YIELD SHORTFALL OF CEREALS IN UKRAINE CAUSED BY THE CHANGE IN AIR TEMPERATURE AND PRECIPITATION AMOUNT

Aim. To determine the trends in precipitation patterns, the precipitation productivity, and the cumulative impact of the change in air temperature and precipitation levels on cereal yield, including corn and spring barley, throughout the vegetation cycle stages. Furthermore, the examination of the alterations in the climate suitability, crop yield shortfall, and their speci ﬁ c characteristics within in the soil-climatic zones of Ukraine during 1981–2010 years Methods. In order to accomplish the outlined aims conventional and more speci ﬁ c research methods were used: 1) An analytical-synthetic approach – to examine the existing state-of-the art research; 2) A statistical approach – to assess the intensity and signi ﬁ cance of changes in agroclimatic conditions pertaining to crop cultivation; 3) A comparative analysis – to determine the speci ﬁ cities mentioned under 2) in soil-climatic zones of Ukraine and in different stages of plant development; 4) A climatic approach – to characterize precipitation levels and to evaluate their impact on crop productivity; 5) modelling – to assess the effect of changes in precipitation amounts on the productivity of corn and spring barley, to assess the cumulative impact of the variations in surface temperature and precipitation on climate productivity and yield shortfall of these crops; 6) application of abstract and logical method – to formulate the generalizations and draw conclusions based on the ﬁ ndings. Results. During the years 1981–2010, Ukraine experienced changes in precipitation patterns and increased air temperature throughout the vegetation cycle of corn and spring barley in different


INTRODUCTION
Climate change has a considerable effect on agricultural production and food safety in the world and requires effi cient solutions for their adjustment (Asseng et al, 2015;Lobell et al, 2011;FAO, 2021).Modelling and empirical research demonstrated that the observed climate changes led to signifi cant variability in many crops (Field et al, 2014;Challinor et al, 2014;Bassu et al, 2014;Lesk et al, 2016;Polevoy et al, 2007;Balabukh, 2017, Balabukh et al, 2021).It was determined that this effect depended considerably on geographic location and the crop involved.In northern regions of the world, where air temperature increased considerably in spring and summer, there was an increase in the duration of the vegetation period and its heat provision, the conditions for the cultivation of many crops became more favorable and probably would be improved in short-and middle-term (Darwin et al, 1995;Cuculeanu et al, 1999;Isik and Devadoss, 2006;Xuhui Wang et al, 2014Shrestha et al, 2013).Due to climate changes in these northern cool climate regions, there is generally an increase in crop yield, new varieties are introduced, the crop cultivation areas are expanded and there is a possibility to obtain increased yield (Wang et al, 2014).However, in southern warm climate regions of the world, negative consequences of the climate change on crops are much more signifi cant than the positive ones, and the tendency will accelerate with further temperature increase (Wang et al, 2014;Işık and Devadoss, 2006;Fishman, 2016).The increase in the recurrence and intensity of extreme weather phenomena, especially waves of heat and droughts, conditioned the shortage of moisture and nutrients, a decrease in the productivity and quality of cereals, reduced agricultural production and affected the food safety in the world (Parkes et al, 2018;Cammaranoa et al, 2019;Asseng et al, 2015;Lobell et al, 2011;FAO, 2021).In some countries, negative consequences of climate change get to such a scale that the decrease in the productivity of cereals cannot be compensated even with the application of modern technologies, the introduction of fertilizers and other factors (FAO, 2021).
The changes in air temperature affect the productivity and quality of grain much more than the variations in precipitation, especially if these changes are beyond the limits of the values, optimal for plant growth (Högy et al, 2013;Lobell, 2007).Increase in mean maximum air temperature during the vegetation period causes much more damage to crop productivity than increase in minimal temperature.This effect is more pronounced under precipitation defi ciency, especially when precipitation amount during the vegetation period is under 400 mm (Wang et al, 2014;Işık et al, 2006;Blanc, 2012).Precipitation has a considerable effect on the growth of crops and their productivity in dry land, as for example is the case for a large part of Ukraine.The impact of moisture on the productivity of crops is usually evaluated by the cumulative annual amount of precipitation or the amount of precipitation available during the vegetation period (Dmitrenko, 1973;Schipper et al, 2010).However, climate change also often induces re-distribution of precipitation both during the year and during the vegetation period which can substantially affect crop productivity (Balabukh et al, 2022).Understanding of the way, in which different climate factors interact and affect crop productivity during their vegetation cycle enables elaboration of effi cient agricultural adjustment strategies towards the effects of climate change (Porter et al, 2014;Schipper et al, 2019) The aim of this study was to determine the tendencies in changes in precipitation (amount and periodicity), the precipitation suitability and the cumulative impact of changes in air temperature and precipitation amount on the yield of crops, the change in the climate suitability, yield shortfall of crops and their specifi cities in the soil-climatic zones of Ukraine over 1981-2020 years.

