Risk Of Frost Damage Research Articles

Genetic control of intra-annual height growth in 6-year-old Norway spruce progenies in Latvia

Coupling growth with periods of favourable weather conditions minimizes risks of frost damage and maximizes annual height increment. The phenology of the formation of height increment is therefore a trait related to the adaptability of trees to annual weather fluctuations. Strong genetic control of the timing of the onset and cessation of shoot elongation has been reported for Norway spruce, but little is known about its fluctuations that occur during the growth period. The strength of the genetic control of the height growth rate was assessed for young (6 years old) Norway spruce progenies originating from six open-pollinated stands from two local provenance regions. In 2010, the length of the growing period for the studied trees was ca. 60 days. Trees from the more continental provenance region, which had later onset and cessation of height growth (by ca. 2.5 days), exhibited slightly lower increments (by ca. 1%). Accordingly, the provenance region had a significant effect on height growth at the beginning and end of the growing period. Nevertheless, considerable genetic control of the growth rate was found throughout the entire growing period (particularly at the beginning and cessation, ha2 ≥ 0.20), except for a week-long interval around mid-summer (ha2 = 0.07). Similarly, the coefficient of additive genetic variation suggested that breeding could be applied for the improvement of height growth intensity throughout the season. The phenotypic correlations between weekly growth rates and tree height (before growth) were mostly non-significant, suggesting varying mechanisms of control, hence possibility for simultaneous improvement of the traits by breeding.

Canopy damage by spring frost in European beech along the Apennines: effect of latitude, altitude and aspect

Late spring frost plays a major role in the structure and function of forest ecosystems with potential consequences on species distribution at both local and regional scales. Paradoxically, in a warmer world the incidence and impact of frost is increasing because of earlier leaf unfolding and flowering as a response to warmer temperatures. In this regard, European Beech (Fagus sylvatica L.), a native tree species widely distributed in European forests, is considered particularly sensitive to changes in spring temperature regimes associated with climate change and thus especially subject to the risk of frost damage. Although several studies concerning F. sylvatica frost damage have been conducted in northern and central Europe, no extensive studies are available for the southern part of its range, i.e. central and southern Italy as well as Greece.In this paper the effect of a late spring frost occurring at the end of April 2016 is extensively documented with high spatial detail all along the Apennine Chain through satellite image data. Three different remote-sensing greenness indexes, namely the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and the greenness index (GI) derived from Landsat-8 satellite images acquired from May to July in the years 2014, 2015, and 2016 at a spatial resolution of 30 m, were used to gauge the spatial response of common beech forests to this late frost event with relation to latitude, altitude and slope exposure. Frost damage was evaluated as a difference (Δ) of NDVI, GI and EVI between the mean of years 2014 and 2015 (i.e. MRY, mean of reference years), and 2016 (i.e. FEY, frost reference year). The three satellite remote-sensing indexes were efficient at detecting leaf damage with detailed spatial resolution and proved consistent with one another.The greatest damage occurred in the middle altitudinal range between 1500 and 1700 m a.s.l. with a decreasing trend toward both lower and higher elevations due to warmer temperatures below, and delayed phenology above. Exposure also influenced frost injury, with south-facing slopes of the mountain more damaged than the north. This difference was due to earlier spring leaf phenology of southern beech trees in response to a greater heat sum in the warm weeks preceding. Less damage in the northern Apennines is consistent with the spatial extent of minimum freezing temperatures. To sum up, frost damage is strongly related to site-specific conditions, i.e. on the one hand to minimum temperatures, and on the other to the phenological stage of the trees involving both altitude and exposure. Hence focusing on detailed sub-regional studies can be helpful for predicting future consequences of climate change on forests.

