110 results on '"Dendrochronology -- Research"'
Search Results
2. Eastern white pine and eastern hemlock growth: possible tradeoffs in response of canopy trees to climate
- Author
-
Stern, Rebecca L., Schaberg, Paul G., Rayback, Shelly A., Murakami, Paula F., Hansen, Christopher F., and Hawley, Gary J.
- Subjects
Eastern hemlock -- Environmental aspects ,Global temperature changes -- Environmental aspects ,Dendrochronology -- Research ,White pine -- Environmental aspects ,Forestry research ,Earth sciences - Abstract
A warming climate and extended growing season may confer competitive advantages to temperate conifers that can photosynthesize across seasons. Whether this potential translates into increased growth is unclear, as is whether pollution could constrain growth. We examined two temperate conifers--eastern white pine (Pinus strobus L.) and eastern hemlock (Tsuga canadensis (L.) Carriere)--and analyzed associations between growth (476 trees in 23 plots) and numerous factors, including climate and pollutant deposition variables. Both species exhibited increasing growth over time and eastern white pine showed greater maximum growth. Higher spring temperatures were associated with greater growth for both species, as were higher autumnal temperatures for eastern hemlock. Negative correlations were observed with previous year (eastern hemlock) and current year (eastern white pine) summer temperatures. Spring and summer moisture availability were positively correlated with growth for eastern white pine throughout its chronology, whereas for hemlock, correlations with moisture shifted from being significant with current year's growth to previous year's growth over time. The growth of these temperate conifers might benefit from higher spring (both species) and fall (eastern hemlock) temperatures, though this could be offset by reductions in growth associated with hotter, drier summers. Key words: dendrochronology, temperate conifers, temperature, moisture, climate change. Un climat plus chaud et une saison de croissance plus longue pourrait conferer des avantages competitifs aux coniferes de la zone temperee chez qui la photosynthese peut se poursuivre en toute saison. Il n'est pas clair si cette possibilite pourrait se traduire par une croissance accrue et de meme si la pollution pourrait limiter la croissance. Nous avons etudie deux coniferes de la zone temperee: le pin blanc (Pinus strobus L.) et la pruche du Canada (Tsuga canadensis (L.) Carriere), et nous avons analyse les liens entre la croissance (476 arbres dans 23 places echantillons) et plusieurs facteurs, incluant des variables liees au climat et aux retombees de polluants. Les deux especes ont augmente leur croissance avec le temps et le pin blanc a connu la croissance maximum la plus elevee. Les temperatures printanieres elevees etaient associees a une plus forte croissance chez les deux especes, ainsi que les temperatures automnales elevees dans le cas de la pruche du Canada. Des correlations negatives ont ete observees avec les temperatures estivales de l'annee precedente (pruche du Canada) et de l'annee en cours (pin blanc). La disponibilite d'humidite au printemps et a l'ete etait positivement correlee avec la croissance du pin blanc tout au long de sa chronologie, tandis que dans le cas de la pruche du Canada les correlations avec l'humidite allaient avec le temps de significatives avec la croissance de l'annee en cours a celle de l'annee precedente. La croissance de ces coniferes de la zone temperee pourrait beneficier de temperatures plus chaudes au printemps (les deux especes) et a l'automne (pruche du Canada), bien que cela puisse etre compense par des reductions de croissance associees a des etes plus chauds et plus secs. [Traduit par la Redaction] Mots-cles: dendrochronologie, coniferes de la zone temperee, temperature, humidite, changement climatique., Introduction Forest composition and growth may shift as the suitability of habitats for component tree species shifts with climate change (Prasad et al. 2007--ongoing). For species in temperate forest communities [...]
- Published
- 2021
- Full Text
- View/download PDF
3. New Forestry Study Results Reported from Harbin Normal University (Reconstruction of Ndvi Based On larix Gmelinii Tree-rings During June-september 1759-2021)
- Subjects
Atmospheric circulation -- Research ,Dendrochronology -- Research ,Forests and forestry -- Research ,Health ,Science and technology - Abstract
2024 AUG 2 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- Fresh data on Science - Forestry are presented in a new report. According to news [...]
- Published
- 2024
4. Europe's air is the driest in 400 years
- Published
- 2023
5. Dendroclimatic investigations and cross-dating in the 1700s: the tree-ring investigations of Johan Leche (1704-1764) in southwestern Finland
- Author
-
Norrgard, Stefan and Helama, Samuli
- Subjects
Dendroclimatology -- Research ,Archaeological dating -- Methods ,Droughts -- Research -- Finland ,Dendrochronology -- Research ,Tree-rings -- Research ,College teachers -- Works ,Earth sciences - Abstract
Cross-dating is considered one of the most important principles of dendrochronology. The first known cross-dating attempts, conducted between the years 1737 and 1783 by independent researchers in France, Germany, and Sweden, were related to the identification of growth rings believed to have formed during the harsh winter of 1708-1709. In this paper, we present a novel perspective on the birth of dendrochronology and cross-dating in the 1700s. We focus on the ideas and experimental studies of one of the lesser known pioneers, Johan Leche (1704-1764), the Professor of Medicine at the Royal Academy (Turku, Finland). Instead of winter harshness, Leche was fascinated by the drought that killed and damaged several trees and tree species in the summer of 1757. Leche conducted several dendrochronological and field experiments described only in his unpublished manuscript filed in the National Archives in Sweden. Reviewing Leche's measurements of ring-width series of multiple radii and his comparisons between the radii, it seems only fair to include him in the long list of natural historians who made important contributions to the field ofdendrochronology. His manuscript was never published, which is why Leche's dendrochronological experiments and recommendations never reached a wider audience. Key words: tree-ring research, dendrochronology, dendroclimatology, cross-dating, history of science. La datation croisee est consideree comme un des plus importants principes de la dendrochronologie. Les premieres tentatives connues de datation croisee, effectuees entre les annees 1737 et 1783 par des chercheurs independants en France, en Allemagne et en Suede, etaient reliees a l'identification de cernes de croissance qu'on croyait avoir ete formes durant le rude hiver de 1708-1709. Dans cet article, nous presentons une nouvelle perspective sur la naissance de la dendrochronologie et la datation croisee au cours des annees 1700. Nous mettons l'accent sur les idees et les etudes experimentales menees par un des pionniers moins connus, Johan Leche (1704-1764), le professeur de medecine a l'Academie royale (Turku, Finlande). Au lieu de la severite de l'hiver, Leche etait fascine par la secheresse qui avait tue et endommage plusieurs arbres et especes d'arbres a l'ete de 1757. Leche realisa plusieurs etudes dendrochronologiques et experiences sur le terrain decrites seulement dans son manuscrit non publie depose dans les Archives nationales en Suede. Lorsqu'on examine les mesures de Leche qui portent sur les series dendrochronologiques de multiples rayons, il semble seulement juste de l'inclure dans la longue liste d'historiens de la nature qui ont apporte d'importantes contributions au domaine de la dendrochronologie. Son manuscrit n'a jamais ete publie, ce qui explique pourquoi les travaux de Leche en dendrochronologie et ses recommandations n'ont jamais rejoint une plus large audience. [Traduit par la Redaction] Mots-cles : recherche sur les cernes des arbres, dendrochronologie, dendroclimatologie, datation croisee, histoire des sciences., Introduction Climatic change has over recent decades led to a growing need to better understand historical climate variability. For this purpose, local and national archives are continuously and systematically scrutinized [...]
- Published
- 2021
- Full Text
- View/download PDF
6. Reports Outline Botany Study Results from University of Murcia (Expanding dendrochronology to palms: A Bayesian approach to the visual estimate of a palm tree age in urban and natural spaces)
- Subjects
Archaeological dating -- Research ,Dendrochronology -- Research ,Biological sciences ,Health - Abstract
2024 JAN 2 (NewsRx) -- By a News Reporter-Staff News Editor at Life Science Weekly -- New research on botany is the subject of a new report. According to news [...]
- Published
- 2024
7. Recent Studies from Wuhan University Add New Data to Information Science (Improving Signal Strength of Tree Rings for Paleoclimate Reconstruction By Micro-hyperspectral Imaging)
- Subjects
Dendroclimatology -- Research ,Dendrochronology -- Research ,Information science -- Research ,Climatic changes -- Research ,Computers - Abstract
2023 DEC 12 (VerticalNews) -- By a News Reporter-Staff News Editor at Information Technology Newsweekly -- Current study results on Information Technology - Information Science have been published. According to [...]
- Published
- 2023
8. Comparaison de deux approches de mesure de cernes utilisant les outils systeme d'information geographique (SIG) sur des images a haute resolution de bois tropicaux
- Author
-
Ilunga, Cedric, Mbayu, Faustin, Sabongo, Prosper, Ebuy, Jerome, and Arenas-Castro, Salvador
- Subjects
Geographic information systems -- Usage ,Dendrochronology -- Research ,Forestry research ,Tree rings -- Environmental aspects -- Physiological aspects ,Forests ,Anopheles ,Geographic information system ,Earth sciences - Abstract
Using geographic information system (GIS) tools for dendrochronological purposes offers an excellent opportunity to develop better growth ring analyses, especially when dealing with tropical forests where growth ring analysis technics are seemingly complex and time-consuming. In this study, two different approaches for ring width measurements were compared using the GIS application ArcMap for increment core and wood stick sampling simulations. Results based on two tropical tree species (Milicia excelsa (Welw.) C.C. Berg and Pericopsis elata (Harms) Meeuwen) showed no statistical differences between the two approaches tested. Nevertheless, series of measures obtained with both approaches do not totally correspond at a 0.05 mm threshold with Bland-Altman's graphic technics. Overall, statistical analyses of chronologies from the different series favor implementation of the increment core approach while using a mosaic of digital images of the whole radial section of the wood disk. Based on the methods and approaches used here, it would be worth developing diametric and areal growth estimation technics for disk type samples. [Translated by the Journal]Key words: growth ring measurements, geographic information system (GIS), digital images, Milicia excelsa, Pericopsis elata.L'utilisation des outils systeme d'information geographique (SIG) en dendrochronologie offre une excellente opportunite de developper davantage les analyses de cernes, notamment dans le contexte des forets tropicales ou les techniques d'analyses de cernes sont reputees compliquees et fastidieuses. Dans cette etude, deux approches de mesure de largeurs de cernes ont ete comparees en faisant une simulation de l'echantillonnage de bois en << carotte >> et en << barreau >> a l'aide du logiciel SIG ArcMap. Les resultats de l'etude bases sur deux especes d'arbres tropicaux (Milicia excelsa (Welw.) C.C. Berg et Pericopsis elata (Harms) Meeuwen) ont montre que les mesures de deux approches utilisees ne sont pas statistiquement differentes l'une de l'autre. Neanmoins, les series de mesures obtenues par les deux voies ne sont pas totalement concordantes au seuil de 0,05 mm par la technique graphique de Bland-Altman. Dans l'ensemble, les statistiques de chronologies calculees sur les differentes series suggerent plus la mise en oeuvre de mesure par l'approche << carotte >>, tout en utilisant une mosaique d'images numeriques de la section transversale complete de la rondelle. En s'inspirant de la methode et des approches utilisees, il serait interessant de developper les techniques d'estimation de croissance diametrique et de surfaces avec des echantillons de type << disque >>.Mots-cles : mesures de cernes, systeme d'information geographique (SIG), images numeriques, Milicia excelsa, Pericopsis elata., IntroductionLa dendrochronologie compte, a l'heure actuelle, des applications dans divers domaines. Dans la recherche forestiere, cette discipline est devenue de plus en plus essentielle pour comprendre les effets de facteurs [...]