MATERIALS AND METHODS
The effect of agrometeorological conditions on corn and spring barley productivity was evaluated using the hydrometeorological methodology of the so-called Weather-Yield model, developed by V.P. Dmitrenko, including the cumulative climate suitability coeffi cient S (T, R), which characterizes the impact of the air temperature (Т) and the precipitation amount (R) during the main stages of fi eld crop development.This coefficient is a leading agrometeorological factor in measuring effects of climate change on agricultural suitability, i.e. soil fertility and crop yield (reduction) (Dmitrenko, 2010;Dmitrenko et al, 2017).The value of the cumulative productivity coeffi cient allows optimization of the spatial location of fi eld crops by the degree of climate suitability, and evaluation of the unprofi tability of some factors of meteorological origin in the form of yield shortfall.The cumulative productivity (suitability) coeffi cient of climate is calculated by the following formula (Dmitrenko VP, 2010): where η(T і ), η(R і ) -productivity coeffi cients, which describe the effect of air temperature and precipitation on the yield during the і-th stage of the vegetation cycle; α і − a weighing factor for contribution of the duration of each і-th stage of the vegetation cycle to the productivity level under optimal conditions of temperature and precipitation The temperature productivity coeffi cient η(Т) characterizes the degree of correspondence between ther-mal conditions and the needs of plants and is calculated according to the formula (Dmytrenko VP, 2010): where у(Т) -productivity under current thermal conditions Т; Y(T opt ) -productivity under optimal temperature Т opt during each period of the vegetation cycle; T min , T max -biological extremes of temperature in the corresponding period of the vegetation cycle; q 1 , q 2 -model parameters which are determined by the formulas: The coeffi cient of crop productivity by the precipitation amount characterized the degree of correspondence of the moisturization conditions to the needs of plants in all the stages of the vegetation cycle, except for the ripening stage, and is described by the equation (Dmytrenko, 2010): where у(R) -productivity under the current amount of precipitation R; Y(R opt ) -maximum productivity under the optimum amount of precipitation R opt during a certain stage of the vegetation cycle; R min , R max -biological extremes of the precipitation amount in the corresponding stage of the vegetation cycle; v 1 , v 2 -model parameters, determined by the formulas: The determination of the correspondence of the thermal regime and the precipitation amount to the needs of the fi eld crop for all the stages of the vegetation cycle was conducted using the cumulative productivity coeffi cient η(T, R) (Dmitrenko, 2010): The obtained values of the cumulative productivity coeffi cient were transformed into percentages and the suitability scale (Dmitrenko, 2010) was used to estimate the correspondence of the regime of heat and moisture to the needs of the fi eld crop: 86-100 %favorable, 66-85 % -satisfactory, 36-65 % -unsat-BALABUKH et al.
