The Experts below are selected from a list of 2205 Experts worldwide ranked by ideXlab platform
Isabelle Chuine - One of the best experts on this subject based on the ideXlab platform.
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modelling the timing of betula pubescens Budburst ii integrating complex effects of photoperiod into process based models
Climate Research, 2011Co-Authors: Amelia Caffarra, Alison Donnelly, Isabelle ChuineAbstract:Despite experimental evidence of the individual and interactive effects of photoperiod and temperature on bud growth, photoperiod has not yet been effectively accounted for in models of Budburst. However, in some tree species, such as Betula pubescens (birch), photoperiod has an important role in phenological control, and its inclusion in process-based models of Budburst might affect phenological projections under climate change scenarios. The aim of the present study was to integrate photoperiod into a process-based phenological model (Chuine 2000; J Theor Biol 207: 337-347; Unified model), using experimental findings in which photoperiod was found to signifi- cantly affect Budburst in B. pubescens (Caffarra et al. 2011; Clim Res 46:147-157, this issue). The effect of photoperiod was integrated into the model at 2 levels. Firstly, photoperiod, in interaction with temperature, affects the course of dormancy induction. Secondly, photoperiod modifies the response to temperature during the phase of forcing. The resulting model (DORMPHOT) for the sim- ulation of birch Budburst was fitted to a large phenological dataset, including data from different lat- itudes, and validated with 7 datasets from 4 different European countries. Besides giving more bio- logical realism to the model, the newly introduced mechanisms improved its predictive performance. The DORMPHOT model outperformed the Unified model, the linear regression model (Budburst date vs. spring average temperature), and the UniForc model. It also proved to be more accurate at pre- dicting Budburst in extremely warm years, which suggests it might be more reliable than previous models when using future climate change scenarios.
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modelling the timing of betula pubescens Budburst i temperature and photoperiod a conceptual model
Climate Research, 2011Co-Authors: Amelia Caffarra, Alison Donnelly, Isabelle Chuine, M B JonesAbstract:The main factors triggering and releasing bud dormancy are photoperiod and temperature. Their individual and combined effects are complex and change along a transition from a dormant to a non-dormant state. Despite the number of studies reporting the effects of temperature and photoperiod on dormancy release and Budburst, information on the parameters defining these relationships is scarce. The aim of the present study was to investigate the effects and interaction of temperature and photoperiod on the rates of dormancy induction and release in Betula pubescens (Ehrh.) in order to develop a conceptual model of Budburst for this species. We performed a series of controlled environment experiments in which temperature and photoperiod were varied during different phases of dormancy in B. pubescens clones. Endodormancy was induced by short days and low temperatures, and released by exposure to a minimal period of chilling temperatures. Photoperiod during exposure to chilling temperatures did not affect Budburst. Longer exposure to chilling increased growth capability (growth rate at a given forcing temperature) and decreased the time to Budburst. During the forcing phase, Budburst was promoted by photoperiods above a critical threshold, which was not constant, but decreased upon longer chilling exposures. These relationships between photoperiod and temperature have, as yet, not been integrated into the commonly used processbased phenological models. We suggest models should account for these relationships to increase the accuracy of their predictions under future climate conditions.
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climatic determinants of Budburst seasonality in four temperate zone tree species
New Phytologist, 1999Co-Authors: Isabelle Chuine, P CourAbstract:summary Several physiological processes controlling tree phenology remain poorly understood and in particular bud dormancy. Many studies have emphasised the action of chilling temperatures in breaking dormancy. However, the eect of the preceding summer temperatures has rarely been investigated although there is some evidence that they may be involved in the settlement and intensity of dormancy as well as cold acclimation. In this paper, thermal time to Budburst in relation to the duration of chilling outdoors, preceding summer temperatures and forcing temperatures was studied by outdoors experiments in seedlings of Platanus acerifolia, Vitis vinifera, Quercus pubescens and Castanea sativa. Results showed that temperatures of the preceding summer had no significant eect on the timing of Budburst, P. acerifolia and Q. pubescens showed a very weak response to the duration of chilling, and the phenological characteristics of each species were found to be adapted to the climate conditions of its own geographical area. The phenological model used in this study explained 82‐100% of the variance of the data without taking into account summer temperatures. Thus, although summer temperatures may be well involved in the intensity of dormancy and cold hardiness, they do not significantly aect Budburst and therefore may not need to be considered in phenological models for predicting Budburst.