- Published
- 2018
- Full Text
- View/download PDF
9. Alabama A&M University Researcher Details Research in Plant Biology (The Relationships between Climate, Tree-Ring Growth, and Cone Production in Longleaf Pine)
- Subjects
Ecosystems -- Research ,Dendrochronology -- Research ,Climate -- Research ,Plant physiology -- Research ,Biological sciences ,Health - Abstract
2023 MAY 16 (NewsRx) -- By a News Reporter-Staff News Editor at Life Science Weekly -- Investigators discuss new findings in plant biology. According to news reporting out of Normal, [...]
- Published
- 2023
10. Reports Outline Physical Geography Findings from University of Idaho (The Longleaf Tree-ring Network: Reviewing and Expanding the Utility of Pinus Palustris Mill. Dendrochronological Data)
- Subjects
Longleaf pine -- Research ,Dendrochronology -- Research ,Forestry research ,Health ,Science and technology - Abstract
2023 FEB 10 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- Investigators discuss new findings in Environment - Physical Geography. According to news reporting out of [...]
- Published
- 2023
11. Nonstationary temporal response of mountain hemlock growth to climatic variability in the North Cascade range, Washington, USA
- Author
-
Marcinkowski, Kailey, Peterson, David L., and Ettl, Gregory J.
- Subjects
Cascade Range -- Natural history ,Dendrochronology -- Research ,Climate cycles -- Research ,Global temperature changes -- Research ,Hemlocks (Trees) -- Environmental aspects -- Growth ,Plant growth -- Environmental aspects ,Company growth ,Earth sciences - Abstract
A stationary response of tree radial growth to climatic variables is assumed as a basis for climatic reconstructions and future growth projections in response to climate change. Mountain hemlock (Tsuga mertensiana (Bong.) Carriere) trees on the western slopes of the North Cascade Range (Washington, USA) were examined for stability in growth response to climatic influences at a small spatial scale. Moving correlation functions demonstrate that climate-growth interactions are nonstationary over time, alternating between periods of significant and nonsignificant responses. Correlations between growth and winter precipitation have weakened, becoming statistically insignificant in the last decade, but correlations with spring temperature and previous-year summer temperature have strengthened, becoming statistically significant. The Pacific Decadal Oscillation influences patterns in climate-growth correlations but does not seem to account for the most recent changes in correlation strength. At an interannual scale, growth differs between El Nino Southern Oscillation phases, specifically between El Nino and La Nina years and between La Nina and neutral phase years. The variability in growth response to climate at interannual and interdecadal time frames, especially with the climate changes emerging in recent decades, will challenge the reliability and accuracy of reconstruction and predictive models. Key words: dendrochronology, mountain hemlock, North Cascades, limiting factors, climate. A la base des reconstitutions du climat et des projections de la croissance future en reaction aux changements climatiques, on assume que la reaction de la croissance aux variables climatiques est stationnaire. Des tiges de pruche subalpine (Tsuga mertensiana (Bong.) Carriere) sur les pentes occidentales de la section nord de la chaine des Cascades (Washington, E.-U.) ont ete examinees a petite echelle pour determiner la stabilite de leur croissance en reaction aux influences du climat. Des fonctions de correlation mobile demontrent que les interactions entre la croissance et le climat ne sont pas stationnaires dans le temps : elles alternent entre des periodes ou la reaction de la croissance est significative et des periodes ou elle ne l'est pas. Les correlations entre la croissance et les precipitations hivernales se sont estompees pour devenir statistiquement non significatives durant la derniere decennie alors que les correlations avec la temperature printaniere et la temperature estivale de l'annee precedente se sont renforcees et sont devenues statistiquement significatives. L'oscillation decennale du Pacifique influence l'allure des correlations entre le climat et la croissance mais ne semble pas expliquer les plus recents changements dans la force des correlations. Sur une base interannuelle, la croissance differe entre les phases de l'oscillation australe El Nino, specifiquement entre les annees El Nino et La Nina et entre les annees La Nina et en phase neutre. La variabilite de la reaction de la croissance au climat sur une base interannuelle et interdecennale, particulierement avec les changements qui sont apparus au cours des dernieres decennies, vont remettre en question la fiabilite et la precision des reconstitutions et des modeles de prevision. [Traduit par la Redaction] Mots-cles: dendrochronologie, pruche subalpine, section nord de la chaine des Cascades, facteurs limitants, climat., Introduction Forest environments can often be classified on a gradient from energy limited, in which growth is influenced by climatic factors such as light, temperature, or length of growing season, [...]
- Published
- 2015
- Full Text
- View/download PDF
12. Can scar-based fire history reconstructions be biased? An experimental study in boreal Scots pine
- Author
-
Piha, Aura, Kuuluvainen, Timo, Lindberg, Henrik, and Vanha-Majamaa, Ilkka
- Subjects
Dendrochronology -- Research ,Pine -- Environmental aspects -- Health aspects ,Wildfires -- Environmental aspects -- Health aspects ,Earth sciences - Abstract
Determining forest fire history is commonly based on fire scar dating with dendrochronological methods. We used an experimental setup to investigate the impacts of low-intensity prescribed fire on fire scar formation 8 years after fire in 12 young managed Scots pine (Pinus sylvestris L.) stands. Five stands were between 30 and 35 years old and seven were 45 years old at the time of burning. A total of 217 fire scars were recorded in 142 trees. The number of separate scars per tree originating from a single fire ranged from 1 to 6, with 67% of the trees having just one scar. The proportion of fire-scarred trees out of all trees per plot ranged from 0% to 30%, averaging 16.5% in young stands and 2.8% in older stands. Four of the 12 burned plots did not have any trees with fire scars, and these were all in the older age group. This means that in the older stands, in only three of seven plots (43%) did the fire leave scars from which fire can potentially be detected and dated afterwards. Our results suggest that fire scar dating in Scots pine dominated forests may underestimate fire frequency, area, and the importance of historically common low-intensity surface fires in dendrochronological reconstructions of past fire histories. Resume: L'historique des feux de foret est generalement determine a l'aide de methodes dendrochronologiques en s'appuyant sur la datation des cicatrices de feu. Nous avons utilise un dispositif experimental pour etudier les impacts d'un brulage dirige de faible intensite sur la formation des cicatrices de feu huit ans apres un feu dans 12 jeunes peuplements amenages de pin sylvestre (Pinus sylvestris L.). Cinq peuplements avaient entre 30 et 35 ans et sept autres avaient 45 ans au moment du brulage. Au total, 217 cicatrices de feu ont ete denombrees sur 142 arbres. Le nombre de cicatrices distinctes par arbre resultant d'un seul feu variait d'une a six cicatrices alors que 67 % des arbres avaient seulement une cicatrice. Dans les parcelles, la proportion des arbres avec des cicatrices de feu variait de 0 a 30 %, soit en moyenne 16,5 % dans les jeunes peuplements et 2,8 % dans les peuplements plus vieux. Parmi les 12 parcelles brulees, quatre parcelles appartenant toutes au plus vieux groupe d'age ne contenaient aucun arbre avec des cicatrices de feu. Cela signifie que, dans les peuplements plus vieux, des cicatrices qui pourront eventuellement servir a detecter et dater le passage du feu ont ete laissees par le feu dans seulement trois (43 %) des sept parcelles. Nos resultats indiquent que la datation des cicatrices de feu dans les forets dominees par le pin sylvestre peut sous-estimer la frequence des feux, ainsi que la superficie et l'importance des feux de surface de faible intensite qui sont survenus frequemment dans le passe. [Traduit par la Redaction], Introduction Fires are considered to play an essential role in the dynamics, structure, and biodiversity of boreal ecosystems (Zackrisson 1977; Esseen et al. 1997; Granstrom 2001). It is currently understood [...]
