Method to measure tree-ring width,density,elemental composition,and stable carbon and oxygen isotopes using one sample

Tree-ring width(RW),density,elemental com-position,and stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)are widely used as proxies to assess climate change,ecology,and environmental pollution;however,a specific pretreat-ment has been needed for each proxy.Here,we developed a method by which each proxy can be measured in the same sample.First,the sample is polished for ring width meas-urement.After obtaining the ring width data,the sample is cut to form a 1-mm-thick wood plate.The sample is then mounted in a vertical sample holder,and gradually scanned by an X-ray beam.Simultaneously,the count rates of the fluorescent photons of elements(for chemical characteriza-tion)and a radiographic grayscale image(for wood density)are obtained,i.e.the density and the element content are obtained.Then,cellulose is isolated from the 1-mm wood plate by removal of lignin,and hemicellulose.After producing this cellulose plate,cellulose subsamples are separated by knife under the microscope for inter-annual and intra-annual stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)analysis.Based on this method,RW,density,elemental composition,δ^(13)C,and δ^(18)O can be measured from the same sample,which reduces sample amount and treatment time,and is helpful for multi-proxy comparison and combination research.

Enhancing forest insect outbreak detection by integrating tree-ring and climate variables

Annual tree rings are widely recognized as valuable tools for quantifying and reconstructing historical forest disturbances.However,the influence of climate can complicate the detection of disturbance signals,leading to limited accuracy in existing methods.In this study,we propose a random under-sampling boosting(RUB)classifier that integrates both tree-ring and climate variables to enhance the detection of forest insect outbreaks.The study focused on 32 sites in Alberta,Canada,which documented insect outbreaks from 1939 to 2010.Through thorough feature engineering,model development,and tenfold cross-validation,multiple machine learning(ML)models were constructed.These models used ring width indices(RWIs)and climate variables within an 11-year window as input features,with outbreak and non-outbreak occurrences as the corresponding output variables.Our results reveal that the RUB model consistently demonstrated superior overall performance and stability,with an accuracy of 88.1%,which surpassed that of the other ML models.In addition,the relative importance of the feature variables followed the order RWIs>mean maximum temperature(Tmax)from May to July>mean total precipita-tion(Pmean)in July>mean minimum temperature(Tmin)in October.More importantly,the dfoliatR(an R package for detecting insect defoliation)and curve intervention detec-tion methods were inferior to the RUB model.Our findings underscore that integrating tree-ring width and climate vari-ables as predictors in machine learning offers a promising avenue for enhancing the accuracy of detecting forest insect outbreaks.

Silver fir tree-ring fluctuations decrease from north to south latitude—total solar irradiance and NAO are indicated as the main influencing factors

Silver fir(Abies alba Mill.)is a flexible European tree species,mainly vegetating within the mountainous regions of Europe,but its growth responses across its latitudinal and longitudinal range have not yet been satisfactorily verified under changing environmental conditions.This study describes the tree-ring increment of silver fir in research plots across a latitudinal gradient from the northern range in Czechia(CZ),through Croatia(HR)to the southernmost range in Italy(IT).The research aims to analyze in detail the dynamics and cyclicity of the ringwidth index(RWI)and how it relates to climatic factors(temperature and precipitation),the North Atlantic Oscillation(NAO),and total solar irradiance(TSI),including the determination of latitude.The results show that the main drivers affecting fir growth are the seasonal NAO index and TSI.Monthly temperatures affect RWI early in the vegetation season,while lack of precipitation during the summer is a limiting factor for fir growth,especially in July.Seasonal temperatures and temperatures in June and July negatively impact,while seasonal precipitation totals in the same months positively influence the RWI in all research plots across meridian.The longest growth cycles in fir RWI were recorded in the northernmost studied plots in CZ.These cyclical fluctuations recede approaching the south.The cyclic increase in RWI is related to the TSI,which decreases its effect from north to south.The TSI's effects vary,positively impacting CZ but negatively influencing HR while remaining relatively neutral in IT.On the other hand,seasonal NAO tends to negatively affect silver fir growth in HR and CZ but has a mildly positive effect in IT.In conclusion,the TSI and the influence of the seasonal NAO index are prevalent in the fir RWI and are accompanied by a greater cyclicity of RWI in Central Europe(temperature optimum)than in the Italian Mediterranean region,where this tree species is limited by climatic conditions,especially lack of precipitation.

