The Aksu area is located in western Xinjiang, China, where an oasis is the main space for human production and life in this region. The stability of the oasis is crucial for societal and economic ...development and can be severely impacted by continued drought. The Palmer Drought Severity Index (PDSI), a widely applied index for dryness, has been reconstructed in many areas by tree rings. Here we develop a new regional long tree-ring-width chronology of Schrenk’s spruce (
Picea schrenkiana
Fisch. et Mey.) from the Aksu area. Based on the regional PDSI from the previous September to current March (PDSI
p9–c3
), regional drought variability is reconstructed in the past 548 years (1466–2013 CE). The regional PDSI reconstruction captures distinct wet and dry periods and also some low-frequency climate signals. A decadal analysis reveals 12 wet and 12 dry periods in the past 548 years, of which 1514–1560 CE was the longest dry period. The prominent mega-drought during the mid-sixteenth century is particularly pronounced. The PDSI in the Aksu area records a notable sudden onset and long period of wet conditions from the 1980s until the present day. Mechanism analysis indicates that the regional drought has been mainly affected by the North Atlantic Oscillation (NAO) over the last centuries through an anti-phase relationship.
Mass movements in China typically encompass landslides, rockfalls, and debris flows, and these processes affect almost 70% of all mountain areas of China. An improved understanding of geomorphic ...process dynamics and their drivers and process histories are important prerequisites for a proper assessment and a sustainable management of mountain hazards. Tree rings have on varied occasions proven to be a reliable tool for the acquisition of data on past mountain hazards. Here we present the first reconstruction of past landslide activity on a slope in the Qilian Mountains, northeast Tibetan Plateau, China. To this end, a total of 543 Qilian juniper (Sabina przewalskii Kom.) samples were selected from 239 trees growing on or next to a complex landslide body, with the aim to reconstruct past landslide histories at the site. The dataset of disturbed trees was complemented with 174 increment cores from 84 reference Qilian juniper trees growing on three adjacent, yet undisturbed sites. Based on the dating of the samples and the interpretation of growth disturbances (GD) in the tree-ring series of affected trees, we provide the first reconstruction of past landslides as retrieved from a dendrogeomorphic record covering more than a millennium (956–2011 CE). Results show that the first detectable GD occurred as early as in 1042 CE, followed by seven major landslide reccurrences in 1703, 1816, 1848, 1863, 1913, 1970, and 1982. Comparison between our landslide record and a dendroclimatic precipitation reconstruction points to the crucial role of major, longer-term wet precipitation anomalies on landslide occurrence.
•We present the longest, tree-ring based landslide reconstruction.•Qilian junipers allow centennial-scale reconstruction of complex landslide processes.•Landslides are caused by successive wet years or extreme rainfalls.•Earthquakes do not seem to trigger landslides at the site.
The development of sports in children is crucial. Unlike European and American sports clubs, China uses children's sports schools as its main form of competitive sports training. However, with the ...changing economy and mindset in China, this approach is facing challenges and is in urgent need of changes allowing the school and its internal staff to be more sustainable as they can adapt and survive in the overall market. This change means that such schools can no longer simply rely on government assistance but rather must be more in tune with the market economy and gain competitiveness. Zhangjiakou, China, one of the host cities for the 2022 Beijing Winter Olympics, has a good overall sports atmosphere. Its municipal government attaches importance to sports development, including children's sports, with several children's sports schools that are typical of this study. Accordingly, seven Zhangjiakou sports schools were selected for investigation through field research and sampling. Moreover, the sources of resistance to change in Zhangjiakou children's sports schools were analyzed from multiple perspectives, including external politics and economy, internal group and individual perspectives, using data from questionnaires and in-depth interviews.
