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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.
... 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.
... The fact of earlier spring flowering is closely associated with the growing risk of spring frosts at the time of fruit trees flowering. Many authors have examined the increase in the risk exposure of fruit trees to spring frosts in their country, e.g., [17] evaluated this task in Switzerland. High losses in fruit and wine growing have been and are being recorded, especially in the last decades. ...
... Notably, [7] revealed in their study the importance of reliable phenological models which not only work for current but also for changed climate conditions and at different sites. Notably, [17] suggested in their results that frost risk needs to be considered carefully when promoting the introduction of new varieties of fruit trees in warmer and drier climates or when considering new plantations at higher elevations. Freeze damage is one of the main limiting factors to horticultural crop production [8]. ...
... Freeze damage is one of the main limiting factors to horticultural crop production [8]. Many authors, e.g., [17] suggested that frost risk needs to be considered carefully when promoting the introduction of new fruit tree varieties adapted to a warmer and drier climate. Similar findings were found [12] in their research about the sensitivity of cherry trees to sub-zero temperatures. ...
Climate change affects the agroecological conditions and persistence of cherry tree flowering. Detailed evaluation of minimum air temperature and occurrence of synoptic events occurrence during spring frosts within the cherry tree flowering in the Czech Republic (Central Europe) is missing. The main objective of this study was to evaluate the above-mentioned variables during the cherry tree flowering in different parts of the country from 1924 to 2012. Our question was how the frequency of frost days occurrence changed during the cherry tree flowering. A trend analysis was conducted with the Mann-Kendall test. The onset of the beginning of flowering and end of flowering shifted to an earlier date per the whole examined period (up to −13.9 and −8.1 days) and the period of flowering extended (up to 4.1 days). The shifts were more pronounced at higher elevations. During the period of the cherry tree flowering, the trend in change of the number of frost days was negative at the lowland station (−0.3 day) and positive at the highland station (+1.2 day). At all stations, “Ap3” synoptic event (anticyclone) occurrence during cherry tree flowering on days with the highest spring frost risk (Tmin at 2 m < −1.1 °C) prevailed. The positive trend of frost-day occurrence and the negative trend of minimum air temperature in cherry tree flowering indicate that blossoms are more endangered at higher elevations.
... A prolonged growing season starts with an advanced forest phenology driven by a unnatural warming (Chmielewski et al. 2018). An earlier phenology characterized as advanced sprouting and flowering increases the risk of frost damage on newly growing organs, which included sprouted buds, dehardened twigs, unfolded leaves, blooming flowers, and young fruits (Rodrigo 2000, Park 2016, Chmielewski et al. 2018, Vitasse et al. 2018. The loss of carbon (C) in a false spring was unlikely to be offset by post-spring continuous growth under a warming climate (Awaya et al. 2009, Hufkens et al. 2012, Chamberlain et al. 2020. ...
... Franco) (Malmqvist et al. 2017), Norway spruce (Picea abies [L.] Karst. (Olsson et al. 2017, Vitasse et al. 2018, and Scots pine (Pinus sylvestris L.) (Muilu-Makela et al. 2017) were all reported to have suffered severe damages from a spring frost. In a broadened geographical range across North America, Europe, and Asia, broad-leaved trees and shrubs were found to be more reactive than conifers to winter-spring thermal time (Zohner et al. 2020). ...
... In a broadened geographical range across North America, Europe, and Asia, broad-leaved trees and shrubs were found to be more reactive than conifers to winter-spring thermal time (Zohner et al. 2020). Documented cases of false spring frosts damaged budburst in broad-leaved trees that showed visual damage included but not limited to European beech (Fagus sylvatica L.) (Kreyling et al. 2012, Principe et al. 2017, Schieber et al. 2017, Bascietto et al. 2018, Vitasse et al. 2018, pedunculate oak (Quercus robur L.) (Puchalka et al. 2016), apple (Malus domestica Borkh.), and cherry (Prunus persica avium L. and Prunus persica cerasus L.) (Chmielewski et al. 2018, Vitasse et al. 2018). Most of current observations on phenological responses were derived from studies on remotely montane fields where forests were mostly dominated by tree species used for timber and fruiting harvests. ...
Information is highly scarce about the possible effect of a late spring frost on physiological response of buds in ornamental trees. In this study, spring temperature of Changchun at Northeast China was recorded to identify the characteristics of a false spring by detecting extraordinary warming and sudden freeze in early April of 2017. Buds of six local ornamental tree species were investigated for their dynamics in biomass, non-structural carbohydrates, frost resistance on days of 7, 14, 21, and 28 April 2017. According to a comparison with spring temperature records historically from 2007 to 2016, a false spring was determined. Black pine (Pinus tabuliformis var. mukdensis) had greater bud biomass than apricot (Prunus sibirica L.). Peach (Prunus persica L. var. persica f. rubro-plena Schneid.) reserved greater non-structural carbohydrate content in post-chilling buds than black pine, and apricot and willow (Salix babylonica L.) had greater soluble sugars and starch contents in buds, respectively. Cumulative number of days with temperature below 12°C had a negative relationship with relative conductance in sorbus (Sorbus pohuashanensis [Hance] Hedl.). Chokecherry (Padus virginiana ‘Canada Red’) had greatest bud starch content on 21 April. Overall, a late spring frost imposed interruption on carbohydrate metabolism rather than direct damage on buds of ornamental trees before late April. Advanced warming induced more pronounced negative impact of a false spring than the sudden decline of minimum temperature.
... A recent study predicted that warming increases winter chill leading to greater advances in budburst (Ettinger et al., 2020). It is likely that if spring phenology advances more quickly than late frosts retreat, plant tissues may be more frequently exposed to frost damage in the future (Vitasse, Schneider, et al., 2018). In the past, spring frost events have caused yield losses in the production of sweet cherry. ...
... Our results highlight the importance of research focusing on low chill cultivars of sweet cherries. However, cultivars with lower chill requirements tend to be characterized by earlier flowering dates, especially under warming spring temperatures and may therefore be at higher risks of frost damage (Bigler and Bugmann, 2018;Vitasse, Schneider, et al., 2018). The severity of adverse weather conditions depends on cultivar characteristics (Trnka et al., 2014;Vanalli et al., 2021). ...
... In terms of frost exposure, our results show that climate warming might bring along an increasing risk of frost damage to sweet cherry trees. A recent study using longterm series of phenological observations in Switzerland suggested that cherry trees require on average 147 GDDs to flower (Vitasse, Schneider, et al., 2018). In our study, heat accumulation before the LSF event in the Lanzhou-Lianyungang region is 51 GDDs (95% CI: 5-140 GDDs) during 1975-2015, indicating that the risk of frost damage to cherry trees is currently small. ...
Given the strong sensitivity of sweet cherry trees to air temperature and the foreseeable warming under future climates, it becomes urgent to analyse spatiotemporal variability of growing conditions in main production areas of China. Here, we estimated changes of three climate metrics, that is, winter chill, heat accumulation and the risk of spring frost events, by using 22 global climate models over the historical and future (represented by central years 2050s and 2085s) time stages. Statistically downscaled daily maximum and minimum temperatures at 14 sites under representative concentration pathway (RCP) 4.5 and 8.5 scenarios were used. The results show a general increase of available winter chill for most sites in Bohai and Lanzhou–Lianyungang Railway line agro‐climatic zones, and the increase in chill accumulation could reach up to 15.2% in these regions for RCP4.5 by 2085 s. However, the most dramatic winter chill decrease is projected to occur in the southwest region under the RCP8.5 scenario by 2085 s. Additionally, the increase rate of heat accumulation during the forcing period shows spatially consistency, and the most pronounced increase is found in the RCP8.5 by 2085 s. In the north region, median heat accumulation increases by 17.5%–21.0% in the 2050 s under RCP4.5. Similar increasing range could be found in the southwest station. High frost risk areas are found in the southwestern region for both baseline and future climate scenarios. Across the 14 study sites, Mengzi and Kunming have the highest meteorologically defined risk of spring damaging frost with accumulated 335 growing degree days (GDDs) and 264 GDDs before the last spring frost event, respectively. Overall, this study provides projected characteristics of site‐specific growing conditions for sweet cherry trees in main production regions. The results could be useful for decision‐making such as selection of appropriate species and varieties in adapting to future warming.