- Published
- 2013
- Full Text
- View/download PDF
13. Long-term drought sensitivity of trees in second-growth forests in a humid region
- Author
-
Pederson, Neil, Tackett, Kacie, McEwan, Ryan W., Clark, Stacy, Cooper, Adrienne, Brosi, Glade, Eaton, Ray, and Stockwell, R. Drew
- Subjects
Droughts -- Research -- United States ,Dendrochronology -- Research ,Old growth forests -- Research -- United States ,Earth sciences - Abstract
Classical field methods of reconstructing drought using tree rings in humid, temperate regions typically target old trees from drought-prone sites. This approach limits investigators to a handful of species and excludes large amounts of data that might be useful, especially for coverage gaps in large-scale networks. By sampling in more 'typical' forests, network density and species diversity would increase in ways that could potentially improve reconstructions. Ten nonclassical tree-ring chronologies derived from randomly selected trees, trees from logged forests, or both were compared to more classical chronologies and an independent regional drought reconstruction to determine their usefulness for dendrohydroclimatic research. We find that nonclassical chronologies are significantly correlated to classical chronologies and reconstructed drought over the last 2-3 centuries. While nonclassical chronologies have spectral properties similar to those from classical dendroclimatic collections, they do lack spectral power at lower frequencies that are present in the drought reconstruction. Importantly, our results show that tree growth is strongly dependent on moisture availability, even for small, randomly selected trees in cut forests. These results indicate that there could be more data available in areas with few current tree-ring collections for studying climate history and that drought plays an important role in humid forests. Resume: Les methodes de terrain classiques pour reconstituer les periodes de secheresse a l'aide des cernes des arbres dans les regions temperees humides ciblent typiquement les vieux arbres dans les stations sujettes a la secheresse. Cette approche limite les chercheurs a une poignee d'especes et exclut de grandes quantites de donnees qui pourraient etre utiles, particulierement pour les bris de couverture dans les reseaux a grande echelle. En echantillonnant dans des forets plus typiques, la densite des reseaux et la diversite des especes augmenteraient, ce qui pourrait ameliorer les reconstitutions. Dix series dendrochronologiques non classiques derivees d'arbres choisis au hasard, d'arbres provenant de forets coupees, ou des deux, ont ete comparees a des series dendrochronologiques plus classiques et a une reconstitution independante des periodes de secheresse regionale pour determiner leur utilite pour la recherche en dendrohydroclimatologie. Nous avons trouve que les series dendrochronologiques non classiques sont significativement correlees avec les series dendrochronologiques classiques et avec les periodes de secheresse reconstituees au cours des derniers deux a trois siecles. Alors que les series dendrochronologiques non classiques ont des proprietes spectrales semblables a celles des collections dendroclimatiques classiques, elles n'ont pas la puissance spectrale aux frequences plus faibles qui est presente dans la reconstitution des periodes de secheresse. Nos resultats montrent surtout que la croissance des arbres est fortement dependante de l'humidite disponible, meme celle des petits arbres choisis au hasard dans les forets coupees. Ces resultats indiquent que plus de donnees pourraient etre disponibles dans les regions qui comptent actuellement peu de collections dendrochronologiques pour l'etude du climat passe et que la secheresse joue un role important dans les forets humides. [Traduit par la Redaction], Introduction Many classical, tree-ring based drought reconstructions target trees from old-growth forests or forests that are largely undisturbed by human land use. However, the amount of old-growth forest in humid [...]
- Published
- 2012
- Full Text
- View/download PDF
14. MAIDENiso: a multiproxy biophysical model of tree-ring width and oxygen and carbon isotopes
- Author
-
Danis, P.-A., Hatte, C., Misson, L., and Guiot, J.
- Subjects
Environment -- Research ,Dendrochronology -- Research ,Tree-rings -- Analysis ,Earth sciences - Abstract
MAIDENiso is a new version of the process-based biogeochemical model MAIDEN of tree growth. Isotopic modules have been implemented to simulate stable oxygen and carbon isotopes in tree-ring cellulose (TRC). In addition to annual increment biomass, this new model version estimates [d.sup.18]O and [d.sup.13]C associated with the daily amount of carbon allocated to the stem. MAIDENiso only requires daily input data: minimal and maximal air temperatures, amount of precipitation, [CO.sub.2] atmospheric concentration, and [d.sup.13]C in [CO.sub.2]. MAIDENiso simulates tree-ring width, [d.sup.18]O in precipitation [[(d.sup.18]O.sub.P]), [d.sup.18]O in soil water [[(d.sup.18]O.sub.SW]), [d.sup.18]O in xylem water [[(d.sup.18]O.sub.XW]), [d.sup.18]O in cellulose [[(d.sup.18]O.sub.TRC]), and [d.sup.13]C in cellulose [[(d.sup.13]C.sub.TRC]). The model has been calibrated and validated with tree-ring series sampled in the Fontainebleau Forest (France) from 1953 to 2000. We first calibrated several parameters for the 1977-2000 period and then validated it for the independent 1953-1976 period. Over the complete interval (1953-2000), we obtained correlations between observations and simulations above 0.5 for both isotopic series and above 0.65 for tree growth series. An important feature of the model is its ability to simulate not only extreme values of tree growth, such as the effect of 1976 drought, but also its persistence over several years. Resume: MAIDENiso est une nouvelle version du modele MAIDEN des processus biogeochimiques de la croissance d'ar-bres. Des modules isotopiques ont ete ajoutes a ce dernier pour simuler les isotopes stables de l'oxygene et du carbone de la cellulose des cernes (TRC). De plus, de la biomasse annuelle, cette nouvelle version estime [d.sup.18]O et [d.sup.13]C associes a la quantite journalieres de carbone alloue au tronc. MAIDENiso requiert seulement des donnees journalieres de temperatures minimales et maximales de l'air, de precipitations, de la concentration atmospherique en [CO.sub.2] et du [d.sup.13]C du [CO.sub.2]. MAIDE-Niso simule l'epaisseur du cerne d'arbre, [d.sup.18]O des precipitations [[(d.sup.18]O.sub.P]), [d.sup.18]O de l'eau du sol [[(d.sup.18]O.sub.SW]), [d.sup.18]O de l'eau du xylem [[(d.sup.18]O.sub.XW]), [d.sup.18]O de la cellulose [[(d.sup.18]O.sub.TRC]) et [d.sup.13]C de la cellulose [[(d.sup.13]C.sub.TRC]). Le modele a ete calibre et valide avec des series de cernes d'arbres echantillonnees dans la Foret de Fontainebleau (France) de 1953 a 2000. Le modele a ete tout d'a-bord calibre sur la periode 1977-2000 and valide independamment sur la periode 1953-1976. Pour la periode complete (1953-2000), nous avons obtenu des correlations entre observations et simulations superieures a 0,5 pour les deux series isotopiques et superieures a 0,65 pour les series de croissance. Une caracteristique importante du modele est sa capacite a si-muler non seulement les extremes de la croissance, comme l'effet de la secheresse de l'ete 1976, mais aussi sa persistance sur plusieurs annees., Introduction In dendroclimatology, tree-ring width and oxygen and car-bon isotopes in cellulose are used either independently (Libby et al. 1976) or in a multiproxy approach to statistically reconstruct past climatic [...]
- Published
- 2012
- Full Text
- View/download PDF
15. Structural attributes of two old-growth cross timbers stands in Western Arkansas
- Author
-
Bragg, Don C., Stahle, David W., and Cerny, K. Chris
- Subjects
Dendrochronology -- Research ,Timber -- Natural history ,Biological sciences ,Earth sciences - Abstract
Comprised of largely non-commercial, xeric, oak-dominated forests, the Cross Timbers in Arkansas have been heavily altered over the last two centuries, and thus only scattered parcels of old-growth timber remain. We inventoried and mapped two such stands on Fort Chaffee Military Training Center in Sebastian County, Arkansas. The west-facing Christmas Knob site is located on an isolated hill, while the southerly-facing Big Creek Narrows site is on a long, narrow rocky outcrop called Devil's Backbone Ridge. These sites occupied rocky, south- to southwest-facing sandstone-dominated slopes, with primarily post oak (Quercus stellata) and blackjack oak (Q. marilandica) overstories. Post oak dominated the largest size classes at both sites. Increment cores indicated that some post oaks exceeded 200 y of age, and tree-ring dating also confirmed an uneven-aged structure to these stands. Both locations had irregular reverse-J shaped diameter distributions, with gaps, deficiencies, and excesses in larger size classes that often typify old-growth stands. On average, the post oaks at the Big Creek Narrows site were taller, larger in girth, and younger than those on the Christmas Knob site, suggestive of a better quality site at Big Creek. The application of neighborhood density functions on stem maps of both sites found random patterns in tree locations. These stands are very similar in their structure to old-growth examples in other parts of the Cross Timbers ecoregion., INTRODUCTION The Cross Timbers ecoregion occupies southeastern Kansas, eastern and central Oklahoma, and north-central Texas and has been mapped as far east as extreme west-central Arkansas (Bruner, 1931; Rice and [...]
- Published
- 2012
16. Consequences of decreasing the number of cored trees per plot on chronology statistics and climate-growth relationships: a multispecies analysis in a temperate climate
- Author
-
Merian, Pierre and Lebourgeois, Francois
- Subjects
Dendrochronology -- Research ,Trees -- Physiological aspects -- Environmental aspects ,Climate -- Social aspects -- Statistics -- Environmental aspects ,Growth (Plants) -- Research ,Earth sciences - Abstract
: Existing literature investigates the effect of the number of cored trees per plot (N) on chronology statistics. The present study sought to highlight (i) the effect of N on the reliability of both chronology and climate-growth relationships and (ii) its variability across five European tree species with differentiated ecophysiological patterns. Fifty-eight pure, even-aged forests were sampled across France. For each plot, dendroecological investigations were carried out using chronologies built from 28 to three trees. Chronology reliability was studied using the mean intertree correlation (rbt) and the expressed population signal (EPS), whereas the climate-growth relationships were evaluated through the bootstrapped correlation coefficients (BCC). The accuracy of the dendroecological investigations decreased with decreasing N: EPS and BCC approached zero, implying that the signal common to all trees weakened. Thus, most of the significant correlations became nonsignifi-cant when the sample size decreased from 28 to three trees per plot. Differences were found between species. For a given sample size, the shade-intolerant species Quercus petraea and Pinus sylvestris displayed lower intertree differences in growth-index series (higher rbt) and higher EPS than the shade-tolerant species Abies alba, Fagus sylvatica, and Picea abies. These latter species also displayed a greater sensitivity to sample size decrease, with a stronger BCC weakening and a higher proportion of changes in correlation significance. The EPS threshold of 0.85 was reached for around six to 10 trees for shade-intolerant species versus 20-30 for the shade-tolerant ones and generally corresponded to a mean correlation preci-sion of around 0.06. We finally propose a general method to estimate this precision. Resume: La litterature examine l'effet du nombre d'arbres carottes par placette (N) sur les statistiques de la chronologie. La presente etude a cherche a mettre en evidence (i) l'effet de N sur la qualite de la chronologie et de l'estimation des rela-tions cerne-climat, et (ii) sa variabilite sur cinq essences europeennes a autecologies contrastees. Cinquant-huit forets pures et regulieres ont ete echantillonnees a travers la France. A chaque placette, les etudes dendroecologiques ont ete menees avec des chronologies construites a partir de 28 a trois arbres. La qualite de la chronologie a ete etudiee au travers de la cor-relation inter-arbre moyenne (rbt) et de l' expressed population signal (EPS), alors que les relations cerne-climat ont ete evaluees par le calcul des coefficients de correlation bootstrapped. La justesse des analyses dendroecologiques a diminue avec la baisse de N: l'EPS et les BCC se sont rapproches de zero, impliquant que le signal commun a tous les arbres s'etait affaibli. Par consequent, la plupart des correlations significatives sont devenues non-significatives quand la taille de l'echan-tillon a diminue de 28 a trois arbres par placette. Des differences ont ete observees entre les especes. Pour une taille d'e-chantillon donnee, les especes heliophiles Quercus petraea et Pinus sylvestris ont montre de plus faibles differences interarbres dans les series d'indices de croissance (rbt plus eleves) et de plus forts EPS que les especes tolerantes a l'ombre Abies alba, Fagus sylvatica et Picea abies. Ces dernieres especes ont ete plus sensibles a la baisse de la taille de l'echantil-lon, avec une plus forte diminution des BCC et une plus forte proportion de changement de significativite. Le seuil d'EPS de 0,85 a ete atteint pour environ six a 10 arbres carottes pour les especes heliophiles, contre 20 a 30 pour les especes tole-rantes a l'ombrage. Nos resultats ont egalement mis en evidence que, quelque soit l'espece, le seuil d'EPS de 0,85 corres-pondait a une precision moyenne des BCC d'environ 0,06. Nous proposons enfin une methode generale pour estimer cette precision., Introduction In temperate and northern ecosystems, tree-ring width has been widely used to investigate the environmental influence on tree growth because it easily provides quantitative and annual retrospective information (Fritts [...]
