Frost Intensity Research Articles

Future changes in agrometeorological extremes in the southern Mediterranean region: When and where will they affect croplands and wheatlands?

Climate change and extremes are increasingly threatening food security, especially in the Global South. Here, we examine how croplands and wheatlands of the southern Mediterranean region could be affected by projected changes in agrometeorological extremes over the 21st century. We use 17 bias-corrected climate models from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) to identify potential trends and assess the time of emergence of significant changes in agrometeorological extremes under the Shared Socioeconomic Pathway (SSP3–7.0). We note that simulated historical trends in agrometeorological extremes closely match observed trends, here derived from ERA5land, over croplands. Our analysis of CMIP6 projected scenarios reveals a consistent rise in heat intensity, drought intensity, and the frequency of compound dry and hot (D5/H95) days. While a reduction in frost intensity, combined with fewer wet and cold (W95/C5) and dry and cold (D5/C5) events offer some mitigation potential, concerns about water scarcity due to heightened heat and drought stresses may overshadow these benefits. These changes in agrometeorological extremes are projected to emerge in the near- and mid-term future (by 2030 and 2050). We also note that the projected decreases in cold extremes affect smaller agricultural regions than the increases in extreme heat. We find higher likelihoods of negative agrometeorological impacts over croplands and wheatlands throughout the 21st century, which could significantly challenge crop yields and agricultural sustainability. Without proactive adaptation and mitigation strategies, food security could come increasingly under threat in a changing climate in the southern Mediterranean region.

Climate warming may accelerate apple phenology but lead to divergent dynamics in late-spring frost and poor pollination risks in main apple production regions of China

Frost exposure and poor pollination are great challenges for the cultivation of perennial orchard systems such as apples, whose adaptive capacity to climate impacts is limited. Unfortunately, such climatic risks remained largely unexplored due to the complexity in future climate predictions, uncertainties in apple phenological simulations, and difficulties in quantifications of risks of late-spring frost and poor pollination. Here, focusing on the main apple production Sub-regions I–IV (i.e., the Loess Plateau, the Bohai Bay, the Southwest Cool Highland, and Xinjiang) in China, we used an ensemble of seven phenological models to estimate changes in apple first flowering and fruit-setting. Based on phenological sensitivity window proposed, we evaluated the late-spring frost risk and climatic risk of poor pollination based on two individual indices developed for these two kinds of meteorological risks. The phenology model ensemble was driven by climatic data derived from an ensemble of 27 global climate models (GCMs) from CMIP6 to simulate apple phenology in two periods of 2021 − 2060 (Near Future) and 2061 − 2100 (Far Future) under two climate scenarios of SSP245 and SSP585. Model ensemble could largely improve phenology prediction accuracy. Our results also confirmed the general earlier occurrence of apple phenological stages and the shortening of phenological sensitive windows. The first flowering advanced about 0.19 − 0.32 d∙y-1 and fruit-setting advanced about 0.24 − 0.47 d∙y-1. Although the shortening of phenological sensitivity window might decrease frost frequency in some regions and reduce the general risk of late-spring frost (e.g. in Sub-region II), the increase of frost intensity could offset this kind of alleviation and even exacerbate frost risks in Sub-regions I and IV. Finally, except for Sub-region III and a few sites in Sub-regions I and IV, shifts in climatic risks of poor pollination in spatial contrasts were lower than late-spring frost risk. This highlighted late-spring frosts would be more possibly the reason for apple yield or quality losses than the unfavorable climatic pollination conditions under climate change. Model ensemble provides a realistic assessment for quantifying future risks of late spring frost and poor pollination in apple production systems, and helps to identify urgent meteorological risks and provide options for apple production systems in response to climate change.

Association of frost injury with tuber yield components in potato (Solanum tuberosum L.)

