The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Markus Stoffel - One of the best experts on this subject based on the ideXlab platform.
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tree ring proxies of larch bud moth defoliation latewood width and blue intensity are more precise than tree ring width
Tree Physiology, 2018Co-Authors: Estelle Arbellay, Ingrid Jarvis, Raphael D Chavardes, Lori D Daniels, Markus StoffelAbstract:Reconstructions of defoliation by larch bud moth (LBM, Zeiraphera diniana Gn.) based on European larch (Larix decidua Mill.) tree rings have unraveled outbreak patterns over exceptional temporal and spatial scales. In this study, we conducted tree-ring analyses on 105 increment cores of European larch from the Valais Alps, Switzerland. The well-documented history of LBM outbreaks in Valais provided a solid baseline for evaluating the LBM defoliation signal in multiple tree-ring parameters. First, we used tree-ring width measurements along with regional records of LBM outbreaks to reconstruct the occurrence of these events at two sites within the Swiss Alps. Second, we measured earlywood width, latewood width and blue intensity, and compared these parameters with tree-ring width to assess the capacity of each proxy to detect LBM defoliation. A total of six LBM outbreaks were reconstructed for the two sites between AD 1850 and 2000. Growth suppression induced by LBM was, on average, highest in latewood width (59%), followed by total ring width (54%), earlywood width (51%) and blue intensity (26%). We show that latewood width and blue intensity can improve the temporal accuracy of LBM outbreak reconstructions, as both proxies systematically detected LBM defoliation in the first year it occurred, as well as the differentiation between defoliation and non-defoliation years. This study introduces blue intensity as a promising new proxy of insect defoliation and encourages its use in conjunction with latewood width.
Roques Alain - One of the best experts on this subject based on the ideXlab platform.
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Structuration génétique des populations de tordeuse du mélèze, Zeiraphera diniana (Lepidoptera:Tortricidae), dans l'espace et dans le temps
2009Co-Authors: Delamaire Sophie, Roques AlainAbstract:Les insectes forestiers évoluent dans des écosystèmes particuliers caractérisés par leur longévité et leurs dimensions spatiales. Certains insectes forestiers, en particulier les défoliateurs, montrent des patterns de pullulations cycliques, parfois associés à un développement spatial précis. Zeiraphera diniana présente deux caractéristiques intéressantes (1) une temporelle et (2) une spatiale : (1) une très forte régularité dans la périodicité de ses pullulations observée depuis plus d un millénaire. Les densités de population fluctuant drastiquement tous les 8 à 10 ans dans les Alpes, provoquant des défoliations impressionnantes sur de grandes surfaces forestières (2) le développement spatial du pic de pullulation suit un pattern de traveling waves avec une initiation toujours située dans une région Française appelée Briançonnais. En tant que première étude sur la génétique des populations de la tordeuse du mélèze à l échelle de son aire de pullulation, cette thèse donne des éléments descriptifs sur les caractéristiques génétiques spatiales, avec une vision phylogéographique et historique. De plus, cette étude propose un regard sur la dynamique des populations complexe de cet insecte, en testant les prédictions génétiques correspondent aux modèles et hypothèses de dynamique existants.Forest insects evolve in particular ecosystems characterized by their longevity and their spatial dimensions. Some populations of forest insects, in particular defoliators, exhibit a pattern of cyclic outbreaks that can be associated with particular spatial development. Zeiraphera diniana exhibits two interesting characteristics, a (1) temporal one and a (2) spatial one : (1) really high regularity in outbreak periodicity observed for more than a thousand years. Population densities fluctuate dramatically with outbreaks every 8 to 10 years in the Alps, causing spectacular defoliation of large stands of larch forests (2) the outbreak spatial development follows a travelling wave pattern always initiated from an area located in a French area called Briançonnais. As the first study on population genetics of the larch budmoth all over its outbreak range, this PhD gives descriptive elements on the spatial genetic characteristics of the insect, with an insight in its phylogeography and past history. This study furthermore gives a spatio-temporal insight in the complex population dynamics observed, by testing genetic predictions corresponding to existing population dynamics models and hypotheses.ORLEANS-SCD-Bib. electronique (452349901) / SudocSudocFranceF
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Larch- and pine-feeding host races of the larch bud moth ( Zeiraphera diniana) have cyclic and synchronous population fluctuations.
