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Subtropical forests are an important carbon sink, yet our understanding on tree growth response to inter-annual climate variability remains limited. This study investigated the growth-climate relationships of four evergreen broad-leaved tree species (Stewartia pteropetiolata W. C. Cheng, Schima noronhae Reinw. ex Bl. Bijdr, Machilus gamblei King ex J. D. Hooker, and Machilus yunnanensis Lec) in the subtropical evergreen broad-leaved forests (EBFs) in the Ailao Mountains of Yunnan province, southwest China. We constructed tree ring-width residual chronologies for each species and correlated them with daily and monthly climate data. Ring-width chronologies of S. pteropetiolata and S. noronhae were positively correlated with precipitation, relative humidity, and self-calibrated Palmer drought index (scPDSI) during autumn of the previous year and spring-to-early summer of the current year, indicating that these two Theaceae species were sensitive to moisture availability. Tree radial growth of two Machilus species was primarily limited by excessive precipitation and dense cloud cover during the rainy season in this middle montane cloud forest. Moving correlations between climate variables and radial growth of all species were temporally unstable, with a weakening response to climate variability in recent decades. We highlight the dendroclimatic potential of evergreen broad-leaved tree species in moist subtropical forests. The findings offer a pertinent perspective, emphasizing the necessity of separately considering distinct ecological indicators for trees in order to obtain a comprehensive understanding of climate-growth responses within highly diverse subtropical forests. • Radial growth of two Theaceae species showed moisture sensitivity during previous autumn and current spring-to-early summer. • The growth of Machilus spp. was mainly limited by excessive precipitation and cloud cover during the rainy season. • We highlight the dendroclimatic potential of evergreen broad-leaved tree species in moist subtropical forests. [ABSTRACT FROM AUTHOR]

Asian summer monsoon (ASM) variability and its long-term ecological and societal impacts extending back to Neolithic times are poorly understood due to a lack of high-resolution climate proxy data. Here, we present a precisely dated and well-calibrated treering stable isotope chronology from the Tibetan Plateau with 1- to 5-y resolution that reflects high- to low-frequency ASM variability from 4680 BCE to 2011 CE. Superimposed on a persistent drying trend since the mid-Holocene, a rapid decrease in moisture availability between ~2000 and ~1500 BCE caused a dry hydroclimatic regime from ~1675 to ~1185 BCE, with mean precipitation estimated at 42 ± 4% and 5 ± 2% lower than during themid-Holocene and the instrumental period, respectively. This second-millennium-BCE megadrought marks the mid-to late Holocene transition, during which regional forests declined and enhanced aeolian activity affected northern Chinese ecosystems. We argue that this abrupt aridification starting ~2000 BCE contributed to the shift of Neolithic cultures in northern China and likely triggered human migration and societal transformation. [ABSTRACT FROM AUTHOR]

Climatic harshness is expected to increase at higher elevations; however, elevational trends of tree radial growth response of high-elevation forests to climate change need to be investigated at different locations because of existing local variability in site-specific climatic conditions. We developed tree-ring width chronologies of Yunnan fir ( Abies georgei ) along elevation gradients at two sites in the central Hengduan Mountains (HM). High-elevation forests of A. georgei showed growth synchronicity and common growth signals along elevation gradients, indicating a common climatic forcing, although tree radial growth rates decreased with increasing elevation. Radial growth of Yunnan fir showed positive correlations with summer temperatures and February precipitation and moisture availability, but were negatively correlated with spring temperatures. The strongest positive relationship indicated summer (July) mean and minimum temperatures are the most important growth determining climatic factors for tree radial growth in the cold environment of HM, and this relationship revealed a clear elevational trend with stronger correlations at higher altitudes. In contrast, tree radial growth was negatively correlated with June precipitation and moisture availability. The whole study period 1954–2015 was split in two sub-periods of equal length. Comparing the early sub-period (1954–1984) to the later sub-period (1985–2015), tree growth response to the summer temperatures strongly increased, while it became weaker to June precipitation and moisture availability. High-elevation Yunnan fir forests in the HM currently benefit from elevated growing season temperatures under humid summer conditions. However, increasing temperatures may induce drought stress on tree radial growth if the observed decreasing trend in humidity and precipitation continues. [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]