1In north-western and west-central sub-tropical plains of India, frost is known to influence the potato productivity by 10-50% depending upon intensity of frost and crop age. Information on frost tolerance is limited in sub-topical plains (Kang et al. 2007, Luthra et al. 2007) and association of frost injury with tuber yield components is lacking in potato. The tuber yield being complex polygenic trait is determined by interactions among various genetic as well as environmental factors. The genetic parameter gives an idea of the genetic advance to be expected from selection for a character (Johnson et al. 1955). Association among different characters helps in selection of better plant type.

The effect of climate change on spring frosts and flowering of Crataegus laevigata – The indicator of the validity of the weather lore about “The Ice Saints”

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 and2.0 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.

Evaluating late spring frost risks of apple in the Loess Plateau of China under future climate change with phenological modeling approach

Changes in apple phenology associated with climate change have attracted extensive attention. However, it is poorly known whether the phenological dynamics responding to climate change would increase the severity and frequency of frost in apple trees. Here, we investigated the variation of phenophase (budburst and fruit-setting) and the frost risk for apple trees in the Loess Plateau combined with phenology models driven by Global Climate Models (GCMs) under two emission scenarios (SSP2-RCP4.5 and SSP5-RCP8.5 for two time periods 2050s and 2090s, respectively). The results showed that apple budburst and fruit-setting are expected to be advanced to varying degrees, but the rate of advance is decreasing (budburst 0.04–0.14 d∙y−1, fruit-setting 0.12–0.22 d∙y−1). The combinations of high emission scenarios and ‘far’ time periods (SSP5-RCP8.5, 2090s) in budburst and fruit-setting advance larger than conservative emission scenarios and ‘near’ time periods (SSP2-RCP4.5, 2050s). Furthermore, although frost frequency is expected to decrease about 0.09–0.36 d under both SSP2-RCP4.5 and SSP5-RCP8.5, frost intensity tends to increase about 0.004–0.008 °C·d−1 (except SSP5-RCP8.5, 2090s). Due to the different directions of changes in frequency and intensity of frost under future time periods, overall frost risk showed regional differences. The unchanged or decreased frost risk distributed in the northern and southern areas of the study areas, while the increased frost risk mainly distributed across the central areas of the study areas. Finally, the advancement of two phenophase was disproportionately related to frost risks in the geographic distributions. Areas with large advance in phenophase were themselves expected to be at greater frost risk. Our findings will help to promote local preventative interventions for reasonably reducing the risk of late spring frosts in future climate warming scenarios.

Effects of freeze-thaw cycles on soil arthropod in the permafrost region of the Great Hing'an Mountains, Northeast China

A laboratory experiment was conducted to investigate the impacts of freeze-thaw intensity (-5-5 ℃, -10-5 ℃) and frequency (1, 5, 10, 15 times) on the community structure of soil arthropod in permafrost zone, Great Hing'an Mountains with the 5 ℃ as control. A total of 4198 individuals of soil arthropod were extracted, belonging to 4 classes, 9 orders, 24 families and 33 genera. The results showed that the number of individuals and groups of soil arthropod decreased significantly in the treatment with high frost intensity (-10-5 ℃), while the individuals of some taxa increased in the treatment with low frost intensity (-5-5 ℃) after the first freeze-thaw incubation. The group number, Margalef index and Shannon index decreased with the increases of freeze-thaw cycling times in low frost intensity treatment, while did not change regularly in high frost intensity treatment. Larva stage was a kind of survival strategy for arthropod to resist low temperature stress, with Acari showing stronger cold tolerance. Different responses of soil arthropod to freeze-thaw cycles, synergistic effect among species and soil environment were factors affecting the structure of soil arthropod community. This study could provide scientific data and theoretical basis for the research and conservation of soil arthropod diversity in the permafrost zone in mid-high latitudes.

