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Increase in the risk of exposure of forest and fruit trees to spring frosts at higher elevations in Switzerland over the last four decades
Abstract
Winters and early springs are predicted to become warmer in temperate climates under continued global warming, which in turn is expected to promote earlier plant development. By contrast, there is no consensus about the changes in the occurrence and severity of late spring frosts. If the frequency and severity of late spring frosts remain unchanged in the future or change less than spring phenology of plants does, vulnerable plant organs (dehardened buds, young leaves, flowers or young fruits) may be more exposed to frost damage. Here we analyzed long-term temperature data from the period 1975–2016 in 50 locations in Switzerland and used different phenological models calibrated with long-term series of the flowering and leaf-out timing of two fruit trees (apple and cherry) and two forest trees (Norway spruce and European beech) to test whether the risk of frost damage has increased during this period. Overall, despite the substantial increase in temperature during the study period, the risk of frost damage was not reduced because spring phenology has advanced at a faster rate than the date of the last spring frost. In contrast, we found that the risk of frost exposure and subsequent potential damage has increased for all four species at the vast majority of stations located at elevations higher than 800 m while remaining unchanged at lower elevations. The different trends between lower and higher elevations are due to the date of the last spring frost moving less at higher altitudes than at lower altitudes, combined with stronger phenological shifts at higher elevations. This latter trend likely results from a stronger warming during late compared to earlier spring and from the increasing role of other limiting factors at lower elevations (chilling and photoperiod). Our results suggest that frost risk needs to be considered carefully when promoting the introduction of new varieties of fruit trees or exotic forest tree species adapted to warmer and drier climates or when considering new plantations at higher elevations.
... Vegetation vulnerability may be affected not only by CDH, but also by other types of CCEs (Richardson et al. 2018;Vitasse et al. 2018;Li et al. 2022). Cold-and wetrelated extreme events can exacerbate vegetation loss by causing the leaf frostbite, inhibiting the root respiration, shortening the growing season, and reducing the photosynthetic carbon uptake (Richardson et al. 2018;Vitasse et al. 2018;Chen et al. 2023b). ...
... Vegetation vulnerability may be affected not only by CDH, but also by other types of CCEs (Richardson et al. 2018;Vitasse et al. 2018;Li et al. 2022). Cold-and wetrelated extreme events can exacerbate vegetation loss by causing the leaf frostbite, inhibiting the root respiration, shortening the growing season, and reducing the photosynthetic carbon uptake (Richardson et al. 2018;Vitasse et al. 2018;Chen et al. 2023b). Li et al. (2022 argued that CDC events impose an adverse impact on productivity at midto high-latitudes, surpassing the impacts of individual cold or dry events. ...
... The lag effect may vary depending on the type and intensity of climate events and vegetation types, and its dynamic characteristics are crucial for understanding the mechanisms of vegetation vulnerability. Second, although cold-and wet-related CCEs may inhibit vegetation growth and disrupt ecosystem functions (Richardson et al. 2018;Vitasse et al. 2018;Chen et al. 2023b;Li et al. 2022), little is known about the response characteristics of different vegetation types to these events. In addition, the nonlinear interactions between CCEs and vegetation responses have yet to be thoroughly explored. ...
In the context of climate warming, compound dry-hot (CDH), dry-cold (CDC), wet-hot (CWH), and wet-cold (CWC) events have become increasingly frequent and widespread in recent decades, causing severe but disproportionate impacts on terrestrial vegetation. However, the understanding of how vegetation vulnerability responds to these compound climate events (CCEs) is still limited. Here, we developed a multivariate copula conditional probabilistic model integrating the Standardized Precipitation Index (SPI), Standardized Temperature Index (STI), and Normalized Difference Vegetation Index (NDVI) together to quantify the vegetation response to each of CDH, CDC, CWH and CWC events under diverse climates in mainland China. Results show that CDC has a greater likelihood of causing vegetation loss relative to other CCEs, with the probability of NDVI ≤ 40th being 4.8–13.0% (0.5–2.6%) higher than individual dry (cold) events, while CWH causes the lowest vegetation loss probability, with the probability of NDVI ≤ 40th being 5.6–6.9% (4.2–5%) lower than individual wet (hot) events. Vegetation in arid and semi-arid regions is highly susceptible to CDC and CDH events, while that in northeastern China and southern humid regions is more vulnerable to CWC and CWH events. Among vegetation types, Shrubland, grassland and cropland exhibit higher vulnerability to CDC and CDH events, while deciduous (evergreen) forests are more vulnerable to CWC (CWH) events, which may be related to vegetation physiological characteristics, survival strategies, and climatic adaptations. This study enhances the understanding of the response of various vegetation types to different CCEs and highlights the necessity of simultaneously considering vegetation types and regional climate conditions when formulating adaptive vegetation management strategies.
... (EWE), many of which are projected to increase with global warming (Easterling et al. 2000;Allan and Soden 2008;Jentsch and Beierkuhnlein 2008). The early growth of many plant invaders (Polgar and Primack 2011;Wolkovich and Cleland 2011;Wolkovich et al. 2013;Polgar et al. 2014) may make them particularly sensitive to EWEs that occur early in the growing season, as they may be more susceptible to extreme temperatures and/ or water availability during the early stages of growth (Laube et al. 2015;Vitasse et al. 2018) in comparison to later growing native species. Some of the common effects of climate change on invasive plants that have already been reported, including an advancement of leaf-out in spring and shifts in flowering patterns (Polgar and Primack 2011;Wolkovich and Cleland 2011;Wolkovich et al. 2013;Polgar et al. 2014), as well as an extended leaf phenology and delayed abscission in autumn (Fridley 2012;Gallinat et al. 2015), could make them more susceptible to the effects of early or late occurring EWEs. ...
... In terms of the occurrence of extreme low temperature events, climate change-related advancement of the growing season could pose significant risks for plants that initiate growth earlier (Bradley et al. 2010;Laube et al. 2015). Since the date of first spring frost may not change significantly (Vitasse et al. 2018), growing earlier brings the risk of low temperature-related impairment of growth and reproduction. Given that the growth period is strongly controlled by regional climate history, native species may display more conservative traits that have made them more resistant to EWEs and/or allowed them to evade most of their effects through adaptation to a shorter growing season (Zohner and Renner 2017). ...
... Whilst we cannot separate the effects of early growth from a greater resilience to episodic low temperature events, by starting growth later, native species may avoid the impacts of an EWE that occurs early in the year (Zohner and Renner 2017), which could partially explain why J. effusus was not impacted by Storm Emma. Thus, growing earlier may not always represent a benefit given the risks associated with exposure to spring frosts (Laube et al. 2015;Vitasse et al. 2018), highlighting that climate change-related extension in the growing period will not always benefit invasive plants as often suggested (Polgar and Primack 2011;Wolkovich and Cleland 2011;Fridley 2012;Wolkovich et al. 2013;Groeneveld et al. 2014;Polgar et al. 2014;Gallinat et al. 2015;Ratcliffe et al. 2024). ...
Whilst it is often assumed that invasive plant species may benefit more from climate change than native species, there is little empirical data on how they, and the communities they invade, respond to extreme weather events (EWEs). Here, we show that the effects of a low temperature EWE can result in a dramatic reduction in both vegetative and reproductive growth of invasive populations of Gunnera tinctoria , although a significant recovery was found within 1 year after its occurrence. Whilst the EWE decreased both the leaf/petiole numbers of mature plants, the major impact was on leaf expansion and a decrease in the size/number of inflorescences. Concomitant with the reduction in growth of G. tinctoria , there was a 5‐fold increase in the number of resident species emerging in invaded areas, which largely persisted after the recovery of the invasive populations. Although the growth of G. tinctoria seedlings was also reduced, this was relatively small, and growth and development resumed almost immediately after the EWE. In comparison, the resident plant community was largely unaffected by the EWE either due to the later initiation of growth and/or because of their greater resilience to episodic low temperature events. Our results show that an EWE of this magnitude can have complex time‐dependent effects on plant invasions and invaded communities, with a greater impact on the established invasive plants compared to newly recruited seedlings. Based on an assessment of historical climatic data, these long‐lived populations have been exposed to EWEs of a similar or greater magnitude in the past, which have not constrained their spread or compromised recruitment. Given the likelihood of an almost complete absence of low temperature EWEs of similar magnitude in the future, any temporary restrictions on the growth of invasive G. tinctoria and other similar invasive species populations are likely to be small.
... Therefore, the impacts of climate change on spring phenophases and spring frost risk of apple trees were region-specific (Ru et al., 2023). Moreover, while the elevated minimum temperatures could potentially mitigate spring frost risk, the advancement in the first flower opening time of apples is likely to counteract this effect (Cho et al., 2021;Darbyshire et al., 2012;Drepper et al., 2022b;Eccel et al., 2009;Guo et al., 2019;Hoffmann and Rath, 2013;Lamichhane, 2021;Unterberger et al., 2018;Vitasse et al., 2018;Yang et al., 2021). Despite these dynamics, there remains a dearth of studies evaluating the consequences of spring frost on apple yield loss under anticipated future climate change scenarios (Chen et al., 2023;Li et al., 2020;Miranda et al., 2021;Sousa et al., 2022;Stöckle et al., 2010;Zhu et al., 2021;. ...
... For the first time, we used a process-based crop model STICS to evaluate the impacts of climate change on apple phenology and yield across the China's apple planting regions. Advancement in spring phenology was projected in most apple planting regions especially in northern China due to rising spring temperature, which was reported all over the world (Lamichhane, 2021;Sun et al., 2022;Unterberger et al., 2018;Vitasse et al., 2018). In the warmer climate regions of China, such as the southern region IV, and the majority of the region III, spring phenophases would be delayed due to insufficient chill accumulation of apples caused by rising winter and spring temperatures (Fig. S7). ...
... In general, apple yield losses due to spring frost were projected to increase in the future in most of China's apple planting regions, particularly in regions I, II, and V (Fig. 4). This was because apple flowering was projected to occur earlier than spring frost events in the future (Lamichhane, 2021;Unterberger et al., 2018;Vitasse et al., 2018;Yang et al., 2021). Therefore, we further tested the potential of delaying first flower opening time to mitigate the adverse effects of frost risk on apple yields. ...
Apple is one of the globally significant perennial fruits, with high consumption driven by the demand for nutritional food diversity and population growth. There is a lack of understanding with respect to the potential consequences of climate change, particularly the impact of spring frost-a frequent agrometeorological disaster on apple yield. Here we used a process-based apple model driven by five climate models to evaluate climate change impacts and the potential adaptation potential in China's apple planting region under climate change. Our study used the process-based STICS model developed by INRAE, France, driven by five global climate models (GCMs; FGOALS-g3, GFDL-ESM4, MPI-ESM1-2-HR, MRI-ESM2-0, and UKESM1-0-LL) to evaluate the impacts of climate change including spring frost on apple yield in China's apple planting region and explore the possible adaptation strategy by increasing thermal time required to complete the phase from budbreak to first flower opening with increments of 10%, 30%, 50%, 70%, and 90% in the STICS model at frost-sensitive sites under two emission scenarios (SSP245 and SSP585) during two periods of 2050s (2040-2069) and 2080s (2070-2099). We found the robust performance of the STICS model in simulating phenology and yield of apple across China's apple planting regions. While climate change exerts a slightly positive impact on apple yields with large spatial variation in the staple apple production regions, intensified spring frost under climate change would aggravate apple yield loss. We found that delaying flowering time can increase yield by up to 10% at the frost-sensitive sites. Our results highlight the importance of effective adaptation options to reduce frost-induced apple yield loss under climate change in China's apple planting region.
... This argument has mainly been supported via modeling with past data and via predictions according to the monitored changes. However, it has also been argued that climate warming has increased frost risks for forest plants due to the advanced phenology and aggravated impairment of organs during dehardening [3][4][5]. This risk has been predicted to exist with continuous warming at an expected probability as high as 20% in a thoroughly projected period that runs up to 2090 [6]. ...
... At the same time, in the first sampling, all of the seedlings had experienced a growing season of about six months, and this was recognized as a sufficient time for new leaves to grow. Fresh new leaves were sampled since they were especially vulnerable to frost shocks [4,27]. At each sampling, ten fresh leaves were collected from the twigs and branches that were fully exposed to sunlight. ...
... ANOVA, analysis of variance; 2 Chla, chlorophyll-a content; 3 F and P values represent ANOVA significance;4 bold values indicate significant results; 5 Chlb, chlorophyll-b content; 6 MDA, level of malondialdehyde; 7 POD, peroxidase activity; 8 EC, electrical conductance. ...
Valuable trees are frequently taken from their original habitat and introduced to a different location in the pursuit of better economic development. Global climate change imposes a higher probability of warm spells during chilly seasons; these may increase the threat posed by frost to newly introduced, valuable species. In this study, Dalbergia odorifera was cultured as a valuable tree species that was introduced from an original provenance in Sanya (1° N) to the northern mountains in Pingxiang (22° N), Guangzhou (23° N), Zhangpu (24° N), Xianyou (25° N), and up to the northernmost limit in Wenzhou (28° N). Seedlings of these six provenances were tested in a field study conducted in Wenzhou (control) to examine their resistance to local frost stress and to detect the driving forces related to meteorological factors in the winter–spring period of 2015–2016. The leaves sampled over seven days exhibited the typical characteristics of frost impairment. The daily maximum temperature delivered warm spells, increasing by ~7 °C. The daily minimum temperature (−4.3 to −2.0 °C) did not reach freezing point until the early spring of 2016. The controlled seedlings showed lower malondialdehyde content than those from the southern locations, and no mortality occurred. Invisible frost stress was caused by low nitrogen utilization during the earlier stages during warm spells, as well as damage to membrane integrity during the later stage when the minimum temperature suddenly declined. A warm spell was found to impose a negative driving force five days before a sudden chill, which led to frost having an impact on superoxide accumulation and electrical leakage. We conclude that the D. odorifera seedlings that dwell effectively in Wenzhou obtained stronger resistance to local frost stress than those from the southern locations. Low cell membrane integrity and high electrical leakage in leaf cells accounted for the frost damage.
... In May, the average diurnal range varied across different cultivation regions, as detailed in Table 3. While reports on frost injury to fruits due to early leafing and blooming prompted by mild winter temperatures are prevalent [24,25], studies on the risk of spring frosts are scarce [26]. Crop frost hardiness decreases progressively after dormancy [27,28], varying with the growth stage of the flower buds and weakening notably just before blooming [29,30]. ...
... Weather analysis over the past 12 years compared to long-term average norms indicates increased weather variability [33], including unusual weather events and region-based differences [21]. This variability, differing from typical patterns, is expected to heighten concerns about potential frost injury due to unpredictable meteorological phenomena in the future [26]. ...
Recent meteorological variability in winter and spring complicates predicting and managing frost damage in apples and pears. This study investigated the relationship between frost injury during the flowering stages of apples (‘Hongro’ and ‘Fuji’) and pears (‘Wonwhang’ and ‘Niitaka’) and weather conditions across regions at varying altitudes. Orchards were categorized into coastal, inland, mid-mountainous, and mountainous regions, and flowering stages and frost injury were analyzed. The flowering period of apples, from the onset of blooming to full bloom, averaged approximately 15 days, which was about 3 to 5 times longer than that of pears. Furthermore, the total flowering duration of apples was 1.5 to 2.0 times longer than that of pears. Additionally, flowering exhibited a tendency to be delayed at higher altitudes. However, orchards situated in mid-mountainous regions experienced earlier flowering compared to those in other regions. Among the two apple cultivars, the average frost damage was more severe in central flowers than in lateral flowers and was relatively higher in ‘Fuji’ than in ‘Hongro’. In pears, frost damage was most prevalent in the first to fourth flowers within the inflorescence, with ‘Wonhwang’ exhibiting relatively greater susceptibility than ‘Niitaka’. Across different cultivation regions, severe frost damage was observed in orchards located in mid-mountainous areas for both fruit species and cultivars. The severity of frost damage followed the order mid-mountainous, mountainous, plain, and coastal regions. Minimum temperatures were lowest in mid-mountainous and mountainous regions, while daily temperature differences were largest in mid-mountainous regions. Meteorological analysis (1981 to 2022) revealed consistent trends, with an increase in daily temperature range in recent years. These findings highlight the vulnerability of mid-mountainous orchards due to flowering stages overlapping with coastal and plain regions, exposing them to lower temperatures and larger temperature differences. Further studies on temperature variability are essential to mitigate frost damage risks.