The value of the climate suitability index can be used to estimate the climatic yield shortfall δу с by the formula (Dmitrenko, 2010): The study on the cumulative infl uence of changes in precipitation amount and air temperature on the crop productivity was conducted using daily data about the precipitation amount and the average daily air temperature from the network of hydrometeorological monitoring of Ukraine ( 187 The optimum values of precipitation amount in specifi c vegetative stages of corn and spring barley in Ukraine are presented in Table 1. The average values of air temperature, precipitation amount, the coeffi cients of temperature and precipitation productivity, and the cumulative productivity coeffi cient for 1981-2010 were determined for each phase of the vegetative cycle of corn and spring barley and the mentioned scale was used to estimate the correspondence of the heat and moisture regime to the needs of fi eld crops in all the soil-climatic zones of Ukraine.The evaluation of the intensity, relevance, and signifi cance of the changes in the average annual values of the agroclimatic indices was conducted for the period under investigation.The coeffi cient of the linear trend (a), characterizing the rate and direction of their change, was used as a measure of intensity in the change of indices.The signifi cance of the coef-fi cients of the linear trend (р) was evaluated by Student's t-criterion.According to the recommendation of the Intergovernmental Panel on Climate Change (IPCC, 2014;IPCC, 2021), the following relevant criteria were used: р ≤ 0.01, probability -99-100 %, the change is practically undoubted; 0.01 < р ≤ 0,1, probability -90-99 %, the change is very probable; 0.1 < р ≤ 0.34, probability -66-90 %, the change is probable; 0.34 < р ≤ 0.67, probability -33-66 %, the change is both probable and improbable; 0.67 < р ≤ 0.90, probability -10-33 %, the change is hardly probable; 0.90 < р ≤0 .99,probability -1-10 %, the change is ever hardly probable; р > 0.99, probability -0-1 %, the change is of extremely low probability.The evaluation of intensity, and signifi cance of the change in the average annual values of the agroclimatic indices was conducted for each administrative region of Ukraine and for its soil climatic zones using these indices (a and p): Forest (Polissia), Forest-Steppe (western, central, eastern Forest-Steppe), and Steppe (northern and southern Steppe).The comparative analysis of agroclimatic indices changes demonstrated their specifi cities in the soil climatic zones of Ukraine and in different stages of plant development, and the abstract logical methods helped form generalizations and conclusions.

RESULTS
The infl uence of the change in the precipitation amount on corn productivity by the stages of crop development during 1981-2010.The analysis of precipitation levels during the vegetation cycle of corn cultivation during 1981-2010 revealed notable variation in moisture conditions across different agroclimatic zones in Ukraine.The presowing period exhibited sig-  2).
During the third leaf to panicle emergence stage of corn, unfavorable moisturization conditions were observed in the eastern Forest-Steppe and the Steppe of Ukraine.In the fi nal milky ripeness to middle dough stage, excessive moisturization and unsatisfactory cultivation conditions in all the agroclimatic zones were present (Table 2).Quantitative evaluation indicated mainly satisfactory conditions for corn cultivation during the presowing period in all agroclimatic zones, with favorable conditions during the sowing-third leaf stage (Table 2).However, during the third leaf-panicle emergence stage, only Polissia and the western Forest-Steppe exhibited favorable conditions, while the central Forest-Steppe experienced satisfactory conditions and the eastern Forest-Steppe and the Steppe of Ukraine faced unfavorable ones.During the milky ripeness -middle dough stage, all soil-climatic zones exhibited unfavorable conditions, with productivity levels ranging only 28 to 65 % of the maximal potential (Table 2).
The climate suitability index S(T,R) provided insights into the overall suitability of corn cultivation in the agroclimatic zones of Ukraine from 1981 to 2010.Corn cultivation was determined to be favorable in Polissia and the western Forest-Steppe (85-86 %), satisfactory in the central and eastern Forest-Steppe and northern Steppe (72-82 %) and unfavorable in the southern Steppe (56 %) based on the maximum productivity level.
The agroclimatic conditions for corn cultivation signifi cantly changed towards the end of the 20 th and the beginning of the 21 st century.Notably, there was an overall increase in air temperature throughout the entire vegetation cycle of corn across all soil-climatic zones in Ukraine.This rise in temperature infl uenced temperature productivity and negatively impacted crop productivity formation (Balabukh et al, 2021).The combined effect of temperature and precipitation changes had varying impact on corn productivity during different stages of development and exhibited specifi c characteristics in each soil-climatic zones of Ukraine Polissia.The analysis of precipitation changes in Polissia from 1981 to 2010 revealed an overall increase in precipitation levels throughout the entire vegetation cycle of corn, particularly in the presowing period.However, exceptions were observed in Zhytomyr and Chernihiv districts during the third leaf to panicle emergence stage, where there was an increase in precipitation defi cit by 18-19 %, and a 5 % decrease during the blossoming stage over 10 years in the Chernihiv region (Table 3).The impact of precipitation on productivity remained relatively stable throughout the vegetation cycle, with only a probable increase observed during the presowing period in Volyn and Rivne regions (Table 4).
The cumulative coeffi cient of temperature and precipitation productivity in Polissia exhibited signifi cant changes only during the presowing period, with a probable increase observed (Table 5).However, the change in the climate suitability and corn yield shortfall was considered to be hardly probable, i.e. statistically virtually insignifi cant (Table 6).