Reconstruction of hydrological changes based on tree-ring data of the Haba River, northwestern China

Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living coniferous forests on the Altay Mountains provide a good example for carrying out the dendrohydrological studies. In this study, a regional composite tree-ring width chronology developed by Lariat sibirica Ledeb. and Picea obovata Ledeb. was used to reconstruct a 301-year annual （from preceding July to succeeding June） streamflow for the Haba River, which originates in the southern Altay Mountains, Xinjiang, China. Results indicated that the reconstructed streamflow series and the observations were fitting well, and explained 47.5% of the variation in the observed streamflow of 1957-2008. Moreover, floods and droughts in 1949-2000 were precisely captured by the streamflow reconstruction. Based on the frequencies of the wettest/driest years and decades, we identified the 19th century as the century with the largest occurrence of hydrological fluctuations for the last 300 years. After applying a 21-year moving average, we found five wet （1724-1758, 1780-1810, 1822-1853, 1931-1967, and 1986-2004） and four dry （1759-1779, 1811-1821, 1854-1930, and 1968-1985） periods in the streamflow reconstruction. Furthermore, four periods （1770-1796, 1816-1836, 1884-1949, and 1973-1997） identified by the streamflow series had an obvious increasing trend. The increasing trend of streamflow since the 1970s was the biggest in the last 300 years and coincided with the recent warming-wetting trend in northwestern China. A significant correlation between streamflow and precipitation in the Altay Mountains indicated that the streamflow reconstruction contained not only local, but also broad-scale, hydro-climatic signals. The 24-year, 12-year, and 2.2-4.5-year cycles of the reconstruction revealed that the streamflow variability of the Haba River may be influenced by solar activity and the atmosphere-ocean system.

January to August temperature variability since 1776 inferred from tree-ring width of Pinus tabulaeformis in Helan Mountain

Tree-ring standardized chronologies are developed by 78 cores collected from the eastern and western Helan Mountain. Statistical analysis shows that both the STD and RES chronologies correlate negatively with the temperature of different periods of early half year, especially with January to August mean （JA） temperature, which means that JA temperature is one of the predominant limiting factors of tree growth in the Helan Mountain. Based on this analysis, we reconstructed JA temperature, and the explained variance is 43.3% （F=21.422, p〈0.001 ）. The comparatively high temperature periods in the reconstruction were： 1805-1818 1828-1857, 1899-1907, 1919-1931 and 1968-1995; and the comparatively low temperatu re periods happened in 1858-1872, 1883-1895 and 1935-1953. Ten-year moving average curve shows three slow uplifting trends： 1766-1853, 1862-1931 and 1944-1995. Each temperature increase was followed by a sudden temperature decrease about 10 years, that is to say, the JA temperature in the Helan Mountain is characterized by slow increase and sudden decrease. The 70- and 10.77-year periodicities detected in the temperature series correspond to the Gleissberg （80-year） and Schwabe （11-year） periodicities of solar activity respectively, the 2.11-2.62 years cycles are considered to be influenced by QBO （Quasi-Biennial-Oscillation） and the local environmental change.

Tree-ring response of Larix chinensis on regional climate and sea-surface temperature variations in alpine timberline in the Qinling Mountains

Tree-ring width chronologies of Larix chinensis were developed from the northern and southern slopes of the Qinling Mountains in Shaanxi Province,and climatic factors affecting the tree-ring widths of L.chinensis were examined.Correlation analysis showed that similar correlations between tree-ring width chronologies and climatic factors demonstrated that radial growth responded to climate change on both slopes.The radial growth of L.chinensis was mainly limited by temperature,especially the growing season.In contrast,both chronologies were negatively correlated with precipitation in May of the previous year and April of the current year.Spatial climate-correlation analyses with gridded land-surface climate data revealed that our tree-ring width chronologies contained a strong regional temperature signal over much of northcentral and eastern China.Spatial correlation with seasurface temperature fields highlights the influence of the Pacific Ocean,Indian Ocean,and North Atlantic Ocean.Wavelet coherence analysis indicated the existence of some decadal and interannual cycles in the two tree-ring width chronologies.This may suggest the influences of El Nin˜o-Southern Oscillation and solar activity on tree growth in the Qinling Mountains.These findings will help us understand the growth response of L.chinensis to climate change in the Qinling region,and they provide critical information for future climate reconstructions based on this species in semi-humid regions.