... At higher altitudes (500-750 m asl), the phenological trends were almost the same for winter wheat and shrubs and herbs, so the wild species also showed the same phenological speed as the crop plants. Very similar outputs were also recorded for forest trees and fruit trees in Switzerland, where a stronger phenological shift occurred at higher elevations (predicted mean across species and all 50 stations: −3.9 days per decade) than at lower elevations (− 2.2 days per decade) (Vitasse et al. 2018). The difference between lower and higher elevations could be explained by the different temperature trends-stronger warming during late rather than early spring (Vitasse et al. 2018)-which was not proven according to our data (the temperature trends were not different at lower, middle or higher elevations). ...
... Very similar outputs were also recorded for forest trees and fruit trees in Switzerland, where a stronger phenological shift occurred at higher elevations (predicted mean across species and all 50 stations: −3.9 days per decade) than at lower elevations (− 2.2 days per decade) (Vitasse et al. 2018). The difference between lower and higher elevations could be explained by the different temperature trends-stronger warming during late rather than early spring (Vitasse et al. 2018)-which was not proven according to our data (the temperature trends were not different at lower, middle or higher elevations). The reason for the smaller phenological trends (in wild plants) at lower and middle elevations could be that phenophases occur early in the spring, which indicates that they could be limited by late frosts or photoperiods that decelerate the onset of phenophases. ...
Phenological shifts in wild-growing plants and wild animal phenophases are well documented at many European sites. Less is known about phenological shifts in agricultural plants and how wild ecosystem phenology interacts with crop phenology. Here, we present long-term phenological observations (1961–2021) from the Czech Republic for wild plants and agricultural crops and how the timing of phenophases differs from each other. The phenology of wild-growing plants was observed at various experimental sites with no agriculture or forestry management within the Czech Hydrometeorological Institute observations. The phenological data of the crops were collected from small experimental plots at the Central Institute for Supervising and Testing in Agriculture. The data clearly show a tendency to shift to earlier times during the observation period. The data also show some asynchrony in phenological shifts. Compared with wild plants, agricultural crops showed more expressive shifts to the start of the season. Phenological trends for crop plants ( Triticum aestivum ) showed accelerated shifts of 4.1 and 5.1 days per decade at low and middle altitudes, respectively; on the other hand, the average phenological shift for wild plants showed smaller shifts of 2.7 and 2.9 days per decade at low and middle altitudes, respectively. The phenophase ´heading´ of T. aestivum showed the highest correlation with maximum temperatures ( r = 0.9), followed by wild species (with r = 0.7–0.8) and two remaining phenophases of T. aestivum jointing and ripening (with r = 0.7 and 0.6). To better understand the impacts of climate on phenological changes, it is optimal to evaluate natural and unaffected plant responses in wild species since the phenology of field crops is most probably influenced not only by climate but also by agricultural management.
... Ce changement climatique observable depuis le milieu des années 1980 (Schultz, 2000 ;Hansen et al., 2010 ;Jones et al., 2012 ;Reid et al., 2016) n'exclut pas l'existence d'épisodes froids marqués en hiver et plus en avant dans la saison. Ainsi, au printemps, les plantes sont confrontées à un double effet antagoniste : d'une part, une évolution des températures favorable (moins de froid) et, d'autre part, des risques d'être touchées par le gel accrus par augmentation de leur sensibilité (avancement de la saison végétative : Hänninen, 1991 ;Scheifinger et al., 2002 ;Gu et al., 2008 ;Sadras et al., 2009 ;Hufkens et al., 2012 ;Augspurger, 2013 ;Morin et Chuine, 2014 ;Bigler et Bugmann, 2018 ;Liu et al., 2018 ;Vitasse et al., 2018 ;sur la vigne : Briche et al., 2011 ;Mosedale et al., 2015 ;Sgubin et al., 2018 ;Chamberlain et al., 2019 ;Gavrilescu et al., 2019). En conséquence, au croisement de l'aléa météorologique et de la vulnérabilité d'origine phénologique, et ce malgré un contexte globalement plus chaud, les risques de pertes de production pour l'agriculture, l'arboriculture et la viticulture sont toujours présents, et parfois même plus sévères qu'autrefois pour une intensité de gel identique car les plantes sont moins acclimatées au froid (Castel et al., 2017) ou débourrent plus tôt (Sgubin et al., 2018). ...
... Une autre conséquence de l'événement gélif sur les tissus conducteurs est le phénomène d'embolie caractérisé par la formation de bulles d'air rompant les flux d'eau par cavitation (Sperry et Sullivan, 1992 ;Tyree et al., 1994 ;Cochard et al., 2001 ;Tyree et Zimmermann, 2002 ;Sevanto et al., 2012). De nombreux cas ont été observés aux États-Unis en 2007 (Gu et al., 2008 ;Augspurger, 2009), en 2010 (Hufkens et al., 2012) et en 2012 (Kistner et al., 2018) ; en France en 1995 (Ningre et Colin, 2007) ; ou encore en Suisse, en Allemagne du Sud et dans le nord-est de la France en 2011 et en 2016 (Kreyling et al., 2012 ;Vitasse et al., 2018). À un pas de temps plus fin, une chute de pluie précédant un épisode de gel aggrave l'impact de la gelée proprement dite, puisque l'eau peut geler sur la plante elle-même et ainsi provoquer des dégâts à une température plus élevée qu'en situation préalablement sèche (Christner et al., 2008). ...
Night-time clear and calm weather conditions cause a highly contrasting fine-scale spatial temperature distribution, locally depending on topographic features, type of soil and land cover. The combination of meteorological and geographical features with plant phenology points out the strong sensitivity of spring phenology to the occurrence of late frosts. Spring frosts can have serious impacts on plant growth and can penalize economic sectors depending on fruit and wine production. Therefore, spring is the most monitored season. Strong frosts occurred in France in late April 2016, causing local and long-lasting (several consecutive hours) temperature records below -5°C in some lowland places. The same features occurred in spring 2017 and 2019. The study of the combined meteorological and topoclimatic features causing the spring frosts of 2016 in France was carried out in the lower and middle Loire Valley. This part of the Loire valley is one of the studied wine regions of the European project LIFE-ADVICLIM (ADaptation of VIticulture to CLIMate change: High resolution observations of adaptation scenarii).In this study, the following points are developed: the climate conditions in the geographical context of the lower and middle Loire Basin; the synoptic scale meteorology associated with late frosts and the peculiarity of spring frost compared to winter frost. The cold event of 27 April 2016 between Nantes and Orléans is analysed using a methodology that takes into account geography at fine scales. A comparative study is carried out between two nearby weather stations, representative of different local-scale geographical contexts: Romorantin, located on a valley floor with a sandy soil, and Lye, located on an open hilltop. The results show how the nested space-time scales must be taken into account to explain the contrasting temperature distribution: the synoptic scale allows frost risk triggering, while at local scale their effective impacts on the studied site to be highlighted, in terms of intensity and duration of the frost event.
... Another negative effect of climate change is the alteration of tree phenology, which predicts that several phonologically responsive species in the US and Europe, including fruit trees, will experience more frost damage in the future [17]. In Europe, for example, increasing spring temperatures over the last three to four decades have advanced apple blooming by an average of 2-3 days per decade [18,19], resulting in an increased risk of frost, particularly for apples growing at higher elevations [18,19]. Traditional frost management techniques, such as microclimate-alteration, are costly, time-consuming, unpredictable, and environmentally unsustainable [20]. ...
... Another negative effect of climate change is the alteration of tree phenology, which predicts that several phonologically responsive species in the US and Europe, including fruit trees, will experience more frost damage in the future [17]. In Europe, for example, increasing spring temperatures over the last three to four decades have advanced apple blooming by an average of 2-3 days per decade [18,19], resulting in an increased risk of frost, particularly for apples growing at higher elevations [18,19]. Traditional frost management techniques, such as microclimate-alteration, are costly, time-consuming, unpredictable, and environmentally unsustainable [20]. ...
... At higher altitudes (500-750 m asl), the phenological trends were almost the same for winter wheat and shrubs and herbs, so the wild species also showed the same phenological speed as the crop plants. Very similar outputs were also recorded for forest trees and fruit trees in Switzerland, where a stronger phenological shift occurred at higher elevations (predicted mean across species and all 50 stations: −3.9 days per decade) than at lower elevations (− 2.2 days per decade) (Vitasse et al. 2018). The difference between lower and higher elevations could be explained by the different temperature trends-stronger warming during late rather than early spring (Vitasse et al. 2018)-which was not proven according to our data (the temperature trends were not different at lower, middle or higher elevations). ...
... Very similar outputs were also recorded for forest trees and fruit trees in Switzerland, where a stronger phenological shift occurred at higher elevations (predicted mean across species and all 50 stations: −3.9 days per decade) than at lower elevations (− 2.2 days per decade) (Vitasse et al. 2018). The difference between lower and higher elevations could be explained by the different temperature trends-stronger warming during late rather than early spring (Vitasse et al. 2018)-which was not proven according to our data (the temperature trends were not different at lower, middle or higher elevations). The reason for the smaller phenological trends (in wild plants) at lower and middle elevations could be that phenophases occur early in the spring, which indicates that they could be limited by late frosts or photoperiods that decelerate the onset of phenophases. ...
Phenological shifts in wild-growing plants and wild animal phenophases are well documented at many European sites. Less is known about phenological shifts in agricultural plants and how wild ecosystem phenology interacts with crop phenology. Here, we present long-term phenological observations (1961-2021) from the Czech Republic for wild plants and agricultural crops and how the timing of phenophases differs from each other. The phenology of wild-growing plants was observed at various experimental sites with no agriculture or forestry management within the Czech Hydrometeorological Institute observations. The phenological data of the crops were collected from small experimental plots at the Central Institute for Supervising and Testing in Agriculture. The data clearly show a tendency to shift to earlier times during the whole observation period. The data also show some asynchrony in phenological shifts. Compared with wild plants, agricultural crops showed more expressive shifts to the start of the season. Phenological trends for crop plants (Triticum aestivum) showed accelerated shifts of 4.1 and 5.1 days per decade at low and middle altitudes, respectively; on the other hand, the average phenological shift for wild plants showed smaller shifts of 2.7 and 2.9 days per decade at low and middle altitudes, respectively. Phenological data also showed variability in correlations with climate parameters (only one phenophase of T. aestivum, heading, showed a statistically significant correlation not only with temperature but also with precipitation). To better understand theimpacts of climate on phenological changes, it is optimal to evaluate natural and unaffected plant responses in wild species.
... Recently, FSEs have been investigated mostly in moderate mid-latitudinal climate zones. For example, disproportionate changes of the last day of frost (LDF) during spring and the SGS have been shown for central Europe (Vitasse et al., 2018;Zohner et al., 2016) and the United States (Peterson and Abatzoglou, 2014). Chen et al. (2021) demonstrated a negative correlation between the SGS date and mean air temperature over temperate China, indicating an earlier SGS under warmer conditions. ...
... The same as Fig. 9 but for HDCE 95 . cuss potential reasons for the large regional variability, including elevation (Vitasse et al., 2018) and distance from the sea (Ma et al., 2019). The findings of this study also demonstrate these two drivers as decisive when determining the potential future risk of FSEs. ...
The Mediterranean Basin is one of the regions most affected by climate change, which poses significant challenges to agricultural efficiency and food security. While rising temperatures and decreasing precipitation levels already impose great risks, the effects of compound extreme events (CEEs) can be significantly more severe and amplify the risk. It is therefore of high importance to assess these risks under climate change on a regional level to implement efficient adaption strategies. This study focuses on false-spring events (FSEs), which impose a high risk of crop losses during the beginning of the vegetation growing period, as well as heat–drought compound events (HDCEs) in summer, for a high-impact future scenario (Representative Concentration Pathway (RCP) 8.5). The results for 2070–2099 are compared to 1970–1999. In addition, deviations of the near-surface atmospheric state under FSEs and HDCEs are investigated to improve the predictability of these events. We apply a multivariate, trend-conserving bias correction method (MBCn) accounting for temporal coherency between the inspected variables derived from the European branch of the Coordinated Regional Climate Downscaling Experiment (EURO-CORDEX). This method proves to be a suitable choice for the assessment of percentile-threshold-based CEEs. The results show a potential increase in frequency of FSEs for large portions of the study domain, especially impacting later stages of the warming period, caused by disproportionate changes in the behavior of warm phases and frost events. Frost events causing FSEs predominantly occur under high-pressure conditions and northerly to easterly wind flow. HDCEs are projected to significantly increase in frequency, intensity, and duration, mostly driven by dry, continental air masses. This intensification is several times higher than that of the univariate components. This study improves our understanding of the unfolding of climate change in the Mediterranean and shows the need for further, locally refined investigations and adaptation strategies.
... Weather anomalies, increasing temperatures, the shifting boundaries of agroecosystems and increased incidence of extreme weather phenomena such as drought, hail, flood or hurricane necessitate adaptation. However, despite the observed global warming, many regions, for example in Switzerland, Germany, or Poland, face a non-decreasing risk of frost [1][2][3][4]. This is because climate change causes an acceleration of both the beginning of the growing season, as well as the occurrence of the last spring frosts. ...
... Interestingly, there is an increase in the number of days with air frost in spring in the fifth decade and in autumn in the fourth decade (Figure 9), as is the case with ground frosts. Numerous authors point to the fact that the risk of frost, particularly of spring frost, is not decreasing and is in fact increasing despite the warming climate [1,2,[6][7][8]14,39,40]. Updating the dates of the occurrence of frost in consecutive decades, just as in the case of ground frosts, it was found that there is a general acceleration in spring and deceleration in autumn together with an increase in span over particular years. ...
Fruits, garden plants, and agricultural crops grown in Poland exhibit wide variations in their sensitivity to frost, particularly in early spring. In the case of frost, generally, the yield and quality are reduced, and sometimes, entire plants can be destroyed. This article characterizes the occurrence of ground frosts (at 5 cm agl) and air frosts (at 200 cm agl) in Poland gathered from 52 meteorological stations affiliated with IMGW-PIB between 1971 and 2020. To assess the real risk of frost to plants, the variability of this phenomenon was analyzed per thermal growing season (defined as air temperature >5 °C), rather than in traditional calendar terms as presented in most studies. In the climatic conditions of Poland, the growing season is characterized by a reported 28 days with ground frost and 13.3 days with air frost, approximately. In spring, the last ground frost disappears, on average, on a country scale, on May 14, and air frost on April 27. In turn, in autumn, the first ground frost is recorded, on average, on 1 October and air frost on 14 October. On the basis of the selected characteristics of frost and the growing season, four areas of potential risk of ground and air frost in the growing season, as well as in spring, were determined with the use of cluster analysis.
... However, many uncertainties surround this strategy, not least the fact that southern-sourced populations may be poorly adapted to current conditions at northern sites. For example, seed sourced from a southern population should be adapted to local seasonal timing and at northern locations may flush leaves early in spring and senesce late in autumn leaving them vulnerable to early or late frosts in contemporary environments (Broadmeadow et al., 2005;Vitasse et al., 2018). Damage incurred in early growth stages may not be overcome even if individuals survive. ...
... Spring phenology is advancing under climate change (Fu et al., 2014;Roberts et al., 2015;Thackeray et al., 2016). However, advances in the timing of key spring phenological events such as bud-burst can be greater than the advance in the date of the latest spring frost (Klein et al., 2018;Vitasse et al., 2018), andZohner et al. (2020) found that latespring frost risk has increased in Europe since 1959. Furthermore, some environmental factors, such as photoperiod, will not vary under climate change and interactions may be important. ...
... In the 20th century, the increase in minimum temperature reported in the northern hemisphere was higher than that of the maximum temperature [2,3]. However, in the last few decades, in Western and Central Europe, there has been approximately a two-fold increase in maximum temperature [4]. An increase in air temperature affects vegetation and has a significant effect on the dates of the beginning, end, and duration of the growing season. ...
... Climatic projections taking into consideration the growing season point to a greater risk of frosts after the beginning of the spring growth of plants in a warming climate [4,62,63]. There are also numerous studies [64,65] indicating that despite warmer winters, there is a lengthening of the period in which frosts may occur, regardless of the established lengthening of the frost-free period. ...