ABSTRACT In this study, we examine the relationship between short- and long-term effects of precipitation deficits, integrated in a drought index called 'Joint Deficit Index ( JDI)', and tree-ring growth of oak trees ( Quercus infectoria) in the Javan-Roud region, Kermanshah province (Iran). Precipitation data from regional climate stations cover the period 1968-2008, and the tree-ring width chronology span over the period 1818-2008. This chronology is highly correlated with the JDI (January-September) series for the instrumental period ( P < 0.01). Therefore, the regional JDI was reconstructed using a simple linear regression model which accounts for 40% of JDI (January-September) variances over the instrumental period. Reconstructed drought periods persisted on average for 2 years, and some severe drought lasted for 3-4 years. However, one 7-year drought was reconstructed over the period 1923-1929. The most severe droughts occurred in the periods 1960-1963 and 1999-2001. While the reconstructed JDIs have no significant correlation with the North Atlantic Oscillation, a significant negative correlation was observed with the Southern Oscillation Index in November and December of pre growth during the common period from 1877 to 2008. An appropriate agreement was found between our reconstruction and historical famines in Iran and also reconstructed results from neighbouring countries in the east (China) and west (Turkey and other countries around the Mediterranean Sea), particularly for the most severe droughts. The highest agreement was achieved with regions in the pathway of westerly storm tracks travelling via the Mediterranean region into Iran. [ABSTRACT FROM AUTHOR]

Precipitation in the monsoon shadow zone of the western Himalayan region, largely under the influence of mid-latitude westerlies, is the dominant regional socioeconomic driver. Current knowledge of long-term regional precipitation variability is scarce due to spatially and temporally limited weather and high-resolution proxy climate records. We developed the first boreal spring precipitation reconstruction for the western Himalaya covering the last millennium (1030–2011 C.E.). The annually resolved reconstruction is based on a large tree-ring data set of Himalayan cedar ( Cedrus deodara ) and neoza pine ( Pinus gerardiana ) from 16 ecologically homogeneous moisture stressed settings in Kinnaur, western Indian Himalaya. The precipitation reconstruction revealed persistent long-term spring droughts from the 12th to early 16th century C.E. and pluvial from the late 16th century C.E. to recent decades. The late 15th and early 16th centuries (1490–1514 C.E.) displayed the driest episode, with precipitation being ∼15% lower than the long-term mean. The early 19th century (1820–1844 C.E.) was the wettest period of the past millennium, with mean precipitation ∼13% above the long-term mean. The reconstructed boreal spring precipitation from the western Himalaya revealed large-scale consistency with hydrological records from westerly dominated regions in Central Asia, indicating synoptic-scale changes in atmospheric circulation during the major part of the Medieval and Little Ice Age periods. Protracted droughts in Central Asia could have caused severe contraction of the regional economy, as indicated by striking coherence of reconstructed drought periods and historic social upheavals and invasions of India from Central and Western Asian invaders. Vulnerability to climatic extremes underpins the need to develop a better understanding of the temporal and spatial variability in regional hydroclimate in order to devise viable water resource management plans. [ABSTRACT FROM AUTHOR]

Variations of stable isotopes ratios in tree rings are indicators of climate fluctuations. The current study examines the relationships between precipitation and temperature variations and stable oxygen isotopes ratios ( δ 18 O) of the last 50 years in cellulose extracted from growth rings of Juniperus polycarpus and Quercus macranthera in northern Iran. We sampled at high-elevation sites in the Alborz Mountains, where J. polycarpus covers south-facing slopes and Q. macranthera covers north-facing slopes, respectively. δ 18 O values of tree-ring cellulose in oak and juniper show site-specific differences in their mean and standard deviation, but temporal variations are significantly correlated, indicating a common forcing. Correlation functions of tree-ring δ 18 O with local and modelled climate data reveal positive effects of temperature on δ 18 O values in J. polycarpus during January–June, with significant correlations in January and May. Moreover, juniper δ 18 O is influenced by winter precipitation, probably due to an influence of snow melt on the isotopic composition of soil water during spring. Negative correlations were found between juniper δ 18 O and early vegetation period precipitation, when new xylem cells are formed. In contrast, δ 18 O of oak contains a late summer (September) precipitation signal. Besides, δ 18 O values in oak are positively affected by temperatures during summer and winter, with strongest connections with temperatures of September during the previous and current growing seasons. By combining stable isotope signals of species growing under different site conditions, there is a potential to reconstruct moisture variations during different seasons in the mountain areas of north Iran. [ABSTRACT FROM AUTHOR]

