Tree-ring δ18O inferred spring drought variability over the past 200 years in the Hengduan Mountains, Southwest China

2019 ◽  
Vol 518 ◽  
pp. 22-33 ◽  
Author(s):  
Fan Zhao ◽  
Zexin Fan ◽  
Tao Su ◽  
Shufeng Li ◽  
He Tang ◽  
...  
Keyword(s):  
Tree Ring ◽  
Southwest China ◽  
Hengduan Mountains ◽  
Drought Variability ◽  
The Past

scholarly journals Spatiotemporal drought variability for central and eastern Asia over the past seven centuries derived from tree-ring based reconstructions

2013 ◽  
Vol 283 ◽  
pp. 107-116 ◽  
Author(s):  
Keyan Fang ◽  
Xiaohua Gou ◽  
Fahu Chen ◽  
Nicole Davi ◽  
Changzhi Liu
Keyword(s):  
Tree Ring ◽  
Eastern Asia ◽  
Drought Variability ◽  
The Past

scholarly journals Tree-ring-based assessments of drought variability during the past 400 years in the Tianshan mountains, arid Central Asia

2021 ◽  
Vol 126 ◽  
pp. 107702
Author(s):  
Ting Wang ◽  
Anming Bao ◽  
Wenqiang Xu ◽  
Ruide Yu ◽  
Qingling Zhang ◽  
...  
Keyword(s):  
Central Asia ◽  
Tree Ring ◽  
Tianshan Mountains ◽  
Drought Variability ◽  
Arid Central Asia ◽  
The Past

scholarly journals Supporting Restoration Decisions through Integration of Tree-Ring and Modeling Data: Reconstructing Flow and Salinity in the San Francisco Estuary over the Past Millennium

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2139
Author(s):  
Paul H. Hutton ◽  
David M. Meko ◽  
Sujoy B. Roy
Keyword(s):  
San Francisco ◽  
Tree Ring ◽  
San Francisco Estuary ◽  
Salinity Intrusion ◽  
Estuarine Ecosystem ◽  
Freshwater Flow ◽  
The Past ◽  
Decadal Scale ◽  
Tree Ring Data ◽  
Past Millennium

This work presents updated reconstructions of watershed runoff to San Francisco Estuary from tree-ring data to AD 903, coupled with models relating runoff to freshwater flow to the estuary and salinity intrusion. We characterize pre-development freshwater flow and salinity conditions in the estuary over the past millennium and compare this characterization with contemporary conditions to better understand the magnitude and seasonality of changes over this time. This work shows that the instrumented flow record spans the range of runoff patterns over the past millennium (averaged over 5, 10, 20 and 100 years), and thus serves as a reasonable basis for planning-level evaluations of historical hydrologic conditions in the estuary. Over annual timescales we show that, although median freshwater flow to the estuary has not changed significantly, it has been more variable over the past century compared to pre-development flow conditions. We further show that the contemporary period is generally associated with greater spring salinity intrusion and lesser summer–fall salinity intrusion relative to the pre-development period. Thus, salinity intrusion in summer and fall months was a common occurrence under pre-development conditions and has been moderated in the contemporary period due to the operations of upstream reservoirs, which were designed to hold winter and spring runoff for release in summer and fall. This work also confirms a dramatic decadal-scale hydrologic shift in the watershed from very wet to very dry conditions during the late 19th and early 20th centuries; while not unprecedented, these shifts have been seen only a few times in the past millennium. This shift resulted in an increase in salinity intrusion in the first three decades of the 20th century, as documented through early records. Population growth and extensive watershed modification during this period exacerbated this underlying hydrologic shift. Putting this shift in the context of other anthropogenic drivers is important in understanding the historical response of the estuary and in setting salinity targets for estuarine restoration. By characterizing the long-term behavior of San Francisco Estuary, this work supports decision-making in the State of California related to flow and salinity management for restoration of the estuarine ecosystem.

scholarly journals Tree Vitality and Forest Health: Can Tree-Ring Stable Isotopes Be Used as Indicators?