Frosts cause damage to plants in field crops and also trees, thus contributing to heavy economic losses in agriculture. One of the consequences of climate warming is the lengthening of the thermal growing season (AT > 5 °C) and acceleration of phenological phases as well as the lengthening of the frost-free period. This favourable element allows the extension of the range of cultivated plants to include plants requiring warmth and a longer development period. The present study concerns the area of Poland. The data on mean and minimum 24-h period air temperature (200 cm above ground level) were obtained from 52 meteorological stations of the Institute of Meteorology and Water Management—National Research Institute (IMGW-PIB) for the period 1971–2020. A day with air frost was identified when the recorded minimum air temperature was below 0.0 °C and the mean 24-h period air temperature was above 0.0 °C. All calculations concerning frosts were limited to the period with mean 24-h period air temperature >5 °C (the growing season) as determined with the Gumiński method. The obtained results show that in the thermal growing season (AT > 5 °C) in Poland, no statistically significant change in the average number of days with air frosts in the period 1971–2020 was found. On average, in Poland, in the years 1971–2020, a lengthening of the thermal growing season by 6.2 days over 10 years was identified. Earlier disappearance of the latest air frosts in spring was identified as 2 to 3 days over 10 years, and the later occurrence of air frosts in autumn as 1 to 4 days over 10 years. The share of severe (−4.1°C ÷ −6.0 °C) and very severe (<−6.0 °C) frosts in the total number of days with air frosts in Poland amounts to, on average, 5.8% in spring and 2.6% in autumn.
... Vol. 32, No. 4 (2023), [1][2][3][4][5][6][7] Original Research ...
... He added that the role of spring frosts, hail, summer drought, and spring rain in reducing productivity and fruit quality cannot be ignored. According Vitasse [4], during analyzed long-term temperature data from the period 1975-2016 in 50 locations in Switzerland and used different phenological models calibrated with long-term series of the flowering and leaf-out timing of two fruit trees (apple and cherry) to test whether the risk of frost damage has increased during this period. ...
... This last date was defined to cover the whole of winter and early spring until leaf emergence, which occurs at the end of April in the study area (Millerón et al., 2012). Accumulated warm winter and spring temperatures above a certain threshold are a good proxy for predicting leaf emergence (Vitasse et al., 2018a), and an early leaf emergence can lead to a higher risk of late frost (Sangüesa- . Other variables, such as growing-degree days until last frost or the difference between the mean temperatures of the 10 days before the last frost and the absolute minimum temperatures during the last frost, were also obtained but were not useful to characterizing the pointer years and are therefore not shown in the results. ...
Studying growth declines and the factors that cause them, such as droughts or late spring frosts, is key to understanding their influence on forest productivity. However, most of the currently used methodologies to assess these events have drawbacks that can lead to erroneous conclusions. The increasing frequency and importance of these growth declines is linked to a higher climate variability and thus requires more effort to find suitable approaches to quantify their impacts on long-term tree growth. Furthermore, dendroecology generally focuses its efforts on the study of growth relationships with prevailing climatic conditions, giving little weight to the effect of occasional and discrete climatic events on medium-and long-term growth dynamics. Here, we develop a new methodology that consists in: (I) analyzing the largest growth reductions, (II) characterizing climate in those years, (III) identifying the change points in the tree growth function using Bayesian regression, and (IV) quantifying the impact of climate on short-, medium-and long-term growth trends using relative growth and cumulative growth loss indices. We studied the drops in growth suffered by European beech (Fagus sylvatica), caused by both droughts and late frosts. The study was conducted in stands with contrasting structural features (diameter, age) at the southwestern species distribution limit in the central Iberian Peninsula. Our results indicate that extreme climate events have caused a decade of growth loss in old trees (age ca. 100-330 years), and are the factor responsible for the decline of tree vigor. However, the relationships between prevailing climate conditions and tree growth were not significant, highlighting the importance of occasional and discrete climate events as the main drivers of growth. Tree age, rather than tree diameter, shapes tree growth response to extreme climate events such as droughts and late frosts.
... In contrast, deciduous tree species generally follow a "quick" strategy, quickly capturing light energy to meet the carbon demands for tree growth within a short growing period (Chen and Xu, 2014;Reich and Cornelissen, 2014), and tend to bud burst earlier. However, early bud burst increases the susceptibility to cold and frost damage (Kollas et al., 2014;Vitasse et al., 2018). For evergreen conifer species, the contribution of the current year needles to photosynthesis is limited, and the benefits of early bud burst are less pronounced. ...
Leaf and cambium phenologies are both important aspects of tree environmental adaptation in temperate areas. Temperate tree species with non-porous, diffuse-porous and ring-porous woods diverge substantially in the strategy of coping with freezing-induced hydraulic dysfunction, which can be closely associated with the timing of both leaf phenology and xylogenesis. Nevertheless, we still know little about the potential differences in the intra-annual process of xylogenesis among species of the three functional groups as well as its association with leaf phenology. Here, we monitored leaf phenology and xylogenesis in a non-porous (Pinus), a diffuse-porous (Populus), and a ring-porous (Ulmus) temperate tree species in a common garden. The results showed clear divergences in leaf and cambium phenologies and their chronological orders among the three species. The two hardwood species exhibited earlier bud burst and leaf unfolding than the conifer. The cambial activity of the ring-porous species began earlier than the diffuse-porous species, although the leaf phenology of the diffuse-porous species was earlier. The conifer species showed the latest bud break but the initiation of cambium activity was the earliest, which can be attributed to its strong resistance to freezing-induced embolism in the tracheid-based xylem. The leaf phenology preceded the onset of cambial activity in the Populus species, which was permitted by the ability of diffuse-porous species in largely retaining the stem hydraulic function over the winter. In contrast, the Ulmus species with ring-porous wood had to restore its severely hampered stem hydraulic function by winter embolism before leaf flush. The results revealed that leaf and cambium phenologies are closely interconnected due to the coordination between xylem water transport and leaf water demand. These findings contribute to a better understanding of the divergent adaptive strategies of temperate trees with different wood types.
... Hail, especially during flowering and fruiting periods, can severely harm fruit trees like apples, peaches, plums, and cherries (Groatjahn et al., 2021). Smaller hailstones can bruise the fruits, reducing their quality and yield (Bal, 2014), instead severe hailstorms and windstorms during summer can devastate cherry, apple, plum, peach, and apricot crops (Vitasse et al., 2018). Even brief hail events can severely damage fruits and trees, leading to quality degradation and increased susceptibility to diseases like fire blight, cankers, and fruit rots (Choudhary et al., 2015). ...
The hailstorm damages occurring in the context of climate change are among the greatest threats to the production and quality of orchard fruits. As example, a large hailstorm (approximately 1.5-2 cm in diameter) occurred at the beginning of June 2024 caused significant damage to orchards in the Bistrița hills area. In this context, a study was conducted to elucidate the possibility of identifying apple cultivars that, through their particular characteristics, can mitigate the damage caused by hail. The effects of the hail was assessedthrough observations in a field trial established in 2021 at FRDS Bistrița which includes 33 cultivars and two hybrids. The study aimed to observe the sensitivity of apple cultivars to mechanical damage caused by hail on the fruits. Thus, a sample of 100 fruits was collected from each cultivar from the northern side of the tree (the side from which the hail hit). The extent of fruit damage was estimated according to the methodology applied in plant protection. According to the degree of damage, the apple cultivars were categorized into the following groups: cultivars with deep, closed lesions (Valery, Bistrițean, Dany, Gala Decarli Fendeca, Gala Ferplus, Florina, Luca, Cezar, Dacian, Idared, Red Topaz, Generos, Opal, and Redix) and cultivars with open lesions, pulp destroyed by more than 50% (Orion, Sirius, Golden clone B, Starkprim, Choupette, Gala Decarli Fendeca, Rebra, Crimson Crisp, Salva, Doina, Alex, Inedit, BN 1/1-98, Goldrush, Ifo 1/6, Goldprim, Luna, Rustic, Auriu de Bistrița, Ionaprim, and Ariwa). The data collected are useful not only for the microzoning of cultivars but also for apple breeding programs targeting the development of cultivars with fruit characteristics that can mitigate the effects of hail.
... Increasing frequent and severe frost events caused by global climate changes pose significant threats to the survival, yield, and quality of these crops [20][21][22]. Paradoxically, the risk of cold injury has risen alongside global temperature increases [23], particularly in high-altitude and high-latitude areas where fruit and nut trees are grown [24,25]. As a result, cold injury has become a pressing concern in regions like Central Asia and Europe, where walnut production is integral to local economies and livelihoods [20,26]. ...
As global climate change escalates, horticultural crops, especially walnuts, face increased vulnerability to frost damage. Cold hardiness—a crucial trait for survival—is influenced by complex physiological and biochemical mechanisms. This study assessed the cold hardiness of five walnut cultivars—‘Xinxin 2’, ‘Wen 81’, ‘Wen 185’, ‘Zha 343’, and ‘Xinzaofeng’—under simulated low-temperature stress, focusing on differences in freezing tolerance. One-year branches were gradually cooled to temperatures as low as −30 °C. Key physiological metrics, including electrolyte leakage (EL) and regrowth (RG) potential, along with biochemical metrics like antioxidant enzyme activities and osmoregulatory compounds, were used to evaluate cold hardiness. A comprehensive cold resistance indicator, derived using the subordination function method, highlighted cultivar resilience. Results showed significant variation in cold tolerance, with ‘Wen 185’ and ‘Wen 81’ exhibiting superior resilience, while ‘Xinxin 2’ was the most susceptible. Logistic regression analysis of relative electrolyte conductivity (REC) data estimated the semi-lethal temperature (LT50), identifying ‘Wen 81’ as the most cold-tolerant cultivar (LT50 = −21.73 °C). Antioxidant enzymes and osmoregulatory compounds were crucial for maintaining cellular stability and recovery after freezing. These findings offer practical insights for breeding cold-resistant cultivars and strategies to mitigate frost damage.
... This is due to an extension of the frost-free stage and a decrease in FD throughout the year. However, despite this, frost damage is not mitigated (Fang et al., 2011;Pfleiderer et al., 2019;Vitasse et al., 2018). ...
The spring frost over northeast China significantly affects local socioeconomic development; however, the variations and underlying mechanisms remain unclear. The present study explored the spatiotemporal attributes of spring frost days (FD) over northeast China in recent decades, and the potential mechanisms underlying their interannual variations. The results indicated an evident decline in spring FD over northeast China, accompanied by substantial interannual variation. Further analyses suggested that anomalous springtime North Atlantic tripole sea surface temperature (SST) and Eurasian snow depth are critical factors controlling the interannual variations of spring FD in northeast China. Rossby wave trains can be stimulated by the anomalous North Atlantic tripole SST (NAT), which propagates eastward through the Eurasian continent to northeast China, significantly affecting the atmospheric circulation along the pathways. This results in anomalous negative geopotential heights and cyclonic circulation over northeast China, causing low‐temperature anomalies by moderating wind‐induced alterations in surface heat fluxes and cloud‐induced modifications in surface radiation. Meanwhile, Eurasian snow depth anomalies represent a consistent effect with NAT. The anomalous Eurasian snow depth may modify the atmosphere thickness by regulating surface heat flux, promoting the propagation of wave trains as a snow‐atmosphere bridge, which enhances the impact of NAT on FD. In addition, it also triggers the Rossby wave trains to spread from high‐latitude Siberia to northeast China. Both of these processes have a considerable impact on the local atmospheric circulation. Consequently, these two factors contribute to local surface cooling, thereby increasing the spring frost occurrence over northeast China.
... 200 °C-days) are projected to increase at Edmonton while projected increases in exceedance probabilities are for moderate values (20 -100°C-days) at Ottawa and Halifax. Long-term series of phenological observations in Switzerland showed that cherry trees require 147 GDD5 and apple trees 219 GDD5 to flower (Vitasse et al. 2018a). Cherry and apple trees might therefore be vulnerable to subfreezing temperatures in some regions of Canada. ...
Winter climate conditions, especially extremely low temperatures, constrain the production of fruit trees and other perennial crop species in Canada. Significant decreases in cold extremes under climate change may result in changes in plant hardiness zones and the distribution of crop species across the country. Climate warming might also bring changes to climate conditions that affect fall hardening, loss of cold hardiness due to winter thaws, and spring frost damages. Using the most up-to-date climate projections, we provide projected changes in the risks of damages to fruit trees during winter based on five agroclimatic indices and changes to the United States Department of Agriculture (USDA) plant hardiness zones based on long-term averages of annual extreme minimum air temperatures in the near-term (2030s, 2020–2049), mid-term (2050s, 2040–2069), and distant future (2070s, 2060–2089). Our results suggest that climate change might be beneficial for fruit trees across Canada with (1) improved fall hardening because of more time to acquire cold hardiness due to delayed first fall frost and (2) decreased winter coldness with increases in annual minimal temperatures and decreases in the accumulation of cold degree-days below –15 °C. The risks of loss of cold hardiness due to winter thaws will increase slightly while the risks of spring frost damages to buds will be largely unchanged. Under a warmer distant future, the USDA plant hardiness zones across Canada would increase by 1.5–2 “full” zones, which may lead to the introduction of new fruit tree species and opportunities for Canadian producers.
... In many regions, early spring warming does not preclude the occurrence of freezing events (Shaw and Etterson, 2012;Allen et al., 2014;Fitchett et al., 2014;Meng et al., 2019) and it can lead to "false springs", where early warming leads to budburst and is followed by a damaging freeze event (Gu et al., 2008;Chamberlain et al., 2019). False springs are increasingly prevalent across the temperate parts of the world (Augspurger, 2011;Vitasse et al., 2018;Ma et al., 2018;Warren and Vermette, 2022; but see Park et al., 2021), including in the midwestern United States (Allstadt et al., 2015). Because many woody plants are among the first to flower in the spring, their reproductive tissue may be especially susceptible to false springs (Inouye, 2000;Winde et al., 2017;Pardee et al., 2018). ...
Premise
There are advantages to flowering early in the spring, including greater pollinator fidelity and longer fruit maturation time. But plant phenology has advanced in recent years, making many plants vulnerable to freezing damage from late frosts.
Methods
To determine the costs and benefits of flowering early in the growing season, we exposed Prunus pumila plants to two freezing treatments and a delayed flowering treatment in subsequent years. Data were collected on ovary swelling, fruit production, and pollinator visitation on hand‐ and open‐pollinated plants in all treatments. We also measured tissue damage after freeze events.
Results
Our results suggest that flowering time and temperature affect reproductive success, with fewer fruits produced after hard freezes. The same was not true for light freezes, which had minimal impact on reproduction. Freezing damage to plants after a hard freeze did affect the number of dipteran pollinators but not the overall pollinator visitation rate. Despite the clear impact of freezing temperatures on plant reproduction, flowering early provided an advantage in that reproductive output decreased with delayed flowering.
Conclusions
Our findings suggest that Prunus pumila will retain the ability to attract pollinators and produce viable seeds if exposed to false spring conditions that involve a light freeze, but hard freezes may reduce yield by an order of magnitude. Although the advantages to flowering early may outweigh the risk of freezing damage under current conditions, it is possible that flower viability may be constrained under continued climate warming.
... A number of researchers suggest that further warming will reduce the thermal sensitivity of plants due to winters that are too warm. This may move the onset of flowering to later dates without increasing the risk of plant damage by late spring frosts [10,11]. Other researchers believe that warming temperatures may shift the onset of flowering to earlier dates and increase the risk of spring frost damage [12,13]. ...
Siberian stone pine is one of the main edificator plants of taiga forests of Western Siberia. Sustainable functioning of forest ecosystems depends on its successful cone crops, as its seeds are the basis for the diet of many forest animals. A cone crop in this species is characterized by pronounced interannual variability, manifested in the formation of high seed yields once in 3-4 years. However, in the last 20 years, high yields have been rare, replaced by years with average and low yields. To establish the reasons for these changes, the dynamics of seeding in the period from 1990 to 2023 and weather conditions in spring in the pollination year during the same period were analyzed. It was found that the number of mature cones in the crown largely depended on spring weather in the year of pollination and was negatively correlated with the sum of active temperatures above +5°C accumulated before the late spring frost. If frost occurred at SAT above 300°C, the following year’s crop was minimized. Analysis of weather conditions showed that, on average, there is a tendency to shift the dates of the last frosts to later dates, and even a short-term decrease in temperature to -1 °C leads to complete death of the future crop of cones. Despite the growth of heat availability in the spring period due to active temperature increase in April, the expected shift of frosts to earlier dates is not observed in the south of Western Siberia. For Siberian stone pine, such situation is fraught with strengthening of negative trend in seeding dynamics. It is supposed that at further climate warming the beginning of spring development of reproductive structures will occur at earlier dates, so reproductive structures will be more damaged by late spring frosts, since the latter remain within the same time frames.