• Radial growth of Abies delavayi in southwest China is mainly limited by high temperatures and low moisture availability. • Tree growth rate of A. delavayi has been declining since the 1950s, accompanied with a remarkable increase of iWUE. • Xylem stable carbon (δ13C) and oxygen (δ18O) isotopic composition shifted to higher values from cold to warm years. • Growth declines of A. delavayi were driven by increasing drought stress and stomatal closure under a warming climate. Long-term tree growth trends and physiological responses to environmental changes, i.e., climate warming, and the rise of atmospheric [CO 2 ] (C a), need to be investigated across diverse forest ecosystems. We detected long-term trends in tree growth and δ13C derived intrinsic water use efficiency (iWUE) of Abies delavayi in the Cangshan Mountains, at its southern distribution edge in the Hengduan Mountains in southwestern China. We applied a dual-isotopic approach (δ13C, δ18O) to detect the shifts of tree physiological responses (photosynthetic, stomatal conductance) from colder to warmer conditions. Annual basal area increment (BAI) of A. delavayi in the Cangshan Mountains was decreasing since the 1950s, whilst the declining trend of tree growth was not obvious during the earlier period (1800–1951) after removing tree age- and size-related growth signals. Tree growth correlated negatively with temperatures and positively with relative humidity and self-calibrated Palmer drought severity index (scPDSI) during the early growing season (February to June), indicating a predominant growth limitation by moisture availability. Leaf inter-cellular [CO 2 ] (C i) derived from tree-ring δ13C of A. delavayi increased over time, with a rate slower than atmospheric C a rise, resulting in a decrease in the C i /C a ratio. Intrinsic water-use efficiency (iWUE) was increasing, especially after the 1950s. Dual-isotopic analyses revealed a reduction of stomatal conductance and stable or declined photosynthetic assimilation under warmer and drier environmental conditions. Recent growth decline of A. delavayi in the Cangshan Mountains was mainly related to the increase of warming-mediated drought stress and the resulting stomatal closure, while a positive effect of CO 2 fertilization was diminished under warming and drying environmental conditions. Our results serve as an early warning for tree growth and productivity of A. delavayi forests at the southern distribution limits under the ongoing warming climate. [ABSTRACT FROM AUTHOR]

Abstract: Podocarpus falcatus is an indigenous evergreen conifer species of tropical mountain forests in southeastern Ethiopia, showing potential tree ages of around 500 years. To study the influence of seasonal climate on the growth pattern of P. falcatus, we combined high-resolution electronic dendrometer measurements with wood anatomical investigations of microcores from the outermost stem parts collected in monthly intervals. At any time of the year sufficient rain events are able to cause cambial activity in P. falcatus. This permanent growing readiness leads to irregular wood formation with the formation of intra-annual density fluctuations and missing rings. Wood anatomical studies of microcores collected around the circumference of a mature P. falcatus revealed locally different activity status of the cambium on different lobes of the stem. Tree-ring width measurements of stem disks resulted in tentative tree ages that were confirmed by radiocarbon dating of selected wood samples. Although our efforts to cross-date ring-width series from several stem disks were not successful, further sampling in areas with different rainfall regimes, additional radiocarbon dating and measurements of stable isotopes hopefully would enable the establishment of a multi-century-long tree-ring series for climate reconstruction. [Copyright &y& Elsevier]