Ground Frosts in Poland in the Growing Season

The ongoing climate warming affects, among others, and the variability of thermal conditions in spring and autumn are resulting in earlier dates of the beginning and end of the growing season. The present paper provides detailed characteristics of the phenomenon of ground frosts, addressing the question of whether the risk of frost-related damage in the extending growing season is still present. The assessment of temporal and spatial distribution of ground frosts (5 cm above ground level-AGL) in Poland in the thermal growing season (AT > 5 °C) was conducted on the basis of the results of air temperature measurements at 5 and 200 cm a.g.l. obtained from 52 station of the Institute of Meteorology and Water Management—National Research Institute for the period 1971–2020. The thermal growing season was calculated using the method by Gumiński. The following were calculated: the dates of the occurrence of ground frosts in spring and autumn, duration of the frost-free period, the number of days with frosts of various intensity, according to years, ten-day period and days in a year together with trends of change. The conducted analysis demonstrated that the number of days with frosts in the thermal growing season in the multiannual period under analysis (1971–2020) does not show any statistically significant changes. It was found that in the thermal growing season, the average number of days with ground frosts in Poland amounts to 28 and ranges in spring from 15 to 22, and in autumn from 8 to 12. Most frequently, approx. 49%, slight frosts are recorded, followed by moderate (29%), severe (15%) and very severe (7%). A positive effect of water reservoirs on decreasing the frequency and intensity of frosts, as well as sporadic occurrence of the phenomenon in the second half of June were demonstrated. Statistically significant earlier dates of disappearance of frosts in spring, later dates of occurrence in autumn and the lengthening of the frost-free period from approximately 2 days in the north-east of Poland to approximately 8.0 days over 10 years in the Pomerania region, create increasingly more favourable conditions for the cultivation of plants with high thermal requirements in Poland.

Disentangling the effect of topography and microtopography on near-ground growing-season frosts at the boreal-temperate forest ecotone (Québec, Canada)

Permanent landscape attributes such as topography (elevation [m]) and microtopography (local variation in elevation [cm]) can increase the risk of cold air drainage down-slopes and in microtopographic depressions, causing important temperature gradients that generate localized growing-season frosts. Since most studies on growing-season frosts are restricted to the northern parts of the boreal forest or to mountainous areas, their negative consequences on tree productivity at the boreal-temperate forest ecotone is often ignored. We quantified the intensity and probability of growing-season frosts at the boreal-temperate forest ecotone in regard to topographic and microtopographic landscape attributes, which were extracted from airborne LiDAR surveys. In situ air temperature was measured for two summers (2016–2017) with 252 temperature loggers installed in two 18-years-old spruce plantations established in both temperate and boreal mixedwood forests. Growing-season frosts were more intense and probable at the boreal mixedwood forest site compared to the temperate forest site. Still, at both sites, when growing-season frost occurred, air temperature could vary by 4 °C along the elevation gradient of 15 m, often reaching sub-zero values at low elevation while reaching above-freezing values at high elevation. The importance of microtopography on the risk of sub-zero temperatures increased where frost events were less likely to occur such as at the temperate forest and at high elevation. Considering that growing-season frosts can considerably reduce tree productivity, the effects of both topography and planting microsite should be considered when determining where to establish plantations in the landscape and to determine suitable frost-free planting microsites within a plantation.

Soil frost affects stem diameter growth of Norway spruce with delay

Key messageA lack of snow cover and increased soil freezing may not only have short-term impacts on trees but longer-lasting lagged effects on radial growth.Soil temperature and soil frost intensity are affected by the depth of insulating snow cover and the timing of snowmelt which are predicted to change by climate warming. This may increase tree growth if there is less soil freezing or decrease growth if there is no insulating snow cover, but frost temperatures still exist. Previously, we showed that the changes in soil frost by snow manipulations in a ~ 50-year-old stand of Norway spruce [Picea abies (L.) Karst.] in eastern Finland in two winters (2005/2006 and 2006/2007) led to short-term changes in physiology, morphology, and the growth of the shoots and roots. The treatments were: (1) control with natural insulating snow accumulation and melting; (2) snow removal during winter; and (3) snow removal in winter and insulation at the top of the forest floor in late winter to delay soil thawing. In this study, we examined the lagged effects of those treatments by radial trunk increment cores during the nine-year recovery period after the termination of the treatments. Annual ring width index (AWI) was calculated for each year by normalization of the ring width in the respective year in proportion to the ring width in the last year (2005) before the treatments. No differences in AWI were found between the treatments before or during the snow manipulation period. However, differences started to appear 1 year after the treatments were finished, became significant 4 years later in 2011 and lasted for 3 years. The radial increment was lower in the treatment with snow removed than in the control and in the treatment with insulation to delay soil thawing, but there were no differences between the latter two treatments. The results indicate that a lack of snow cover may not only have short-term impacts but longer-lasting consequences on the radial growth of trees. The positive effects of prolonged growing season by the increasing summer temperatures on forest growth predicted for the boreal region may therefore not be fully realised due to the negative effects of decreased snow cover and increasing soil freezing.

