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11 pages, 5590 KiB

Open AccessArticle

A Tree-Ring-Based Precipitation Reconstruction since 1760 CE from Northeastern Tibetan Plateau, China

by Youping Chen, Feng Chen and Heli Zhang

Atmosphere 2021, 12(4), 416; https://doi.org/10.3390/atmos12040416 - 24 Mar 2021

Cited by 4 | Viewed by 2504

Hydroclimatic conditions and related water resources change in the Tibetan Plateau is one of the main concerns for future sustainable development in China. This study presents a 254-year precipitation reconstruction from August of the previous year to June of the current year for [...] Read more.

Hydroclimatic conditions and related water resources change in the Tibetan Plateau is one of the main concerns for future sustainable development in China. This study presents a 254-year precipitation reconstruction from August of the previous year to June of the current year for the northeastern Tibetan Plateau based on tree-ring width data of tree-ring cores of Picea crassifolia from three sampling sites. The precipitation reconstruction explained 51.4% of the variance in instrumental precipitation during the calibration period 1958–2013. Dry periods with precipitation below the 254-year average value occurred during 1848–1865, 1873–1887, 1898–1923, and 1989–2003, and wet periods (precipitation above the mean) occurred during 1769–1785, 1798–1833, 1924–1938, 1957–1968, and 2004–2013. Spatial correlation analyses with the precipitation gridded dataset showed that our reconstruction contains some strong regional-scale precipitation signals for the upper Yellow River Basin. Our precipitation reconstruction also agreed in general with other dendroclimatic precipitation reconstructions from surrounding regions. In addition, reconstructed precipitation changes were consistent with the streamflow variation of the Yellow River. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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12 pages, 3066 KiB

Open AccessArticle

June–July Temperature Reconstruction of Kashmir Valley from Tree Rings of Himalayan Pindrow Fir

by Rayees Malik and Raman Sukumar

Atmosphere 2021, 12(3), 410; https://doi.org/10.3390/atmos12030410 - 23 Mar 2021

Cited by 7 | Viewed by 2321

Abstract

The Himalaya is one of the major mountain ecosystems that is most likely to be impacted by climate change. The main drawback in understanding climate change in the remote Himalayan ecosystems is the lack of long-term instrumental climate records. Reconstructing past climates from [...] Read more.

The Himalaya is one of the major mountain ecosystems that is most likely to be impacted by climate change. The main drawback in understanding climate change in the remote Himalayan ecosystems is the lack of long-term instrumental climate records. Reconstructing past climates from tree-rings offers a useful proxy for adding data to the instrumental climate records. In this study, climatically sensitive tree-rings of Himalayan fir (Abies pindrow) were used for reconstruction of mean June–July temperatures of Kashmir valley. Total ring-width chronology was built from 60 tree-ring cores growing near the higher altitudinal limits of the species. The radial growth showed a strong positive response to growing season temperature. The strong response of site chronology to mean June–July temperatures was used for reconstruction purposes. Mean June–July temperatures of Kashmir valley were reconstructed since 1773 from residual site chronology. Though the reconstruction did not show any strong long-term trend, on a centennial-scale, 20th-century summers were the warmest with a mean annual summer temperature of 22.99 °C. Seven of the warmest years and five of the warmest decades were seen in the 20th century. The reconstruction for 1773–2012 showed 23 extreme hot summers above the hot threshold of a 23.47 °C mean temperature and 19 extreme cold years below the cold threshold of a 22.46 °C mean summer temperature. The cold years in the reconstruction did not coincide with known volcanic eruptions. This reconstruction will help in providing a better understanding of regional climate change. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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15 pages, 4032 KiB

Open AccessArticle

Dendrochronological Potential of Drought-Sensitive Tree Stands in Armenia for the Hydroclimate Reconstruction of the Lesser Caucasus

by Magdalena Opała-Owczarek, Hrachuhi Galstyan, Piotr Owczarek, Hovik Sayadyan and Trahel Vardanyan

Atmosphere 2021, 12(2), 153; https://doi.org/10.3390/atmos12020153 - 26 Jan 2021

Cited by 1 | Viewed by 2341

Abstract

Existing high-resolution reconstructions of hydroclimate variability in the Caucasus are lacking tree-ring data from Armenian Plateau, the most continental part of the region. Our research presents the first dendrochronological investigation in Armenia. Juniper and oak tree-ring width chronologies were constructed, the longest spanning [...] Read more.

