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1.
Accurate use of precipitation can be considered as one of the best options to decrease the amount of underground water extraction for agriculture in arid and semi-arid areas such as northeast of Iran. For this reason, characteristics of the growing season such as onset, cessation, and length of the growing period should be analyzed. In this paper, we have calculated growing season characteristics of five locations in northeast of Iran using 45?years historical daily weather data and employed four approaches with different calculation methods. As temperature is one of the limiting factors in irrigation-based agriculture, the first approach has been based on this factor. The three remaining approaches were based on joint rainfall and temperature approach, rainfall, evapotranspiration, and temperature approach, and the final approach was based on availability of adequate water in 0.25?m of soil profile. The calculated onset dates using second and third approaches have been based on soil water balance model and relative evapotranspiration rate, and both were evaluated also to find whether the onset is a false start occurrence or not. The results showed that, when temperature was the only limiting factor, Bojnourd station with 197?days showed the longest growing season, however, when precipitation was used along with temperature, longest growing season (124?days) was obtained for Sabzevar station. The third approach which benefits from a water balance model and is similar to rainfed conditions showed the longest growing season with 147?days for Mashhad station. When adequate soil water approach was used, Bojnourd station with 255?days showed the longest growing season. Evaluation of false start of the growing season indicated the lowest probability of false start occurrence for Mashhad compared with other locations.  相似文献   

2.
The water deficits in different development stages and the whole growing season of winterwheat in North China under climate change scenarios are analyzed based on the meteorological da-ta,crop phenomenon and soil hydrological data of 30 weather stations.The results show that ifthe temperature rises,the potential evapotranspiration and crop maximum transpiration will in-crease 8%-10%;the actual evapotranspiration in whole growing season will increase about 1%-2%;and it seems to decrease in spring.Therefore the water deficit status would deteriorate.Theamount of water deficit in whole growing season would increase 14%-30%,and the water deficitisolines might shift southward with maximum shift distance being 190 km.As a result the climaticsuitability of winter wheat would change,and the variation rate of yield reduction will be 8%-20% of the present value which results in the declining output values.The irrigation amountwould increase 25%-33%,and the agriculture cost might increase owing to additional irrigation.  相似文献   

3.
This paper characterizes droughts in Romania using the approach of both the standardized precipitation index (SPI) and climatic water deficit (WD). The values of the main climatic factors (rainfall, temperature, reference evapotranspiration, etc.) were obtained from 192 weather stations in various regions of Romania. Penman–Monteith reference evapotranspiration (ETo-PM) was used to calculate WD as the difference between precipitation (P) and ETo-PM. SPI was calculated from precipitation values. There is a clear difference between drought and aridity. Drought occurrence determines higher WD values for plains and plateaus and lower climatic excess water (EW) values for high mountains in Romania, depending on the aridity of the specific region considered and drought severity. WD calculated as mean values for both normal conditions and, for all locations studied, various types of drought was correlated with mean annual precipitation and temperature, respectively. The combined approach of WD and SPI was mainly carried out for periods of 1 year, but such studies could also be done for shorter periods like months, quarters, or growing season. The most arid regions did not necessarily coincide with areas of the most severe drought, as there were no correlations between WD and SPI and no altitude-based SPI zones around the Carpathian Mountains, as is the case for other climate characteristics, soils and vegetation. Water resource problems arise where both SPI values characterize extremely droughty periods and WD values are greatly below ?200 mm/year. This combined use of SPI and WD characterizes the dryness of a region better than one factor alone and should be used for better management of water in agriculture in Romania and also other countries with similar climate characteristics.  相似文献   

