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Microclimatic effects (light, temperature) are often neglected in phenological studies and little information is known about the impact of resource availability (nutrient and water) on tree’s phenological cycles. - Here we experimentally studied spring and autumn phenology in four temperate trees in response to changes in bud albedo (white-painted vs black-painted buds), light conditions (nonshaded vs c. 70% shaded), water availability (irrigated, control and reduced precipitation) and nutrients (low vs high availability). - We found that higher bud albedo or shade delayed budburst (up to +12 d), indicating that temperature is sensed locally within each bud. Leaf senescence was delayed by high nutrient availability (up to +7 d) and shade conditions (up to +39 d) in all species, except oak. Autumn phenological responses to summer droughts depended on species, with a delay for cherry (+7 d) and an advance for beech (−7 d). - The strong phenological effects of bud albedo and light exposure reveal an important role of microclimatic variation on phenology. In addition to the temperature and photoperiod effects, our results suggest a tight interplay between source and sink processes in regulating the end of the seasonal vegetation cycle, which can be largely influenced by resource availability (light, water and nutrients)., New Phytologist, 232 (2), ISSN:0028-646X, ISSN:1469-8137

As spring frost proves to be an increasing risk throughout Slovenia and Europe, a better assessment of frost risk is needed. The statistical approach presented in this article consists of the conditional probability that the last spring frost occurs before budburst or flowering. The analysis was conducted using two separate phenological models and phenological data of various grapevine (Vitis vinifera L.), apple (Malus domestica), and sweet cherry (Prunus avium L.) varieties in locations across Slovenia. The increase in risk of spring frost for grapevine ranged from 1 to 1980, from 0.06 to 12 for apple, and from 1 to 180 for sweet cherry. Overall, the varieties most prone to frost proved to be Refošk (Teran) and Merlot grapevine varieties as well as the Germersdorf sweet cherry variety. We have identified the location in the hilly region with moderate climate where the Bobovec apple variety is grown as the least exposed to frost. Although counterintuitive, the GDD generally proved somewhat more efficient than the two-phase phenological model BRIN, although not in all cases. For the purpose of the study, the phenological models were calibrated, and the model parameters can serve as invaluable information for further research of this topic. Nasl. z nasl. zaslona. Special issue: Vegetation and Climate Relationships. Opis vira z dne 6. 4. 2023. Bibliografija: str. 17-18. Abstract.

The objective of this work was to evaluate the effect of heat waves on the bud dormancy of grapevines with contrasting chilling requirements. ‘Chardonnay’, ‘Merlot’ and ‘Cabernet Sauvignon’ hardwood cuttings were collected in vineyards of Veranópolis, State of Rio Grande do Sul, Brazil, and were exposed to constant (7.2°C) or alternate (7.2 and 18°C for 12/12 hours) temperatures, combined with zero, one or two days a week at 25°C. Periodically, part of cuttings was transferred to 25°C for daily budburst evaluation. Endodormancy (dormancy controlled by cold) was overcome with 150 chilling hours (CH) at 7.2ºC in ‘Chardonnay’, 300 CH in ‘Merlot’ and 400 CH in ‘Cabernet Sauvignon’. Daily temperature cycles ranging from7.2ºC to 18°C did not affect the endodormancy process. Heat waves of 25°C resulted in increase in CH to overcome endodormancy. The negative effect of heat waves depended on their duration, with heat partially canceling out the chilling accumulation after 36 continuous hours on the dormancy. Such evidence shows that the dormancy evolution is affected by the impact of the heat interspersed with cold, and should be considered in the adjustment and/or development of better-adapted models for the prediction of the budburst potential of the grapevine culture in Southern Brazil. Resumo Este trabalho objetivou avaliar o efeito de ondas de calor na dormência de gemas de videiras com necessidades contrastantes de frio hibernal. Estacas lenhosas de videiras ‘Chardonnay’, ‘Merlot’ e ‘Cabernet Sauvignon’ foram coletadas em vinhedos de Veranópolis-RS, e expostas a temperatura constante (7,2°C) ou alternada (7,2 e 18°C, por 12/12 horas), combinadas com zero, um ou dois dias por semana a 25°C. Periodicamente, parte das estacas era transferida para 25°C, para avaliação da brotação das gemas. A endodormência (dormência controlada pelo frio) foi superada com 150 horas de frio (HF) a 7,2ºC em ‘Chardonnay’, 300 HF em ‘Merlot’ e 400 HF em ‘Cabernet Sauvignon’. Ciclos diários de temperaturas, variando de 7,2ºC, a 18°C não afetaram o processo de endodormência. Ondas de calor de 25°C resultaram em aumento de HF para a superação da endodormência. O efeito negativo das ondas de calor dependeu de sua duração, sendo que o calor anulou parcialmente o acúmulo de frio após 36 horas contínuas na dormência. Tais evidências mostram que a evolução da dormência é afetada pelo impacto do calor intercalado ao frio hibernal, devendo ser considerada no ajuste e/ou no desenvolvimento de modelos mais adaptados para a predição do potencial de brotação de videiras no Sul do Brasil.

