Climatic response of three tree species growing at different elevations in the Luliang Mountains of Northern China

In this study, we present the results of a dendroclimatological investigation of three coniferous tree species, Larix principis-rupprechtii, Picea meyeri and Pinus tabulaeformis, growing along an altitudinal gradient at the Luliang Mountains in Northern China. Totally five tree-ring width chronologies were developed to explore the climate-growth responses of these tree species. No obviously regular trend associated with the increase of elevation was found by comparing the statistical characteristics of the chronologies. Correlation analysis indicated that the chronologies from lowerest to middle-high sites (SZ, BWD, BDGL and BDGP, respectively) were highly correlated, and different species from the same site showed the highest correlation. Growth-climate analysis indicated that the chronology of Larix principis-rupprechti at the uppermost site near the tree line (XWS) did not exhibit a significant response to the seasonal climatic factors, whereas the other four lower chronologies were consistently and significantly influenced by both the mean temperature from May to July and the total precipitation from March to June, regardless of tree species and elevation. The similarity of the tree growth-climate relationships of different species growing at different elevations (except that from the tree line) suggests that the trees in this region can provide common regional climate information, and combinations of multiple species (RC) are more successful in reconstructing the climate data than single species. The results of this research are very crucial for the future forest management and dendroclimatological sampling strategy in the arid to semi-arid area of northern China.</p

Climatic response of Chinese pine and PDSI variability in the middle Taihang Mountains, north China since 1873

We reconstructed the first Palmer Drought Severity Index (PDSI) in the Taihang Mountains, north China from 1873 to 2008, based on ring width of the Chinese Pine (Pinus tabulaeformis Carr). The reconstruction can explain 43.2 % of the PDSI from instrument record during the calibration period (1955-2005). The PDSI variability was relatively stable before the twentieth century. However, it became more variable and persistent during the twentieth and early twenty-first century. Persistent long dry intervals were found in 1920-1931, 1973-1982 and 1992-2001, and the wet intervals were identified in 1944-1965 and 2004-2008. Comparing with the 1920s, the dryness of the 1970s and 1990s were more intense and the 1990s ranked the most severe drought for the whole reconstructed period in the Taihang Mountains. After a decreasing trend since the 1950s, the PDSI shows increasing tendency after 2000, demonstrating a better moisture condition in recent years in the studied area. Comparisons of our reconstruction with nearby dry/wet index and other tree-ring-based PDSI reconstruction showed high consistency in dry (wet) periods, showing similar dry-wet regimes around the sampled site, which was also further proved by the spatial correlation analysis. This reconstruction is also highly correlated with the East Asian Summer Monsoon (EASM) index, suggesting the reconstructed PDSI could be used to indicate the strength of EASM. Spectral analysis revealed significant peaks at 2.05, 2.07, 2.65, 3.75, 10 and 60 years, implying the influence of larger circulation system (such as ENSO, PDO and NAO) and solar activity on local climate.</p

A dendroclimatic reconstruction of May-June mean temperature variation in the Heng Mounatins, north China, since 1767 AD

High-resolution tree-ring records covering the last hundreds years in north China are very scarce, yet essential for understanding the process and pattern of climate change and designing climate model. In this paper, a Chinese pine (Pinus tabulaformis Carr.) ring-width chronology spanning 1767-2008 AD was developed using standard dendroclimatological methods in the Heng Mountains, Shanxi province of north China. Strongly negative relationships were detected between the ring-width chronology and the monthly mean temperatures (minimum, mean, and maximum) from April to September during the growing season. Based on correlation analysis, the mean temperature from May to June was reconstructed back to 1767 AD. Both spatial correlation analysis with CRU grid dataset and comparisons with other tree-ring based temperature reconstructions from surrounding areas revealed that this reconstruction represented a larger-scale regional temperature variation for north-central China. Significant spectral peaks were found at 2.04-, 2.05-, 2.22-, 7.69-, 75- and 100-year, implying the possible influence of ENSO and solar activity on the local climate. Considering the strong and negative relationship between tree growth and temperature, the future warming will possibly bring increasing drought stress for the tree growth, as shown by the recent warming since the 1950s. However, due to the limit of tree age, this reconstruction did not capture the multi-century scale variations which presents the necessity for developing more and longer tree-ring chronologies in the future in north-central China.</p