Forest-Steppe.Moisturization patterns also underwent changes during the vegetation cycle of corn, albeit unevenly.In the western Forest-Steppe, there was an increase in precipitation levels throughout most of the vegetation stages (Table 3).The most significant changes were observed in the Lviv region, with a probable and very probable increase in precipitation by 10-20 % over 10 years during each stage of crop development.However, these changes had unfavorable implications for corn cultivation, particularly during the milky ripeness to middle dough stage, resulting in 4-5 % decrease in crop productivity over 10 years (Table 4).
In the central Forest-Steppe, the precipitation amount increased only during the presowing period, and blossoming, and milky ripeness to middle dough stages.These changes ranged from 5-10 % over 10 years.However, during corn sowing, germination, and the third leaf to panicle emergence stage, precipitation decreased by an average of 4-10 % over 10 years in the region (Table 3).In the Kyiv and Cherkasy regions, these changes were even more pronounced, reaching 13 % over 10 years.The increased moisture defi cit and excess were detrimental to corn cultivation throughout the vegetation cycle, except during the presowing period, leading to a decreased crop productivity, as evidenced by changes in the precipitation productivity coeffi cient (Table 4).
The eastern Forest-Steppe experienced a signifi cant decrease in precipitation levels throughout almost the entire corn vegetation cycle, except during the milky ripeness to middle dough and the presowing stage.The highest increase in moisture defi cit was observed in the Sumy region.These changes resulted in decreased precipitation productivity during almost the entire corn vegetation cycle, particularly during the blossoming and the milky ripeness to middle dough stage (Table 4).
The analysis of the cumulative coeffi cient of temperature and precipitation productivity revealed predominantly unfavorable changes in temperature and precipitation for corn cultivation in the Forest-Steppe, particularly during the vegetation cycle, except for the presowing period (Table 6).These unfavorable conditions were most pronounced in the central and eastern Forest-Steppe during the third leaf to panicle emer-    gence and blossoming and milky ripeness to middle dough stages (Table 5).Changes in air temperature and precipitation had a probable and very probable negative impact on climate suitability and yield shortfall, resulting in a 3-5 % decrease in yield over 10 years, especially in the central and eastern Forest-Steppe (Table 7).
In the Steppe zone, the changes in the precipitation level fl uctuated between -5 and 5 % over each 10-year period throughout almost the entire corn vegetation cycle (Table 3).These changes in precipitation were found to be insignifi cant for the Steppe zone.However, exceptions were observed during the pre-sowing period and the milky ripeness to middle dough stage, where there was an average increase of 10-15 % in the precipitation 10 years in the region.Despite these changes, the overall effect of this fl uctuation in moisture was unfavorable for corn cultivation throughout the entire vegetation period, as indicated by a decrease in the precipitation produc- tivity coeffi cient (Table 4).Only the increase in the precipitation during the presowing period contributed to an increase in crop productivity.Nevertheless, the moisturization conditions remained favorable for corn cultivation in the Steppe during 1981-2010 (Table 4).
The analysis of the cumulative productivity coeffi cient of temperature and precipitation revealed that the changes in temperature and precipitation were unfavorable for corn cultivation, in the southern Steppe (Table 5).These changes resulted in a 3-5 % decrease in productivity over 10 years, particularly during the stage from the third leaf to panicle emergence.
The change in the thermal and moisturization regimes led to the decrease in climate suitability for corn cultivation by 7-10 % in 10 years in the southern Steppe and by 5-7 % in 10 years in the northern Steppe (Table 6).Overall, in the southern Steppe, the conditions for corn cultivation were deemed satisfactory, with a yield shortfall averaging 20-25 % and above in the region due to climate factors.However, the current climatic period has presented unsatisfactory conditions for corn cultivation in the southern Steppe, resulting in a yield shortfall of 35-40 %.
