This session is organized by a consortium representing the International Society of Biometeorology (Phenology Commission), the Pan-European Phenology Network - PEP725, the Swiss Academy of Science SCNAT, the TEMPO French Phenology Network and the USA National Phenology Network.
Over recent decades, autumn leaf senescence of temperate deciduous trees has generally been delayed. Whilst post-summer solstice warming slows the progression of senescence, pre-solstice warming has been shown to advance senescence onset by increasing developmental rates. Severe heat and drought events, which have been increasing in frequency and intensity, can also advance senescence through stress. Yet, it remains unclear whether premature senescence is primarily driven by faster development or by climatic stress, limiting accurate projections of future premature leaf senescence frequencies. We analysed leaf senescence observations for four dominant deciduous tree species (horse chestnut, silver birch, European beech, and English oak) across >3000 sites in central Europe from 1951–2023. For all species, the proportion of premature senescence events (occurrences within the earliest 5% percentile) has slightly decreased over time (trend: -0.11-0% yr-1). Pre-solstice climate variables had the largest effects on premature senescence likelihood, with post-solstice effects diminishing over time. Pre-solstice growing degree days were the most influential factor, associated with a 30-40% increase in premature senescence likelihood per standard deviation (sd) increase. Nighttime temperatures were as important as daytime temperatures. Leaf-out date was the next most significant factor (25% increase per sd). Water deficit had smaller effects (5-12% sd-1), aligning with our experimental results showing that drought conditions do not cause premature senescence when nutrient availability is high. These results suggest that pre-solstice developmental processes exert a larger effect on premature senescence than summer climatic stress. Nevertheless, ongoing early-season warming and the increasing frequency of heatwaves and droughts is likely to intensify premature leaf senescence in European trees. Such shifts could have key impacts on biogeochemical cycles and community interactions within forest ecosystems.
How to cite: Rebindaine, D., W. Crowther, T., Mo, L., and M. Zohner, C.: Premature leaf senescence in temperate trees is strongly driven by pre-solstice heat and drought while post-solstice effects disappeared over recent decades, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11008, https://doi.org/10.5194/egusphere-egu25-11008, 2025.
Frosts occurring after spring leaf onset significantly jeopardize tree growth, forest productivity, and ecosystem functions. As the climate warms, earlier leaf onset has become increasingly common, exposing plants to heightened risks of frost damage. However, the impacts of spring frosts occurring after leaf onset on later senescence phenology in deciduous forests remain largely unexplored. Using 20 years of remotely sensed phenology data, we demonstrate that, in European beech forests, late spring frost events disrupt predictable patterns of leaf onset and senescence, weakening the carryover effect between the start and end of the growing season. Interestingly, the frequency and intensity of these frost events did not significantly exacerbate this disruption. In contrast, favorable summer conditions were found to partially restore the natural interdependency between leaf onset and senescence. Our findings reveal how plant phenology is profoundly affected by climate change not only as an emerging process but also in terms of its internal dynamics. We aspire for our study to lay the groundwork for highlighting the key role of biological start-end of season carryover effects in the phenology responses to climate change, advocating for their incorporation into the development of phenology models.
How to cite: Bajocco, S., Ferrara, C., Crecco, L., Bregaglio, S., and Bascietto, M.: Late frosts weaken spring leaf onset carryover effect on autumn senescence , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12319, https://doi.org/10.5194/egusphere-egu25-12319, 2025.
Emerging evidence suggests that temperature increases due to climate change not only differ strongly between regions but also across seasons. As a rule of thumb, one could argue that colder seasons (e.g., winter) tend to warm up faster than warmer seasons, although there are notable exceptions to this rule (e.g., due to changes in the polar vortex). The implications of such seasonal differences in warming trends for plant phenology, i.e., the timing of key events during the plant seasonal cycle, however remain poorly understood. A gap in knowledge that arises, in part, because we lack a global overview of the period(s) of the year during which changing temperatures impact on the phenological cycle of plants the most.
Here, we provide a global analysis of the interrelationships between seasonal temperature changes and global land surface phenology using satellite data from the period 2001-2019. More specifically, we determined the annual period of highest correlation between temperature fluctuations and the onset of different phenological stages within a 100km radius around 10.000 point locations. We found that, across most of the Northern Hemisphere’s mid and high latitudes, a wide range of these stages, i.e., from the onset of ‘greenup’ to ‘greendown’, correlate strongly with temperature fluctuations during roughly the same period of the year, i.e., up until a few weeks before or after the onset of greenup. We found that warming rates during this period were roughly 1.5-2.5 times faster than regional mean annual temperature increases, which, in turn, were roughly 1.5-2.0 times faster than the increase in global mean annual temperature (which includes air above the oceans).
When assessing the impact of global mean annual temperature changes on global land surface phenology, it is thus crucial to consider seasonal differences in warming. These differences are likely to affect not only plant phenology but also many other key processes related to plant growth and development.
