| 1. |
- Bai, M. W., et al.
(författare)
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Different responses of the radial growth of the planted and natural forests to climate change in humid subtropical China
- 2020
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Ingår i: Geografiska Annaler Series a-Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 102:3, s. 235-246
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Tidskriftsartikel (refereegranskat)abstract
- China holds the world's largest area of planted forests, which play a crucial role in mitigating climate change. Knowledge gaps remain on the responses of the growth of planted forests to climate changes in China, particularly for their long-term changes. This study compared the long-term tree-ring growth patterns and their responses to climate between planted and natural forests. We developed four chronologies from two typical conifer species ofPinus massonianaandCunninghamia lanceolatafrom planted and natural forests in humid subtropical China. One chronology is to our knowledge the longest chronology from planted forests in China spanning since 1944. Tree growths of both natural and planted forests are generally limited by summer drought due to the hot and dry summer in this area. In general, tree rings of the natural forests are more sensitive to climate than planted forests as indicated by higher inter-series correlations, which agree with previous studies. The natural forests are more drought sensitive wheareas the planted forests are relatively more limited by temperature. TheC. lanceolataforests showed more significant correlations with the accumulated drought thanP. massonianafor both the natural and planted forests.
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| 2. |
- Chen, D., et al.
(författare)
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A tree-ring delta O-18 based reconstruction of East Asia summer monsoon over the past two centuries
- 2020
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:6
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Tidskriftsartikel (refereegranskat)abstract
- The East Asian summer monsoon (EASM) exhibits considerable decadal variations since the late 20th century. Efforts to examine long-term behaviors and dynamics of the EASM are impeded largely due to the shortness of instrumental meteorological records. So far, reconstructions of the EASM with annual resolution from its core regions remain limited. We conduct the first 200-year robust EASM reconstruction based on tree-ring cellulose delta O-18 records derived from Pinus massoniana trees growing in the middle Yangtze River basin, one of the core EASM areas. The delta O-18 chronology accounts for 46.2% of the actual variation in an index of the EASM from 1948 to 2014. The reconstructed EASM indicates that the monsoon intensity was below average before the 1950s, peaked in the 1950s-1970s, and then began to decline. The reconstructed EASM is negatively correlated with the El Nino-Southern Oscillation (ENSO), but this teleconnection is dynamic through time, i.e. enhanced (reduced) ENSO variability coheres with strong (weak) EASM-ENSO connections. In addition, despite high ENSO variability since the 1980s, the EASM-ENSO relationship weakened possibly due to anthropogenic impact, particularly aerosol emissions.
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| 3. |
- Chen, Shiyin, et al.
(författare)
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Tree-ring recorded variations of 10 heavy metal elements over the past 168 years in southeastern China
- 2021
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Ingår i: Elementa: Science of the Anthropocene. - : University of California Press. - 2325-1026. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Heavy metal pollution is a serious concern in the urban area of China. Understanding metal pollution history is crucial for setting up appropriate measures for pollution control. Herein, we report a record of concentrations of 10 heavy metals (Fe, Mn, Cu, Zn, Ni, Cr, Cd, Pb, Co, and Sr) in Pinus massoniana tree rings from Fuzhou City over the past 168 years, which represents the longest tree-ring chronology of heavy metals in China. The studied metals displayed contrasting distribution patterns. Among them, Mn and Sr showed the strongest migration trend with peak concentrations at the pith. Co, Cd, and Pb also showed distinctively high concentrations near the boundary between heartwood and sapwood. Ni, Cu, Cr, and Fe showed an increasing trend possibly due to migration toward bark caused by physiological activities and increasing tourism activities and traffic pollution. The other elements (Cr, Fe, and Zn) with low migration revealed the historical pollution possibly discharged by the Fuzhou Shipping Bureau and other anthropogenic activities. Strong correlations between Cu content and temperature were found, which provides an alternative tree-ring proxy for climate reconstruction. This study provides a long-term perspective of the joint impacts of physiological, environmental, and climatological factors on the concentrations of heavy metals in southeastern China.
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| 4. |
- Fan, H., et al.
(författare)
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Different moisture regimes during the last 150 years inferred from a tree-ring δ18O network over the transitional zone of the Asian summer monsoon
- 2022
-
Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 613
-
Tidskriftsartikel (refereegranskat)abstract
- The East Asian summer monsoon (EASM) and Indian summer monsoon (ISM) are two interactive climate systems dominating the moisture variability of Monsoon Asia. However, ISM-EASM interactions and their effects on regional moisture dynamics remain unclear. This study investigated the spatiotemporal characteristics of monsoon-related hydroclimate variability by establishing a new tree-ring oxygen isotope ratio (δ18Otree) network of eight δ18Otree records covering the last 150 years in southern China, which differs from previous studies that used data from individual sites. The δ18Otree chronologies were found to be sensitive to regional hydroclimatic changes during the monsoon season. The δ18Otree network indicated an east–west clustering pattern in the ISM-EASM transitional zone, which demonstrates an asynchrony in δ18Otree variability in the west and east of this region. Regional variability of the west and east δ18Otree modes reflected the different moisture signals, as indicated by their significant correlations with modern observations and paleo-δ18O records in disparate upstream regions of moisture transport (the Indochina Peninsula and Southeast China). This finding was confirmed by the east–west distinct pattern of spatial isotopic depletion of monsoon rainfall that originates from coastal areas of tropical oceans (Bay of Bengal and South China Sea) to the study area, as well as the consistent present-day pattern of atmospheric vapor transport during the monsoon season. In addition, the west and east modes exhibited stronger associations with ISM variability, whereas the east–west δ18Otree gradient captured the EASM-related hydroclimatic signal, suggesting that summer moisture variability in the ISM-EASM transitional zone was regulated more by ISM than by EASM during the last 150 years. The relationships between δ18Otree and large-scale ocean–atmosphere interaction modes revealed that the El Niño-Southern Oscillation (ENSO) dominantly modulates δ18Otree variability across southern China. © 2022 Elsevier B.V.
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| 5. |
- Fan, H. W., et al.