Tree-ring-based reconstruction of temperature variability(1445–2011) for the upper reaches of the Heihe River Basin, Northwest China

Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-line of the middle Qilian Mountains within the upper reaches of Heihe River Basin, Northwest China for a long-term reconstruction of temperature at the study site. In this paper, tree-ring chronology was used to examine climate-growth associations considering local climate data obtained from Qilian Meteorological Station. The results showed that temperatures correlated extremely well with standardized growth indices of trees (r=0.564, P<0.001). Tree-ring chronology was highest correlated with annual mean temperature (r=0.641, P<0.0001). Annual mean temperature which spans the period of 1445–2011 was reconstructed and explained 57.8% of the inter-annual to decadal temperature variance at the regional scale for the period 1961–2011. Spatial correlation patterns revealed that reconstructed temperature data and gridded temperature data had a significant correlation on a regional scale, indicating that the reconstruction represents climatic variations for an extended area surrounding the sampling sites. Analysis of the temperature reconstruction indicated that major cold periods occurred during the periods of 1450s–1480s, 1590s–1770s, 1810s–1890s, 1920s–1940s, and 1960s–1970s. Warm intervals occurred during 1490s–1580s, 1780s–1800s, 1900s–1910s, 1950s, and 1980s to present. The coldest 100-year and decadal periods occurred from 1490s–1580s and 1780s–1800s, respectively, while the warmest 100 years within the studied time period was the 20th century. Colder events and intervals coincided with wet or moist conditions in and near the study region. The reconstructed temperature agreed well with other temperature series reconstructed across the surrounding areas, demonstrating that this reconstructed temperature could be used to evaluate regional climate change. Compared to the tree-ring reconstructed temperature from nearby regions and records of glacier fluctuations from the surrounding high mountains, this reconstruction was reliable, and could aid in the evaluation of regional climate variability. Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Ni?o–Southern Oscillation (ENSO).

Reconstructing the annual precipitation variation since 1899 based on tree-ring width in the western Hedong sandy land of Ningxia

Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation and the tree-ring width since 1899 was reconstructed. The results of cross verification indicated that the conversion equation is stable and the reconstructed results are reliable. The result of reconstructed annual precipitation showed the remarkable fluctuation of precipitation and dry-to-wet variation before the 1940s. The smaller fluctuation and high frequent changes of precipitation occurred during the period of 1940s-1980s and after the 1980s the change trend of the precipitation became high periodic extent and low frequent. The study found that there were some coincidences with the climate change in Changling Mountains, Helan Mountains and the east of Qilian Mountains. The relatively dry periods in the beginning of 20th century, 1920s to 1930s, the end of the 20th century and 2004 to 2006 in the western Hedong sandy land of Ningxia accelerated the desertification, while the relatively humid period during the periods of the 1910s-1920s, 1930s-1940s and 1990s is favorable to prevent and control the desertification, and to weaken the climate warming and drying. The periods of annual precipitation variation in the western Hedong sandy land of Ningxia since 1899 are approximately 2-4 years, 5-7 years and 10 years.

