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Dendrochronology is a discipline that uses tree rings to study the history and dynamics of the earth system, such as climate change, natural disasters, and human activities. This study aims to evaluate the development of dendrochronology and its track in China from 1990 to 2022 using a bibliometric analysis approach. We screened the Web of Science Core Collection for documents related to dendrochronology and analyzed them according to indicators related to production, cooperation, citation, and keywords. Our study revealed that the number of dendrochronological publications increased continuously, reaching more than 800 in 2021, with the USA and China being the top two countries. The cooperation network of dendrochronology was mainly centered between North America and Europe, with China having a moderate level of collaboration with other countries and regions like the USA and Canada. Comprehensive research has been conducted within diverse fields of dendrochronology in the world and in China, but dendrochronological research focusing on forestry and climatology represented a slightly higher proportion of research originating from China. The integration of dendrochronology with other disciplines and techniques, such as remote sensing, artificial intelligence, and modeling, may be hotspots in future research, as indicated by the increasing co-occurrence analysis of keywords in the most recent years. This study suggests that Chinese Dendrochronology still requires improved international collaboration, diversified research topics beyond climate reconstructions, and more emphasis on tree-ring methods to advance this discipline globally, despite of increasing rank of publications in the past decade. [ABSTRACT FROM AUTHOR]

Forest fires are an important factor shaping Mediterranean ecosystems and determine the distribution of different species. Information about past forest fires can be obtained with pyrodendroecology. Here, we present a fire history for three sites in the mountain forest belt on the island of Corsica in the Mediterranean Basin. The dating of scars from cores, stem discs, and wedges from 101 pine trees (Pinus nigra and Pinus pinaster) allowed the reconstruction of six definite fire events between 1800 and 2017. Additionally, we reconstructed the spatial extent of a large fire event at AD 2000 with remote sensing data. The study sites are affected by different types of fires. The even-aged forest structure at two sites is clear evidence of past lethal fires, whereas the old-growth Pinus nigra forest at the third site represents the final stage of succession under current climate conditions. The current distribution of both pine species can at least partly be regarded as a result of varying fire frequency at different sites. Although Pinus pinaster stands dominate in areas with frequent fires and can even replace Pinus nigra in cases of high fire frequency, Pinus nigra dominates in areas with low fire frequencies. [ABSTRACT FROM AUTHOR]

Background and Aims Annually resolved biological climate proxies beyond the altitudinal and latitudinal distribution limit of trees are rare. In such regions, several studies have demonstrated that annual growth rings of dwarf shrubs are suitable proxies for palaeoclimatic investigations. In High Asia, the pioneer work of Liang et al. (Liang E, Lu X, Ren P, Li X, Zhu L, Eckstein D, 2012. Annual increments of juniper dwarf shrubs above the tree line on the central Tibetan Plateau: a useful climatic proxy. Annals of Botany 109 : 721–728) confirmed the suitability of shrub growth-ring chronologies for palaeoclimatic research. This study presents the first sensitivity study of an annually resolved δ18O time series inferred from Wilson juniper (Juniperus pingii var. wilsonii) from the northern shoreline of lake Nam Co (Tibetan Plateau). Methods Based on five individual dwarf shrub discs, a statistically reliable δ18O chronology covering the period 1957–2009 was achieved (expressed population signal = 0.80). Spearman's correlation analysis between the δ18O chronology and climate variables from different sources was applied. In a first step, the suitability of various climate data was evaluated. Key Results Examinations of climate–proxy relationships revealed significant negative correlations between the δ18O shrub chronology and summer season moisture variability of the previous and current year. In particular, relative humidity of the previous and current vegetation period significantly determined the proxy variability (ρ = −0.48, P < 0.01). Furthermore, the δ18O variability of the developed shrub chronology significantly coincided with a nearby tree-ring δ18O chronology of the same genus (r = 0.62, P < 0.01). Conclusions The δ18O shrub chronology reliably recorded humidity variations in the Nam Co region. The chronology was significantly correlated with a nearby moisture-sensitive tree-ring δ18O chronology, indicating a common climate signal in the two chronologies. This climate signal was likely determined by moisture variations of the Asian summer monsoon. Local climate effects were superimposed on the supra-regional climate signature of the monsoon circulation. Opposing δ18O values between the two chronologies were interpreted as plant-physiological differences during isotopic fractionation processes. [ABSTRACT FROM AUTHOR]