Abstract: High-resolution proxy data are still scarce in the southeastern Tibetan Plateau, which limit our understanding of climatic variability before instrumental records. In this study, we developed 595-year tree ring-width chronology from Larix speciosa near the timberlines of the Gaoligong Mountains, southeastern Tibetan Plateau. Ring-width site chronologies and a well-replicated regional chronology (RC) showed significant positive correlations with warm season temperatures from May to August. Using RC as predictor, we reconstructed mean May–August temperature for the study region that extends back to A.D. 1585. Cold conditions prevailed during the periods 1600s, 1620–30, 1640–50s, 1700s, 1730–40s, 1760s, 1810–20s, 1850s, 1900–10s and 1955–70. Warm episodes occurred during 1610s, 1660–1680s, 1710–20s, 1750s, 1780–90s, 1820–40, 1920–50 and 1980–present. Spatial correlations with gridded land surface temperatures revealed that our reconstruction represents regional temperature signal for the southern Tibetan Plateau. Comparison with other tree ring-based temperature reconstructions from surrounding areas implies a high degree of confidence for our reconstruction. [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]

The article discusses a tree ring-based drought reconstruction in the central Hengduan Mountains in north-western Yunnan, China. The study involved developing four tree ring-width chronologies of three species. It was found that there are correlations existing among the chronologies, and that the first principal component makes up 60.5% of total variance in 1655-2005. Also, radial growth was observed to be affected by precipitation and relative humidity and Palmer drought severity index (PDSI), whereas tree growth is negatively affected by temperature in March.

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]

• Summer temperature is the most important climatic factor to determine radial growth of Himalayan fir. • Himalayan fir showed an elevational trend in tree radial growth response. • Tree growth is increasingly limited by spring moisture availability at low-to-middle elevations with ongoing climate change. • No obvious temporal shift has been observed in temperature sensitivity of Himalayan fir. A better understanding of growth-climate responses of high-elevation tree species across their distribution range is essential to devise an appropriate forest management and conservation strategies against adverse impacts of climate change. The present study evaluates how radial growth of Himalayan fir (Abies spectabilis D. Don) and its relation to climate varies with elevation in the Manaslu Mountain range in the central Himalaya. We developed tree-ring width chronologies of Himalayan fir from three elevational belts at the species'upper distribution limit (3750−3900 m), in the middle range (3500−3600 m), and at the lower distribution limit (3200−3300 m), and analyzed their associations with climatic factors. Tree growth of Himalayan fir varied synchronously across elevational belts, with recent growth increases observed at all elevations. Across the elevation gradient, radial growth correlated positively (negatively) with temperature (precipitation and standardized precipitation-evapotranspiration index, SPEI-03) during the summer (July to September) season. However, the importance of summer (July to September) temperatures on radial growth decreased with elevation, whereas correlations with winter (previous November to current January) temperatures increased. Correlations with spring precipitation and SPEI-03 changed from positive to negative from low to high elevations. Moving correlation analysis revealed a persistent response of tree growth to May and August temperatures. However, growth response to spring moisture availability has strongly increased in recent decades, indicating that intensified spring drought may reduce growth rates of Himalayan fir at lower elevations. Under sufficient moisture conditions, increasing summer temperature might be beneficial for fir trees growing at all elevations, while trees growing at the upper treeline will take additional benefit from winter warming. [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]