The influence of rootstocks on the sensitivity of flower buds to frost and the main properties of the ‘Carmen’ sweet cherry cultivar

The study examined the influence of five vegetative rootstocks on the flower bud sensitivity to frost during the period of ecological dormancy and the most important biological and pomological properties of the ?Carmen? sweet cherry cultivar. The ?Carmen? cultivar was grafted on the following rootstocks: ?Colt?, ?Gisela 5?, ?Gisela 6?, ?MaxMa 14? and ?Oblacinska cherry?. Winter frosts occurred during the ecological dormancy of sweet cherry trees. The intensity of frost was between -5?C and -7?C. The percentage of damaged and non-damaged flower buds per fruiting branch was determined by counting (50 flower buds per tree were taken from every part of the canopy and fruiting branches). The highest rate of damage of flower buds was in trees grafted on ?Oblacinska cherry?, an average of 77.2% of flower buds, while the lowest was observed in trees grafted on ?MaxMa 14?, an average of 24.3% of total flower buds. The significantly higher sensitivity of flower buds was found in spur fruiting branches compared to lateral fruiting branches. The fruits of the ?Carmen? cultivar had the earliest ripening on rootstocks ?Gisela 5? and ?Oblacinska cherry?. The ?Carmen? cultivar had the highest yield per tree on the ?MaxMa 14? rootstock, while the lowest yield rate was observed in ?Oblacinska cherry?, 5.4 kg and 1.9 kg, respectively. The highest mass of fruits was noticed in trees grafted on ?Gisela 6?, an average of 11.6 g, while the smallest was recorded in trees grafted on ?Gisela 5?- an average of 9.4 g.

Estimating Frost during Growing Season and Its Impact on the Velocity of Vegetation Greenup and Withering in Northeast China

Vegetation phenology and photosynthetic primary production have changed simultaneously over the past three decades, thus impacting the velocity of vegetation greenup (Vgreenup) and withering (Vwithering). Although climate warming reduces the frequency of frost events, vegetation is exposed more frequently to frost due to the extension of the growing season. Currently, little is known about the effect of frost during the growing season on Vgreenup and Vwithering. This study analyzed spatiotemporal variations in Vgreenup and Vwithering in Northeast China between 1982 to 2015 using Global Inventory Modeling and Mapping Studies Normalized Difference Vegetation Index (GIMMS 3g NDVI) data. Frost days and frost intensity were selected as indicators to investigate the influence of frost during the growing season on Vgreenup and Vwithering, respectively. Increased frost days during the growing season slowed Vgreenup and Vwithering. The number of frost days had a greater impact on Vwithering compared to Vgreenup. In addition, Vgreenup and Vwithering of forests were more vulnerable to frost days, while frost days had a lesser effect on grasslands. In contrast to frost days, frost intensity, which generally decreased during the growing season, accelerated Vgreenup and Vwithering for all land cover types. Changes in frost intensity had less of an impact on forests, whereas the leaf structure of grasslands is relatively simple and thus more vulnerable to frost intensity. The effects of frost during the growing season on Vgreenup and Vwithering in Northeast China were highlighted in this study, and the results provide a useful reference for understanding local vegetation responses to global climate change.