The aim of this study was to assess the thermal requirements of the most important grapevine varieties in northwestern Spain to better understand the impact of climate change on their phenology. Different phenological models (GDD, GDD Triangular and UniFORC) were tested and validated to predict budburst and flowering dates of grapevines at the variety level using phenological observations collected from Treixadura, Godello, Loureira and Albariño between 2008 and 2019. The same modeling framework was assessed to obtain the most suitable model for this region. The parametrization of the models was carried out with the Phenological Modeling Platform (PMP) platform by means of an iterative optimization process. Phenological data for all four varieties were used to determine the best-fitted parameters for each variety and model type that best predicted budburst and flowering dates. A model calibration phase was conducted using each variety dataset independently, where the intermediate-fitted parameters for each model formulation were freely-adjusted. Afterwards, the parameter set combination of the model providing the highest performance for each variety was externally validated with the dataset of the other three varieties, which allowed us to establish one overall unique model for budburst and flowering for all varieties. Finally, the performance of this model was compared with the attained one while considering all varieties in one dataset (12 years × 4 varieties giving a total number of observations of 48). For both phenological stages, the results showed no considerable differences between the GDD and Triangular GDD models. The best parameters selected were those provided by the Treixadura GDD model for budburst (day of the year (t0) = 49 and base temperature (Tb) = 5) and those corresponding to the Godello model (t0 = 52 and Tb = 6) for flowering. The modeling approach employed allowed obtaining a global prediction model that can adequately predict budburst and flowering dates for all varieties.

The aim of this study was to assess the thermal requirements of the most important grapevine varieties in northwestern Spain to better understand the impact of climate change on their phenology. Different phenological models (GDD, GDD Triangular and UniFORC) were tested and validated to predict budburst and flowering dates of grapevines at the variety level using phenological observations collected from Treixadura, Godello, Loureira and Albariño between 2008 and 2019. The same modeling framework was assessed to obtain the most suitable model for this region. The parametrization of the models was carried out with the Phenological Modeling Platform (PMP) platform by means of an iterative optimization process. Phenological data for all four varieties were used to determine the best-fitted parameters for each variety and model type that best predicted budburst and flowering dates. A model calibration phase was conducted using each variety dataset independently, where the intermediate-fitted parameters for each model formulation were freely-adjusted. Afterwards, the parameter set combination of the model providing the highest performance for each variety was externally validated with the dataset of the other three varieties, which allowed us to establish one overall unique model for budburst and flowering for all varieties. Finally, the performance of this model was compared with the attained one while considering all varieties in one dataset (12 years × 4 varieties giving a total number of observations of 48). For both phenological stages, the results showed no considerable differences between the GDD and Triangular GDD models. The best parameters selected were those provided by the Treixadura GDD model for budburst (day of the year (t0) = 49 and base temperature (Tb) = 5) and those corresponding to the Godello model (t0 = 52 and Tb = 6) for flowering. The modeling approach employed allowed obtaining a global prediction model that can adequately predict budburst and flowering dates for all varieties. Ministerio de Agricultura, Pesca y Alimentación (España) | Ref. 20190020007473 Xunta de Galicia | Ref. ED431C 2017/62-GRC Xunta de Galicia | Ref. ED481A-2017/209 Fundação para a Ciência e a Tecnologia (Portugal) | Ref. FCT UIDB / 04683/2020 Fundação para a Ciência e a Tecnologia (Portugal) | Ref. UIDP / 04683/2020