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Climatic determinants of Budburst seasonality in four temperate‐zone tree species
New Phytologist, 1999Co-Authors: Isabelle Chuine, P CourAbstract:summary Several physiological processes controlling tree phenology remain poorly understood and in particular bud dormancy. Many studies have emphasised the action of chilling temperatures in breaking dormancy. However, the eect of the preceding summer temperatures has rarely been investigated although there is some evidence that they may be involved in the settlement and intensity of dormancy as well as cold acclimation. In this paper, thermal time to Budburst in relation to the duration of chilling outdoors, preceding summer temperatures and forcing temperatures was studied by outdoors experiments in seedlings of Platanus acerifolia, Vitis vinifera, Quercus pubescens and Castanea sativa. Results showed that temperatures of the preceding summer had no significant eect on the timing of Budburst, P. acerifolia and Q. pubescens showed a very weak response to the duration of chilling, and the phenological characteristics of each species were found to be adapted to the climate conditions of its own geographical area. The phenological model used in this study explained 82‐100% of the variance of the data without taking into account summer temperatures. Thus, although summer temperatures may be well involved in the intensity of dormancy and cold hardiness, they do not significantly aect Budburst and therefore may not need to be considered in phenological models for predicting Budburst.
P Cour - One of the best experts on this subject based on the ideXlab platform.
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climatic determinants of Budburst seasonality in four temperate zone tree species
New Phytologist, 1999Co-Authors: Isabelle Chuine, P CourAbstract:summary Several physiological processes controlling tree phenology remain poorly understood and in particular bud dormancy. Many studies have emphasised the action of chilling temperatures in breaking dormancy. However, the eect of the preceding summer temperatures has rarely been investigated although there is some evidence that they may be involved in the settlement and intensity of dormancy as well as cold acclimation. In this paper, thermal time to Budburst in relation to the duration of chilling outdoors, preceding summer temperatures and forcing temperatures was studied by outdoors experiments in seedlings of Platanus acerifolia, Vitis vinifera, Quercus pubescens and Castanea sativa. Results showed that temperatures of the preceding summer had no significant eect on the timing of Budburst, P. acerifolia and Q. pubescens showed a very weak response to the duration of chilling, and the phenological characteristics of each species were found to be adapted to the climate conditions of its own geographical area. The phenological model used in this study explained 82‐100% of the variance of the data without taking into account summer temperatures. Thus, although summer temperatures may be well involved in the intensity of dormancy and cold hardiness, they do not significantly aect Budburst and therefore may not need to be considered in phenological models for predicting Budburst.
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Climatic determinants of Budburst seasonality in four temperate‐zone tree species
New Phytologist, 1999Co-Authors: Isabelle Chuine, P CourAbstract:summary Several physiological processes controlling tree phenology remain poorly understood and in particular bud dormancy. Many studies have emphasised the action of chilling temperatures in breaking dormancy. However, the eect of the preceding summer temperatures has rarely been investigated although there is some evidence that they may be involved in the settlement and intensity of dormancy as well as cold acclimation. In this paper, thermal time to Budburst in relation to the duration of chilling outdoors, preceding summer temperatures and forcing temperatures was studied by outdoors experiments in seedlings of Platanus acerifolia, Vitis vinifera, Quercus pubescens and Castanea sativa. Results showed that temperatures of the preceding summer had no significant eect on the timing of Budburst, P. acerifolia and Q. pubescens showed a very weak response to the duration of chilling, and the phenological characteristics of each species were found to be adapted to the climate conditions of its own geographical area. The phenological model used in this study explained 82‐100% of the variance of the data without taking into account summer temperatures. Thus, although summer temperatures may be well involved in the intensity of dormancy and cold hardiness, they do not significantly aect Budburst and therefore may not need to be considered in phenological models for predicting Budburst.
Ivan A Janssens - One of the best experts on this subject based on the ideXlab platform.