2021 ◽  
Author(s):  
Paolo Cherubini ◽  
Giovanna Battipaglia ◽  
John L. Innes
Keyword(s):  
Air Pollution ◽  
Stable Isotopes ◽  
Tree Ring ◽  
Forest Decline ◽  
Forest Health ◽  
Stress Factors ◽  
Tree Vitality ◽  
The Past ◽  
Physiological Processes

Abstract Purpose of Review Society is concerned about the long-term condition of the forests. Although a clear definition of forest health is still missing, to evaluate forest health, monitoring efforts in the past 40 years have concentrated on the assessment of tree vitality, trying to estimate tree photosynthesis rates and productivity. Used in monitoring forest decline in Central Europe since the 1980s, crown foliage transparency has been commonly believed to be the best indicator of tree condition in relation to air pollution, although annual variations appear more closely related to water stress. Although crown transparency is not a good indicator of tree photosynthesis rates, defoliation is still one of the most used indicators of tree vitality. Tree rings have been often used as indicators of past productivity. However, long-term tree growth trends are difficult to interpret because of sampling bias, and ring width patterns do not provide any information about tree physiological processes. Recent Findings In the past two decades, tree-ring stable isotopes have been used not only to reconstruct the impact of past climatic events, such as drought, but also in the study of forest decline induced by air pollution episodes, and other natural disturbances and environmental stress, such as pest outbreaks and wildfires. They have proven to be useful tools for understanding physiological processes and tree response to such stress factors. Summary Tree-ring stable isotopes integrate crown transpiration rates and photosynthesis rates and may enhance our understanding of tree vitality. They are promising indicators of tree vitality. We call for the use of tree-ring stable isotopes in future monitoring programmes.

Response of Siberian trees to climatic changes over the past 1500 years

2021 ◽  
Author(s):  
Olga Churakova (Sidorova) ◽  
Marina Fonti ◽  
Rolf Siegwolf ◽  
Tatyana Trushkina ◽  
Eugene Vaganov ◽  
...  
Keyword(s):  
Tree Ring ◽  
Ice Core ◽  
Climatic Changes ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Taimyr Peninsula ◽  
Climate Conditions ◽  
Northeastern Part ◽  
The Past ◽  
Tree Ring Cellulose

<p>We use an interdisciplinary approach combining stable isotopes in tree rings, pollen data, ice cores from temperature-limited environment in the Siberian north and developed a comprehensive description of the climatic changes over the past 1500 years. We found that the Climatic Optimum Period was warmer and drier compared to the Medieval one, but rather similar to the recent period. Our results indicate that the Medieval Warm period in the Taimyr Peninsula started earlier and was wetter compared to the northeastern part of Siberia (northeastern Yakutia). Summer precipitation reconstruction obtained from carbon isotopes in tree-ring cellulose from Taimyr Peninsula significantly correlated with the pollen data of the Lama Lake (Andreev et al. 2004) and oxygen isotopes of the ice core from Severnaya Zemlya (Opel et al. 2013) recording wetter climate conditions during the Medieval Warm period compared to the northeastern part of Siberia. Common large-scale climate variability was confirmed by significant relationship between oxygen isotope data in tree-ring cellulose from the Taimyr Peninsula and northeastern Yakutia, and oxygen isotope ice core data from Severnaya Zemlja during the Medieval Warm period and the recent one. Finally, we showed that the recent warming on the Taimyr Peninsula is not unprecedented in the Siberian north. Similar climate conditions were recorded by stable isotopes in tree rings, pollen, and ice core data 6000 years ago. On the northeastern part of Siberia newly developed a 1500-year summer vapor pressure deficit (VPD) reconstruction showed, that VPD increased recently, but does not yet exceed the maximum values reconstructed during the Medieval Warm period. The most humid conditions in the northeastern part of Siberia were recorded in the Early Medieval period and during the Little Ice Age. However, the increasing VPD under elevated air temperature in the last decades affects the hydrological regime of these sensitive ecosystems by greater evapotranspiration rates. Further VPD increase will significantly affect Siberian forests most likely leading to drought even under additional access of thawed permafrost water.</p><p>This work was supported by the FP7-PEOPLE-IIF-2008 - Marie Curie Action: "International Incoming Fellowships" 235122 and "Reintegration Fellowships" 909122 “Climatic and environmental changes in the Eurasian Subarctic inferred from tree-ring and stable isotope chronologies for the past and recent periods” and the Government of Krasnoyarsk Kray and Russian Foundation for Basic Research and Krasnoyarsk Foundation 20-44-240001 “Adaptation of conifer forests on the north of the Krasnoyarsk region (Taimyr Peninsula) to climatic changes after extreme events over the past 1500 years“ awarded to Olga V. Churakova (Sidorova).</p>