Global warming has a significant impact on the ecosystem of the high‐altitude areas of the Tibetan Plateau, such as land degradation and the rapid retreat of glaciers. It is important to understand ...the effects of global warming occurring over hundreds or thousands of years. However, the long‐term reconstruction of temperature is still lacking for the region of Western Sichuan Plateau (WSP). In this study, we reconstructed summer (June–July) temperatures back to 1383 for the WSP region based on a significant positive correlation between the standard chronology and summer temperature. The reconstruction passed statistical tests and explained 55.4% of the climatic variance in the period for which data are available (1962–2005). There have been five periods with warm summers and five with cold summers during the past 623 years. Warm periods occurred in 1383–1445, 1525–1590, 1700–1724, 1825–1870, and 1930–1960, while relatively cold periods occurred in 1446–1524, 1591–1675, 1725–1824, 1900–1929, and 1961–1990. A comparison with observed data and regional temperature reconstruction series shows that the reconstruction has a high degree of consistency and is indicative and reliability. The spatial correlation was analysed with Climatic Research Unit gridded data to detect the spatial representativeness of the reconstruction, confirming that the reconstruction has a strong regional temperature signal for the WSP. Furthermore, ensemble empirical mode decomposition indicates quasi‐oscillations of 2.8–3.3, 6.4–8.3, 11.1–14.2, 25–38.4, 89, and 138 years in the reconstructed temperature time series during the past 623 years. El Niño Southern Oscillation cycles, solar activity, and Atlantic multi‐decadal oscillation may be the primary forcing factors. Meanwhile, the coordinated action of temperature‐induced drought stress with a late growing season related to delayed snowmelt can potentially be attributed to the divergence problem (observed around 2005).
This work provided a new tree‐ring‐based temperature reconstruction on the Western Sichuan Plateau and investigated the periodic variations on different timescales imprinted in the reconstructed temperature series by using ensemble empirical mode decomposition. The result suggested that El Niño Southern Oscillation cycles, solar activity, and Atlantic multi‐decadal oscillation may be the primary forcing factors of regional temperature variations. Further, we explored the possible factors, which may potentially attributed to the divergence problem.
Tree growth trends can affect the interpretation of the response of tree-ring proxies (especially tree-ring width) to climate in the low-frequency band, which in turn may limit quantitative ...understanding of centennial-scale climate variability. As such, it is difficult to determine if long-term trends in tree-ring measurements are caused by age-dependent growth effects or climate. Here, a trend similarity ranking method is proposed to define the range of tree growth effects on tree-ring width chronologies. This method quantifies the inner and outer boundaries of the tree growth effect following two extreme standardization methods: curve fitting standardization and regional curve standardization. The trend similarity ranking method classifies and detrends tree-ring measurements according to the ranking similarity between the regional growth curve and their long-term trends through curve fitting. This standardization process mainly affects the secular trend in tree-ring chronologies, and has no effect on their inter-annual to multi-decadal variations. Applications of this technique to the Yamal and Torneträsk tree-ring width datasets and the maximum latewood density dataset from northern Scandinavia reveals that multi-centennial and millennial-scale temperature variations in the three regions provide substantial positive contributions to the linear warming trends in the instrumental period, and that the summer warming rate during the 20th century is not unprecedented over the past two millennia in any of the three regions.
The Qilian Mountains, located in northwest China and serving as a crucial water recharge area, have exhibited significant regional differences in precipitation patterns in recent decades. However, ...the limited temporal coverage of instrumental data has hindered a deep understanding of hydroclimate variations and regional differences. Further investigation into their long-term spatial and temporal precipitation characteristics is urgently needed. In this study, a new tree-ring-width chronology spanning 1743 years was established in the central Qilian Mountains using Qilian juniper (Juniperus przewalskii Kom.) samples. Significant correlations were found between the tree-ring indices and precipitation during both the growing and pre-growing seasons. Based on these correlations, annual precipitation from August of the previous year to July of the current year was reconstructed. The reconstruction model successfully explains 34.5% of the variation in precipitation during the calibration period. The analysis of the reconstructed series reveals notable interannual to multi-decadal dry–wet variability during the period from 614 AD to 2016 AD. The mid- to late-15th century emerges as the longest-lasting dry period, while the last decade stands out as the wettest. Comparative analysis with other precipitation reconstructions in the eastern and western Qilian Mountains reveals that regional drought events tend to be more pronounced and enduring. Low-frequency fluctuations on decadal to century scales show distinct wet and dry periods in the 12th–18th centuries in both the eastern and western parts of the Qilian Mountains, with weaker fluctuations in subsequent centuries. However, the central part of the Qilian Mountains exhibits opposite trends, possibly due to the complex interactions of multiple circulation systems.