Nordic Ecological Society, 2006Co-Authors: Dormont Laurent, Baltensweiler Laurent, Choquet Rémi, Roques AlainAbstract:International audiencePopulation cycles of many forest-defoliating insects often show synchronous fluctuations at both intra-specific (spatial synchrony) and inter-specific levels. However, population dynamics of different host-associated biotypes of the same species, such as those of the larch budmoth (LBM), Zeiraphera diniana (Lepidoptera: Tortricidae), have never been compared. This species causes extensive defoliation of larch forests every 8 to 9 years in the Alps, but it consists of two genetically-differentiated host races, the first one developing on European larch, Larix decidua, and the other one developing on Swiss stone pine, Pinus cembra. The dynamics of Zeiraphera populations have been extensively studied on..
Charles J Krebs - One of the best experts on this subject based on the ideXlab platform.
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the experimental paradigm and long term population studies
Ibis, 2008Co-Authors: Charles J KrebsAbstract:Most ecologists recognize the value of long-term studies to population and community ecology, and many also subscribe to the experimental approach as the most effective way of obtaining ecological knowledge. But if we are experimentalists, do we need long-term studies? I argue that the answer to this question is yes, that we must combine these two approaches to solve the major ecological questions of the next century. Most of the challenging questions facing ecologists involve systems subject to long-term time trends or high environmental variability. Because of the statistical power of many ecological methods, long-term studies are essential to measure time trends in ecosystems. Ignoring statistical power has been a major problem with short-term studies, which have predominated in the ecological literature. Some examples of long-term studies on larch bud-moth Zeiraphera diniana, winter moth Operophthera brumata and snowshoe hares are discussed briefly to illustrate the four major desiderata of long-term projects: spatial scale, sampling design, hypothesis testing and timeframe. Two reasons for not doing long-term studies are to assess density-dependence and to monitor ecosystem health. The density-dependent paradigm is bankrupt and has produced much argument and little understanding of population processes. Monitoring of populations is politically attractive but ecologically banal unless it is coupled with experimental work to understand the mechanisms behind system changes.
Ulf Büntgen - One of the best experts on this subject based on the ideXlab platform.
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Return of the moth: rethinking the effect of climate on insect outbreaks
Oecologia, 2020Co-Authors: Ulf Büntgen, Alain Roques, Andrew Liebhold, Daniel Nievergelt, Beat Wermelinger, Frederick Reinig, Paul J. Krusic, Alma Piermattei, Simon Egli, Paolo CherubiniAbstract:The sudden interruption of recurring larch budmoth (LBM; Zeiraphera diniana or griseana Gn.) outbreaks across the European Alps after 1982 was surprising, because populations had regularly oscillated every 8-9 years for the past 1200 years or more. Although ecophysiological evidence was limited and underlying processes remained uncertain, climate change has been indicated as a possible driver of this disruption. An unexpected, recent return of LBM population peaks in 2017 and 2018 provides insight into this insect's climate sensitivity. Here, we combine meteorological and dendrochronological data to explore the influence of temperature variation and atmospheric circulation on cyclic LBM outbreaks since the early 1950s. Anomalous cold European winters, associated with a persistent negative phase of the North Atlantic Oscillation, coincide with four consecutive epidemics between 1953 and 1982, and any of three warming-induced mechanisms could explain the system's failure thereafter: (1) high egg mortality, (2) asynchrony between egg hatch and foliage growth, and (3) upward shifts of outbreak epicentres. In demonstrating that LBM populations continued to oscillate every 8-9 years at sub-outbreak levels, this study emphasizes the relevance of winter temperatures on trophic interactions between insects and their host trees, as well as the importance of separating natural from anthropogenic climate forcing on population behaviour.