The response of the growing season to the ongoing global warming has gained considerable attention. In particular, how and to which extent the growing season will change during this century is essential information for the Tibetan Plateau, where the observed warming trend has exceeded the global mean. In this study, the 1960-2014 mean length of the tree-ring growing season (LOS) on the Tibetan Plateau was derived from results of the Vaganov-Shashkin oscilloscope tree growth model, based on 20 composite study sites and more than 3000 trees. Bootstrap and partial correlations were used to evaluate the most significant climate factors determining the LOS in the study region. Based on this relationship, we predicted the future variability of the LOS under three emission scenarios (Representative Concentration Pathways (RCP) 2.6, 6.0, and 8.5, representing different concentrations of greenhouse gasses) derived from 17 Earth system models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The averaged LOS on the Tibetan Plateau is 103 days during the period 1960-2014, and April-September minimum temperature is the strongest factor controlling the LOS. We detected a general increase in the LOS over the twenty-first century under all the three selected scenarios. By the middle of this century, LOS will extend by about 3 to 4 weeks under the RCPs 2.6 and 6.0, and by more than 1 month (37 days) under the RCP 8.5, relative to the baseline period 1960-2014. From the middle to the end of the twenty-first century, LOS will further extend by about 3 to 4 weeks under the RCPs 6.0 and 8.5, respectively. Under the RCP 2.6 scenario, however, the extension reaches a plateau at around 2050 and about 2 weeks LOS extension. In total, we found an average rate of 2.1, 3.6, and 5.0 days decade−1 for the LOS extension from 2015 to 2100 under the RCPs 2.6, 6.0, and 8.5, respectively. However, such estimated LOS extensions may be offset by other ecological factors that were not included into the growth model. The estimated lengthening of the growing season could substantially affect carbon sequestration and forest productivity on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Forests provide fundamental ecosystem services. Environmental changes are predicted to affect forest growth directly through increased environmental stressors, and indirectly by amplifying disturbance. To increase our understanding of effects of environmental changes and disturbance on Afromontane forest growth, we used tree-ring data collected from Juniperus procera trees from church forests in the northwest highlands of Ethiopia. We used structural change models to detect structural shift in growth trends. We applied Linear Mixed Effect Models (LMM) to compare growth rate differences between successive tree generations. The running mean method and radial growth pattern analysis were used to detect disturbance events. Three groups of generations were identified based on Basal Area Increment (BAI) rates. There are significant differences (χ 2  = 204.64, P < .001) among generations in pace of BAI, indicating that old generation trees grew at a slower pace than younger ones. Radial growth patterns were homogeneous for the old generation, but diverse in young trees. The observed high growth rates in the younger generation may have a negative effect on the longevity of the individuals and positively affect carbon accumulation in the biomass. Disturbance was detected in all generations, but worsened in the 20th century. About 35% of disturbances matched with climate extreme events, providing evidence that the disturbance is both human-induced (i.e., site-specific) and climate-induced. Thus, forest management plans should emerge from a sound understanding of climate-forest-human interaction. [ABSTRACT FROM AUTHOR]

Phenological responses of vegetation to climate, in particular to the ongoing warming trend, have received much attention. However, divergent results from the analyses of remote sensing data have been obtained for the Tibetan Plateau (TP), the world's largest highelevation region. This study provides a perspective on vegetation phenology shifts during 1960-2014, gained using an innovative approach based on a well-validated, process-based, tree-ring growth model that is independent of temporal changes in technical properties and image quality of remote sensing products. Twenty composite site chronologies were analyzed, comprising about 3,000 trees from forested areas across the TP. We found that the start of the growing season (SOS) has advanced, on average, by 0.28 d/y over the period 1960-2014. The end of the growing season (EOS) has been delayed, by an estimated 0.33 d/y during 1982-2014. No significant changes in SOS or EOS were observed during 1960-1981. April-June and August-September minimum temperatures are the main climatic drivers for SOS and EOS, respectively. An increase of 1 °C in April-June minimum temperature shifted the dates of xylem phenology by 6 to 7 d, lengthening the period of tree-ring formation. This study extends the chronology of TP phenology farther back in time and reconciles the disparate views on SOS derived from remote sensing data. Scaling up this analysis may improve understanding of climate change effects and related phenological and plant productivity on a global scale. [ABSTRACT FROM AUTHOR]