Existing high-resolution reconstructions of hydroclimate variability in the Caucasus are lacking tree-ring data from Armenian Plateau, the most continental part of the region. Our research presents the first dendrochronological investigation in Armenia. Juniper and oak tree-ring width chronologies were constructed, the longest spanning the last 140 years. The positive influence of spring–summer precipitation and the negative influence of temperature suggest drought stress at the investigated sites. Moving correlation analysis indicated a significant change over time in the sensitivity of investigated trees to climatic variability; juniper, previously sensitive to both temperature and precipitation, has shown especially strong precipitation signals in the recent decades since the local climate has turned more arid. Ongoing climate change increases drought stress in juniper, which may have further consequences on semiarid ecosystems. Our results reveal multiannual droughts recorded by tree rings, emerging in most parts of the Black Sea–Caspian Sea region. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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25 pages, 6870 KiB

Open AccessArticle

Comparing Approaches for Reconstructing Groundwater Levels in the Mountainous Regions of Interior British Columbia, Canada, Using Tree Ring Widths

by Stephanie C. Hunter, Diana M. Allen and Karen E. Kohfeld

Atmosphere 2020, 11(12), 1374; https://doi.org/10.3390/atmos11121374 - 19 Dec 2020

Cited by 5 | Viewed by 2271

Abstract

Observed groundwater level records are relatively short (<100 years), limiting long-term studies of groundwater variability that could provide valuable insight into climate change effects. This study uses tree ring data from the International Tree Ring Database (ITRDB) and groundwater level data from 22 [...] Read more.

Observed groundwater level records are relatively short (<100 years), limiting long-term studies of groundwater variability that could provide valuable insight into climate change effects. This study uses tree ring data from the International Tree Ring Database (ITRDB) and groundwater level data from 22 provincial observation wells to evaluate different approaches for reconstructing groundwater levels from tree ring widths in the mountainous southern interior of British Columbia, Canada. The twenty-eight reconstruction models consider the selection of observation wells (e.g., regional average groundwater level vs. wells classified by recharge mechanism) and the search area for potential tree ring records (climate footprint vs. North American Ecoregions). Results show that if the climate footprint is used, reconstructions are statistically valid if the wells are grouped according to recharge mechanism, with streamflow-driven and high-elevation recharge-driven wells (both snowmelt-dominated) producing valid models. Of all the ecoregions considered, only the Coast Mountain Ecoregion models are statistically valid for both the regional average groundwater level and high-elevation recharge-driven systems. No model is statistically valid for low-elevation recharge-driven systems (rainfall-dominated). The longest models extend the groundwater level record to the year 1500, with the highest confidence in the later portions of the reconstructions going back to the year 1800. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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15 pages, 7061 KiB

Open AccessArticle

Combination of Tree Rings and Other Paleoclimate Proxies to Explore the East Asian Summer Monsoon and Solar Irradiance Signals: A Case Study on the North China Plain

by Qiang Li, Yu Liu, Ruolan Deng, Ruoshi Liu, Huiming Song, Yan Wang and Gang Li

Atmosphere 2020, 11(11), 1180; https://doi.org/10.3390/atmos11111180 - 01 Nov 2020

Cited by 4 | Viewed by 2153

Abstract

Paleoclimate research, which involves the study of climate and environmental changes in historical and geological periods, is typically conducted using high-resolution paleoclimatic proxies, such as tree rings, historical documentations, stalagmite, and ice core. Although each paleoclimate proxy has its own merits in paleoclimatic [...] Read more.