- Published
- 2011
- Full Text
- View/download PDF
17. Detection of high-wind events using tree-ring data
- Author
-
Hadley, Keith S. and Knapp, Paul A.
- Subjects
Dendrochronology -- Research ,Cyclones -- Research -- United States ,Earth sciences - Abstract
Windstorms are common events in midlatitude west coast climates yet little is known about their long-term history and influence on regional forests. In this paper, we present a procedure that detects the timing and frequency of these high-wind events (HWEs) along the Pacific Northwest coast of North America using crossdated tree-ring measurements and detrended tree-ring chronologies derived from windsnapped trees. Our results show that abrupt changes in ring width pat-terns closely match dates of known HWEs and can serve as a nonclimatic basis for crossdating. Experimentation with different growth suppression and release criteria revealed that either a 50% decrease or a 50% increase in radial growth relative to the mean index value provided the best criterion for detecting windstorm-related growth anomalies. Comparing these results with the known occurrence of windstorms during the past century successfully identified all known major wind events during the study period. Low correlations between tree growth and climatic variables further imply that HWEs are the principal cause of interannual growth variations. Accordingly, we discuss the application of our procedure toward the development of a multicentury reconstruction of HWEs, a long-term analysis of decadal climate variability and HWEs, and the ecological role of HWEs in Pacific Northwest and other west coast forests. Les tempetes de vent sont des evenements courants sous les climats temperes de mi-latitude de la cote ouest mais leur historique a long terme et leur influence sur les forets regionales sont peu connus. Dans cet article, nous presentons une methode pour detecter le moment et la frequence de ces episodes de vent fort (EVF) le long de la cote du Pacific Northwest de l'Amerique du Nord en utilisant des mesures de datation croisee des cernes annuels et des series dendrochro-nologiques purgees de leur composante tendancielle provenant d'arbres brises par le vent. Nos resultats montrent que les changements abrupts dans la largeur des cernes annuels correspondent etroitement aux dates ou sont survenus des EVF connus et peuvent servir de base non climatique pour la datation croisee. L'experimentation avec differents criteres de suppression et de reprise de la croissance a revele qu'une diminution ou qu'une augmentation de 50 % de la croissance radiale relativement a la valeur de l'indice moyen constituent le meilleur critere pour detecter les anomalies de croissance reliees aux tempetes de vent. La comparaison de ces resultats avec l'occurrence connue des tempetes de vent au cours du siecle dernier a permis d'identifier avec succes tous les episodes connus de vent fort au cours de la periode d'etude. Les faibles correlations entre la croissance des arbres et les variables climatiques indiquent aussi que les EVF sont la principale cause des variations interannuelles de croissance. Par consequent, nous discutons de l'application de notre methode pour realiser une reconstitution des EVF sur plusieurs siecles, analyser la variabilite a long terme du climat sur une base decennale et celle des EVF ainsi que determiner le role ecologique des EVF dans les forets du Pacific Northwest et dans les autres forets de la cote ouest. [Traduit par la Redaction], Introduction Strong midlatitude cyclones and typhoon remnants generating hurricane-force winds (i.e., sustained winds ≥ 118 km/h) are common events in the marine west coast climates of North America (e.g., Mass [...]
- Published
- 2011
- Full Text
- View/download PDF
18. New Earth Science Findings Has Been Reported by Investigators at Polish Academy of Sciences [Bog Pine Dendrochronology Related To Peat Stratigraphy: Palaeoenvironmental Changes Reflected In Peatland Deposits Since the Late Glacial (Case Study of ...]
- Subjects
Geology, Stratigraphic -- Research ,Dendrochronology -- Research ,Geological research ,Health ,Science and technology - Abstract
2022 MAR 18 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- Current study results on Science - Earth Science have been published. According to news reporting [...]
- Published
- 2022
19. Population dynamics of Empetrum hermaphroditum (Ericaceae) on a subarctic sand dune: evidence of rapid colonization through efficient sexual reproduction
- Author
-
Boudreau, Stephane, Ropars, Pascale, and Harper, Karen Amanda
- Subjects
Dendrochronology -- Research ,Ericaceae -- Natural history ,Population biology -- Research ,Biological sciences - Abstract
The importance of sexual reproduction for clonal plant species has long been underestimated, perhaps as a consequence of the difficulty in identifying individuals, preventing the study of their population dynamics. Such is the case for Empetrum hermaphroditum, an ericaceous species, which dominates the ground vegetation of subarctic ecosystems. Despite abundant seed production, seedlings are rarely observed. Therefore, prevalent seedling recruitment on a subarctic dune system provided an opportunity to study the population dynamics and spatial pattern of the colonization phase of this species. We established a 6-ha grid on the dune systems that extended from the shoreline to the fixed dunes and mapped and measured all E. hermaphroditum individuals in the grid. Moreover, we sampled 112 individuals just outside the grid to identify any allometric relationship between the size and age of the individuals, which allowed us to reconstruct population expansion. The overall size structure suggests that the population is still expanding. In the last 50 yr, E. hermaphroditum advanced more than 200 m in the dune system. Expansion started in the 1960s simultaneously at different distances from the shoreline. Colonization did not proceed gradually from the fixed dune toward the shoreline but instead individuals established earlier in the troughs between the dunes, with an increasingly clumped spatial pattern as the population filled in with time. Key words: allometric relationship; clonal species; dendrochronology; dune colonization; Empetrum hermaphroditum; Ericaceae; population dynamics; seedling establishment; spatial pattern; subarctic environments. doi: 10.3732/ajb.0900304
- Published
- 2010
20. Climate as a contributing factor in the demise of Angkor, Cambodia
- Author
-
Buckley, Brendan M., Anchukaitis, Kevin J., Penny, Daniel, Fletcher, Roland, Cook, Edward R., Sano, Masaki, Nam, Le Canh, Wichienkeeo, Aroonrut, Minh, Ton That, and Hong, Truong Mai
- Subjects
Dendrochronology -- Research ,Paleoclimatology -- Research ,Science and technology - Abstract
The 'hydraulic city' of Angkor, the capitol of the Khmer Empire in Cambodia, experienced decades-long drought interspersed with intense monsoons in the fourteenth and fifteenth centuries that, in combination with other factors, contributed to its eventual demise. The climatic evidence comes from a seven-and-a-half century robust hydroclimate reconstruction from tropical southern Vietnamese tree rings. The Angkor droughts were of a duration and severity that would have impacted the sprawling city's water supply and agricultural productivity, while high-magnitude monsoon years damaged its water control infrastructure. Hydroclimate variability for this region is strongly and inversely correlated with tropical Pacific sea surface temperature, indicating that a warm Pacific and El Nino events induce drought at interannual and interdecadal time scales, and that low-frequency variations of tropical Pacific climate can exert significant influence over Southeast Asian climate and society. collapse | dendrochronology | paleoclirnate | El Nino-Southern Oscillation | Palmer Drought Severity Index doi/ 10.1073/pnas.0910827107
- Published
- 2010
21. Dendroentomological evidence associated with an outbreak of the native wood-boring beetle Enaphalodes rufulus
- Author
-
Fierke, Melissa K. and Stephen, Fred M.
- Subjects
Insect-plant relationships -- Research ,Dendrochronology -- Research ,Beetles -- Research - Abstract
An outbreak of Enaphalodes rufulus Haldeman, a North American wood-boring cerambycid beetle, appears to be a major contributing factor to a recent Quercus rubra L. mortality event. The objectives of this research were to investigate the historical activity and within-tree distributions of E. rufulus by using scars formed by larval feeding in the cambium and xylem. Scars were counted and dated in fifteen 63- to 88-year-old northern red oaks; five in each of three infestation classes (low, moderate, and high). There were significantly fewer scars noted in low infestation trees than in trees with high infestations, and moderately infested trees showed intermediate scarring. There were significant differences in the date of the first xylem scar with initial scars occurring in 1980 in low infestation trees, 1952 in moderate, and 1940 in high. The number of xylem scars present varied significantly at different heights on the tree bole, but no differences were found based on tree aspect. This research provides evidence that an outbreak of red oak borer has not occurred before in these trees, beetles have not undergone recent population oscillations, trees that are currently highly infested have been infested over a longer period of time and at higher densities than low infestation trees, and there are distinctive within-tree larval distributions. Resume: Une epidemie du grand longicorne du chene rouge (Enaphalodes rufulus Haldeman), un cerambycide perceur indigene de l'Amerique du Nord, semble etre un facteur important qui aurait contribue a un episode recent de mortalite du chene rouge (Quercus rubra L.). Les objectifs de cette recherche etaient d'etudier l'activite passee et la distribution dans les arbres du grand longicorne du chene rouge grace aux cicatrices laissees par les larves qui se nourrissent dans le cambium et le xyleme. Les cicatrices ont ete denombrees et datees chez 15 chenes rouges nordiques ages de 63 a 88 ans, a raison de cinq cicatrices par classe d'infestation (legere, moderee et severe). Significativement moins de cicatrices ont ete notees sur les arbres legerement infestes comparativement aux arbres severement infestes et les arbres moderement infestes occupaient une position intermediaire. Il y avait des differences significatives entre les dates de la premiere cicatrice dans le xyleme qui est survenue en 1980 chez les arbres legerement infestes, en 1952 chez les arbres moderement infestes et en 1940 chez les arbres severement infestes. Les cicatrices presentes dans le xyleme variaient de facon significative selon la hauteur sur le tronc mais il n'y avait pas de difference selon l'orientation du tronc. Cette recherche demontre: qu'il n'y a pas eu d'autres epidemies du grand longicorne du chene rouge sur ces arbres avant celle-ci, que ce longicorne n'a pas subi d'oscillations de population recemment, que les arbres qui sont presentement severement infestes ont ete infestes pendant une plus longue periode de temps et plus densement que les arbres legerement infestes et qu'il y a des distributions distinctes des larves dans les arbres. [Traduit par la Redaction], Introduction High populations of red oak borer (Enaphalodes rufulus (Haldeman)) (Coleoptera: Cerambycidae) have been implicated as a major contributing factor in a recent widespread oak mortality event in the Ozark [...]