(författare)
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Different moisture regimes during the last 150 years inferred from a tree-ring delta O-18 network over the transitional zone of the Asian summer monsoon
- 2022
-
Ingår i: Journal of Hydrology. - 0022-1694. ; 613
-
Tidskriftsartikel (refereegranskat)abstract
- The East Asian summer monsoon (EASM) and Indian summer monsoon (ISM) are two interactive climate systems dominating the moisture variability of Monsoon Asia. However, ISM-EASM interactions and their effects on regional moisture dynamics remain unclear. This study investigated the spatiotemporal characteristics of monsoon-related hydroclimate variability by establishing a new tree-ring oxygen isotope ratio (delta O-18(tree)) network of eight delta O-18(tree) records covering the last 150 years in southern China, which differs from previous studies that used data from individual sites. The delta O-18(tree) chronologies were found to be sensitive to regional hydroclimatic changes during the monsoon season. The delta O-18(tree) network indicated an east-west clustering pattern in the ISM-EASM transitional zone, which demonstrates an asynchrony in d18Otree variability in the west and east of this region. Regional variability of the west and east delta O-18(tree) modes reflected the different moisture signals, as indicated by their significant correlations with modern observations and paleo-delta O-18 records in disparate upstream regions of moisture transport (the Indochina Peninsula and Southeast China). This finding was confirmed by the east-west distinct pattern of spatial isotopic depletion of monsoon rainfall that originates from coastal areas of tropical oceans (Bay of Bengal and South China Sea) to the study area, as well as the consistent present-day pattern of atmospheric vapor transport during the monsoon season. In addition, the west and east modes exhibited stronger associations with ISM variability, whereas the east-west delta O-18(tree) gradient captured the EASM-related hydroclimatic signal, suggesting that summer moisture variability in the ISM-EASM transitional zone was regulated more by ISM than by EASM during the last 150 years. The relationships between delta O-18(tree) and large-scale ocean-atmosphere interaction modes revealed that the El Nino-Southern Oscillation (ENSO) dominantly modulates delta O-18(tree) variability across southern China.
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| 6. |
- Fan, H. W., et al.
(författare)
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Spatial synchrony in delta O-18 time-series from a tree-ring network are driven by synchronous hydroclimate variability in the transitional zone of the Asian summer monsoon
- 2021
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923. ; 311
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Tidskriftsartikel (refereegranskat)abstract
- Owing to the increased need to assess global forest behavior under changing climatic conditions within a longterm context, spatial coherence in tree-ring records is of widespread interest. Spatial networks of tree growth have been widely discussed from regional to global scales, but few studies have reported stable oxygen isotopes in networks of tree rings (delta O-18(tree)), thus impeding a comprehensive hydroclimatic interpretation of delta O-18(tree) records over large spatial scales, i.e., isoscapes. In this study, a network of four annually resolved delta O-18(tree) chronologies (1805-2016) was developed for Southwest China, the transitional zone of the Asian summer monsoon, to test spatial coherence in delta O-18(tree) variations and to explore the climatic factors driving synchrony at different spatial scales. The quantitative analyses show that the four chronologies exhibit consistent annual variations, with the first principal component (PC1) accounting for 70% of the total variance, which uniformly respond to local relative humidity (RH) and precipitation delta O-18 during the monsoon season. This confirms the spatial coherence in delta O-18(tree) records. Furthermore, significant inter-site correlations of local RH and precipitation delta O-18 are also detected, revealing that it is the regionally homogeneous year-to-year variations in the hydroclimate that should be responsible for spatial coherence. For a larger spatial perspective, spatial correlation analyses reveal that the most prominent correlations between delta O-18(tree) and hydroclimate fields occur in the Indochina Peninsula, in which delta O-18(tree) changes are synchronized with those in Southwest China and the synchrony temporally varies with the Indian summer monsoon (ISM) intensity, indicating that coherent delta O-18(tree) variations are linked to ISM-related moisture transport. In addition, delta O-18(tree) records have shown strong in-phase relationships with the natural variabilities of the ISM and El Nino-Southern Oscillation (ENSO) across interannual and interdecadal timescales over the last 150 years, suggesting that spatial coherence in delta O-18(tree) records can be utilized to reflect the long-term history of large-scale atmospheric circulation.
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| 7. |
- Fang, Keyan, et al.
(författare)
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An interdecadal climate dipole between Northeast Asia and Antarctica over the past five centuries
- 2019
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 52:1/2, s. 765-775
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Springer-Verlag GmbH Germany, part of Springer Nature Climate models emphasize the need to investigate inter-hemispheric climatic interactions. However, these models often underestimate the inter-hemispheric differences in climate change. With the wide application of reanalysis data since 1948, we identified a dipole pattern between the geopotential heights (GPHs) in Northeast Asia and Antarctica on the interdecadal scale in boreal summer. This Northeast Asia/Antarctica (NAA) dipole pattern is not conspicuous on the interannual scale, probably in that the interannual inter-hemispheric climate interaction is masked by strong interannual signals in the tropics associated with the El Niño-Southern Oscillation (ENSO). Unfortunately, the instrumental records are not sufficiently long-lasting to detect the interdecadal variability of the NAA. We thus reconstructed GPHs since 1565, making using the proxy records mostly from tree rings in Northeast Asia and ice cores from Antarctica. The strength of the NAA is time-varying and it is most conspicuous in the eighteenth century and after the late twentieth century. The strength of the NAA matches well with the variations of the solar radiation and tends to increase in along with its enhancement. In boreal summer, enhanced heating associated with high solar radiation in the Northern Hemisphere drives more air masses from the South to the North. This inter-hemispheric interaction is particularly strong in East Asia as a result of the Asian summer monsoon. Northeast Asia and Antarctica appear to be the key regions responsible for inter-hemispheric interactions on the interdecadal scale in boreal summer since they are respectively located at the front and the end of this inter-hemispheric trajectory.
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| 8. |
- Fang, Keyan, et al.
(författare)
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Climate of the late Pleistocene and early Holocene in coastal South China inferred from submerged wood samples
- 2017
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Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182. ; 447, s. 111-117
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Tidskriftsartikel (refereegranskat)abstract
- Tree-ring variability of submerged wood specimens in coastal areas provides important clues about sea level change and climate variability of the past. We dated submerged wood samples from coastal Fujian province in China using the radiocarbon methods and investigated their tree-ring variability. The submerged wood samples from the Shenhu Bay that date to the early Holocene (similar to 8000 calibrated years B.P.) may be related to the rise of the sea level after the Last Glacial Maximum (LGM). The submerged wood samples from the Qianhu Bay site dated to the Marine Isotope Stage 3 (MIS 3) (> 40,000 calibrated years B. P.). Most of the submerged wood samples are from coniferous trees with frequent branching tree rings. Frequent branching tree rings in this region are mostly found from the currently endangered coniferous species with narrow ecological amplitude at humid sites. Tree rings of the submerged sample show conspicuous interdecadal variability (similar to 20 years) than interannual variations, which differs from modern tree rings of nearby regions which have stronger interannual and multi-decadal variability. Our study highlights the potential to use submerged samples of coastal Southeast China for paleoclimate studies.