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summer temperature dependency of larch budmoth outbreaks revealed by alpine tree ring isotope chronologies
Oecologia, 2009Co-Authors: Anne Kress, Ulf Büntgen, Matthias Saurer, Kerstin Treydte, Harald Bugmann, Rolf T W SiegwolfAbstract:Larch budmoth (LBM, Zeiraphera diniana Gn.) outbreaks cause discernable physical alteration of cell growth in tree rings of host subalpine larch (Larix decidua Mill.) in the European Alps. However, it is not clear if these outbreaks also impact isotopic signatures in tree-ring cellulose, thereby masking climatic signals. We compared LBM outbreak events in stable carbon and oxygen isotope chronologies of larch and their corresponding tree-ring widths from two high-elevation sites (1800–2200 m a.s.l.) in the Swiss Alps for the period AD 1900–2004 against isotope data obtained from non-host spruce (Picea abies). At each site, two age classes of tree individuals (150–250 and 450–550 years old) were sampled. Inclusion of the latter age class enabled one chronology to be extended back to AD 1650, and a comparison with long-term monthly resolved temperature data. Within the constraints of this local study, we found that: (1) isotopic ratios in tree rings of larch provide a strong and consistent climatic signal of temperature; (2) at all sites the isotope signatures were not disturbed by LBM outbreaks, as shown, for example, by exceptionally high significant correlations between non-host spruce and host larch chronologies; (3) below-average July to August temperatures and LBM defoliation events have been coupled for more than three centuries. Dampening of Alps-wide LBM cyclicity since the 1980s and the coincidence of recently absent cool summers in the European Alps reinforce the assumption of a strong coherence between summer temperatures and LBM defoliation events. Our results demonstrate that stable isotopes in tree-ring cellulose of larch are an excellent climate proxy enabling the analysis of climate-driven changes of LBM cycles in the long term.
Rolf T W Siegwolf - One of the best experts on this subject based on the ideXlab platform.
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summer temperature dependency of larch budmoth outbreaks revealed by alpine tree ring isotope chronologies
Oecologia, 2009Co-Authors: Anne Kress, Ulf Büntgen, Matthias Saurer, Kerstin Treydte, Harald Bugmann, Rolf T W SiegwolfAbstract:Larch budmoth (LBM, Zeiraphera diniana Gn.) outbreaks cause discernable physical alteration of cell growth in tree rings of host subalpine larch (Larix decidua Mill.) in the European Alps. However, it is not clear if these outbreaks also impact isotopic signatures in tree-ring cellulose, thereby masking climatic signals. We compared LBM outbreak events in stable carbon and oxygen isotope chronologies of larch and their corresponding tree-ring widths from two high-elevation sites (1800–2200 m a.s.l.) in the Swiss Alps for the period AD 1900–2004 against isotope data obtained from non-host spruce (Picea abies). At each site, two age classes of tree individuals (150–250 and 450–550 years old) were sampled. Inclusion of the latter age class enabled one chronology to be extended back to AD 1650, and a comparison with long-term monthly resolved temperature data. Within the constraints of this local study, we found that: (1) isotopic ratios in tree rings of larch provide a strong and consistent climatic signal of temperature; (2) at all sites the isotope signatures were not disturbed by LBM outbreaks, as shown, for example, by exceptionally high significant correlations between non-host spruce and host larch chronologies; (3) below-average July to August temperatures and LBM defoliation events have been coupled for more than three centuries. Dampening of Alps-wide LBM cyclicity since the 1980s and the coincidence of recently absent cool summers in the European Alps reinforce the assumption of a strong coherence between summer temperatures and LBM defoliation events. Our results demonstrate that stable isotopes in tree-ring cellulose of larch are an excellent climate proxy enabling the analysis of climate-driven changes of LBM cycles in the long term.
