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.

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.

A 1 835 a tree-ring chronology and its preliminary analyses in Dulan region, Qinghai

TREE-ring analysis is one of the important ways for paleoclimatic reconstruction because tree-ring series of several hundred or even thousands of years are available, and can be matched orextended and accurately dated, and the tree rings can record changes in climate. In China,several thousand paleoclimatic series of data are obtained from the historical documents,

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.

Exploratory Precipitation in North-Central China during the Past Four Centuries

Two robust precipitation reconstructions were conducted by combining tree-ring chronologies, dryness/wetness indices from historical documents, and climate data from the global grid. It was found that the recurrent drought history of a region can help us understand the variability of precipitation. Several dry/wet periods during the past four centuries and potential cycles of precipitation variation were determined. Furthermore, the reconstructions are not only consistent well with each other in North-central China, but also in good agreement with variations of precipitation in northeastern Mongolia, the Longxi area in Gangsu Province and the Dulan area of Qinghai Province, and the snow accumulation of the Guliya glacier. These synchronous variations indicate that it is valuable to study various climate records, find common information and determine the driving force of climate change.

RADIAL GROWTH OF HUASHAN PINE AND ITS RESPONSE TO CLIMATE

Huashan pine (Finus armandii Franch) is a poential species for dendroclimatic study. Ring-width cores were sampled for four stands of two sites from the eastern extreme of the Qinling Mountains. The ring-width chronologies developed in this study cover a maximum Period from A.D. 1359 t0 1992 and show high common chronology variance over the common period 1911-1960.All the chronologies are significantly correlated with all others, and the degree of correlation appears related to tree age. Response function analyses reveal that from 41 to 75 Percent of chronology variance can be accounted for by monthly mean air temperature and monthly total precipitation. A sufficiently strong correlation of ringwidth index with May and June rainfall and June temperature exists, implying soil moisture to be a limiting factor for Huashan pine growth. The association displayed by response diagrams between narrow rings, low precipitation, and high temperature during spring and early summer indicates a promising potential of ring widths for reconstruction of spring drought for the study area.

Infl uence of altitude and tree class on climate-growth relationships in a larch plantation in subtropical China

Precise quantifi cation of climate-growth relationships can make a major contribution to scientifi c forest management.However,whether diff erences in the response of growth to climate at diff erent altitudes remains unclear.To answer this,264 trees of Larix kaempferi from 88 plots,representing diff erent altitudinal ranges(1000-2100 m)and tree classes were sampled and used to develop tree-ring chronologies.Tree-ring growth(TRG)was either positively(dominant)or negatively(intermediate and suppressed)correlated with climate in diff erent tree classes at diff erent altitudes.TRG was strongly correlated with growing season at low altitudes,but was less sensitive to climate at middle altitudes.It was mainly limited by precipitation and was highly sensitive to climate at low altitudes.Climate-growth relationships at high altitudes were opposite compared to those at low altitudes.TRG of dominant trees was more sensitive to climate change compared to intermediate and suppressed trees.Climate factors(annual temperatures;moisture,the number of frost-free days)had diff erent eff ects on tree-ring growth of diff erent tree classes along altitudinal gradients.It was concluded that the increase in summer temperatures decreased water availability,resulting in a signifi cant decline in growth rates after 2005 at lower altitudes.L.kaempferi is suitable for planting in middle altitudes and dominant trees were the best sampling choice for accurately assessing climate-growth relationships.