... A recent study predicted that warming increases winter chill leading to greater advances in budburst (Ettinger et al., 2020). It is likely that if spring phenology advances more quickly than late frosts retreat, plant tissues may be more frequently exposed to frost damage in the future (Vitasse, Schneider, et al., 2018). In the past, spring frost events have caused yield losses in the production of sweet cherry. ...
... Our results highlight the importance of research focusing on low chill cultivars of sweet cherries. However, cultivars with lower chill requirements tend to be characterized by earlier flowering dates, especially under warming spring temperatures and may therefore be at higher risks of frost damage (Bigler and Bugmann, 2018;Vitasse, Schneider, et al., 2018). The severity of adverse weather conditions depends on cultivar characteristics (Trnka et al., 2014;Vanalli et al., 2021). ...
... In terms of frost exposure, our results show that climate warming might bring along an increasing risk of frost damage to sweet cherry trees. A recent study using longterm series of phenological observations in Switzerland suggested that cherry trees require on average 147 GDDs to flower (Vitasse, Schneider, et al., 2018). In our study, heat accumulation before the LSF event in the Lanzhou-Lianyungang region is 51 GDDs (95% CI: 5-140 GDDs) during 1975-2015, indicating that the risk of frost damage to cherry trees is currently small. ...
China is the largest fruit producer and consumer market in the world. Understanding the growing conditions responses to climate change is the key to predict future site suitability of main cultivation areas for certain deciduous fruit trees. In this study, we used dynamic and growing degree day models driven by downscaled daily temperatures from 22 global climate models to project the effects of climate change on growing conditions for deciduous fruit trees under two representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios over 2 future time periods (represented by central years 2050s and 2085s) in northern China. The results showed a general increase of available winter chill for all sites under RCP4.5 scenario, and the most dramatic increase in chill accumulation could reach up to 36.8% in northeast regions for RCP8.5. However, the forecasted chill will decrease by 6.4% in southeast stations under RCP8.5 by 2085s. Additionally, the increase rate of growing season heat showed spatially consistency, and the most pronounced increase was found in the RCP8.5 by 2085s. For the southwest station, median heat accumulation increased by 20.8% in the 2050s and 37.1% in the 2085s under RCP8.5. Similar increasing range could be found in the northeast station; the median growing season heat increased by 19.8% and 38.8% in the 2050s and 2085s under RCP8.5, respectively. Moreover, the date of last spring frost was expected to advance and the frequency of frost occurrences was projected to decline in the study area compared to the past. Overall, the present study improves understanding regarding site-specific characteristics of climatic suitability for deciduous fruit tree cultivation in main producing regions of northern China. The results could provide growers and decision–makers with theoretical evidence to take adaptive measure to ensure fruit production in future.
... Cold spell is another form of extreme event that can cause vegetation damage by leaf frostbite, shortening growing season, and reducing photosynthetic carbon uptake 19,20 . The vegetation productivity responses to compound events that include cold extremes have received little attention so far. ...
... In mid-to-high latitudes, we find directly and lagged adverse synergistic effects of CCD events on productivity. Temperate and boreal vegetation are most vulnerable to cold extremes 19 , which often negatively affect productivity and result in extensive reductions in productivity 20 . Moreover, our results suggest that the lagged effects of CCD spring can be of similar magnitude as direct adverse effects. ...
... Spring cold events are regarded as climatic extremes with high ecological and evolutionary importance. Destruction of foliage, flowers and unripe fruits caused by spring cold is a sustainable damage for plants because it negatively impacts on nutrient storage, growth, reproduction, leaf development, and even ultimately survival in subsequent years 19 . The coupling of cold with dry condition thus can cause long-term negative effects on vegetation due to vegetation carryover effects. ...
Compound climate events can strongly impact vegetation productivity, yet the direct and lagged vegetation productivity responses to seasonal compound warm-dry and cold-dry events remain unclear. Here we use observationally-constrained and process-based model data and analyze vegetation productivity responses to compound events of precipitation and temperature in spring and summer across global mid-to-high latitudes. We find regional asymmetries in direct and lagged effects of compound warm-dry events. In high-latitudes (>50°N), compound warm-dry events raise productivity. In contrast, in mid-latitudes (23.5–50°N/S), compound warm-dry events reduce productivity and compound warm-dry springs can cause and amplify summer droughts, thereby reducing summer productivity. Compound cold-dry events impose direct and lagged adverse impacts on productivity in mid-to-high latitudes, exceeding the impacts from individual cold and dry events. Our results highlight the benefits of a multivariate perspective on vegetation vulnerability as precipitation and temperature often covary and jointly drive vegetation impacts.
... 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—AGL) 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. ...
... Therefore, the phenological stage of budburst represents a crucial stage in the development of grapevine (Vitis vinifera L.) [3,10,[17][18][19]. In other fruit trees such as apple (Malus domestica) [7,9,11,20], peach (Prunus persica) [12,[21][22][23], pear (Pyrus communis) [6], and sweet cherry (Prunus avium L.) [4,5], an equally crucial stage exposed to high spring frost risk is flowering. With rising spring temperatures, the water content in buds and shoots increases and the cold resistance of the buds steadily decreases [3,24,25]. ...
... Consequently, frost damage may occur at temperatures below freezing if the fruit tree is at a sensitive phenological stage, such as budburst or flowering [1,6]. However, in recent years, both increasing and decreasing risks of spring frosts have been reported under future climate conditions [4][5][6][7][8][9][10][11][12]. The phenology of temperate fruit trees is mainly determined by radiative forcing, which is strongly influenced by seasonal changes. ...
As spring frost proves to be an increasing risk throughout Slovenia and Europe, a better assessment of frost risk is needed. The statistical approach presented in this article consists of the conditional probability that the last spring frost occurs before budburst or flowering. The analysis was conducted using two separate phenological models and phenological data of various grapevine (Vitis vinifera L.), apple (Malus domestica), and sweet cherry (Prunus avium L.) varieties in locations across Slovenia. The increase in risk of spring frost for grapevine ranged from 1 to 1980, from 0.06 to 12 for apple, and from 1 to 180 for sweet cherry. Overall, the varieties most prone to frost proved to be Refošk (Teran) and Merlot grapevine varieties as well as the Germersdorf sweet cherry variety. We have identified the location in the hilly region with moderate climate where the Bobovec apple variety is grown as the least exposed to frost. Although counterintuitive, the GDD generally proved somewhat more efficient than the two-phase phenological model BRIN, although not in all cases. For the purpose of the study, the phenological models were calibrated, and the model parameters can serve as invaluable information for further research of this topic.
... Generally, Europe experienced a significant increase in late spring frost days during the growing seasons between 1982 and 2012 (Liu et al., 2018). However, the occurrence of frost days during the growing seasons of individual species differs on a regional or local scale (Knozová, 2017, Vitasse et al., 2018, Koźmiński et al., 2021. Our results confirm the altitudinal and regional heterogeneity in late spring frost occurrence similarly to other studies dealing with the phenology of tree species from the family Rosaceae. ...
