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14 pages, 6061 KiB

Open AccessArticle

Precipitation Variations in the Central Qilian Mountains since the 7th Century and Regional Differences: Evidence from Tree-Ring Data

by Taibang Zhang, Yong Zhang, Xuemei Shao and Xiuqi Fang

Forests 2024, 15(4), 624; https://doi.org/10.3390/f15040624 - 29 Mar 2024

Viewed by 562

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)

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17 pages, 5787 KiB

Open AccessArticle

Two Centuries of Winter Temperature Variability Inferred from Betula ermanii Ring Widths near the Forests/Tundra Ecotone in the Changbai Mountain, China

by Siwen Li, Xiaoyang Cui and Yangao Jiang

Forests 2024, 15(1), 220; https://doi.org/10.3390/f15010220 - 22 Jan 2024

Viewed by 1517

Abstract

In this study, we constructed a ring-width chronology derived from Betula ermanii (BE) near the transitional zone between forests and tundra within the Changbai Mountain (CBM) region. This chronology was established utilizing 55 cores obtained from 30 trees. Our analysis of growth/climate responses [...] Read more.

In this study, we constructed a ring-width chronology derived from Betula ermanii (BE) near the transitional zone between forests and tundra within the Changbai Mountain (CBM) region. This chronology was established utilizing 55 cores obtained from 30 trees. Our analysis of growth/climate responses underscores the pivotal role of the mean maximum winter temperature in influencing radial growth. Drawing upon these growth/climate associations, we reconstructed the mean maximum temperature series for December of the preceding year through January of the current year for the years 1787 and 2005 CE, employing a standardized chronology. During the calibration period (1960–2005), the reconstructed series exhibited an explained variance of 36%. This reconstruction provides crucial insights into historical temperature fluctuations within the study area. Our findings indicate that year-to-year temperature variations did not manifest synchronously along the altitude gradient of Changbai Mountain. Notably, the response to recent winter warming exhibited disparities with the altitude on Changbai Mountain. Specifically, the higher altitude range (1950–2000 m a.s.l.) displayed a response to warming around 1960, the mid-altitude range (765–1188 m a.s.l.) responded around 1975, and the lowest altitude (650 m a.s.l.) responded by 1977. Consequently, the paleotemperature research outcomes from Changbai Mountain alone may not adequately characterize climate change in this region. We recommend future high-resolution temperature records be obtained through sampling at various altitudes to enhance the comprehensiveness of our understanding. Full article

(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)

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15 pages, 10381 KiB

Open AccessArticle

Tree-Ring Stable Oxygen Isotope Ratio (δ¹⁸O) Records Precipitation Changes over the past Century in the Central Part of Eastern China

by Changfeng Sun, Xuan Wu, Qiang Li, Yu Liu, Meng Ren, Qiufang Cai, Huiming Song and Yongyong Ma

Forests 2024, 15(1), 128; https://doi.org/10.3390/f15010128 - 08 Jan 2024

Viewed by 1046

Abstract

Fully understanding the past characteristics of climate and patterns of climate change can contribute to future climate prediction. Tree-ring stable oxygen isotope ratio (δ¹⁸O) is crucial for high-resolution research of past climate changes and their driving mechanisms. A tree-ring δ¹⁸ [...] Read more.