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the impact of winter and spring temperatures on temperate tree Budburst dates results from an experimental climate manipulation
PLOS ONE, 2012Co-Authors: Yongshuo H Fu, Matteo Campioli, Gaby Deckmyn, Ivan A JanssensAbstract:Budburst phenology is a key driver of ecosystem structure and functioning, and it is sensitive to global change. Both cold winter temperatures (chilling) and spring warming (forcing) are important for Budburst. Future climate warming is expected to have a contrasting effect on chilling and forcing, and subsequently to have a non-linear effect on Budburst timing. To clarify the different effects of warming during chilling and forcing phases of Budburst phenology in deciduous trees, (i) we conducted a temperature manipulation experiment, with separate winter and spring warming treatments on well irrigated and fertilized saplings of beech, birch and oak, and (ii) we analyzed the observations with five temperature-based Budburst models (Thermal Time model, Parallel model, Sequential model, Alternating model, and Unified model). The results show that both winter warming and spring warming significantly advanced Budburst date, with the combination of winter plus spring warming accelerating Budburst most. As expected, all three species were more sensitive to spring warming than to winter warming. Although the different chilling requirement, the warming sensitivity was not significantly different among the studied species. Model evaluation showed that both one- and two- phase models (without and with chilling, respectively) are able to accurately predict Budburst. For beech, the Sequential model reproduced Budburst dates best. For oak and birch, both Sequential model and the Thermal Time model yielded good fit with the data but the latter was slightly better in case of high parameter uncertainty. However, for late-flushing species, the Sequential model is likely be the most appropriate to predict Budburst data in a future warmer climate.
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bayesian comparison of six different temperature based Budburst models for four temperate tree species
Ecological Modelling, 2012Co-Authors: Yongshuo H Fu, Matteo Campioli, Gaby Deckmyn, Marcel Van Oijen, Ivan A JanssensAbstract:Abstract Phenology models are tools to analyze changes in the timing and duration of the growing season. During the past three decades different Budburst models have been developed, but, so far, no consensus model has been found to accurately predict Budburst date across different tree species. The aim of this study was to estimate the performance of six different temperature-driven models of leaf Budburst (thermal time, thermal period fixed, sequential, parallel, alternating, unified) for four temperate tree species in Belgium (birch, chestnut, oak, beech). The models were parameterized using a Bayesian approach. The performance of these models was compared using Bayesian model comparison (BMC) and root mean square error (RMSE). Model comparison showed that the two models that do not include a calculation of chilling requirement were the best for the studied four tree species. The Sequential model (SM) was the third most plausible model for predicting Budburst, having a higher probability to be correct than the other two-phase models combining a chilling phase with a forcing phase. This suggested that in our Budburst observation dataset, the chilling requirement was probably always fulfilled, making the date of Budburst controlled by forcing temperature. We cannot rule out that in warmer regions or future warmer conditions, chilling may become insufficient and a sequential pattern of chilling and forcing may become most appropriate to simulate Budburst date. Parameter analysis showed that the last month prior to Budburst had the greatest impact on determining the date of bud opening in the case of birch and chestnut, whereas the last 3 months were the main determinants for oak and beech, the two later flushing species. Validation showed that the models that fitted the parameterization data well had much poorer performance when tested with independent data. This indicates that other factors (e.g. photoperiod) might affect the Budburst process and/or model parameterization (determining the sensitivity of Budburst to temperature) substantially change between different localities.
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bayesian calibration of the unified Budburst model in six temperate tree species
International Journal of Biometeorology, 2012Co-Authors: Yongshuo H Fu, Matteo Campioli, Ivan A Janssens, Gaston R Demaree, Alex Deckmyn, Rafiq Hamdi, Gaby DeckmynAbstract:Numerous phenology models developed to predict the Budburst date of trees have been merged into one Unified model (Chuine, 2000, J. Theor. Biol. 207, 337–347). In this study, we tested a simplified version of the Unified model (Unichill model) on six woody species. Budburst and temperature data were available for five sites across Belgium from 1957 to 1995. We calibrated the Unichill model using a Bayesian calibration procedure, which reduced the uncertainty of the parameter coefficients and quantified the prediction uncertainty. The model performance differed among species. For two species (chestnut and black locust), the model showed good performance when tested against independent data not used for calibration. For the four other species (beech, oak, birch, ash), the model performed poorly. Model performance improved substantially for most species when using site-specific parameter coefficients instead of across-site parameter coefficients. This suggested that Budburst is influenced by local environment and/or genetic differences among populations. Chestnut, black locust and birch were found to be temperature-driven species, and we therefore analyzed the sensitivity of Budburst date to forcing temperature in those three species. Model results showed that Budburst advanced with increasing temperature for 1–3 days °C−1, which agreed with the observed trends. In synthesis, our results suggest that the Unichill model can be successfully applied to chestnut and black locust (with both across-site and site-specific calibration) and to birch (with site-specific calibration). For other species, temperature is not the only determinant of Budburst and additional influencing factors will need to be included in the model.