Establishment of tree-ring chronology and climatic response of Tibetan juniper(S.tibetica) in south Tibet,western China

A tree-ring width chronology of 442 years(1567-2008) was developed from Tibetan junipers(S.tibetica) derived from south Tibet in western China.Three versions of chronology were produced according to standard dendrochronological techniques.The correlation and response analysis displays a high correlation between the standard tree ring-width chronology and observed annual mean precipitation series during the period 1961-2008.Based on a linear regression model,an annual(prior August to current July) precipitation for the past 229 years was reconstructed.This is the first well-calibrated precipitation reconstruction for the Nanggarze region,south Tibet.The results show that relatively wet years with above-average precipitation occurred in 1780-1807,1854-1866,1886-1898,1904-1949,1967-1981 and 2000-2008,whereas relatively dry years with below-average precipitation prevailed during 1808-1853,1867-1885,1899-1903,1950-1966 and 1982-1999.Common dry/wet periods during 1890s,1910s,1940s-1960s and 1980s were also identified from other moisture reconstructions of nearby regions,indicating a synchronous climatic variation in south Tibet.Abrupt change beginning in 1888 was detected,revealing a transition from wet to dry conditions in south Tibet.Power spectrum analysis reveals significant cycles of 28-year,5.5-5.6-year and 3.3-year during the past 200 years.

Response of tree-ring growth to climate at treeline ecotones in the Qilian Mountains,northwestern China

Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data, the influence of precipitation, mean temperature and mean minimum temperature at yearly, seasonal and monthly scales on the tree-ring growth of Picea crossifolia was studied at treeline ecotones in the Qilian Mountains, northwestern China. The results show that growing season temperatures of previous and current years are important limiting factors on tree-ring growth, particularly June mean temperature and mean minimum temperature of current year. The precipitations in the previous winter and current spring have a positive correlation, and in the current fall has a negative correlation with tree-ring growth, but these correlations are not significant. Our results suggest that temperature controls tree-ring growth more strongly than precipitation at treeline ecotones in the Qilian Mountains.

Dynamics of moisture regime and its reconstruction from a tree-ring width chronology of Pinus sylvestris in the downstream basin of the Selenga River, Russia

Regional tree-ring width chronology of the Scots pine (Pinus sylvestris L.) was constructed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga River basin, Russia. Moisture information contained in tree-ring width chronology was obtained through linear regression reconstruction models of annual August–July precipitation and annual water discharge of the Selenga River during the period 1767–2015. Comparison of the smoothed series allowed estimating long-term variation component of these moisture regime parameters with a high precision. At the same time, regional drought indices are less correlated with pine radial growth, because they have contribution of the other environmental variables, which are much less reflected in the tree-ring of the investigated pine forest stands. Reconstructed dynamic of the moisture regime parameters is supported by documental evident of many socially significant events in the regional history, such as crop failures caused by both droughts and floods, and catastrophic fire in the Irkutsk City in 1879. Also, dependence of the amount of precipitation in the study area on the atmospheric circulation in Central Asia is revealed to have a similar pattern with other regions, i.e., a negative relationship of precipitation with the development of large high atmospheric pressure area within its center in the Altai and Tianshan mountains.

Tree-ring:a suitable implement for spatial and temporal fire distribution analysis in savanna woodland and dry forest

Based on 120 stem discs collected during3 months of fieldwork along a 12 km route,the history of fires in the Wari Maro Forest（09 1000 N–02 1000E） over the past century in savanna woodland and dry forest was reconstituted.Three major ecological areas are characterized：one highly burnt zone located between two relative less burnt areas.By analyzing tree rings,246 fire scars were identified.The scars were caused by 51 fire years,occurring at a mean interval of 2.23 years.From 1890 to1965,only 6 years with fires were recorded from sampled trees.Since 1966,no year has passed without fire.The fire frequency point scale reached 14 years.This was the case of Burkea africana,which has been identified as a species tolerant to fire and could be planted to create a natural firewall.In contrast,Anogeissus leiocarpa is highly sensitive to fire,and in a dry forest ecosystem that burns seasonally,it requires a special conservation plan.Two new concepts are described：the rebarking of trees after fire and Mean Kilometer Fire Interval.The first concept was tested with Daniellia oliveri（Rolfe） Hutch ＆ Dalz trees,and the second concept was used to evaluate spatial fire distribution.We demonstrate that savanna woodland and dry forest were subject to a degradation process caused by destructive fires related to vegetation cover clearance and illegal logging.