Fully understanding the past characteristics of climate and patterns of climate change can contribute to future climate prediction. Tree-ring stable oxygen isotope ratio (δ¹⁸O) is crucial for high-resolution research of past climate changes and their driving mechanisms. A tree-ring δ¹⁸O chronology from 1896 to 2019 was established using Pinus tabulaeformis Carr. from the Yimeng Mountains (YMMs) in the central part of eastern China. We found that precipitation from the 41st pentad (five days) of the previous year to the 40th pentad of the current year (P_41–40) was the main factor influencing the YMMs tree-ring δ¹⁸O change. We then created a transfer function between P_41–40 and tree-ring δ¹⁸O. The reconstructed P_41–40 explained 39% of the variance in the observed precipitation during the common period of 1960–2016. Over the past 124 years, the YMMs experienced 19 dry years and 20 wet years. The spatial correlation results indicate that the reconstructed precipitation could, to some extent, represent the precipitation changes in Shandong Province, and even the central part of eastern China, from the early 20th century to the present. In addition, it was found that the trends in YMMs tree-ring δ¹⁸O were similar at both high frequency and low frequency to those in tree-ring δ¹⁸O series from Mt. Tianmu in eastern China and from Jirisan National Park in southern South Korea. However, the YMMs tree-ring δ¹⁸O was only correlated at low frequency with the tree-ring δ¹⁸O of the Ordos Plateau in northwestern China and that of Nagano and Shiga in central Japan, which are far from the YMMs. The changes in precipitation and tree-ring δ¹⁸O in the YMMs were, to some extent, influenced by the Pacific decadal oscillation. Full article

(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)

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16 pages, 5110 KiB

Open AccessArticle

Drought Variations in the Yili Basin, Northwest China since AD 1673 Based on Tree-Ring Width

by Yifan Wu, Yu Liu, Qiang Li, Qiufang Cai, Meng Ren, Huiming Song, Changfeng Sun, Tongwen Zhang and Mao Ye

Forests 2023, 14(11), 2127; https://doi.org/10.3390/f14112127 - 25 Oct 2023

Viewed by 1028

Abstract

The Yili Basin represents a typical region influenced by the Westerlies, and as a result of the substantial precipitation delivered by these winds, it has emerged as a significant hub for agricultural and animal husbandry activities in Central Asia. This study established a [...] Read more.

The Yili Basin represents a typical region influenced by the Westerlies, and as a result of the substantial precipitation delivered by these winds, it has emerged as a significant hub for agricultural and animal husbandry activities in Central Asia. This study established a 419-year tree-ring width chronology, utilizing living Picea schrenkiana samples from two sampling sites in the Yili Basin. Correlation analysis showed that the standard tree-ring width chronology had the best correlation with the Palmer Drought Severity Index from the previous August to the current May (PDSI_P8C5) (r = 0.614, n = 59, p < 0.001). Therefore, we reconstructed PDSI_P8C5 variations from 1673 to 2018. The reconstruction results reveal eight wet and seven dry periods during the past 346 years. In the reconstructed series, droughts are particularly pronounced around 1770 and 1920, and the PDSI shows a significant long-term wetting trend since the 1980s. The solar activity, North Atlantic Oscillation (NAO), and Atlantic Multidecadal Oscillation (AMO) jointly influenced the regional moisture variation. Full article

(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)

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17 pages, 4218 KiB

Open AccessArticle

Responses of Tree Growth and Intrinsic Water Use Efficiency to Climate Factors and Human Activities in Upper Reaches of Tarim River in Alaer, Xinjiang, China

by Yuanda Ye, Yu Liu, Meng Ren, Qiufang Cai, Changfeng Sun, Qiang Li, Huiming Song, Mao Ye and Tongwen Zhang

Forests 2023, 14(9), 1873; https://doi.org/10.3390/f14091873 - 14 Sep 2023

Viewed by 865

Abstract

With global warming and increasing human activities, exploring the impact of the rising atmospheric carbon dioxide concentration and climate change on forest ecosystems is crucial. In this study, we focus on Euphrates poplar (Populus euphratica Oliv.) in the upper reaches of the [...] Read more.

