23 results on '"Helle, Gerhard"'
Search Results
2. A high yield cellulose extraction system for small whole wood samples and dual measurement of carbon and oxygen stable isotopes
- Author
-
Andreu-Hayles, Laia, Levesque, Mathieu, Martin-Benito, Dario, Huang, Wei, Harris, Ryan, Oelkers, Rose, Leland, Caroline, Martin-Fernández, Javier, Anchukaitis, Kevin J., and Helle, Gerhard
- Published
- 2019
- Full Text
- View/download PDF
3. Oxygen isotopes in tree rings show good coherence between species and sites in Bolivia
- Author
-
Baker, Jessica C.A., Hunt, Sarah F.P., Clerici, Santiago J., Newton, Robert J., Bottrell, Simon H., Leng, Melanie J., Heaton, Timothy H.E., Helle, Gerhard, Argollo, Jaime, Gloor, Manuel, and Brienen, Roel J.W.
- Published
- 2015
- Full Text
- View/download PDF
4. Climate sensitivity and parameter coherency in annually resolved δ13C and δ18O from Pinus uncinata tree-ring data in the Spanish Pyrenees
- Author
-
Konter, Oliver, Holzkämper, Steffen, Helle, Gerhard, Büntgen, Ulf, Saurer, Matthias, and Esper, Jan
- Published
- 2014
- Full Text
- View/download PDF
5. Hydroclimatic variation in Far North Queensland since 1860 inferred from tree rings
- Author
-
Heinrich, Ingo, Weidner, Kathrin, Helle, Gerhard, Vos, Heinz, and Banks, John C.G.
- Published
- 2008
- Full Text
- View/download PDF
6. Climate signals in tree-ring width, density and δ13C from larches in Eastern Siberia (Russia)
- Author
-
Kirdyanov, Alexander V., Treydte, Kerstin S., Nikolaev, Anatolii, Helle, Gerhard, and Schleser, Gerhard H.
- Published
- 2008
- Full Text
- View/download PDF
7. Environmental history of the German Lower Rhine Embayment during the Middle Miocene as reflected by carbon isotopes in brown coal
- Author
-
Lücke, Andreas, Helle, Gerhard, Schleser, Gerhard H., Figueiral, Isabel, Mosbrugger, Volker, Jones, Timothy P., and Rowe, Nick P.
- Published
- 1999
- Full Text
- View/download PDF
8. Inter-annual variation of tree-ring width, δ13C and δ18O in juvenile trees of five plantation poplar cultivars (Populus spp.).
- Author
-
Meyer, Matthias, Krabel, Doris, Kniesel, Britt, and Helle, Gerhard
- Abstract
Abstract The 10-year juvenile records of three hybrid poplar and two aspen cultivars (Populus spp.) from a short rotation coppice (SRC) were assessed by measuring tree-ring width (annual radial increment, i r) and stable isotope ratios of carbon and oxygen (δ
13 C and δ18 O) of α-cellulose. All cultivars showed common ‘juvenile trends’ that were modeled with nonlinear fit (NLF) functions. The i r of all cultivars culminated in the middle of the juvenile phase. Within the first ten years, δ13 C showed a gradual decrease of approximately 2.5 ‰ in all cultivars and δ18 O showed an asymptotic increase which was variable among the poplar cultivars and which was more pronounced in two hybrid poplars. Potential causes of the juvenile inter-annual variability of δ13 C and δ18 O were discussed. Likely, the maturation related changes in hydraulic architecture, the canopy closure and the resulting increase of the proportion of shaded crown segments which have lower photosynthetic capacities had an effect on δ13 C. An additional effect of changes in N nutrition on δ13 C is assumed at the present SRC trial because the NO 3− concentration had significantly decreased after ten years. Interpretation of δ18 O data remained difficult given the lack of soil water δ18 O records. The maturation effect and the respective interaction have resulted in large temporal variability in the present three investigated tree ring traits. However, the impact of two drought vegetation periods (2003 and 2006) was still reflected by the juvenile tree ring records of all traits. Different juvenile trends in the records of the stable isotope ratios δ13 C and δ18 O, and the trend slopes, which may vary between genetically different cultivars, must be considered in tree ring investigations of SRC poplars. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