Protection against radiation frost damage of sweet cherries in the bloom stage by use of rain covers

Covering systems are used in sweet cherry orchards to avoid fruit cracking and rotting damage during rains. An additional advantage of using covers is the reduction of the risk of spring frost damage. The effect of rain covers on radiation frost damage was evaluated in covered and uncovered orchards during the bloom stage on 11 sweet cherry genotypes (‘Adelka’, ‘Aranka’, HL 13420, HL 15463 (Elza), HL 16165 (Felicita), ‘Helga’, ‘Horka’, ‘Justyna’, ‘Sandra’, ‘Skeena’, and ‘Sylvana’) in spring 2016 in Holovousy, Czech Republic. During the tree flowering period (full bloom stage; BBCH 65), the minimum temperatures subsided below 0°C for six sequential nights in the uncovered orchards (April, 24: -1.6°C; 25: -3.3°C; 26: -1.3°C; 27: -0.8°C; 28: -2.0°C; 29: -2.0°C), and for five sequential nights in the covered orchard (April, 25: -2.0°C; 26: -0.9°C; 27:-0.3°C; 28: -1.0°C; 29: -0.7°C). Frost damage appeared in both evaluated orchards (covered and uncovered). Less severe damage was recorded in the cultivars from the covered orchard than in those in the uncovered orchard. The highest differences in the degree of damage between the uncovered and covered cultivars were recorded in ‘Sandra’ (34% damage in uncovered orchard; 5% damage in covered orchard), ‘Skeena’ (33% damage in uncovered orchard; 11% damage in covered orchard), and ‘Adelka’ (31% damage in uncovered orchard; 19% damage in covered orchard). On the contrary, the lowest difference was recorded in the hybrid cultivar HL 13420 (8% damage in uncovered orchard; 5% damage in covered orchard). Other genotypes demonstrated around 10% differences in damage severity between covered and uncovered orchards. Covering cherry orchards has a positive effect by increasing the temperature by approximately 1-2°C, resulting in decreased frost damage occurring during the bloom stage under the prevalent climatic conditions of central Europe.

Investigation of thermal, moisture, and mechanical properties of wet and dry fired clay materials to assess frost damage risk

Frost action is one of the main causes for deterioration of porous building materials under defined hygrothermal conditions. For an accurate assessment of the frost damage risk under various environmental conditions, thermal, moisture, and mechanical properties should be considered; the hygrothermal properties affect the distribution of temperature and amount of frozen water in the material, whereas the mechanical properties are necessary to predict deformation and damage. Moreover, the dependency of these properties on the moisture content should be understood. Therefore, in this study, thermal, moisture, and mechanical properties of wet and dry fired clay materials were measured. The fired clay materials were sintered at two different temperatures, 1000 °C and 1100 °C (samples T10 and T11, respectively) for comparison. The measured thermal and mechanical properties are considerably different in the wet state compared to the dry state. Freeze–thaw tests were conducted to investigate the relation between the material properties and the frost resistance under a simple experimental condition. As expected, based on the pore structure and obtained mechanical properties, T10 exhibited lower frost resistance than T11 in the freeze–thaw test. Finally, frost damage risk was assessed under various environmental conditions based on the obtained hygrothermal and mechanical properties.

Probabilistic assessment of the impact of material properties on the risk of frost damage in masonry constructions

Historically valuable buildings often contain a huge energy saving potential due to their current lacking thermal performance of the building envelope. Next to this, unfortunately insulation measures, which normally occur at the inside, induce a decrease in the temperature and drying potential of the structure which results in a risk for frost damage. To validate this risk Heat, Air and Moisture simulations are a valuable tool. Heritage facades often consist of masonries, which are known to have a complex hygrothermal behaviour. Therefore nowadays a homogenization of the masonry, for example to a homogenous brick wall, is often assumed to save computational time. Nevertheless these homogenizations, which include neglecting mortars, can have a drastic impact on the hygrothermal behaviour of masonries. Hence this study compares the impact of basic material parameters for the brick, pointing mortar and bed mortar of a masonry separately under a constant indoor and outdoor climate based on probabilistic simulations. The evaluation is done for three frost related criteria. Generally, the main impact parameters for the one and a half brick construction are found to be quite similar for interior insulated and not insulated cases but diverse between the chosen criteria.

