1989) to similar to 12% (1990-2019), with increased meltwater compensating for precipitation deficits during dry spells. Cross-basin comparisons indicate that hydrological stationarity is regulated by the glacial contribution ratio. While precipitation-dominated basins with low glacier cover maintain stable regimes, heavily glacierized basins are undergoing non-stationary shifts due to sustained ice loss. CMIP6 projections suggest this buffering is transient; runoff is projected to peak around mid-century and then decline, transitioning toward a more volatile, precipitation-dominated regime. Our findings highlight that glaciers currently maintain hydrological stability in warming arid basins, but their continued loss commits these critical water resources to a more uncertain and unstable future-an insight with broad implications for water security in glacier-fed river basins worldwide.

Although increment borers are the standard for non-destructive tree-ring coring, cores frequently get stuck, compressed, fragmented, and damaged. Here, we present the new ”Increment Core Ejector”, a simple though efficient too to expel intact or fractured cores from the hollow tube in a controlled axial manner. The device integrates a threaded rod, a limiter assembly, a connection assembly, a fixing assembly, a hollow sampling tube, and an anti-drop assembly. Rotation of the threaded rod produces progressive axial advancement, allowing the operator to eject jammed samples without resorting to abrupt forcing, heating, or uncontrolled manual pulling. In addition to describing the device architecture and operating sequence, this report contextualises the ejector within the broader methodological literature on increment borer handling, bark-related jamming, micro-borer extraction, and commercial core-ejection aids. The Increment Core Ejector is intended as a compact post-sampling recovery tool that improves sample integrity, reduces field downtime, and extends the operational life of dendrochronological increment borers.

The East Asian Monsoon Transition Zone is highly sensitive to hydroclimatic variability, making it essential to systematically investigate its hydrological dynamics from both historical and future perspectives. However, the scarcity of long-term hydrological observations hampers robust assessments of whether recent extreme events exceed the bounds of natural variability. Here, we reconstructed a 260-year streamflow record for a representative watershed in this transition zone using tree-ring chronologies. The reconstruction reveals that, relative to the East Asian Summer Monsoon, the regulatory influence of the upper-jet stream on regional streamflow variability has become increasingly prominent. To investigate the recent rise in extreme hydrological events, we integrate machine learning models with Shapley additive planation (SHAP)-based interpretability analysis. Results indicate that precipitation is the dominant control on runoff variability, while leaf area index and potential evapotranspiration emerge as particularly sensitive indicators of hydrological change. Furthermore, a comprehensive assessment combining the Budyko framework with CMIP6 multi-model ensemble projections suggests that future increases in runoff will be primarily governed by land surface processes, which account for approximately 59.5% of the total projected change. Overall, this study provides a long-term perspective and forward-looking assessment of hydrological evolution in the East Asian monsoon transition zone, offering critical insights into the mechanisms regulating regional water resources under ongoing climate change.

Although it is generally accepted today that climate and other environmental factors affected past human societies at different spatiotemporal scales, direct linkages are difficult to determine, and correlation should not be confused with causation. Here, we use a tree-ring width network of multimillennial chronologies from inner Eurasia to reconstruct annual changes in Net Primary Productivity (NPP) back to 200 BCE. Our findings reveal that episodes of reduced NPP around the 70s-100s, 360s-380s, and 470s-560s CE likely contributed to the westward and southward migration of nomadic people from their homelands in northwestern China and Mongolia. Although prolonged multidecadal periods of climate-induced low NPP served as tipping points for agricultural and pastoral subsistence systems, the inherent mobility of nomadic communities not only enabled them to adapt to adverse environmental conditions but also facilitated a widespread dispersal of ethnic groups.

This study presents long-term research conducted at the Zhanibek Experimental Station on selecting promising tree and shrub species for landscaping arid regions of Western Kazakhstan. The aim was to identify species resistant to extreme soil and climatic conditions, including solonetz and ameliorated solonetz soils, and to evaluate their viability, growth, and longevity. The methodology included observations of plant morphology, survival rates after planting, growth dynamics, resistance to abiotic stresses, and adaptive responses to environmental conditions. Special attention was given to comparing native and introduced species to determine optimal combinations for sustainable landscaping. The most resilient tree species identified were pedunculate oak (Quercus robur), Siberian elm (Ulmus pumila), white poplar (Populus alba), wild apple (Malus sylvestris), Tatar maple (Acer tataricum), common ash (Fraxinus excelsior), silver birch (Betula pendula), black locust (Robinia pseudoacacia), and common pear (Pyrus communis). Among shrubs, the most устойчивые species included Tatar honeysuckle (Lonicera tatarica), golden currant (Ribes aureum), narrow-leaved sea buckthorn (Hippophae rhamnoides var. angustifolia), multi-branched broom (Cytisus multiflorus), and yellow locust (Robinia pseudoacacia var. flava). Results showed that Siberian elm and Tatar maple performed best on solonetz soils, while steppe xerophytes were more effective on ameliorated soils. Key adaptation mechanisms include extensive root systems, water balance regulation, osmotic adjustment, and synthesis of protective compounds. The findings demonstrate that combining native and introduced species enhances plantation resilience, improves microclimate, and supports effective ecological and urban greening in arid regions.