Paleoclimate research, which involves the study of climate and environmental changes in historical and geological periods, is typically conducted using high-resolution paleoclimatic proxies, such as tree rings, historical documentations, stalagmite, and ice core. Although each paleoclimate proxy has its own merits in paleoclimatic research, reconstructions based on a single proxy may suffer from shortcomings, including insufficient reliability and low coverage of the representative area. It may be possible to overcome these shortcomings by combining multi-paleoclimatic proxies to understand paleoclimatic changes. In this study, we attempt to combine tree-ring stable oxygen isotope ratio (δ¹⁸O), tree-ring width, and stalagmite thickness data as well as historical records to establish a 320-year (1675–1994) time series using principal component analysis in the water-scarce North China Plain (NCP). The results show that the first principal component (PC1) series is closely related to regional precipitation and the maximum temperature in summer. The spatial correlation pattern indicates that the PC1 series can represent the regional hydroclimate variation not only in the NCP but also in all of northern China. The significant (p < 0.001) correlations between the PC1 series and several East Asian summer monsoon (EASM) indices prove that the PC1 reflects the intensity of the EASM. The PC1 series is consistent with the interannual variations of two reconstructed solar activity correlation indexes (r = 0.48 and 0.46, n = 320, and p < 0.001). The results indicate that the hydroclimate variation in the NCP is affected by large-scale atmospheric circulations, such as EASM and solar activity, and shows the potential of combining multiple paleoclimate proxies for analyzing regional climate change. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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11 pages, 3408 KiB

Open AccessArticle

A 422-Year Reconstruction of the Kaiken River Streamflow, Xinjiang, Northwest China

by Heli Zhang, Huaming Shang, Feng Chen, Youping Chen, Shulong Yu and Tongwen Zhang

Atmosphere 2020, 11(10), 1100; https://doi.org/10.3390/atmos11101100 - 14 Oct 2020

Cited by 2 | Viewed by 1773

Abstract

Our understanding of Central Asian historical streamflow variability is still limited because of short instrumental hydrologcial records. Based on tree-ring cores collected from three sampling sites in Kaiken River basin near Tien Shan, a regional tree-ring width chronology were developed. The correlation analysis [...] Read more.

Our understanding of Central Asian historical streamflow variability is still limited because of short instrumental hydrologcial records. Based on tree-ring cores collected from three sampling sites in Kaiken River basin near Tien Shan, a regional tree-ring width chronology were developed. The correlation analysis showed that the runoff of Kaiken River from previous August to current June was significantly correlated with the regional chronology, and the high correlation coefficient was 0.661 (P < 0.01). Based on the regional chronology, the August-June runoff of Kaiken River has been reconstructed over the past 422 year, and it accounted for 43.7% of actual runoff variance during the common period 1983–2013. The reconstruction model is reliable, and the trend of observed and reconstructed data is relatively consistent. The results of multi-taper spectral analysis for the runoff reconstruction indicated some remarkable cycles for the past 422 years; the 11.5-year cycles correspond to the solar cycle and is found widely in runoff reconstructions in Central Asia. This may imply a solar influence on the hydroclimate variations of Tien Shan. The runoff reconstruction of Kaiken River compares well with runoff reconstructions the Urumqi River and Manas River, and implies that there is a common driving factor for the runoff in central Tien Shan, China. The analysis of linkages between climate variation and the runoff reconstruction of Kaiken River shows that there is a relationship between extremes in runoff variation and abnormal atmospheric circulations. Our 422-year steamflow reconstruction provides long-term perspective on current and 20th century hydrological events in central Tien Shan, is useful for aids sustainable water management and addresses regional climate change challenges. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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13 pages, 5620 KiB

Open AccessArticle

The Potential of Using Tree-Ring Chronology from the Southern Coast of Korea to Reconstruct the Climate of Subtropical Western North Pacific: A Pilot Study

by Min-Seok Kim, Peng Zhang, Sung-Ho Woo, Youngdae Koh, Hans W. Linderholm and Jee-Hoon Jeong

Atmosphere 2020, 11(10), 1082; https://doi.org/10.3390/atmos11101082 - 11 Oct 2020

Viewed by 2228

Abstract

Tree-ring width (TRW) chronologies have successfully been used as climate proxies to infer climate variabilities over the past hundreds to thousands of years worldwide beyond observational records. However, these data are scarce over parts of subtropical East Asia, and especially over the Korean [...] Read more.