How to cite: Lever, J., Gilarranz, L., D'Odorico, P., Psomas, A., Ginzler, C., Simis, S., Damm, A., Gessler, A., Odermatt, D., and Vitasse, Y.: Seasonal warming and global land surface phenology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17138, https://doi.org/10.5194/egusphere-egu25-17138, 2025.
The Mediterranean oak savanna is Europe's most extensive agroforestry system, with significant economic, social, and ecological relevance. Climate models indicate that the Mediterranean region is particularly vulnerable to the impacts of global warming, which include increased frequency and severity of droughts. Consequently, there is a pressing need for conservation measures to prevent the degradation of this ecosystem, reduce uncertainty about production, and ensure its sustainable development. One of the most valuable resources of this system is the acorn of holm oaks, which significantly contributes to the quality of extensive livestock products. The intensity of oak flowering is a key factor limiting maximum acorn production, and it is usually monitored by visual sampling in the field, a costly and time-consuming method. To address this challenge, this study aims to evaluate the potential of remote sensors onboard UAVs (unmanned aerial vehicles) and high-resolution satellite sensors for monitoring the flowering of holm oak trees. This approach aims to scale up the monitoring effort, simultaneously providing valuable information to many farmers.
Previous works have explored the use of digital cameras for monitoring phenology, particularly in combination with airborne data. Gómez-Giráldez et al. (2021) proposed an index designed to automatically quantify the male flowering intensity of holm oaks based on the closeness to pure yellow in RGB images captured by UAVs. This index showed sufficient accuracy in differentiating between various flowering intensity levels and providing intensity maps. However, the index requires further validation before it can be applied on a larger scale.
This study extends the validation of the proposed index using UAV data and high-resolution satellite imagery. It was conducted on six plots located in southern Spain. During 2022 and 2024, 11 images were taken over the three previously studied plots and three additional plots to enhance the validation. The results indicated that trees with lower flowering intensity were concentrated in areas with higher yellow distances, which confirmed previous results. However, due to the high phenological variability among individuals, we observed the importance of synchronizing the image acquisition date with the peak flowering period. Two high-quality orthoimages with a resolution of 1.5 m were acquired from the SPOT 6 satellite in 2024 to extend the methodology to larger areas and provide intensity maps.
The expanded evaluation and visual verification showed promising results. The index, which can be derived using just an RGB image, shows potential for future applications related to phenology and productivity. Furthermore, developing an automated tool for this task would be beneficial in covering large areas and improving the representativeness of the estimates.
How to cite: Calbet, A., Gonzalez-Dugo, M. P., Carbonero, M. D., García-Moreno, A. M., Muñoz-Gómez, M. J., and Andreu, A.: Evaluation of high-resolution imagery for monitoring the flowering of holm oak trees, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12728, https://doi.org/10.5194/egusphere-egu25-12728, 2025.
The annual dormancy cycle of apple trees is highly temperature dependent, with photoperiod deemed irrelevant for dormancy induction or breaking. In fall, cold days induce endodormancy. Endodormancy, in turn, is overcome by further accumulation of chill, when a cultivar-specific chill requirement is met. To further overcome ecodormancy, a cultivar-specific heat requirement must be met, allowing for bud break and subsequent phenology phases to occur. Thus, compared to species where photoperiod is relevant for the dormancy cycle, apple tree dormancy and spring phenology phases are especially susceptible to climate change.
Chill and heat requirements reported in the literature vary between cultivars, within cultivars with location and even for the same cultivar and location depending on the methodological approach. This is, inter alia, related to an imprecision regarding terminology. The minimum chill and heat to respectively overcome endodormancy and ecodormancy are referred to as chill requirement and heat requirement. Yet, studies often report a chill or heat accumulation that – if a phenological phase occurred – at least met the respective requirement. Thus, the existing literature can provide approximations of the actual chill and heat requirements. However, a large database of phenology observations might include instances at the limit for the occurrence of specific phenological phases. Thus, such a database may most accurately approach a cultivar’s actual chill requirement.
In this work we capitalize on a phenology database by the German Weather Service (DWD) that is openly available. This database entails over 50,000 observations for each bud break, bloom start and full bloom spanning the years 1996 to 2024. While there are data on over 60 apple cultivars, we deemed the data for 23 cultivars sufficient for model development. As source for temperature data, we used a temperature grid with 1x1 km spatial resolution developed by the DWD. As underlying modelling approach, we used the chill overlap model. This model is not merely fitting data statistically, but provides a biological meaningful framework.
This biological footing is crucial to extrapolate findings to different climatic conditions. Therefore, the spring phenology models developed in this work will allow to predict onset of spring phenology phases in a warmer future. Consequently, in the future the risk of late frost events or the risk of approaching climatic conditions that will hinder bud break can be investigated for each cultivar. Thus, a cultivar-specific risk assessment regarding likely future conditions can inform planting decisions.
How to cite: Ohnemus, T., Paasch, S., and Mollenhauer, H.: Spring Phenology Models for Temperate Apple Cultivars, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5852, https://doi.org/10.5194/egusphere-egu25-5852, 2025.