Floodplain trees and forests are globally threatened by hydrological changes, yet the response of riparian trees to hydroclimatic drivers remain poorly understood in the southern taiga of Western Siberia. This study investigates the relationships between the annual growth of Populus nigra L. and Salix alba L. and hydroclimatic factors in the Tura River – a relatively undisturbed tributary of the Ob with minimal current anthropogenic impact. Tree-ring chronologies (148 years for poplar, 145 years for willow) were developed from 27 poplar and 41 willow trees. Correlation and seasonal window analyses were applied to assess links with temperature, precipitation, soil moisture, runoff, and river discharge. Radial growth of both species is primarily controlled by river discharge, while temperature and precipitation play secondary, species-specific roles. Willow exhibits short-window sensitivity (2–4 months): growth is determined by peak spring discharge (December–May), spring soil moisture (March–April), and late summer temperatures. Poplar demonstrates extended-window sensitivity (5–9 months), relying on sustained soil moisture (February–September) and discharge from January to July. These contrasting strategies imply that willow is more responsive to shifts in spring flood timing, whereas poplar is more vulnerable to reductions in summer discharge. Both species integrate complex hydroclimatic signals (snowmelt-driven discharge, soil moisture storage, seasonal temperatures), making unambiguous single-variable reconstructions difficult. Species-specific assessments are essential for predicting floodplain dynamics and guiding forest restoration efforts under ongoing climate change.

The continuous intensification of human activities has led to a rise in global surface temperatures. However, understanding long-term climate variations and their driving mechanisms in the Changbai Mountains in Northeast China is hindered by the limited duration of observation data and climate reconstructions, especially in the absence of reconstructions using latewood blue intensity. To address this, we constructed a 239-year-long latewood blue intensity chronology of Picea jezoensis. Correlation analysis resulted in a correlation coefficient of 0.648 between the latewood blue intensity of tree-rings and monthly mean temperatures recorded at ChangbaiMeteorological Station during May to September. The reconstruction accounts for 42

Anthropogenic climate change affects regional hydrological cycles and poses significant challenges to the sustainable supply of freshwater. The Central China water tower (CCWT) is the key source region feeding the Yangtze and Yellow Rivers, and its runoff is indispensable for the surrounding mega-city clusters. Here we present a reconstruction of CCWT runoff depth (RD) back to 1595 CE, based on a new dendrochronological network including 100 tree-ring sampling sites and an ensemble averaging approach that combines multiple regression models. Comparison of this reconstruction with similar records from six water tower regions along the Pacific Rim (Mongolian Plateau, Tibetan Plateau TP, Great Dividing Range, Southern and Northern Rocky Mountains, Andes Mountains) revealed that the CCWT provide the most stable water supply, while the TP to be most susceptible to extreme runoff events. Twenty-first century projections indicate generally increasing runoff across most Pacific Rim water towers, whereas the Northern Rocky Mountains are projected to decline substantially. We attribute the differences in runoff variability and projected trends across Pacific Rim water towers to their distinct geographies and synoptic climatic conditions. The long-term runoff reconstructions and projected changes highlighted in this study provide insights for adaptive management strategies in China and all other regions relying on supply from mountain water towers.