Tree-ring width (TRW) chronologies have successfully been used as climate proxies to infer climate variabilities over the past hundreds to thousands of years worldwide beyond observational records. However, these data are scarce over parts of subtropical East Asia, and especially over the Korean Peninsula. In this pilot study, Korean red pine (Pinus densiflora Siebold and Zucc.) TRW chronologies from Mt. Mudeung and Mt. Wolchul, South Korea, were developed, and their local- to large-scale climatic responses were investigated. Mt. Mudeung TRW had a positive association with local temperature in the preceding December and April. Mt. Wolchul TRW had a positive association with local temperature in the preceding December and most of the early summer to autumn months, and with local precipitation in February and October. On a large scale, both TRWs retained meaningful temperature and monsoon precipitation signals over East Asia and sea surface temperature signals over the Western North Pacific. The results suggest that the subtropical trees from South Korea can be used to infer past long-term climate variability at both local and large scales over East Asia and the Western North Pacific, such as the East Asian summer monsoon, the Kuroshio Current, the Western North Pacific Subtropical High, and El Niño–Southern Oscillation. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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13 pages, 3767 KiB

Open AccessArticle

Moisture Variability in the East Pearl River Basin since 1894 CE Inferred from Tree Ring Records

by Teng Li, Jinbao Li, Tsun Fung Au and David D. Zhang

Atmosphere 2020, 11(10), 1075; https://doi.org/10.3390/atmos11101075 - 09 Oct 2020

Cited by 4 | Viewed by 2228

Abstract

Short-term climate change in South China has been extensively studied based on meteorological or hydrological records. However, tree ring-based long-term climate change research is rare, especially in the Pearl River basin, owing to the difficulty in finding old-aged trees. Here, we present a [...] Read more.

Short-term climate change in South China has been extensively studied based on meteorological or hydrological records. However, tree ring-based long-term climate change research is rare, especially in the Pearl River basin, owing to the difficulty in finding old-aged trees. Here, we present a 200-year tree ring width chronology of Pinus kwangtungensis in the east Pearl River basin with reliable coverage from 1894 to 2014. Based on the significant climate-growth relationship between tree growth and annual self-calibrating Palmer drought severity index (scPDSI) from previous May to current April, the pMay-cApr scPDSI was reconstructed for the period 1894–2014. The reconstruction reveals four dry periods during 1899–1924, 1962–1974, 1988–1994, and 2003–2014, and four wet periods during 1894–1898, 1925–1961, 1975–1987, and 1995–2002. Significant spatial correlations between the reconstructed scPDSI and the Climatic Research Unit (CRU) gridded scPDSI indicate that our reconstruction can effectively represent regional moisture variability in the Pearl River basin. Spatial correlations with global sea surface temperatures (SSTs) show that our reconstruction is negatively correlated with northern and western Pacific SSTs while positively correlated with eastern Pacific SSTs, suggesting that SST variability in these domains strongly affects moisture change in the Pearl River basin. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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14 pages, 4479 KiB

Open AccessArticle

Dendrochronological Reconstruction of June Drought (PDSI) from 1731–2016 for the Western Mongolian Plateau

by Liang Shi, Guangxin Li, Hongyan Liu, Jeffery P. Dech, Mei Zhou, Pengwu Zhao and Zhong Ren

Atmosphere 2020, 11(8), 839; https://doi.org/10.3390/atmos11080839 - 11 Aug 2020

Cited by 3 | Viewed by 2730

Abstract

Droughts are a recurrent phenomenon in the semiarid forest-steppe ecotone of Mongolia with negative consequences for tree growth and agricultural management. In order to better cope with the uncertainty of a changing climate, the study of historical drought and its effects on forests [...] Read more.

Droughts are a recurrent phenomenon in the semiarid forest-steppe ecotone of Mongolia with negative consequences for tree growth and agricultural management. In order to better cope with the uncertainty of a changing climate, the study of historical drought and its effects on forests could provide useful insights into ecosystem responses to climate variability. Siberian larch (Larix sibirica) is a dominant tree species in Western Mongolia that provides a valuable source of proxy data in the form of annual rings. We used dendrochronological techniques to establish a standard master chronology and analyze the relationship between annual ring widths and climatic factors. Correlation analyses revealed that the strongest associations of tree-ring index (TRI) values for the master chronology to direct climate variables were June temperature (r = −0.36, p < 0.01) and precipitation (r = 0.39, p < 0.01). The master chronology was strongly correlated to Palmer Drought Severity Index (PDSI) for June (r = 0.606, p < 0.001), and this variable (PDSI_Jun) was chosen for reconstruction. A simple linear regression of PDSI_Jun based on TRI explained 35.4% of the total variance for the period 1965–2016 and based on this model the PDSI_Jun changes from 1731–2016 were reconstructed. Split–sample calibration–verification tests were conducted to evaluate the quality of the model used for climate reconstruction. In the past 286 years, the number of non-drought years (PDSI > 0) was low, with a frequency of only 14.1% of the total reconstruction years. Extreme drought (PDSI_Jun < −2.70) occurred frequently in the 19th and early and late 20th centuries. Multi-taper method (MTM) spectra and wavelet analysis showed that the reconstructed PDSI series had high and low frequency periods (2.4–3.3 and 85–92 years). Our findings provide an understanding of the drought history of the semiarid forest-steppe ecotone of western Mongolia. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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14 pages, 3665 KiB