4.
Crop production would decline in the Midwestern United States from climate change following a regional nuclear conflict between India and Pakistan. Using Agro-IBIS, a dynamic agroecosystem model, we simulated the response of maize and soybeans to cooler, drier, and darker conditions from war-related smoke. We combined observed climate conditions for the states of Iowa, Illinois, Indiana, and Missouri with output from a general circulation climate model simulation that injected 5 Tg of elemental carbon into the upper troposphere. Both maize and soybeans showed notable yield reductions for a decade after the event. Maize yields declined 10–40 % while soybean yields dropped 2–20 %. Temporal variation in magnitude of yield for both crops generally followed the variation in climatic anomalies, with the greatest decline in the 5 years following the 5 Tg event and then less, but still substantial yield decline, for the rest of the decade. Yield reduction for both crops was linked to changes in growing period duration and, less markedly, to reduced precipitation and altered maximum daily temperature during the growing season. The seasonal average of daily maximum temperature anomalies, combined with precipitation and radiation changes, had a quadratic relationship to yield differences; small (0 °C) and large (?3 °C) maximum temperature anomalies combined with other changes led to increased yield loss, but medium changes (?1 °C) had small to neutral effects on yield. The exact timing of the temperature changes during the various crop growth phases also had an important effect.  相似文献   

5.
A simulation study was carried out to assess the potential sensitivity of wheat growth and water balance components to likely climate change scenarios at Wagga Wagga, NSW, Australia. Specific processes considered include crop development, growth rate, grain yield, water use efficiency, evapotranspiration, runoff and deep drainage. Individual impacts of changes in temperature, rainfall and CO2 concentration ([CO2]) and the combined impacts of these three variables were analysed for 2050 ([CO2] = 570 ppm, T +2.3°C, P ?7%) and 2070 ([CO2] = 720 ppm, T +3.8°C, P ?10%) conditions. Two different rainfall change scenarios (changes in rainfall intensity or rainfall frequency) were used to modify historical rainfall data. The Agricultural Production Systems Simulator (APSIM) was used to simulate the growth and water balance processes for a 117 year period of baseline, 2050 and 2070 climatic conditions. The results showed that wheat yield reduction caused by 1°C increase in temperature and 10% decrease in rainfall could be compensated by a 266 ppm increase in [CO2] assuming no interactions between the individual effects. Temperature increase had little impact on long-term average water balance, while [CO2] increase reduced evapotranspiration and increased deep drainage. Length of the growing season of wheat decreased 22 days in 2050 and 35 days in 2070 conditions as a consequence of 2.3°C and 3.8°C increase in temperature respectively. Yield in 2050 was approximately 1% higher than the simulated baseline yield of 4,462 kg ha???1, but it was 6% lower in 2070. An early maturing cultivar (Hartog) was more sensitive in terms of yield response to temperature increase, while a mid-maturing cultivar (Janz) was more sensitive to rainfall reduction. Janz could benefit more from increase in CO2 concentration. Rainfall reduction across all rainfall events would have a greater negative impact on wheat yield and WUE than if only smaller rainfall events reduced in magnitude, even given the same total decrease in annual rainfall. The greater the reduction in rainfall, the larger was the difference. The increase in temperature increased the difference of impact between the two rainfall change scenarios while increase in [CO2] reduced the difference.  相似文献   

6.
基于涡度相关的春玉米逐日作物系数及蒸散模拟   总被引：3，自引：0，他引：3       下载免费PDF全文
作物系数是计算作物蒸散量的关键参数。利用2006—2008年和2011年辽宁锦州玉米农田生态系统的涡度相关、气象、作物发育期及叶面积指数观测数据,分析不受水分胁迫条件下玉米逐日作物系数特征及其与叶面积指数的关系。研究表明:作物系数与玉米农田实际蒸散均呈单峰型变化,约在7月末至8月初达到最大值 (玉米开花吐丝期)。在此基础上,建立了不受水分胁迫条件下玉米逐日作物系数与叶面积指数关系 (达到0.01显著性水平), 同时,采用积温表示的标准化生育期方法模拟相对叶面积指数,并建立了逐日作物系数与相对叶面积指数关系 (达到0.01显著性水平),解决了无叶面积观测地区玉米逐日实际蒸散量的计算。研究结果可为玉米农田用水管理以及灌溉措施的制定提供参考。  相似文献   