... In Belgium, pear flowering is expected to be less often affected by spring frost at lower altitudes below 300 m compared to higher elevations, where vulnerability for frost damage remains high (Drepper et al., 2022). Similarly in Switzerland, the risk of frost exposure and subsequent potential damage has increased for cherry and apple flowers at the vast majority of stations located at elevations higher than 800 m while remaining unchanged at lower elevations (Vitasse et al., 2018). On the contrary, in Italy, a risk analysis confirmed a lower risk of exposure of flowering apple trees to frost at present than in the past and probably either constant or slightly lower risk in the future (Eccel et al., 2009). ...
The onset and duration of phenological events are key indicators of the ecological impact of climate change on vegetation. During the flowering time in spring, late frosts are one of the most dangerous meteorological phenomena leading to damage to crops. During 1987–2016, we analyzed the occurrence and intensity of frosts during the period around the weather lore “Frost on the Ice Saints burns all the flowers” in short, “The Ice Saints” and their effects on the flowering phenology of hawthorn (Crataegus laevigata (Poir.) DC.). The late frosts were identified at 0.05 m and 2.0 m above ground from temperature measurement data at five phenological stations located from 160 m to 700 m a.s.l. in Slovakia. Results indicate that recent climate change caused the beginning of flowering (BBCH60) for Crataegus laevigata to start significantly earlier by 4.2, 5.0, 6.2 and 3.6 days per decade at 160, 300, 400 and 500 m a.s.l., respectively. Thus, the risk of late frost damage to flowers during “The Ice Saints” is getting highly probable, particularly at 160, 300 and 500 m a.s.l., where the flowering and frosts occur simultaneously. Decreased risk of frost damage during “The Ice Saints” was found at 400 and 700 m a.s.l. It was because of the rare frost occurrence at 400 m a.s.l. in the last decade (2007–2016) of the studied period, and due to the flowering onset dated mostly after "The Ice Saints" at 700 m a.s.l. in the same period.
... In theory, rising minimum temperature may decrease the impact of frost damage during flowering on apple growth (Drepper et al., 2022;Eccel et al., 2009;Guo et al., 2019;Hoffmann and Rath, 2013;Kramer, 1994). However, a large number of studies found that the frost risk during flowering would increase due to an advance in flowering date of apple caused by winter and spring warming (Darbyshire et al., 2013;Unterberger et al., 2018;Vitasse et al., 2018;Yang et al., 2021). ...
... Climate warming may decrease the frequency of frost occurrence during crop growing season (Guo et al., 2019;Ma et al., 2019;Zohner et al., 2020). However, the flowering frost risk may increase because of earlier exposure to frost due to an advance in flowering date caused by winter and spring warming and higher frequency of extreme low temperature (Darbyshire et al., 2013;Unterberger et al., 2018;Vitasse et al., 2018;Yang et al., 2021). Our study approved the conclusion that flowering frost occurrence days and intensities did not decrease in the study sites and even increased in recent ten years. ...
Frost damage during flowering is recognized as one of the most serious agro-meteorological disasters affecting
apple production in Shaanxi province, a typical apple producing area in China. Quantitative assessments of
flowering frost damage to apple yield are critical for the development of strategies on mitigating yield losses, but
have been rarely conducted. For the first time, our study used the process-based STICS model and statistical
methods based on Lagrange interpolation method to assess the impacts of frost damage during flowering on apple
yield at five study sites over the past three decades. Four canopy temperature thresholds were set as 0 ◦ C, − 2 ◦ C,
− 5 ◦ C, and − 35 ◦ C for 0, 10%, 90%, and 100% frost damage on fruit number, respectively. The study results
showed that STICS could effectively simulate the phenology and yield of apple, with the simulation errors less
than 15%. Simulated yield losses caused by frost damage during flowering by STICS model were consistent with
that estimated by statistical methods. Average yield loss due to frost damage during flowering estimated by
STICS model was 6.35–29.27% in frost years during past three decades at five study sites. In general, both the
frost occurrence days and intensities were the highest in the recent ten years. Our study provides a method to
quantitatively assess the impacts of frost damage during flowering on apple yield for the prevention and miti-
gation of frost disasters in apple production.
... 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.
... Frost is one of the main environmental factors that causes damage and economic losses among plants (Vitasse et al. 2018) because of water freezing within and outside of the cells, which leads to the damage of tender buds, owers and fruits. Although rising temperatures due to climate warming usually increase the average temperature in winter and early spring, as well as reduce the number of annual days of low temperatures (Robeson 2002;Fernández-Long et al. 2013), the spatiotemporal characteristics of frost events during the blossoming and early fruiting stages are highly variable and widely reported in temperate zones, such as North American ecosystems (Gu et al. 2008;Augspurger 2013), forest and fruit plantations in Europe (Yann et al. 2018) and Asia (Yang et al., 2021;Wang et al., 2021a, b). ...
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.
... As a perennial crop that is affected by the climate throughout the year, fruit trees are considered to be vulnerable to climate change [3]. A temperature rise due to climate change leads to an advance in the spring phenology of fruit trees in high-altitude areas of Switzerland, which increases the risk of frost [4], and the amount of winter cold required for temperate trees to overcome dormancy is expected to be greatly reduced in the future in the most deciduous fruit-growing areas [5]. In this context, determining how species and cultivars adapt to certain climates is of primary interest in research and decision-making, to explore the potential for cultivation in new areas and to allow for the development of adaptation strategies to climate change in current locations. ...
Planting suitability determines the distribution and yield of crops in a given region which can be greatly affected by climate change. In recent years, many studies have shown that carbon dioxide fertilization effects increase the productivity of temperate deciduous fruit trees under a changing climate, but the potential risks to fruit tree planting caused by a reduction in suitable planting areas are rarely reported. In this study, Maxent was first used to investigate the spatial distribution of five Pyrus species in China, and the consistency between the actual production area and the modeled climatically suitable area under the current climatic conditions were determined. In addition, based on Coupled Model Intercomparison Project Phase 6, three climate models were used to simulate the change in suitable area and the migration trend for different species under different emission scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). The results showed that the suitable area for pear was highly consistent with the actual main production area under current climate conditions. The potential planting areas of P. ussuriensis showed a downward trend under all emission paths from 2020 to 2100; other species showed a trend of increasing first and then decreasing or slowing down and this growth effect was the most obvious in 2020–2040. Except for P. pashia, other species showed a migration trend toward a high latitude, and the trend was more prominent under the high emission path. Our results emphasize the response difference between species to climate change, and the method of consistency analysis between suitable planting area and actual production regions cannot only evaluate the potential planting risk but also provide a reasonable idea for the accuracy test of the modeled results. This work has certain guiding and reference significance for the protection of pear germplasm resources and the prediction of yield.
... Information on this relationship in species will contribute to the elucidation of the mechanisms underlying local adaptation to late frost regime in temperate tree species. Furthermore, measuring the genetic differentiation among populations for the timing of leaf out would aid in assessing the adaptability of the species in ongoing climate change because the risk of late frost damage is increasing owing to climate warming in Asia and Europe [20,21]. ...
We studied the genetic differentiation in budburst timing among Fagus crenata populations along spatial gradients in late frost timing in the Hakkoda Mountains, northern Japan, by focusing on last fatal frost day and topography. For budburst timing, we analyzed interpopulation variations in habitats, genetic variations in a nursery, and the relationships between these variations and environmental conditions in the habitats. Analyses of interpopulation variation showed that the day and the temperature sum of budburst positively correlated with the last fatal frost day in the habitats. Analyses of genetic variation showed significant genetic variations among provenances and families for both traits. For all provenances, the heritability for these traits were 0.7–0.8. The genetic variations were significantly associated with variations in the last fatal frost day among the provenances, suggesting that natural selection due to late fatal frost causes genetic differentiation in the traits along the spatial gradient in late frost timing. These results demonstrate that late frost is a key factor driving genetic differentiation of leaf-out phenology within a regional tree population.