Adaptability and Growth of a Fast-Growing <i>Neolamarckia cadamba</i> (Roxb.) Bosser Clone in the South Subtropical Region of China

The present study investigated the adaptability and growth of a fast-growing clone (BN1) of N. cadamba planted as short-rotation plantation species in the south subtropical region of China, using 17 sampled sites representing different environments, planting models and ages, and local weather station temperature records. BN1’s growth characteristics were further compared with the most productive eucalypts planted nearby. The survival of BN1 seedlings raised and transplanted with tissue-culture micro-cuttings was >94.0% in the 1st year, and the percentage of the effective trees with diameter at breast height ( Dbh ) ≥ 8 cm was >71.0% over 30-month old. Most of the sampled sites and trees were susceptible to low-temperature or frost injury in the 1st winter, with average damage index ( Id ) ranging from 0.1 to 2.6. Some sites/trees were infected by caterpillar or borer pests, but the damage was neglectable. The injured trees quickly sprouted out leading shoots and recovered their growing vigor from low temperature or insect damage. Temperature factors were closely related to Id (P °C) with risk of significant frost damage on BN1 trees; one site (No. 9) was not suitable with frequent and heavy cold damage ( Id =2.6 ). BN1 grew extremely fast, with average diameter at breast height ( Dbh ) ranging from 14.5 - 20.3 cm and average tree height ( Ht ) from 12.3 - 16.0 m at 54-month old, and Dbh from 17.8 - 22.7 cm and from 14.4 - 15.9 m at 66-month old, over different sites/soils and planting models. Peak for both Dbh and Ht appeared in the 2nd year, but after 6-year old for average individual tree volume ( Vt ). BN1 was faster in Dbh at most sites but slower in Ht at all sites than eucalypts compared. Some sampled sites of BN1 performed similarly as or obviously better than most productive eucalypts in stock volume (Vs). With properly planting density, tending and rotation, BN1 could be expected to outperform fast-growing eucalypts in terms of Dbh , Vt and Vs, and to produce all diameter grades of timbers if the rotation age is extended beyond 8 to 9 years. Discussion was also given to potential silvicultural models, risks and limitations of planting BN1 and other superior N. cadamba varieties.

Survival, growth and cold hardiness tradeoffs in white spruce populations: Implications for assisted migration

Human assisted movement of reforestation stock poleward or upward in elevation has been proposed as a tool to address climate change in regular reforestation programs. However, moving warm adapted seed sources to colder environments could carry the risk of frost damage if seed sources are moved too far. Here, we assess genetic differentiation in growth potential, survival and cold hardiness of a wide-ranging tree species, white spruce (Picea glauca [Moench] Voss). We use data from a 34-year-old common garden experiment planted in the approximate center of the species range. Cold hardiness was negatively related to growth and positively to survival. Generalized additive models identified mean coldest month temperature and latitude (as a proxy for the day length regime) as an exceptionally good predictor for the onset of cold hardiness (R2adj = 0.91). The results suggest that day length, an environmental factor that is not influenced by climate change, is an important factor controlling the timing of the onset of hardiness. Survival was only moderately well predicted, primarily by precipitation of the provenance origin (R2adj = 0.36) indicating that other adaptive traits besides cold hardiness should be considered in assisted migration prescriptions. Survival of seed sources appears primarily compromised when transplanting sources from wet origins to a dry location. Nevertheless, acceptable migration distances without significant tradeoffs were up to 500 km north and 1500 km west towards a central planting location.

Divergent trends in the risk of spring frost damage to trees in Europe with recent warming.

Frost events during the active growth period of plants can cause extensive frost damage with tremendous economic losses and dramatic ecological consequences. A common assumption is that climate warming may bring along a reduction in the frequency and severity of frost damage to vegetation. On the other hand, it has been argued that rising temperature in late winter and early spring might trigger the so called "false spring", that is, early onset of growth that is followed by cold spells, resulting in increased frost damage. By combining daily gridded climate data and 1,489k in situ phenological observations of 27 tree species from 5,565 phenological observation sites in Europe, we show here that temporal changes in the risk of spring frost damage with recent warming vary largely depending on the species and geographical locations. Species whose phenology was especially sensitive to climate warming tended to have increased risk of frost damage. Geographically, compared with continental areas, maritime and coastal areas in Europe were more exposed to increasing occurrence of frost and these late spring frosts were getting more severe in the maritime and coastal areas. Our results suggest that even though temperatures will be elevated in the future, some phenologically responsive species and many populations of a given species will paradoxically experience more frost damage in the future warming climate. More attention should be paid to the increased frost damage in responsive species and populations in maritime areas when developing strategies to mitigate the potential negative impacts of climate change on ecosystems in the near future.