7.
Phenology is critical to ecosystem carbon quantification, and yet has not been well modeled considering both aboveground and belowground environmental variables. This is especially true for alpine and pan-arctic regions where soil physical conditions play a significant role in determining the timing of phenology. Here we examine how the spatiotemporal pattern of satellite-derived phenology is related to soil physical conditions simulated with a soil physical model on the Tibetan Plateau for the period 1989–2008. Our results show that spatial patterns and temporal trends of phenology are parallel with the corresponding soil physical conditions for different study periods. On average, 1 °C increase in soil temperature advances the start of growing season (SOS) by 4.6 to 9.9 days among different vegetation types, and postpones the end of growing season (EOS) by 7.3 to 10.5 days. Soil wetting meditates such trends, especially in areas where warming effect is significant. Soil thermal thresholds for SOS and EOS, defined as the daily mean soil temperatures corresponding to the phenological metrics, are spatially clustered, and are closely correlated with mean seasonal temperatures in Spring and Autumn, respectively. This study highlights the importance and feasibility of incorporating spatially explicit soil temperature and moisture information, instead of air temperature and precipitation, into phenology models so as to improve carbon modeling. The method proposed and empirical relations established between phenology and soil physical conditions for Alpine ecosystems on the Tibetan plateau could also be applicable for other cold regions.  相似文献   

8.
Three new 159-year long reconstructions of spring, summer, and growing season precipitation totals were developed for northeastern Kansas and northwestern Missouri from five station clusters (Lawrence, Leavenworth, and Manhattan, Kansas; Miami and Oregon, Missouri). Nonstandard observation practices are inherent in the early meteorological data, which can induce an undercount in precipitation measurements, particularly during the cool season. Threshold analyses of these five station clusters indicated undercount can be lessened for daily precipitation totals of 0.50 in. and greater during the warm season (“half-inch threshold”). Therefore, “adjusted reconstructions” of total precipitation for the spring (AMJ), summer (JA), and growing season (AMJJA) were derived using the “half-inch threshold” totals and an estimate of the missing amount between 0.00 and 0.50 in. based on an average of the modern observations at each station (or the nearest available station). The new precipitation reconstructions suggest that the most severe spring drought may have occurred during the mid-19th century, although the potential for undercount is likely highest during the spring season. The most severe summer precipitation deficit is estimated during the 1930s Dust Bowl drought, followed by the summer drought of the 1910s. When precipitation is totaled for the entire growing season, the mid-19th century and Dust Bowl droughts were of approximately equal magnitude and duration in this reconstruction. However, the integration of precipitation and temperature into seasonal measures of effective moisture, using a new 19th century temperature reconstruction for northeastern Kansas, indicates that the 1930s growing season moisture deficit was the most severe and sustained since 1855, highlighting the extraordinarily high temperatures recorded during the 1930s Dust Bowl drought.  相似文献   

9.
This paper explores changes in climatic variables, including solar radiation, rainfall, fraction of diffuse radiation (FDR) and temperature, during wheat season (October to May) and maize season (June to September) from 1961 to 2003 at four sites in the North China Plain (NCP), and then evaluates the effects of these changes on crop growth processes, productivity and water demand by using the Agricultural Production Systems Simulator. A significant decline in radiation and rainfall was detected during the 43 years, while both temperature and FDR exhibit an increasing trend in both wheat and maize seasons. The average trend of each climatic variable for each crop season from the four sites is that radiation decreased by 13.2 and 6.2 MJ m?2 a?1, precipitation decreased by 0.1 and 1.8 mm a?1, minimum temperature increased by 0.05 and 0.02°C a?1, maximum temperature increased by 0.03 and 0.01°C a?1, FDR increased by 0.21 and 0.38% a?1 during wheat and maize season, respectively. Simulated crop water demand and potential yield was significantly decreased because of the declining trend in solar radiation. On average, crop water demand was decreased by 2.3 mm a?1 for wheat and 1.8 mm a?1 for maize if changes in crop variety were not considered. Simulated potential crop yields under fully irrigated condition declined about 45.3 kg ha?1 a?1 for wheat and 51.4 kg ha?1 a?1 for maize at the northern sites, Beijing and Tianjin. They had no significant changes in the southern sites, Jinan and Zhengzhou. Irrigation, fertilization development and crop variety improvement are main factors to contribute to the increase in actual crop yield for the wheat–maize double cropping system, contrasted to the decline in the potential crop yield. Further research on how the improvement in crop varieties and management practices can counteract the impact of climatic change may provide insight into the future sustainability of wheat–maize double crop rotations in the NCP.  相似文献   