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| 9. |
- Fang, Keyan, et al.
(författare)
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Co-varying temperatures at 200hpa over the Earth’s three poles
- 2021
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Ingår i: Science China Earth sciences. - : Springer Science and Business Media LLC. - 1674-7313 .- 1869-1897. ; 64, s. 340-350
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Tidskriftsartikel (refereegranskat)abstract
- The Earth’s three poles, the North Pole, South Pole, and Third Pole (i.e., the Tibetan Plateau and its surroundings), hold the largest amount of fresh water on Earth as glaciers, sea ice, and snow. They are sensitive to climate change. However, the linkages between climate variations of the three poles, particularly between the South Pole and Third Pole, remain largely unknown. The temperatures at 200 hPa over the three poles are the highest in the summer and are less affected by surface conditions, which could reflect large-scale dynamic linkages. Temperatures at 200 hPa peak the three poles during their respective hemispheric summer and exhibit in-phase variations on interdecadal timescales (10-100 years). The 200 hPa temperatures over the North Pole and South Pole were significantly correlated with the Brewer-Dobson circulation (BDC), which transports stratospheric ozone poleward, heating the air at 200 hPa. Tropopause warming over the Third Pole was found to enhance the poleward BDC, particularly to the South Pole, linking the Third Pole’s climate to the other two poles. Additionally, the Interdecadal Pacific Oscillation (IPO) also exhibits links with the 200 hPa temperatures of the three poles.
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| 10. |
- Fang, Keyan, et al.
(författare)
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Drought variation of western Chinese Loess Plateau since 1568 and its linkages with droughts in western North America
- 2017
-
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 49:11-12, s. 3839-3850
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Tidskriftsartikel (refereegranskat)abstract
- © 2017, Springer-Verlag Berlin Heidelberg. Understanding long-term drought variations in the past can help to evaluate ongoing and future hydroclimate change in the arid western Chinese Loess Plateau (WCLP), a region with increasing demand for water resources due to the increasing population and socioeconomic activities. Here we present a new tree-ring chronology inform the WCLP, which shows coherent interannual variations with tree-ring chronologies from 7 neighboring areas across the WCLP, suggesting a common regional climate control over tree growth. However, considerable differences are observed among their interdecadal variations, which are likely due to growth disturbances at interdecadal timescales. To deal with this issue, we use a frequency based method to develop a composite tree-ring chronology from 401 tree-ring series from these 8 sites, which shows more pronounced interdecadal variability than a chronology developed using traditional methods. The composite tree-ring chronology is used to reconstruct the annual precipitation from previous August to current July from 1568 to 2012, extending about 50 years longer than the previous longest tree-ring reconstruction from the region. The driest epoch of our reconstruction is found in the 1920s–1930s, which matches well with droughts recorded in historical documents. Over the past four centuries, a strong resemblance between drought variability in the WCLP and western North America (WNA) is evident on multidecadal timescales, but this relationship breaks down on timescales shorter than about 50 years.
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| 11. |
- Fang, Keyan, et al.
(författare)
-
ENSO modulates wildfire activity in China
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- China is a key region for understanding fire activity and the drivers of its variability under strict fire suppression policies. Here, we present a detailed fire occurrence dataset for China, the Wildfire Atlas of China (WFAC; 2005-2018), based on continuous monitoring from multiple satellites and calibrated against field observations. We find that wildfires across China mostly occur in the winter season from January to April and those fire occurrences generally show a decreasing trend after reaching a peak in 2007. Most wildfires (84%) occur in subtropical China, with two distinct clusters in its southwestern and southeastern parts. In southeastern China, wildfires are mainly promoted by low precipitation and high diurnal temperature ranges, the combination of which dries out plant tissue and fuel. In southwestern China, wildfires are mainly promoted by warm conditions that enhance evaporation from litter and dormant plant tissues. We further find a fire occurrence dipole between southwestern and southeastern China that is modulated by the El Nino-Southern Oscillation (ENSO). Fire activity in China and its associations with climate are not well quantified at a local scale. Here, the authors present a detailed fire occurrence dataset for China and find a dipole fire pattern between southwestern and southeastern China that is modulated by the El Nino-Southern Oscillation (ENSO).
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| 12. |
- Fang, Keyan, et al.
(författare)
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How robust are Holocene treeline simulations? A model-data comparison in the European Arctic treeline region
- 2013
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Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 28:6, s. 595-604
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Tidskriftsartikel (refereegranskat)abstract
- Treeline encroachments and retractions can provide global-scale feedbacks to the climate system, and treeline dynamics are therefore of great relevance for understanding global climate variability. To assess the accuracy of long-term treeline simulations based on the generalized dynamic vegetation model LPJ-GUESS, we simulate European Arctic treeline dynamics over the past 9000 years and compare the results with fossil-based reconstructions. The results show that while LPJ-GUESS is limited in its ability to capture species-level current treeline patterns and past dynamics, it is generally able to realistically simulate the Holocene coniferous treeline changes with a cutoff biomass carbon of 2 C kg m(-2). The model captures the northward expansion of the boreal forest during the mid Holocene and correctly simulates a treeline retreat in response to climate cooling during the last 3000 years. However, there are data-simulation disagreements particularly during the early Holocene, which mainly result from the differences between the two palaeoclimate model scenarios used to drive the simulations. We suggest that the spatial accuracy of the model could be improved by incorporating the influence of topographic features, the extent of the Arctic peatlands, the tree species life-history characteristics, microclimate and other ecological factors. Copyright (c) 2013 John Wiley & Sons, Ltd.
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| 13. |
- Fang, Keyan, et al.