9. A guideline for sample preparation in modern tree-ring stable isotope research.
- Author
-
Schollaen, Karina, Baschek, Heiko, Heinrich, Ingo, Slotta, Franziska, Pauly, Maren, and Helle, Gerhard
- Abstract
The comprehensive procedure of wood sample preparation, including tree-ring dissection, cellulose extraction, homogenization and packing for stable isotope analysis, is labour intensive and time consuming. Based on a brief compilation of existing methods, we present a methodological approach from pre-analyses considerations to wood sample preparation, semi-automated chemical extraction of cellulose from tree-ring cross-sections, and tree-ring dissection for stable isotope ratio mass spectrometry: the Cross-Section Extraction and Dissection (CSED) guideline. Following the CSED guideline can considerably increase efficiency of tree-ring stable isotope measurement compared to classical methods
We introduce a user-friendly device for cellulose extraction, allowing simultaneous treatment of wood cross-sections of a total length of 180 cm (equivalent to 6 increment cores of 30 cm length) and thickness of 0.6–2.0 mm. After cellulose extraction, tree-ring structures of 10 tree species (coniferous and angiosperm wood) with different wood growth rates and tree-ring boundaries, largely remained well identifiable. Further, we demonstrate that tree rings from cellulose cross-sections can be dissected at annual to intra-seasonal resolution, utilizing simple manual devices as well as sophisticated UV-laser microdissection microscopes in a way that sample homogenization is no longer necessary in most cases. We investigate seasonal precipitation signals in high-resolution intra-annual δ 18 O cellulose values from African baobab, performed by using UV-laser microdissection microscopes. [ABSTRACT FROM AUTHOR] - Published
- 2017
- Full Text
- View/download PDF
10. Applying CLSM to increment core surfaces for histometric analyses: A novel advance in quantitative wood anatomy.
- Author
-
Liang, Wei, Heinrich, Ingo, Helle, Gerhard, Liñán, Isabel Dorado, and Heinken, Thilo
- Abstract
Abstract: A novel procedure has been developed to conduct cell structure measurements on increment core samples of conifers. The procedure combines readily available hardware and software equipment. The essential part of the procedure is the application of a confocal laser scanning microscope (CLSM) which captures images directly from increment cores surfaced with the advanced WSL core-microtome. Cell wall and lumen are displayed with a strong contrast due to the monochrome black and green nature of the images. Consecutive images are merged into long images representing entire increment cores which are then analysed for cell structures in suitable software. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
11. Response of climate-growth relationships and water use efficiency to thinning in a Pinus nigra afforestation.
- Author
-
Martín-Benito, Darío, Del Río, Miren, Heinrich, Ingo, Helle, Gerhard, and Cañellas, Isabel
- Subjects
VEGETATION & climate ,TREE growth ,PLANT-water relationships ,AUSTRIAN pine ,FOREST density ,FOREST management ,CARBON isotopes ,OXYGEN isotopes - Abstract
Abstract: Thinning is the main forestry measure to increase tree growth by reducing stand tree density and competition for resources. A thinning experiment was established in 1993 on a 32-year-old Pinus nigra Arn. stand in central Spain. The response of growth, climate-growth relationships and intrinsic water use efficiency (WUEi) to a stand density reduction were compared between moderate thinned plots and a control plot by a combined analysis of basal area increments (BAI), and C and O stable isotope ratios (δ
13 Cc and δ18 Oc ). BAI in the control plot showed a decreasing trend that was avoided by thinning in the thinned plot. Thinning also partially buffered tree-ring response to climate and trees were less sensitive to precipitation although more sensitive to temperature. Δ13 Cc in the thinned plot was not modified indicating that stomatal conductance (g) and photosynthetic capacity (A) did not change or change in the same direction. However, δ18 Oc decreased in the control plot (unrelated to δ18 O of precipitation) but not in the thinned plot, suggesting a relative increase of temperature and irradiance and/or a decrease of air humidity after reducing the density consistent with an increase in A, g and BAI. As WUEi did not increase in the thinned plot, faster growth in this plot was caused by higher abundance of resources per tree. The trend of WUEi in both plots indicated low-moderate CO2 -induced improvements. Thinning might be a useful adaptation measure against climate change in these plantations reducing their vulnerability to droughts. However, because WUEi was not affected, the positive growth response might be limited if droughts and warming continue and certain thresholds are exceeded. [Copyright &y& Elsevier]- Published