Karen M. Clancy - One of the best experts on this subject based on the ideXlab platform.
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variation in Budburst phenology of douglas fir related to western spruce budworm lepidoptera tortricidae fitness
Journal of Economic Entomology, 2003Co-Authors: Zhong Chen, Karen M. Clancy, Thomas E KolbAbstract:Abstract Variation in Budburst phenology among individual trees of interior Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) may influence their susceptibility to western spruce budworm (Choristoneura occidentalis Freeman) defoliation. We tested the hypothesis that phenological asynchrony between Douglas-fir and the western spruce budworm is a mechanism of resistance using clones derived from parent trees that showed resistance versus susceptibility to C. occidentalis defoliation in the field. Susceptible clones had earlier Budburst phenology compared with resistant clones when they were grown in a common greenhouse environment, demonstrating a genetic basis for parallel phenological differences exhibited by the parent trees. We tested the importance of phenological asynchrony as a factor influencing fitness of C. occidentalis using two different greenhouse bioassay experiments. One experiment compared western spruce budworm performance on equivalent phenological stages of susceptible and ...
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The Role of Monoterpenes in Resistance of Douglas Fir to Western Spruce Budworm Defoliation
Journal of Chemical Ecology, 2002Co-Authors: Zhong Chen, Thomas E Kolb, Karen M. ClancyAbstract:We conducted defoliation experiments with 7- to 8-year-old clones of Douglas fir [ Pseudotsuga menziesii (Mirb.) Franco var. glauca ] to assess the role of monoterpenes as a resistance mechanism to western spruce budworm ( Choristoneura occidentalis Freeman) defoliation. The grafted clones were derived from mature trees that showed resistance or susceptibility to budworm defoliation in the forest. All clones were exposed to either budworm defoliation or nondefoliation treatments in 1998 and 1999 under greenhouse conditions. We found that the total concentration of monoterpenes in current-year foliage varied greatly between two consecutive years in clones in the greenhouse and in their corresponding mature trees in the forest. Fractional composition of different monoterpenes was similar between different years and between clones and mature trees, indicating genetic control of this trait. Two different defoliation experiments were conducted to assess the importance of Budburst phenology as a factor determining host plant resistance. In the 1998 experiment, budworm feeding was matched to the Budburst of each individual plant. Monoterpene concentration was high in 1998, and budworm potential fitness was greater on clones from the resistant mature trees that had lower concentrations of total monoterpenes. In the 1999 experiment, budworm feeding was matched to Budburst of the whole population of plants in order to mimic conditions similar to insects feeding on trees in the field. The concentration of monoterpenes was low in 1999, and budworm fitness was not related to monoterpenes. Total monoterpene concentration was negatively related to foliar nitrogen concentration, suggesting that C/N balance may affect monoterpene synthesis in needles. However, tree growth was not related to total monoterpene concentration. We concluded that expression of differences in budworm resistance among Douglas fir genotypes might be caused by interactions among multiple resistance mechanisms such as needle monoterpenes and tree Budburst phenology.
Yongshuo H Fu - One of the best experts on this subject based on the ideXlab platform.