(författare)
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Interdecadal modulation of the Atlantic Multi-decadal Oscillation (AMO) on southwest China’s temperature over the past 250 years
- 2019
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 52:3/4, s. 2055-2065
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Springer-Verlag GmbH Germany, part of Springer Nature The temperature gradient between southwestern China and Indian Ocean is one key driver of the Indian Summer Monsoon, suggesting the necessity to understand temperature variability in southwestern China. Contrary to the general warming experienced in most of China, a few regions in southwestern China have undergone a cooling trend since the 1950s. To place this cooling trend in a historical context, this study develops an Abies fabri tree-ring width chronology in the Sichuan Basin, the most populated region in southwest China. The chronology spans from 1590 to 2012, with its reliable portion from 1758 to 2012, by far the longest in the Sichuan Basin. To better extract regional climate signals encoded in tree rings with strong local disturbances, we incorporate climate signals of nearby tree-ring chronologies to generate a large-scale tree-ring chronology (LSC). The LSC shows higher correlations with temperature near the sampling site on Mount Emei and sea surface temperatures of the northern Atlantic Ocean than chronologies developed using traditional methods. The highest correlations between the LSC and temperature are found from current February to July in the Sichuan Basin for the period 1901–1950 (r = 0.70), with a sharp decrease afterwards. Interdecadal variations of the LSC match well with Atlantic Multi-decadal Oscillation reconstructions, except for the late nineteenth century and after ~ 1980s. This study provides evidence that southwest China is a transitional region both affected by the interdecadal temperature variations of the northern Atlantic and Asian areas, although their influences weakened in recent possible due to enhanced human activities.
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| 14. |
- Fang, Keyan, et al.
(författare)
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Oceanic and atmospheric modes in the Pacific and Atlantic Oceans since the Little Ice Age (LIA): Towards a synthesis
- 2019
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 215, s. 293-307
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the variability of the oceanic and atmospheric modes from the Little Ice Age (LIA,similar to 1250 - 1850) to the present can help evaluate their behaviors under future warming scenarios. Numerous proxy-based reconstructions of the oceanic and atmospheric modes were presented. It is highly needed for a synthesis study to evaluate the existing reconstructions of the dominant oceanic and atmospheric modes since the LIA. We found that the El Nino-Southern Oscillation (ENSO) reconstructions are only robust on interannual and interdecadal scales, while the reconstructed Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO) are robust on multi-decadal (50-100 years) timescales. We generated synthesized ENSO, PDO and AMO reconstructions as the average of the existing reconstructions on the most suitable timescales identified using timescale dependent correlation methods. In the 20th century, the interannual variability and periodicity of the ENSO and the multi-decadal periodicity of the PDO and AMO were most pronounced. The ENSO shows the strongest multi-decadal periodicity from mid-18th century onwards, while the multi-decadal periodicity of the PDO and AMO was particularly low in the 18th century. Multi-decadal variations of the AMO showed a prompt and positive response to solar irradiation, while the ENSO showed a lagged and negative response to solar irradiation from the 18th century to the present. (C) 2019 Elsevier Ltd. All rights reserved.
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| 15. |
- Fang, Keyan, et al.
(författare)
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Synchronous multi-decadal climate variability of the whole Pacific areas revealed in tree rings since 1567
- 2018
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 13:2
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Tidskriftsartikel (refereegranskat)abstract
- Oceanic and atmospheric patterns play a crucial role on modulating climate variability from interannual to multi-decadal timescales by, causing large-scale co-varying climate changes. The brevity of the existing instrumental records hinders the ability to recognize climate patterns before the industrial era, which can be alleviated by using proxies. Unfortunately, proxy based reconstructions of oceanic and atmospheric modes of the past millennia often have modest agreements with each other before the instrumental period, raising questions about the robustness of the reconstructions. To ensure the stability of climate signals in proxy data through time, we first identified tree-ring datasets from distant regions containing coherent variations in Asia and North America, and then interpreted their climate information. We found the multi-decadal covarying climate patterns of the middle and high latitudinal regions around the northern Pacific Ocean agreed quite well with the climate reconstructions of the tropical and southern Pacific areas. This indicates a synchronous variability at multi-decadal timescale of the past 430 years for the entire Pacific Ocean. This pattern is closely linked to the dominant mode of the Pacific sea surface temperature (SST) after removing the warming trend. This Pacific multi-decadal SST variability resembles the Interdecadal Pacific Oscillation (IPO).
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| 16. |
- Fang, Keyan, et al.
(författare)
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Synchronous spring precipitation in Southeastern China and Bengal: a potential indicator for the Indian summer monsoon?
- 2024
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Ingår i: ENVIRONMENTAL RESEARCH LETTERS. - 1748-9326. ; 19:10
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Tidskriftsartikel (refereegranskat)abstract
- Spring precipitation in southeastern China and Bengal, occurring during the transitional phase from winter to summer monsoons, serves as a critical window into the dynamics of large-scale circulations and the subsequent summer monsoon. While many studies have analyzed spring precipitation in southeastern China and Bengal, their interconnections and implications for the summer monsoon have remained relatively under explored. We utilized the Empirical Orthogonal Function of spring precipitation to reveal Synchronous Spring Precipitation (SSP) in southeastern China and Bengal. This synchronicity is bridged by the East Asian Subtropical Jet (EASJ) that extends from Bengal to southeastern China. The EASJ was predominantly correlated with precipitation in southeastern China prior to the 1990s, while it developed a more profound connection with precipitation in Bengal after the 1990s. Notably, SSP anomalies occurred during the developing phase of the El Ni & ntilde;o-Southern Oscillation (ENSO). The predictive capacity of SSP for the Indian summer monsoon (ISM) amplifies during periods of the intensified SSP-ENSO correlations and positive phase of the North Pacific Meridional Mode. Tree-ring based reconstructions spanning the past two centuries further corroborate the persistent linkages among the SSP, ISM, and ENSO. Our research sheds light on the intricate interplay of these factors and their significance in understanding and predicting the monsoon dynamics in the region.
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| 17. |
- Fang, Keyan, et al.
(författare)
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The potential to use variations in tree-ring geometric center to estimate past wind speed change
- 2022
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Ingår i: Natural Hazards Research. - : Elsevier BV. - 2666-5921. ; 2:2, s. 132-137
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Tidskriftsartikel (refereegranskat)abstract
- Tree radial growth is characterized by not only the annual ring-width increment but also shifts in the tree-ring geometric center (TRGC) if subjected to asymmetric external forcing, such as gravity downslope or prevailing winds. Previous dendrochronological studies have used the asymmetric growth derived from tree-ring widths to reconstruct wind speed changes. Here we propose a novel method that uses quantitative TRGC measurements to estimate wind speed. We investigated TRGC shifts in northeast China, where the prevailing westerly winds are strong and persistent. We found that the TRGC showed significant correlations (r = 0.64, p < 0.01) with wind speed in May–September. The higher tree geometry sensitivity to wind speed obtained with the new method compared to previous ones, suggests the possibility of reconstructing historical wind change and variability in prevailing winds using TRGC. In addition, by correcting tree-ring radius according to their TRGC shifts, the basal area increment (BAI) was calculated. Our new BAI estimation provided stronger correlations with climate than both the standard tree-ring width chronology and a traditional BAI estimation. We suggest that future dendrochronological studies should consider TRGC shifts to increase the accuracy in climate reconstructions.