... Changes in frost risk may vary as a function of geography, species, and even genetic provenance (Kramer et al., 2017;Bigler and Bugmann, 2018;Mura et al., 2022). Warming conditions in Switzerland are increasing, decreasing, or leaving unchanged the risk of spring frost damage to foliage of temperate tree species, depending on elevation (Bigler and Bugmann, 2018;Vitasse et al., 2018). Although most of the forests across North America are experiencing declines in the risk of damaging spring frost, many parts of the northeastern U.S. are actually experiencing an increase (Zohner et al., 2020). ...
Spring frosts can defoliate trees, reduce canopy carbon assimilation, and alter interspecific competition dynamics. These events may become more common with climate change, but our understanding of the associated ecological impacts is limited by the stochastic nature of their occurrences. In 2020, a late spring frost defoliated oak (Quercus spp.), but not co-occurring maples (Acer spp.) across temperate broadleaf forests of the Hudson Highlands in southern New York State, U.S.A. Defoliation impacted 60% of this region’s forests and delayed full leaf expansion of oaks by ∼17 days. We used this event as an opportunity to advance understanding of how leaf-level physiology, radial growth, and interspecific competition dynamics of mature trees respond to frost-induced defoliation. We quantified leaf-level photosynthetic capacity, stomatal conductance, and water-use efficiency (WUE), as well as basal area increment of defoliated red oak (Q. rubra) trees and non-defoliated red maple (A. rubrum) trees in 2020 (“defoliation year”) and 2021 (“reference year”). Oak defoliation provided red maple trees with a competitive edge in terms of photosynthetic capacity early in the growing season. However, the second cohort of red oak leaves that developed following defoliation had photosynthetic capacities that were 3–4 times higher than red maple trees by the second half of the growing season, likely facilitated by higher rates of stomatal conductance. The growing season mean photosynthetic capacities for the defoliation year were significantly higher for red oaks than red maples. Red oak basal area increment tended to be higher than red maple during both the defoliation and reference years. For both species basal area increment was significantly higher during the reference year than defoliation year, but the reasons remain unclear. Taken together, these findings demonstrate that temporal patterns of photosynthesis in temperate broadleaf forests are altered by defoliation events, but enhanced photosynthetic capacities of second cohort leaves can reduce the negative effects of delayed leaf expansion and mitigate competitive advantages conferred to undefoliated co-occurring tree species. We suggest that understanding a tree species’ ability to compensate for frost-induced defoliation is essential to accurately predict effects of extreme climate events on tree competition dynamics and ecosystem processes.
... The study of the features of cherry phenological phases passage was carried out in accordance with [9]. Statistical processing of experimental data was carried out by variance analysis method [10], as well as with the use of "Excel" computer program. The objects of research are presented in Table 1. ...
This article presents the results of studying the features of main phenological phases passage by varieties, selected and elite seedlings of common cherry in the conditions of the Orel region. The research was carried out on the basis of stone crops plantings of the Russian Research Institute of Fruit Crop Selection in 2018–2020. The purpose of the research was to study the peculiarities of phenological phases passage by common cherry cultivars from the VNIISPK gene pool. During the studies it was found that Turgenevka, Businka and Kapelka varieties are early-ripening, in conditions of the Orel region, and forms 84847, 84595 and 84854, Putinka, Umanskaya Skorospelka are late-ripening. The duration of cherry cultivars vegetation season was determined at the level of 175–194 days. The sum of active temperatures during the vegetation season of cherry cultivation was 2592.4–2650.9 oC. The variance analysis allowed to determine a certain influence degree of the year conditions on vegetation season duration and sum of active temperatures necessary for the varieties to pass the phenological phases successfully.
... Frost can significantly damage crops (Woldendorp et al., 2008;Qian et al., 2010), and is one of the possible climatic conditions leading to a decrease in yield and quality of crops and fruit trees (Frederiks et al., 2015;Crimp et al., 2016；Sgubin et al., 2018Gobbett et al., 2021;Rubio-Cuadrado et al., 2021). Frost is harmful to fruit trees (e.g., grapevine [Vitis vinifera L.], sweet cherry [Prunus avium L.], apple [Malus sylvestris (L.) Mill.]) (Cittadini et al., 2006;Sgubin et al., 2018;Vitasse et al., 2018;Szalay et al., 2019), and crops (e.g., potato [Solanum tuberosum L.], maize [Zea mays L.], wheat [Triticum aestivum L.]) (Barlow et al., 2015;Pulatov et al., 2015;Xiao et al., 2018;Wang et al. 2019). Research in recent years has shown that global climate warming is strengthening (Zhang et al., 2022), and extreme climate events occur from time to time Meehl et al., 2000). ...
Spring frost damage (SFD) is the main meteorological disaster limiting the tea industry in the region of the north of the Yangtze River (NYR) in China. Research regarding an SFD indicator for tea plants is of great significance for prevention and control of spring frosts, as well as for timely monitoring and early warning. Based on daily minimum air temperatures (Tmin) and spring frost disaster records in NYR from 1961 to 2020, the Receiver Operating Characteristic curve (ROC) was used to evaluate the accuracy of frost identification, and the critical temperature threshold for SFD to tea plants was determined by jointly comparing Overall Accuracy and the Youden Index. The results showed that the area under the ROC curve was 0.977, indicating that Tmin performed well in identifying frost events. The critical temperature threshold for spring frost in NYR was determined as Tmin of 3.7 °C, and 93 % of frost occurrences were correctly identified. Based on the determined critical threshold of SFD, the number of spring frost days, first frost date (FFD), and last frost date (LFD) in NYR from 1961 to 2020 were analyzed. The results showed that the number of spring frost days in NYR decreased from north to south. FFD appeared earlier and LFD ended later in northern NYR than in southern NYR. These results provide theoretical and technical support for the monitoring and evaluation of spring frosts in NYR, and also for implementing SFD prevention and control measurements for tea plants by use of a critical temperature threshold.
... This was because false spring also occurred in subtropical regions (Zhang et al. 2021b), and it was also supported by the record of below-zero temperature in late March and mid-April by our weather stations (Table S2). Additionally, the temperature in plant tissues would be several degrees lower than the measured air temperature on clear and windless nights (Leuning and Cremer 1988), thus late frost damage in trees had already occurred when the air temperature approached 0 ℃ (Vitasse et al. 2018b;Zohner et al. 2020). However, the magnitude of phenological responses to elevational change differed between phenophases. ...
Key message
Spring leaf phenology delayed with increasing elevation, and the onset of bud development showed less response to elevation. Bud development advanced under increased forcing and delayed under decreased chilling.
AbstractPlant phenology is highly sensitive to environmental changes and is driven mostly by temperature. However, elevational pattern, adaptation strategies, and temperature sensitivity of spring leaf phenology of trees in subtropical mountain forests remain rarely explored, despite their important implications for predicting how plant phenology may respond to global warming. Here, we monitored the timing and duration of bud development for three rare, endangered, and deciduous tree species (Euptelea pleiospermum, Cercidiphyllum japonicum, and Tetracentron sinense) along an elevational gradient in the Shennongjia Mountains in central China. We then conducted a twig experiment in the climate chambers to test the phenological sensitivity of leaf to forcing and chilling. The results showed that with increasing elevation, the onset of bud development and leaf unfolding were consistently delayed and the duration of bud development was lengthened. The magnitude of the phenological responses to elevational change differed between phenological stages, and the onset of bud development showed a lower response to elevation than leaf unfolding. Additionally, after accounting for elevation, a negative relationship between the onset and duration of bud development was observed. The results from twig experiments showed that the timing of bud development advanced under increased forcing and delayed under decreased chilling. We infer that leaves may unfold earlier under warmer springs, but the advance may be slowed down by warmer winters. The phenological sensitivity to temperature is species-specific, and E. pleiospermum was the most sensitive species. Our results suggest that the spring leaf phenology of rare and endangered tree species in subtropical mountain forests has a significant elevational trend and is sensitive to temperature changes. We also highlight that the important role of chilling should be considered when predicting the phenological shift under climate change.