... The degree of fructification was found to depend on the temperature and occurrence of rather sunny and dry weather in the spring also in glacial relict Pulsatilla vernalis [76]. As climate change increases the incidence of extreme climatic events, higher spring temperatures may result in earlier flowering, increasing the risk of exposure to late frosts and subsequent fruit damage [28,30,32]. Indeed, late summer frosts exert a more pronounced negative impact on reproductive shoots, consequently affecting sexual reproduction success, compared to vegetative ones in the majority of studied high-mountain plants from the European Alps [82]. ...
The role of endemic species in global biodiversity is pivotal, and understanding their biology and ecology is imperative for their fitness and long-term survival, particularly in the face of ongoing climatic oscillations. Our primary goal was to investigate the sexual reproduction level of the endangered Western Carpathian endemic Daphne arbuscula (Thymelaeaceae), which inhabits extreme rocky habitats, and to comprehend the influence of specific factors on its reproductive success. We conducted the research across four populations, varying in size and environmental conditions. Over two years, we monitored flower and fruit production, analyzed genetic variability within and among populations, and studied pollination mechanisms. Daphne arbuscula proved to be strictly self-incompatible, with significant variations in flower and fruit production among populations and seasons. The average fruit production percentage consistently remained below 50% across populations, indicating challenges in sexual reproduction. Cold and harsh weather during the reproductive phase had a substantial negative impact on sexual reproduction efficacy, leading to decreased fruit production. Nevertheless, several individuals in sheltered microhabitats displayed significantly higher fruit production, ranging from 60% to 83%, emphasizing the critical role of microhabitat heterogeneity in sustaining sexual reproduction in this species. We found no pronounced differences in genetic diversity within or among populations, suggesting that genetic factors may not critically influence the reproductive success of this endemic species. The implications of our findings might be of paramount importance for the long-term survival of D. arbuscula and offer valuable insights for the development of effective conservation strategies for this species.
... When comparing the LT 50 values for each cultivar separately in each month across the 3 years, the differences ranged from 2.8°C ('Petra') to 5.1°C ('Bergarouge') in October and from 2.3°C ('Kurezia') to 6.3°C ('Harogem') in November, while from 0.6°C ('Primaya') to 5.8°C ('Bergarouge') in December and from 3.0°C ('Petra') to 8.1°C ('Bergarouge') in January, finally from 1.9°C ('Petra') to 7.2°C ('Harlayne', 'Goldrich') in February. Due to the mild winter weather, the cultivars did not achieve their genetically possible level of frost hardiness, which is a common occurrence in other fruit species (Szalay et al., 2017;Vitasse et al., 2018). ...
The effectiveness of apricot cultivation is greatly threatened by frost damage to flower buds during the dormancy period. One of the most important aspects of the evaluation of cultivars is therefore the determination of their frost tolerance. In this paper, the frost hardiness of flower buds of 16 apricot cultivars was investigated in three dormancy periods, applying a standardised artificial freezing test protocol and determining LT 50 values. The results showed that both the genotypes and the yearly climatic conditions had a significant effect on frost tolerance. A genotype generally determines the potential maximum of its frost tolerance (‘Sweet Red’ and ‘Primaya’ were very sensitive to frost every year, while ‘Harlayne’ and ‘Rózskajszi C.1406’ could be considered as frost hardy). Flower buds can reach different levels of frost resistance each year depending on the temperature conditions during the hardening and dehardening periods. From the point of view of yield security, it is essential when planning an orchard, to take into account and harmonise the frost hardiness of the cultivars selected and the growing site conditions. Therefore, it is very important to have adequate information about the frost hardiness of different apricot cultivars, which should be included in cultivar descriptions. This paper is intended to contribute to this goal.
... The extent of shifts found in the mentioned studies differed considerably between the tree species, locations and altitudes, and also depended on the length of analysed periods and their timing. Earlier spring development is associated with a higher risk of fruit and forest trees to frost exposure (Vitasse et al. 2018), especially when the probability of occurrence of late spring frosts is high (Škvareninová et al. 2022). ...
This study aims to analyse the phenological dynamics of tree species in response to changes in climatic conditions over the last two climate-normal periods (CLINO 1961−1990 and 1991−2020). We focused on the main climax tree species (Quercus species, Fagus sylvatica L., Abies alba Mill., Picea abies [L.] Karst., and Pinus mugo Turra) dominating eight altitudinal forest vegetation zones (FVZ) and alluvial forests of Western Carpathians and adjacent lowlands in Central Europe. The phenological phases analysed in this study were first leaf (BBCH11) and general leaf colouring (BBCH94) for deciduous species, and the onset of new shoots (BBCH10) for evergreen conifers. The results of partial correlations confirmed that temperature is the main driving factor explaining the shifted onset of phenological phases for the species considered. Furthermore, deciduous species growing in the lower (and warmer) FVZ showed a certain level of drought sensitivity related to the earlier BBCH94. The identified trends in phenology were species-specific and differed between the individual FVZs. The most pronounced shifts toward the earlier BBCH10 and BBCH11 were found in the upper FVZ of the vertical distribution range of species. The presented results will support our understanding of the mechanisms underlying environmental control of tree phenology. This is crucial for predicting how the growing season of trees will be constrained by climate changeinduced conditions in individual FVZ.
... Our results point to significant sensitivities to both time and temperature for oak as well as significant sensitivity to temperature for hornbeam, which is consistent with the results by Vitasse et al. (2009b). The advancement of budburst would increase the possibility of spring frost damage (Liu et al., 2018;Vitasse et al., 2018), influencing tree physiology and growth with possible impacts on the productivity of forests (Vitasse et al., 2019) or even the distribution of tree species (Chuine, 2010). ...
Spring phenology is a key indicator of temperate and boreal ecosystems' response to climate change. To date, most phenological studies have analyzed the mean date of budburst in tree populations while overlooking the large variability of budburst among individual trees. The consequences of neglecting the within-population variability (WPV) of budburst when projecting the dynamics of tree communities are unknown. Here, we develop the first model designed to simulate the WPV of budburst in tree populations. We calibrated and evaluated the model on 48 442 budburst observations collected between 2000 and 2022 in three major temperate deciduous trees, namely, hornbeam (Carpinus betulus), oak (Quercus petraea) and chestnut (Castanea sativa). The WPV model received support for all three species, with a root mean square error of 5.7 ± 0.5 d for the prediction of unknown data. Retrospective simulations over 1961–2022 indicated earlier budburst as a consequence of ongoing climate warming. However, simulations revealed no significant change for the duration of budburst (DurBB, i.e., the time interval from BP20 to BP80 (with BP representing budburst percent), which respectively represent the date when 20 % and 80 % of trees in a population have reached budburst), due to a lack of significant temperature increase during DurBB in the past. This work can serve as a basis for the development of models targeting intra-population variability of other functional traits, which is of increasing interest in the context of climate change.
... These factors may be the main causes of the differences in the PGSs in elevation bounds, as their aspect and long-term average daily temperatures are different because of the minimum 600 m elevation difference between the two bands. Considering the direct relationship between temperature and phenology, suggested by Sangüesa- Barreda et al. (2021), Bigler and Bugmann (2018) and Vitasse et al. (2018), the growing season in colder areas is shorter than in warmer ones, although this may vary with species. ...
... Late-spring frost damage can occur when below-freezing temperatures hit after budbreak or the first leaf-out. Exposure to frost during the initial stages of leaf emergence can have dramatic effects on growth and reproduction by affecting individual resource acquisition 28,32,33 . Plants experiencing a non-lethal stress can respond with a phenological shift in the subsequent year 34-36 . ...
Climate change is rapidly altering weather patterns, resulting in shifts in climatic zones. The survival of trees in specific locations depends on their functional traits. Local populations exhibit trait adaptations that ensure their survival and accomplishment of growth and reproduction processes during the growing season. Studying these traits offers valuable insights into species responses to present and future environmental conditions, aiding the implementation of measures to ensure forest resilience and productivity. This study investigates the variability in functional traits among five black spruce ( Picea mariana (Mill.) B.S.P.) provenances originating from a latitudinal gradient along the boreal forest, and planted in a common garden in Quebec, Canada. We examined differences in bud phenology, growth performance, lifetime first reproduction, and the impact of a late-frost event on tree growth and phenological adjustments. The findings revealed that trees from northern sites exhibit earlier budbreak, lower growth increments, and reach reproductive maturity earlier than those from southern sites. Late-frost damage affected growth performance, but no phenological adjustment was observed in the successive year. Local adaptation in the functional traits may lead to maladaptation of black spruce under future climate conditions or serve as a potent evolutionary force promoting rapid adaptation under changing environmental conditions.
... This shade-tolerant species requires well-drained, moderately deep soils, and relatively high atmospheric humidity and annual precipitations (Packham et al. 2012). It is sensitive to late spring frosts (Vitasse et al. 2018). European beech has been the subject of numerous studies on the environmental determinants of budburst (Caffarra and Donnelly 2011) and leaf senescence (Qiang et al. 2020;Vitasse et al. 2009b) as determinants of forest ecosystem productivity (Pilegaard and Ibrom 2017;Wu et al. 2013). ...
Key message
Phenology is of increasing interest to climate change science and adaptation ecology. Here, we provide bud development, leafing, and leaf senescence data, collected on 772 European beech and silver fir trees between 2006 and 2019 on Mont Ventoux, France. Dataset access is at https://doi.org/10.15454/TRFMZN . Associated metadata are available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/a33c8375-9a90-4bc3-a0d7-19317160b68f .
... In addition to heat, the cold hazards may affect plants, especially populations of recently latitudinally or altitudinally migrated plants, which would experience more frequent cold hazards than native habitats. Cold events are projected to occur with high anomaly (e.g., occurrence of frost events in spring after unusual warming) (Ipcc, 2014;Vitasse et al., 2018). Cold hazard affects the physiological performance of plants and slows down their migration to cooler climate areas (Wen et al., 2018). ...
Understanding how plants respond to thermal stress is central to predicting plant responses and community dynamics in natural ecosystems under projected scenarios of climate change. Although physiological tolerance is suggested to evolve slower than climatic niches, this comparison remains to be addressed in plants using a phylogenetic comparative approach. In this study, we compared i) the evolutionary rates of physiological tolerance to extreme temperatures with ii) the corresponding rates of climatic niche across three major vascular plant groups. We further accounted for the potential effects of hardening when examining the association between physiological and climatic niche rates. We found that physiological cold tolerance evolves faster than heat tolerance in all three groups. The coldest climatic-niche temperatures evolve faster than the warmest climatic-niche temperatures. Importantly, evolutionary rates of physiological cold tolerance were faster than rates of change in climatic niches. However, an inverse association between physiological cold tolerance and responding climatic niche for plants without hardening was detected. Our results indicated that plants may be sensitive to changes in warmer temperatures due to the slower evolutionary rates of heat tolerance. This pattern has deep implications for the framework that is being used to estimate climate-related extinctions over the upcoming century.
... The timing of seasonally recurrent biological phenomena (i.e., phenology) of trees has been shown to be sensitive to ongoing global warming (Schwartz, 2013). Recently, warming-induced shifts in phenological events, such as leaf-out, flowering and leaf coloration, have considerably influenced not only tree fitness and distribution but also forest functioning, including carbon, water, and energy fluxes (Chuine & Beaubien, 2001;Peñuelas et al., 2009;Richardson et al., 2013;Vitasse, Schneider, et al., 2018). Understanding the climate-phenology relationship is important for assessing and projecting the responses of forest ecosystems to a warming climate (Delpierre et al., 2016). ...
Aim
Temperature is the main driver of growth reactivation in plants of extratropical regions. Accumulations of chilling and forcing units during dormancy co‐regulate spring phenology. Here, we aimed to answer whether chilling and forcing proceed in parallel or sequentially to regulate spring phenology in temperate trees.
Location
Europe.
Time Period
1951–2016.
Major Taxa Studied
Nine temperate woody species.
Methods
Using long‐term and large‐scale records of in situ leaf unfolding dates of temperate tree species at more than 2300 sites, we analysed the rolling partial correlations between leaf unfolding dates and chilling and forcing in winter and spring using a weekly smoothing window. Through process‐based modelling, we further identified the start of forcing accumulation and the end of chilling accumulation using the Unified model and compared the model efficiency of the Parallel and the Sequential models.
Results
We observed negative responses of leaf unfolding dates to accumulations of both chilling and forcing units for most of winter and spring across successional types of species (early‐ and late‐successional taxa), elevations and periods. Using the Unified model, we also found overlapping windows for chilling and forcing accumulations. Moreover, the Parallel model performed better than the Sequential model. These findings suggested that chilling and forcing requirements may be fulfilled simultaneously in temperate trees.
Main Conclusions
Our study not only provides a guideline for identifying the effective periods of chilling and forcing, but also a general and robust perspective that accumulations of chilling and forcing act in parallel to regulate spring leaf unfolding in temperate trees, promoting more precise and reasonable predictions of temperature‐driven phenological shifts under future climate change.
... After the abrupt temperature change, Siberian larch exhibited a significant negative correlation with the precipitation of the previous winter ( Figure 5). Evergreen coniferous species usually use nonstructural carbohydrates from old leaves for bud burst, and it takes longer for new evergreen leaves to emerge [68,69]. However, the bud burst period of deciduous trees is earlier and is more affected by the low temperatures and frost in spring because these trees rely on the NSC from stems and branches for leaf development [70,71]. ...
With global warming, the frequency, intensity, and period of extreme climates in more areas will probably increase in the twenty first century. However, the impact of climate extremes on forest vulnerability and the mechanisms by which forests adapt to climate extremes are not clear. The eastern Tianshan Mountains, set within the arid and dry region of Central Asia, is very sensitive to climate change. In this paper, the response of Picea schrenkiana and Larix sibirica to climate fluctuations and their stability were analyzed by Pearson’s correlation based on the observation of interannual change rates of climate indexes in different periods. Additionally, their ecological adaptability to future climate change was explored by regression analysis of climate factors and a selection of master control factors using the Lasso model. We found that the climate has undergone significant changes, especially the temperature, from 1958 to 2012. Around 1985, various extreme climate indexes had obvious abrupt changes. The research results suggested that: (1) the responses of the two tree species to extreme climate changed significantly after the change in temperature; (2) Schrenk spruce was more sensitive than Siberian larch to extreme climate change; and (3) the resistance of Siberian larch was higher than that of Schrenk spruce when faced with climate disturbance events. These results indicate that extreme climate changes will significantly interfere with the trees radial growth. At the same time, scientific management and maintenance measures are taken for different extreme weather events and different tree species.
... results in frequent mild winter temperatures that are not favourable in hardening processes and has impact on the phenological processes of almond genotypes as well, similarly to other fruit trees (Egea et al. 2003;Eccel et al., 2009;Lamp et al. 2001;Kaukoranta et al., 2010;Di Lena et al. 2017;Benmoussa et al 2017;Vitasse et al. 2018;El Yaacoubi et al. 2019). It is difficult to compare our results with previous research results, as such a systematic study of the frost resistance of flower buds of almond genotypes has not yet been performed. ...
Frost hardiness of flower buds of twenty almond genotypes was investigated in five dormancy periods by determining LT 50 values after artificial freezing tests. The main aim of our work was modelling the changing of frost hardiness of the observed accessions during dormancy and assessing the potential best frost tolerance of them. The effect of genotype and year had significant impact on frost hardiness of flower buds. The potential frost hardiness of accessions has been characterised by LT50 values of flower buds averaged of the bests of the four years. ‘Sóskút 96/5’ was the most sensitive with -17.16 °C, and ‘Tétényi keményhéjú’ was the most frost hardy with -21.08 °C in averaged of years, but both showed lower and higher frost tolerance as well in different years. Flower buds were most frost-tolerant in December and January but did not achieve the same frost resistance every year. From this, we conclude that temperature plays an important role in the hardening process of them. From the aspect of safe yield, frost hardiness of flower buds is an important trait of cultivars, because Hungary is situated at the northern part of economical almond growing area. Our work contributes to facilitating practical considerations in orchard planning.
... Global warming leads to accelerated crop growth so that reproductive growth stages occur earlier in the season (Eccel et al. 2009). This can increase frost risks, especially in more continental regions such as Austria, France and Switzerland (Legave et al. 2015;Unterberger et al. 2018;Sgubin et al. 2018;Vitasse et al. 2018). ...