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| 18. |
- Fang, Keyan, et al.
(författare)
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Time-varying relationships among oceanic and atmospheric modes: A turning point at around 1940
- 2018
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Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182. ; 487:SI, s. 12-25
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Elsevier Ltd and INQUA. Oceanic and atmospheric modes play a key role in modulating climate variations, particularly on interannual and interdecadal scales, causing an indirect response of regional climate to external forcings. This study comprehensively investigated the time-varying linkages among dominant oceanic and atmospheric modes of the Pacific and Atlantic areas on different timescales using the scale space multiresolution correlation analysis. For the Pacific Ocean, the Interdecadal Pacific Oscillation (IPO) shows closer matches with the El Niño-Southern Oscillation (ENSO) than with the Pacific Decadal Oscillation (PDO). This indicates that the ENSO dominates climate variability of the whole Pacific Ocean not only on interannual but also on interdecadal scales. Interdecadal variations of the IPO appear to be more closely linked to southern Pacific Ocean climate before ∼1940, but become more closely linked to northern Pacific Ocean after ∼1940. The shifts on interdecadal connections among northern, tropical and southern parts of the Pacific Oceans seems to be related to the phase shifts of the IPO/PDO, which may contribute to the cooling trend from 1940s to 1970s. For the Atlantic Ocean, the Atlantic Multi-decadal Oscillation (AMO) is closely linked to the North Atlantic Oscillation (NAO) on the interdecadal scale before ∼1940.
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| 19. |
- Guo, Guoyang, et al.
(författare)
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Increasing intrinsic water-use efficiency over the past 160 years does not stimulate tree growth in southeastern China
- 2018
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Ingår i: Climate Research. - : Inter-Research Science Center. - 0936-577X .- 1616-1572. ; 76:2, s. 115-130
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Inter-Research. Understanding the responses of tree growth and intrinsic water-use efficiency (iWUE) to anthropogenic CO2 increase and climate warming provides important benchmarks for evaluating future forest dynamics under different scenarios of warming and CO2 changes. Relative to the short period of instrumental data of the past few decades, long-term tree-ring width and stable carbon isotopic (δ13C) data are invaluable in fully comprehending their interactions during the entire industrial era, since ~1850. Here, we present a tree-ring width chronology (1856 to 2015) and Δ13C series (1876-2015) of Pinus massoniana for Yongtai county of Fujian province, in humid subtropical China, a 'green island' relative to other dry subtropical areas of the world. Tree growth was limited by precipitation of the hydrological year (previous November to current October) (r = 0.568, p < 0.001), and the stable carbon isotope discrimination (Δ13C) was strongly correlated with relative humidity in September-October (r =-0.677, p < 0.001) of the current growing season. We found that the iWUE increased by 40.9% since 1876. Specifically, we found that the ci:ca ratio decreased during the study period whereas intercellular CO2 concentration (ci) increased. The negative relationship between basal area increment (BAI) and iWUE indicated that increasing iWUE may not lead to long-term enhancement of tree growth. Our results indicated a drought-induced limitation to tree growth in response to rising CO2, and that trees may mitigate the negative effects of a decrease in water availability through a reduction in stomatal conductance.
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| 20. |
- He, M. S., et al.
(författare)
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A delayed modulation of solar ultraviolet radiation on the COVID-19 transmission reflects an incubation period
- 2022
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Ingår i: Meteorological Applications. - : Wiley. - 1350-4827 .- 1469-8080. ; 29:5
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory experiments have revealed the meteorological sensitivity of the coronavirus disease 2019 (COVID-19) virus. However, no consensus has been reached about how outdoor meteorological conditions modulate the virus transmission as it is also constrained by non-meteorological conditions. Here, we identify the outbreak's evolution stage, constrained least by non-meteorological conditions, by searching the maximum correlation coefficient between the ultraviolet flux and the growth rate of cumulative confirmed cases at the country level. At this least-constrained stage, the cumulative cases count around 1300-3200, and the count's daily growth rate correlates with the ultraviolet flux and temperature significantly (correlation coefficients r = -0.54 +/- 0.09 and -0.39 +/- 0.10 at p<0.01$$ p, respectively), but not with precipitation, humidity, and wind. The ultraviolet correlation exhibits a delay of about 7 days, providing a meteorological measure of the incubation period. Our work reveals a seasonality of COVID-19 and a high risk of a pandemic resurgence in winter, implying a need for seasonal adaption in public policies.
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| 21. |
- Li, D. W., et al.
(författare)
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Climate, intrinsic water-use efficiency and tree growth over the past 150 years in humid subtropical China
- 2017
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Influence of long-term changes in climate and CO2 concentration on intrinsic water-use efficiency (iWUE), defined as the ratio between net photosynthesis (A) and leaf conductance (g), and tree growth remain not fully revealed in humid subtropical China, which is distinct from other arid subtropical areas with dense coverage of broadleaf forests. This study presented the first tree-ring stable carbon isotope (delta C-13) and iWUE series of Pinus massoniana from 1865 to 2013 in Fujian province, humid subtropical China, and the first tree-ring width standard chronology during the period of 1836-2013 for the Niumulin Nature Reserve (NML). Tree-ring width growth was limited by precipitation in July-August (r = 0.40, p < 0.01). The tree-ring carbon isotope discrimination (Delta C-13) was mainly controlled by the sunshine hours (r = -0.66, p < 0.001) and relative humidity (r = 0.58, p < 0.001) in September-October, a season with rapid latewood formation in this area. The iWUE increased by 42.6% and the atmospheric CO2 concentration (c(a)) explained 92.6% of the iWUE variance over the last 150 years. The steady increase in iWUE suggests an active response with a proportional increase in intercellular CO2 concentration (c(i)) in response to increase in c(a). The contribution of iWUE to tree growth in the study region is not conspicuous, which points to influences of other factors such as climate.
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| 22. |
- Li, H. H., et al.