... The forecasting models of global warming predict more frequent occurrence of extreme climatic conditions, including extraordinary temperatures, which may affect the phenological processes and tolerance of our plants against frost and other environmental factors. It should be stated that frost damage is becoming more common in apple orchards (Eccel et al., 2009;Kaukoranta et al., 2010;Vitasse et al., 2018). ...
p class="042abstractstekst">The success of apple production is influenced by frost damages. Occurrence of extreme temperatures is increasing worldwide because of global warming, so the risk of frost damages is also increasing in apple orchards during dormancy and blooming time. In our work the frost hardiness of flower buds of eight apple cultivars was observed with artificial freezing tests during four subsequent dormancy periods in Hungary. The studied cultivar assortment contained two standard commercial cultivars (‘Gala’, ‘Idared’), two scab-resistant cultivars from abroad breeding programmes (‘Florina’, ‘Prima’) and four new Hungarian multi-resistant (mainly scab-resistant) cultivars (‘Artemisz’, ‘Cordelia’, ‘Hesztia’, ‘Rosmerta’). There were remarkable differences between cultivars and years from the aspect of frost hardiness of generative overwintering organs. At the end of hardening period, in January, the LT<sub>50</sub> values of flower buds were between -22.4 °C and -30.4 °C according to cultivar and year. LT<sub>50</sub> means the temperature causing 50 % frost damage in the flower buds of the certain cultivar in the certain time. ‘Gala’ and ‘Florina’ were the most frost hardy, while ‘Prima’, ‘Cordelia’ and ‘Idared’ the most sensitive to frost. Cold hardiness values of flower buds of ‘Artemisz’, ‘Rosmerta’ and ‘Hesztia’ cultivars were regularly between the values of two extreme groups. In winters with inappropriate weather the generative overwintering organs were unable to reach the genetically possible frost hardiness of them.</p
... As suggested by Benmoussa et al. (2020), the projections of SWC obtained in our analysis may indicate that high-and even medium-chill species or cultivars may only thrive in particular micro-climates in the future. In accordance with previous studies (Chmielewski et al. 2018;Vitasse et al. 2018), experts acknowledged the probable increase in the risk of spring frost events in some early-blooming cultivars as well as asynchrony between pollen donors and pollen receptors in self-incompatible as well as dioecious species, which might jeopardize successful pollination, diminishing the prospect of sustainable fruit or nut yields, or require the replacement of current donor-receptor combinations to secure yields under future scenarios. Apart from dormancy-related risks, experts also hinted at additional climatic challenges, including the occurrence of heat waves and other unusual climatic events during the growing season, extended periods of drought and increasing pressure of pests and physiological disorders. ...
Temperate trees require low temperatures during winter and subsequent warm conditions in early spring to flower and eventually bear fruit. Many parts of the Mediterranean region feature winters with low and sometimes marginal chill accumulation. To assess historic and future agroclimatic conditions for cultivating temperate trees (including almonds, pistachios, apricots, sweet cherries and apples), we mapped winter chill throughout this important growing region. We used on-site weather records (1974–2020) to calibrate a weather generator and produced data for historic and future scenarios. To broaden our analysis, we spatially interpolated chill for the whole Mediterranean basin. We supplemented our simulation outcomes by collecting expert knowledge (from farmers and researchers) regarding observed climate change impacts on temperate orchards as well as future risks and concerns generated by climate change. Results showed that northern African growing regions have experienced major chill losses, a likely cause of the irregular and delayed bloom highlighted by experts. The same regions, together with southern Europe, may lose up to 30 Chill Portions by 2050 under a moderate warming scenario. For the future, experts foresee increasing risk of spring frost in early-blooming cultivars, exacerbated bloom-related problems and increasing occurrence of heat waves. Our results provide evidence of likely climate change impacts on temperate orchards. Expert knowledge proved instrumental in interpreting the simulation results as well as in orienting climate change adaptation strategies. The results we present are useful for farmers and orchard managers planning new plantings, as well as for researchers and policy makers developing strategies to adapt fruit orchards to the impacts of climate change.
... This study found that the frost risk to young leaves and flowers did not change significantly. In Switzerland, the risk of spring frost exposure and subsequent potential damage has increased for four tree species at the vast majority of stations located at elevations higher than 800 m while remaining unchanged at lower elevations (Vitasse et al., 2018). A recent study showed that the frequency of frosts in late spring has increased to a greater extent in Europe and East Asia than in North America from 1959 to 2017 (Zohner et al., 2020). ...
Woody plant species in temperate regions must withstand a cold winter and freezing events through cold acclimation and dormancy in autumn and winter. However, how seasonal changes in dormancy depth and cold hardiness affect the frost risk of temperate species is unclear because few studies have assessed dormancy depth and cold hardiness simultaneously. In this study, an experiment was conducted to estimate the dormancy depth and cold hardiness of five common woody temperate plant species during the winter of 2018/2019 in Beijing, China. Twigs of each species were collected at different dates during winter and the timing of budburst was monitored under the same forcing conditions. The dormancy depth was quantified as growing degree day (GDD) requirements of spring events. Simultaneously, the cold hardiness of buds at each sampling date was determined based on the electrical conductivity of the holding solution. Two indices (chilling accumulation and cold hardiness index) were used to simulate the past dynamics of dormancy depth, spring phenology, and cold hardiness from 1952 to 2021. The maximum dormancy depth of the study species was observed between early October and early December, and thereafter decreased exponentially. The cold hardiness peaked in mid-winter (end of December) through cold acclimation and thereafter decreased in spring (deacclimation). During the past 70 years, the budburst date (first flowering date or first leaf date) of five species was estimated to have advanced significantly, and dormancy depth in early spring was predicted to have increased owing to the warming-associated decrease in chilling accumulation. However, cold hardiness has decreased because of weakened acclimation and accelerated deacclimation under a warming climate. The frost risk before and after budburst remained unchanged because of the reduction in occurrence and severity of low-temperature events and earlier late spring frosts. The present methods could be generalized to estimate and predict the seasonal changes in dormancy depth and cold hardiness of temperate species in the context of climate change.
... The ongoing warming conditions produced by climate change are shifting the timing of phenological events by fulfilling forcing requirements earlier (i.e. accelerating ecodormancy release), potentially exposing plants to an increasing risk of frost damage due to late frost events (Gu et al., 2008;Liu et al., 2018;Vitasse et al., 2018;Zohner et al., 2020). Late frost events are characterised by freezing temperatures after plant leaf-out in the spring, often causing significant damage to crops and forests (Chamberlain et al., 2019;Rigby & Porporato, 2008). ...
Under climate change, the increasing occurrence of late frost combined with advancing spring phenology can increase the risk of frost damage in trees. In this study, we tested the link between intra-specific variability in bud phenology and frost exposure and damages. We analysed the effects of the 2021 late frost event in a black spruce (Picea mariana (Mill.) BSP) common garden in Québec, Canada. We hypothesized that the timing of budbreak drives the exposure of vulnerable tissues and explains differences in frost damage. Budbreak was monitored from 2015 to 2021 in 371 trees from five provenances originating between 48° and 53° N and planted in a common garden at 48° N. Frost damages were assessed on the same trees through the proportion of damaged buds per tree and related to the phenological phases by ordinal regressions. After an unusually warm spring, minimum temperatures fell to -1.9°C on May 28 and 29, 2021. At this moment, trees from the northern provenances were more advanced in their phenology and showed more frost damage. Provenances with earlier budbreak had a higher probability of damage occurrence according to ordinal regression. Our study highlights the importance of intra-specific variability of phenological traits on the risk of frost exposure. We provide evidence that the timings of bud phenology affect sensitivity to frost, leading to damages at temperatures of -1.9°C. Under the same conditions, the earlier growth reactivation observed in the northern provenances increases the risks of late frost damage on the developing buds. This article is protected by copyright. All rights reserved.