- 2010
- Full Text
- View/download PDF
12. Variability of latewood-widths and -stable isotope ratios in a sessile oak tree (Quercus petraea (Matt.) Liebl.).
- Author
-
Weigl, Martin, Grabner, Michael, Helle, Gerhard, Schleser, Gerhard H., and Wimmer, Rupert
- Subjects
STABLE isotopes ,OAK ,DURMAST oak ,ECONOMIC trends ,TREES - Abstract
Abstract: Axial variation of latewood-widths and -stable isotopes (δ
13 C and δ18 O) of a single sessile oak tree (Quercus petraea (Matt.) Liebl.) was analyzed. The influence of sampling height was found to be weak for both, latewood-widths and -stable isotopes in the latewood. The observed trends with stem-height show clearly that possible effects due to cambial aging are overrated by annual effects. In addition, relations between samples from different stem-heights are strong for identical calendar years while they are poor for identical cambial age. This indicates that samples from both, living trees and historical wood can be taken from any height position of a trunk or beam as long they are free from anatomical abnormities. Simple correlation and Gleichläufigkeit were used for validation. [Copyright &y& Elsevier]- Published
- 2007
- Full Text
- View/download PDF
13. An annual-resolution stable isotope record from Swiss subfossil pine trees growing in the late Glacial.
- Author
-
Pauly, Maren, Helle, Gerhard, Büntgen, Ulf, Wacker, Lukas, Treydte, Kerstin, Reinig, Frederick, Turney, Chris, Nievergelt, Daniel, Kromer, Bernd, Friedrich, Michael, Sookdeo, Adam, Heinrich, Ingo, Riedel, Frank, Balting, Daniel, and Brauer, Achim
- Subjects
- *
STABLE isotopes , *CLIMATE change , *PINE , *GLACIATION , *OXYGEN isotopes , *ICE cores - Abstract
Previous studies have suggested that the Late Glacial period (LG; ∼14 600–11 700 cal BP) was characterised by abrupt and extreme climate variability over the European sector of the North Atlantic. The limited number of precisely dated, high-resolution proxy records, however, restricts our understanding of climate dynamics through the LG. Here, we present the first annually-resolved tree-cellulose stable oxygen and carbon isotope chronology (δ18O tree , δ13C tree) covering the LG between ∼14 050 and 12 795 cal BP, generated from a Swiss pine trees (P. sylvestris ; 27 trees, 1255 years). Comparisons of δ18O tree with regional lake and ice core δ18O records reveal that LG climatic changes over the North Atlantic (as recorded by Greenland Stadials and Inter-Stadials) were not all experienced to the same degree in the Swiss trees. Possible explanations include: (1) LG climate oscillations may be less extreme during the summer in Switzerland, (2) tree-ring δ18O may capture local precipitation and humidity changes and/or (3) decayed cellulose and various micro-site conditions may overprint large-scale temperature trends found in other δ18O records. Despite these challenges, our study emphasises the potential to investigate hydroclimate conditions using subfossil pine stable isotopes. • Millennial stable isotope chronologies of δ13C and δ18O from 27 Swiss subfossil pine trees, covering the Late Glacial (∼14 050–12 795 cal BP). • Two extreme δ18O tree depletions parallel North Atlantic 'cool periods' (GI-1c, GS-1), another LG event (GI-1b) is not expressed in δ18O tree. • Trees with less extensive decay have significantly higher inter-isotope (δ18O tree : δ13C tree) correlations. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