• Tree growth in the Karnali river catchment was sensitive to moisture availability. • March–July streamflow was reconstructed for Karnali River Basin since 1628 CE. • An increasing frequency of extreme events was found during the recent decades. • Streamflow variability of the Karnali river is mainly linked with ENSO and PDO. The Karnali River is one of the major transboundary rivers of the Nepalese central Himalaya and a major tributary of the Ganges River. In order to investigate regional historical hydroclimate variability, we compiled eleven tree ring-width chronologies based on 354 exactly dated tree cores from five coniferous species for the Karnali River catchment. The chronologies were moisture-sensitive and the composite chronology was significantly correlated with spring-to-early summer (March–July) (R = 0.67, P < 0.001) discharge at the Chisapani gauging station. The robust calibration (R2 = 0.45, 1962–2010) enabled us to reconstruct March–July streamflow variability of Karnali River Basin (KRB) over the past four centuries. The streamflow reconstruction showed prolonged pluvial periods during 1650–1661, 1711–1718, 1723–1731, 1824–1831, 1877–1889, 1924–1931, and 1971–1981, while prolonged low-flow periods occurred during 1639–1649, 1689–1710, 1753–1769, 1777–1784, 1803–1823, 1867–1876, 1942–1959, and 1963–1970. Our reconstructed March–July streamflow series correlated positively with the seasonally averaged drought index and precipitation in the central-west Himalayan region and vicinities. The streamflow reconstruction revealed an increasing frequency of extreme low-flow and pluvial events in the central-west Himalayan region, especially during the past century. We found short (2.1–3.3, 6.2–6.3, and 8.5–8.7 years) to medium (12.2–12.5 years) periodicities in the reconstructed streamflow series, implying teleconnections with broad-scale climate modes like the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Our Karnali River streamflow reconstruction represents an update of regional hydroclimate variability, which may serve as a useful reference for water resource management and appropriate water-use policies in the context of current and future climate change. [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]

High-resolution palaeoclimate proxy records have been lacking for the subtropical region of southwest China. To gain insights into hydroclimate variability in central Yunnan Province, we constructed a tree ring-width chronology of Tsuga dumosa from the Wuliang Mountain area. Correlation analysis shows that moisture availability is predominantly the limiting factor on radial growth, particularly during the spring-early summer season. Using a well-calibrated regression model (R2 = 0.36, p < 0.001), we reconstructed the March–June Standardized Precipitation-Evapotranspiration Index (SPEI) for the period from 1826 to 2020 CE. Eleven extreme drought years (1860, 1897, 1958, 1960, 1979, 1984, 1987, 2006, 2010, 2013, and 2019) were identified, with most of them confirmed by historical evidence. The reconstruction series shows inter-annual to inter-decadal variations and an increasing occurrence of severe dry or wet events in the recent past, particularly during the last 50 years. Our drought reconstruction series shows high frequency cycle of 2–8 years. Spatial correlations indicate that our drought reconstruction captures hydrological signals over a larger area. In line with this, the reconstructed dry periods exhibit broad consistency with other tree-ring based drought reconstructions conducted in nearby regions. Our findings demonstrate the potential of tree-ring proxies for hydroclimate reconstruction in the subtropical areas of southwest China and provide crucial information for evaluating long-term climate change in this region. • Radial growth of T. dumosa in central Yunnan is mainly limited by spring-early summer moisture availability. • The two-century SPEI reconstruction identified eleven extreme drought years that align with historical records. • There has been a notable increase in the occurrence of severe dry or wet events in recent decades. [ABSTRACT FROM AUTHOR]

Advances and retreats of glaciers on the Tibetan Plateau (TP) are widely regarded as indicators for climate changes sensitive to macroclimatic forcing mechanisms like the Asian summer monsoon. However, it often remains unclear why some glaciers retreat or advance earlier than others, particularly regarding the timing of the so-called ‘Little Ice Age (LIA) maximum’. Within this study, we present newly acquired tree-ring data from four glacier forefields in the Nyainqêntanglha Range on the southeastern TP and link them to previous studies. Two of the glaciers formed a double-tongue moraine set during the LIA, with trees providing minimum ages for two different major glacier extents. In combination with evidence from a third glacier, three warm phases within the generally cold LIA can be deduced during the first half of the 16th century, and the mid-17th and 18th centuries. This implies the occurrence of three preceding major cold spells. A minor cool phase between 1790 and 1850 marks the end of the LIA on the southeast TP. Minimum ages for beginning retreat from the last major LIA glacial advance differ by only 40 years for all sampled monsoonal temperate valley glaciers in the Nyainqêntanglha Range. This implies a common forcing, whose impact on glacier dynamics is only slightly altered by topographical factors or local climatic conditions. Regression analysis suggests that the delay of the glacier retreat from the maximum extent is mainly related to glacier size, with minor influence of ablation area aspect. All moraine ages highlight intermediate LIA warm phases on the southeast TP corresponding to warm phases on the northern Hemisphere and thus prove monsoonal temperate glaciers to be highly sensitive archives for northern hemispheric climatic conditions. [ABSTRACT FROM AUTHOR]