Understanding the long-term variability of forest productivity is crucial in the context of climate change. While remote sensing data provide valuable information on vegetation dynamics, their temporal coverage is often limited. Tree-ring width, however, serves as a reliable proxy for reconstructing past forest productivity and extending NDVI records. In this study, we reconstructed the Normalized Difference Vegetation Index (NDVI) for Austrocedrus chilensis forests in northwestern Argentine Patagonia using multi-centennial tree-ring chronologies. A total of 162 wood samples from living trees and 65 from dead trees were used to develop the regional chronology, which exhibited a significant and positive correlation with NDVI from January to March over the period 1981-2019. Based on this relationship, a linear regression model was applied to reconstruct NDVI for these months extending back to 1405. The reconstruction explained 44% of the total NDVI variance and showed significant positive associations with the Standardized Precipitation Evaporation Index (SPEI), the Palmer Drought Severity Index (PDSI), and the Southern Annular Mode (SAM). Long-term cycles in vegetation productivity were detected, potentially linked to solar activity and other low-frequency climate forcings. The results indicate secular changes in forest productivity dynamics, reflecting the influence of ongoing climate change. By providing a multi-century perspective on NDVI variability, this reconstruction offers critical insights into past forest dynamics and establishes a robust baseline for understanding contemporary ecosystem functioning. Moreover, these findings provide a valuable framework for predictive modeling of future productivity responses under changing climatic conditions.

Understanding the spatial distribution of tree growth sensitivity in response to climate change is essential for developing effective adaptive forest management strategies, particularly in vulnerable ecotones and transitional zones. Here, we present a network of 70 tree ring width chronologies from 12 tree species to systematically investigate the radial growth responses to key climatic factors, including temperature, precipitation, and drought (scPDSI), across the North-South transitional zone in China (NSTZ). Our analysis indicates that precipitation in the previous September (r = 0.005 - 0.503), January of the current year (r = 0.001 - 0.297), and late spring to early summer (April to June, r = 0.003 - 0.535) exerts a positive influence on the growth of most trees (chronologies > 50), whereas temperature suppresses tree growth in May (r = -0.443 - -0.004) and December (r = -0.396 - -0.026) of the current year. Further redundancy (RDA) and GeoDetector (GD) analysis indicates that the spatial variability of growth sensitivity is primarily governed by combined geographic, aridity gradients, and species, with local microclimatic variables such as vapor pressure deficit (VPD) and soil moisture exerting comparatively weaker influences. Multi-model projections under the SSP2-4.5 and SSP5-8.5 scenarios suggest that the transitional zone is likely to experience a drier and increasingly heterogeneous eco-climatic regime (the mean coefficient of variation > 0.25). Such changes may intensify the spatial divergence and potential destabilization of tree growth-climate relationships, posing challenges for forest ecosystem long-term sustainability.

Tree-ring data processing often remains operationally fragmented, with file conversion, crossdating evaluation, and chronology aggregation distributed across independent software tools. To address this work-intensive and error-prone analytical separation, we present an integrated Python-based desktop workflow for dendrochronological data processing comprising four applications: RWLUpdaterApp (Ring Width Length Updater), pos2rwlApp, converterApp, and RWLStatsApp. These tools support: i) conversion of POS (CooRecorder coordinate) files to the Tucson ring-width list (RWL) format; ii) multi-format chronology conversion and diagnostics; iii) COFECHA (a widely used crossdating quality-control program)-assisted crossdating checks; iv) interactive correction of problematic series; and v) automated updating and screening of a combined master chronology. The central component, RWLUpdaterApp, provides folder monitoring, duplicate prevention, live editing tools, and an audit trail of chronology changes. Available as ready-to-run executables for both Windows and macOS, the workflow fills an operational gap in traceable, end-to-end chronology management. Rather than replacing established tools, the workflow connects them into a coherent sequence, reducing repetitive manual effort, lowering file-handling errors, and improving transparency and reproducibility of iterative chronology revision.

Although anthropogenic greenhouse gas emissions are widely regarded as the major cause of ongoing global climate change, isolating anthropogenic impacts on climate is difficult due to the internal variability of the climate system and the brevity of the observational record. Here we attempt to discern a human signal in recent climate change using a 400-year reconstruction of the self-calibrating Palmer Drought Severity Index for the southeastern Tibetan Plateau, where current warming is more pronounced than most other places. Our results highlight a trend towards progressively drier conditions, while the most recent drought and wetness events are ranked as the second most severe throughout the entire reconstruction. We conclude that anthropogenic influence on climate in this region, which is clearly detected at the end of the 20th century, will become stronger in the foreseeable future.