Reconstruction of drought variability in North China and its associationwith sea surface temperature in the joining area of Asia andIndian–Pacific Ocean

Using tree-ring data from the northernmost marginal area of the East Asian summer monsoon (EASM) in North China, May–July mean Palmer drought severity index (PDSI) was reconstructed back to 1767 AD. The reconstruction captured 52.8% of the variance over the calibration period from 1945 to 2005 AD and showed pronounced pluvial periods during 1850–1905, 1803–1811 and 1940–1961 and dry periods during 1814–1844, 1916–1932 and 1984–2012. These anomalous periods have previously been reported in other parts of North China. Spatial correlation analyses and comparisons with other hydroclimatic indices in North China indicated that our new PDSI reconstruction could represent spatial and temporal drought variability in this region well. Our work also suggested that the drying tendency currently observed in the northern part of North China (including the study area) is consistent with the weakening of the EASM. Meanwhile the drying trend was seemingly restrained at present in the southern part of North China. Spatial correlation patterns with global sea surface temperature (SST) indicated that the regional hydroclimatic variability in North China was tightly linked to SST over the joining area of Asia and Indian–Pacific Ocean (AIPO), especially over the tropical western Pacific. When SST from prior November to current July (NJ-SST) in the AIPO area was anomalously high (low), the thermal contrast between Asian land and ocean was weakened (strengthened), and the EASM was correspondingly weakened (strengthened), thereby causing droughts (pluvials) in North China. The results of this study do not only provide useful information for assessing the long-term climate change in North China, but also suggest that abnormal variability in NJ-SST over the AIPO area could be used to forecast hydroclimatic conditions in North China

Long-term variation of temperature over North China and its links with large-scale atmospheric circulation

A May-July temperature reconstruction is based on tree-ring widths of Chinese pine (Pinus tabulaeformis) from Ningwu, Shanxi Province, China. The reconstruction explains 45.1% of the variance in observed May-July temperature. The intervals with persistent decadal warmth include 1779-1792, 1827-1839, 1853-1865, 1898-1932, 1936-1948 and 1987-2003. Intervals with persistent decadal cold include 1793-1807, 1814-1826, 1866-1888, 1949-1963 and 1976-1986. Spatial correlation between the reconstruction and the gridded temperature datasets reveals that the reconstruction is representative of temperature variability in semi-arid/arid regions of East Asia, including the Gobi Desert, the Loess Plateau and the North China Plain. The regions are referred to as North China in this study. Significant correlation with the January-August temperature reconstruction in the Helan Mountains of Northwest China for the overlapping period of 1796-1999 suggests that the reconstruction captures the regional temperature variability for a long-term period. The reconstructed temperature series has a significantly negative correlation with the monsoon rainfall series at inter-annual, decadal and multi-decadal time scales for the overlapping period of 1688-2003, suggesting an influence of the East Asian Summer Monsoon (EASM) and the dominant climate regime consisting of either cool/wet or warm/dry weather in the North China. Moreover, for the past three centuries, synchronous variations are found for the reconstructed temperature as well as the reconstructed Asian-Pacific Oscillation (APO) and the Pacific Decadal Oscillation (PDO) at decadal and multi-decadal time scales, suggesting the influences of large-scale atmospheric circulations on temperature variability in the North China. The possible mechanisms behind these links are also explained with observed climate data.</p

Amplitudes, rates, periodicities and causes of temperature variations in the past 2485 years and future trends over the central-eastern Tibetan Plateau