14. A novel device for batch-wise isolation of α-cellulose from small-amount wholewood samples.
- Author
-
Wieloch, Thomas, Helle, Gerhard, Heinrich, Ingo, Voigt, Michael, and Schyma, Philipp
- Subjects
CELLULOSE ,STABLE isotopes ,DENDROCLIMATOLOGY ,CHEMICAL processes ,SOLUTION (Chemistry) ,EXTRACTION (Chemistry) - Abstract
Abstract: A novel device for the chemical isolation of α-cellulose from wholewood material of tree rings was designed by the Potsdam Dendro Laboratory. It allows the simultaneous treatment of up to several hundred micro samples. Key features are the batch-wise exchange of the chemical solutions, the reusability of all major parts and the easy and unambiguous labelling of each individual sample. Compared to classical methods labour intensity and running costs are significantly reduced. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
15. Hydroclimatic seasonality recorded by tree ring δ18O signature across a Himalayan altitudinal transect.
- Author
-
Brunello, Camilla Francesca, Andermann, Christoff, Helle, Gerhard, Comiti, Francesco, Tonon, Giustino, Tiwari, Achyut, and Hovius, Niels
- Subjects
- *
TREE-rings , *OXYGEN isotopes , *TREE growth , *ATMOSPHERIC temperature , *HUMIDITY , *STABLE isotopes - Abstract
Water stable isotope ratios of tropical precipitation predominantly reflect moisture source and precipitation intensity. Trees can incorporate the isotopic signals into annual tree-ring cellulose records, permitting reconstruction of the temporal changes of hydroclimate over decades to millennia. This is especially valuable in the Himalayas where the understanding of monsoon dynamics is limited by the lack of a dense and representative observational network. We have analyzed tree ring δ 18 O records from two distinct physiographic sites along the upper Kali Gandaki valley in the central Nepal Himalayas, representing the wet High-Himalayas and the Trans-Himalayan dryland to the north. Empirical correlations and regression analyses were compared to an in-situ calibrated oxygen isotope fractionation model, exploring the relationships between tree ring δ 18 O and seasonal-mean variability of hydroclimatic forcing at the different locations. For this purpose, gridded precipitation data from the Asian rain gauge dataset APHRODITE, as well as high resolution onsite observations (relative humidity, air temperature, δ 18 O of precipitation and radial tree growth) were used. We found that two distinct sets of meteorological values, reflecting pre-monsoon and monsoon conditions, are needed to reproduce the measured tree ring δ 18 O values from the High-Himalayan site, but that a single set of monsoonal values performs best for the Trans-Himalayan site. We conclude that Trans-Himalayan trees capture long-term changes in strength of the Indian summer monsoon. In contrast, High-Himalayan tree ring δ 18 O records a more complex hydro-climatic signal reflecting both pre-monsoon and monsoon seasons with very contrasting isotopic signatures of precipitation. This difference in the two hydroclimatic proxy records offers an opportunity to reconstruct first-order hydroclimate conditions, such as local precipitation rates, and to gain new insights into monsoon timing and seasonal water source determination across the Himalayan orographic region. • Hydroclimate seasonality is preserved in tree ring δ 18 O from the Central Himalayas. • A fractionation model confirms relationships from empirical correlation analyses. • High-Himalayan tree ring δ 18 O compounds pre- and monsoon signals • Trans-Himalayan tree ring δ 18 O only contains monsoon signal. • At different locations across the Himalayas, different climate features are recorded. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
16. Late Holocene relative humidity history on the southeastern Tibetan plateau inferred from a tree-ring δ18O record: Recent decrease and conditions during the last 1500 years.