(författare)
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Influences of West Pacific Sea Surface Temperature on Covarying Eurasian Droughts Since the Little Ice Age
- 2020
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Ingår i: Quaternary. - : MDPI AG. - 2571-550X. ; 3:2
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Tidskriftsartikel (refereegranskat)abstract
- The Western Pacific Warm Pool (WP), with the highest sea surface temperature (SST) in the world, has strong impacts on the drought variations in Eurasia. However, since the little ice age (1250-1850, LIA), the co-climatic drought pattern due to WP warming in Eurasia remains unclear. This is a long-term warming background for the current warming period (CWP). In this paper, we use both instrumental data and 1625 tree-ring width records from Eurasia to investigate the drought patterns in both modern and historical periods. This study revealed two seesaw precipitation patterns, namely the Central Asia-Mongolia (CAMO) and Northern Europe-Southern Europe (NESE) patterns. When the Western Pacific Warm Pool sea surface temperature (WPSST) is high, precipitation increases in Central Asia and Northern Europe, and decreases in Mongolia and southern Europe. When the positive (negative) phase event of the El Nino-Southern Oscillation (ENSO) occurs, the WPSST is reduced (increased), and the decreases (increases) of precipitation in Central Asia and Northern Europe and the increases (decreases) in precipitation in Mongolia and southern Europe are more obvious. The CAMO dipole has been strengthened since the LIA. The CAMO dipole is positively correlated with solar radiation and Northern Hemisphere temperature, and negatively correlated with Pacific decadal oscillations (PDO).
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| 23. |
- Li, Tiewei, et al.
(författare)
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Increasing Sensitivity of Tree Radial Growth to Precipitation
- 2024
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Ingår i: Geophysical Research Letters. - 1944-8007 .- 0094-8276. ; 51:16
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Tidskriftsartikel (refereegranskat)abstract
- The sensitivity of tree growth to precipitation regulates their responses to drought, and is a crucial metric for predicting ecosystem dynamics and vulnerability. Sensitivity may be changing with continuing climate change, yet a comprehensive assessment of its change is still lacking. We utilized tree ring measurements from 3,044 sites, climate data and CO2 concentrations obtained from monitoring stations, combined with dynamic global vegetation models to investigate spatiotemporal changes in the sensitivity over the past century. We observed an increasing sensitivity since around 1950. This increased sensitivity was particularly pronounced in arid biomes due to the combined effect of increased precipitation and elevated CO2. While elevated CO2 reduced the sensitivity of the humid regions, the intensified water pressure caused by decreased precipitation still increased the sensitivity. Our findings suggest an escalating vulnerability of tree growth to precipitation change, which may increase the risk of tree mortality under future intensified drought.
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| 24. |
- Li, Y. J., et al.
(författare)
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Growth decline of Pinus Massoniana in response to warming induced drought and increasing intrinsic water use efficiency in humid subtropical China
- 2019
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Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 57:October
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Tidskriftsartikel (refereegranskat)abstract
- Pinus Massoniana is the most widely distributed coniferous species in southern China and one of the most distributed species for plantation in China. It is not uncertain about the responses of tree growth to the combined effects of regional drying and the increase in the intrinsic water-use efficiency (iWUE) due to increased atmospheric CO2. This study addressed this issue by comparing the tree growth patterns as represented by three tree-ring width chronologies with climate variables and three iWUE series derived from three tree-ring stable carbon isotope discrimination chronologies (Delta C-13) from Pinus Massoniana in Daiyun Mountain, central Fujian province of China. Among these chronologies, we reported the first tree-ring carbon isotope discrimination chronologies (Delta C-13) from Fuzhou area spanning last 210 years. It was found that tree radial growth is mainly limited by dry condition from May to October. Growth limitation by cold condition was only found in one high altitude site (780m) in early spring and late autumn. The tree-ring carbon discrimination was enhanced under conditions with low relative humidity and sufficient sunshine in late summer and autumn. In general, the iWUE showed a significantly increasing trend since the 1850s for all the sites in response to the increase in atmospheric CO2. However, the growth promotion of the increased iWUE on tree growth could not compensate the growth limitation caused by drought. Especially since the 1960s, a growth decline was found at two drought stressed sites at low altitudes. On the other hand, the increase in temperature of spring and autumn and iWUE has most likely enhanced tree growth at the high altitude site.
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| 25. |
- Shi, Feng, et al.
(författare)
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A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium
- 2015
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Ingår i: Climatic Change. - : Springer Science and Business Media LLC. - 0165-0009 .- 1573-1480. ; 131:4, s. 663-674
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Tidskriftsartikel (refereegranskat)abstract
- To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June–July–August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400.
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| 26. |
- Tang, Wanru, et al.
(författare)
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Drought variations in the southeastern Tibetan Plateau region since 1704 and their link to the Atlantic Multidecadal Oscillation
- 2023
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 630
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the long-term history of drought in the Tibetan Plateau region is important to improve understanding of drought frequency in response to future global warming. Although the Tibetan Plateau has become generally wetter recently, the southeastern part of the Tibetan Plateau has become drier since the 2000s. To place this drying trend in a historical context, we conducted tree-ring studies for Abies spectabilis and Tsuga dumosa at three sites in the southeastern Tibetan Plateau, and developed tree-ring width (TRW), earlywood width (EWW), and latewood width (LWW) chronologies to permit local drought reconstruction. Based on correlation between these tree-ring parameters and instrumental meteorological data, the EWW chronologies were identified as suitable variables for reconstructing the average April–July self-calibrating Palmer Drought Index (scPDSI). The reconstruction accounted for 45.86% of the variance in the instrumental record and allowed us to extend the drought record back to 1704 CE. Based on this new dataset, the driest interval was from 1907 to 1919 CE during which time agricultural production fell by about 70% according to written historical records, leading to severe famine. Our findings suggest that this early twentieth century drought was in phase with the previously known drought over the northern Daxing'an Mountains. However, the southeastern Tibetan Plateau drought occurred one decade earlier than the known widespread drought event in North China during the 1920s–1930s. We show that this spatial drought pattern may have been modulated by the Atlantic Multidecadal Oscillation.
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| 27. |
- Wang, Lei, et al.
(författare)
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Intensified variability of the El Niño–Southern Oscillation enhances its modulations on tree growths in southeastern China over the past 218 years
- 2018
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 38:14, s. 5293-5304
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Royal Meteorological Society Lack of long-term tree-ring records in the core regions of the Asian summer monsoon in southeastern China limits our ability of evaluating the current climate change in a historical context. In this study, we developed the first 218-year tree-ring chronology (1798–2015) of Pinus massoniana in Zhangping area, Fujian Province, humid subtropical China. This chronology is positively correlated with winter–spring (January–March) temperature (r = 0.359, p <.01) and summer (July–September) precipitation (r = 0.351, p <.01). Although the correlations between our tree rings with sea surface temperatures (SSTs) are not very high, the correlation pattern is very close to the correlation pattern with the El Niño–Southern Oscillation variability (ENSO). These suggest that the ENSO could be the major large-scale regulator on the growth of our tree rings. The strength of the correlations between our tree rings and the ENSO (r = 0.30, N = 66) matches closely with the ENSO variability during 1950–2015. The modulations of the ENSO on regional tree growth have been the most conspicuous since the 1950s, which corresponds to its enhanced inter-annual variability. The extreme growth anomalies match quite well with the extreme years of the moisture-sensitive chronologies. The dry epoch from 1935 to 1958 is the most severe long-lasting drought in our tree rings, which is a widely distributed pattern in southeastern China and is likely modulated by the La Niña-like modes in that period.