As the largest city in northern China and the capital of China, the rapid increases in Beijing's water consumption in recent years have made water resources provision an increasing problem. To rationally allocate water resources, it is important to obtain long-term runoff information in Beijing. In this study we develop a 236-year chronology of tree-ring widths based on cores from Pinus tabuliformis from four sampling sites. The resulting regression model reconstructs December-July runoff of the Yongding River in Beijing, with 49.5% of the variance explained, back to 1786 CE. Among the last 236 years, 1868, 1956, 1991, 1998, 2018, and 2021 were extremely high runoff years; and 1900, 1906, 1999, and 2000 were extremely low runoff years. Comparison of the runoff reconstruction results with climate grid data demonstrated a large magnitude of climate change in North China during the study period. Linkage analysis between the reconstructed runoff and large-scale water vapor indicated that the high runoff years occurred during negative phases of the Pacific Decadal Oscillation, which may be influenced by the East Asian Summer Monsoon. Projections indicate that the flow of the Yongding River will increase in the future. Supported by policies such as the Ecological Water Supply and South-to-North Water Diversion, regional vegetation productivity and Yongding River runoff have increased substantially since 2000. Vegetation growth interacts with runoff volume. It is unclear how long these increases will continue.

Increasing climatic pressures on global forest ecosystems highlight the urgent need to quantify their responses to climate change. This study integrates tree-ring chronologies, Normalized Difference Vegetation Index (NDVI), and climate reanalysis data to investigate vegetation-climate interactions and the role of ocean-atmosphere circulation in mid-latitude Pacific regions. We developed new chronologies for Pinus tabuliformis in northern China and Araucaria araucana in northern Patagonia Argentina, revealing distinct response mechanisms under global warming. Recently, both regions have exhibited rapid tree radial growth, although the growth of A. araucana in northern Patagonia Argentina remains comparatively weaker. P. tabuliformis growth is closely aligned with monsoon precipitation and maintains significant correlations with local NDVI; likewise, A. araucana growth also responds high sensitively to local moisture variability and exhibits stronger coupling with NDVI over the northern Patagonian Plateau during the summer months. Favorable thermal conditions combined with adequate precipitation or snowmelt during spring and summer driver tree growth in both regions. Over the past century, evolving teleconnection patterns suggest that the El Nino-Southern Oscillation (ENSO) has had a diminishing negative impact on P. tabuliformis growth while exerting an increasingly persistent and intensifying positive influence on A. araucana. The Arctic Oscillation (AO) and Southern Annular Mode (SAM) also exhibit significant temporal variations in their impacts across both regions. The findings suggest that the observed forest resilience in northern China and Patagonia represents a crucial ecological positive feedback mechanism, particularly for developing climate adaptation strategies against intensifying heatwaves and drought events.

The April–September maximum temperature in the Greater Caucasus region of Georgia has undergone notable changes, yet extended reconstructions remain scarce. We collected 40 Pinus sylvestris cores from Bakuriani and extracted their blue-intensity (BI) signals, which capture latewood density closely linked to high-season temperature. After chemical treatment and high-resolution scanning, we employed correlation analyses to identify the seasonal temperature signal in BI. Then, we used a linear regression model—validated by local instrumental records from 1950–2020—to reconstruct April–September temperatures back to 1780 CE. Additional superposed epoch analysis tested the reconstruction’s responsiveness to significant volcanic eruptions and solar variability. Our reconstruction strongly correlates with observed data (r = 0.72, p < 0.001), revealing significant warming trends alongside cooling events linked to volcanic aerosols and low solar activity in recent decades. Spatial analyses confirm that the BI-derived temperature variations align well with broader regional climate patterns. Furthermore, CMIP6-based projections under high-emission scenarios suggest possible warming of up to 8.75°C by 2100, highlighting the severity of future climate risks in the region. By integrating BI data, linear regression techniques, and superposed epoch analysis, this research demonstrates the effectiveness of tree-ring proxies in capturing both anthropogenic and natural drivers of climate variability. The resulting 240-year temperature record provides valuable insights into historical climate dynamics, refines model predictions, and underscores the importance of localised, high-resolution data for adaptation planning in the Greater Caucasus region.

The South-to-North Water Diversion Project in China aims to address the unbalanced distribution of water resources between the northern and southern regions, a critical safeguard for sustainable socio- economic and ecological development. In this study, we investigated the hydroclimatic evolution of the water source area and its driving mechanisms using the inflow runoff data at Danjiangkou Reservoir from 1954 to 2013, along with multiple gridded hydroclimatic datasets. Based on the correlations between instrumental runoff data and gridded hydroclimatic variables, we used linear regression to extend the long-term runoff record to the period of 1902–2019. Our results indicate that climate changes, dominated by regional wet-dry cycles, have significant impacts on runoff variations, while the influence of human activities remains comparatively limited. Danjiangkou Reservoir can maintain a balanced base flow, even during the operation of the water diversion project. Preliminary synoptic climatology analyses reveal that runoff variations are mainly driven by the El Niño-Southern Oscillation (ENSO) and the Pacific Walker Circulation (PWC), which affect runoff by altering large-scale ocean-to-continent water vapor processes. This study advances the field by integrating multi-source data with analytical techniques, which enhances understanding of long-term runoff changes in the Danjiangkou Reservoir and their climatic drivers, ultimately supporting sustainable water resource management.