- Published
- 2010
- Full Text
- View/download PDF
22. Geomorphology of snow avalanche impact landforms in the southern Canadian Cordillera
- Author
-
Johnson, Alexis L. and Smith, Dan J.
- Subjects
Avalanches -- Canada ,Avalanches -- Environmental aspects ,Dendrochronology -- Research ,Landforms -- Natural history ,Landforms -- Structure ,Geography - Published
- 2010
23. Geoscience of climate and energy 6. Tree rings as temperature proxies
- Author
-
Luckman, Brian H.
- Subjects
Dendroclimatology -- Management ,Dendrochronology -- Research ,Temperature measurements -- Analysis ,Company business management ,Environmental issues ,Earth sciences - Abstract
SUMMARY Tree rings have provided annually resolved and precisely dated proxy climate records for large areas of the earth's land surface. These records are considerably longer than instrumental climate data [...]
- Published
- 2010
24. Dendrochronological dating of coal mine workings at the Joggins Fossil Cliffs, Nova Scotia, Canada
- Author
-
Quann, Sarah L., Young, Amanda B., Laroque, Colin P., Falcon-Lang, Howard J., and Gibling, Martin R.
- Subjects
Nova Scotia -- Environmental aspects ,Dendrochronology -- Research ,Earth sciences - Abstract
ABSTRACT Joggins, Nova Scotia, was one of the first places in North America where coal was mined. Dendrochronological methods were employed to date timber pit props preserved within relic coal [...]
- Published
- 2010
- Full Text
- View/download PDF
25. Changes in growth and dendroclimatic response of trees growing along an artificial lake
- Author
-
Copenheaver, Carolyn A., Hendrick, Laura E., Houchins, John W., and Pearce, Christopher D.
- Subjects
Dendrochronology -- Research ,Tree-rings -- Evaluation ,White oak -- Physiological aspects ,Growth (Plants) -- Research ,Biological sciences ,Earth sciences - Abstract
The objective of this study was to track changes in growth and dendroclimatic response of white oak (Quercus alba) trees that established in the forest interior and, following the creation of an artificial lake, continued living along the lake edge. Twenty-one white oaks from the lake edge were cored and 91% of the trees exhibited a growth response to the creation of the lake--most commonly a suppression. Two 32 y segments (pre-lake and postlake) were compared for differences in dendroclimatic response. The tree-ring chronology from the pre-lake time period had significant negative correlations between ring width index (RWI) and temperature in Jun.; significant positive correlations between RWI and precipitation from Jun. of the previous year; significant positive correlations between RWI and precipitation in Mar. of the current year; and significant positive correlations between RWI and Palmer Drought Severity Index (PDSI) in Jul. After lake construction, the same trees exhibited significant positive correlations between RWI and Jul. temperature from the previous year; significant negative correlations between RWI and temperature in Feb. and May; significant positive correlations between RWI and precipitation in Sep.; and significant positive correlations between RWI and PDSI in Jun., Jul., Aug. and Sep. Most trees that experienced transitions from interior to edge positions responded with a decline in growth rate and a moderate change in dendroclimatic responsiveness., INTRODUCTION Quantifying the influence of forest edge on tree growth elucidates how forest fragmentation and silvicultural practices alter tree physiology and productivity (Bebber et al., 2004; McDonald and Urban, 2004). [...]
- Published
- 2010
26. Chemical pretreatment of Thuja occidentalis tree rings: implications for dendroisotopic studies
- Author
-
Au, Robert and Tardif, Jacques C.
- Subjects
Dendrochronology -- Research ,Tree-rings -- Properties ,Earth sciences ,Research ,Properties - Abstract
Whether or not extractives, lignin, and (or) hemicelluloses, all of which have specific isotopic signatures, should be removed prior to dendroisotopic analysis is still debated. This study reports the range of modern tree-ring [δ.sup.13]C values of cellulose from Thuja occidentalis L., a species that has been under-utilized in dendroisotopic research despite its broad distribution and great longevity in North America. The main objective of the study was to recommend a wood component from T. occidentalis to isolate for future [δ.sup.13]C dendroisotopic analyses. Annually resolved tree-ring decadal segments common to eight T. occidentalis trees were excised from cross sections and homogenized. The tree-ring decadal segment from each tree was then chemically processed from untreated whole wood to extractive-free wood, to holocellulose, and to acellulose. Subsamples were analyzed for [δ.sup.13]C, percent carbon, and percent yield after each stage of chemical treatment. We recommend that holocellulose be extracted for T. occidentalis, as the a-cellulose yield may be too low when tree- ring samples are very small. The [δ.sup.13]C values for T. occidentalis tree rings were found to be enriched with respect to those for needle-leaved conifers but in close agreement with those reported in the literature for other scale-leaved evergreens. Un debat est actuellement en cours a savoir si les produits d'extraction, soit la lignine et les hemicelluloses, qui ont tous une signature isotopique specifique, devraient etre elimines avant de proceder a l'analyse dendroisotopique. Cette etude rapporte l'etendue des valeurs de [δ.sup.13]C de la cellulose dans les cernes recents du Thuja occidentalis L., une espece sous-utilisee en recherche dendroisotopique malgre sa vaste distribution et sa grande longevite en Amerique du Nord. L'objectif principal de cette etude etait de recommander une composante du bois de T. occidentalis a isoler pour les futures analyses dendroisotopiques de [δ.sup.13]C. Les cernes annuels correspondant aux memes 10 annees ont ete preleves sur des sections radiales de huit T. occidentalis. Les tissus de chaque groupe de 10 cernes ont ete homogeneises et traites chimiquement pour obtenir du bois exempt de produits d'extraction, de l'holocellulose et de l'alpha-cellulose. Des souse echantillons ont ete analyses pour determiner la valeur de [δ.sup.13]C, le pourcentage de C et le pourcentage de rendement apres chaque etape du traitement chimique. Nous recommandons l'extraction de l'holocellulose dans le cas de T. occidentalistant donne que le rendement de l'alpha-cellulose pourrait etre trop faible dans les cas ou le volume des echantillons de cernes annuels est tres faible. Nous avons trouve que les valeurs de [δ.sup.13]C des cernes de T. occidentalis sont plus elevees comparativement aux coniferes qui ont des feuilles aciculaires mais tres pres des valeurs rapportees dans la litterature pour les autres coniferes qui ont des feuilles squamiformes. [Traduit par la Redaction], 1. Introduction Isotopic analysis of tree rings provides some of the highest resolution climatic information from continental temperate forests and is of great interest to those who develop scenarios for [...]
- Published
- 2009
27. Fire history of a central Nevada pinyon-juniper woodland
- Author
-
Bauer, John M. and Weisberg, Peter J.
- Subjects
Forest ecology -- Research ,Forest fires -- Research -- North America ,Dendrochronology -- Research ,Pine -- History ,Earth sciences ,Research ,History - Abstract
Our study reconstructed fire history (1445-2006) from tree rings for a Great Basin single-needle pinyon pine (Pinus monophylla Torr & Frem.)--Utah juniper (Juniperus osteosperma (Torr.) Little) woodland. Information from multiple lines of evidence, including dateable fire scars (n = 83), tree demography, and charred coarse woody debris, was used to quantify fire frequency, severity, and extent. Fire cycle models were developed using survivorship analysis of time-since-fire estimates. We investigated the spatial and temporal variation in historical fire regime, addressing the plausibility of postsettlement fire exclusion as an explanation for increased woodland area and density since the late 1800s. Historical fire regime was characterized by infrequent, small, high-severity fires. Estimated fire cycle (1570-1880) was 427 years, with no evidence of postsettlement stand-replacing fires. Topographic analyses indicated that in this drought-prone landscape, more mesic conditions favor continuous fuels that lead to more frequent or extensive fire. Superposed epoch analysis showed increased fire occurrence during drought years but with no influence of antecedent climatic conditions. More frequent grassland and shrubland fires were recorded by fire scars near valley floors. Thus, anthropogenic fire exclusion in adjacent, shrub-dominated communities presents a plausible mechanism for woodland expansion in the study area. However, there is little ecological justification for reintroducing fire to areas of historic woodland, where effects of fire exclusion have been minimal. Notre etude dendrochronologique a permis de reconstituer l'historique des feux (1445-2006) dans un boise de pin faux-arolle (Pinus monophylla Torr & Frem.) et de genevrier (Juniperus osteosperma (Torr.) Little) situe dans le Great Basin. L'information provenant de plusieurs sources, incluant les cicatrices de feu datables (n = 83), la demographie des arbres et les debris ligneux grossiers carbonises, a ete utilisee pour quantifier la frequence, la severite et l'etendue des feux. Des modeles du cycle de feu ont ete developpes en utilisant l'analyse de survie des estimations du temps ecoule depuis un feu. Nous avons etudie les variations spatiales et temporelles du regime de feux passe en abordant le fait que l'exclusion du feu apres la colonisation pourrait expliquer l'augmentation de la superficie et de la densite des boises depuis la fin des annees 1800. Le regime de feux passe etait caracterise par des feux de forte severite, petits et peu frequents. La dure e du cycle de feu (1570-1880) a ete estimee a 427 ans et il n'y avait pas d'indices de feux causant le remplacement des peuplements apres la colonisation. Des analyses topographiques indiquent que, dans ce paysage sujet a la secheresse, des conditions plus mesiques favorisent la presence continue de combustibles associes a des feux plus frequents et plus etendus. Une analyse par superposition d'epoques a montre que l'occurrence des feux a augmente durant les annees de se cheresse mais sans que les conditions climatiques anterieures exercent une influence. Des feux de prairie et de broussailles ont ete enregistres par les cicatrices de feu pres du fond des vallees. L'exclusion du feu par l'homme dans les communautes adjacentes dominees par des arbustes constitue par consequent un mecanisme plausible pour expliquer l'expansion des boises dans la zone detude. Cependant, il y a peu de justification ecologique pour reintroduire le feu dans les zones historiquement boisees, ou l'exclusion du feu a eu peu d'effets. [Traduit par la Redaction], Introduction Characterization of historical fire regimes has emerged as an important component for ecological restoration of North American forests and woodlands (Landres et al. 1999; Bergeron et al. 2002). However, [...]