In the Piedmont region, located in northwestern Italy, meteorological data are available from two regional databases: the stations belonging to the agrometeorological network (RAM) and those belonging to the regional meteorological service (ARPA). The former are located in areas of agricultural interest, and the latter everywhere. By combining the two series, and adopting interpolation procedures for missing or unmeasured data, it was possible to reconstruct a complete database of hourly observations in the period 2004-2024 relating to the following quantities: temperature, humidity and pressure at the screen level, precipitation, solar radiation, and wind speed in about fifty stations located in the most renowned wine-growing areas. These data were integrated with the soil texture values available in the SoilGrids database, which is a system for digital soil mapping based on a global compilation of soil profile data and environmental layers. Although the period does not have the necessary temporal dimension (30 years) to be considered strictly climatic, its length is sufficient to be able to make some preliminary considerations in this sense. Using the above mentioned data, it was possible to perform twenty-year simulations on each station using the land surface model UTOPIA (University of TOrino land surface Process Interaction model in Atmosphere), in order to obtain the energy and mass fluxes in the vegetation layer, and the subsoil temperatures and humidity in the root layer. In turn, the inputs and outputs of the previous simulations were used to perform further simulations with the crop growth model IVINE (Italian Vineyard Integrated Numerical model for Estimating physiological values), in order to obtain the trend of the main pheno-physiological parameters for each station in the twenty-year period considered. During the presentation, the evolution over the period of some variables relevant to vineyard cultivation practices will be shown, such as some components of the energy and hydrological balances (such as heat fluxes and evaporation), temperatures and humidity of the subsoil, as well as the main phenological phases and some physiological values (sugar content, mass, yield, ...) in a selection of stations showing the most significant results.
How to cite: Cassardo, C. and Andreoli, V.: Behavior of pheno-physiological parameters and surface-layer variables on vineyard environments in Piedmont (Italy) using numerical models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13031, https://doi.org/10.5194/egusphere-egu25-13031, 2025.
The OPRAM (Online Pest Risk Analysis Model) project is developing an open source web application, which will be used in guiding risk assessment and surveillance of high priority plant pests across Ireland. Current models predict the timing of adult emergence during the year using an accumulative growing degree day model, but overwintering is not typically included (for example : https://www.usanpn.org/vis-tool). The inclusion of overwintering is particularly important when predicting a plant pest’s end-of-year phenology and for making predictions across multiple years.
We developed template models for the three main overwintering life-histories for insects. Quiescence implies that an insect may be present all year round if temperatures are high enough;e.g. Spodoptera frugiperda may not reach the required threshold.. In addition, the inclusion of the fractional number of generations per year is especially important as it indicates regions which maybe close to completing a generation based on the threshold rather than presenting a null value.
The inclusion of obligate and facultative diapause imply the season will end earlier due to the decrease in photoperiod or because of the combined effects of photoperiod and temperature for species like Leptinotarsa decemlineata and Oulema melanopus. This would impact the overall risk assessment depending on how many generations of a species may appear during the year and the mitigative measures undertaken. For instance, Ips typographus, has greater damage if a second generation were to emerge. If diapause were not ncluded in these models then this variation in year-to-year seasonal length may not be captured.
We give examples for six template species: Agrilus anxius, Spodoptera frugiperda, Leptinotarsa decemlineata, Oulema melanopus, Ips typographus and Halyomorpha halys. We used mean temperature and photoperiod from the Republic of Ireland from 1961 until present. Future climate scenarios were incorporated using projections across three RCP scenarios (RCP 26, 45 & 85) across two future periods : 2021 – 2050 and 2041 – 2070.
Future climate scenarios indicate that more generations will occur; where for instance, Agrilus anxius would increase from three generations to four generations as its season is solely temperature based. Whereas, other such as Leptinotarsa decemlineata that undergo obligative diapause may not have an increase in generations as a decrease in photoperiod serves as a limiting factor for their length of season. While for Halyomorpha halys, no generations would appear despite the warmer conditions.
The goal of this project is to have an open access web application that could then be developed further in the future. This readily could serve as a template for initiatives in other countries. This online tool will provide the decision support to allow actions to be taken in the event of high risk of the modelled pest and can be expanded to if a new pests that may emerge over time in the Republic of Ireland.
How to cite: Brett, P., Hochstrasser, T., Finkele, K., Flattery, P., Coonan, B., Duffy, C., Hemming, D., Kaye, N., McGee, C., and Yearsley, J.: Accounting for overwintering life-histories in an online pest risk assessment tool, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17199, https://doi.org/10.5194/egusphere-egu25-17199, 2025.
Phenological changes are key indicators of climate change. While most studies focus on individual species, plant macrophenology examines large-scale patterns and processes in the timing of plant life cycle events, such as flowering, across extensive spatial and temporal scales. Traditional methods often struggle to capture the complexity of these patterns. To address this, we developed a pioneering methodological approach using nonlinear dimension reduction [1], which effectively extracts spatio-temporal patterns from large and diverse phenological datasets.