Dendrochronological methods have been used to reconstruct insect outbreaks, yet the application has been scarce in the high Asia. We compiled tree-ring data from 4 host (Larix potaninii) and 4 non-host (Abies and Picea) sites in the central Hengduan Mountains, southwestern China. We assessed site-specific growth-climate responses and applied two methods to detecting larch insect defoliation events during the past 250 years. Compared with the non-host chronologies, larch trees (host) showed periodic reduction in radial growth, which may be associated with outbreaks of a larch defoliator. Synchronously, growth reductions was found for three low-elevation sites, such as during 1783–1790, 1846–1850, 1860–1865, 1873–1878, 1900–1909, 1939–1945, 1965–1970 and 1981–1986. However, these periods of outbreaks differ from those of a high-elevation site. With spectral analyses, we found 11–13 years frequency domains for three low-elevation larch chronologies, while 7–9 year peaks presented one high-elevation site. Contrastively, no significant frequency domains within the same periodicity were found in ring-width chronologies of co-occurring non-host species. We provide tree-ring evidence that larch trees growing in the central Hengduan Mountains have been infected by insect defoliators repeatedly. We suggest that appropriate approaches should be applied to correct insect-defoliation signals when using larch tree-ring data as a climatic proxy. [ABSTRACT FROM AUTHOR]

Stable isotopes in wood cellulose of tree rings provide a high-resolution record of environmental conditions, yet intra-annual analysis of carbon and oxygen isotopes and their associations with physiological responses to seasonal environmental changes are still lacking. We analyzed tree-ring stable carbon (δ13C) and oxygen (δ18O) isotope variations in the earlywood (EW) and latewood (LW) of pines from a secondary forest (Pinus kesiya) and from a natural forest (Pinus armandii) in southwestern China. There was no significant difference between δ13CEW and δ13CLW in P. kesiya, while δ13CEW was significantly higher than δ13CLW in P. armandii. For both P. kesiya and P. armandii, δ13CEW was highly correlated with previous year's δ13CLW, indicating a strong carbon carry-over effect for both pines. The intrinsic water use efficiency (iWUE) in the earlywood of P. armandii was slightly higher than that of P. kesiya, and iWUE of both pine species showed an increasing trend, but at a considerably higher rate in P. kesiya. Respective δ13CEW and δ13CLW series were not correlated between the two pine species and could be influenced by local environmental factors. δ13CEW of P. kesiya was positively correlated with July to September monthly mean temperature (MMT), whereas δ13CEW of P. armandii was positively correlated with February to May MMT. Respective δ18OEW and δ18OLW in P. kesiya were positively correlated with those in P. armandii, indicating a strong common climatic forcing in δ18O for both pine species. δ18OEW of both pine species was negatively correlated with May relative humidity and δ18OEW in P. armandii was negatively correlated with May precipitation, whereas δ18OLW in both pine species was negatively correlated with precipitation during autumn months, showing a high potential for climate reconstruction. Our results reveal slightly higher iWUE in natural forest pine species than in secondary forest pine species, and separating earlywood and latewood of for δ18O analyses could provide seasonally distinct climate signals in southwestern China. [ABSTRACT FROM AUTHOR]

Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. While the former can often be quantified by detailed wood anatomical analyses, the latter are often treated as qualitative features or as binary variables (present/absent). Macroscopic tree-ring features can be quantified in terms of frequency, intensity, or classified according to their position within a tree ring, like intra-annual density variations (IADFs) in conifers or frost rings in earlywood or latewood. Although some of these tree-ring features, like e.g. missing rings or IADFs are often seen as anomalies, hampering dendrochronologists to perform proper crossdating of tree-ring series, many of these properties are formed under extreme environmental stress or heavy impact, and could mark these extreme events by the manifestation in the wood anatomical structures throughout the lifespan of trees. The described tree-ring features form discrete time-series of extreme events. For example, flood rings may be marked by lunar-shaped earlywood vessels or enlarged latewood vessels in ring-porous oaks. White earlywood rings and light rings indicate reduced cell wall thickness and lignification occurring in very cold years. Frost rings result from cambial cell death during abrupt cooling events in the growing season. Missing rings and IADFs are mainly caused by drought events. Characteristic variations in earlywood vessel size, shape, or number in ring-porous oak species are markers for flood events, defoliation, heat stress, or drought. Traumatic resin ducts may be triggered by a range of biotic or environmental stressors, including wounding, fires or mechanical factors. Reaction wood is indicative of mechanical stress, often related to geomorphic events. In many cases anatomical responses are unspecific and may be caused by different stressors or extreme events. Additionally, the sensitivity of trees to form such features may vary between species, or between life stages within one species. We critically evaluate the indicative value of different wood anatomical tree-ring features for environmental reconstructions. [ABSTRACT FROM AUTHOR]