Weather risks threaten food production and put farms’ profitability at risk. Insurance solutions can compensate for the resulting financial losses and thereby serves as important risk management tool. While insurance providers in Europe have recently largely expanded the number and scope of offered weather insurance solutions, this remained undocumented in scientific literature. We here provide a structured assessment of agricultural insurance products that are on the market to cover weather risks in crop and horticulture production in dynamic European insurance markets, focusing on Austria, France, Germany, Italy, Spain and Switzerland. We systematically collect information on supplied insurance products (N = 107) and find large diversity in market concentrations, offered products, insured weather risks, and political market interventions. We find that for most economically relevant weather risks (especially for hail), insurance solutions are available to farmers, but we identify certain insurance protection gaps (e.g., flood in Germany). Additionally, drought and heat risks seem underrepresented in current insurance products, especially given their economic relevance. Indemnity insurance (where payouts are based on assessed losses) is offered most frequently, but weather index insurance (where payouts depend on the realization of an index, such as cumulative precipitation) is also increasingly available in Europe. Most of current weather index insurance solutions have a unique design, indicating a preference to stand out from the competition, and we observe little knowledge spillovers between markets. There are different levels of political market intervention and in particular a trend to introduce premium subsidies and towards a convergence of premium subsidy levels between markets. We highlight the need to align any political market intervention to other policy goals and to the transition to a more sustainable agriculture. Finally, we underline the important role of research in improving current insurance systems.
The Forest Report 2025 is the third publication of its kind, with previous versions appearing in 2005 and 2015. It is aimed at experts and anyone interested in forest and wood-related issues. The report provides an overview of the condition and development of Swiss forests over the past ten years and assesses the outlook for all relevant areas against the backdrop of advancing climate change. With a structure modelled on Forest Europe reports, the Forest Report sets out internationally comparable results and serves as a benchmark publication. It uses a broad range of data from long-term surveys to answer important questions for society, economic players and policymakers.
Der Waldbericht erscheint 2025 zum dritten Mal nach 2005 und 2015. Er richtet sich an Fachleute und an eine am Thema Wald und Holz interessierte Leserschaft. Der Waldbericht ist eine Gesamtschau über Zustand und Entwicklungen des Schweizer Waldes in den letzten zehn Jahren und gibt einen Ausblick für alle Themenbereiche im Hinblick auf den fortschreitenden Klimawandel. Mit seiner an den Berichten von Forest Europe orientierten Struktur liefert der Waldbericht international vergleichbare Ergebnisse und dient als Referenzpublikation. Er beantwortet anhand einer breiten Datenbasis aus Langzeiterhebungen wichtige Fragen für Gesellschaft, Wirtschaft und Politik.
• Defoliation in Swiss forests is tending to increase, with strong annual fluctuations. This is apparent from the results of the Sanasilva Inventory and the Inter-cantonal Forest Observation Programme (WDB).
• An increase in mortality is observed in some tree species, this also being subject to annual fluctuations.
• The annual fluctuations can be partly explained by extreme events such as storms or drought years. The upward trends seen over the past ten years could intensify further if the extreme events predicted by climate models become more frequent.
Convergent and parallel evolution occur more frequently than previously thought. Here, we focus on the evolutionary adaptations of angiosperms at sub-zero temperatures. We begin by introducing the history of research on convergent and parallel evolution, defining all independent similarities as convergent evolution. Our analysis reveals that frost zones (periodic or constant), which cover 49.1% of Earth’s land surface, host 137 angiosperm families, with over 90% of their species thriving in these regions. In this context, we revisit the global biogeography and evolutionary trajectories of plant traits, such as herbaceous form and deciduous leaves, that are thought to be evasion strategies for frost adaptation. At the physiological and molecular levels, many angiosperms have independently evolved cold acclimation mechanisms through multiple pathways in addition to the well-characterized C-repeat binding factor/dehydration-responsive element binding protein 1 (CBF/DREB1) regulatory pathway. These convergent adaptations have occurred across various molecular levels, including amino acid substitutions and changes in gene duplication and expression within the same or similar functional pathways; however, identical amino acid changes are rare. Our results also highlight the prevalence of polyploidy in frost zones and the occurrence of paleopolyploidization events during global cooling. These patterns suggest repeated evolution in cold climates. Finally, we discuss plant domestication and predict climate zone shifts due to global warming and their effects on plant migration and in situ adaptation. Overall, the integration of ecological and molecular perspectives is essential for understanding and forecasting plant responses to climate change.
Temperate woody perennial plants form buds during late summer that contain leaves and flowers that emerge in the following growth season. To survive winter, dormant buds must attain cold hardiness, and timely lose it in spring to break bud while avoiding damage from low temperatures and late frosts. Here, we use an untrained process-based model to predict bud cold hardiness of three grapevine varieties ( V. vinifera 'Cabernet-Sauvignon' and 'Riesling', and V. hybrid 'Concord') from historical temperature records of eight different locations in North America and Europe (n = 329). Based on those predictions, and thresholds of cold hardiness at budbreak from literature, timing of budbreak was extracted. Despite being untrained to the data, the RMSE of budbreak predictions was 7.3 days (Bias=−0.83). Based on cold hardiness estimations and air temperature records, low temperature damage was quantified and validated through newspapers and extension records. In years × location where damage was predicted, corrections to budbreak based on delays expected resulted in improvements of predictions (RMSE=7.2d, Bias=0.58). Predictions of instances of freeze damage risk demonstrate genotypic adaptation to different environments. At the species level, increasing or decreasing trends in freeze damage risk are predicted, depending on the range of mean dormant season temperature (MDST; 1 Nov - 30 Apr) present in each location. Sensitivity analysis of predicted time to budbreak based on MDST shows a general advancement of phenology at −5.8d/°C. However, in much warmer locations, delays can be expected as temperatures continue to increase (+1.9d/°C for MDST>10°C). Through cold hardiness dynamics, the estimation of chilling accumulation appears as an important source of error for predictions of spring phenology across environments. Cold dynamics represents an advancement in phenological modeling that provides information for the entirety of the dormant season, as well as budbreak.
In this chapter, we provide an overview of plant phenology modeling, focusing on mechanistic phenology models. After a brief history of plant phenology modeling, we present the different models, which have been described in the literature and highlight the main differences between them, i.e. their degree of complexity and the different types of response function to temperature they use. We also discuss the different approaches used to build and parameterize such models. Finally, we provide a few examples of applications mechanistic plant phenology models have been successfully used for, such as the modeling of frost hardiness, forest growth and distribution, evolutionary dynamics of phenological traits, and the reconstruction of temperature during the last millennium.
In the context of climate warming, the compound dry-hot (CDH), dry-cold (CDC), wet-hot (CWH), and wet-cold (CWC) events have become more frequent and widespread in recent decades, causing severe but disproportionate impacts on terrestrial vegetation. However, the understanding of how vegetation vulnerability responds to these compound climate events (CCEs) is still limited. Here, we developed a multivariate copula conditional probabilistic model integrating the Standardized Precipitation Index (SPI), Standardized Temperature Index (STI), and Normalized Difference Vegetation Index (NDVI) together to quantify the vegetation response to each of CDH, CDC, CWH and CWC events under diverse climates in mainland China. Results show that CDC events result in the largest probability of vegetation loss relative to other three CCEs, with the probability of NDVI below the 40% percentile being 4.8%-13.0% (0.5%-2.6%) larger than individual dry (cold) events. In contrast, CWH leads to the lowest vegetation loss probability among all CCEs, with the probability of NDVI below the 40% percentile being 5.6% ~ 6.9% (4.2% ~ 5%) less than individual wet (hot) events. The response of vegetation vulnerability to CCEs varies considerably with ecosystems and climate types. Vegetation in Loess Plateau and northwestern Xinjiang (Inner Mongolia) is highly susceptible to CDC (CDH) events, while that in northeastern and southern China (eastern coastal and southwestern regions) is more vulnerable to CWC (CWH) events. Shrubland, grassland and cropland exhibit higher vulnerability to CDC and CDH events, while deciduous (evergreen) forests are more vulnerable to CWC(CWH) events, which may be related to vegetation physiological characteristics, survival strategies, and climatic adaptations. This study enhances our understanding on the response of various vegetation types to CCEs, and provides theoretical support for the development of measures to mitigate climate hazards.
Background and Aims
As winter and spring temperatures continue to increase, the timing of flowering and leaf out is advancing in many seasonally cold regions. This advancement could put plants that flower early in the spring at risk of decreased reproduction in years when there are late freeze events. Unfortunately, relatively little is known about floral freezing tolerance in forest communities. In this study, we examined the impact of freezing temperatures on the flowers of woody plants in a region where there is rapid winter warming in North America.
Methods
We subjected the flowers of twenty-five woody species to a hard (-5ºC) and a light freeze (0ºC). We assessed tissue damage using electrolyte leakage. In a subset of species, we also examined the impact of a hard freeze on pollen tube growth. To determine if the vulnerability of flowers to freezing damage relates to flowering time and to examine the responsiveness of flowering time to spring temperature, we recorded the date of first flower for our study species for three years.
Key Results and Conclusions
Across species, we found that floral freezing tolerance was strongly tied to flowering time with the highest freezing tolerance occurring in plants that bloomed earlier in the year. We hypothesize that these early blooming species are unlikely to be impacted by a false spring. Instead, the most vulnerable species to a false spring should be those that bloom later in the season. The flowering time in these species is also more sensitive to temperature, putting them at a great risk of experiencing a false spring. Ultimately, floral damage in one year will not have a large impact on species fitness, but if false springs become more frequent, there could be long-term impacts on reproduction of vulnerable species.
Spring frosts during flowering and fruit setting often deprive the plum of the harvest, worsen the general condition of trees and the quality of fruits. In this regard, the purpose of the research was to isolate plum varieties resistant to spring frosts for breeding use. The research was carried out in 2022-2023 at the sites of the primary variety study of stone crops and in the laboratory of the Physiology of the stability of fruit plants of the Russian Research Institute of Fruit Crop Breeding. The objects of the study were plum varieties of various genetic origin of the bioresource collection of the Institute. The assessment of resistance to spring frosts in the field was carried out in accordance with the "Program and methodology of variety study of fruit, berry and nut crops". In laboratory conditions, artificial freezing was carried out in the climate chamber Espec PSL-2KPH (Japan). The stability of generative organs of Prúnus doméstica, Prunus salicina and Prunus × rossica Erem. varieties was evaluated. in field and controlled conditions. Varieties of Prunus × rossica Erem. - Vetraz’, Gek, Zlato Skifov and Prunus salicina - Orlovskaya mechta, Skoroplodnaya, Suvenir Vostoka showed high stability of flowers and buds after the action of temperature -3 °C. The varieties Hungarian Zarechnaya, Stanley and Kuban Comet withstood a temperature of -3 °C with a proportion of dead buds of no more than 10 % and flowers of no more than 25 %. The data obtained under controlled conditions had a close correlation with the field assessment of damage to plum blossoms r = 0.75. The most resistant to spring frosts in the field and laboratory conditions are the varieties of plum Kubanskaya cometa, Skoroplodnaya and Orlovskaya mechta.
Zusammenfassung
Dieses Kapitel beschäftigt sich mit den klimatischen, ökologischen und sozioökonomischen treibenden Kräften, welche die Landnutzung in Österreich in der Vergangenheit und der Gegenwart maßgeblich bestimmt haben und die zukünftigen Entwicklungen beeinflussen werden. Es behandelt die in der Vergangenheit beobachteten und in der Zukunft erwarteten treibenden Kräfte von Landnutzungsänderungen in der Landwirtschaft (Abschn. 3.2), der Forstwirtschaft (Abschn. 3.3) und der Siedlungs- und Infrastrukturentwicklung (Abschn. 3.4). Abschließend werden die möglichen und erwarteten Auswirkungen dieser treibenden Kräfte auf die Bereitstellung der Ökosystemleistungen (ÖSL) beschrieben (Abschn. 3.5). Der Abbau von Mineralien wie Schotter oder Metalle wird aus Platzgründen nicht in diesem Kapitel behandelt, wenngleich es unumstritten ist, dass es sich auch dabei um landnutzungsrelevante Aktivitäten handelt. Kap. 3 unterscheidet zwischen natürlichen und anthropogenen Faktoren und wie sich diese auf die Landnutzung ausgewirkt haben und auswirken. Die sozioökonomischen Auswirkungen berücksichtigen dabei allerdings nicht die möglichen Anpassungs- oder Minderungsstrategien der einzelnen Sektoren, da diese in den Kap. 4 und 5 gesondert dargestellt werden.
Recent climate warming is reflected in the advanced onset of spring phenological phases of fruit trees and in so-called false springs. This then manifests as an increased risk of trees being damaged by late frosts in the sensitive growing stage. Based on the homogenised temperature series of 155 climatological stations divided into two altitudinal groups (below 300 m a.s.l. and 301–600 m a.s.l.), a climatological analysis of selected variables in relation to atmospheric circulation over the territory of the Czech Republic during the period 1961–2021 was performed. The number of frost days and the dates of their latest onset exhibited negative linear trends; however, only 16% and 20% were statistically significant. The onset of false spring (at least ten consecutive days with daily maximum ≥ 10 °C) was also characterised by decreasing trends, which significantly deepened after 1980. Spring frost days were particularly attributed to higher frequencies of anticyclonic circulation types such as the central anticyclone and circulation types with northeastern, eastern and southeastern airflow. False spring onset was particularly connected with the central anticyclone and circulation types with western and southwestern airflow. The increasing trends of frost risk days (days between the beginning of the false spring and the date of the latest frost with daily minimum < −1.5 °C) were statistically nonsignificant. Local series of fruit trees from southeastern Moravia proved to have significantly earlier onset of the first blossom and full blossoming phenophases. Although the damage by late frosts has been identified as an important factor contributing to low yields of fruit trees during the period 1996–2021 in the Czech Republic, other factors (e.g. other weather phenomena, diseases, pests, site, taking preventive measures against frost) must also be taken into account.
Historical sources report manifold on hazardous past climate and weather events that had considerable impacts on society. Studying changes in the occurrence or mechanisms behind such events is, however, hampered by a lack of spatially and temporally complete weather data. Especially, the spring season has received less attention in comparison to summer and winter, but is nevertheless relevant since weather conditions in spring can delay vegetation and create substantial damage due to for example late frost events. For Switzerland, we created a daily high-resolution (1x1 km2) reconstruction of temperature and precipitation fields from 1763 to 1960, that forms together with present-day meteorological fields a 258-year-long gridded data set. With this data set, we study changes in longer-term climate and historical weather events based on climate and phenological indices focusing on the spring season. Climate and phenological indices show few changes in the mean during the first 200 years, but climate change signals clearly emerge in all indices in the most recent period. We evaluate the climate and phenological indices for three cases of extreme spring weather conditions, an unusually warm spring, two late frost events, and three cold springs. Warm springs are much more frequent in the 21st century, but also in 1862 a very warm and early spring occurred. Spring temperatures, however, do not agree on how anomalously warm the spring was when comparing the Swiss reconstruction with reanalyses that extend back to 1868. The three springs of 1785, 1837, and 1853, were particularly cold with historical sources reporting for example prolonged lake freezing and abundant snowfall. Whereas the springs of 1837 and 1853 were characterized by cold and wet conditions, in the spring of 1785 wet-days were below average and, in particular, in the Swiss Plateau, frost days reached an all-time maximum. Such inversion conditions are confirmed by mostly north-easterly and high pressure weather types and historical sources describing prolonged Bise conditions. Studying such historical events is valuable since similar atmospheric conditions can also nowadays lead to cold springs affecting vegetation growth and agricultural production.
Frost stress is a major environmental factor that limits apricot growth in the warm temperate zone (WTZ) of China, and is always triggered by extreme low temperature weather processes. In this study, the characteristics of the apricot frost processes f(D, Tcum), which were identified from historical disaster representation, were analyzed and apricot frost evaluation indicators were developed, thus facilitating the process-based assessment and spatiotemporal analysis of apricot frost processes. Periods of low temperature that persist for 1~2, 3, and ≥4 days (i.e., duration days, D) provide the initial identification indicator for light, moderate, and severe apricot frost. The threshold ranges for Tcum are 0~3.9, 9.2~12.0, and >16.2 for D values of 1~2, 3, and ≥4, respectively. The northwest of the WTZ is dominated by apricot frost, with approximately 80% of apricot frost being light, followed by moderate and severe. Regional apricot frost exhibited a significant decreasing trend over the last four decades. A total of 29.65% of stations, which were mainly located in the northwest and middle parts of the study region, detected an increasing trend in apricot frost. The results provide technical support for targeted apricot frost level detection, and the process-based spatiotemporal characteristics of apricot frost can provide basic information for the prevention and mitigation of apricot frost.