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the impact of winter and spring temperatures on temperate tree Budburst dates results from an experimental climate manipulation
PLOS ONE, 2012Co-Authors: Yongshuo H Fu, Matteo Campioli, Gaby Deckmyn, Ivan A JanssensAbstract:Budburst phenology is a key driver of ecosystem structure and functioning, and it is sensitive to global change. Both cold winter temperatures (chilling) and spring warming (forcing) are important for Budburst. Future climate warming is expected to have a contrasting effect on chilling and forcing, and subsequently to have a non-linear effect on Budburst timing. To clarify the different effects of warming during chilling and forcing phases of Budburst phenology in deciduous trees, (i) we conducted a temperature manipulation experiment, with separate winter and spring warming treatments on well irrigated and fertilized saplings of beech, birch and oak, and (ii) we analyzed the observations with five temperature-based Budburst models (Thermal Time model, Parallel model, Sequential model, Alternating model, and Unified model). The results show that both winter warming and spring warming significantly advanced Budburst date, with the combination of winter plus spring warming accelerating Budburst most. As expected, all three species were more sensitive to spring warming than to winter warming. Although the different chilling requirement, the warming sensitivity was not significantly different among the studied species. Model evaluation showed that both one- and two- phase models (without and with chilling, respectively) are able to accurately predict Budburst. For beech, the Sequential model reproduced Budburst dates best. For oak and birch, both Sequential model and the Thermal Time model yielded good fit with the data but the latter was slightly better in case of high parameter uncertainty. However, for late-flushing species, the Sequential model is likely be the most appropriate to predict Budburst data in a future warmer climate.
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bayesian comparison of six different temperature based Budburst models for four temperate tree species
Ecological Modelling, 2012Co-Authors: Yongshuo H Fu, Matteo Campioli, Gaby Deckmyn, Marcel Van Oijen, Ivan A JanssensAbstract:Abstract Phenology models are tools to analyze changes in the timing and duration of the growing season. During the past three decades different Budburst models have been developed, but, so far, no consensus model has been found to accurately predict Budburst date across different tree species. The aim of this study was to estimate the performance of six different temperature-driven models of leaf Budburst (thermal time, thermal period fixed, sequential, parallel, alternating, unified) for four temperate tree species in Belgium (birch, chestnut, oak, beech). The models were parameterized using a Bayesian approach. The performance of these models was compared using Bayesian model comparison (BMC) and root mean square error (RMSE). Model comparison showed that the two models that do not include a calculation of chilling requirement were the best for the studied four tree species. The Sequential model (SM) was the third most plausible model for predicting Budburst, having a higher probability to be correct than the other two-phase models combining a chilling phase with a forcing phase. This suggested that in our Budburst observation dataset, the chilling requirement was probably always fulfilled, making the date of Budburst controlled by forcing temperature. We cannot rule out that in warmer regions or future warmer conditions, chilling may become insufficient and a sequential pattern of chilling and forcing may become most appropriate to simulate Budburst date. Parameter analysis showed that the last month prior to Budburst had the greatest impact on determining the date of bud opening in the case of birch and chestnut, whereas the last 3 months were the main determinants for oak and beech, the two later flushing species. Validation showed that the models that fitted the parameterization data well had much poorer performance when tested with independent data. This indicates that other factors (e.g. photoperiod) might affect the Budburst process and/or model parameterization (determining the sensitivity of Budburst to temperature) substantially change between different localities.
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bayesian calibration of the unified Budburst model in six temperate tree species
International Journal of Biometeorology, 2012Co-Authors: Yongshuo H Fu, Matteo Campioli, Ivan A Janssens, Gaston R Demaree, Alex Deckmyn, Rafiq Hamdi, Gaby DeckmynAbstract:Numerous phenology models developed to predict the Budburst date of trees have been merged into one Unified model (Chuine, 2000, J. Theor. Biol. 207, 337–347). In this study, we tested a simplified version of the Unified model (Unichill model) on six woody species. Budburst and temperature data were available for five sites across Belgium from 1957 to 1995. We calibrated the Unichill model using a Bayesian calibration procedure, which reduced the uncertainty of the parameter coefficients and quantified the prediction uncertainty. The model performance differed among species. For two species (chestnut and black locust), the model showed good performance when tested against independent data not used for calibration. For the four other species (beech, oak, birch, ash), the model performed poorly. Model performance improved substantially for most species when using site-specific parameter coefficients instead of across-site parameter coefficients. This suggested that Budburst is influenced by local environment and/or genetic differences among populations. Chestnut, black locust and birch were found to be temperature-driven species, and we therefore analyzed the sensitivity of Budburst date to forcing temperature in those three species. Model results showed that Budburst advanced with increasing temperature for 1–3 days °C−1, which agreed with the observed trends. In synthesis, our results suggest that the Unichill model can be successfully applied to chestnut and black locust (with both across-site and site-specific calibration) and to birch (with site-specific calibration). For other species, temperature is not the only determinant of Budburst and additional influencing factors will need to be included in the model.