- Author
-
Grießinger, Jussi, Bräuning, Achim, Helle, Gerhard, Hochreuther, Philipp, and Schleser, Gerhard
- Subjects
- *
HOLOCENE paleoclimatology , *HUMIDITY , *TREE-rings , *CLIMATE change , *TEMPERATURE effect - Abstract
In recent decades, the Tibetan plateau (TP) experienced a distinctive temperature increase, with fundamental consequences for the hydrological system. As meteorological time-series extending back more than 60 years are scarce, there is a strong need for proxy data providing insight into the regional hydroclimatic history as well as the long-term variability. Within this study, a recently developed annually resolved 1500 year-long tree-ring stable oxygen isotope (δ 18 O) time from the southeastern TP is presented. Climate–proxy relationships reveal a strong impact of relative humidity (rH) during the summer months (May to September) on tree-ring δ 18 O, explaining around 45% of its variance. The derived reconstruction of relative humidity reveals a recent trend towards drier conditions on the TP. However, the present low rH level is not unprecedented in regard to the last 1500 years. In comparison to recent climate conditions, the Medieval Warm Period (MWP) was characterized by more stable conditions with higher humidity values. Hydroclimatic conditions during the Little Ice Age (LIA) suggest a contrasting two-phased period, with a clear shift from drier conditions prevailing between 1400 and 1650 AD to more humid conditions since the second half of the 17th century. Comparisons with other local proxies from lake levels and Pollen data from the southern part of the Tibetan plateau indicate a common regional climate forcing during the MWP and the LIA which can be related to changes in summer monsoon activity. However, the strength of the distinct dryness trend during the 20th century seems unique. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
17. Climate sensitivity and parameter coherency in annually resolved δ13C and δ18O from Pinus uncinata tree-ring data in the Spanish Pyrenees.
- Author
-
Konter, Oliver, Holzkämper, Steffen, Helle, Gerhard, Büntgen, Ulf, Saurer, Matthias, and Esper, Jan
- Subjects
- *
CLIMATE change , *PINE , *OXYGEN isotopes , *DATA analysis , *TEMPERATURE effect - Abstract
Abstract: We explore the 20th century climate sensitivity of annually resolved carbon and oxygen isotope ratios in five Pinus uncinata individuals from the upper treeline in ~2400m asl of the Spanish Pyrenees. Time series of δ13C and δ18O are calibrated against temperature, precipitation, and drought indices over the period 1901–2009. Negative correlations of δ13C with summer precipitation and drought indices, as well as positive correlations with summer temperatures, confirm previous evidence from similar habitats in the Pyrenees. In contrast to this summer climate signal in the carbon isotopes, the δ18O record reveals mainly negative correlations with spring precipitation and drought. We explore the coherence between δ13C and δ18O time series derived from individual trees and assess the influence of widely applied δ13C correction procedures on the climate signal strength. Spatial correlation patterns and decomposition of the time series into high- and low-frequency components are used to develop a calibration setup for carbon and oxygen isotope ratios, which will improve long-term climate reconstructions in a region, where classical tree-ring width and density data are limited. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
18. Pooled versus separate measurements of tree-ring stable isotopes
- Author
-
Dorado Liñán, Isabel, Gutiérrez, Emilia, Helle, Gerhard, Heinrich, Ingo, Andreu-Hayles, Laia, Planells, Octavi, Leuenberger, Markus, Bürger, Carmen, and Schleser, Gerhard
- Subjects
- *
STABLE isotopes , *TREE-rings , *PALEOCLIMATOLOGY , *ECOPHYSIOLOGY , *CARBON compounds , *DENDROCHRONOLOGY , *OXYGEN , *DATA analysis - Abstract
Abstract: δ 13C and δ 18O of tree rings contain time integrated information about the environmental conditions weighted by seasonal growth dynamics and are well established as sources of palaeoclimatic and ecophysiological data. Annually resolved isotope chronologies are frequently produced by pooling dated growth rings from several trees prior to the isotopic analyses. This procedure has the advantage of saving time and resources, but precludes from defining the isotopic error or statistical uncertainty related to the inter-tree variability. Up to now only a few studies have compared isotope series from pooled tree rings with isotopic measurements from individual trees. We tested whether or not the δ 13C and the δ 18O chronologies derived from pooled and from individual tree rings display significant differences at two locations from the Iberian Peninsula to assess advantages and constraints of both