Open AccessArticle

Reconstructing Summer Precipitation with MXD Data from Pinus sylvestris Growing in the Stockholm Archipelago

by Eva Rocha, Björn E. Gunnarson and Steffen Holzkämper

Atmosphere 2020, 11(8), 790; https://doi.org/10.3390/atmos11080790 - 27 Jul 2020

Cited by 10 | Viewed by 2726

Abstract

Maximum latewood density (MXD) chronologies have been widely used to reconstruct summer temperature variations. Precipitation signals inferred from MXD data are, however, rather scarce. In this study, we assess the potential of using MXD data derived from Scots pine (Pinus sylvestris L. [...] Read more.

Maximum latewood density (MXD) chronologies have been widely used to reconstruct summer temperature variations. Precipitation signals inferred from MXD data are, however, rather scarce. In this study, we assess the potential of using MXD data derived from Scots pine (Pinus sylvestris L.) growing in the Stockholm archipelago (Sweden) to reconstruct past precipitation variability. In this area, slow-growing pine trees emerge on flat plateaus of bedrock outcrops with thin or absent soil layers and are, therefore, sensitive to moisture variability. A 268-year-long MXD chronology was produced, and climate–growth relationships show a significant and robust correlation with May–July precipitation (P_MJJr = 0.64, p < 0.01). The MXD based May–July precipitation reconstruction covers the period 1750–2018 CE and explains 41% of the variance (r²) of the observed precipitation (1985–2018). The reconstruction suggests that the region has experienced more pluvial phases than drought conditions since the 1750s. The latter half of the 18th century was the wettest and the first half of the 19th century the driest. Climate analysis of “light rings” (LR), latewood layers of extreme low-density cells, finds their occurrence often coincides with significantly dry (<41 mm precipitation) and warmer (1–2 °C above average temperature), May–July conditions. Our analysis suggests that these extremes may be triggered by the summer North Atlantic Oscillation (SNAO). Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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17 pages, 4884 KiB

Open AccessFeature PaperArticle

High-Resolution Temperature Variability Reconstructed from Black Pine Tree Ring Densities in Southern Spain

by Jan Esper, Claudia Hartl, Ernesto Tejedor, Martin de Luis, Björn Günther and Ulf Büntgen

Atmosphere 2020, 11(7), 748; https://doi.org/10.3390/atmos11070748 - 15 Jul 2020

Cited by 9 | Viewed by 5674

Abstract

The presence of an ancient, high-elevation pine forest in the Natural Park of Sierras de Cazorla in southern Spain, including some trees reaching >700 years, stimulated efforts to develop high-resolution temperature reconstructions in an otherwise drought-dominated region. Here, we present a reconstruction of [...] Read more.

The presence of an ancient, high-elevation pine forest in the Natural Park of Sierras de Cazorla in southern Spain, including some trees reaching >700 years, stimulated efforts to develop high-resolution temperature reconstructions in an otherwise drought-dominated region. Here, we present a reconstruction of spring and fall temperature variability derived from black pine tree ring maximum densities reaching back to 1350 Coefficient of Efficiency (CE). The reconstruction is accompanied by large uncertainties resulting from low interseries correlations among the single trees and a limited number of reliable instrumental stations in the study region. The reconstructed temperature history reveals warm conditions during the early 16th and 19th centuries that were of similar magnitude to the warm temperatures recorded since the late 20th century. A sharp transition from cold conditions in the late 18th century (t_1781–1810 = −1.15 °C ± 0.64 °C) to warm conditions in the early 19th century (t_1818–1847 = −0.06 °C ± 0.49 °C) is centered around the 1815 Tambora eruption (t₁₈₁₆ = −2.1 °C ± 0.55 °C). The new reconstruction from southern Spain correlates significantly with high-resolution temperature histories from the Pyrenees located ~600 km north of the Cazorla Natural Park, an association that is temporally stable over the past 650 years (r_1350–2005 > 0.3, p < 0.0001) and particularly strong in the high-frequency domain (r_HF > 0.4). Yet, only a few of the reconstructed cold extremes (1453, 1601, 1816) coincide with large volcanic eruptions, suggesting that the severe cooling events in southern Spain are controlled by internal dynamics rather than external (volcanic) forcing. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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11 pages, 3250 KiB