Amplitudes, rates, periodicities, causes and future trends of temperature variations based on tree rings for the past 2485 years on the central-eastern Tibetan Plateau were analyzed. The results showed that extreme climatic events on the Plateau, such as the Medieval Warm Period, Little Ice Age and 20th Century Warming appeared synchronously with those in other places worldwide. The largest amplitude and rate of temperature change occurred during the Eastern Jin Event (343-425 AD), and not in the late 20th century. There were significant cycles of 1324 a, 800 a, 199 a, 110 a and 2-3 a in the 2485-year temperature series. The 1324 a, 800 a, 199 a and 110 a cycles are associated with solar activity, which greatly affects the Earth surface temperature. The long-term trends (&gt;1000 a) of temperature were controlled by the millennium-scale cycle, and amplitudes were dominated by multi-century cycles. Moreover, cold intervals corresponded to sunspot minimums. The prediction indicated that the temperature will decrease in the future until to 2068 AD and then increase again.</p

Recent warming evidence inferred from a tree-ring-basedwinter-half year minimum temperature reconstructionin northwestern Yichang, South Central China, and its relationto the large-scale circulation anomalies

High-resolution winter temperature reconstructions in China are rare, yet vital for the comprehensive understanding of past climate change. In the present work, the first winter-half year minimum mean temperature from previous November to current April in northwestern Yichang, South Central China, was reconstructed back to 1875 based on tree-ring material. The reconstruction can explain 55 % of the variance over the calibration period during 1955&ndash;2011. The temperature maintained at comparatively low level before 1958, and an abnormal warming was seen since 1959. However, the warming trend stagnated after 2000 AD. 2001&ndash;2010 was the warmest decade not only during the instrumental period but also during the whole reconstructed period. The reconstruction indicates good spatial resemblance to other temperatures series in adjacent areas and Northern Hemisphere, yet the recent warming in this study is earlier and more prominent than that of Southeast China. This work also manifests that the winter-half year minimum temperature in study area has good agreement with summer (June&ndash; September) maximum temperature variation in Southeast China at decadal scale, except that the winter-half year warming in recent decades is more evident than summer. This reconstruction is not only useful in improving our knowledge of long-term temperature variation but also useful in predicting the tree growth dynamics in the future in the study area.</p

Tree-ring-based annual precipitation reconstruction in Kalaqin, Inner Mongolia for the last 238 years

A tree-ring-width chronology of Pinus tabulaeformis from Kalaqin, Inner Mongolia was developed using modern dendrochronological techniques. Based on the results of correlation function analysis, the total precipitation from the previous August to current July was reconstructed for 1771-2008 AD with an explained variance of 49.3%. The reconstruction correlated well with the dryness/wetness series derived from historical documents, as well as the precipitation reconstruction of the Chifeng-Weichang region. There were eight intervals with greater precipitation than the average (associated with the strong East Asian summer monsoon) and seven intervals lower than the average (weak monsoon). A power spectrum analysis showed that there were 120 a, 80 a, 8 a and 2 a periodicities.</p

Reconstructed May-July mean maximum temperature since 1745 AD based on tree-ring width of Pinus tabulaeformis in Qianshan Mountain, China

A tree-ring-width chronology of Pinus tabulaeformis was developed from the Qianshan Mountain, Liaoning province, northeastern China. Based on the correlation between the ring width and instrumental data, a transfer function was designed and the May-July mean maximum temperature (MMT) from 1745 to 2012 was reconstructed. The reconstruction explains 42.7% of the instrumental variance during the calibration period (41.7% after adjusting for the loss of the degrees of freedom). The reconstructed MMT is similar to several observed MMT series and the temperature index in north-central China, which indicated that the decrease in summer temperatures in the 20th century was a large scale phenomenon. The reconstruction also showed that high MMT values corresponded to historical drought events in Liaoning. In addition, a spatial Correlation analyses revealed that the MMT reconstruction is regionally representative. Significant 128.2-, 64.1-, 18.6-, 3.46-, 3.19-, 2.43-, 2.15- and 2.10-year cycles were detected in the reconstructed MMT series from Qianshan Mountain.</p