methodologies. The comparisons along the period 1900–2003 reveal a good agreement between pooled chronologies and the two mean master series which were created by averaging raw individual values (Mean) or by generating a mass calibrated mean (MassC). In most of the cases, pooled chronologies show high synchronicity with averaged individual samples at interannual scale but some differences also show up especially when comparing δ 18O decadal to multi-decadal variations. Moreover, differences in the first order autocorrelation among individuals may be obscured by pooling strategies. The lack of replication of pooled chronologies prevents detection of a bias due to a higher mass contribution of one sample but uncertainties associated with the analytical process itself, as sample inhomogeneity, seems to account for the observed differences. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
19. Characteristics of radial growth and stable isotopes in a single oak tree to be used in climate studies
- Author
-
Weigl, Martin, Grabner, Michael, Helle, Gerhard, Schleser, Gerhard H., and Wimmer, Rupert
- Subjects
- *
STABLE isotopes , *LINEAR free energy relationship , *CONDITIONS & laws of chemical reaction , *AUTOCORRELATION (Statistics) , *PROBABILITY theory , *MATHEMATICAL statistics - Abstract
Abstract: In this study we have analyzed the variability of tree-ring widths and stable isotopes (δ 13C and δ 18O) of a single sessile oak tree (Quercus petraea (Matt.) Liebl.) since these parameters are critical in reconstructing the environment, particularly climatic conditions. Tree rings were separated into early- and latewood (EW t ; LW t ), tree ring (TR t ), and transfer tree ring (TTRt, the latter being the latewood plus the earlywood of the subsequent year. Mean sensitivity, simple correlation, partial correlation and autocorrelation analyses were applied to describe data and relationships. Although this research focused on a single tree, the results compared well with average site data. Widths and δ 18O values showed generally low autocorrelation for all tree-ring components, whereas δ 13C revealed highly significant autocorrelations for most tree-ring components. Mean sensitivity of the standardized values turned out to be high for δ 18O, marginally lower for width and the lowest for δ 13C. Correlation analyses have proven that the relationships within the tree-ring widths or within the isotope parameters are much stronger than across widths and isotope parameters. The study demonstrates the unique potential of all measured tree-ring data to be used as climate proxies. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
20. Changes in El Niño – Southern Oscillation (ENSO) conditions during the Greenland Stadial 1 (GS-1) chronozone revealed by New Zealand tree-rings.
- Author
-
Palmer, Jonathan G., Turney, Chris S.M., Cook, Edward R., Fenwick, Pavla, Thomas, Zoë, Helle, Gerhard, Jones, Richard, Clement, Amy, Hogg, Alan, Southon, John, Bronk Ramsey, Christopher, Staff, Richard, Muscheler, Raimund, Corrège, Thierry, and Hua, Quan
- Subjects
- *
TREE-rings , *YOUNGER Dryas , *KAURI , *RADIOCARBON dating , *WAVELETS (Mathematics) ,EL Nino - Abstract
The warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in Greenland (Greenland Stadial 1 or GS-1) and Europe (Younger Dryas Stadial or YD). This reversal to glacial-like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain. Whilst the wider Atlantic region has a network of high-resolution proxy records spanning GS-1, the Pacific Ocean suffers from a scarcity of sub-decadally resolved sequences. Here we report the results from an investigation into a tree-ring chronology from northern New Zealand aimed at addressing the paucity of data. The conifer tree species kauri ( Agathis australis ) is known from contemporary studies to be sensitive to regional climate changes. An analysis of a ‘historic’ 452-year kauri chronology confirms a tropical-Pacific teleconnection via the El Niño – Southern Oscillation (ENSO). We then focus our study on a 1010-year sub-fossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring-width downturn between ∼12,500 and 12,380 cal BP within GS-1. Wavelet analysis shows a marked increase in ENSO-like periodicities occurring after the downturn event. Comparison to low- and mid-latitude Pacific records suggests a coherency with ENSO and Southern Hemisphere atmospheric circulation change during this period. The driver(s) for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and/or increased expression of ENSO across the mid-latitudes of the Pacific, seemingly independent of the Atlantic and polar regions. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
21. Multiple tree-ring chronologies (ring width, δ13C and δ18O) reveal dry and rainy season signals of rainfall in Indonesia.