Hygrothermal assessment of internally insulated solid masonry walls fitted with exterior hydrophobization and deliberate thermal bridge

AbstractRelative humidity (RH) and temperature were measured in several solid masonry walls with embedded wooden beams, fitted with autoclaved aerated concrete (AAC) thermal insulation on the interior surface and exposed to a cool, temperate climate. The field study was based on the use of a 40‐feet insulated reefer container reconfigured with eight 1 × 2 m holes containing the solid masonry walls. The study investigated the influence of AAC thermal insulation on the interior side with a combination of exterior hydrophobization and a deliberate thermal bridge in front of the embedded wooden wall plate using a material with higher thermal conductivity. Validated HAM simulations were used to investigate the effect of controlling the indoor humidity, and how this would affect the theoretical risk predictions from the damage models. Experimental findings indicate that hydrophobization of solid masonry walls with internal insulation have both positive and negative effects on the moisture balance of the wall, in relation to moisture‐induced damage, and that a deliberate thermal bridge installed in front of the embedded wooden wall plate can reduce the moisture content in the wooden elements. Simulation findings indicate that a combination of exterior hydrophobization and decreased indoor moisture load can reduce the RH to acceptable levels in relation to moisture induced damage at the interface between existing wall and new insulation. No major changes were observed in relation to the risk of frost damage at the exterior surface.

Predicting future frost damage risk of kiwifruit in Korea under climate change using an integrated modelling approach

As the climate changes, increasing variations in environmental factors directly influence crop cultivation at different magnitudes over a broad range of local communities worldwide. As a result, there is an urgent need to develop local impact assessments and adaptation strategies for use at local, rather than national or global, levels. In this study, we predicted the future frost damage of kiwifruit in the Jeonnam province, Korea, as a case study for the local impact assessment of climate change. This study included a series of models that integrated both the biological responses of plants and the physical influences of climatic factors. First, potential changes in the suitable area for kiwifruit cultivation under a changing climate were simulated using downscaled high resolution (1 km) climate data. Through the development of a frost‐forecasting model and linking it to a kiwifruit phenology model, we also assessed the interaction of plant and climatic factors. Because of the warming climate, the last frost date in spring occurred 13.7 days earlier in average under climate change. Nevertheless, the potential risk of spring frost damage of kiwifruit continued to exist at a similar magnitude in the future. Additional study at the county level indicated that the date of bud burst is advancing even faster than the last frost date (approximately 1 day per every decade), resulting in the increasing risk of spring frost damage for kiwifruit through 2100. In this study, the local impacts of climate change on kiwifruit frost damage were assessed using the integrated modelling approach. As such, local policy makers and stakeholders will be able to prepare more realistic adaptation strategies to cope with upcoming threats in a changing climate.

Hygrothermal assessment of internally insulated brick wall based on numerical simulation

Massive walls exposed to external climate are characterized by low levels of thermal insulation. Unfortunately in many cases, due to the historic character of the building, the only possible way to improve their thermal insulation is the use of internal insulation. However, such solutions are associated with the risk of frost damage, mould growth or interstitial condensation. Calculations regarding the occurrence of these risks require complex calculation methods. Therefore, in the present work, the evaluation of the hygrothermal behavior of the internally insulated solid brick wall was performed based on the numerical simulations using the program WUFI Pro. Various material solutions of internal insulations, based on both synthetic and natural materials, were compared. The focus was on a particularly sensitive interface between the insulation and the original wall

Unprecedented risk of spring frost damage in Switzerland and Germany in 2017

Spring frosts are feared by farmers, fruit growers, and wine growers as they can cause significant damage to crops when they occur during the development of the plants. In the second half of April 2017, following a very warm period that had caused premature vegetation growth, a cold air mass from the Arctic penetrated central and western Europe, causing severe damage to natural and cultivated vegetation over broad areas. Here, we analyze how exceptional this event was in Switzerland and Germany in relation to the accumulated growing degree days (GDD), used as a proxy for plant phenology advancement. Although this damaging frost was not the latest on record in terms of calendar days, our results show that it was, in some regions, unprecedented in relation to the accumulated warmth during the preceding period, at least since the beginning of instrumental temperature records (1864). Our results also highlight how global warming has considerably increased the number of days with mean temperature above 5 °C in late winter and early spring, especially since 1970 (+ 16.8 ± 4.7 °C days decade−1). However, in spite of earlier spring phenology due to climate warming, our results suggest that the risk of damaging frost events to vegetation has remained unchanged over the last 150 years in lowlands of Switzerland and Germany, due to the concurring earlier occurrence of the last potentially damaging frosts (about − 20 days since 1864). Our analyses reveal therefore that the April 2017 damaging frost was a true outlier in terms of risk of frost damage to plants.