The infl uence of the change in the precipitation amount on spring barley productivity by the stages of crop development during 1981-2010.The analysis of the moisturization conditions for spring barley during 1981-2010 revealed signifi cant variability throughout the vegetation cycle, although generally favorable conditions prevailed across a substantial area of Ukraine, with the exception of the southern Steppe region where conditions were deemed satisfactory.Notably, there was a decrease in precipitation levels during the stagesowing to third leaf and tillering stages across all the agroclimatic zones, compared to the optimum values.The most pronounced precipitation defi cit was observed in the eastern Forest-Steppe and Steppe zones, particularly in the southern Steppe, where the sowing to third leaf stage experienced nearly a 35 % reduction in precipitation compared to the optimum amount.Similarly, the tillering stage encountered an approximate 80 % decrease in precipitation (Table 7).Unfavorable moisturization conditions persisted across all the agroclimatic zones during the stagemilky ripeness to middle dough stage.However, excessive moisture was observed during this phase of crop development, particularly in Polissia, the western Forest-Steppe, and central Forest-Steppe.These conditions had a detrimental impact on spring barley productivity, while remaining conducive to their cultivation during this stage.During 1981-2010, the climate suitability index S(T, R) demonstrated favorable conditions for the cultivation of spring barley in all the agroclimatic zones of Ukraine, ranging from 86 to 92 % of the maximum productivity level, except for the southern Steppe region, where conditions were satisfactory at 80 %.Consequently, due to climate factors, the spring barley yield fell short (δy с ) by 8 to 14 and 20 % of the maximum possible level.
In the Polissia region, an overall rise in precipitation level throughout most of the growth cycle took place in the period 1981-2010.Nevertheless, exceptions were observed during the stem elongation to ear formation stage across the entire Polissia territory and during the milky ripeness to middle dough stage in Zhytomyr and Chernihiv Polissia.These regions experienced a 3-6 % increase in precipitation defi cit over a span of 10 years, with a particularly notable 15 % increase in June (Table 8).
The alteration in moisture pattern proved to be advantageous for barley solely during the tillering stage, where an upsurge in precipitation resulted in improved crop productivity up to 4%.However, during other stages of development, both increases and decreases in precipitation levels proved detrimental to barley cultivation, especially during the crop ripening stage (Table 9).
It is very probably and probably that the changes in the thermal regime and the moisture regime were responsible for a decline in the cumulative productivity coeffi cient of temperature and precipitation across the entire Polissia region.This decline was evident during the sowing of barley, and the emergence of the third leaf, milky ripeness, and middle dough stages.In Chernihiv and Zhytomyr Polissia, a decrease was also observed during the stem elongation and ear formation stages (Table 10).However, an increase in air temperature during the presowing period, combined with a decrease in precipitation, proved benefi cial for barley.Similarly, during the tillering stage, an increase in precipitation, accompanied by insignifi cant temperature changes, had a positive impact.
Overall, the alterations in both the thermal regime and the moisture regime during the climate period of 1981-2010 likely contributed to 1 % decrease in climate suitability for barley cultivation over 10 years in the Volyn region.Consequently, this decrease resulted in a decline in yield shortfalls.In the remaining area of Polissia, changes in climate suitability were predominantly negative, although their likelihood remains uncertain (Table 11).
Forest-Steppe.In contrast to the temperature fl uctuations the variations in precipitation levels in the Forest-Steppe region during the vegetation cycle of spring barley cultivation were highly uneven.In the predominant part of the Forest-Steppe, these changes ranged from -5 to 5 % over a span of 10 years (Table 8).However, these precipitation changes had minimum impact on the Forest-Steppe.In the western Forest-Steppe, there was a probable increase of 10-20 % in precipitation over 10 years during the sowing, third leaf, milky      ripeness, and middle dough stages, and an increase up to 8-9 % during the presowing period.However, in the central and eastern Forest-Steppe, there was a probable decrease of 10-13 % precipitation over 10 years during the stem elongation and ear formation stages.These changes had detrimental effects on barley cultivation, as evidenced by the decrease in the precipitation productivity coeffi cient and a probable 3-6 % decrease in crop productivity during the corresponding phase of development (Table 9).An analysis of the cumulative coeffi cient of temperature and precipitation productivity, revealed that the temperature and precipitation changes during the current climatic period were mostly unfavorable for spring barley cultivation in the Forest-Steppe throughout the vegetation cycle (Table 10).The most signifi - cant changes were observed during the stage milky ripeness and middle dough stages, as well as during the stem elongation and ear formation stage.The increase in the air temperature and precipitation levels in the western Forest-Steppe during the milky ripeness and middle dough stages, along with a notable temperature increase and insignifi cant precipitation change in the central and eastern Forest-Steppe, were likely unfavorable for barley cultivation.Furthermore, the increase in temperature and decrease in precipitation levels in the central and eastern Forest-Steppe were also unfavorable.During other stages of barley development, the changes in the cumulative productivity coeffi cient were generally insignifi cant across the entire Forest-Steppe region, albeit with varying tendencies (Table 10).