With global warming and increasing human activities, exploring the impact of the rising atmospheric carbon dioxide concentration and climate change on forest ecosystems is crucial. In this study, we focus on Euphrates poplar (Populus euphratica Oliv.) in the upper reaches of the Tarim River in the Alaer region of Xinjiang. We use dendrochronological methods, tree-ring width, and stable carbon isotope series to explain basal area increment (BAI) and intrinsic water use efficiency (iWUE) changes. We further explore the influence of past climate change and human activities on the radial growth and iWUE of P. euphratica through stable oxygen isotope analysis combined with historical literature records. The results showed that relative humidity had an essential effect on Δ¹³C and δ¹⁸O fractionation in P. euphratica tree rings, whereas the vapor pressure deficit (VPD) was considered the main factor influencing the inter-annual variability of the iWUE and BAI. Since 1850, long-term variations in iWUE have exhibited an upward trajectory correlated with rising atmospheric CO₂ levels. Approximately 13% of this iWUE increase can be attributed to changes in carbon-concentration-induced water use efficiency (^cciWUE). Although Δ¹³C and δ¹⁸O were generally uncorrelated between 1850 and 2018, around 1918, their relationship changed from being weakly correlated to being significantly negatively correlated, which may record changes related to the upstream Tarim River diversion. During the period from 1850 to 2018, both the BAI and iWUE showed an increasing trend for P. euphratica growth; however, the relationship between them was not stable: during 1850–1958, both variables were mainly influenced by climatic factors, while during 1959–2018, the most important influence was due to human activities, specifically agricultural development and irrigation diversions. An abrupt surge in the BAI was observed from 1959 to 1982, reaching its peak around 1982. Surprisingly, post-1983, the escalating iWUE did not correspond with a continuation of this upward trajectory in the BAI, highlighting a divergence from the previous trend where the enhanced iWUE no longer facilitated the growth of P. euphratica. Despite P. euphratica having adapted to the continuously rising C_a, improving its iWUE and growth capacity, this adaptive ability is unstable and may easily be affected by human activities. Overall, the increase in C_a has increased the iWUE of P. euphratica and promoted its growth at a low frequency, while human activities have promoted its development at a high frequency. Full article

(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)

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14 pages, 6124 KiB

Open AccessArticle

A 250-Year Winter Minimum Temperature Reconstruction Based on Tree Rings from Luoji Mountain, Southwest China

by Jianfeng Peng, Jinbao Li, Jingru Li and Teng Li

Forests 2023, 14(8), 1555; https://doi.org/10.3390/f14081555 - 29 Jul 2023

Viewed by 968

Abstract

Annually resolved temperature records spanning the past few centuries are limited in Southwest China. In this paper, we present a robust 250-year winter minimum temperature reconstruction based on the tree rings of Abies georgei Orr from Luoji Mountain, Southwest China. The tree rings [...] Read more.

Annually resolved temperature records spanning the past few centuries are limited in Southwest China. In this paper, we present a robust 250-year winter minimum temperature reconstruction based on the tree rings of Abies georgei Orr from Luoji Mountain, Southwest China. The tree rings exhibit significant correlations with winter minimum temperatures (Tmin) from the previous November to the current March (pNov–cMar). Based on this relationship, we reconstructed pNov-cMar Tmin from 1765 to 2014. This reconstruction accounts for 37.8% of the Tmin variance during the instrumental 1960–2014 period. Our reconstruction reveals five warm periods (1765–1785, 1795–1804, 1827–1883, 1901–1907, 1989–2014) and four cold periods (1786–1794, 1805–1826, 1884–1900, 1908–1988) over the past 250 years. Spectral analyses revealed several significant interannual (2.3–2.4a, 3.9–4.2a, 8.9–9.7a) and interdecadal (23.0–28.9a) cycles in our reconstruction series. Both spatial correlation analysis and the inter-comparison of paleoclimate records revealed that the winter Tmin reconstruction had significant positive correlations with the Atlantic Multidecadal Oscillation (AMO), with relatively consistent warm and cold periods in their variations over the past 250 years. Full article

(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)

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16 pages, 4028 KiB

Open AccessArticle

A 195-Year Growing Season Relative Humidity Reconstruction Using Tree-Ring Cellulose δ¹³C in the Upper Tarim River Basin, NW China

by Yuanda Ye, Yu Liu, Qiang Li, Meng Ren, Qiufang Cai, Changfeng Sun, Huiming Song, Teng Li, Mao Ye and Tongwen Zhang

Forests 2023, 14(4), 682; https://doi.org/10.3390/f14040682 - 26 Mar 2023

Cited by 1 | Viewed by 1300

Abstract

Reconstruction of relative humidity changes in the upper Tarim River using carbon isotopic tree-ring chronology bridges the gap in historical observations on the Tarim River Basin in Arid Central Asia. Populus euphratica Olivier (P. euphratica), growing in the Tarim River Basin [...] Read more.