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| 28. |
- Xing, Hang, et al.
(författare)
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Impacts of changes in climate extremes on wildfire occurrences in China
- 2023
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Ingår i: Ecological Indicators. - 1470-160X. ; 157
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Tidskriftsartikel (refereegranskat)abstract
- Climate change has caused more frequent instances of extreme climatic events around the world, being an influential factor on the occurrence of wildfires in China on large scale. However, the impact of changes in extreme climate on the occurrence of wildfires in different climate zones remains unclear. In the present study, 26 extreme climate indices were selected to analyze the thereof relationship with wildfire occurrences from 2005 to 2018 in different regions of China. Wildfires in China primarily occur in the south, with a measurable presence in the north. On an annual scale, the wildfire occurrences in southwestern China show stronger correlations with mean temperature than extreme temperature indices, but show stronger correlations with extreme precipitation indices than the total precipitation. On the contrary, the wildfire occurrences in southeastern China show stronger correlations with the total precipitation than extreme precipitation indices, but show stronger correlations with extreme temperature indices than the mean temperature. In Northeast China, wildfires show a more significant correlation with mean temperature than with any extreme climate indices, indicating a minimal impact from extreme climatic conditions. The fire-climate relationships in the main fire season (January-April) are similar to those in the annual scale. The wildfire occurrences in the southwestern, south-central, and southeastern China, which are located in the same latitudes, were affected by extreme climate indices of different types and on different time scales. Furthermore, we recommend that consecutive dry days (CDD) and diurnal temperature range (DTR) should be considered first when studying the relationship between wildfire occurrence and extreme climate in southwestern and southeastern China respectively.
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| 29. |
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| 30. |
- Zhang, Peng, et al.
(författare)
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Abrupt shift to hotter and drier climate over inner East Asia beyond the tipping point
- 2020
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 370:6520, s. 1095-1099
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Tidskriftsartikel (refereegranskat)abstract
- Unprecedented heatwave-drought concurrences in the past two decades have been reported over inner East Asia. Tree-ring–based reconstructions of heatwaves and soil moisture for the past 260 years reveal an abrupt shift to hotter and drier climate over this region. Enhanced land-atmosphere coupling, associated with persistent soil moisture deficit, appears to intensify surface warming and anticyclonic circulation anomalies, fueling heatwaves that exacerbate soil drying. Our analysis demonstrates that the magnitude of the warm and dry anomalies compounding in the recent two decades is unprecedented over the quarter of a millennium, and this trend clearly exceeds the natural variability range. The “hockey stick”–like change warns that the warming and drying concurrence is potentially irreversible beyond a tipping point in the East Asian climate system.
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| 31. |
- Zhang, Y., et al.
(författare)
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Reconstruction of soil erosion rates from exposed roots in southeast China
- 2017
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Ingår i: Asian Geographer. - : Informa UK Limited. - 1022-5706 .- 2158-1762. ; 34:2, s. 91-105
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Tidskriftsartikel (refereegranskat)abstract
- Southeast China, characterized by a humid subtropical climate, is dominated by dense evergreen broad-leaved forests with the exception for the Changting area, which is one of the most eroded areas in southern China. Various methods have been employed to investigate regional soil erosion dynamics, yet these studies are limited to short periods and few sites. Dendrogeomorphological methods can alleviate this problem due to the long duration of tree rings and easy implementation for many sites. We present the first tree-ring-based soil erosion study in southeastern China, based on 123 exposed roots from 85 Pinus massoniana trees at six sites in Changting. The distinct reduction of cell lumen area of earlywood tracheids of exposed roots is a good bio-indicator for the first year of exposure due to soil erosion for this hot and humid area. The reconstructed soil erosion rates ranged from 4.26 to 43.50 mm/year with an average of 14.14 +/- 8.05 mm/year. Soil erosion rate is the highest at the slopes of 10 degrees-30 degrees. This is in line with previous findings using other methods over the study area. In addition, soil erosion in this area is found to be closely related to vegetation types and summer precipitation.
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| 32. |
- Zhao, Yesi, et al.
(författare)
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Deciphering the transfer of hydroclimate signals to tree-ring S18O 18 O using a proxy system model in East Asia's Meiyu region
- 2024
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Ingår i: CHEMICAL GEOLOGY. - 0009-2541 .- 1872-6836. ; 668
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Tidskriftsartikel (refereegranskat)abstract
- The stable oxygen isotope ratios of whole tree-ring alpha-cellulose ( S 18 O WR ) have been interpreted as an indicator of early summer hydroclimate in the Meiyu region of East Asia. However, the underlying physical mechanism often remains unclear. Here we provide a mechanistic understanding through intra-annual tree-ring oxygen isotope analysis and process-based S 18 O WR modelling over the period 1979-2006. The selected tree species for analysis is Pinus taiwanensis, , whose S 18 O WR exhibit the strongest linear relationship with relative humidity (RH) in June. The results indicated that the June RH signal is predominantly contained in tree-ring earlywood rather than latewood. The strong response of S 18 O WR to June RH is not due to the legacy effect. Using the proxy system model (PSM) of S 18 O WR , we obtained a modeled S 18 O WR time series that is significantly positively correlated with the measured S 18 O WR time series. The modeled and measured S 18 O WR series show similar relationships with monthly RH. Sensitivity experiments with PSM revealed that the June RH signal is originated from the oxygen isotopes of source water and leaf water. Rapid cellulose formation in June plays a role in enhancing the June RH signal. Our study demonstrates how S 18 O WR record early summer hydroclimate signals from a process perspective, and that the PSM is effective in modelling the interannual S 18 O WR variability in the Meiyu region.
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| 33. |
- Zhao, Z., et al.