Our approach reveals ecological gradients that capture underlying structures and relationships missed by linear methods [1,2]. A primary objective is to quantify synchronised behaviour across thousands of plant species, offering insights into the collective responses of plant communities to climate variability and change. By identifying and analysing synchronisation patterns, we aim to detect shifts in plant phenology and understand their broader ecological impacts
We demonstrate the versatility of our approach by applying it to datasets collected by citizen scientists using mobile applications such as Flora Incognita [3], a plant identification app. Additionally, we explore phenological changes across annual cycles and propose linking these findings to large-scale measurements such as eddy covariance and satellite data.
Incorporating citizen science datasets enhances the resolution and accuracy of our analyses, enabling robust conclusions about the impact of climate variability on plant phenology. This framework advances plant macrophenology, providing researchers with practical tools to quantify and monitor climate change effects on plant life cycles.
[1] Mora et al. (2024) Methods Ecol Evol, http://doi.org/10.1111/2041-210X.14365
[2] Mahecha et al. (2021) Ecography, 44: 1131-1142 https://doi.org/10.1111/ecog.05492
[3] Mäder et al. (2021) Methods Ecol Evol, 12: 1335-1342 https://doi.org/10.1111/2041-210X.13611
How to cite: Mora, K., Rzanny, M., Wäldchen, J., Feilhauer, H., Guimarães-Steinicke, C., Kattenborn, T., Kraemer, G., Mäder, P., Svidzinska, D., Wieneke, S., Wolf, S., and Mahecha, M. D.: Plant macrophenological dynamics - variations in plant group behaviour revealed by citizen science data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16628, https://doi.org/10.5194/egusphere-egu25-16628, 2025.
Plant phenology is a key driver of plant growth and ecosystem-climate interactions, influencing canopy structure, surface albedo, and carbon and water fluxes. While the effects of environmental factors on phenology are well-documented, less attention has been given to intrinsic plant physiological processes. Non-structural carbohydrates (NSC), including sugars and starch, are essential for growth, metabolism, and osmotic regulation, serving as indicators of carbon availability. They reflect the balance between photosynthetic carbon supply (source activity) and the demands of growth and respiration (sink activity), suggesting that NSCs may influence phenological stages such as spring leaf-out and autumn senescence. However, the relationship between NSC dynamics in various plant organs and leaf phenology remains poorly understood.
By synthesizing current knowledge on the interplay between NSCs and leaf phenology, we outline seasonal NSC variations in deciduous and evergreen species. We further propose hypotheses on their interactions with phenological stages, namely leaf-out and autumn leaf senescence, and assess their alignment with existing conceptual carbon allocation models. To address existing gaps, we advocate for integrating NSC dynamics into carbon allocation models by leveraging insights from manipulative experiments, multi-scale observational networks, and remote sensing. These approaches will enable a more comprehensive understanding of NSC-phenology relationships across spatial and temporal scales. This could help us improve the modelling of plant phenology responses and carbon dynamics in diverse ecosystems.
How to cite: Luo, Y., Zohner, C., W. Crowther, T., Hoch, G., D. Richardson, A., Vitasse, Y., and Gessler, A.: Dynamics in non-structural carbohydrates of trees might influence the variation of leaf phenology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8512, https://doi.org/10.5194/egusphere-egu25-8512, 2025.
Advanced bud burst in deciduous trees extends the growing season to an earlier date, increasing their vulnerability to spring frost damage. Such frost events, though understudied in current research, can cause long-term damage by compromising the recovery capacity of trees and adding stress to their carbon and water balance. The resilience of pedunculate oak (Quercus robur L.) to the increasingly dry and warm climate positions them as crucial tree species in the planning of climate-adapted forests. Understanding the balance between drought resilience and frost vulnerability is essential for informed decisions about future forest management strategies. In this study, we used a dense monitoring network of phenological observations to i) highlight a significant increase in spring frost risk in recent years and ii) calibrate two phenological models and apply them to the output of seven coupled RCP8.5 climate projections. The models predict a mean advance in oak bud burst by 2-2.7 days per decade, consistent with a 2 days per decade advance observed historically. Despite the general warming trend, last spring frost events have not preponed to earlier dates in the observations. This is probably linked to stable high-pressure systems in spring with enhanced radiative cooling at the surface during the night. However, the projections fail to accurately capture the last frost, likely linked to a known weakness in blocking events. Consequently, we suggest that future frost risk may be underestimated in current projections.
How to cite: Smekal, B. L., Ahrends, B., Axer, M., Sutmöller, J., and Meesenburg, H.: Shifting Seasons, Rising Risks: Spring Frost Predictions for Pedunculate Oak in Hesse, Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-181, https://doi.org/10.5194/egusphere-egu25-181, 2025.