Climatic response of Pinus sylvestris var. mongolica tree-ring width and precipitation reconstruction for the northern Greater Higgnan Mountains, China, since 1720

August-June precipitation has been reconstructed back to AD 1720 for the northern Greater Higgnan Mountains, China, by use ofPinus sylvestris var. mongolica tree-ring width. The reconstruction explains the variance of 39% in observed precipitation from 1973 to 2008. Some extremely dry/wet signals in historical documents and other precipitation reconstructions in previous studies are precisely captured in our reconstruction. Wet periods occurred during the periods of 1730 to 1746, 1789 to 1812, 1844 to 1903, 1920 to 1930, 1942 to 1961, and 1985 to 1998; while periods of 1747 to 1788, 1813 to 1843, 1904 to 1919, 1931 to 1941, and 1962 to 1984 were relatively dry. Power spectral and wavelet analyses demon- strated the existence of significant 24-year, 12-year, and 2-year cycles of variability.

Assessment of tree-ring mercury radial translocation and age effect in Masson pine:Implications for historical atmospheric mercury reconstruction

The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury(Hg)trends,but with the large knowledge gaps in the reliability.In this study,we comprehensively evaluated the Hg source,radial translocation and age effect of Masson pine(Pinus massoniana)tree ring at Mt.Jinyun in Chongqing,to assess the suitability of such tree ring as the archive of atmospheric Hg.Results showed that distinct variabilities among Masson pine tree-ring Hg concentration profiles.The Hg concentration significantly increased along with stem height(P<0.05),indicating the Hg in tree rings mainly derived from foliage uptake atmospheric Hg.We found a distinct age effect that the tree ring of young trees had the higher Hg concentration.Besides,we used the advection-diffusion model to demonstrate how Hg concentration shifted by the advection or/and diffusion in tree rings.The modeling results showed that the advection induced radial translocation during the young growth period of tree was a plausible mechanism to result in the tree-ring Hg record largely different from the trend of anthropogenic Hg emissions in Chongqing.We finally suggest that in further Hg dendrochemistry,better discarding the tree-ring Hg profile of the young growth period to reduce impacts of the radial translocation and age effect.

The summer standardized precipitation evapotranspiration index(SPEl)dataset for six European regions over the past millennium reconstructed by tree-ring chronologies

Accurate reconstructed series are crucial for studying the differences in regional hydroclimatic variations in Europe over the past millennium.Using hierarchical clustering analysis and stepwise regression methods,we reconstructed yearly time series of the summer standardized precipitation evapotranspiration index(SPEl)for six European regions over the past millennium.Our analysis also revealed prominent regional hydroclimatic differences in multidecadal signals over the past 500 years.For instance,in the 1500s-1570s(from the beginning of the 1500s to the end of the 1570s),drying trends were observed in northern and southeastern Europe,whereas southwestern Europe experienced a wetting trend.Moreover,drying trends were observed in northern and central Europe in the 1640s-1670s.Additionally,wetting trends were observed in western and central Europe during the 1830s-1850s,with drying trends in northern and southeastern Europe.Notably,the hydroclimatic variations in most European regions showed drying trends in the 1920s-1950s,especially in southern Europe.By utilizing large amounts of tree-ring samples and directly comparing regional hydroclimatic variations,our reconstructions provide a consistent and comprehensive dataset for further analysis.The reconstructed dataset is available at https://doi.org/10.57760/sciencedb.07215.

Climate Response Analysis of Pinus massoniana Tree-Ring Chronology in Shuangpai County,China

The formation of tree-rings is closely related to climate variation. This paper establishes the tree-ring chronology of Pinus massoniana for a period of 36 years and examines the relationship between the tree-ring chronology and climatic conditions based on tree-ring width samples from three sites on the northeast slopes of Yangming Mountain. This data is used to study the relationship between the tree-ring width of a young tree and climatic conditions in a moist hilly region of southern China and to understand the general pattern of climate variation and its effects on tree growth in the past in this region. The results indicate that changes in tree-ring widths in these sites are closely related to local climatic conditions. There is a significant positive correlation between the radial growth of Pinus massoniana and the mean temperature of the current year from January to May（coefficient of correlation, R, is 0.596, P〈0.01） and the mean temperature of the previous year from June to July（R is 0.639, P〈0.01）. The radial growth of Pinus massoniana is negatively correlated with the total precipitation of the previous year from January to March and November to December（R is-0.46, P〈0.05） and negatively correlated with the total precipitation of the previous year from June to July（R is-0.582, P〈0.05）. The effect of precipitation on the radial growth of Pinus massoniana is known as the ＂hysteresis effect＂.