(författare)
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Responses of the radial growth of the endangered species Keteleeria fortunei to climate change in southeastern China
- 2019
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Ingår i: Trees-Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890. ; 33:4, s. 977-985
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge on the responses of endangered species to current global changes can highlight the necessity and importance of protecting these species. Tree-ring-based studies provide a longer term perspective than monitoring studies on the responses and adaptations of the growth of endangered species to climate change and forest disturbances. Therefore, this study conducted a tree-ring case study on Keteleeria fortunei, an endangered and endemic species in southern China, and presents the first tree-ring chronology of K. fortunei from 1850 to 2013 in the Fuzhou area, which is located west of the Taiwan Strait. K. fortunei trees tend to grow in moister locations in closed forests and are more sensitive to forest disturbances and sunshine than Pinus massoniana. Our study shows that missing rings are more frequent for K. fortunei than for P. massoniana in the same area, which agrees with previous findings that wedging and missing rings tend to occur in trees experiencing growth suppression in closed forests.
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| 34. |
- Zhou, Feifei, et al.
(författare)
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ENSO weakens the co-variability between the spring persistent rains and Asian summer monsoon: Evidences from tree-ring data in southeastern China
- 2024
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Ingår i: Journal of Hydrology. - 0022-1694. ; 634
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Tidskriftsartikel (refereegranskat)abstract
- The Spring Persistent Rains (SPR) and the Asian Summer Monsoon (ASM) are the two dominant rainfall systems in East Asia, providing together a majority of annual rainfall in southeastern China (SEC). Since observational data in SEC were mostly unavailable until the 1950s, proxy records that are capable of capturing the SPR and ASM variations are required to examine the long-term co-variability patterns between them. Tree-ring earlywood and latewood δ18O records in SEC were found to respond to relative humidity (RH) during the SPR and ASM seasons, respectively, allowing us, for the first time, to reconstruct the RH changes of SPR and ASM back to 1801. The two reconstructions can explain 44.9 % and 42.3 % of the instrumental variance. We observed a long-lasting wet epoch in the 1920s–60s for both the SPR and ASM, caused by a peak in the land–ocean thermal contrast. The El Niño-Southern Oscillation (ENSO) and the Intertropical Convergence Zone (ITCZ) were found to be the two leading tropical systems that modulated the SPR and ASM co-variability. During a period with weakened ENSO variance, the RH of SPR and ASM showed in-phase changes driven by the ITCZ. However, when the ENSO variance became strengthened, the co-variability collapsed since the ENSO can offset the influence of the ITCZ via teleconnections.
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| 35. |
- Zhou, F. F., et al.
(författare)
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Hydroclimate Change Encoded in Tree Rings of Fengshui Woods in Southeastern China and its Teleconnection With El Nino-Southern Oscillation
- 2020
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Ingår i: Water Resources Research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 56:1
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Tidskriftsartikel (refereegranskat)abstract
- Hydroclimate variations inferred from proxies, such as tree rings, provide a long-term context for the understanding of the current climate change. In humid Southeastern China (SEC), relatively limited long-term tree-ring records were published due to the paucity of old trees. This study develops a robust tree-ring width chronology from the Chinese cedar (Cryptomeria fortune) Fengshui woods, spanning from 1781 to 2015, by far the longest in SEC. Common growth anomalies of the Fengshui trees can well capture long-term springtime (March-May) Standardized Precipitation Evapotranspiration Index (SPEI) changes over the past 230 years in SEC. This hydroclimate-sensitive chronology shows significant correlations with El Nino-Southern Oscillation (ENSO) like sea surface temperature modes, indicating that ENSO may act as an important regulator in local springtime SPEI. However, interdecadal shifts in the relationships between the variances of tree rings and ENSO reveal that the ENSO-SPEI teleconnection over SEC was an unstable process, and it collapsed during the periods of 1820s-1860s and 1920s-1960s, when ENSO was in its decaying phases.
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| 36. |
- Zhou, F. F., et al.
(författare)
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Teleconnections between large-scale oceanic-atmospheric patterns an interannual surface wind speed variability across China: Regional and seasonal patterns
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 838
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Tidskriftsartikel (refereegranskat)abstract
- Great attention has been paid to the long-term decline in terrestrial near-surface wind speed (SWS) in China. However, how the SWS varies with regions and seasons and what modulates these changes remain unclear. Based on quality-controlled and homogenized terrestrial SWS data from 596 stations, the covarying SWS patterns during the Asian Summer Monsoon (ASM) and the Asian Winter Monsoon (AWM) seasons are defined for China using empirical orthogonal function (EOF) analysis for 1961-2016. The dominant SWS features represented by EOF1 patterns in both seasons show a clear decline over most regions of China. The interannual variability of the EOF1 patterns is closely related to the Northeast Asia Low Pressure (NFAIP) and the Arctic Oscillation (AO), respectively. The EOF2 and EOF3 patterns during ASM (AWM) season describe a dipole mode of SWS between Fast Tibetan Plateau and Fast China Plain (between Fast Tibetan Plateau and Northeast China), and between Southeast and Northeast China (between Northeast China and the coastal areas of Southeast China), respectively. These dipole structures of SWS changes arc closely linked with the oceanic-atmospheric oscillations on interannual scale.
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| 37. |
- Zhou, Feifei, et al.
(författare)
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Summer heat induced the decline of Pinus taiwanensis forests at its southern limit in humid Subtropical China
- 2024
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Ingår i: Agricultural and Forest Meteorology. - 0168-1923. ; 350
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Tidskriftsartikel (refereegranskat)abstract
- Warming-induced aridity has caused forest decline and mortality for many sites with water-limiting conditions. However, equatorward rear-edge Pinus taiwanensis trees at the Daiyun Mountains in humid subtropical China are also suffering die-backs and decline, but the roles played by heat or drought stress still remain unclear. Here, we compared the tree-ring radial width, anatomical features, stable carbon isotope (δ13C) and intrinsic water use efficiency (iWUE) between die-back and healthy trees to elucidate potential causes driving the decline. Die-back trees showed sustained growth reductions and produced tracheids with thinner cell walls over the recent decade, indicative of reduced carbon assimilation. The climate response pattern and Vaganov-Shashkin (V-S) model indicated the critical role of summer (June-August) temperature in recent growth decline. Long-term higher wood δ13C and iWUE within die-back trees indicated that actual growth decline already started several decades earlier. This conservative growth strategy was at the cost of low efficiency of photosynthesis due to chronic stomatal closure. When the lethal heatwaves arrived, these weakened trees were not able to access sufficient carbonhydrates to maintain metabolism, causing a distinct decline and mortality. We concluded that recent decline in Pinus taiwanensis trees was mainly caused by long-term carbon starvation.
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