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Extreme climatic events such as droughts are likely to result in huge and long-lasting effects on regional ecosystem health if large numbers of foundation tree species continue to die. Although deforestation is severe in the Ethiopian highlands, some remnants of dry afromontane forests still exist. However, the resilience of these forests under climate change scenarios is unknown. Therefore, we studied (1) the extent and spatial patterns of standing dead stems along an elevational gradient and (2) the effects of dieback on forest carbon sequestration potential and aboveground carbon stocks, in Juniperus procera and Olea europaea dominated dry afromontane forest in northern Ethiopia, using allometric models combined with tree ring analysis. Juniperus procera and Olea europaea constitute 67% of the total tree population. Tree dieback affected a quarter of the total population. This loss is critical because 92.2% of snags belong to J. procera and O. europaea , which are the foundation species of the study forest. The total estimated mean aboveground C-stock was 19.3 (±3.9) Mg C ha −1 . Of this estimate, snags contributed 34.5% of total C-stock. The estimated annual C-sequestration potential of the study forest was 0.33 (±0.03) Mg C ha −1 year −1 , which is 27% less when compared to the pre-tree dieback C-sequestration potential. We found a decreasing trend in tree dieback with increasing elevation, which implies that the aboveground C-stocks and climate change mitigation potentials of the forest, was highly affected at lower elevations which is the drier part of the landscape. Tree ring analysis showed that trees reach medium-sized stem diameter (i.e., 20–25 cm) after no less than 100 years, indicating that the effect of forest dieback on C-sequestration potential and ecosystem function is long-lasting. Our results provide information on the magnitude of tree dieback and its long-lasting impact on forest carbon fluxes and forest ecosystem services. Evidently, the results substantiate the importance of protecting such forest to maintain the quality of the environment and to reduce efforts and cost for forest restoration after major loss. Finally, the information gained by this study provides baseline information for comparison of future carbon sequestration estimates. [ABSTRACT FROM AUTHOR]

Knowledge of Asian monsoon variability remains limited because of sparse instrumental data available only for short time series. Here, an updated tree-ring width record covering the period ad 1037–2009 was developed for the south-central Tibetan Plateau (TP). Correlation analysis revealed a significant relationship (r = 0.71) between the tree-ring index and annual (previous July to current June) precipitation series for the instrumental period 1963–2008, which accounts for 50.41% of the rainfall variability. Based on a linear regression model, the longest available regional precipitation history was reconstructed. Spatial correlation between tree ring width and annual precipitation data from previous July to current June indicates that the reconstruction is representative of precipitation changes on the south-central TP. Regional wet conditions occurred during ad 1095–1161, 1376–1403, 1414–1446, 1518–1537, 1549–1572, 1702–1757, 1848–1878 and 1891–1913, while dry periods were identified during ad1189–1242, 1256–1314, 1329–1357, 1470–1491, 1573–1623, 1636–1686, 1761–1821, 1823–1847, 1879–1890 and 1931–1985. The negative correlation between our reconstructed precipitation and India monsoon rainfall series indicates the seesaw pattern over northern and southern monsoon Asia. It is suggested that solar radiation-induced sea surface temperature (SST) anomalies over the tropical Pacific influence regional rainfall patterns. The degree of this influence has been stable at the multidecadal scale during the past 1000 years. [ABSTRACT FROM AUTHOR]