In Switzerland, as elsewhere in the world, climate change is challenging viticulture. Knowledge of the potential impacts is essential for preparing adaptation measures. Two aspects directly impacted by increasing temperatures are the choice of grapevine varieties and the location of vineyards. To help address these impacts, we analysed future trends in two bioclimatic indices, average growing season temperature (GST) and Huglin’s heliothermal index (HI), in the Swiss canton of Neuchâtel. We conducted our analysis based on regional climate change scenarios referring to the emission pathways RCP4.5 and RCP8.5. Under the assumption of RCP8.5, trends in GST and HI indicate that the climate in this region will become too hot for most grapevine varieties currently cultivated, especially Pinot noir. Moreover, adaptation problems under RCP8.5 are expected to originate from an increase in climate extremes in both temperature and precipitation. Results based on RCP4.5 indicate a broader scope for adaptation, as the climate will remain suitable for a larger number of grapevine varieties within the current altitudinal limits of the Neuchâtel vineyards. In theory, an altitudinal shift of Pinot noir would also be possible under this emission pathway. In practice, however, the possibility of establishing vineyards above 600 m would be limited by the presence of protected forests and rocky areas. Our results highlight that vineyards in this region will need important adaptation measures if anthropic greenhouse gas emissions do not decrease rapidly and considerably, limiting the global temperature increase to < 1.5 °C.
We investigated how deciduous trees can adjust their freezing resistance in response to temperature during the progress of the ecodormancy phase, from midwinter to budburst.
We regularly sampled twigs of four different temperate deciduous tree species from January to the leaf‐out date. Using computer‐controlled freezers and climate chambers, the freezing resistance of buds was measured directly after sampling and also after the application of artificial hardening and dehardening treatments, simulating cold and warm spells. The thermal time to budburst in forcing conditions ( c . 20°C) was also quantified at each sampling as a proxy for dormancy depth.
Earlier flushing species showed higher freezing resistance than late flushing species at either similar bud development stage or similar dormancy depth. Overall, freezing resistance and its hardening and dehardening potential dramatically decreased during the progress of ecodormancy and became almost nil during budburst.
Our results suggest that extreme cold events in winter are not critical for trees, as freezing resistance can be largely enhanced during this period. By contrast, the timing of budburst is a critical component of tree fitness. Our results provide quantitative values of the freezing resistance dynamics during ecodormancy, particularly valuable in process‐based species distribution models.
Attempts at explaining range limits of temperate tree species still rest on correlations with climatic data that lack a physiological justification. Here, we present a synthesis of a multidisciplinary project that offers mechanistic explanations. Employing climatology, biogeography, dendrology, population and reproduction biology, stress physiology and phenology, we combine results from in situ elevational (Swiss Alps) and latitudinal (Alps vs. Scandinavia) comparisons, from reciprocal common garden and phytotron studies for eight European broadleaf tree species.
We show that unlike for low‐stature plants, tree canopy temperatures can be predicted from weather station data, and that low‐temperature extremes in winter do not explain range limits. At the current low‐temperature range limit, all species recruit well. Transplants revealed that the local environment rather than elevation of seed origin dominates growth and phenology. Tree ring width at the range limit is not related to season length, but to growing season temperature, with no evidence of carbon shortage. Bud break and leaf emergence in adults trees are timed in such a way that the probability of freezing damage is almost zero, with a uniform safety margin across elevations and taxa. More freezing‐resistant species flush earlier than less resistant species.
Synthesis : we conclude that the range limits of the examined tree species are set by the interactive influence of freezing resistance in spring, phenology settings, and the time required to mature tissue. Microevolution of spring phenology compromises between demands set by freezing resistance of young, immature tissue and season length requirements related to autumnal tissue maturation.
The responses of flowering phenology to temperature increases in temperate fruit trees have rarely been investigated in contrasting climatic regions. This is an appropriate framework for highlighting varying responses to diverse warming contexts, which would potentially combine chill accumulation (CA) declines and heat accumulation (HA) increases. To examine this issue, a data set was constituted in apple tree from flowering dates collected for two phenological stages of three cultivars in seven climate-contrasting temperate regions of Western Europe and in three mild regions, one in Northern Morocco and two in Southern Brazil. Multiple change-point models were applied to flowering date series, as well as to corresponding series of mean temperature during two successive periods, respectively determining for the fulfillment of chill and heat requirements. A new overview in space and time of flowering date changes was provided in apple tree highlighting not only flowering date advances as in previous studies but also stationary flowering date series. At global scale, differentiated flowering time patterns result from varying interactions between contrasting thermal determinisms of flowering dates and contrasting warming contexts. This may explain flowering date advances in most of European regions and in Morocco vs. stationary flowering date series in the Brazilian regions. A notable exception in Europe was found in the French Mediterranean region where the flowering date series was stationary. While the flowering duration series were stationary whatever the region, the flowering durations were far longer in mild regions compared to temperate regions. Our findings suggest a new warming vulnerability in temperate Mediterranean regions, which could shift toward responding more to chill decline and consequently experience late and extended flowering under future warming scenarios.
Within the same forest stand, temperate deciduous trees generally exhibit a distinct pattern in leaf-out timing, with some species flushing earlier than other species. This study aimed to explain the timing of leaf-out of various temperate tree species in relation to the risk of freezing damage to leaves.
We combined long-term series of leaf-out date (14–32 years) of five temperate tree species located in both low and high elevations in Switzerland, daily minimum temperatures recorded on the same sites and species-specific freezing resistance (LT50) of emerging leaves. We calculated temperature safety margins (the temperature difference between absolute minimum temperature during leaf-out and species-specific LT50 values), and date safety margins (time lag between the last day when temperature falls below species-specific LT50 values and the date of leaf-out).
The timing of leaf-out occurred when the probability to encounter freezing damage approaches zero, irrespective of climatic conditions (low vs. high elevation) and species (early and late flushing species). In other words, trees leaf-out precisely at the beginning of the probabilistically safe period. Interestingly, the temperature safety margins did not differ significantly between low and high elevation. Yet, the date safety margin was smaller at high elevation, presumably due to a faster increase of temperature during the leaf-out period at high elevation.
When species-specific freezing resistance is taken into account, the time of leaf-out converges among species towards a marginal risk of freezing damage. Thus, leaf-out time has likely evolved in a way that the risk of freezing damage is minimized over a large spectrum of climatic conditions. Species with a small safety margin against freezing temperature, like Fagus sylvatica, appear to employ photoperiod co-control of spring phenology, whereas species with a large safety margin depend largely on temperature for the right timing of leaf-out.
Our results offer a new avenue to explain the differences in leaf-out timing among co-occurring tree species. They further suggest that in a warming climate, tree species can expand their distribution range to the extent their phenology matches the stochasticity of freezing temperatures in spring.
A mathematical model relating environmental temperatures to rest completion of 2 peach cultivars has been developed. The model equates temperatures to effective chill-units, such that, one can predict when rest will or has been completed with a high degree of accuracy.
Earlier spring leaf unfolding is a frequently observed response of plants to climate warming. Many deciduous tree species require chilling for dormancy release, and warming-related reductions in chilling may counteract the advance of leaf unfolding in response to warming. Empirical evidence for this, however, is limited to saplings or twigs in climate-controlled chambers. Using long-term in situ observations of leaf unfolding for seven dominant European tree species at 1,245 sites, here we show that the apparent response of leaf unfolding to climate warming (ST, expressed in days advance of leaf unfolding per °C warming) has significantly decreased from 1980 to 2013 in all monitored tree species. Averaged across all species and sites, ST decreased by 40% from 4.0 ± 1.8 days °C(-1) during 1980-1994 to 2.3 ± 1.6 days °C(-1) during 1999-2013. The declining ST was also simulated by chilling-based phenology models, albeit with a weaker decline (24-30%) than observed in situ. The reduction in ST is likely to be partly attributable to reduced chilling. Nonetheless, other mechanisms may also have a role, such as 'photoperiod limitation' mechanisms that may become ultimately limiting when leaf unfolding dates occur too early in the season. Our results provide empirical evidence for a declining ST, but also suggest that the predicted strong winter warming in the future may further reduce ST and therefore result in a slowdown in the advance of tree spring phenology.
While the rise in global mean temperature over the past several decades is now widely acknowledged, the issue as to whether and to what extent temperature variability is changing continues to undergo debate. Here, variability refers to the spread of the temperature distribution. Much attention has been given to the effects that changes in mean temperature have on extremes, but these changes are accompanied by changes in variability, and it is actually the two together, in addition to all aspects of a changing climate pattern, that influence extremes. Since extremes have some of the largest impacts on society and ecology, changing temperature variability must be considered in tandem with a gradually increasing temperature mean. Previous studies of trends in temperature variability have produced conflicting results. Here we investigated ten long-term instrumental records in Europe of minimum, mean and maximum temperatures, looking for trends in seasonal, annual and decadal measures of variability (standard deviation and various quantile ranges) as well as asymmetries in the trends of extreme versus mean temperatures via quantile regression. We found consistent and accelerating mean warming during 1864–2012. In the last 40 years (1973–2012) trends for Tmax were higher than for Tmin, reaching up to 0.8 °C per 10a in spring. On the other hand, variability trends were not as uniform: significant changes occurred in opposing directions depending on the season, as well as when comparing 1864–2012 trends to those of 1973–2012. Moreover, if variability changed, then it changed asymmetrically, that is only in the part above or below the median. Consequently, trends in the extreme high and low quantiles differed. Regional differences indicated that in winter, high-alpine stations had increasing variability trends for Tmax especially at the upper tail compared to no changes or decreasing variability at low altitude stations. In contrast, summer variability increased at all stations studied.
The rise in spring temperatures over the past half-century has led to advances in the phenology of many nontropical plants and animals. As species and populations differ in their phenological responses to temperature, an increase in temperatures has the potential to alter timing-dependent species interactions. One species-interaction that may be affected is the competition for light in deciduous forests, where early vernal species have a narrow window of opportunity for growth before late spring species cast shade. Here we consider the Marsham phenology time series of first leafing dates of thirteen tree species and flowering dates of one ground flora species, which spans two centuries. The exceptional length of this time series permits a rare comparison of the statistical support for parameter-rich regression and mechanistic thermal sensitivity phenology models. While mechanistic models perform best in the majority of cases, both they and the regression models provide remarkably consistent insights into the relative sensitivity of each species to forcing and chilling effects. All species are sensitive to spring forcing, but we also find that vernal and northern European species are responsive to cold temperatures in the previous autumn. Whether this sensitivity reflects a chilling requirement or a delaying of dormancy remains to be tested. We then apply the models to projected future temperature data under a fossil fuel intensive emissions scenario and predict that while some species will advance substantially others will advance by less and may even be delayed due to a rise in autumn and winter temperatures. Considering the projected responses of all fourteen species, we anticipate a change in the order of spring events, which may lead to changes in competitive advantage for light with potential implications for the composition of temperate forests.
© 2015 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.
Temperate climates are defined by distinct temperature seasonality with large and often unpredictable weather during any of the four seasons. To thrive in such climates, trees have to withstand a cold winter and the stochastic occurrence of freeze events during any time of the year. The physiological mechanisms trees adopt to escape, avoid, and tolerate freezing temperatures include a cold acclimation in autumn, a dormancy period during winter (leafless in deciduous trees), and the maintenance of a certain freezing tolerance during dehardening in early spring. The change from one phase to the next is mediated by complex interactions between temperature and photoperiod. This review aims at providing an overview of the interplay between phenology of leaves and species-specific freezing resistance. First, we address the long-term evolutionary responses that enabled temperate trees to tolerate certain low temperature extremes. We provide evidence that short term acclimation of freezing resistance plays a crucial role both in dormant and active buds, including re-acclimation to cold conditions following warm spells. This ability declines to almost zero during leaf emergence. Second, we show that the risk that native temperate trees encounter freeze injuries is low and is confined to spring and underline that this risk might be altered by climate warming depending on species-specific phenological responses to environmental cues.
Spring phenology of temperate forest trees is optimized to maximize the length of the growing season while minimizing the risk of freezing damage. The release from winter dormancy is environmentally mediated by species-specific responses to temperature and photoperiod. We investigated the response of early spring phenology to temperature and photoperiod at different stages of dormancy release in cuttings from four temperate tree species in controlled environments. By tracking bud development, we were able to identify the onset of bud swelling and bud growth in Acer pseudoplatanus L., Fagus sylvatica L., Quercus petraea (Mattuschka) Liebl. and Picea abies (L.) H. Karst. At a given early stage of dormancy release, the onset and duration of the bud swelling prior to bud burst are driven by concurrent temperature and photoperiod, while the maximum growth rate is temperature dependent only, except for Fagus, where long photoperiods also increased bud growth rates. Similarly, the later bud burst was controlled by temperature and photoperiod (in the photoperiod sensitive species Fagus, Quercus and Picea). We conclude that photoperiod is involved in the release of dormancy during the ecodormancy phase and may influence bud burst in trees that have experienced sufficient chilling. This study explored and documented the early bud swelling period that precedes and defines later phenological stages such as canopy greening in conventional phenological works. It is the early bud growth resumption that needs to be understood in order to arrive at a causal interpretation and modelling of tree phenology at a large scale. Classic spring phenology events mark visible endpoints of a cascade of processes as evidenced here.
In temperate climates, seedlings and saplings have often been assumed to be more sensitive to late‐spring freezes than conspecific adult trees. Yet, no data are available to compare the freezing resistance of juvenile and adult trees at their phenologically most sensitive stage, that is, during leaf‐out.
Emerging leaves of seedlings, saplings and adult trees were collected in spring 2013 in seven temperate tree species in a mature mixed forest in the foothills of the Swiss Jura Mountains. Freezing resistance of these emerging leaves was assessed using different target temperatures (−13 to +4 °C) in seven computer‐controlled freezers. Additionally, we assessed the risk that species encounter freeze damages based on temperature data recorded since 1898.
The different study species showed contrasting freezing resistance, with the LT 50 (median lethal freezing temperature) of emerging leaves ranging from −3.5 ± 0.2 °C ( Fraxinus excelsior ) to −8.3 ± 0.2 °C ( Prunus avium ). Within species, juvenile trees (seedlings or saplings) were found to be as sensitive to freezing temperatures as mature trees when the same developmental stage of foliage was compared. Based on phenological observations made during spring 2012, long time series of temperatures indicate a very low risk of freeze damage at the study site, especially for adult trees.
Synthesis . We conclude that seedlings and saplings are more prone to freeze damage than adult trees because of their earlier flushing rather than due to a higher sensitivity to freezing as such. Our study highlights that the timing of spring phenology has evolved in such a way that it minimizes the risk of freeze damage according to the species‐specific LT 50 . Early flushing species are among the most freezing‐resistant species during flushing, whereas late flushing species are among the least resistant. We conclude that for the examined species the species‐specific freezing resistance during leaf emergence could be extracted from either adult or juvenile trees, as long as it is estimated at a same phenological stage.
Knowledge of the spatial variation in temperature in wine regions provides the basis for evaluating the general suitability for viticulture, allows for comparisons between wine regions, and offers growers a measure of assessing appropriate cultivars and sites. However, while tremendous advances have occurred in spatial climate data products, these have not been used to examine climate and suitability for viticulture in the western United States. This research spatially maps the climate in American Viticultural Areas (AVAs) throughout California, Oregon, Washington, and Idaho using the 1971-2000 PRISM 400 m resolution climate grids, assessing the statistical properties of four climate indices used to characterize suitability for viticulture: growing degree-days (GDD, or Winkler index, WI), the Huglin index (HI), the biologically effective degree-day index (BEDD), and average growing season temperatures (GST). The results show that the spatial variability of climate within AVAs can be significant, with some regions representing as many as five climate classes suitable for viticulture. Compared to static climate station data, documenting the spatial distribution of climate provides a more holistic measure of understanding the range of cultivar suitability within AVAs. Furthermore, results reveal that GST and GDD are functionally identical but that GST is easier to calculate and overcomes many methodological issues that occur with GDD. The HI and BEDD indices capture the known AVA-wide suitability but need to be further validated in the western U.S. Additionally, the research underscores the necessity for researchers, software developers, and others to clearly communicate the data time period and method of calculating GDD so that results can be correctly interpreted and compared.