Climate change is one of the greatest challenges facing the agricultural sector in the 21st century. In recent decades, extreme heat, uncharacteristic for Latvia, prolonged drought, particularly in spring, and extremely heavy rainfall in the second half of summer have significantly impacted the development of cereals. An example is May 2023, which was the driest May in the history of observations in Latvia. The aim of the study was to describe how uncharacteristic weather conditions caused by climate change impact the phenology and yield stability of summer barley (Hordeum vulgare L.) in two distinct locations, Priekuli (climate type—Dfb) and Stende (climate type—Cfb), from 2000 to 2023. Spring barley in Latvia is usually sown in late April or early May. The analysis of the data revealed a moderately close relationship between the average air temperature in April and the barley sowing time in both Priekuli and Stende. For the most part, in years when the average air temperature in April has been higher, sowing has begun earlier. Early varieties typically require a minimum of 90 days from sowing to full maturity, whereas late varieties usually need an average of 100 to 110 days. However, in certain years, both early and late varieties have experienced a significantly shorter growing season. Years where the average air temperature during the growing season exceeds the norm typically witness a shorter growing season. This was the case, for example, in 2010, 2018, and 2021, when none of the varieties in Priekuli exceeded 89 days between sowing and full maturity. The data from the study show that if the transition from the vegetative growth phases to the generative growth phases occurred very rapidly, the plants had a low tillering rate, there were few productive stems, and the plants were short; hence, the yields were also low. For instance, in 2021, the variety ‘Ansis’ in Priekuli yielded 2.72 t ha-1, approximately twice as low as in years when the weather was optimal for development. If drought and heat accelerate the development of cereals, then frequent precipitation and lower air temperature during the ripening period hinder the onset of full ripeness. Observing adverse weather conditions, such as heavy rainfall, during the full ripeness stage delays harvesting and deteriorates crop quality, as demonstrated in 2017. Based on the results obtained, it is possible to select varieties and breeding lines that, regardless of the influence of weather conditions on the length of the growing season, maintain relatively high yield stability and good yield quality. An analysis of the 24-year data series shows that the increasingly frequent uncharacteristic weather conditions affect the phenology of spring barley. Furthermore, the study results do not show regional differences, as the impact of extreme weather conditions is similar at both observation locations.
How to cite: Dzedule, L., Kalvane, G., and Legzdina, L.: Impact of uncharacteristic weather conditions on the phenology and yield stability of spring barley (Hordeum vulgare L.) in Latvia: a 24-year study (2000–2023), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2233, https://doi.org/10.5194/egusphere-egu25-2233, 2025.
Vegetation spring phenology in arid mountain regions is undergoing profound changes as a result of recent climate anomalies. While shifts in the timing of growth onset have been widely attributed to temperature and precipitation, interacting effects of these two climate variables on phenology have not been explored. To better understand whether an interaction between temperature and precipitation may be present, and how it may affect phenology, we first determined the influence of preseason temperature and precipitation on the starting date of vegetation growing season (SOS), and then investigated the spatial pattern of climatic sensitivity of SOS and its relation to preseason temperature/precipitation. We used satellite-derived estimates of SOS for the Qilian Mountains (QLMs) in northwestern China. Our results revealed a significant interaction between temperature and precipitation, contributing up to 30% of total variability in predicted ecosystem-level SOS. This interacting effect was likely achieved through the influence on climatic sensitivity of SOS; we found a close relationship between temperature sensitivity and preseason cumulative precipitation, and a significant association between precipitation sensitivity and preseason temperatures. Spatially, SOS was more sensitive to variability in preseason temperature in wetter than in dryer areas; likewise, a spatial increase in thermal accumulation often corresponded to an enhancement in precipitation sensitivity of SOS. These findings highlight the importance of interacting effects of climatic variables in model projections of future spring phenology, and indicate that unexpected shifts in vegetation phenology in response to climatic extremes may occur under the influence of strong interactions of climatic factors.
How to cite: He, Z.: Interacting effects of temperature and precipitation on climatic sensitivity ofspring vegetation green-up in arid mountains of China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14181, https://doi.org/10.5194/egusphere-egu25-14181, 2025.
Phenology, encompassing the timing of the start, end, and duration of the growing season, is influenced by climate warming in northern regions. Altered phenological patterns carry significant implications for the global carbon cycle by disrupting the seasonal balance between gross primary productivity (GPP) and ecosystem respiration and complicating vegetation reproductive cycles. However, many current Earth system models, including those used in the “Trends and drivers of the regional scale terrestrial sources and sinks of carbon dioxide” (TRENDY) project, may inadequately capture recent phenological trends in northern ecosystems (Sitch et al., 2024). In this study, we aim to present a comprehensive analysis of phenology patterns across northern latitudes (>45°N) over the past two decades, using outputs from twelve state-of-the-art vegetation models included in the TRENDY project. These outputs, along with the TRENDY model ensemble average, are intercompared with a remote sensing-based phenology dataset derived using the Plant Phenology Index (PPI) and MODIS data. Compared with the in-situ measurements, the PPI has demonstrated improved accuracy in capturing northern phenology, particularly for boreal evergreen forests, by reducing the confounding effects of snowmelt and soil background signals (Jin et al., 2017). Furthermore, the PPI has proven effective in estimating large-scale GPP across diverse northern ecosystems, providing a robust benchmark for evaluating the performance of vegetation models (Marsh et al., 2024). We further examine the primary climatic drivers of phenological shifts (air temperature, precipitation and radiation) and assess the extent to which TRENDY models capture these drivers and the associated phenological responses to climate warming. Our findings highlight the current gap between model projections and observed phenology, offering insights into the limitations of current carbon cycle models in representing northern ecosystem dynamics. Our study contributes to advancing our understanding of the roles of northern ecosystems in the global carbon cycle.