Understanding of past climatic variability over the Tibetan Plateau is still limited because of the lack of long-term climatic records. Here we reconstruct the mean summer (June–August) minimum ...temperature for the past 379 years based on tree-ring data in the source region of the Yangtze River. This reconstruction successfully captures recent abrupt climatic changes and agrees in general with other temperature reconstructions for the Tibetan Plateau on a decadal timescale. The cold and warm periods coincide with documented glacier advances and retreats on the east and southeast Tibetan Plateau. The interval 1816–22 is among the coldest periods in the reconstruction and may be related to the influence of the Tambora eruption in Indonesia in 1815. Comparisons with other paleoclimatic proxies imply a high degree of confidence for our reconstruction and its indicative power for a large-scale climate variability on the Tibetan Plateau.
Moisture conditions, especially those that occur as multi-decadal anomalies, have profound impacts on society, especially in arid and semi-arid regions. However, the lack of high-resolution climate ...data for the first millennium CE greatly limits our understanding of how moisture variations have influenced history. Here, we present an 1882-year (134–2015 CE) tree-ring chronology developed from Qilian juniper (
Juniperus przewalskii
Kom.) growing in the western Qilian Mountains, northwest China. The tree-ring index correlates significantly with the May–June self-calibrating Palmer Drought Severity Index (sc-PDSI) and can be used to reconstruct May–June moisture variations since 241 CE. The reconstruction reflects moisture conditions at the annual to multi-decadal time scales over the past two millennia. During the period from the third to eighth centuries, there were prominent interdecadal fluctuations, with the third century and the late fifth century being the wettest and driest periods during the reconstruction, respectively. The transition from the wet third century to the dry fifth century corresponded with key events in Chinese history, namely the demise of the Western Jin Dynasty and the chaotic Southern and Northern Dynasties. Thus, our reconstruction provides new evidence for the potential linkage between abnormal climate conditions and social changes in ancient times.
•The tree-ring width chronology was developed during CE 1685–2017.•High coherence between the chronology and the total October-June precipitation.•A precipitation series was reconstructed for the ...central Lesser Khingan Mountains.•The Asian polar vortex is a factor influencing the precipitation in our study area.
Inter-annual variations of precipitation play important roles in forest management and agricultural production. This study presents a 270-year precipitation reconstruction of winter to early growing season for the central Lesser Khingan Mountains, Northeast China based on tree-ring width data of 99 tree-ring cores of Korean pine from two sampling sites near Yichun city. The reconstruction explained 46% of the variance in precipitation from the previous October to current June during the calibration period CE 1959–2017. At decadal scale, we identified four dry periods that occurred during CE 1748–1759, 1774–1786, 1881–1886 and 1918–1924, and four wet periods occurring during CE 1790–1795, 1818–1824, 1852–1859 and 2008–2017, and the period CE 2008–2017 was the wettest in the past 270 years. Power spectral analysis and wavelet analysis revealed cyclic patterns on the inter-annual (2–3 years) and inter-decadal (~11 and ~30–60 years) timescales in the reconstructed series. In addition, the Asian polar vortex has an important effect on the precipitation in our study area.
Daily and monthly maximum and minimum surface air temperatures at 66 weather stations over the eastern and central Tibetan Plateau with elevations above 2000 m were analyzed for temporal trends and ...spatial variation patterns during the period 1961–2003. Statistically significant warming trends were identified in various measures of the temperature regime, such as temperatures of extreme events and diurnal temperature range. The warming trends in winter nighttime temperatures were among the highest when compared with other regions. We also confirmed the asymmetric pattern of greater warming trends in minimum or nighttime temperatures as compared to the daytime temperatures. The warming in regional climate caused the number of frost days to decrease significantly and the number of warm days to increase. The length of the growing season increased by approximately 17 days during the 43‐year study period. Most of the record‐setting months for cold events were found in the earlier part of the study period, while that of the warm events occurred mostly in the later half, especially since the 1990s. The changes in the temperature regime in this region may have brought regional‐specific impacts on the ecosystems. It was found that grain production in Qinghai Province, located in the area of prominent warming trends, exhibited strong correlations with the temperatures, although such relationships were obscured by the influence of precipitation in this arid/semiarid environment in juniper tree ring records. In western Sichuan Province under a more humid environment, the tree growth (spruces) was more closely related to the changing temperatures.
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