- Published
- 2009
28. Dendroglaciological evidence for Holocene glacial advances in the Todd Icefield area, northern British Columbia Coast Mountains
- Author
-
Jackson, Scott I., Laxton, Sarah C., and Smith, Dan J.
- Subjects
Dendrochronology -- Research ,Little Ice Age ,Paleogeography -- Holocene ,Earth sciences ,Observations ,Research - Abstract
Abstract: Accelerated glacial recession and downwasting in Pacific North America is exposing land surfaces and features buried by glacial advances that, in many locations, predate the recent Little Ice Age [...]
- Published
- 2008
29. Raised in the wild south : a dendrochronological and dendrochemical profile of a far-southern stand of kauri (Agathis australis) on the Taieri Plain, Otago
- Author
-
Brookman, Tom H.
- Published
- 2014
30. Climate and disturbance forcing of episodic tree recruitment in a Southwestern ponderosa pine landscape
- Author
-
Brown, Peter M. and Wu, Rosalind
- Subjects
Climatic changes -- Environmental aspects ,Ponderosa pine -- Environmental aspects ,Dendrochronology -- Research ,Biological sciences ,Environmental issues - Abstract
Strong but relatively short (annual to decadal length) climate change can have broad-scale and long-lasting effects on forest communities. Climate impacts forests through direct effects on tree demography (mortality and overstory recruitment) and indirect effects on disturbance regimes. Here, we compare multicentury chronologies of tree recruitment from a 307-ha ponderosa pine forest in southwestern Colorado to reconstructions of fire years, hydroclimate, and the El Nino-Southern Oscillation (ENSO). Few trees predate a regional multiyear megadrought centered in the 1580s. A prolonged pluvial in the early-1600s resulted in a pulse of tree recruitment that corresponds to recruitment seen over much of the Southwest. Other cohorts in the early 1700s and mid-1800s established during multidecadal fire-quiescent periods. These periods correspond to shifts in ENSO that apparently resulted in dampening of interannual wet/dry oscillations responsible for fuel buildup and drying. Fires, mediated by stochastic climate variation, acted as a density-independent regulation on tree populations since establishment was not limited by overstory tree density, but rather by fire-caused mortality of seedlings and saplings during periods of more frequent tires. Even-aged cohorts in ponderosa pine forests likely have little if anything to do with episodic mortality caused by more severe fires, but rather relate mainly to episodic recruitment opportunities. Fire cessation after Euro-American settlement in the late 1800s resulted in an increase in tree density and changes in forest composition, which are major factors that have contributed to recent severe wildfires in other Southwestern forests. Our results document clear linkages between synoptic climate forcing, fires, and recruitment episodes, and highlight the importance of regional historical processes on contemporary forest composition and structure. Key words: dendroecology; density-independent population dynamics; drought; El Nino-Southern Oscillation; fire regimes; tree demography; tree recruitment.
- Published
- 2005
31. The peripatetic hedge: a case for dendrochronological dating.
- Author
-
Winchester, V.
- Subjects
Dendrochronology -- Research ,Land titles -- Interpretation and construction ,Land titles -- Cases ,Company legal issue - Published
- 2003
32. Reconstructing salmon abundance in rivers: an initial dendrochronological evaluation
- Author
-
Drake, Deanne C., Naiman, Robert J., and Helfield, James M.
- Subjects
Fish populations -- Research ,Pacific salmon -- Research ,Dendrochronology -- Research ,Biological sciences ,Environmental issues - Abstract
Decision-makers concerned with salmon or their stream habitats are faced with many persistent, difficult questions including: how large and variable were these populations before European settlement? Here, we examine the feasibility of reconstructing salmon abundance using links between marine nutrients carried upstream by Pacific salmon (Oncorhynchus spp.) and growth of dominant riparian trees in two Alaskan systems. We employ standard dendrochronology methods and regression models to quantify relationships between annual tree-ring growth, salmon escapement, and the climate pattern that affects oceanic production of Northeast Pacific salmon stocks, the Pacific Decadal Oscillation (PDO). We find that known, annual salmon escapement is significantly related to tree-ring growth at two sites in the Pacific coastal rainforest (PCRF) ([r.sup.2] = 0.23, P < 0.05 at each site), but not at two sites in the boreal forest. We then use relationships established at PCRF sites to reconstruct preliminary salmon spawning abundances to 1820 A.D. The PDO was not correlated with local 19-yr salmon escapement records and could not be used in reconstructions. Reconstructions compare favorably to southeastern Alaska fisheries catch data from 1924 to 1994 (Pearson correlation = 0.301 [P = 0.02] and 0.401 [P < 0.01]). This study demonstrates the promise and utility of dendrochronology for reconstructing salmon returns to streams. Key words: dendrochronology; fertilization; marine-derived nutrients; nutrient cycling; Onchorynchus spp.; Pacific Decadal Oscillation, PDO; Picea glauca; Picea sitchensis; riparian forest, salmon; Sitka spruce; white spruce.
- Published
- 2002
33. Recent Findings in Quaternary Science Described by Researchers from Mendel University Brno (Effects of Social and Climatic Factors On Building Activity In the Czech Lands Between 1450 and 1950: a Dendrochronological Analysis)
- Subjects
Technology and civilization -- Research ,Dendrochronology -- Research ,Food supply -- Research ,Health ,Science and technology - Abstract
2021 NOV 5 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- Data detailed on Science - Quaternary Science have been presented. According to news reporting originating [...]
- Published
- 2021
34. RECONSTRUCTION OF SUBARCTIC LAKE LEVELS OVER PAST CENTURIES USING TREE RINGS
- Author
-
Begin, Yves
- Subjects
Canada -- Environmental aspects ,Tree-rings -- Usage ,Dendrochronology -- Research ,Erosion -- Research ,Geomorphological research -- Analysis ,Climatic changes -- Canada ,Lakes -- Canada ,Hydrology -- Research ,Engineering and manufacturing industries ,Science and technology - Abstract
This paper presents the dendrochronological markers used to date the erosive activity of ice and waves on the shores of two large lakes in Northern Quebec. Damages to trees are dated by detailed analysis of anomalous tree rings in response to the shore geomorphic activity associated with extreme water levels over the last 2 centuries. Spring floods are dated using ice scars on trees and shrubs. Lake ice breakup occurs 4-6 weeks after snowmelt. Marks on trees made by ice displaced by the wind indicate the flood levels. Once ice breakup is complete, waves erode forest edges. Tree tilting, dated by counting rings in compression wood, mark high lake levels at the beginning of summer. At submerged sites that are not subject to waves and ice, stress related to prolonged submersion results in narrow tree rings. Trees located in the immersion zone show narrow rings compared to wider rings in unsubmerged trees. However, tree response is not immediate; they can primarily respond to sequences of several consecutive years of stress, reducing the resolution of dating to 2-3 years. Rings of submerged trees are denser than average. These high water level markers, as well as population recruitment showed by the age structure of shoreline trees and shrubs, which establish during intercalary years of low water levels, were used to date the extreme levels of two large lakes at the interface between the upper boreal and subarctic regions in northeastern Canada. During the past 200 years, the annual extreme levels have been increasing, becoming even more pronounced in the 1930s, and may be due to a century-long increase in snow precipitation. The summers seem to be drier. The 1930s, 1950s, and 1970s were marked by a high frequency of high water levels. Intercalary periods of low water levels allowed regeneration of shoreline forests and recovery of trees damaged during these events. It appears that episodes similar to the recent period of low waters experienced in the American northeast since 1982 may have occurred in the past during the 1920s, 1940s, and 1960s.
- Published
- 2000
35. TREE-RING VARIATION IN PINYON PREDICTS LIKELIHOOD OF DEATH FOLLOWING SEVERE DROUGHT
- Author
-
Ogle, Kiona, Whitham, Thomas G., and Cobb, Neil S.
- Subjects
Arizona -- Environmental aspects ,Dendrochronology -- Research ,Tree-rings -- Environmental aspects ,Pinus edulis -- Environmental aspects ,Pinyon pines -- Environmental aspects ,Plants -- Drought resistance ,Droughts -- Environmental aspects ,Biological sciences ,Environmental issues - Abstract
A severe drought in northern Arizona caused widespread pinyon (Pinus edulis) mortality, exceeding 40% in some populations. We measured tree-ring widths of pinyons that survived and that died in three sites designated as 'high,' 'medium,' and 'low' stress. Growth characteristics during the previous 10-15 years can be used to predict the likelihood of drought-induced death; dead trees exhibited 1.5 times greater variation in growth than live trees. A model of ring-width deviations vs. drought severity showed a loss of 'climatic sensitivity' with age in dead trees. These differences were independent of site. We found two distinct tree types that are predisposed to die during drought; highly sensitive young trees, and insensitive older trees. As the Southwest has a dynamic climate typified by severe droughts, it is important to understand how droughts act as bottleneck events to affect a dominant tree in a major vegetation type of the United States. Keywords: climatic sensitivity; drought; environmental stress; mortality, likelihood following drought; Pinus edulis; pinyon pine; tree rings.
- Published
- 2000
36. The Historic and Paleoclimatic Significance of Log Buildings in Southcentral Texas
- Author
-
Therrell, Matthew D.