... Frost is a common meteorological disaster which refers to a sudden drop in the air and surface temperature to below 0 °C. It has been recognized as a major threat to plant growth, development, and agricultural and forestry productivity [1,2]. Since climate warming has increased temperatures in early spring, perennial plants have become increasingly vulnerable to lower temperatures due to phenological shifts, such as advanced flowering time [3]. ...
Spring frost is a major limiting factor in the production and cultivation of apricot kernels, an ecological and economic dry-fruit tree in China. The frequent occurrence of spring frost often coincides with the blooming period of apricot kernels, resulting in significant damage to floral organs and reductions in yield. We investigated the molecular signature of pistils from two apricot kernel cultivars with different frost-resistance levels using transcriptome data. A total of 3223 differently expressed genes (DEGs) were found between two apricot kernel cultivars under freezing stress, including the bHLH and AP2/ERF-ERF transcription factors. Based on KEGG analysis, DEGs were mostly enriched in the biosynthesis of the secondary metabolites, in the metabolic pathways, and in plant-hormone signal transduction. The co-expression network, which included 81 hub genes, revealed that transcription factors, protein kinases, ubiquitin ligases, hormone components, and Ca2+-related proteins coregulated the ROS-mediated freezing response. Moreover, gene interaction relationships, such as ERF109-HMGCR1, ERF109-GRXC9, and bHLH13-JAZ8, were predicted. These findings revealed the regulatory factors for differences in frost resistance between the two tested apricot kernel cultivars and contributed to a deeper understanding of the comprehensive regulatory program during freezing stress. Some of the hub genes identified in this work provide new choices and directions for breeding apricot kernels with a high frost resistance.
... 한 온난화는 농작물의 봄철 싹트임, 개화시기 등의 생 육과정 변화 (Murray et al., 1989;Chmielewski et al., 2004;Menzel et al., 2006;Cook et al., 2012;Shi et al., 2017)를 야기시켜, 봄 늦서리 위험 노출을 증가 시킬 수 있기에 경각심을 가질 필요가 있다 (Sgubin et al., 2018;Vitasse et al., 2018;Guo et al., 2019;Pfleiderer et al., 2019 (Choi, 2004)가 있지만, 지역세부적으로 는 서리일수가 증가한 지점도 충분히 존재한다 (Kwon, 2006). 그리고 기후변화로 인한 식물의 이른 성장단계 (Min, 2000;Ho et al., 2006)에서 발생하는 예상치 못한 서리피해는 여전히 무시할 수 없다 (Jung and Yun, 2005;Jeong et al., 2018;Kim et al., 2019). ...
In order to actively prepare to frost damage that occurs in the process of growing crops, the spatial and temporal distribution of frost occurrence in South Korea was derived using frost observation data from 20 regions over the past 21 years (2000∼2020). The main products are the number of frost days, first frost day, and last frost day by region. And the climatic trends of these results were identified by performing the Mann-Kendall trend test and Sen's slope estimator. In South Korea, a lot of frost occurs in the inland area to the west of the Taebaek and Sobaek Mountains. Relatively closer to the coastal area, the number of frost days is small, the first frost day is slow, and the last frost day is early. The east coast region has fewer frost days, the first frost day is later, and the last frost day is earlier than the west coast region. The southern sea, the southeastern sea region, and the island region rarely experience frost. As a result of the annual time series trend analysis, although South Korea is a country where climate warming is progressing, there was no trend in reducing the number of frost days and slowing the first frost day, and it was found that the last frost day is delayed by 0.5 days per year.
... This is a difficult task because there are many factors influencing the impact in different sectors. In the case of agriculture, the most influencing are latitude, topography, and other local circumstances (Vitasse et al., 2018). When it comes to measures, their applicability depends largely on infrastructure, the local community, characteristics of the region, limiting factors, access to information, agricultural systems, and farmers' knowledge and experience (Niles et al., 2015, Pandey, et al., 2018. ...
Climate change has a significant impact on agriculture and there are many measures proposed for its mitigation and adaptation. The selection of the most suitable measures for given local conditions is crucial for proper planning, implementation, and sustainability. In this paper, we present the results of the evaluation and prioritization of 24 measures done by 10 experts in a
three-step multi-criteria procedure. First, experts individually assessed seven criteria for
evaluating the measures: level of responsibility, category, implementation timeframe, multifunctionality, technical skills, cost-benefit ratio, and mitigation effectiveness. Assessment of criteria and calculation of their priorities is performed by using the analytic hierarch process (AHP), well known multi-criteria method. Second, experts are grouped into three clusters according to their backgrounds, and their priorities within each cluster are aggregated into group priorities of criteria. Finally, criteria priorities of each cluster are used to rank proposed measures as alternatives by the TOPSIS method. Results obtained for three groups of experts show differences in prioritization of criteria, as well as in the ranking of adaptation and mitigation measures. The applied methodology proved that planning of adaptation/mitigation measures requires the inclusion of different experts in the assessment and evaluation process, but also careful joint analysis of the results since wrong decisions can influence financial feasibility and applicability of measures in the practice.
... Due to global warming and irregular rainfall patterns, there is continuous fruit crop failure in the autumn season (Nautiyal et al. 2020;Sharma et al. 2021a). Severe damages have been noticed due to hailstorms and windstorms during the summer season in fruits like cherry, apple, plum, peach and apricot (Choudhary et al. 2015;Vitasse et al. 2018). Even a short spell of hail can cause severe injury to the fruits and trees, both downgrading quality and subsequently causing diseases like fire blight, cankers and fruit rots (Choudhary et al. 2015). ...
Climate change is impacting agriculture through a rise in greenhouse gases, higher temperatures and extreme precipitation patterns, with adverse consequences such as hailstorms in horticultural and fruit crops. Hail is ice precipitation, usually more than 5 mm in diameter, that is formed in thunderstorms. Hailstorms contain hail particles formed when temperatures are below freezing and there is abundant super-cool liquid water which coexists with ice particles. These ice particles increase in size through collisions with super-cool droplets. Here, we review the occurrence of hailstorms and their possible impacts on fruit orchards. Mitigation strategies include anti-hail nets, cloud seeding, anti-hail guns, agrivoltaics and nanocomposites. Integrated management with chemicals and crop insurance is a viable post-hail management strategy.
... In vielen Teilen Europas nehmen zudem Häufigkeit und Intensität von Starkniederschlägen zu(Rajczak und Schär 2017). Auch die Anzahl extremer Hitzetage im Sommer, aber auch die Zahl der für die Landwirtschaft kritischen Spätfröste (z.B. während der Obst-und Weinblüte) wird in vielen Gebieten zunehmen (z.B.Trnka et al. 2014;Vitasse et al. 2018). Durch den Klimawandel werden zudem Kombinationen von Extremereignissen (z.B. ein gemeinsames Auftreten von Dürren, Hitzewellen, aber auch Starkniederschlägen), sogenannte »compound risks« (z.B. ...
... Our results showed that the advance of the leafout date in response to climate warming would slow down if European beech adopts the current strategy to adapt to future climate change. As a result, the safety margin, defined as the period (number of days) between the last spring frost and the local trees' leaf-out (Vitasse et al., 2018), would be longer under the adaptation assumption than the no adaptation assumption. Thus, local adaptation to future climate could help European beech reduce the frost risk, but this effect is only significant in coastal areas of Western Europe (Fig. S2). ...