References
Jin, H., Jönsson, A. M., Bolmgren, K., Langvall, O., & Eklundh, L. (2017). Disentangling remotely-sensed plant phenology and snow seasonality at northern Europe using MODIS and the plant phenology index. Remote Sensing of Environment, 198, 203-212.
Marsh, H., Jin, H., Duan, Z., Holst, J., Eklundh, L., & Zhang, W. (2025). Plant Phenology Index leveraging over conventional vegetation indices to establish a new remote sensing benchmark of GPP for northern ecosystems. International Journal of Applied Earth Observation and Geoinformation, 136, 104289.
Sitch, S., O’sullivan, M., Robertson, E., Friedlingstein, P., Albergel, C., Anthoni, P., ... & Zaehle, S. (2024). Trends and drivers of terrestrial sources and sinks of carbon dioxide: An overview of the TRENDY project. Global Biogeochemical Cycles, 38(7), e2024GB008102.
How to cite: Marsh, H., Jin, H., Duan, Z., and Zhang, W.: Northern Phenology Under Climate Warming: Evaluating TRENDY Models Against Remote Sensing Data with the Plant Phenology Index, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16191, https://doi.org/10.5194/egusphere-egu25-16191, 2025.
Cold temperatures (known as ‘chilling’) are perceived by tree buds in winter and are responsible for dormancy release after species-specific exposure times, which marks the start of the buds' sensitivity to warmer temperatures (known as ‘forcing’). Temperate trees are also sensitive to changing daylength, but it remains unresolved whether the accumulation of chilling and forcing is related to the diurnal cycle. This study explores whether trees "count" chilling based on night/day cycles rather than purely through temperature accumulation or exposition, and whether forcing temperatures are more effective during daylight.
We harvested twigs from four temperate tree species with contrasting chilling and forcing requirements for dormancy release in late November 2024 , i.e. before they would experience significant periods of cold. Twig cuttings were then placed into transparent boxes filled with water and kept in climate chambers at 2°C/4°C (night/day) under three diurnal cycles: 12h/12h, 6h/6h (2 cycles per day), and 4h/4h (3 cycles per day) for one month (short chilling) or two months (long chilling). After these six treatments, all cuttings were transferred to forcing conditions with 12h daylight under two temperature regimes: 10°C/25°C and 15°C/20°C, i.e. with the same mean temperature but warmer or colder temperature during daytime. The timing and success of bud break were visually monitored twice a week.The experiment is ongoing. We hypothesize that chilling accumulation is influenced by diurnal cycles, with faster dormancy release for twigs exposed to shorter diurnal cycles. Additionally, we anticipate that daytime temperatures play a more significant role in forcing accumulation, leading to faster budburst in the 10°C/25°C treatment compared to the 15°C/20°C, especially for species known to be photoperiodic sensitive such as European beech.
Our study will provide insights into how trees perceive and respond to temperature in relation to daylight, which is crucial for understanding and predicting phenological responses accurately in the context of climate change.
How to cite: Vitasse, Y., Hoch, G., Pepin, S., and Giardina, F.: Exploring the control of diurnal cycles on chilling and forcing accumulation in tree bud dormancy release, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5103, https://doi.org/10.5194/egusphere-egu25-5103, 2025.
Phenology—the study of the timing of seasonal activities of animals and plants—provides a vital window into ecological responses to climate change (IPCC 2007). Since its inception 15 years ago, PEP725, the Pan-European Phenological Database, has developed into an essential resource for phenological research across Europe.
With support from ZAMG / now Geosphere Austria, the Austrian Ministry of Education, Science and Research, and EUMETNET, PEP725 has built an open-access database that now boasts over 13 million phenological records across many countries of Europe - all classified with a single scale. These records, which trace back to 1775, offer a unified and comprehensive view of phenological observations across Europe. The project continues to overcome challenges posed by disparate data sources and formats, enabling harmonized, large-scale studies and fostering international collaboration.
Throughout its evolution, PEP725 has faced and overcome many challenges, from the integration of different datasets to the creation of a focal point and collaboration platform for European phenological research. PEP725 enables large-scale studies and fostering international cooperation. Since its’s beginning user engagement has steadily increased, with registrations and data downloads reaching new highs, and the database has supported an impressive number of peer-reviewed publications, demonstrating its scientific impact.
In this presentation, we will present the current status of PEP725, including milestones achieved, lessons learnt and challenges encountered along the way. Moreover, we want to express our gratitude to all our indispensable project partners who have accompanied us along the way. We are also pleased to provide an insight into the development of our new website, which aims to improve usability and widen access to this invaluable resource.