- Subjects
Texas -- History ,Log buildings -- History ,Paleoclimatology -- Texas ,Dendrochronology -- Research ,Anthropology/archeology/folklore ,Regional focus/area studies - Abstract
Tree-ring dating has been applied to eight historic log buildings in southcentral Texas. The historic tree-ring chronologies derived from these buildings are combined with chronologies from living trees to create an improved and extended tree-ring record dating from A.D. 1649 to 1995 that is sensitive to regional and large-scale climate change. This extended chronology is significantly correlated with meteorological measurements of growing season moisture supply in Texas, and with the episodic influence of the El Nino-Southern Oscillation (ENSO). Tree-ring dating provides insight into the history and archaeology of these buildings. Historic structures also preserve crucial paleoclimatic data that can provide unique information about environmental and cultural history. Sadly, these historic structures are rapidly vanishing from the Texas landscape.
- Published
- 2000
37. WARMING WILL REDUCE ABILITY OF TREES TO SLOW CLIMATE CHANGE
- Subjects
Global warming -- Research ,Dendrochronology -- Research ,Atmospheric carbon dioxide -- Research ,News, opinion and commentary - Abstract
Tucson, AZ -- The following information was released by the University of Arizona: The world's forests play an important role in mitigating climate change. They are carbon sinks, meaning they [...]
- Published
- 2020
38. New research unlocks the key to the past of St Giles' Kirk as it approaches its 900th anniversary
- Subjects
Dendrochronology -- Research ,Chambers of commerce -- Research ,Archaeological dating -- Research ,Historic sites -- Research ,Timber -- Research ,New towns ,Time ,Cities and towns ,Company business management ,General interest ,News, opinion and commentary - Abstract
Edinburgh: Edinburgh Chamber of Commerce has issued the following news release: Historic Environment Scotland (HES) provided funding for the South East Scotland Oak Dendrochronology project (SESOD), led by Dr Coralie [...]
- Published
- 2020
39. Study Results from Yunnan University Provide New Insights into Biogeoscience (The Productivity of Low-elevation Juniper Forests In Central Asia Increased Under Moderate Warming Scenarios)
- Subjects
Dendrochronology -- Research ,Biological sciences ,Health - Abstract
2021 JUN 15 (NewsRx) -- By a News Reporter-Staff News Editor at Life Science Weekly -- Current study results on Science - Biogeoscience have been published. According to news reporting [...]
- Published
- 2021
40. A changing temperature response with elevation for Lagarostrobos Franklinii in Tasmania, Australia
- Author
-
Buckley, B.M., Cook, E.R., Peterson, M.J., and Barbetti, M.
- Subjects
Tasmania -- Natural history ,Climatic changes -- Research ,Dendrochronology -- Research ,Earth sciences - Abstract
A network of seven Huon pine ring-width chronologies is constructed from sites ranging in elevation from 200 to 950 metres above sea level in western Tasmania. The chronologies are analysed individually and collectively to explore Huon pine's response to climate as a function of elevation. Three chronologies from greater than 700 metres in elevation exhibit a strong, direct response to temperature for most growing season months (p < 0.05), while three from below 700 metres exhibit a weaker, direct response to growing-season temperature, and a strong, inverse relationship with temperature of the prior season of growth, also significant at the 0.05 level. Moisture availability at these temperate rainforest sites is less growth-limiting than temperature, and significant correlations for January (inverse) and April (direct) of the year of growth largely reflect the inter-relationships between temperature, precipitation and cloudiness, and their combined influence on photosynthesis, particularly at higher-elevation sites. A rotated Principal Component Analysis reveals a clear grouping of the high and low-elevation chronologies, represented by the first and second eigenvectors, respectively. The 700 metre Lake Marilyn Low chronology is revealed to be a transitional site between the two groupings, and likely reflects an important climatic ecotone where both temperature and photosynthetically-active radiation drop below optimum levels for the species, and begin to directly inhibit growth. Tasmania's west coast climate has been shown to exhibit a distinct vertical structure, exemplified by a subsidence-inversion layer above 900 metres. Temperature increases slightly with altitude above 930 metres (the elevation at which a peak in daily minimum and maximum humidity levels is observed) before decreasing again. A dense, orographically-generated cloud-zone of reduced light and temperature has a mean altitude between 700 and 900 metres, with the steepest drop in both air and soil temperature exhibited between 850 and 930 metres. This structure can account for Huon pine's changing response to climate with elevation as described in this paper, and reinforces the importance of careful site selection for dendroclimatic research. In the case of reconstructing warm-season temperature from Tasmanian Huon pine, the desired signal might be maximised through sampling at the few rare, subalpine stands which have been located in western Tasmania. The great length afforded by the low-elevation Huon pine resource may ultimately yield a far more detailed reconstruction of regional climate throughout the Holocene, with respect to a vertical profile, following the development of more sound, mechanistically-based response models.
- Published
- 1997
41. Recent trends in tree-ring records from high elevation sites in the Andes of Northern Patagonia
- Author
-
Villalba, Ricardo, Boninsegna, Jose A., Veblen, Thomas T., Schmelter, Andrea, and Rubulis, Sigfrido
- Subjects
Andes -- Natural history ,Patagonia -- Natural history ,Climatic changes -- Research ,Dendrochronology -- Research ,Earth sciences - Abstract
A new set of tree-ring records from the Andes of northern Patagonia, Argentina (41 [degrees] S) was used to evaluate recent (i.e., last 250 years) regional trends in tree growth at upper treeline. Fifteen tree-ring chronologies from 1200 to 1750 m elevation were developed for Nothofagus pumilio, the dominant subalpine species. Samples were collected along three elevational transects located along the steep west-to-east precipitation gradient from the main Cordillera (mean annual precipitation > 4000 mta) to an eastern outlier of the Andes (mean annual precipitation > 2000 mm). Ring-width variation in higher elevation tree-ring records from the main Cordillera is mainly related to changes in temperature and precipitation during spring and summer. However, the response to climatic variation is also influenced by local site factors of elevation and exposure. Based on the relationships between Nothofagus growth and climate, we reconstructed changes in snow cover duration in late spring and variations in mean annual temperature since A.D. 1750. Abrupt interannual changes in the mean annual temperature reconstruction are associated with strong to very strong El Nino-Southern Oscillation events. At upper treeline, tree growth since 1977 has been anomalously high. A sharp rise in global average tropospheric temperatures has been recorded since the mid-1970s in response to an enhanced tropical hydrologic cycle due to an increase in temperature of the tropical Pacific. Temperatures in northern Patagonia have been anomalously high throughout the 1980s, which is consistent with positive temperature anomalies in the tropical Pacific and along the western coast of the Americas at ca. 40 [degrees] S latitude. Our 250-year temperature reconstruction indicates that although the persistently high temperatures of the 1980s are uncommon during this period, they are not unprecedented. Tropical climatic episodes similar to that observed during the 1980s may have occurred in the recent past under pre-industrial carbon dioxide levels.
- Published
- 1997
42. Variations of wood delta 13C and water-use efficiency of Abies alba during the last century
- Author
-
Bert, Didier, Leavitt, Steven W., and Dupouey, Jean-Luc
- Subjects
Jura, France -- Natural history ,Plant-water relationships -- Research ,Dendrochronology -- Research ,Tree-rings -- Research ,Biological sciences ,Environmental issues ,Research ,Natural history - Abstract
Variations of intrinsic water-use efficiency during the last century were investigated based on analysis of Δ13C in tree rings of Abies alba from the Jura Mountains (eastern France). To separate the effects related to the age of the tree at the time the tree ring was formed from effects due to environmental changes, analyzed wood samples were extracted from a very large sample set including different tree ages and calendar dates of wood formation. For the first 75 yr of the life of Abies alba, Δ13C of wood holocellulose increases with the age of the tree from -24.4 at age 15 to approximately -22.5 at age 75. Between the ages of 75 and 150 values remain constant at -22.5. Consequently, the effect of the tree age on isotopic discrimination has to be taken into account in studies on the long-term environmental effects on Δ13C in tree rings. Divergent trends of Δ13C during the last century were observed between tree rings formed at age 40 and bulk air data. The isotopic discrimination A varied insignificantly around a mean of 17.3 between the 1860s and the 1930s. It then decreased to 15.8 from the 1930s to the 1980s. Using these results and classical models of carbon discrimination, we calculated that the intrinsic water-use efficiency (A/[g.sub.w], the ratio of C[O.sub.2] assimilation rate to stomatal conductance for water vapor), integrated over the year, has increased by 30% between the 1930s and the 1980s. These results, obtained at the level of mature trees, are consistent with the physiological effects of increasing C[O.sub.2] concentrations as observed in controlled experiments on young seedlings. They are consistent with the strong increases in radial growth observed for Abies alba in western Europe over the past decades. However, other long-term environmental changes such as increasing nitrogen deposition could cause similar effects. Key words: Abies alba; 13C/12C ratio; C[O.sub.2] fertilization; dendrochronology; isotopic discrimination; long-term trend; radial growth; stable-carbon isotopes; tree rings; water-use efficiency., INTRODUCTION The isotopic composition of tree rings carries an integrated annual record of environmental conditions. This was recognized early by Epstein and Yapp (1976) who found a strong correlation between [...]
- Published
- 1997
43. The use of dendroecological methods to estimate the time frame of environmental releases.
- Author
-
Balouet, Jean-Christophe
- Subjects
Dendrochronology -- Research ,Environmental impact analysis -- Methods - Published
- 2006
44. A 300-year history of disturbance and canopy recruitment for co-occurring white pine and hemlock on the Allegheny Plateau, USA
- Author
-
Abrams, Marc D. and Orwig, David A.