We present a 620-year long ring width record from the middle Qilian Mountains, where it is presently controlled by the Westerlies. The chronology was developed from Qilian juniper ( Sabina przewalskii) growing at sites near the western distribution limit of the species in the northern Qilian Mountains, Gansu Province, China. A linear regression model between ring width and annual (July to June) precipitation accounts for 34.9% of the observed instrumental precipitation variance during the period 1952 to 2007. Spatial correlation analyses between the reconstruction and gridded precipitation data shows that the annual precipitation reconstruction captures regional climatic variations over the Qilian Mountains and the nearby Hexi Corridor. We also show the scaled standard chronology adjusted to the mean and variance of the instrumental data. Relatively wet periods are identified for AD 1390-1413, 1425-1450, 1530-1649, 1792-1920, 1937-1949 and 1980-1985. Dry conditions prevailed during AD 1414-1424, 1451-1529, 1650-1791, 1921-1936, 1950-1979 and 1986-2007. In comparison with the regression-based reconstruction, the scaled reconstruction indicates considerably wetter conditions during 1390-1413, 1425-1450, 1570-1630 and 1790-1920. The interval AD 1451-1529 was the most intense and longest drought epoch in the Hexi Corridor over the past six centuries. This drought was not only recorded in the Qilian Mountains but also occurred in northern and eastern China. It might be caused by a substantial weakening of the Asian summer monsoon induced by the joint effects of solar and volcanic activities at that time. Our results also suggest that the Hexi Corridor was under the control of the Asian monsoon circulation on inter-decadal to centennial timescales in the past centuries. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Abstract: The climatological signal of δ 18O variations preserved in ice cores recovered from Puruogangri ice field in the central Tibetan Plateau (TP) was calibrated with regional meteorological data for the past 50 years. For the period AD 1860–2000, 5-yearly averaged ice core δ 18O and a summer temperature reconstruction derived from pollen data from the same ice core were compared. The statistical results provide compelling evidence that Puruogangri ice core δ 18O variations represent summer temperature changes for the central TP, and hence regional temperature history during the past 600 years was revealed. A comparison of Puruogangri ice core δ 18О with several other temperature reconstructions shows that broad-scale climate anomalies since the Little Ice Age occurred synchronously across the eastern and southern TP, and the Himalayas. Common cold periods were identified in the 15th century, 1625–1645 AD, 1660–1700 AD, 1725–1775 AD, 1795–1830 AD, 1850–1870 AD, 1890–1920 AD, 1940–1950 AD, and 1975–1985 AD. The period 1725–1775 AD was one of the most prolonged cool periods during the past 400 years and corresponded to maximum Little Ice Age glacier advance of monsoonal temperate glaciers of the TP. [Copyright &y& Elsevier]

Since recent drought events have already caused severe damage to trees and droughts in the near future are expected to occur even more frequently, this study investigated the response of forest ecosystems to changing climate conditions in the topographically complex region of Bavaria, southeast Germany. For this purpose, climate–growth relationships of important European deciduous and coniferous tree species were investigated over the past 50 years at three middle mountain ranges and corresponding basins. A response analysis between tree-ring width and climate variables was applied to detect modifications in tree responses comparing two 25-year periods at individual forest sites. Furthermore, tree responses to climatic extreme years and seasons were analyzed using a superposed epoch analysis. The results showed that Scots pine (Pinus sylvestris) proved to be the most vulnerable and least drought-resistant of all investigated tree species. Likewise, Norway spruce (Picea abies) and European beech (Fagus sylvatica) revealed a higher drought sensitivity over the past 25 years, even though an extended growing season partially improved tree growth at high-elevation sites. In conclusion, all studied tree species were affected by drought events, even at humid high-elevation sites. Correlations with daily climate variables confirmed that even short-term weather conditions could strongly influence trees' radial growth. Tree responses to climate conditions have shifted significantly between past and present periods but vary considerably among sites and are generally stronger in humid regions than in already dry areas. [ABSTRACT FROM AUTHOR]

Identifying what determines the high elevation limits of tree growth is crucial for predicting how treelines may shift in response to climate change. Treeline formation is either explained by a low-temperature restriction of meristematic activity (sink limitation) or by the photosynthetic constraints (source limitation) on the trees at the treeline. Our study of tree-ring stable isotopes in two Tibetan elevational transects showed that treeline trees had higher iWUE than trees at lower elevations. The combination of tree-ring δ13C and δ18O data further showed that photosynthesis was higher for trees at the treeline than at lower elevations. These results suggest that carbon acquisition may not be the main determinant of the upper limit of trees; other processes, such as immature tissue growth, may be the main cause of treeline formation. The tree-ring isotope analysis (δ13C and δ18O) suggests that Tibetan treelines have the potential to benefit from ongoing climate warming, due to their ability to cope with co-occurring drought stress through enhanced water use efficiency. [ABSTRACT FROM AUTHOR]