With global warming, an advance in spring leaf phenology has been reported worldwide. However, it is difficult to forecast phenology for a given species, due to a lack of knowledge about chilling requirements. We quantified chilling and heat requirements for leaf unfolding in two European tree species and investigated their relative contributions to phenological variations between and within populations. We used an extensive database containing information about the leaf phenology of 14 oak and 10 beech populations monitored over elevation gradients since 2005. In parallel, we studied the various bud dormancy phases, in controlled conditions, by regularly sampling low- and high-elevation populations during fall and winter. Oak was 2.3 times more sensitive to temperature for leaf unfolding over the elevation gradient and had a lower chilling requirement for dormancy release than beech. We found that chilling is currently insufficient for the full release of dormancy, for both species, at the lowest elevations in the area studied. Genetic variation in leaf unfolding timing between and within oak populations was probably due to differences in heat requirement rather than differences in chilling requirement. Our results demonstrate the importance of chilling for leaf unfolding in forest trees and indicate that the advance in leaf unfolding phenology with increasing temperature will probably be less pronounced than forecasted. This highlights the urgent need to determine experimentally the interactions between chilling and heat requirements in forest tree species, to improve our understanding and modeling of changes in phenological timing under global warming.
Temperature data over the past five decades show faster warming of the global land surface during the night than during the day. This asymmetric warming is expected to affect carbon assimilation and consumption in plants, because photosynthesis in most plants occurs during daytime and is more sensitive to the maximum daily temperature, Tmax, whereas plant respiration occurs throughout the day and is therefore influenced by both Tmax and the minimum daily temperature, Tmin. Most studies of the response of terrestrial ecosystems to climate warming, however, ignore this asymmetric forcing effect on vegetation growth and carbon dioxide (CO2) fluxes. Here we analyse the interannual covariations of the satellite-derived normalized difference vegetation index (NDVI, an indicator of vegetation greenness) with Tmax and Tmin over the Northern Hemisphere. After removing the correlation between Tmax and Tmin, we find that the partial correlation between Tmax and NDVI is positive in most wet and cool ecosystems over boreal regions, but negative in dry temperate regions. In contrast, the partial correlation between Tmin and NDVI is negative in boreal regions, and exhibits a more complex behaviour in dry temperate regions. We detect similar patterns in terrestrial net CO2 exchange maps obtained from a global atmospheric inversion model. Additional analysis of the long-term atmospheric CO2 concentration record of the station Point Barrow in Alaska suggests that the peak-to-peak amplitude of CO2 increased by 23 ± 11% for a +1 °C anomaly in Tmax from May to September over lands north of 51° N, but decreased by 28 ± 14% for a +1 °C anomaly in Tmin. These lines of evidence suggest that asymmetric diurnal warming, a process that is currently not taken into account in many global carbon cycle models, leads to a divergent response of Northern Hemisphere vegetation growth and carbon sequestration to rising temperatures.
Minimum temperature is assumed to be an important driver of tree species range limits. We investigated during which period of the year trees are most vulnerable to freezing damage and whether the pressure of freezing events increases with increasing elevation.
We assessed the course of freezing resistance of buds and leaves from winter to summer at the upper elevational limits of eight deciduous tree species in the S wiss A lps. By reconstructing the spring phenology of these species over the last eight decades using a thermal time model, we linked freezing resistance with long‐term minimum temperature data along elevational gradients.
Counter‐intuitively, the pressure of freeze events does not increase with elevation, but deciduous temperate tree species exhibit a constant safety margin (5–8.5 K) against damage by spring freeze events along elevational gradients, as a result of the later flushing at higher elevation. Absolute minimum temperatures in winter and summer are unlikely to critically injure trees.
Our study shows that freezing temperatures in spring are the main selective pressure controlling the timing of flushing, leading to a shorter growing season at higher elevation and potentially driving species distribution limits. Such mechanistic knowledge is important to improve predictions of tree species range limits.
Background: Temperature directly affects xylogenesis at high-elevation treelines. The low-temperature limitation of meristematic processes is thus key to understand treeline formation.
Aims: We aimed to experimentally test in situ the direct low-temperature effect on wood tissue formation at the alpine treeline.
Methods: We applied controlled Peltier-mediated cooling and warming (±3 K) to branch segments in Pinus uncinata at the treeline in the Swiss Alps. In addition, we studied xylogenesis in untreated trees during the growing season by sequential micro-coring.
Results: Micro-cores indicated that the cambial zone was fully developed by the time the cooling and warming treatment started, shortly after snowmelt. Presumably, because of this, experimental cooling of branches did not significantly reduce the number of cells produced per season. Warming extended the formation of early wood into the late season, and thus reduced the fraction of late wood.
Conclusions: We conclude that temperatures very early in the season determine the width of the cambial zone which, in turn, strongly controls the number of tracheids produced during the remaining growing season. Temperatures later in the season mainly determine the early wood to late wood ratio. These data provide an empirical basis for the mechanistic understanding of tree growth at the treeline in response to temperature.
A considerable number of studies have investigated the phenology of European beech using models, experimental controlled conditions, or descriptive surveys of patterns in situ. In spite of this interest, there is no consensus about the environmental factors controlling bud burst in beech, especially about the role of photoperiod and chilling temperature (cold temperature effective to release bud dormancy). However, recent experimental and modelling studies provide new insights into the means by which these environmental factors control beech phenology. This present contribution aims to reconcile contradictory hypotheses about the main environmental factors controlling bud burst date of European beech. First, we review the main published results on the environmental control of beech phenology both in controlled and in natural conditions. Second, supported by the findings of recent studies, we propose a new theory for the role of photoperiod during the chilling phase for explaining spatial and temporal variations in bud burst phenology of European beech. Examples using long-term data from the Swiss Alps and Germany are presented to support this theory. The possible impacts of future and ongoing climate warming on beech phenology are discussed. Finally, due to interactions between chilling, forcing temperature, and photoperiod, we assert that beech phenology follows a nonlinear trend across biogeographical gradients such as changes in elevation or latitude and that the bud burst date of beech is expected not to undergo significant changes in response to global warming, especially in warmer climates.
Monthly mean maximum and minimum temperatures for over 50% (10%) of the
Northern (Southern) Hemisphere landmass, accounting for 37% of the
global landmass, indicate that the rise of the minimum temperature has
occurred at a rate three times that of the maximum temperature during
the period 1951-90 (0.84°C versus 0.28°C). The decrease of the
diurnal temperature range is approximately equal to the increase of mean
temperature. The asymmetry is detectable in all seasons and in most of
the regions studied.The decrease in the daily temperature range is
partially related to increases in cloud cover. Furthermore, a large
number of atmospheric and surface boundary conditions are shown to
differentially affect the maximum and minimum temperature. Linkages of
the observed changes in the diurnal temperature range to large-scale
climate forcings, such as anthropogenic increases in sulfate aerosols,
greenhouse gases, or biomass burning (smoke), remain tentative.
Nonetheless, the observed decrease of the diurnal temperature range is
clearly important, both scientifically and practically.
Phenological events, such as the initiation and the end of seasonal growth, are thought to be under strong evolutionary control because of their influence on tree fitness. Although numerous studies highlighted genetic differentiation in phenology among populations from contrasting climates, it remains unclear whether local adaptation could restrict phenological plasticity in response to current warming. Seedling populations of seven deciduous tree species from high and low elevations in the Swiss Alps were investigated in eight common gardens located along two elevational gradients from 400 to 1,700 m. We addressed the following questions: are there genetic differentiations in phenology between populations from low and high elevations, and are populations from the upper elevational limit of a species' distribution able to respond to increasing temperature to the same extent as low-elevation populations? Genetic variation of leaf unfolding date between seedlings from low and high populations was detected in six out of seven tree species. Except for beech, populations from high elevations tended to flush later than populations from low elevations, emphasizing that phenology is likely to be under evolutionary pressure. Furthermore, seedlings from high elevation exhibited lower phenological plasticity to temperature than low-elevation provenances. This difference in phenological plasticity may reflect the opposing selective forces involved (i.e. a trade-off between maximizing growing season length and avoiding frost damages). Nevertheless, environmental effects were much stronger than genetic effects, suggesting a high phenological plasticity to enable tree populations to track ongoing climate change, which includes the risk of tracking unusually warm springs followed by frost.
The aim of the study was to determine whether there are genetic variations in growth and leaf phenology (flushing and senescence) among populations of six woody species (Abies alba Mill., Acer pseudoplatanus L., Fagus sylvatica L., Fraxinus excelsior L., Ilex aquifolium L., and Quercus petraea (Matt.) Liebl.) along altitudinal gradients, using a common-garden experiment. We found (i) significant differences in phenology and growth among provenances for most species and (ii) evidence that these among-population differences in phenology were related to the annual temperature at the provenance sites for ash, beech, and oak. It is noteworthy that along the same climatic gradient, species can exhibit opposing genetic clines: beech populations from high elevations flushed earlier than those from low elevations, whereas we observed the opposite trend for ash and oak. For most species, significant altitudinal clines for growth were also revealed. Finally, we highlighted the fact that both phenology timing and growth rate were highly consistent from year to year. The results demonstrated that despite the proximity of the populations in their natural area, differences in altitude led to genetic differentiation in their phenology and growth. These adaptive capacities acting along a natural climatic gradient could allow populations to cope with current climate change.
Phenology reflects the interplay of climate and biological development. Early spring phenological phenomena are particularly important because the end of diapause or dormancy is related not only to heat accumulation in the early spring but also probably to winter low temperatures. Although a warmer winter can reduce overwintering mortality in many insects and plants, it also reduces the accumulation of chilling time that often triggers the end of diapause or dormancy. We examined a continuous 67-year time series of the first flowering date of cherry trees and compared three phenological models based on the temperature-dependent developmental rate: (i) the accumulated degree days (ADD) method, (ii) the number of days transferred to a standardized temperature (DTS) method, and (iii) the accumulated developmental progress (ADP) method. The ADP method performed the best but only slightly better than the DTS method. We further explained the residuals from the ADP method by an additive model using the mean winter minimum daily temperatures, the number of days with low temperatures (represented by daily minimum temperature) below a critical low temperature, and the minimum annual extreme temperature. These three temperature variables explained more than 57.5% deviance of the ADP model residuals. Increased mean winter low temperatures can delay the blooming of cherry trees by reducing the accumulation of chilling time, whereas reduced numbers of cold days can shift the blooming to become earlier. Overall, rising winter low temperatures will delay the flowering time, while rising early spring temperatures directly shift earlier the flowering time. The flowering time has been shifted to earlier, and the balance from the opposing effects of rising winter low temperatures and early spring temperatures explains this shift.
This study presents the first evaluation of apple flowering phenology models using data from 14 sites across the globe. The dataset includes large variability in growing climates, a prerequisite to investigate phenology models for use in climate change applications. Two flowering stages, early and full, were investigated allowing for unique model evaluation based on both statistical performance and biological assumptions. Two overarching phenology models (Sequential and Chill Overlap) and two sub-models of chill (Dynamic and Triangular) and heat (GDH and Sigmoidal) were tested. Flowering times from the different sites illustrated the differing effects of contrasting winter and spring temperatures. Sites with similar springtime temperatures, but different winter temperatures, had different flowering patterns (warmer winter sites flowered later). Across all analyses, results from the Chill Overlap model were better than those from the Sequential model. Of the Chill Overlap models, those fitted with the Triangular or Dynamic chill model and the GDH heat sub-model performed well statistically and met the assumptions of the model across both flowering stages. The mild sites in the analysis were least well represented, regardless of model selection. This global evaluation demonstrated that flowering modelling in temperate fruit trees would progress through appropriate choices of overarching model, sub-models and parameters.
The timing of foliar budburst is an important component of the fitness of trees. Adaptation of budburst to local temperatures and phenotypic plasticity in the date of budburst to changes in temperature can therefore be expected. In this study, we analysed provenance trials of European beech (Fagus sylvatica L.) established over a wide geographic and climatic range in Europe. The analysis was based on a phenological model that represents the key processes at budburst phenology of temperate- and boreal zone deciduous trees. We conclude that adaptive differences exist between provenances in the critical chilling- and forcing requirements triggering budburst. Moreover, it is likely that these provenances show a plastic response to local environmental conditions for these two factors. Chilling- and forcing temperature requirements are key traits determining a tree’s response of the date of foliar budburst to temperature. We infer from our results that trees would be able to adjust this response when climatic conditions change. Implications for climate change assessment studies and suggestions to incorporate this second order phenotypic plasticity in phenological models are discussed.
Tree mortality as a crucial element of natural forest dynamics is still a poorly understood process. Abrupt growth decreases are known to occur several years or decades before complete cessation of growth. Hence, identifying and linking these growth decreases to potential inciting factors such as drought and frost will improve our understanding of mortality processes. We analyzed nine Central European tree species including six coniferous species (Abies alba, Picea abies, Larix decidua, Pinus sylvestris, Pinus cembra, Pinus montana) and three broadleaved species (Fagus sylvatica, Quercus spp., Acer pseudoplatanus). Tree-ring data from 848 standing dead trees from 14 forest reserves all over Switzerland were sampled. We applied distributed lag non-linear models to relate abrupt growth decreases to drought and frost. The results indicate for many species that both drought and frost have a moderate to major impact on abrupt growth decreases prior to tree death. While late frost in spring may instantaneously result in sustained abrupt growth decreases in most species except Scots pine and mountain pine, severe drought over several months in spring may either show an immediate negative impact on growth, such as in beech, or feature negative reactions that are lagged by several years, such as in oak and Scots pine. Thus, extreme climatic conditions have an essential influence on abrupt growth decreases that finally result in tree death, although variability of the reactions within and among species is high.
The phenology of spring leaf unfolding plays a key role in the structure and functioning of ecosystems. The classical concept of heat requirement (growing degree days) for leaf unfolding was developed hundreds of years ago, but this model does not include the recently reported greater importance of daytime than night‐time temperature.
A manipulative experiment on daytime vs night‐time warming with saplings of three species of temperate deciduous trees was conducted and a Bayesian method was applied to explore the different effects of daytime and night‐time temperatures on spring phenology.
We found that both daytime and night‐time warming significantly advanced leaf unfolding, but the sensitivities to increased daytime and night‐time temperatures differed significantly. Trees were most sensitive to daytime warming (7.4 ± 0.9, 4.8 ± 0.3 and 4.8 ± 0.2 d advancement per degree Celsius warming (d °C ⁻¹ ) for birch, oak and beech, respectively) and least sensitive to night‐time warming (5.5 ± 0.9, 3.3 ± 0.3 and 2.1 ± 0.9 d °C ⁻¹ ). Interestingly, a Bayesian analysis found that the impact of daytime temperature on leaf unfolding was approximately three times higher than that of night‐time temperatures.
Night‐time global temperature is increasing faster than daytime temperature, so model projections of future spring phenology should incorporate the effects of these different temperatures.
The onset of the growing season of trees has been earlier by 2.3 days/decade during the last 40 years in temperate Europe because of global warming. The effect of temperature on plant phenology is however not linear because temperature has a dual effect on bud development. On one hand, low temperatures are necessary to break bud endodormancy, and on the other hand higher temperatures are necessary to promote bud cell growth afterwards. Different process-based models have been developed in the last decades to predict the date of budbreak of woody species. They predict that global warming should delay or compromise endodormancy break at the species equatorward range limits leading to a delay or even impossibility to flower or set new leaves. These models are classically parameterized with flowering or budbreak dates only, with no information on the endodormancy break date because this information is very scarce. Here we evaluated the efficiency of a set of phenological models to accurately predict the endodormancy break dates of three fruit trees. Our results show that models calibrated solely with budbreak dates usually do not accurately predict the endodormancy break date. Providing endodormancy break date for the model parameterization results in much more accurate prediction of this latter, with however a higher error than that on budbreak dates. Most importantly, we show that models not calibrated with endodormancy break dates can generate large discrepancies in forecasted budbreak dates when using climate scenarios as compared to models calibrated with endodormancy break dates. This discrepancy increases with mean annual temperature and is therefore the strongest after 2050 in the southernmost regions. Our results claim for the urgent need of massive measurements of endodormancy break dates in forest and fruit trees to yield more robust projections of phenological changes in a near future. This article is protected by copyright. All rights reserved.