10.
Mann?CKendall non-parametric test was employed for observational trend detection of monthly, seasonal and annual precipitation of five meteorological subdivisions of Central Northeast India (CNE India) for different 30-year normal periods (NP) viz. 1889?C1918 (NP1), 1919?C1948 (NP2), 1949?C1978 (NP3) and 1979?C2008 (NP4). The trends of maximum and minimum temperatures were also investigated. The slopes of the trend lines were determined using the method of least square linear fitting. An application of Morelet wavelet analysis was done with monthly rainfall during June?CSeptember, total rainfall during monsoon season and annual rainfall to know the periodicity and to test the significance of periodicity using the power spectrum method. The inferences figure out from the analyses will be helpful to the policy managers, planners and agricultural scientists to work out irrigation and water management options under various possible climatic eventualities for the region. The long-term (1889?C2008) mean annual rainfall of CNE India is 1,195.1?mm with a standard deviation of 134.1?mm and coefficient of variation of 11%. There is a significant decreasing trend of 4.6?mm/year for Jharkhand and 3.2?mm/day for CNE India. Since rice crop is the important kharif crop (May?COctober) in this region, the decreasing trend of rainfall during the month of July may delay/affect the transplanting/vegetative phase of the crop, and assured irrigation is very much needed to tackle the drought situation. During the month of December, all the meteorological subdivisions except Jharkhand show a significant decreasing trend of rainfall during recent normal period NP4. The decrease of rainfall during December may hamper sowing of wheat, which is the important rabi crop (November?CMarch) in most parts of this region. Maximum temperature shows significant rising trend of 0.008°C/year (at 0.01 level) during monsoon season and 0.014°C/year (at 0.01 level) during post-monsoon season during the period 1914?C2003. The annual maximum temperature also shows significant increasing trend of 0.008°C/year (at 0.01 level) during the same period. Minimum temperature shows significant rising trend of 0.012°C/year (at 0.01 level) during post-monsoon season and significant falling trend of 0.002°C/year (at 0.05 level) during monsoon season. A significant 4?C8?years peak periodicity band has been noticed during September over Western UP, and 30?C34?years periodicity has been observed during July over Bihar subdivision. However, as far as CNE India is concerned, no significant periodicity has been noticed in any of the time series.  相似文献   

11.
Temperature has long been accepted as the major controlling factor in determining vegetation phenology in the middle and higher latitudes. The influence of water availability is often overlooked even in arid and semi-arid environments. We compared vegetation phenology metrics derived from both in situ temperature and satellite-based normalized difference vegetation index (NDVI) observations from 1982 to 2006 by an example of the arid region of northwestern China. From the satellite-based results, it was found the start of the growing season (SOS) advanced by 0.37 days year?1 and the end of the growing season (EOS) delayed by 0.61 days year?1 in Southern Xinjiang over 25 years. In the Tianshan Mountains, the SOS advanced by 0.35 days year?1 and the EOS delayed by 0.31 days year?1. There were almost no changes in Northern Xinjiang. Compared with satellite-based results, those estimates based on temperature contain less details of spatial variability of vegetation phenology. Interestingly, they show different and at times reversed spatial patterns from the satellite results arising from water limitation. Phenology metrics derived from temperature and NDVI conclude that water limitation of onset of the growing season is more severe than the cessation. Phenology spatial patterns of four oases in Southern Xingjiang show that, on average, there is a delay of the SOS of 1.6 days/10 km of distance from the mountain outlet stations. Our results underline the importance of water availability in determining the vegetation phenology in arid regions and can lead to important consequences in interpreting the possible change of vegetation phenology with climate.  相似文献   