Pacific Walker circulation (PWC) is an important component of tropical atmospheric circulation. Current studies have mainly focused on PWC changes over recent decades and the near future, while less effort has been devoted to long-term PWC variations. In this study, we investigate PWC changes over the last millennium (LM) based on the Community Earth System Model LM Ensemble (CESM-LME). The simulated PWC variations show no significant trend but do reveal decadal fluctuations during the LM, which underestimate the strengthened Little Ice Age (LIA)-Medieval Climate Anomaly (MCA) PWC differences indicated by proxy-based reconstructions. A quantitative estimation of the contributions made to PWC variability from internal variability and external forcing is conducted by using multiple linear regression (MLR) analysis. The internal variabilities contribute approximately 80% to the changes in PWC during the LM, among which the interdecadal Pacific oscillation (IPO) has the largest contribution. In the positive phase of the IPO, the Indo-Pacific sea level pressure (SLP) gradient decreases, and anomalous westerlies occur in the tropical western Pacific, corresponding to a weakened PWC. The relationships between the IPO and PWC show multidecadal-to-centennial fluctua- tions, suggesting that other internal modes or external forcings may have modulated the IPO-PWC relationship. Volcanic forcing is also an important contributor to PWC variability during the LM. The simulated PWC significantly weakens and lasts for 1-2 years after large volcanic eruptions. The El Ni & ntilde;o-like SST pattern and the corresponding zonal SLP gradient lead to the PWC weakening following large volcanic eruptions. SIGNIFICANCE STATEMENT: As one of the most active components of tropical atmospheric circulation, Pacific Walker circulation (PWC) can significantly modulate global climate through atmospheric teleconnections. Previous studies have mainly focused on PWC variability over recent warm periods and future changes. However, understanding of PWC changes is currently lacking due to limited instrumental observations. The last millennium (LM) has a rich archive of proxy records that give us a longer perspective on climate variability and change, which is an excellent period for understanding the long-term mechanisms and changes in PWC. In this study, we use simulations from the CESMLME to quantify the relative importance of internal variability and external forcings to PWC variations during the LM. The simulated PWC variations show no significant trend but decadal fluctuations, which underestimates the reconstructed PWC variations during the LM. The internal variabilities contribute approximately 80% to the changes in PWC, among which the interdecadal Pacific oscillation (IPO) has the largest contribution. External forcing, especially the contribution made by volcanic forcing, is also nonnegligible. Both the positive phase of the IPO and large tropical volcanic eruptions could trigger El Ni & ntilde;o-like SST anomalies, accompanied by a decreased Indo-Pacific SLP gradient and a weakened PWC.

Central Asia, located in the innermost part of the Eurasian continent, has experienced “warming and humidification” in recent decades, with potentially important implications for tree growth in alpine forests, which are critical for regional water reserves. We use nested principal component analysis to assess tree radial growth patterns and reveal significant positive trends since the 20th century across Central Asian alpine forests (0.076 per decade during 1900–2021, p ​= ​0.003). Regional hydroclimatic variations affect the greening of these alpine forests, especially with extreme droughts being the most damaging. Growth acceleration is driven by low-latitude warming, which enhances regional temperatures and precipitation. The warming ocean centers alter atmospheric circulation patterns, leading to more moisture being transported to the Central Asian alpine forests, thereby increasing regional precipitation and promoting tree growth. Our model projections indicate that growth rates will continue to rise in the future. However, unprecedented warming may eventually lead to growth deterioration if negative effects, such as insufficient precipitation, occur due to breakdown signs of positive feedback mechanisms, such as moisture transport driven by low-latitude warming. Our study highlights the beneficial, but not unlimited, influences of climate warming on tree growth in Central Asian alpine forests, with implications for the sustainability of water resources. However, as urban and agricultural demands escalate, a holistic, long-term perspective is recommended to mitigate the adverse effects of temperature increases.