How to cite: Ressl, H., Ungersböck, M., and Hübner, T.: PEP725: Celebrating 15 Years of this Phenological Research Infrastructure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7960, https://doi.org/10.5194/egusphere-egu25-7960, 2025.
The Meteorological Service of Catalonia (SMC) publishes regularly the Annual Bulletin of Climate Indicators with the aim to communicate the state of the climate in Catalonia based on the climate series, the series of sea temperature and sea level, and the phenological series, all of them managed by this institution.
The Annual Bulletin of Climate Indicators (known by the acronym 'BAIC' according to its name in Catalan) has eight chapters: air temperature (data from 27 climate series), precipitation (data from 72 climate series), extreme climate indices (based on Expert Team on Climate Change Detection and Indices standards), synoptic patterns (surface and 500 hPa), phenology (information from the Phenological Network of Catalonia), insolation (data from 8 series), secular observatories (information from specific observatories in Catalonia with more than 100 years of daily data) and sea (one series of sea temperature at different depths, mean sea level and sea storms), apart from the introduction, the executive summary (key points of the bulletin) and the references.
The SMC created the Phenological Network of Catalonia (Fenocat) in 2013, a citizen science network where 79 observers monitor 25 plant species, 14 bird species and 6 butterflies. 37 of these observers have registered information from the very beginning of the Fenocat, and the results shown are based mostly on their information.
The phenology chapter of the Annual Bulletin of Climate Information describes the state of the phenological network, explains the most characteristic features of the phenological situation during the last year and shows the evolution of the onset of the main phenophases from 2013 to the present, as well as the intra-annual variability. Tables are also provided with the value of the trend and its statistical significance.
The main results of the latest BAIC will be shown, providing examples of graphics, charts and tables used to convey these results to the society, with the main goal of reporting the state of the climate to the society in the clearest and most rigorous way possible.
How to cite: Busto, M., Cunillera, J., de Yzaguirre, X., Prohom, M., Barrera-Escoda, A., and Herrero, M.: The phenological information in the Annual Bulletin of Climate Information of the Meteorological Service of Catalonia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8123, https://doi.org/10.5194/egusphere-egu25-8123, 2025.
Seasonal cycles of vegetation functioning are changing as a consequence of climate change. For example, a widespread greening of the northern hemisphere is observed, with an earlier start of the growing season and a later end of the growing season in some regions. However, in other regions, the growing season is actually ending earlier due to water limitations or more frequent extremes.
In this study, we focus on Europe and calculate seasonal cycles of vegetation indices at each grid cell during a past time period, and determine where most similar seasonal cycles are observed during a more recent time period. This way, we examine how the seasonal vegetation cycle at grid cells has shifted in space over the past decades by analyzing satellite-derived Leaf Area Index (LAI) data. The spatial shift is calculated for each grid cell as the difference between the locations with (i) most similar seasonal cycles during 2010-2018 and (ii) most similar seasonal cycles during 1982-1989. Similarity is assessed based on the RMSE between the seasonal cycles. First results show a widespread eastward and northward shift of seasonal cycles across Europe. The variability of determined shifts is high across regions. Calculations of spatial shifts using MODIS LAI data during more recent time periods are used to validate the long-term results. Finally, we compare the determined spatial shifts to respective trends in hydro-meteorological conditions.
Our detection of large-scale shifts in seasonal vegetation cycles can help to better understand vegetation response and adaptation to global change, and thereby improve the prediction of future shifts.
How to cite: Brügelmann, J., Kroll, J., and Orth, R.: Spatial shifts of seasonal vegetation cycles in Europe over time, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11953, https://doi.org/10.5194/egusphere-egu25-11953, 2025.
Crop phenology is very important in regular crop monitoring. Generally, phenology is monitored through field observation surveys or satellite data. The relationships between ground observations and remotely sensed derived phenological data can enable near-real-time monitoring over large areas, which has never been attempted on hazelnuts. In this study, we extracted phenological metrics derived from MODIS Enhanced Vegetation Index (EVI) in hazelnut production regions and compared them with the spring ground phenological data (BBCH scale) from orchards located in the same area of Turkey over the period from 2019 to 2022. We observed a specific temporal dynamic between remote sensing phenometrics and ground observations. The metrics Greenup, Upturning Date, and Threshold 20% metrics corresponded to the early of EVI growth and were synchronous with the female flowering of hazelnut and ending before bud break. The metrics Threshold 50% and Start of season were associated with the steepest portion of the EVI curve, i.e., canopy greening and thickening, and occurred between ovaries enlargement and leaves unfolding. The metrics Peak of Season, Stabilization Date, and Maturity corresponded to the end of spring vegetative growth. The main outcomes are that (i) female flowering occurred before 20% of vegetation development (BBCH 64P occurred about one month before Threshold 20%), (ii) phenometrics from satellite remote sensing (i.e., Upturning Date and Threshold 20%) well-reflected leaf emergence (rs = 0.30 and rs = 0.32, respectively; p < 0.05) and unfolding (rs = 0.35 and rs = 0.39, respectively; p < 0.05), and (iii) cluster appearance temporally aligned with the peak of the EVI curve (Stabilization Date and BBCH 71P differed by around 4 days). Our method is transferable to operational phenology monitoring, and future applications will consider the senescence season and the effect of environmental variability on the comprehension of vegetation dynamics.