- Author
-
Schollaen, Karina, Heinrich, Ingo, Neuwirth, Burkhard, Krusic, Paul J., D'Arrigo, Rosanne D., Karyanto, Oka, and Helle, Gerhard
- Subjects
- *
RAINFALL , *TREE-rings , *CHRONOLOGY , *MONSOONS , *RAIN forests - Abstract
Abstract: Climatic hazards, such as severe droughts and floods, affect extensive areas across monsoon Asia and can have profound impacts on the populations of that region. The area surrounding Indonesia, including large portions of the eastern Indian Ocean and Java Sea, plays a key role in the global climate system because of the enormous heat and moisture exchange that occurs between the ocean and atmosphere there. Here, we evaluate the influence of rainfall variability on multiple tree-ring parameters of teak (Tectona grandis) trees growing in a lowland rain forest in Central Java (Indonesia). We assess the potential of, annually resolved, tree-ring width, stable carbon (δ13C) and oxygen (δ18O) isotope records to improve our understanding of the Asian monsoon variability. Climate response analysis with regional, monthly rainfall data reveals that all three tree-ring parameters are significantly correlated to rainfall, albeit during different monsoon seasons. Precipitation in the beginning of the rainy season (Sep–Nov) is important for tree-ring width, confirming previous studies. Compared to ring width, the stable isotope records possess a higher degree of common signal, especially during portions of the peak rainy season (δ13C: Dec–May; δ18O: Nov–Feb) and are negatively correlated to rainfall. In addition, tree-ring δ18O also responds positively to peak dry season rainfall, although the δ18O rainy season signal is stronger and more time-stable. The correlations of opposite sign reflect the distinct seasonal contrast of the δ18O signatures in rainfall (18OPre) during the dry (18O-enriched rain) and rainy (18O-depleted rain) seasons. This difference in 18OPre signal reflects the combination of two signals in the annual tree-ring δ18O record. Highly resolved intra-annual δ18O isotope analyses suggest that the signals of dry and rainy season can be distinguished clearly. Thereby reconstructions can improve our understanding of variations and trends of the hydrological cycle over the Indonesian archipelago. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
22. Impact of climate and CO2 on a millennium-long tree-ring carbon isotope record
- Author
-
Treydte, Kerstin S., Frank, David C., Saurer, Matthias, Helle, Gerhard, Schleser, Gerhard H., and Esper, Jan
- Subjects
- *
VEGETATION & climate , *EFFECT of carbon dioxide on plants , *CLIMATE change , *JUNIPERS , *TREE-rings , *RADIOCARBON dating , *CARBON isotopes - Abstract
Abstract: We present one millennium-long (1171-year), and three 100 year long annually resolved δ13C tree-ring chronologies from ecologically varying Juniperus stands in the Karakorum Mountains (northern Pakistan), and evaluate their response to climatic and atmospheric CO2 changes. All δ13C records show a gradual decrease since the beginning of the 19th century, which is commonly associated with a depletion of atmospheric δ13C due to fossil fuel burning. Climate calibration of high-frequency δ13C variations indicates a pronounced summer temperature signal for all sites. The low-frequency component of the same records, however, deviates from long-term temperature trends, even after correction for changes in anthropogenic CO2. We hypothesize that these high-elevation trees show a response to both climate and elevated atmospheric CO2 concentration and the latter might explain the offset with target temperature data. We applied several corrections to tree-ring δ13C records, considering a range of potential CO2 discrimination changes over the past 150 years and calculated the goodness of fit with the target via calibration/verification tests (R 2, residual trend, and Durbin–Watson statistics). These tests revealed that at our