Reconstruction of relative humidity changes in the upper Tarim River using carbon isotopic tree-ring chronology bridges the gap in historical observations on the Tarim River Basin in Arid Central Asia. Populus euphratica Olivier (P. euphratica), growing in the Tarim River Basin of Xinjiang, is an excellent record of past climate change. Based on precise dating, we analysed alpha-cellulose stable carbon isotopes in four cores of P. euphratica taken from the Alaer region of the upper Tarim River Basin. The four stable carbon isotope series records were corrected by the “pin method” and then combined into a carbon isotopic discrimination (Δ¹³C) series by the “numerical mix method”. The discrimination (Δ¹³C) series were clearly correlated with the mean relative humidity (RH_AS) in April–September of the growing season (n = 60, r = −0.78, p < 0.001), and according to the climate response analysis, we designed a simple regression equation to reconstruct the mean relative humidity (RH_AS) in April–September from 1824 to 2018 on the Alaer region. The reconstructed sequence showed mainly dry periods in the last 195 years, 1857–1866 and 1899–1907, while primarily wet periods from 1985 to 2016. Due to increased global warming and human activities, the climate shifted from “warm–dry” to “warm–wet” in the mid-to-late 1980s, when there were signs of a shift from “warm–wet” to “warm–dry” in the 2010s, with an increasing trend towards aridity. The RH_AS series of Alaer compares well to other hydroclimate series’ surrounding the research area, and the spatial correlation analysis indicates that the reconstructed series has good regional representativeness. On an interdecadal scale, the revamped RH_AS series is positively correlated with the Atlantic Multidecadal Oscillation (AMO) and negatively correlated with the North Atlantic Oscillation (NAO), reflecting the influence of westerly circulation on regional wet and dry variability. At the same time, the RH_AS may also be influenced by The Pacific Decadal Oscillation (PDO). Full article

(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)

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13 pages, 4398 KiB

Open AccessArticle

Water Stress-Induced Divergence Growth of Picea schrenkiana in the Western Tianshan and Its Forcing Mechanisms

by Teng Li, Yu Liu, Qiufang Cai, Xiangyu Duan, Pei Li, Meng Ren and Yuanda Ye

Forests 2023, 14(2), 354; https://doi.org/10.3390/f14020354 - 10 Feb 2023

Cited by 2 | Viewed by 1237

Abstract

Since the 1950s, divergence problems have reduced the temporal stability of tree rings in response to climate, shaken the foundations of dendroclimatology, and affected the reliability of reconstructed models based on tree rings and the accuracy of historical climate series. Therefore, it is [...] Read more.

Since the 1950s, divergence problems have reduced the temporal stability of tree rings in response to climate, shaken the foundations of dendroclimatology, and affected the reliability of reconstructed models based on tree rings and the accuracy of historical climate series. Therefore, it is of great importance to investigate divergence problems, which will help us to better understand the growth strategies of trees in response to climate warming and provide a scientific basis for accurate climate reconstruction and simulation of forest dynamics. This paper aims to elucidate the mechanism of divergent growth of Picea schrenkiana at high altitudes in the western Tianshan from three aspects: variations in atmospheric circulation, changes in climatic factors, and the coping strategy of trees with climate change. High spring temperatures accelerate the melting of snow cover. Large amounts of snowmelt initially replenish soil water, leading to the rapid growth of trees, but later, the continuous consumption of snowmelt reduces the available water capacity of soil, resulting in water stress on trees. The pattern of trees’ response to changes in climate ranges from a pure temperature limitation to a collaborative temperature–moisture limitation. Since the 1990s, the weakening of the westerly circulation and the North Atlantic Oscillation has reduced their impacts on the hydroclimate in the Tianshan Mountains of Central Asia. The combination of heat-induced water deficit and a long-term weakening trend in atmospheric circulation has slowed tree growth over the past decade. Full article

(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)

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