Climate change has become a topic of increasing significance in viticulture, severely challenged by this issue. Average global temperatures are increasing, but frost events, with a large variability depending on geographical locations, have been predicted to be a potential risk for grapevine cultivation. Grape cold hardiness encompasses both midwinter and spring frost hardiness, whereas the avoidance of spring frost damage due to late budbreak is crucial in cold resilience. Cold hardiness kinetics and budbreak phenology are closely related and affected by bud’s dormancy state. On the other hand, budbreak progress is also affected by temperatures during both winter and spring. Genetic control of bud phenology in grapevine is still largely undiscovered, but several studies have recently aimed at identifying the molecular drivers of cold hardiness loss and the mechanisms that control deacclimation and budbreak. A review of these related traits and their variability in different genotypes is proposed, possibly contributing to develop the sustainability of grapevine production as climate-related challenges rise.

The objective of this work was to perform preliminary assessment of the performance of different models for the simulation of three main phenology stages (budburst, flowering, and veraison) of grapevine in China. This work utilized observations from five representative wine regions (Changli, Laixi, Shangri-La, Xiaxian, and Yanqi) and four widely cultivated grape cultivars (Cabernet Sauvignon, Cabernet Franc, Merlot, and Chardonnay) in China. The corresponding daily temperature data were used to simulate the timing of grape phenology stages based on the different phenological models. The dates based on the simulation and the actual dates were compared and the performance of these models were assessed for different cultivars and wine regions. The GDD10 model exhibited the best performance for budburst simulation in soil-burying regions, irrespective of the cultivar and location. For flowering and veraison, the optimal model varied in performance between cultivars and locations, and non-linear models exhibited better performance than linear models. In general, the performance of these models was better for the latter two stages than for budburst. The models with relatively good performance were selected for further calibration using these limited Chinese observations. The impact of soil-burying management on budburst simulation was also estimated. These results highlight the strengths of some phenological models for use in China. This study also reiterates the strong need for establishment of a grapevine phenology observation network in China to obtain more comprehensive data.

Ecosystems' potential to provide services, e.g. to sequester carbon, is largely driven by the phonological cycle of vegetation. Timing of phenological events is required for understanding and predicting the influence of climate change on ecosystems and to support analyses of ecosystem functioning. Analyses of conventional camera time series mounted near vegetation has been suggested as a means of monitoring phenological events and supporting wider monitoring of phenological cycle of biomes that is frequently done with satellite earth observation (EO). Especially in the boreal biome, sparsely scattered deciduous trees amongst conifer-dominant forests pose a problem for EO techniques as species phenological signal mix, and render EO data difficult to interpret. Therefore, deriving phonological information from on the ground measurements would provide valuable reference data for earth observed phonology products in a larger scale. Keeping this in mind, we established a network of digital cameras for automated monitoring of phenological activity of vegetation in the boreal ecosystems of Finland. Cameras were mounted at 14 sites, each site having 1-3 cameras. In this study, we used data from 12 sites to investigate how well networked cameras can detect the phenological development of birches (Betula spp.) along a latitudinal gradient. Birches typically appear in small quantities within the dominant species. We tested whether the small, scattered birch image elements allow a reliable extraction of colour indices and the temporal changes therein. We compared automatically derived phenological dates from these birch image elements both to visually determined dates from the same image time series and to independent observations recorded in the phenological monitoring network covering the same region, Automatically extracted season start dates, which were based on the change of green colour fraction in spring, corresponded well with the visually interpreted start of the season, and also to the budburst dates observed in the field. Red colour fraction turned out to be superior to the green colour-based indices in predicting leaf yellowing and fall. The latitudinal gradients derived using automated phenological date extraction corresponded well with the gradients estimated from the phenological field observations. We conclude that small and scattered birch image elements allow reliable extraction of key phonological dates for the season start and end of deciduous species studied here, thus providing important species-specific data for model validation and for explaining the temporal variation in EO phenology products.