To develop multi-century stable isotope chronologies from tree rings, pooling techniques are applied to reduce laboratory costs and time. However, pooling of wood samples from different trees may have adverse effects on the signal amplitude in the final isotope chronology. We tested different pooling approaches to identify the method that is most cost-efficient, without compromising the ability of the final chronology to reflect long-term climate variability as well as climatic extreme years. As test material, we used δ18O data from juniper trees (Juniperus polycarpus) from Northern Iran. We compared inter-tree and shifted 5-year blocks serial pooling of stable isotope series from 5 individual trees and addition of one single series to a shifted serial pooled chronology. The inter-tree pooled chronology showed the strongest climate sensitivity and most synchronous δ18O variations with the individual tree ring analyses, while the shifted block chronologies showed a marked decline in high-frequency signals and no correlations with climate variables of the growth year. Combinations of block-pooled and single isotope series compensated the high-frequency decline but added tree-individual climatic signals. Therefore, we recommend pooling calendar synchronous tree rings from individual trees as a viable alternative to individual-tree isotope measurements for robust paleoclimate reconstructions. [ABSTRACT FROM AUTHOR]

Highlights • Vessel chronologies of two ecologically contrasting tropical tree species were developed. • Temperature had significant effects on vessel variables. • Previous year precipitation influenced vessel features through carbon carryover effects. Abstract Trees can adjust their hydraulic architecture by adjusting vessel size and frequency in response to stressful environmental condition. Little is known about the long term adjustment of tropical moist forest trees to changing environment. Here we develop the standard chronologies of seven vessel features and radial growth of two ecologically contrasting South Asian moist forest trees, Toona ciliata M. Roem. and Lagerstroemia speciosa (L.) Pers. and evaluate their hydraulic response to short term climate variability and long term climate variations. Measurements of vessel variables were performed on digital microscopic images. Standard dendrochronological procedure were applied to develop vessel and ring-width chronologies. Relationships among the chronologies and their interaction with climate variables were assessed by Principal Component Analysis (PCA), bootstrap correlations and moving correlations. Pre-monsoon temperature negatively influenced ring-width (RW) and positively influenced vessel density (VD) in T. ciliata. Mean vessel area (MVA) was negatively related with prior year monsoon temperature. In L. speciosa , previous year temperatures and precipitation showed strong correlations with vessel features and radial growth in the following growing season, probably due to carbon carry over effects. Current year October precipitation was positively related with MVA in both species. Differences in functional traits might have caused the observed variation in hydraulic strategies between the two study species. Our analyses suggest that cellular dendrochronology can be used to understand the long-term hydraulic responses of functionally different moist forest trees to climatic changes which is relevant for forest management under changing climate conditions. [ABSTRACT FROM AUTHOR]

This study investigates the dendroclimatic potential of tree species in a tropical dry forest in southern Ecuador. From 10 selected tree species, Bursera graveolens and Maclura tinctoria exhibited distinct annual and cross-datable tree-rings. It was possible to synchronize individual tree-ring series and to establish two tree-ring chronologies of 203 and 87 years length, respectively. The characteristic ENSO frequency band is reflected in wavelet power spectra of both chronologies. Both species show a strong correlation between ring width and precipitation of the wet season (January–May). Strong El Niño events (1972, 1983 and 1998) lead to strong growth responses in the tree-ring chronologies, whereas ‘normal’ ENSO events do not trigger long-lasting growth responses. The first ring-width based wet-season precipitation reconstruction for the past 103 years was developed. Statistical and spatial correlation analysis verified the skills of the reconstructed precipitation which captures a great part of the Rainfall Index over the land area of Ecuador and the equatorial Pacific. Furthermore, teleconnections with central Pacific precipitation and SST patterns were found. [ABSTRACT FROM AUTHOR]