The hypothetico-deductive modelling framework introduced in Chap. 2 is applied to examining the effects of climatic change on the annual cycle of boreal and temperate trees. Most emphasis is devoted to the paradoxical hypothesis that climatic warming will increase the incidence of frost damage in these trees. According to early computer simulations, trees in boreal conditions in particular would deharden and even start to grow during such mild spells in winter as are commonly projected to prevail in the future climate, so that serious damage would result during subsequent periods of frost. Empirical tests of the frost damage hypothesis suggest that the catastrophic frost damage projected in the early computer simulations will not be realised. Even so, the frost damage hypothesis cannot be ruled out. Available experimental evidence remains limited, and theoretical work with computer simulations has shown that relatively small changes in the ecophysiological traits of trees may cause premature dehardening and growth onset during mild spells in the scenario climate. There have also been several reports of considerable frost damage to boreal and temperate trees and other plants in natural conditions after unseasonally warm spells in winter even in the present climate. For these reasons, nothing conclusive can be said about the frost damage hypothesis. However, the research discussed in this and other chapters of the present volume has pointed out not only the ecophysiological traits of the trees that are critical for the frost damage hypothesis but also the experimental designs that facilitate the determining of those traits in any tree population. Overall, the importance of ecophysiological realism and continuous critical testing of the models are emphasised. Finally, the implications of the effects of climatic change on tree seasonality to the stand and ecosystem level are briefly discussed.
In the current context of global warming, an analysis is required of spatially-extensive and long-term blooming data in fruit trees to make up for insufficient information on regional-scale blooming changes and determinisms that are key to the phenological adaptation of these species. We therefore analysed blooming dates over long periods at climate-contrasted sites in Western Europe, focusing mainly on the Golden Delicious apple that is grown worldwide. On average, blooming advances were more pronounced in northern continental (10 days) than in western oceanic (6–7 days) regions, while the shortest advance was found on the Mediterranean coastline. Temporal trends toward blooming phase shortenings were also observed in continental regions. These regional differences in temporal variability across Western Europe resulted in a decrease in spatial variability, i.e. shorter time intervals between blooming dates in contrasted regions (8–10-day decrease for full bloom between Mediterranean and continental regions). Fitted sequential models were used to reproduce phenological changes. Marked trends toward shorter simulated durations of forcing period (bud growth from dormancy release to blooming) and high positive correlations between these durations and observed blooming dates support the notion that blooming advances and shortenings are mainly due to faster satisfaction of the heating requirement. However, trends toward later dormancy releases were also noted in oceanic and Mediterranean regions. This could tend toward blooming delays and explain the shorter advances in these regions despite similar or greater warming. The regional differences in simulated chilling and forcing periods were consistent with the regional differences in temperature increases.
Evaluation of endodormancy release models in temperate fruit tree species has generally been indirect, as a component of the global evaluation of bud breakdate models that include an endodormancy release module. Due to the lack of data, their direct evaluation based on the knowledge of the dynamics of bud dormancy states has been very succinct. Consequently, these models have not been optimized, except for the 'amount of chill units required to break endodormancy' taken as the genotype specific parameter. As part of different studies on bud state during the rest period, near 30 yearly dynamics of the dormancy state of 'Redhaven' peach vegetative buds under natural conditions have been recorded, based on the biological 'one node cuttings' test under standard conditions (25°C). These data were used to optimize classic models (Weinberger-W; Utah-U, etc.) of endodormancy release in fruit tree species with temperature as the only input variable, in order to compare their goodness of fit and their predictive capacity. The fitted parameters were the 'amount of chill units required to break endodormancy', those of the temperature functions f(T) describing the rate of endodormancy development and, when relevant, the starting date of endodormancy release. The results and practical conclusions for predicting dormancy release date are presented. The optimization method used was the minimization of the mean square error (MSE) between the observed (biological test) and the computed dates of endodormancy release and was carried out using the nls module of R software. As main results: the optimization of the W model resulted in an increase of the standard threshold temperature; the endodormancy release effect of negative temperatures (up to freezing injury) in the optimized form of U model that was not taken into account in the standard form; the sharp transition from positive to negative f(T) values for the temperatures above 12°C, in the optimized U model; and the fact that the model of Weinberger is a particular form of smoothed Utah model.
1. To evaluate the impacts of climate change on the primary production of temperate deciduous tree species, the onset and cessation of the growth must be accurately described. The aim of this study is to find a model which predicts the onset of growth of Fagus sylvatica (European beech) accurately. 2. Several models have been proposed for the prediction of the timing of budburst of woody plants. Most of these models have been evaluated for species other than Fagus sylvatica, and in some cases for flower buds. Six models were fitted to data on leaf unfolding of Fagus sylvatica, collected in the Netherlands over 57 years (1901-68). 3. All models require only temperature as input. For Fagus sylvatica, however, photoperiod may influence the timing of the onset of growth. Therefore, photosensitivity was incorporated in these models. This reduced the predictive power compared to models that do not incorporate photosensitivity. 4. The model proposed by Sarvas (1974), in which the development of rest and quiescence is strictly separated in time, resulted in the best predictions of the average date of leaf unfolding in Fagus sylvatica.
(1) The dates of budhurst of lateral shoots on 2- to 10-year old trees of Picea sitchensis were recorded on fourteen occasions at sites near meteorological stations in lowland and upland Britain between 1960 and 1980. (2) The following relationship accounted for 92% of the variation in thermal time from 1 February to the date of budburst among the fourteen observations: thermal time = 67.4 + 4401.8 exp (-0.042 x chill days) where thermal time was day degrees >5 ⚬C accumulated from 1 February, and chill days were the number of days ⩽5 ⚬C counted from 1 November, both based on mean daily air temperature ((max. + min.)/2). This model may be used to estimate the date of budburst on young P. sitchensis of most provenances growing in upland Britain. (3) The following features or assumptions of the model were examined with reference to the literature and/or by experimentation: the small effect of provenance; linearity in the relationship between bud growth rate and temperature; the large effect of chilling on thermal time to budhurst; the omission of daylength and soil temperature as variables; the choice of starting dates for effective chilling and thermal time; and the use of simple fixed base temperatures. (4) The model was applied to mean daily temperatures at Eskdalemuir for the period 1912-82. The predicted dates of budburst ranged from 23 April in 1961 to 30 May in 1923, with a mean date of 12 May.
This study was carried out in three geographically contrasting countries of the Mediterranean region. Itaims to understand the impact of climate change, particularly the temperature increases, on phenologicalstage of three taxonomically different species (early and late-spring-flowering species). Three species,namely olive (Olea europaea), apple (Malus domestica Borkh.) and almond (Prunus dulcis (Mill.)) wereinvestigated to highlight the phenological behavior of one species at different locations and differentspecies at one location. Climatic and phenological data were collected from Morocco, France and Italyover the last 40 years. Analysis of data on temperature showed a strong warming in the northern locations(coldest areas), particularly in Nîmes, compared to the southern ones (warmer locations) during theperiod October to May. The marked spring warming in all locations since the end of 1980s in France(the beginning of 1990s in Italy and Morocco) resulted in blooming earliness, with regional patterns interms of impact. The late-spring-flowering species (olive and apple) showed a remarkable sensitivity tocontinuous warming in different areas. No flowering earliness was observed in early-spring-floweringspecies (almond), due to the stability of mean temperature during February. Thus, a strong control ofmean temperature during the forcing period on flowering earliness of apple was found in all areas.Physiological processes (dormancy and dormancy release) of trees during the dormant and growth periodexplain, in part, the regional differences observed in flowering dates among sites and species. Overall, thepronounced warming in the southern France reflects a relative trend toward aridity of climate at this site,and consequently some vulnerability of fruit trees. As result, the process of flowering in a high latitudelocations (northern areas) in the future can be represented by that in a low latitude locations at present(southern areas), particularly for apple.
AimAlthough numerous studies have reported advanced Northern Hemisphere spring phenology since the 1980s, recent studies based on remote sensing have reported a reversal or deceleration of this trend. This study aimed (1) to fully understand recent spring phenology shifts using both in situ observations and satellite-based normalized difference vegetation index (NDVI) datasets, and (2) to test whether the NDVI methods capture the trends observed in situ.LocationWestern Central Europe.Methods
Temporal spring phenology trends (leaf unfolding dates) were examined using 1,001,678 in situ observations of 31 plant species at 3984 stations, as well as NDVI-based start-of-season dates, obtained using five different methods, across the pixels that included the phenology stations.ResultsIn situ and NDVI observations both indicated that spring phenology significantly advanced during the period 1982–2011 at an average rate of −0.45 days yr−1. This trend was not uniform across the period and significantly weakened over the period 2000–2011. Furthermore, opposite trends were found between in situ and NDVI observations over the period 2000–2011. Averaged over all species, the in situ observations indicated a slower but still advancing trend for leaf unfolding, whereas the NDVI series showed a delayed spring phenology.Main conclusionsThe recent trend reversal in the advancement of spring phenology in western Central Europe is likely to be related to the response of early spring species to the cooling trend in late winter. In contrast, late spring species continued to exhibit advanced leaf unfolding, which is consistent with the warming trend during spring months. Because remote sensing does not distinguish between species, the signal of growing-season onset may only reflect the phenological dynamics of these earliest species in the pixel, even though most species still exhibit advancing trends.
The effects that below-freezing temperature (frost) can have at times of year when it is unusual are an interesting ecological phenomenon that has received little attention. The physiological consequence of formation of ice crystals in plant tissue is often death of the plants, or at least of sensitive parts that can include flower buds, ovaries, and leaves. The loss of potential for sexual reproduction can have long-lasting effects on the demography of annuals and long-lived perennials, because the short-term negative effects of frosts can result in longer-term benefits through lowered populations of seed predators. The loss of host plants can have dramatic consequences for herbivores, even causing local extinctions, and the loss of just flowers can also affect populations of seed predators and their parasitoids. Frosts can cause local extinctions and influence the geographical distribution of some species. The potential for global climate change to influence the frequency and distribution of frost events is uncertain, but it seems likely that they may become more frequent in some areas and less frequent in others.
Aim
The aim of this study was to test, based on biological theory, which facet of temperature is most closely associated with the elevational and latitudinal low‐temperature limits of seven European broad‐leaved tree species. We compared three temperature‐related potential constraints across three study regions: (1) absolute minimum temperature within 100 years; (2) lowest temperatures during the period of bud‐break; and (3) length and temperature of the growing season.
Location
Western and Eastern Swiss Alps (1165–2160 m a.s.l.) and southern Sweden (57° N–59° N).
Methods
In situ temperature was recorded at the high‐elevation and high‐latitude limits of seven broad‐leaved tree species and correlated with temperatures at the nearest weather stations, in order to reconstruct the temperature regime for the past 50 years. By applying generalized extreme value distribution theory, we estimated the lowest temperatures recurring during the life span of a tree.
Results
At their high‐elevation limits, five out of the seven tree species experienced winter minimum temperatures considerably warmer than their known maximum freezing resistance in winter. For the bud‐break period, potentially damaging temperatures occurred at both the elevational and the latitudinal limits and for all four species for which phenological data were available. Three out of five species for which a latitudinal replicate was available showed a similar length of growing season at their respective elevational and latitudinal limits. The mean temperature during the growing season was always warmer at a species’ latitudinal limit than at its elevational limit, and hence this variable does not bear general explanatory power for the range limit.
Main conclusions
Low‐temperature extremes during bud‐break are the most likely candidates for controlling the elevational and latitudinal limits of broad‐leaved tree species. The absolute minimum temperature in winter and the mean temperature during the growing season are unlikely to constrain the cold limits of these species. Thus, the results call for the use of temperature data (extremes) during key stages of spring phenology when attempting to explain the low‐temperature range limits and to predict the potential range shifts of deciduous tree species.
A survey revealed that researchers still seem to encounter difficulties to cope with outliers. Detecting outliers by determining an interval spanning over the mean plus/minus three standard deviations remains a common practice. However, since both the mean and the standard deviation are particularly sensitive to outliers, this method is problematic. We highlight the disadvantages of this method and present the median absolute deviation, an alternative and more robust measure of dispersion that is easy to implement. We also explain the procedures for calculating this indicator in SPSS and R software.
Crop yields are affected by many factors, related to breeding, management and climate. Understanding these factors, and their relative contributions to historical yield increases, is important to help ensure that these yield increases can continue in the future. Two important factors that can affect yields are planting dates and the crop's growing degree day (GDD) requirements. We analyzed 25 years of data collected by the USDA in order to document trends in planting dates, lengths of the vegetative and reproductive growth periods, and the length of time between maturity and harvest for corn and soybeans across the United States. We then drove the Agro-IBIS agroecosystem model with these observations to investigate the effects of changing planting dates and crop GDD requirements on crop yields and fluxes of water and energy. Averaged across the U.S., corn planting dates advanced about 10 days from 1981 to 2005, and soybean planting dates about 12 days. For both crops, but especially for corn, this was accompanied by a lengthening of the growth period. The period from corn planting to maturity was about 12 days longer around 2005 than it was around 1981. A large driver of this change was a 14% increase in the number of GDD needed for corn to progress through the reproductive period, probably reflecting an adoption of longer season cultivars. If these changes in cultivars had not occurred, yields around 2005 would have been 12.6buac−1 lower across the U.S. Corn Belt, erasing 26% of the yield increase from 1981 to 2005. These changes in crop phenology, together with a shortening of the time from maturity to harvest, have also modified the surface water and energy balance. Earlier planting has led to an increase in the latent heat flux and a decrease in the sensible heat flux in June, while a shorter time from maturity to harvest has meant an increase in net radiation in October.
Large changes in the wintertime atmospheric circulation have occurred over the past two decades over the ocean basins of the Northern Hemisphere, and these changes have had a profound effect on regional distributions of surface temperature and precipitation. The changes over the North Pacific have been well documented and have contributed to increases in temperatures across Alaska and much of western North America and to decreases in sea surface temperatures over the central North Pacific. The variations over the North Atlantic are related to changes in the North Atlantic Oscillation (NAO). Over the past 130 years, the NAO has exhibited considerable variability at quasi-biennial and quasi-decadal time scales, and the latter have become especially pronounced the second half of this century. Since 1980, the NAO has tended to remain in one extreme phase and has accounted for a substantial part of the observed wintertime surface warming over Europe and downstream over Eurasia and cooling in the northwest Atlantic. Anomalies in precipitation, including dry wintertime conditions over southern Europe and the Mediterranean and wetter-than-normal conditions over northern Europe and Scandinavia since 1980, are also linked to the behavior of the NAO. Changes in the monthly mean flow over the Atlantic are accompanied by a northward shift in the storm tracks and associated synoptic eddy activity, and these changes help to reinforce and maintain the anomalous mean circulation in the upper troposphere. It is important that studies of trends in local climate records, such as those from high elevation sites, recognize the presence of strong regional patterns of change associated with phenomena like the NAO.
Climate change, with both warmer spring temperatures and greater temperature fluctuations, has altered phenologies, possibly leading to greater risk of spring frost damage to temperate deciduous woody plants. Phenological observations of 20 woody species from 1993 to 2012 in Trelease Woods, Champaign County, Illinois, USA, were used to identify years with frost damage to vegetative and reproductive phases. Local temperature records were used in combination with the phenological observations to determine what combinations of the two were associated with damage. Finally, a long‐term temperature record (1889–1992) was evaluated to determine if the frequency of frost damage has risen in recent decades.
Frost ≤−1.7°C occurred after bud‐break in 14 of the 20 years of observation. Frost damage occurred in five years in the interior and in three additional years at only the forest edge. The degree of damage varied with species, life stage, tissue (vegetative or reproductive), and phenological phase. Common features associated with the occurrence of damage to interior plants were (1) a period of unusual warm temperatures in March, followed by (2) a frost event in April with a minimum temperature ≤−6.1°C with (3) a period of 16–33 days between the extremes.
In the long‐term record, 10 of 124 years met these conditions, but the yearly probability of frost damage increased significantly, from 0.03 during 1889–1979 to 0.21 during 1980–2012. When the criteria were “softened” to ≤−1.7°C in April and an interval of 16–37 days, 31 of 124 years met the conditions, and the yearly damage probability increased significantly to 0.19 for 1889–1979 and 0.42 for 1980–2012.
In this forest, the combination of warming trends and temperature variability (extremes) associated with climate change is having ecologically important effects, making previously rare frost damage events more common.