Temperate trees could cope with climate change through phenotypic plasticity of phenological key events or adaptation in situ via selection on genetic variation. However, the relative contribution of local adaptation and phenotypic plasticity to phenological change is unclear for many ecologically important tree species. Here, we analyzed the leaf-out data of European beech (Fagus sylvatica L.) from 50 provenances planted in 7 trial sites. We first constructed a function between chilling accumulation (CA) and photoperiod-associated heat requirement (PHR) of leaf-out date for each provenance and quantified the relationship between parameters of the CA-PHR function and climatic variables at provenance origins by using the random forest model. Furthermore, we used the provenance-specific CA-PHR function to simulate future leaf-out dates under two climate change scenarios (RCP 4.5 and 8.5) and two assumptions (no adaptation and adaptation). The results showed that both CA, provenance, and their interactions affected the PHR of leaf-out. The provenances from southeastern Europe exhibited a stronger response of PHR to CA and thus flushed earlier than northwestern provenances. The parameters of the CA-PHR function were connected with climatic variables (e.g., mean diurnal temperature range, temperature seasonality) at the originating sites of each provenance. If only considering the phenotypic plasticity, the leaf-out date of European beech in 2070–2099 will advance by 6.8 and 9.0 days on average relative to 1951–2020 under RCP 4.5 and RCP 8.5, respectively. However, if F. sylvatica adapts to future climate change by adopting the current strategy, the advance of the leaf-out date will weaken by 1.4 and 3.4 days under RCP 4.5 and RCP 8.5, respectively. Our results suggest that the European beech could slow down its spring phenological advances and reduce its spring frost risk if it adopts the current strategy to adapt to future climate change.
... In addition to the date of the last frost and the minimum recorded temperature, we calculated cumulative growing degree days (cum GDD) on the day of the last frost as a proxy for the vegetation phenology advancement. To calculate the cum GDD, the heat sum was accumulated from 1 January and the standard temperature threshold of 5 °C was used (Vitasse et al., 2018). ...
Background and aims:
Understanding the mutual coordination of vegetative and reproductive growth is important in both agricultural and ecological settings. A competitive relationship between vegetative growth and fruiting is often highlighted, resulting in an apparent trade-off between structural growth and fruit production. However, our understanding of factors driving this relationship is limited.
Methods:
We used four scions grafted onto a series of size-controlling rootstocks to evaluate the relationships between the annual fruit yield and radial growth of trunks, branches and roots. To assess tree radial growth, we measured ring widths on extracted tree cores, which is an approach not frequently used in horticultural setting.
Key results:
We found that the yield and radial growth were negatively related when plotted in absolute terms or as detrended and normalized indices. The relationship was stronger in low vigour trees, but only after the age-related trend was removed. In contrast, when trunk radial growth was expressed as basal area increment (BAI), the negative relationship disappeared, suggesting that the relationship between trunk radial growth and fruit yield might not be a true trade-off related to the competition between the two sinks. The effect of low yield was associated with increased secondary growth not only in trunks but also in branches and roots. In trunks, we observed that overcropping was associated with reduced secondary growth in a subsequent year, possibly due to the depletion of reserves.
Conclusions:
Our results show that variation in annual fruit yield due to tree aging, weather cueing, and inherent alternate bearing behaviour is reflected in the magnitude of secondary growth of fruit trees. We found little support for the competition/architecture theory of rootstock-induced growth vigour control. More broadly, our study aimed at bridging the gap between forest ecology and horticulture.
... It is predicted that the climatic optimum of this species in Europe will shift northward, and that it might actually become invasive in the north, while in the southern part of Europe it will be threatened due to its susceptibility to frost injury and drought (Paź-Dyderska et al., 2021). Vitasse et al. (2018) pronounced in their results that frost risk needs to be considered carefully when promoting the introduction new varieties of fruit trees to warmer and drier climates or when considering new plantations at higher elevations. Chmielewski et al. (2018) stated in their study the importance of reliable phenological models which not only work for current but also for changed climate conditions and at different sites. ...
Strength and direction of the potential effect of climate change on walnuts is regionally specific (Gauthier and Jacobs, 2011) as climate change will probably affect the spatial distribution of the walnut. This paper evaluated the long-term phenological series (1961-2012) of the beginning of flowering, end of flowering and duration of flowering in walnut tree (Juglans regia) at two phenological stations located in different geographical locations of the Czech Republic but in the same climatic conditions (warm region). Phenological stages were analyzed in relation to growing degree days and to spring frosts occurrence. Onset of the beginning and end of flowering occurred earlier at Velké Pavlovice station (-2.1 and -1.3 days), and conversely occurred later at Doksany station (+1.8 and +1.0). Period of flowering shortened at Doksany station (-0.8 day) and prolonged at Velké Pavlovice station (+1.2 day). The occurrence of days with minimum air temperature < 0 °C during walnut tree flowering was more frequent at Doksany station (in total, 29 days) with absolute minimum value -5.5 °C. At Velké Pavlovice station 5 days with minimum air temperature below 0 °C were found during examined period with absolute minimum value -3.8 °C. The negative trend in number of frost days occurrence during flowering period was found at both stations. Pearson correlation coefficient between phenophase onset (and flowering period) and sums of growing degree days was stronger at Velké Pavlovice station, and the highest value was between period of flowering and temperature sums (0.782). The results confirmed our hypothesis of changes in phenophase onsets and duration of flowering including spring frosts occurrence according to west-east gradient (maritime climate-continental climate).
... Increased risk of late spring frost above 10% between the two analysed periods was found in 28% of the territory for fruits that bloom earliest (apricot and peach), 17% for cherries, plums, and berries, and 12% for late-blooming fruits such as apples, pears, and quinces. In several attribution studies, it has been found that the increased frequency of potentially harmful spring frosts is a consequence of climate change [39][40][41][42]. The intensity of timing of such frosts may not necessarily change, however, its impact on fruit trees increased due to the earlier end of dormancy and endodormancy periods caused by the periods of higher winter (or early spring) temperatures [43,44]. ...
Climate change, through changes in temperature, precipitation, and frequency of extreme events, has influenced agricultural production and food security over the past several decades. In order to assess climate and weather-related risks to fruit and grape production in Serbia, changes in bioclimatic indices and frequency of the occurrence of unfavourable weather events are spatially analysed for the past two decades (1998–2017) and the standard climatological period 1961–1990. Between the two periods, the Winkler and Huglin indices changed into a warmer category in most of the viticultural regions of Serbia. The average change shift was about 200 m towards higher elevations. Regarding the frequency of spring frost, high summer temperatures and water deficit, the most vulnerable regions in terms of fruit and grape production are found alongside large rivers (Danube, Sava, Great and South Morava), as well as in the northern part of the country. Regions below 300 m are under increased risk of high summer temperatures, as the number and duration of occurrences increased significantly over the studied periods. The high-resolution spatial analysis presented here gives an assessment of the climate change influence on the fruit and grapes production. The presented approach may be used in regional impact assessments and national planning of adaptation measures, and it may help increase resilience of agricultural production to climate change.