Open AccessArticle

Summer Monsoon Season Streamflow Variations in the Middle Yellow River since 1570 CE Inferred from Tree Rings of Pinus tabulaeformis

by Feng Chen, Magdalena Opała-Owczarek, Piotr Owczarek and Youping Chen

Atmosphere 2020, 11(7), 717; https://doi.org/10.3390/atmos11070717 - 06 Jul 2020

Cited by 13 | Viewed by 2740

Abstract

This study investigates the potential reconstruction of summer monsoon season streamflow variations in the middle reaches of the Yellow River from tree rings in the Qinling Mountains. The regional chronology is significantly positively correlated with the July–October streamflow of the middle Yellow River [...] Read more.

This study investigates the potential reconstruction of summer monsoon season streamflow variations in the middle reaches of the Yellow River from tree rings in the Qinling Mountains. The regional chronology is significantly positively correlated with the July–October streamflow of the middle Yellow River from 1919 to 1949, and the derived reconstruction explains 36.4% of the actual streamflow variance during this period. High streamflows occurred during 1644–1757, 1795–1806, 1818–1833, 1882–1900, 1909–1920 and 1933–1963. Low streamflows occurred during 1570–1643, 1758–1794, 1807–1817, 1834–1868, 1921–1932 and 1964–2012. High and low streamflow intervals also correspond well to the East Asian summer monsoon (EASM) intensity. Some negative correlations of our streamflow reconstruction with Indo-Pacific sea surface temperature (SST) also suggest the linkage of regional streamflow changes to the Asian summer monsoon circulation. Although climate change has some important effects on the variation in streamflow, anthropogenic activities are the primary factors mediating the flow cessation of the Yellow River, based on streamflow reconstruction. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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13 pages, 2903 KiB

Open AccessArticle

Retrospective Analysis of Tree Decline Based on Intrinsic Water-Use Efficiency in Semi-Arid Areas of North China

by Weiwei Lu, Xinxiao Yu and Guodong Jia

Atmosphere 2020, 11(6), 577; https://doi.org/10.3390/atmos11060577 - 01 Jun 2020

Cited by 3 | Viewed by 2027

Abstract

Long-term tree growth is significantly affected by climate change, which have become a global concern. Tree-ring width and isotopic information can show how trees respond to climate change on a long-term scale and reveal some phenomena of tree decline or death. In this [...] Read more.

Long-term tree growth is significantly affected by climate change, which have become a global concern. Tree-ring width and isotopic information can show how trees respond to climate change on a long-term scale and reveal some phenomena of tree decline or death. In this study, we used isotopic techniques and investigated annual changes in carbon isotope composition and tree-ring width of Populus simonii Carr. in Zhangbei, as well as trends in tree-ring carbon discrimination (Δ¹³C) and iWUE in normal, mildly declining and severely declining trees, in order to make a retrospective analysis and further understand the process of tree decline. We found that there were significant differences (p < 0.01 **) in δ¹³C, Δ¹³C, c_i and iWUE at different decline stages, meaning that the δ¹³C and iWUE could be new indicators of tree health. The iWUE of all groups increased significantly, while the growth rate of declined P. simonii was much higher than that of normal growth P. simonii. According to the analysis, there may be a threshold of iWUE for healthy trees, which once the threshold value is exceeded, it indicates that trees are resistant to adversity and their growth is under stress. Similarly, the changing trend of BAI supports our conclusion with its changes showed that tree growth became slower and slower as degradation progressed. iWUE inferred from tree-ring stable carbon isotope composition is a strong modulator of adaptation capacity in response to environmental stressors under climate change. Elevated annual temperatures and increased groundwater depth are all contributing to the decline of P. simonii in north China. Full article

(This article belongs to the Special Issue Past Climate Reconstructed from Tree Rings)

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