Frost Damage of Carinata Grown in the Southeastern US

Brassica carinata is an annual oilseed crop used for the commercial production of jet fuel. One of the challenges to commercialization of this crop in the southeastern United States has been frost damage. This 4-page fact sheet discusses symptomology and ways to minimize risk of frost damage to carinata. Written by Michael J. Mulvaney, Ramdeo Seepaul, Ian Small, David Wright, Silvana Paula-Moraes, Carl Crozier, Paul Cockson, Brian Whipker, and Ramon Leon, and published by the UF/IFAS Agronomy Department, May 2018. https://edis.ifas.ufl.edu/ag420

Seedling, planting site and weather factors affecting the success of autumn plantings in Norway spruce and Scots pine seedlings

Due to the lack of labor and the mechanization of planting work, seedlings should be planted during the entire period of unfrozen soil, from early spring to late autumn. In experimental studies, it is difficult to investigate all the risk factors related to different planting windows. In Finland, the winter of 2015–2016 was harsh for seedlings. First temperatures were above zero, then they suddenly dropped to <−30 °C without any protective snow cover. These conditions offered a good opportunity to study the success of autumn plantings and clarify which factors best predict the field performance of autumn planted conifer seedlings. In the survey, 22 regeneration sites planted with Scots pine (Pinus sylvestris L.) and 71 with Norway spruce (Picea abies (L.) Karst.) seedlings were inventoried in the summer of 2016. Scots pine seedlings were more sensitive, and the regeneration result was good only in a few sites. With Norway spruce, the results were better although both good and poor results were found. For Norway spruce, we modeled the probability of severe damage and leader growth damage separately for summer (July and August), September and October plantings. The most important factors affecting the probability of damage was the quality of the planting and the planting spot as well as the soil type. If a planting hole was open or a seedling was planted in a planting spot other than a mineral-covered mound, the risk of damage was high. In fine and course textured soils, as well as medium coarse soils with a high risk of frost heaving, the probability of damage was also high. Low precipitation after planting and during the following spring also increased the probability of leader growth damage. Planting in the summer and early September exposed seedlings to leader growth damage, especially when the seedlings were planted in sites with a high risk of frost damage in autumn and spring. The results indicate that the planting of Scots pine seedlings in the autumn should be avoided. Norway spruce seedlings can be planted even in October when the work quality is good and suitable sites are selected for plantings.

Potassium application alleviates grain sterility and increases yield of wheat (Triticum aestivum) in frost-prone Mediterranean-type climate

Frost is a major risk factor for grain production in Australian farming systems and appears to be increasing in severity and occurrence due to changing climate. In this study we assessed the role of potassium (K) and micronutrients in alleviating floret sterility (FS) and yield loss in wheat crops subject to frost. Field experiments with K application in 2015 and 2016 were conducted in frost-prone, low soil K fields in the grain belt of Western Australia. Following frost events the heads reaching anther dehiscence were tagged and FS was measured 5–6 weeks later. We also measured leaf K concentration, photosynthesis and antioxidant activity, and grain yield. In 2015 K supply decreased FS from 32% at nil K to 24% at 80 kg K ha−1. In 2016 the FS values varied from 30 to >95%. Although there was no effect of K on FS at extreme frosts (FS >95%), applying 20–80 kg K ha−1 reduced FS by 10–20% and increased yield by 0.2–0.4 t ha−1 at less severe frosts. The decrease in FS was associated with increasing leaf K concentrations in the range 1.5–2.6%, higher photosynthesis and less oxidative stress at anthesis, but K supply did not provide extra protection from frost damage at leaf K > 2.6%. Foliar micronutrients at booting and heading did not affect FS in either year due to adequate micronutrient levels in the topsoil. Improved plant K status can increase grain set and yields in wheat under frost, likely by maintaining physiological functions such as cell osmoregulation, plant photosynthesis and anti-oxidant systems. Plant K requirement in frost prone parts of the landscape is greater than in the areas with low risk of frost damage.