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 studied local variations in temperature from winter to spring, and interpopulation variations in leaf out phenology (the day and the temperature sum for budburst and leaf expansion) of Siebold's beech (Fagus crenata) canopy trees. We focused on local topographic variation associated with the late frost regime for the canopy trees using 5–10 years of in situ observation of the temperature at 12 sites and leaf out phenology of two populations inhabiting a basin (basin populations) and 4 populations inhabiting hillside slopes (hillside slope populations) in the Hakkoda Mountains, northern Japan. The late frost regime differed between topographies; late frosts occurred during warmer periods in the basin compared to hillside slopes. The basin populations exhibited a larger temperature sum for leaf out than the hillside slope populations, regardless of altitude, suggesting that local variation in the late frost regime is an abiotic factor causing local variations in leaf out phenology. The six studied populations exhibited earlier days and smaller temperature sum of budburst in years with longer chilling duration. However, the extent of phenotypic plasticity in the temperature sum was small for the basin compared to hillside slopes. The temperature sum of leaf expansion in the hillside slope populations also negatively correlated with chilling duration, whereas that of the basin populations responded in the opposite direction. The safety margin from the last frost differed between the topographies, but not that from the last fatal frost, suggesting local adaptation to the late frost regime in each habitat. We studied interpopulation variations in leaf out phenology of Siebold's beech canopy trees along topographic variation associated with the late frost regime. Our analyses of temperature, leaf out phenology, and their relationships for the populations inhabiting a basin and hillside slopes in the Hakkoda Mountains suggest that local variation in the late frost regime is an abiotic factor causing interpopulation variation in leaf out phenology within a region, such that the basin populations exhibit later leaf out than the hillside slope populations.
Global change outcomes for forests will be strongly influenced by the demography of juvenile trees. We used data from an extensive network of forest inventory plots in Europe to quantify relationships between climate factors and growth rates in sapling trees for two ecologically dominant species, Norway spruce and European beech. We fitted nonlinear regression models with annual radial growth measurements from ~17,500 trees in primary forests to investigate the sensitivity of individuals to temperature and measures of water supply. We controlled for multiple, potentially confounding factors, including ontogeny, resource competition and the deposition of anthropogenic nitrogen and sulphur. The growth potential of spruce was markedly elevated relative to beech, reflecting species-specific relationships with environmental drivers. Declining water availability more strongly limited productivity in spruce, while beech was notably tolerant of observed levels of moisture limitation. Warming promoted growth in both species, but growing season temperatures that exceeded thermally optimum conditions constrained wood production. We identified long-term positive trends in reconstructed annual rates of juvenile tree growth since the early 19 th century, likely driven by industrial-era warming. However, our findings suggest that sustained warming and more prevalent future drought may ultimately inhibit growth due to thermal thresholds and a differential tolerance of water stress. Consequently, global change factors may be expected to affect future species abundance patterns, biomass production, and the carbon sink capacity of forests in Europe.
Phenological shifts in response to changing climatic conditions is a key acclimation process for the persistence of perennial plants in temperate and boreal climates. The optimal time to leaf‐out is the result of an evolutionary process determined by the trade‐off between minimizing the risk of freezing damages and herbivory pressure while maximizing resource uptake to increase competitiveness against the other plants.
We quantified the penalty exerted by frost damage at the time of leaf emergence on plant development (reduction in leaf area, canopy duration and growth) over the potential gains without frost (increased biomass and non‐structural carbohydrate reserves), depending on when leaf‐out occurs. To this purpose, we exposed 960 saplings of four temperate deciduous tree species with contrasting cold hardiness to two frost intensities shortly after leaf emergence, which was artificially induced at four occasions to reflect the whole range of natural leaf‐out dates.
One year above‐ground biomass (AGB) increments following the frost revealed a clear ranking among the species depending on their strategy to cope with damaging frosts. Prunus avium (−41% of AGB‐increment compared to control saplings) resprouted from the stem base, Quercus robur (−62%) rapidly produced new leaves from dormant reserve buds, Fagus sylvatica (−98%) showed highest chlorophyll content in autumn and delayed senescence together with Carpinus betulus (−105%), which overcompensated NSC reserves after the growing season but showed highest mortality (up to 32%). In all species, NSC reserves recovered rapidly to control levels at the expense of growth.
The timing of leaf‐out (advanced and delayed artificially) significantly affected the performance and recovery (regreening and growth) of both frozen and non‐frozen saplings, with the lowest performance found at the most delayed leaf‐out date. We propose that the potential to recover from frost damages is an important component of a tree's performance, particularly at the juvenile stage. The ability to recover may become even more decisive in the future with the predicted increase of false springs in many extratropical regions.
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This chapter describes the impact of some nonbiotic factors on forest health in Europe during the past decades. Storms, floods, and fires, as well as anthropogenic factors, were taken into consideration as primary disturbances predisposing trees to biotic damage. Data and information on the main harmful factors in a few countries obtained since 1950 are presented. These damage agents negatively influence forest health, reducing the survival of trees, and lead to biomass losses. The consequences of abiotic stress for the tree in the final balance are reduced photosynthesis efficiency, weakened plant immunity, increased susceptibility to infections, reduced tolerance to fungi, and increased opportunities for polycyclic diseases. The impact of these abiotic environmental elements is further discussed in relation to climate change.
The southeastern interior of the Iberian Peninsula (Spain) is characterized by a complex orography, which determines a pronounced altitudinal gradient, significant slopes, and marked valleys with important temperature inversion processes. In this work, to analyze the yearly and seasonal evolution of minimum temperatures, six indicators related to minimum temperatures were used: the frost days (FD) and TNltm2 (-2°C), 10th temperature minimum percentile (TN10p), absolute minimum temperatures (TNn), average minimum temperatures (TNm), and cold spells duration index (CSDI). For this, the Spearman non-parametric statistical test was used to analyze data from a total of 22 meteorological stations (1950-2020), using a daily resolution of minimum temperatures.
Significant changes during the study period were revealed, especially between the 1960s and 1990s. In most cases, there has been a statistically significant increase in the minimum temperatures in the study area, except in the western (most mountainous) part, where the dynamics differed from the rest of the interior of the southeast of the peninsular. Nine large global teleconnection patterns were analyzed in relation to the average minimum temperatures in the study area. These are well-characterized indices for the northern hemisphere, which show a very high correlation of the average minimum temperatures with the temporal evolution of the global climate pattern of the East Atlantic (EA) index, especially in the Mediterranean region of the Iberian Peninsula, where it seems to have a very marked influence.
The vitality of Scots pine (Pinus sylvestris L.) is declining since the 1990s in many European regions. This was mostly attributed to the occurrence of hotter droughts, other climatic changes and secondary biotic stressors. However, it is still not well understood which specific atmospheric trends and extremes caused the observed spatio-temporal dieback patterns. In the Swiss Rhône valley, we identified negative precipitation anomalies between midsummer and early autumn as the main driver of sudden vitality decline and dieback events. Whereas climate change from 1981 to 2018 did not lead to a reduced water input within this time of the year, the potential evapotranspiration strongly increased in spring and summer. This prolonged and intensified the period of low soil moisture between midsummer and autumn, making Scots pines critically dependent on substantial precipitation events which temporarily reduce the increased water stress. Thus, local climate characteristics (namely midsummer to early autumn precipitation minima) are decisive for the spatial occurrence of vitality decline events, as the lowest minima outline the most affected regions within the Swiss Rhône valley. Mortality events will most likely spread to larger areas and accelerate the decline of Scots pines at lower elevations, whereas higher altitudes may remain suitable Scots pine habitats. The results from our regional study are relevant on larger geographic scales because the same processes seem to play a key role in other European regions increasingly affected by Scots pine dieback events.
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.
Plant ecologists have long been concerned with a seemingly paradoxical scenario in the relationship between plant growth and
climate change: warming may actually increase the risk of plant frost damage. The underlying hypothesis is that mild winters
and warm, early springs, which are expected to occur as the climate warms, may induce premature plant development, resulting
in exposure of vulnerable plant tissues and organs to subsequent late-season frosts. The 2007 spring freeze in the eastern
United States provides an excellent opportunity to evaluate this hypothesis and assess its large-scale consequences. In this
article, we contrast the rapid prefreeze phenological advancement caused by unusually warm conditions with the dramatic postfreeze
setback, and report complicated patterns of freeze damage to plants. The widespread devastation of crops and natural vegetation
occasioned by this event demonstrates the need to consider large fluctuations in spring temperatures a real threat to terrestrial
ecosystem structure and functioning in a warming climate.