Alterations in air temperature and precipitation levels contributed to a decrease in climate suitability for barley cultivation and resulted in higher yield shortfalls in the Forest-Steppe, particularly in the western and central regions, where they was a probable change of 2-3 % over 10 years (Table 11).
Steppe.The analysis conducted on the climate period of 1981-2010 revealed notable variation in precipitation levels within the northern and southern Steppe region.In the northern Steppe, an overall increase in precipitation was observed throughout almost the entire vegetation cycle of barley cultivation, with the exception of the stem elongation to ear formation stage (Table 8).However, these changes were found to fl uctuate within 5 % over a span of 10 years and were considered insignifi cant and highly improbable.However, the southern Steppe experienced a remarkable decrease in precipitation levels throughout most of barley cultivation period, with the only exceptions being the presowing period and tillering stage.Nevertheless, similar to the northern Steppe, these changes were also deemed insignifi cant and highly improbable, and fl uctuating within 5 % over 10 years (Table 8).
The increase in precipitation during the tillering stage and its decrease during the milky ripeness and middle dough stages likely had a potentially favorable impact on spring barley, as evidenced by a higher precipitation productivity coeffi cient (Table 9).
Furthermore, an analysis of the cumulative productivity coeffi cient, considering the combined effects of temperature and precipitation, indicated that the temperature and precipitation changes observed between 1981 and 2010 were generally unfavorable for spring barley cultivation, particularly in the southern Steppe (Table 10).These changes resulted in a probable 1-2 % decrease in productivity over 10 years, especially during the milky ripeness and middle dough, stem elongation to ear formation, and tillering stages.The alterations in both the thermal regime and moisture regime contributed to a decrease in climate suitability for spring barley cultivation, very probably by 3-4 % over 10 years in the southern Steppe and probably by 2-3 % in the northern Steppe.Consequently, there was a corresponding increase in yield shortfalls for this crop of 2%…to 4 % (Table 11).

DISCUSSION
Climate change poses one of the greatest threats to global food security in the 21 st century (Wheeler and von Braun, 2013).In numerous cereal producing regions since the 1980s, changes in air temperature and precipitation pattern have led to a decrease in crop productivity compared to historical norms unaffected by climate change (Lobell et al, 2011;Zhao et al, 2017).For example, between 1981 and 2010, climate changes resulted in a 19-33 % reduction in the productivity of corn, soybeans, rice, and wheat (Iizumi, 2016).The most substantial decline in corn and soybean productivity were observed in Argentina and northern-eastern China, while reductions in rice productivity were more prominent in Indonesia and southern China.Wheat productivity experienced signifi cant decreases in Australia, France, and Ukraine (Iizumi, 2016).In the pampas of southern America, the potential productivity increase during the same period could have been 15-20 % higher if the climate had remained stable (Verón, 2015).
Studies have shown that the average yield shortfall caused by climate changes between 1981 and 2008 was 3.8 % for corn and 5.5 % for wheat (Lobell et al, 2011).The cumulative annual shortfall of these two crops, along with barley, amounted to 40 million tons per year, which accounted for approximately 2-3 % of global production (Lobell and Field, 2007).In Kazakhstan, climate change led to a decrease in wheat and barley productivity by 1.9 % and 4.8 %, respectively, compared to a scenario without climate change (Schierhor, 2020).In western and central Europe, the increase in the precipitation defi cits and heightened risk of severe droughts have contributed to a decline in the potential with rainfed agriculture (Trnka et al, 2010).In high latitudes, such as Finland, there have been positive effects on barley productivity resulting from increases in temperature and CO 2 levels under optimistic climate scenarios (Rötter et al, 2012).Forecasts concerning the potential impact of climate change on cereal produc-tivity suggest that most regions where spring barley is cultivated will experience warmer and drier conditions, leading to a global decrease in productivity and production ranging from 3 to 17 %, depending on the specifi c environment (Xie et al, 2018, Cheng et al, 2019).Similar decreases in barley productivity due to climate change are anticipated in other regions as well.For instance, in the Mediterranean region, projected declines range from 25 to 8 %, while Kazakhstan is expected to see a reduction of 4.8 %.The Czech Republic may experience declines ranging from −19 to +5 %, and Iran could face a potential decrease of up to 50 % (Cammarano et al, 2019, Mirgol et al, 2020, Schierhorn et al, 2020).
It has been determined that changes in air temperature, especially when exceeding the optimal range for productivity, have a greater infl uence on crop yield variability compared to temperatures below the optimal range and soil moisture defi cits (Iizumi, 2016).On average, crop productivity is more responsive to trends in air temperature change and diurnal patterns than changes in precipitation (Verón et al, 2015).