scholarly journals Cytospora (Diaporthales) in China

2020 ◽  
Vol 45 (1) ◽  
pp. 1-45 ◽  
Author(s):  
X.L. Fan ◽  
J.D.P. Bezerra ◽  
C.M. Tian ◽  
P.W. Crous
Keyword(s):  
New Species ◽  
Host Plants ◽  
Southwest China ◽  
New Combination ◽  
Large Collection ◽  
Dna Phylogeny ◽  
The Past ◽  
Worldwide Distribution ◽  
Wide Range ◽  
Woody Host

Members of the genus Cytospora are often reported as endophytes, saprobes or phytopathogens, primarily causing canker diseases of woody host plants. They occur on a wide range of hosts and have a worldwide distribution. Although several species have in the past been reported from China, the vast majority are not known from culture or DNA phylogeny. The primary aim of the present study was thus to clarify the taxonomy and phylogeny of a large collection of Cytospora species associated with diverse hosts in China. Cytospora spp. were collected in northeast, northwest, north and southwest China, indicating that the cold and dry environments favour these fungi. In this paper, we provide an assessment of 52 Cytospora spp. in China, focussing on 40 species represented by 88 isolates from 28 host genera. Based on a combination of morphology and a six-locus phylogeny (ITS, LSU, act1, rpb2, tef1-α and tub2), 13 new species and one new combination are introduced. The majority of the species investigated here appear to be host-specific, although further collections and pathogenicity studies will be required to confirm this conclusion.

scholarly journals Trans-regional rice supply paradigm reveals unsustainable water use in China

Water Policy ◽  
2021 ◽  
Author(s):  
Liang Wu ◽  
Min Wang ◽  
Kirti Avishek
Keyword(s):  
Water Use ◽  
Northeast China ◽  
Southwest China ◽  
Water Security ◽  
Rice Production ◽  
Consumption Pattern ◽  
Sustainable Food ◽  
The Past ◽  
Production And Consumption ◽  
Global Population

Abstract Rice is an important staple food for more than half of the global population and one of the largest water consumers on earth. Improving the efficiency of water embedded in rice production and supply could have great implications for food and water security. This study starts from Yunnan, a traditional rice producing and consuming province in southwest China, and analyses its rice supply structure and dynamics, together with embedded water footprints (WFs) of three other regions: Northeast China, South and Southwest China and Southeast Asia. The results show that Yunnan has been under through drastic food change in the past decades, leading to increasing production and supply gap. Yunnan is found to have the least WF (778.2 m3/t) for rice production across the study regions, while Northeast China consumes the highest blue WF (364.6 m3/t) and blue to total WF ratio (97.7%). The study indicates that Northeast China is at risk of groundwater deficit due to rice production and export and the current rice production and consumption pattern is inefficient. The study suggests that policies for groundwater extraction, water resource price and international trade need to be in place to ensure sustainable food supply and water use at regional and national levels.

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