Temperature variations recovered from tree-rings in the middle Qilian Mountain over the last millennium

Based on the cross-dated tree-ring samples collected from the middle Qilian Moun- tain, a standard ring-width chronology had been developed, which covered the period AD 1000 to 2000. The correlations between the chronology and climatic records from the nearby meteorological stations indicated that temperature was the dominant climatic factor for tree growth at upper timberline, and the most important climatic factor for the tree growth in the area was the mean temperature from previous December to current April. The temperature variations recovered from the ring-width data showed a cold period during the “Little Ice Age” and the con- tinuous warming during the twentieth century. Comparison between the ring-width chronology and δ18O records from the Dunde ice core in the Qilian Mountain indicated that there was a con- sistent trend in both time series. A significant correlation existed between our ring-width chro- nology and the Northern Hemispheric temperature, suggesting that the climate changes in the Qilian Mountain were not only driven by regional factors, but also responsive to the global cli- mate.

Reconstruction of summer temperature (June-August) at Mt.Helan,China,from tree-ring stable carbon isotope values since AD 1890

From stable carbon isotope analysis of tree-rings of Chinese pine (Pinus tabulaeformis) from Mt. Helan, China, we found that high-δ13C values were related to high mean temperatures from June to August (T 68), and Iow-δ13C values corresponded to low T 68. From these data, a transfer function has been used to reconstruct summer temperatures (T 68) for the Mt. Helan region. The explained variance of reconstruction is 34.9% (F=15.01, p<0.001). The time period containing the highest summer temperatures in northern China (late 1920-1930s) was confirmed by our reconstruction. The data indicate that there is a tele-connection between summer temperatures in Mt. Helan area and sea-surface-temperatures in the tropical Pacific. The extreme low temperature periods around the years of 1920 and 1947 for Mt. Helan region correspond well to the cold climate in the tropical Pacific. Along with other analyses, this suggests that climate variations in the Mt. Helan region are driven not only by local events, but also by the global climate. Significant periodicities appearing in the reconstruction are 2.56 and 2.63 years.

Tree-ring-based reconstruction of the April to September mean temperature since 1826 AD for north-central Shaanxi Province,China

Long-time series of high-resolution temperature record from Chinese Loess Plateau is rare. An April-September mean temperature reconstruction (1826-2004) has been developed for the north-central Shaanxi Province, China, based on tree-ring width analysis. The reconstruction captures 39.3% (p<0.001) of the variance in the instrumental data over the calibration period from 1951 to 2002. The reconstruction shows a high temperature period of 1928-1933, which coincides with the timing of the extreme drought event in 1920s in the entire northern China. The two low temperature periods in reconstruction are 1883-1888 and 1938-1942. With the global warming, the April-September mean temperature in study area has also increased since the 1970s, but has not exceeded the temperature in 1928-1933. Besides the statistical analysis, the reconstruction is also verified by the local dryness/wetness index and other dendroclimatological results.

Growth characteristics and response to climate change of Larix Miller tree-ring in China

As one of the earliest species used in dendrochronological studies, Larix responds sensitively to climate change. In this study, nine larch species and one variety from eleven sites were collected to study the growth characteristics of tree-ring width using dendrochronological methods. Ten residual tree-ring chronologies were developed to analyze their relationships with regional standardized anomaly series by Pearson’s correlation analysis. The results suggest that most of the chronologies had significantly positive correlations with the mean temperature and mean maximum temperature in May. The spring temperature evidently limited the radial growth of the larch species without precipitation control. The largest mean tree-ring width was found in Himalayan Larch in Jilong, whereas Master Larch in Si’er reflected the smallest mean value. Both species presented little climate information in this study. Chinese, Potanin, and Tibetan larches are significantly correlated with climate change, implying a huge potential for climate history reconstruction. The elevation of the sampling sites appears to be an important condition for tree-ring growth of larches responding to climate factors.