The fi ndings obtained in Ukraine regarding changes in corn and spring barley productivity between 1981 and 2010, attributed to climate change, are consistent with data, obtained from other regions such as western and central Europe, northern-eastern China, Argentina, Mediterranean region, Kazakhstan and other (Trnka et al, 2010;Iizumi, 2016;Schierhor, 2020).Determined that, similar to other countries, the impact of climate change on crop productivity in Ukraine varies depending on the specifi c crop and the region where it is cultivated.In Ukraine, there has been an increase in air temperature and a decrease in precipitation along with their altered distribution during the vegetation cycle of cereal cultivation (Balabukh, 2019;Balabukh et al, 2021).These changes and their impact on crop productivity intensify from the northern regions of the country (Polissia) to the southern ones (southern Steppe), where the most signifi cant increases in air temperature and precipitation are observed.Consequently, the average yield shortfall amounts to 35-40 % for corn of and 10-15 % for spring barley.
An analysis of the relationship between air temperature, precipitation and their suitability for corn and spring barley cultivation in Ukraine confi rms previous fi ndings that changes in cereal productivity depend more on air temperature and evaporation than on variations in precipitation, particularly in the northern regions (Liu et al, 2020;Verón et al, 2015).
The changes observed in the agroclimatic conditions of corn and spring barley cultivation indicate a decline in the potential of dryland farming in Ukraine, including the Forest-Steppe soil-climatic zone.These observations align with similar trends identifi ed in other regions such as southern America, western and central Europe, northern-eastern China, Argentina, Mediterranean region, Kazakhstan (Schierhor, 2020;Verón et al, 2015;Iizumi, 2016;Cammarano et al, 2019, Mirgol et al, 2020;Schierhorn et al, 2020;Trnka et al, 2010;Rötter et al, 2012).
It is important to note that the study on the impact of changes in precipitation and the cumulative effects of precipitation and air temperature on corn and spring barley productivity and the climate suitability in Ukraine only covers the period from 1981 to 2010.It does not account for the most recent decade, which has been recognized as the warmest globally and in Ukraine specifi cally (State of the Global Climate 2020, 2021; Balabukh et al, 2021;National Report EN 2020, 2021).The observed decrease in cereal productivity and increase in yield shortfalls due to rising air temperatures and precipitation defi cits were further confi rmed in 2020, which experienced record-breaking temperature since the late 19 th century.Prolonged drought conditions persisted for eight months in 2019 and continued throughout 2020 (except for February, May, and June) (Balabukh et al, 2021;National Report EN 2020, 2021), resulting in crop losses across an area of 770,878 ha, with the total damage exceeding 23.4 billion hryvnia (National Report EN 2020, 2021).The Steppe region, which had both favorable and unfavorable thermal and moisture conditions for cereal cultivation between 1981 and 2010, exhibited the highest susceptibility to changes in the agroclimatic conditions, leading to reduced productivity, decreased climate suitability, and increased yield shortfalls infl uenced by climate factors.For instance, in Mykolayiv region, cereal crops were lost across an area of 24,602 ha, including 2,000 ha of corn, while a decrease in corn yield was observed across 43,200 ha.In Kirovohrad region, cereal losses amounted to 23,378 ha (21,300 ha of corn), with low corn yield observed across 146,700 ha (Balabukh et al, 2021;National Report EN 2020, 2021).
In conclusion, both decrease and increase in crop productivity variability resulting from climate change depend on the specifi c crop and the region where it is cultivated.These fi ndings underscore the importance of long-term global monitoring of productivity, along with comprehensive data collection, to enhance our understanding of the current variability in productivity and its crucial infl uencing factors (Iizumi T, 2016).

CONCLUSIONS
The changes in the moisturization conditions during the vegetative cycle of corn and spring barley at the during 1981-2010 have been uneven across soil-climatic zones in Ukraine.In Polissia, these changes were mostly insignifi cant and unlikely, while in the Forest-Steppe and Steppe regions experienced an increase in precipitation defi cits, with levels 35-80 % lower than optimal in certain stages of the crop`s growth cycle.When considering changes in precipitation amount, moisture conditions for spring barley remained favorable in most regions of Ukraine, except for the southern Steppe, where conditions were satisfactory.For corn moisture conditions were favorable in Polissia, improved in the western Forest-Steppe and some central and other regions, satisfactory in the eastern Forest-Steppe and northern Steppe, and unsatisfactory in the southern Steppe, where conditions deteriorated significantly.The impact of changes in precipitation amounts on corn and spring barley productivity was found to be smaller than the impact of changes in air temperature.