sites, carbon isotope fixation on longer timescales is affected by increasing atmospheric CO2 concentrations at a discrimination rate of about 0.012‰/ppmv. Although this statistically derived value may be site related, our findings have implications for the interpretation of any long-term trends in climate reconstructions using tree-ring δ13C, as we demonstrate with our millennium-long δ13C Karakorum record. While we find indications for warmth during the Medieval Warm Period (higher than today’s mean summer temperature), we also show that the low-frequency temperature pattern critically depends on the correction applied. Patterns of long-term climate variation, including the Medieval Warm Period, the Little Ice Age, and 20th century warmth are most similar to existing evidence when a strong influence of increased atmospheric CO2 on plant physiology is assumed. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
23. Will climate change shift carbon allocation and stem hydraulics? Insights on a systemic view of carbon- and water-related wood traits in an anysohydric tropical tree species (Hymenaea courbaril, Leguminosae).
- Author
-
Macieira, Bernardo Pretti Becacici, Locosselli, Giuliano Maselli, Buckeridge, Marcos Silveira, Jardim, Vinícius Carvalho, Krottenthaler, Stefan, Anhuf, Dieter, Helle, Gerhard, Cuzzuol, Geraldo Rogério Faustini, and Ceccantini, Gregório
- Subjects
- *
ATMOSPHERIC carbon dioxide , *LEGUMES , *CLIMATE change , *CARBON cycle , *HYDRAULICS , *XYLOSE , *TREE-rings - Abstract
• Evaluating trees' responses to climate change can be challenging. • We propose the use of correlation networks to aid the integration of wood traits. • Trees coordinate carbon and water related traits along a tropical climate gradient. • Correlation networks revealed trade-offs that reflects carbon metabolic pathways. • Cell-wall xylose and mannose are central in trees responses to climate variability. Tropical forests uptake more atmospheric CO 2 and transpire more water than any other forest in the world and are critical components of the global carbon and hydrological cycles. Both cycles depend to a great extent on the carbon and water balance of individual trees. Such adjustments are usually evaluated through well-established and newly-emerging traits but integrating them for a systemic understanding of trees' responses to climate change can be challenging. We propose using complex correlation networks to integrate and understand how trees coordinate water- and carbon-related traits under changing climate conditions. We built a correlation network based on 20 traits measured in the wood of Hymenaea courbaril (Leguminosae) trees, a species known for its extreme anisohydric water-use strategy, sampled along a climate gradient in Southeastern Brazil. Intercellular to ambient CO 2 concentrations ratio (c i /c a , estimated from tree-ring δ13C) is a central network trait for being coordinated with several hydraulic and carbon allocation traits. Trees of H. courbaril coordinate these traits along the climate gradient, favoring high c i /c a under warm and dry conditions. A high c i /c a is only possible through a consistent water supply provided by wider vessels together with the investment on soluble sugars, at the detriment of starch, likely for hydraulic maintenance. Trees also favor heat resistance by investing in cell-wall xylose, another central network trait, from xyloglucans and xylans, at the expense of mannose from glucomannans. Such trade-offs within, and between, structural and non-structural carbon allocation reflect well-known metabolic pathways in plants. In summary, this systemic approach confirms previously reported patterns on leaf physiology, stem hydraulics and carbon adjustments while bringing to light the previously unreported role of cell-wall composition and its fine adjustments to cope with climate change. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.