• Pine radial growth across Southwest China was limited by moisture availability • Moisture sensitivity of P. kesiya species decreased from dry to humid sites • Temperature sensitivity of P. yunnanensis decreased from cold to warm sites • Climate sensitivity of two pine species varies with site environmental conditions A better understanding of tree growth-climate sensitivity across regions and species may reduce uncertainties in simulating forest carbon budgets. We studied the spatial heterogeneity of growth-climate sensitivity of Pinus yunnanensis and Pinus kesiya across temperature and moisture gradients in the complex mountain regions of Southwest China. We developed tree ring-width chronologies from 22 sites for P. yunnanensis and 20 sites for P. kesiya , totaling 903 trees (1684 cores). We applied generalized additive mixed models (GAMMs) on basal area increment (BAI) series to remove the age and size effects on tree growth, and correlated BAI residual chronologies with climate variables. Radial growth of P. yunnanensis and P. kesiya at most sites (> 75%) were positively correlated with precipitation and one-month Standardized Precipitation-Evapotranspiration Index (SPEI1) during the early growing season. In contrast, high precipitation and SPEI1 during the late growing season reduced tree growth of both pine species. The growth-climate sensitivity of both pine species varied along the temperature and moisture gradients, i.e., moisture sensitivity of tree growth decreased along a dry-to-humid moisture gradients for P. kesiya during early growing season, whereas temperature sensitivity of P. yunnanensis shifted from positive (beneficial) to negative (limitative) along cold-to-warm gradients. Our results indicate that the growth-climate sensitivity of both pine species varies with site-specific environmental conditions. These findings contribute to improve our understanding about the spatial patterns of tree growth-climate responses of these economically important conifer species in Southwest China. [ABSTRACT FROM AUTHOR]

We present the first annually resolved and statistically reliable tree-ring δ18O (δ18O T) chronologies for the three South Asian tropical moist forest tree species (Chukrasia tabularis A. Juss., Toona ciliata M. Roem., and Lagerstroemia speciosa Roxb.) which differ in their shade tolerance and resistance to water stress. We found significantly higher mean δ18O T values in light-demanding T. ciliata than in intermediate shade tolerant C. tabularis and shade tolerant L. speciosa (p < 0.001). δ18O T in C. tabularis was mainly influenced by pre-monsoon vapor pressure deficit (VPD; r = −0.54, p < 0.01) and post monsoon maximum temperature (T max) (r = 0.52, p < 0.01). δ18O T in T. ciliata was strongly negatively correlated with a dry season drought index PDSI (r = −0.65, p < 0.001) and VPD (r = −0.58, p < 0.001). Pre-monsoon T max was strongly positively linked with δ18O T in L. speciosa (r = 0.65, p < 0.001), indicating that climatic influences on δ18O T are species-specific and vary among tree functional types. Although there was a week correlation between local precipitation and δ18O T in our studied species, we found a strong correlation between δ18O T and precipitation at a larger spatial scale. Linear mixed effect models revealed that multiple factors improved model performance only in C. tabularis , yielding the best model, which combined VPD and T max. The top models in T. ciliata and L. speciosa included only the single factors PDSI and T max , highlighting that the way C. tabularis interacts with climate is more complex when compared with other two species. Our analyses suggest that stable oxygen isotope composition in tree rings of South Asian tropical moist forest trees are a suitable proxy of local and regional climate variability and are an important tool for understanding the physiological mechanisms associated with the global hydrological cycle. Unlabelled Image • Tree-ring δ18O chronologies are developed for three species varying among tree functional types. • The main forcing factor driving inter-annual δ18O T variability is related to variations in hydroclimate. • δ18O T captured local and regional climate variability. • The mean δ18O T values may vary among the studied tree species. • δ18O T help understand how different tree functional types respond to changes in the hydrological cycle. [ABSTRACT FROM AUTHOR]