How to cite: Di Giulio, M., Bajocco, S., Abdullah, M. S., and Bregaglio, S.: Exploring the relationships between ground observations and remotely sensed hazelnut spring phenology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18180, https://doi.org/10.5194/egusphere-egu25-18180, 2025.
Climate change has caused asynchronous phenological shifts between most plants and their pollinators, resulting in an earlier or later appearance of peak flowering relative to peak pollinator abundance. The fitness impact of these two mismatch patterns may not be simply equivalent, but the information has so far been limited. To explore how differently plant fitness responds to the distinct mismatch patterns, we conducted a seed-setting comparative study at the individual level in an alpine grassland community in the Qilian Mountains of China. By monitoring flowering abundance and insect visits, we measured the phenological matching relationship between plants and their key pollinators, and evaluated the impact of mismatches on plant productivity. We found that the pattern of “pollinator peaks earlier” accounted for a relatively high proportion in the natural community, with a significantly stronger fitness impact on plants than that of the “flower peaks earlier” pattern. The asymmetry in the fitness impacts between phenological mismatch patterns is related to the length of flowering period. Specially, the shorter the flowering duration, the greater the difference in influence between the two patterns. Our results suggest that plants with shorter flowering periods may be confronted with more severe pollination limitations if climate warming cause insects to forage further ahead. Therefore, the asymmetric effects of phenological mismatch patterns should be considered in phenological models to improve the predictive performance of plant responses to climate change.
How to cite: Du, J.: Pollinator peaking earlier than flowering is more detrimental to plant fecundity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14304, https://doi.org/10.5194/egusphere-egu25-14304, 2025.
Climate change affects the spatial distribution and abundance of yellowfin tuna (Thunnus albacares, YFT) in the tropical Pacific, yet the mechanisms linking remote climate modes to YFT dynamics remain unclear. This study finds that the variability of autumn tropical Pacific YFT is tied to the spring sea surface temperature anomalies (SSTAs) of the North Atlantic Tripole (NAT), mediated by the Victoria Mode (VM), the second dominant mode of North Pacific SSTAs variability. The result shows that the spring NAT is significantly positive correlated with the subsequent autumn tropical Pacific YFT catch per unit effort (CPUE). The spring NAT triggers eastward-propagating Rossby waves, inducing VM-like SST anomalies (SSTAs) in the North Pacific. These anomalies modify YFT habitat conditions in the tropical Pacific through coupled oceanic-atmospheric bridge (COAB) mechanism, ultimately affecting autumn CPUE. This study unveils a teleconnection-driven mechanism influencing tropical Pacific YFT CPUE, with important implications for fisheries management and forecasting.
How to cite: Zhang, G. and Li, J.: Variability of autumn tropical Pacific yellowfin tuna tied to the spring North Atlantic Tripole , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4238, https://doi.org/10.5194/egusphere-egu25-4238, 2025.
Saxicolous lecideoid lichens form a major part of the existing terrestrial vegetation in Antarctica. Lichens are formed by an association between a fungal (mycobiont) and a photosynthesizing (photobiont) symbiont. Adapted to extreme habitats, their distribution is primarily determined by macroclimatic conditions, with climate change presenting a significant challenge to these specialized organisms. In our study we assessed the current climatic niches of 9 circumantarctic mycobiont species and their associated photobiont OTUs and predicted the niche shifts of this species under two contrasting climate forcing scenarios (RCP2.6 and RCP8.5).
Our findings do not indicate a distinct climatic differentiation between the current niches of the symbiont pairs. However, the changes in potential niche areas suggest a general trend of niche expansion for all species under both climate scenarios (RCP2.6 andRCP8.5). For each species, the projected area gain is predicted to exceed the corresponding area losses due to climate warming. The niche expansion is primarily driven by the shift of niches inland, as new areas become suitable. While newly exposed rock surface due to snowmelt may contribute to the niche expansion for specific species on the Antarctic Peninsula, the overall impact on the continental Antarctic is insignificant. Our analysis indicates a general increase of niche overlap between species across all regions, except in the maritime Antarctic, where the complete loss of species niches was predicted. A broader pattern emerges in which regions with higher probable species richness are expected to shift inland, while coastal areas are likely to experience a decline in species numbers.
How to cite: Götz, A., Andreev, M., Maislinger, L., Sancho, L., Trutschnig, W., and Ruprecht, U.: Predicting Climatic Niche Shifts and Future Range Dynamics of Antarctic Rock-Dwelling Lichens Under Climate Change Scenarios, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16936, https://doi.org/10.5194/egusphere-egu25-16936, 2025.