Heat requirements for four major phenological stages (budburst, flowering, veraison and harvest) were assessed in eight red grapevine cultivars grown in the Sremski Karlovci region in northern Serbia using a growing degree-days (GDD) method and base temperature of 10 degrees C. Temperature and phenological data covering the period 1986-2007 were used to conduct the study. The accumulated GDD for the beginning of budburst ranged from 70 ('Gamay' and 'Limberger') to 92 ('Cabernet Sauvignon'). The heat requirements for the beginning of flowering varied between 338 GDD in 'Gamay' to 398 GDD in 'Probus'. The smallest heat requirements to reach the beginning of veraison was observed in 'Portugizer' (937 GDD) and the greatest in 'Probus' (1117 GDD). The GDD for harvest spanned the range from 1555 in 'Portugizer' to 1649 in 'Prokupac'. Generally, a greater variation in GDD was found between years for a single cultivar than among cultivars within individual years. Among phenological stages, the greatest inter-annul variation in terms of coefficient of variation was displayed for the beginning of budburst and the least for harvest.

Ponderosa pine (Pinus ponderosa Lawson &amp, C. Lawson var. scopulorum Engelm.) forests of the southwestern US are threatened by climate change and deforestation. Information about geographic patterns of provenance variation in budburst phenology is needed to make decisions about selecting seed sources for future planting. In this study, provenance variation in the budburst phenology of ponderosa pine seedlings was examined using common garden studies. Seedlings from 21 provenances, representing an elevational gradient in Arizona and New Mexico, were planted in July 2018 at a ponderosa pine-dominated field site in northern Arizona. Field budburst was monitored weekly on all seedlings in the spring of 2019. Field budburst was compared with budburst timing of the same provenances measured under greenhouse conditions. The hypotheses for this study were that (1) budburst varies among provenances, with earlier budburst in low-elevation provenances, and (2) differences in budburst timing among provenances are consistent for seedlings grown in greenhouse and field environments. Field results show that provenances vary in budburst date and that low- and middle-elevation provenances break bud sooner than high-elevation provenances. Field budburst date had a moderate, positive correlation with provenance mean annual precipitation (r = 0.522) and a moderate, negative trend with latitude (r = &minus, 0.413). Budburst date of provenances in the greenhouse had a moderate, positive trend with budburst date in the field (r = 0.554), suggesting application of greenhouse results to field plantings. Such information about provenance variation and environmental and geographic trends in budburst timing will be useful for developing species-specific seed transfer guidelines and effective assisted migration strategies in a changing climate.

International audience; According to the Janzen-Connell hypothesis, seedling mortality is greater close to conspecific (or closely related) adult trees because of higher enemy pressure, ultimately increasing local tree-species diversity. However, this pattern (i.e. a decline of seedling performance close to conspecific or closely related adults) could also result from other processes: (1) heterospecific adults might positively affect seedlings; (2) conspecific (or closely related) adults might negatively affect seedlings by causing a deterioration of the microenvironment. We tested these hypotheses, accounting also for sizes of adults. We planted oak-seedlings in a temperate forest, characterized their adult neighbourhoods, measured 26 microenvironmental conditions, seedling mortality during one year, budburst and leaf herbivory. We detected Janzen-Connell-like patterns (frequent lack of budburst close to conspecific adults; high seedling mortality close to closely related adults) that were consistent with the Janzen-Connell process. However, these patterns were either counteracted by non-Janzen-Connell processes such as a favourable microenvironment or were weak with little explained variance. We detected Janzen-Connell-like patterns that were not consistent with the Janzen-Connell process: proximity to heterospecific adults per se decreased leaf herbivory partly due to microenvironmental effects, such that a lower leaf herbivory decreased seedling mortality. Overall, the spatial pattern of tree recruitment may resemble that predicted by Janzen-Connell but result from different processes: notably heterospecific adults creating refuges from enemies, facilitating the establishment of oaks below non-oaks without hindering their establishment below oaks.

International audience; • Premise of the study: The branching pattern and phenology of trees result from interactions between the tree’s genetic constitution and environmental conditions. Temperature strongly affects the duration of bud dormancy and further shoot growth. Our hypothesis was that shoot architecture is strongly affected by winter temperatures determining both the position and budburst of vegetative laterals with a lower effect on their outgrowth. • Methods: The study was conducted on four apple cultivars characterized by various chilling requirements and grown in two contrasting winter temperature conditions. A two-step approach was designed to quantify at the shoot scale first the branching pattern and second two phenological stages of vegetative laterals, budburst and outgrowth. A categorical variable, the branching zone, was built to summarize the lateral position along the shoot. It was integrated into the phenological analysis as a factor together with the cultivar and the winter temperature. • Key results: Temperature had a main effect on the distribution of vegetative laterals along the shoot. It also strongly affected budburst, which was also affected by the cultivar and the branching zone. The outgrowth of the lateral was not significantly affected by temperature but was significantly affected by the cultivar and the branching zone. Furthermore, the delayed senescence and subsequent leaf persistence during winter, characterizing the apple tree in the mild winter temperature condition, had only a weak effect on the distribution of vegetative laterals and on budburst and lateral outgrowth. • Conclusions: The actual shoot architecture and budburst result from an ordered sequence of events with a pivotal role of winter temperatures on the dormancy completion of individual lateral buds. Endogenous factors related to the cultivar branching pattern overtake the temperature effect on the lateral outgrowth.