Urbanization may reduce the risk of frost damage to spring flowers: A case study of two shrub species in South Korea.

Regional warming, owing to urbanization, leads to earlier spring phenological events and may expose plants to hard freeze damage. This study examined the influence of urbanization on the risk of frost damage to spring flowers in South Korea from 1973 to 2015. For the analysis period, we categorized 25 cities into two groups: those showing rapid population growth (rPG) ≥ 200,000, including 13 cities, and those showing no or decreased population growth (nPG), including 12 cities. We then investigated the time from the last frost dates (LFDs) in spring to the first flowering dates (FFDs) for each group. The rPG group experienced significant spring warming of 0.47°C per decade, resulting in earlier LFDs and FFDs. For this group, the advancement of LFD was more rapid than that of FFD, and the days between these two dates increased from 0.42 to 0.47 days per decade, implying a reduced risk of frost damage. Spring warming and the advancement of FFDs and LFDs were relatively small for the nPG group, and the LFDs were rather delayed. Consequently, the days between LFDs and FFDs were reduced from −1.05 to −1.67 days per decade, indicating an increased risk of frost damage. The contrasting changes in the frost-damage risk between the two city groups can be attributed to distinct urban warming at night, which makes the LFDs substantially earlier in the rPG group. Therefore, this study suggests that the warming associated with urbanization may lessen the risk of spring frost damage to plants in rapidly growing urban areas.

Changing risk of spring frost damage in grapevines due to climate change? A case study in the Swiss Rhone Valley

Late spring frost is a severe risk during early plant development. It may cause important economic damage to grapevine production. In a warming climate, late frost risk either could decline due to the reduction in frost days and an advancement of the last day of frost or increase due to a more pronounced shift forward of the start of the active growing period of the plants. These possibilities were analyzed in a case study for two locations in the lower Swiss Rhone Valley (Sion, Aigle) where viticulture is an important part of agriculture. Twelve phenology models were calibrated for the developmental stage BBCH09 (bud burst) using measured or reconstructed temperature data for two vineyards in Changins (1958 to 2012) and Leytron (1977 to 2014) together with observed phenological data. The day of year (DOY) for BBCH09 was then modelled for the years 1951 to 2050 using the best performing phenology model in combination with ten downscaled and bias-corrected climate scenarios. A 100-day period starting with BBCH09 was defined, during which daily mean and minimum temperatures were used to calculate three frost risk indices in each year. These indices were compared between the periods 1961–1990 (reference) and 2021–2050 (climate change scenario). Based on the average of the ensemble of climate model chains, BBCH09 advanced by 9 (range 7–11) (Aigle) and 7 (range 5–8) (Sion) days between the two time periods, similar to the shift in the last day of frost. The separate results of the different model chains suggest that, in the near future, late spring frost risk may increase or decrease, depending on location and climate change projections. While for the reference, the risk is larger at the warmer site (Sion) compared to that at the cooler site (Aigle), for the period 2021–2050, small shifts in both phenology and occurrence of frost (i.e., days with daily minimum temperature below 0 °C) lead to a small decrease in frost risk at the warmer but an increase at the cooler site. However, considerable uncertainties remain that are mostly related to climate model chains. Consequently, shifts in frost risk remain uncertain for the time period considered and the two study locations.

Modeling uncertainty of statistical downscaling methods in quantifying the climate change impacts on late spring frost risk over Iran