Since the 1980s, cumulative changes in temperature and precipitation in Ukraine have led to decreased fi eld crop productivity in signifi cant parts of the country compared to calculations assuming absence of climate change.The observed changes in air temperature and precipitation, and their infl uence on climate suitability and cereal productivity, indicate a decline in the potential for dryland agriculture in both the Steppe and Forest-Steppe regions.The impact of climate change on corn productivity has been more pronounced than on spring barley, increasing from north to south correlation with the rise in precipitation defi cits and air temperature.
The changes in air temperature and precipitation levels have likely contributed to a decrease in climate suitability and an increase in yield shortfalls in corn cultivation, with an average increase of 3-5 % over each 10 years in the central and eastern Forest-Steppe, 5-7 % over each 10 years in the northern Steppe, and 7-10 % over each 10 yearsin the southern Steppe.Overall, corn yield shortfalls due to climate factors in the Forest-Steppe averaged 10-20 %, over 30 years.In the northern Steppe, yield shortfalls reached 20-25 % and higher, while in the southern Steppe, where unfavorable agroclimatic conditions for corn cultivation were observed, yield shortfalls were 35-40 % over 30 years.
In a considerable part of Polissia, except for the Volyn region, the increase in air temperature and changes in precipitation during the barley vegetation period did not signifi cantly affect climate suitability or yield shortfalls.In the Forest-Steppe, however, these changes were mostly unfavorable for barley cultivation, particularly in the western and central regions, resulting in a decrease in climate suitability and an increase in yield shortfalls of 2-3 % over 10 years and an average of 5-10 % over 30 years in the region.The Steppe region experienced the most signifi cant changes in air temperature and precipitation, leading to grain yield shortfalls of 5-10 % on average in the northern Steppe and 10-15 % in the southern region.
points) for 1981-2010 [CGO.Sectoral State Archive of hydrometeorological observations of the State Emergency Service of Ukraine].
YIELD SHORTFALL OF CEREALS IN UKRAINE CAUSED BY THE CHANGE IN AIR TEMPERATURE

Table 1 .
The optimum values of the precipitation amount (mm) and air temperature (ºС) in specifi c stages of corn and spring barley vegetation in Ukraine (according toDmitrenko, 2010)Steppe, and southern Steppe, insuffi cient moisture for corn sowing.The moisturization conditions during this stage were more or less satisfactory in the eastern Forest-Steppe and southern Steppe (Table

Table 2 .
Agroclimatic conditions of corn cultivation during 1981-2010 opt -optimum air temperature for stages of development, ºС; T -average air temperature for stages of development in 1981-2010; η(T, R) -cumulative productivity coeffi cient.

Table 5 .
The change rate in the cumulative coeffi cient of T and R productivity during the stages of the vegetation cycle of corn cultivation and its signifi cance (р) Note. a -the coeffi cient of the linear trend , %/10 years ; p -the signifi cance of the coeffi cients of the linear trend.

Table 6 .
The change rate in the climate suitability and corn yield shortfall at the during 1981-2010 in the soil-climatic zones of Ukraine and its signifi cance (р) Note. a -the coeffi cient of the linear trend , %/10 years ; p -the signifi cance of the coeffi cients of the linear trend.YIELD SHORTFALL OF CEREALS IN UKRAINE CAUSED BY THE CHANGE IN AIR TEMPERATURE

Table 7 .
Agroclimatic conditions of spring barley cultivation during 1981-2010 opt -optimum precipitation amoun for stages of development, mm; R -precipitation amount for stages of development in 1981-2010; Т opt , -optimum air temperature for stages of development, ºС; T -average air temperature for stages of development in 1981-2010; η(T, R)-cumulative productivity coeffi cient.

Table 11 .
The change rate in the climate suitability and spring barley yield shortfall during 1981-2010 in the regions of Ukraine and its signifi cance (р) Note. a -the coeffi cient of the linear trend, %/10 years; p -the signifi cance of the coeffi cients of the linear trend.YIELD SHORTFALL OF CEREALS IN UKRAINE CAUSED BY THE CHANGE IN AIR TEMPERATURE