Understanding the relationships between bud size and position and bud fate through time is crucial for identifying and subsequently modeling the mechanisms underlying tree architecture. However, there is a lack of information on how bud size drives crown architectural patterns in coexisting tree species. We studied bud demography in two coexisting Mediterranean oak species with contrasting leaf habit (Quercus ilex, evergreen; Q. faginea, deciduous). The main objective was to analyse the effect of bud size on the fate of buds with different positions along the shoot (apical, leaf axillary and scale-cataphyll axillary buds). The number, length and position of all buds and stems were recorded in marked branches during 4 years. Study species presented different strategies in bud production and lifespan. The evergreen species showed greater mortality rate than the deciduous one, which produced larger buds. Bud size and position were highly related since apical buds where longer than axillary ones and bud length declined basipetally along the stem. Apical buds had also higher chances of bursting than axillary ones. Within positions, longer buds presented a higher probability of bursting than shorter ones, although no absolute size threshold was found below which bud bursting was impaired. In Q. ilex, four-year-old buds were still viable and able to burst, whereas in Q. faginea practically all buds burst in their first year or died soon after. Such different bud longevities may indicate contrasting strategies in primary growth between both species. Q. ilex is able to accumulate viable buds for several ages, whereas Q. faginea seems to rely on the production of large current-year buds with high bursting probability under favourable environmental conditions. © 2013 Springer-Verlag Berlin Heidelberg., A.Q.A., J.J.C. and S.P. acknowledge the support of MAEC-AECID, ARAID and the Spanish Ministerio de Ciencia e Innovación (Juan de la Cierva subprogram), respectively. This work was supported by the Spanish Ministerio de Ciencia e Innovación and FEDER (grant numbers CGL2008-04847-C02-01, CGL2010-16880 BOS, CGL2011-26654 BOS). We thank the collaborative support of the Globimed network (http://​www.​globimed.​net) and the Spanish “Agencia Estatal de Meterorología” for providing climatic data. The authors are grateful to Guillermo Bueno for statistical advice, Jorge Albuixech for help during field work, an anonymous Communicating Editor and two anonymous reviewers for helpful comments on an earlier version of the manuscript.

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.

Climate change has been shown to affect the phenology of many organisms, but interestingly these shifts are often unequal across trophic levels, causing a mismatch between the phenology of organisms and their food.We consider two alternative hypotheses: consumers are constrained to adjust sufficiently to the lower trophic level, or prey species react more strongly than their predators to reduce predation. We discuss both hypotheses with our analyses of changes in phenology across four trophic levels: tree budburst, peak biomass of herbivorous caterpillars, breeding phenology of four insectivorous bird species and an avian predator.In our long-term study, we show that between 1988 and 2005, budburst advanced (not significantly) with 0.17 d yr(-1), while between 1985 and 2005 both caterpillars (0.75 d year(-1)) and the hatching date of the passerine species (range for four species: 0.36-0.50 d year(-1)) have advanced, whereas raptor hatching dates showed no trend.The caterpillar peak date was closely correlated with budburst date, as were the passerine hatching dates with the peak caterpillar biomass date. In all these cases, however, the slopes were significantly less than unity, showing that the response of the consumers is weaker than that of their food. This was also true for the avian predator, for which hatching dates were not correlated with the peak availability of fledgling passerines. As a result, the match between food demand and availability deteriorated over time for both the passerines and the avian predators.These results could equally well be explained by consumers' insufficient responses as a consequence of constraints in adapting to climate change, or by them trying to escape predation from a higher trophic level, or both. Selection on phenology could thus be both from matches of phenology with higher and lower levels, and quantifying these can shed new light on why some organisms do adjust their phenology to climate change, while others do not.