Late spring frosts (LSFs) play a key role in the evaluation of climate suitability for agricultural and horticultural crop production and are considered to be one of the main components of food security. It is expected that future climate change will affect the occurrence of LSFs and its damages. In order to quantify these changes, this study aims to investigate the performance of two downscaling methods (SDSM and ANN), using two GCMs (general circulation model) data of HadCM3 (A2 and B2 scenarios) and CGCM3 (A1B and A2 scenarios). To this end, daily minimum temperature data (Tmin i ) of 50 meteorological stations located across the entire country were gathered and quality controlled for the period 1961 through 2010. The trend analyses of annual minimum temperature series showed a significant increasing trend of 0.3 °C per decade (α = 0.01). Both downscaling models were calibrated for the 40 years of 1961–2000 and the evaluation is conducted for the 10 years of 2001–2010. The Wilcoxon rank-sum and the Levene and bootstrapping tests were used for comparing and finding confidence intervals of averages and variances of downscaled daily minimum temperatures at each month. Results showed that, firstly, downscaling models’ performance in simulating averages is much better than variances. Secondly, SDSM simulates warmer summers and colder winters comparing ANN. Thirdly, the best and the worst results were achieved by ANN_CGCM3_A2 and ANN_HadCM3_B2, respectively. Finally, very low, moderate, high, and very high-risk zones for critical temperature of 0 °C and their areas at the historical period (1961–2010) and three future periods (2011–2040, 2041–2070, 2071–2100) were quantified and compared. Based on the results, SDSM simulated changes in the high and low frost risk zones more than the ANN model. However, since both Very High and No Frost risk zones will drastically change, SDSM results do not always indicate an increasing risk of frost damage. Moreover, the average of the area covered by “low-risk” zone will increase from 1.00% in the current period to 4.43% at the end of the century, and area of “very high-risk” zone will decrease from 8.2 to 4.7% at the same condition.

The risk of tardive frost damage in French vineyards in a changing climate

Tardive frosts, i.e. frost events occurring after grapevine budburst, are a significant risk for viticultural practices, which have recently caused substantial yield losses over different winegrowing regions of France, e.g. in 2016 and 2017. So far, it is unclear whether the frequency of late frosts events is destined to increase or decrease under future climatic conditions. Here, we assess the risk of tardive frosts for the French vineyards throughout the 21st century by analyzing temperature projections from eight climate models and their statistical regional downscaling. Our approach consists in comparing the statistical occurrences of the last frost (day of the year) and the characteristic budburst date for nine grapevine varieties as simulated by three different phenological models. Climate models qualitatively agree in projecting a gradual increase in temperature all over the France, which generally produces both an earlier characteristic last frost day and an earlier characteristic budburst date. However, the latter notably depends on the specific phenological model, implying a large uncertainty in assessing the risk exposure. Overall, we identified Alsace, Burgundy and Champagne as the most vulnerable regions, where the probability of tardive frost is projected to significantly increase throughout the 21st century for two out of three phenological models. The third phenological model produces opposite results, but the comparison between simulated budburst dates and observed records over the last 60 years suggests its lower reliability. Nevertheless, for a more trustworthy risk assessment, the validity of the budburst models should be accurately tested also for warmer climate conditions, in order to narrow down the associated large uncertainty.

The analysis of climatic indicators using different growing season calculation methods – an application to grapevine grown in Hungary

The precise knowledge of the beginning and the end of the growing season is necessary for the calculation of climatic indicators with evident effect on grapevine production. The aim of this study is to develop suitable methods on the basis of thermal conditions that can be used for calculation of the beginning, the end, and the length of the growing season for every single year. The two most accurate methods (5mid' and 'int') are selected using the root-mean-square error compared to the reference growing season values based on averaging the daily mean temperature for several decades. In case of the `5mid' method, the beginning (or the end) is the middle day of the first (or last) 5-day period with temperature not less than 10 degrees C. In case of the 'int' method, the beginning (or the end) of the growing season is the day after March 15 (or September 15), when the smoothed series of daily temperature using the monthly average temperatures of March and April (or September and October) exceeds 10 degrees C (or falls below 10 degrees C). As a next step, several climatic indicators (e.g., Huglin index and hydrothermal coefficient) are calculated for Hungary for three time periods (1961-1990, 2021-2050, and 2071-2100*) using the '5mid' and 'int' methods. For this purpose, the bias-corrected daily mean, minimum, and maximum temperature and daily precipitation outputs of three different regional climate models (RegCM, ALADIN, and PRECIS) are used. Extreme temperature and precipitation indices are also evaluated as they determine the risk of grapevine production. The spatial distributions of the indicators are presented on maps. We compare the indicators for the past and for the future using one-way completely randomized robust ANOVA (analysis of variance). Results suggest that changes of temperature conditions in the 21st century will favor the production of red grapevine and late-ripening cultivars. Furthermore, drought seasons will be longer and extreme high summer temperatures will become more frequent, which are clearly considered as high risk factors in grapevine production. Besides the negative effects, the risk of winter frost damage is expected to decrease, which is evidently a favorable change in terms of grapevine production.