Olive oil characterization of cv. 'Arauco' harvested at different times in areas with early frost in Mendoza, Argentina.

'Arauco' is the only autochthonous olive cultivar from Argentina. Little has been reported so far regarding the management of this crop. In this work, variations in fruit and chemical characteristics of olives harvested over a wide range of dates and seasons are reported for this cultivar at two sites in Mendoza province in central west Argentina. During the harvest periods studied, fruit oil content on a dry basis remained at its maximum and was stable, but fruit oil content on fresh basis increased as water content decreased with delay in harvest date. Harvest date affected the maturity index of fruits as well as the oxidative stability and phenolic content of oil. In contrast, the fatty acid profile was not consistently affected by harvest date. Environmental conditions, mainly the occurrence and intensity of frosts, strongly influenced oil quality as well as maturity with delay in harvest date. The most appropriate harvest time to obtain Arauco oil with a high oil yield and good chemical quality was before mid-May and with maturity index lower than 2. Fruits harvested after mid-May were exposed to minimum temperatures between -1.2 °C and - 4.0 °C, producing oil with low phenolic compounds and oxidative stability. © 2019 Society of Chemical Industry.

Influence of Topography on Local Atmospheric Features in a Peri-urban Area of Bahía Blanca (Argentina)

The aim of the present work has been to identify the influence of topography on local atmospheric features at multiple temporal scales in a peri-urban area of Bahia Blanca (Argentina). Records were collected at two weather stations with a 35 m difference in elevation. As the area has been authorised for residential occupancy, knowing its hygrothermal distribution is considered essential for bioclimatic design. Topographical characteristics have an impact on local atmospheric features. In the lower areas of the valley records have shown lower temperature and higher humidity percentages than in the high areas. This difference increased during night hours and winter months. With clear skies, the thermal difference between both locations reached 4 °C in the hours before dawn in a winter’s day. The occurrence, intensity and duration of frosts were higher in the lower areas of the valley.

Plant rhizome positioning in the soil and under litter: Trade-offs of frost avoidance versus growth

Herbaceous plants can avoid frost stress by positioning their rhizomes deep in the soil or under plant litter, but this insulation may come at a cost of delayed emergence and reduced growth, particularly if frost stress is absent. We explored the strength of this trade-off for a range of rhizomatous plant species by conducting a suite of experiments to disentangle the direct effects of soil depth and litter cover on plant growth and survival from the effects of variation in frost exposure. Rhizome fragments were planted in the fall to experience winter conditions in the field at one of two depths with one of three litter treatments, and the latter treatments were combined with snow removal to increase frost intensity. For comparison, a second set of rhizome fragments that were overwintered in a growth chamber under mild conditions were exposed to the same soil depth and litter treatments in the spring. A third set of rhizomes was subjected to one of six freezing temperatures under controlled conditions then planted at a common depth in the spring. At the end of summer, all plants were harvested, and height and dry biomass were measured. For half the species studied, the depth and litter treatments reduced the severity of the snow removal effects on plant growth or survival, and the results of the controlled condition freezing experiment provided additional support for reduced freezing damage being the main driver of this response. However, deep soil positioning and litter cover were a cost for most species when they were planted in the spring. Overall, these results demonstrated that the benefits of soil and litter cover can outweigh the costs when frost is present; the balance of this trade-off could shift further with climate change and the resulting increase in soil frost caused by reduced snow cover in some regions.