Budburst is a key adaptive trait that can help us understand how plants respond to a changing climate from the molecular to landscape scale. Despite this, acquisition of budburst data is constrained by a lack of information at the plant scale on the environmental stimuli associated with the release of bud dormancy. Additionally, to date, little effort has been devoted to phenotyping plants in natural populations due to the challenge of accounting for the effect of environmental variation. Nonetheless, natural selection operates on natural populations, and investigation of adaptive phenotypes in situ is warranted and can validate results from controlled laboratory experiments. To identify genomic effects on individual plant phenotypes in nature, environmental drivers must be concurrently measured, and characterized. Here, we designed and evaluated a sensor to meet these requirements for temperate woody plants. It was designed for use on a tree branch to measure the timing of budburst together with its key environmental drivers; temperature, and photoperiod. Specifically, we evaluated the sensor through independent corroboration with time-lapse photography and a suite of environmental sampling instruments. We also tested whether the presence of the device on a branch influenced the timing of budburst. Our results indicated the following: the temperatures measured by the budburst sensor’s digital thermometer closely approximated the temperatures measured using a thermocouple touching plant tissue; the photoperiod detector measured ambient light with the same accuracy as did time lapse photography; the budburst sensor accurately detected the timing of budburst; and the sensor itself did not influence the budburst timing of Populus clones. Among other potential applications, future use of the sensor may provide plant phenotyping at the landscape level for integration with landscape genomics.

Phenological observations in olive tree (Olea europaea L.), on the first reproductive phase (budburst) and the winter chilling temperatures required for its onset, were analysed over a 4-year period (1998 - 2001). Research was carried out on two different cultivars growing in two Mediterranean olive-growing areas: 'Ascolana' in central Italy and 'Picudo' in southern Spain. The two main objectives of the study were: (1) to evaluate the different amounts of winter chilling, and their relationship with the budburst dates in outdoor olive plantations; and (2) to test the validity in the study areas of two chilling calculation methods, the Aron and the Utah method. Results show that for the Spanish cultivar the average chilling requirement of 997 h was approximately half of that recorded for the Italian cultivar (1848 h). Also, the year-to-year variability in chilling accumulation and the reproductive development date was observed to be higher in the Spanish area than in the Italian one, indicating a more cons...

O objetivo deste trabalho foi determinar a dinâmica da dormência de gemas em ramos de dois anos de macieira 'Imperial Gala' com ou sem frio suplementar durante o outono e inverno, cultivadas em Porto Amazonas - PR, região de baixa ocorrência de frio. Os ramos foram coletados em intervalos de 21 dias, de abril a agosto (19-04, 10-05, 31-05, 21-06, 12-07, 02-08 e 23-08) e receberam ou não tratamento com frio suplementar de 1.440 horas, à temperatura de 4 a 7° C. A avaliação da dormência foi realizada pelo teste biológico de estacas de nós isolados (temperatura de 25° C e fotoperíodo de 16 horas) por meio dos parâmetros: tempo médio para brotação (TMB), velocidade de brotação (VB), taxa final de brotação (TF), taxa de brotações vigorosas (TBV) e tempo médio para aparecimento de folhas abertas (TMFA). A dormência mais intensa de gemas de dois anos ocorre no final de maio, com oscilações até o início de agosto. A aplicação de 1.440 horas de frio suplementar de 4 a 7° C altera a dinâmica da dormência das gemas de dois anos, reduzindo o seu tempo médio de brotação. Uma vez propiciada a brotação de gemas não-dormentes de dois anos, as mesmas possuem boa capacidade para se desenvolver. This work aims to evaluate the dormancy dynamics of two year old apple tree buds with or without supplementary chill during autumn and winter, in a region of low chill occurence. The stems were collected in Porto Amazonas, Parana State, Brazil, at intervals of 21 days from April to August (April 19th, May 10th, May 31st, June 21st, July 12th, August 2nd and August 23rd) and were either treated or not with 1,440 hours of chill (4 to 7° C). The evaluation of dormancy was observed through the biological test of single node cuttings under controlled conditions (25° C and long days of 16 hours) by the following parameters: average time for budburst (TMB), velocity of budburst (VB), final rate of budburst (TF), rate of vigorous budburst (TBV) and average time for open leaves to appear (TMFA). The most intense dormancy occured on May 31st, but presented variations until August. The chilly treatment with 1,440 hours (4 to 7° C) was effective in reducing the average time for budburst. Non-dormant buds under favorable developing conditions present good growth potencial.