Abstract: We established three tree-ring width chronologies from oak species in the central Zagros Mountains, Iran, where instrumental climate data only cover a short period (1951–2010). Due to high similarity of the individual ring-width series, we included all studied sites in a regional chronology covering 306years. Correlation functions with regional climate data revealed significant positive correlations (p<0.01) with total precipitation from previous October to current May. Thus, we reconstructed regional precipitation variability over the period 1840–2010 based on linear regression between regional tree growth and climate data. Dry conditions prevailed in the 1840s, 1850, 1870s, 1880s, 1900s, 1920s, 1940s, 1960s, 1980s and 1999–2003. In comparison to wet periods, the number and the intensity of dry periods have increased during the 1840–2010 study period. Many of the reconstructed wet years coincided with major El Niño events. Inverse association between the Southern Oscillation Index (SOI) and the reconstructed precipitation during the common period (1877–2010) revealed that the Southern Oscillation Index (SOI) plays an important role in regional precipitation variability. [Copyright &y& Elsevier]

• Our approach successfully removed the effect of insect outbreak on the tree-ring width chronology. • The approach improved growth-climate relationships, especially for summer (June-September) temperatures. • 313-year-long summer temperature reconstruction showed a wiggly trend before the 1980 s before experiencing a rapid warming trend. • The insect outbreaks can result in biased climate prediction, especially in cold periods. Insect outbreaks are proven to harm trees, reducing their biomass accumulation due to the defoliation of leaves during the growing season. Various defoliators are responsible for the formation of extremely narrow tree rings in different tree species. In climate reconstructions based on tree-ring width, such narrow rings are often considered as noise, because their formation is not entirely caused by climatic conditions. Thus, the impact of defoliators should be removed (nullified) for unbiased climate reconstructions. This study mainly describes a statistical approach to disentangle the effects of Larch budmoth(LBM) (Zeiraphera diniana) and climate for an unbiased temperature reconstruction in the Bai-Ma mountain area in Southwest China using Larix potaninii. After applying our new approach, growth-climate relationships improved significantly (p < 0.05), especially with minimum temperature during the growing season (June-September). The resulting temperature reconstruction (BTmin) covers the period 1712–2020 CE (313 years). Our final temperature reconstruction for the Bai-Ma area showed a wiggly trend from 1712 to 1980, with some cool periods (1791–1853 and 1888–1930) and warm episodes (1724–1745, 1854–1887, 1950–1967). During the recent 50 years, BTmin reveal an alarming warming trend of up to 0.4 °C per decade. We also observed a strong coherency of BTmin with regional temperature series. Furthermore, we detected a differential effect of various climate modes, with the most substantial impact of the Atlantic Multidecadal Oscillation (AMO) on BTmin (p < 0.01). Interestingly, the Pacific Decadal Oscillation (PDO) showed a coupled effect along with AMO on BTmin. As revealed in this study, removing the LBM effect improved the chronology's climate sensitivity, leading to a more robust transfer function and in terms of insect infestations unbiased climate reconstructions. Thus, it is recommended to check ring-width data for any periodicity potentially related to insect outbreaks and correct the original data before using tree-ring chronologies for climate reconstruction. [ABSTRACT FROM AUTHOR]

Monsoonal-affected temperate glaciers in the eastern Nyainqêntanglha Range, southeastern Tibet, are highly sensitive to climate change. Knowledge about their late Holocene dynamics is still, however, widely lacking. The few studies on glacial chronology which are available for this region tend to mainly focus on dating results without sufficiently considering the geomorphological setting, often leading to misinterpretations in this complex high mountain environment. In this study, two selected glacier forelands are investigated using a multi-proxy approach encompassing detailed geomorphological mapping, dendrochronology, sedimentology, and optically stimulated luminescence as well as radiocarbon dating. The starting point was the creation of a consistent morphosequence which was validated by remote sensing of further glacier forelands from the wider region. Similarities and differences between the investigated settings were analyzed in detail to identify the relevant morphological and topoclimatic forcing mechanisms. We found evidence of climatic events affecting the whole region during the Little Ice Age, resulting in similar configurations and numbers of moraines. The geomorphological settings of the glacier forelands are, however, remarkably different, making investigations of the landform and sediment configuration an indispensable condition for their interpretation. Subsequently, constraints from different methods of relative and numerical dating were evaluated critically and included into a conceptual chronosequence if applicable. Our results suggest that the late Holocene maximum glacier advance comprised several successive advances from mid-17th to mid-18th century. None of our observations supports an earlier Neoglacial advance reaching further than the LIA maximum. After the LIA maximum, continued retreat that was only interrupted by short phases of stability followed, as evidenced by 2–3 recessional moraines in the investigated settings. [ABSTRACT FROM AUTHOR]