Monitoring permafrost and periglacial processes in Sierra Nevada (Spain) from 2001 to 2016

AbstractOutside the Alps, the Sierra Nevada is probably the best studied European massif with respect to its past and current environmental dynamics. A multi‐approach research program started in the early 2000s focused on the monitoring of frozen ground conditions in this National Park. Here, we present data on the thermal state and distribution of permafrost and seasonal frozen ground in different sites across the highest areas of the massif. New results confirm the absence of widespread permafrost conditions, with seasonal frost prevailing above 2500 m. Small permafrost patches have been only detected in glaciated areas of the Veleta and Mulhacén cirques during the Little Ice Age at elevations of 3000–3100 m. The remnants of those glaciers are still preserved under the thick debris layer covering the cirque floors. Geomatic and geophysical surveying of a rock glacier existing in the Veleta cirque, together with the monitoring of soil temperature at different depths, have revealed permanently frozen conditions undergoing a process of degradation. In the rest of the massif, a seasonal frost regime prevails, even at the highest plateaus at 3300–3400 m, where annual soil temperatures average 2.5°C. The monitoring of soil temperatures in other different periglacial features has also revealed positive average values ranging between 2°C (inactive sorted‐circles) and 3–4°C (inactive and weakly active solifluction lobes). Consequently, we conclude that the present‐day climatic regime does not allow the existence of permafrost in the Sierra Nevada, and environmental dynamics is controlled by the intensity and duration of seasonal frost in the ground.

Characteristics of Frost Days in the Mountain Regions of Georgia

Based on observational data from 25 weather stations for the period of 1936–2013, the statistical structure, intensity, and duration of frosts as well as the dynamics of the number of frost days in the mountain regions of Georgia are investigated. The continuous duration of frosts, the time of the occurrence, the frequency of different gradations of the number of frost days, and the regularities of their long-term variations are revealed.

Frost tolerance of six seed orchards of Acacia mearnsii (black wattle) and the effect of developmental stage and tree size on frost hardiness

ABSTRACTFrost damage is the most important abiotic risk in Acacia mearnsii (black wattle) plantations in South Africa. Current A. mearnsii planting stock cannot tolerate temperatures below −4°C, and therefore there is an urgent need to develop frost-tolerant seed. This study investigated the frost hardiness of seedlots from six South African A. mearnsii seed orchards located at altitudes of 1120–1458 m asl and latitudes of 26.7–29.8°S that were established with cold-hardy Australian provenances and/or local landraces from cold sites. Frost damage was assessed in four field trials established on two different dates in 2015. Three sites experienced extensive frost events, with frequency and intensity varying among sites. Minimum temperatures ranged from −6.4°C to −7.7°C across sites. The seedlot from the coldest, highest altitude orchard showed superior frost hardiness to other seedlots from lower altitude and warmer orchards of similar genetic origin. Thus, site climatic characteristics are important for the development of cold hardiness in A. mearnsii seed orchards. Frost hardiness in young A. mearnsii trees was significantly related to age and tree size. At four months of age, trees were highly susceptible to frost damage irrespective of tree size and orchard origin (60–71% frosted trees). Frost hardiness increased with age and was very high at c. nine months across orchards (1–8% frosted trees at one site and 0–2% at another site). At nine months, although the extent of frost damage was low, this was inversely related to tree size. The percentage of trees that recovered from frost damage also increased with age of frost damage, this being 21% at the site frosted at four months of age and 65–67% at the sites frosted at nine months of age. Finally, there were no differences in tree growth at 14 months suggesting that, unlike cold hardiness, the differences in environment between the orchards did not affect the growth performance of the offspring.

Unchanged risk of frost exposure for subalpine and alpine plants after snowmelt in Switzerland despite climate warming.

The length of the snow-free season is a key factor regulating plant phenology and shaping plant community composition in cold regions. While global warming has significantly advanced the time of snowmelt and the growth period at all elevations in the Swiss Alps, it remains unclear if it has altered the likelihood of frost risk for alpine plants. Here, we analyzed the influence of the snowmelt timing on the risk of frost exposure for subalpine and alpine plants shortly after snowmelt, i.e., during their most vulnerable period to frost at the beginning of their growth period. Furthermore, we tested whether recent climate warming has changed the risk of exposure of plants to frost after snowmelt. We analyzed snow and air temperature data in the Swiss Alps using six weather stations covering the period 1970-2016 and 77 weather stations covering the period 1998-2016, spanning elevations from 1418 to 2950m asl. When analyzed across all years within each station, our results showed strong negative relationships between the time of snowmelt and the frequency and intensity of frost during the most vulnerable period to frost for subalpine and alpine plants, indicating a higher frost risk damage for plants during years with earlier snowmelt. However, over the last 46years, the time of snowmelt and the last spring frost date have advanced at similar rates, so that the frequency and intensity of frost during the vulnerable period for plants remained unchanged.