The process of adaptation is the result of stabilising selection caused by two opposite forces: protection against an unfavourable season (survival adaptation), and effective use of growing resources (capacity adaptation). As plant species have evolved different life strategies based on different trade offs between survival and capacity adaptations, different phenological responses are also expected among species. The aim of this study was to compare budburst responses of two opportunistic species (Betula pubescens, and Salix x smithiana) with that of two long-lived, late successional species (Fagus sylvatica and Tilia cordata) and consider their ecological significance. Thus, we performed a series of experiments whereby temperature and photoperiod were manipulated during dormancy. T. cordata and F. sylvatica showed low rates of budburst, high chilling requirements and responsiveness to light intensity, while B. pubescens and S. x smithiana had high rates of budburst, low chilling requirements and were not affected by light intensity. In addition, budburst in B. pubescens and S. x smithiana was more responsive to high forcing temperatures than in T. cordata and F. sylvatica. These results suggest that the timing of growth onset in B. pubescens and S. x smithiana (opportunistic) is regulated through a less conservative mechanism than in T. cordata and F. sylvatica (long-lived, late successional), and that these species trade a higher risk of frost damage for the opportunity of vigorous growth at the beginning of spring, before canopy closure. This information should be considered when assessing the impacts of climate change on vegetation or developing phenological models.

International audience; The budburst stage is a key phenological stage for grapevine (Vitis vinifera L.), with large site and cultivar variability. The objective of the present work was to provide a reliable agro-meteorological model for simulating grapevine budburst occurrence all over France. The study was conducted using data from ten cultivars of grapevine (Cabernet Sauvignon, Chasselas, Chardonnay, Grenache, Merlot, Pinot Noir, Riesling, Sauvignon, Syrah, Ugni Blanc) and five locations (Bordeaux, Colmar, Angers, Montpellier, Epernay). First, we tested two commonly used models that do not take into account dormancy: growing degree days with a base temperature of 10°C (GDD10), and Riou’s model (RIOU). The errors of predictions of these models ranged between 9 and 21 days. Second, a new model (BRIN) was studied relying on well-known formalisms for orchard trees and taking into account the dormancy period. The BRIN model showed better performance in predicting budburst date than previous grapevine models. Analysis of the components of BRIN formalisms (calculation of dormancy, use of hourly temperatures, base temperature) explained the better performances obtained with the BRIN model. Base temperature was the main driver, while dormancy period was not significant in simulating budburst date. For each cultivar, we provide the parameter estimates that showed the best performance for both the BRIN model and the GDD model with a base temperature of 5°C

In temperate trees, the timings of plant growth onset and cessation affect biogeochemical cycles, water, and energy balance. Currently, phenological studies largely focus on specific phenophases and on their responses to warming. How differently spring phenology responds to the warming and cooling, and affects the subsequent phases, has not been yet investigated in trees. Here, we exposed saplings of Fagus sylvatica L. to warmer and cooler climate during the winter 2013-2014 by conducting a reciprocal transplant experiment between two elevations (1,340 vs. 371m a.s.l., ca. 6 degrees C difference) in the Swiss Jura mountains. To test the legacy effects of earlier or later budburst on the budset timing, saplings were moved back to their original elevation shortly after the occurrence of budburst in spring 2014. One degree decrease in air temperature in winter/spring resulted in a delay of 10.9 days in budburst dates, whereas one degree of warming advanced the date by 8.8 days. Interestingly, we also found an asymmetric effect of the warmer winter vs. cooler winter on the budset timing in late summer. Budset of saplings that experienced a cooler winter was delayed by 31days compared to the control, whereas it was delayed by only 10 days in saplings that experienced a warmer winter. Budburst timing in 2015 was not significantly impacted by the artificial advance or delay of the budburst timing in 2014, indicating that the legacy effects of the different phenophases might be reset during each winter. Adapting phenological models to the whole annual phenological cycle, and considering the different response to cooling and warming, would improve predictions of tree phenology under future climate warming conditions.