- Subjects
Allegheny National Forest, Pennsylvania -- Natural history ,White pine -- Environmental aspects ,Hemlock (Tree) -- Environmental aspects ,Dendrochronology -- Research ,Ecological succession -- Research ,Biological sciences ,Environmental issues - Abstract
1 Dendroecological techniques were used to examine the patterns of canopy recruitment in relation to disturbance history for two dominant, yet ecologically contrasting, tree species, Pinus strobus (white pine; disturbance dependent) and Tsuga canadensis (hemlock; late successional), in a 300-year-old primary forest. 2 Most tree recruitment in both species occurred between 1690 and 1810. All of the white pine, which dominated recruitment during the first 40 years due to more rapid height growth, recruited in this period. Low levels of hemlock recruitment continued until 1900. Most of the younger trees comprised several northern hardwood species. No trees were less than 50 years old and the forest was devoid of an understorey due to intense deer browsing. 3 Radial growth chronologies were determined for 27 cores across all species and age classes. These exhibited 1-11 major and/or moderate releases (indicative of disturbance) in most decades between 1730 and 1990. Peak releases were recorded in the 1950s when a series of severe windstorms impacted the site. Species recruitment patterns were related to earlier growth releases observed in the oldest cores. 4 White pine exhibited a degree of plasticity in initial radial growth (1-5 mm [year.sup.-1]) depending on the time of establishment, as well as the ability to survive through prolonged periods of depressed growth (< 0.5 mm [year.sup.-1]) followed by growth releases. Hemlock was less plastic in its initial growth rates but did have dramatic growth releases (up to 8.8 mm [year.sup.-1]) in several older trees. Thus, both species exhibited some unexpected dendroecological as well as successional attributes. 5 The future of this stand is uncertain due to the impacts of deer and insect outbreaks that plague the region, as well as fortuitous natural disturbances, e.g. wind and fire. Nonetheless, the dendroecological approach elucidated disturbance history, stand development and mechanisms of coexistence of two ecologically contrasting tree species, and should be used to further understanding of the complex ecology of other mixed-species forests and the successional role of various tree species. Keywords: age structure, dendrochronology, Pennsylvania, stand dynamics, succession, tree rings
- Published
- 1996
45. Testing tree-ring crossdatings and other correlated time series by means of first- and second-difference turn tests
- Author
-
Ghent, A.W. and Mochel, Shelia G.
- Subjects
Chronobiology -- Research ,Dendrochronology -- Research ,Tree-rings -- Research ,Biological sciences ,Earth sciences ,Research - Abstract
Two nonparametric tests are presented that are appropriate to, but not limited to, crossdatings of tree-ring chronologies. If each observed measurement in each of two biological time series is rated + or - insofar as it is larger or smaller than the preceding observation (commonly the observation of the preceding year), then the presence of correlation between the time series may be detected by forming a 2 x 2 table, entering in its four cells the counts of ++, + -, - +, and - - alignments. This is termed a first-difference turn test. If the turns taken by plots of tree-ring (or other) chronologies are rated R or L insofar as each graph turns to the right or left at each point, as viewed from early to more recent years, then a second-difference turn test can be performed by testing the RR, RL, LR, and LL alignments in a similar 2 x 2 table. These R, L ratings correspond respectively, to +, - signs of second-differences. The problem of nonindependence between adjacent +, - or R, L ratings is addressed through extensive (300,000+) Monte Carlo chi-square distributions for each test. Modified critical values that compensate for the distortion of the chi-square distribution are presented. A rapid punched-tape procedure for determining 2 x 2 table cell counts is illustrated by a correlation between July-August rainfall and catches of the Atlantic salmon in the Miramichi (New Brunswick, Canada) fishery., 1. INTRODUCTION Among several possible uses of the signs of differences between successive observations in time-series analyses, Moore and Wallis (1943, p. 154) noted that: The existence of correlation between [...]
- Published
- 1996
46. Tree-ring dating of pre-1980 volcanic flowage deposits at Mount St. Helens, Washington
- Author
-
Yamaguchi, David K. and Hoblitt, Richard P.
- Subjects
Mount Saint Helens -- Research ,Tree-rings -- Chronologies ,Dendrochronology -- Research ,Mudflows -- Chronologies ,Earth sciences - Published
- 1995
47. Disturbance regime and disturbance interactions in a Rocky Mountain subalpine forest
- Author
-
Veblen, Thomas T., Hadley, Keith S., Nel, Elizabeth M., Kitzberger, Thomas, Reid, Marion, and Villalba, Ricardo
- Subjects
Rocky Mountains -- Environmental aspects ,Dendrochronology -- Research ,Geographic information systems -- Usage ,Forest dynamics -- Research ,Forest declines -- Environmental aspects ,Biological sciences ,Environmental issues - Abstract
1 The spatial and temporal patterns of fire, snow avalanches and spruce beetle outbreaks were investigated in Marvine Lakes Valley in the Colorado Rocky Mountains in forests of Picea engelmannii, Abies lasiocarpa, Pseudotsuga menziesii and Populus tremuloides. Dates and locations of disturbances were determined by dendrochronological techniques. A geographic information system (GIS) was used to calculate areas affected by the different disturbance agents and to examine the spatial relationships of the different disturbances. 2 In the Marvine Lakes Valley, major disturbance was caused by fire in the 1470s, the 1630s and the 1870s and by spruce beetle outbreak in c. 1716, 1827 and 1949. 3 Since c. 1633, 9% of the Marvine Lakes Valley has been affected by snow avalanches, 38.6% by spruce beetle outbreak and 59.1% by fire. At sites susceptible to avalanches, avalanches occur at a near-annual frequency. The mean return intervals for fire and spruce beetle outbreaks are 202 and 116.5 years, respectively. Turnover times for fire and spruce beetle outbreaks are 521 and 259 years, respectively. 4 Several types of disturbance interaction were identified. For example, large and severe snow avalanches influence the spread of fire. Similarly, following a stand-devastating fire or avalanche, Picea populations will not support a spruce beetle outbreak until individual trees reach a minimum diameter which represents at least 70 years' growth. Thus, recent fires and beetle outbreaks have nonoverlapping distributions.
- Published
- 1994
48. Major wet interval in White Mountains Medieval Warm Period evidenced in Delta13C of bristlecone pine tree rings
- Author
-
Leavitt, Steven W.
- Subjects
White Mountains (New Hampshire) -- Natural history ,Middle Ages -- Environmental aspects ,Dendrochronology -- Research ,Climatic changes -- Research ,Climatology -- Research ,Earth sciences - Abstract
A long [[Delta].sup.13]C chronology was developed from bristlecone pine (Pinus longaeva) at the Methuselah Walk site in the White Mountains of California. The chronology represents cellulose from five-year ring groups pooled from multiple radii of multiple trees. The most dramatic isotopic event in the chronology appears from A.D. 1080-1129, when [[Delta].sup.13]C values are depressed to levels [approximately] 2[Sigma] below the mean for the period A.D. 925-1654. This isotopic excursion appears to represent a real event and is not an artifact of sampling circumstances; in fact, a similar excursion occurs in a previously-reported, independent [[Delta].sup.13]C chronology from bristlecone pine. By carbon isotope fractionation models, the shift to low [[Delta].sup.13]C values is consistent with abundant soil moisture, permitting leaf stomata to remain open, and allowing ready access of C[O.sub.2] from which carbon fixation may discriminate more effectively against 13C in favor of 12C. According to this model, the 13C-depleted 50-yr isotopic excursion represents the wettest period in the White Mountains in the past 1000 yr, during which isotope-reconstructed July Palmer Drought Severity Indices averaged [approximately] +2.2.
- Published
- 1994
49. Tree-ring and glacial evidence for the Medieval Warm Epoch and the Little Ice Age in Southern South America
- Author
-
Villalba, Ricardo
- Subjects
South America -- Natural history ,Dendrochronology -- Research ,Glacial epoch -- Research ,Climatology -- Research ,Climatic changes -- Research ,Earth sciences - Abstract
A tree-ring reconstruction of summer temperatures from northern Patagonia shows distinct episodes of higher and lower temperature during the last 1000 yr. The first cold interval was from A.D. 900 to 1070, which was followed by a warm period A.D. 1080 to 1250 (approximately coincident with the Medieval Warm Epoch). Afterwards a long, cold-moist interval followed from A.D. 1270 to 1660, peaking around 1340 and 1640 (contemporaneously with early Little Ice Age events in the Northern Hemisphere). In central Chile, winter rainfall variations were reconstructed using tree rings back to the year A.D. 1220. From A.D. 1220 to 1280, and from A.D. 1450 to 1550, rainfall was above the long-term mean. Droughts apparently occurred between A.D. 1280 and 1450, from 1570 to 1650, and from 1770 to 1820. In northern Patagonia, radiocarbon dates and tree-ring dates record two major glacial advances in the A.D. 1270-1380 and 1520-1670 intervals. In southern Patagonia, the initiation of the Little Ice Age appears to have been around A.D. 1300, and the culmination of glacial advances between the late 17th to the early 19th centuries. Most of the reconstructed winter-dry periods in central Chile are synchronous with cold summers in northern Patagonia, resembling the present regional patterns associated with the El Nino-Southern Oscillation (ENSO). The years A.D. 1468-69 represent, in both temperature and precipitation reconstructions from tree-rings, the largest departures during the last 1000 yr. A very strong ENSO event was probably responsible for these extreme deviations. Tree-ring analysis also indicates that the association between a weaker southeastern Pacific subtropical anticyclone and the occurrence of El Nino events has been stable over the last four centuries, although some anomalous cases are recognized.
- Published
- 1994
50. Tree-ring reconstructed rainfall over the Southeastern U.S.A. during the Medieval Warm Period and Little Ice Age
- Author
-
Stahle, David W. and Cleaveland, Malcolm K.
- Subjects
Southern States -- Natural history ,Middle Ages -- Environmental aspects ,Glacial epoch -- Research ,Dendrochronology -- Research ,Climatic changes -- Research ,Earth sciences - Abstract
A 1053-year reconstruction of spring rainfall (March-June) was developed for the southeastern United States, based on three tree-ring reconstructions of statewide rainfall from North Carolina, South Carolina, and Georgia. This regional reconstruction is highly correlated with the instrumental record of spring rainfall (r = +0.80; 1887-1982), and accurately reproduces the decade-scale departures in spring rainfall amount and variance witnessed over the Southeast during the past century. No large-magnitude centuries-long trends in spring rainfall amounts were reconstructed over the past 1053 years, but large changes in the interannual variability of spring rainfall were reconstructed during portions of the Medieval Warm Period (MWP), Little Ice Age (LIA), and the 20th century. Dry conditions persisted at the end of the 12th century, but appear to have been exceeded by a reconstructed drought in the mid-18th century. High interannual variability, including five extremely wet years were reconstructed for a 20-yr period during the late 16th and early 17th centuries, and may reflect amplified atmospheric circulation over eastern North America during what appears to have been one of the most widespread cold episodes of the Little Ice Age.
- Published
- 1994
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.