Research on Trends in Extreme Weather Events and their Effects on Grapevine in Romanian Viticulture

The aim of this work was to investigate the frequency and intensity of extreme weather events in various centers from Romania’s viticultural regions: winter frost, extreme temperatures during the growing season and summer droughts. Winter frost damaging the vine is a significant risk to grape production, mainly in the plains and lowlands to the foothills. The frequency of winter frost damaging the vine has increased during the last decades, in the context of climate change. Also, there has been found a significant increase in the number of hot days (Tmax > 30°C) and very hot days (Tmax > 35°C). The evolution of these extreme events was followed in Craiova, Constanta, Bucharest, Timisoara, Cluj-Napoca, Oradea and Iasi, between 1977 and 2015. The long term study (18 years) conducted in the experimental plantation of the University of Agronomic Sciences and Veterinary Medicine Bucharest revealed their influence on vine. During the last two decades, there has been registered a trend of increasing the frequency and intensity of winter frost, damaging vine (Tmin < -20°C), heat waves (number of days with Tmax > 30°C and > 35°C) and droughts that adversely affect viticulture, production and quality of grapes and wine. The highest warming trends were observed for northern viticultural regions (Transylvania and Moldavia) and for the seaside. Although the intensification of heat waves increases sugar accumulation in the berries, they trigger a significant reduction in grape production and in titrable acidity, requiring corrections and resulting in unbalanced wines. Meanwhile, droughts trigger production decrease. To avoid negative effects on vine, it is necessary to take measures, both on a short, medium and long term.

THE INFLUENCE OF TERRAIN ALTITUDE, SLOPE EXPOSURE AND SLOPE DEGREE ON PLANT SPATIAL DISTIRIBUTION

Article represents the state-of-the-art review of the literature considering influence of a relief on a spatial distribution of separate plants and vegetable communities. The relief is the ecological factor exerting indirect impact on a vegetable cover due to redistribution of heat, light and moisture. The author allocated ecologically significant elements of a relief – district height above sea level, an exposition of a slope and the steepness of a slope. Explicitly influence of height of the district above sea level on different forms of a relief – a macrorelief, a mesorelief, and a microrelief are considered. It is noted that in mountain systems vegetation it is more rich and more various than vegetation of plains that is caused by large variety of soil climatic conditions in mountains. Height of separate belts and a set of species of plants in them depend on the mountains latitude. Fluctuation of temperature gradient concerning the heights, seasons, and slopes of different exposition is very large. The mesorelief and microrelief caused the redistribution of heat and moisture, and also nutrients in the soil. For such forms of a relief the altitude change of a vegetable cover is extremely poor. In the conditions of meso - and a microrelief there is an increase in fluctuation of temperatures, intensity of frosts, duration of the frost-free period that generally influences the development of plants, their abundance and spatial distribution. Radiation level, winter distribution of snow and speed of wind depend on slope exposure. On slopes of different exposures some natural changes of air and soil temperature are observed. Exposure of slopes are of great importance for the life cycle of plants. Influence of various slope exposures is reflected in structure of vegetation on all the forms of a relief. Distinctions in soil temperatures on the slopes with various exposures also affect air temperature that is reflected in character of vegetation, structure of flora, dynamics of vegetation development and morphology of plants. Temperature of the soil and ground air layer, thickness of snow cover, size of daily amplitude of temperature, power of a soil profile, intensity of an erosion depends on the degree of slope. The degree of slope influences the specific structure and structure of phytocoenosis, emergence the petrophylous bush species, semi-low shrubs and grassy plants, formation of ecological, genetic and altitudinal zones of vegetable communities.