12.
Over recent years, the Iberian Peninsula has witnessed an increase both in temperature and in rainfall intensity, especially in the Mediterranean climate area. Plant phenology is modulated by climate, and closely governed by water availability and air temperature. Over the period 1986–2012, the effects of climate change on phenology were analyzed in five crops at 26 sites growing in Spain (southern Europe): oats, wheat, rye, barley and maize. The phenophases studied were: sowing date, emergence, flag leaf sheath swollen, flowering, seed ripening and harvest. Trends in phenological response over time were detected using linear regression. Trends in air temperature and rainfall over the period prior to each phenophase were also charted. Correlations between phenological features, biogeographical area and weather trends were examined using a Generalized Lineal Mixed Model approach. A generalized advance in most winter-cereal phenophases was observed, mainly during the spring. Trend patterns differed between species and phenophases. The most noticeable advance in spring phenology was recorded for wheat and oats, the “Flag leaf sheath swollen” and “Flowering date” phenophases being brought forward by around 3 days/year and 1 day/year, respectively. Temperature changes during the period prior to phenophase onset were identified as the cause of these phenological trends. Climate changes are clearly prompting variations in cereal crop phenology; their consequences could be even more marked if climate change persists into the next century. Changes in phenology could in turn impact crop yield; fortunately, human intervention in crop systems is likely to minimize the negative impact.  相似文献   

13.
Seasonal drought is a common occurrence in humid climates.The year 2003 was the driest year during the period 1985-2011 in southeastern China.The objective of this study was to elucidate the impact of the exceptional drought in 2003,compared with eddy flux measurements during 2004-11,on the dynamics of evapotranspiration （ET） and related factors,as well as their underlying mechanisms,in a subtropical coniferous plantation in southeastern China.It was found that daily ET decreased from 5.34 to 1.84 mm during the intensive drought period and recovered to 4.80 mm during the subsquent recovering drought period.Path analysis indicated that ET was mainly determined by canopy conductance and deep soil water content （50 cm） during the intensive drought and recovering drought periods,respectively.The canopy conductance offset the positive effect of air vapor pressure deficit on ET when suffering drought stress,while the canopy conductance enhanced the positive effect of air temperature on ET during the late growing season.Because the fine roots of this plantation are mainly distributed in shallow soil,and the soil water in the upper 40 cm did not satisfy the demand for ET,stomatal closure and defoliation were evident as physiological responses to drought stress.  相似文献   

14.
Using the high-quality observed meteorological data, changes of the thermal conditions and precipitation over the North China Plain from 1961 to 2009 were examined. Trends of accumulated temperature and negative temperature, growing season duration, as well as seasonal and annual rainfalls at 48 stations were analyzed. The results show that the accumulated temperature increased significantly by 348.5℃ day due to global warming during 1961-2009 while the absolute accumulated negative temperature decreased apparently by 175.3℃ day. The start of growing season displayed a significant negative trend of -14.3 days during 1961- 2009, but the end of growing season delayed insignificantly by 6.7 days. As a result, the length of growing season increased by 21.0 days. The annual and autumn rainfalls decreased slightly while summer rainfall and summer rainy days decreased significantly. In contrast, spring rainfall increased slightly without significant trends. All the results indicate that the thermal conditions were improved to benefit the crop growth over the North China Plain during 1961-2009, and the decreasing annual and summer rainfalls had no direct negative impact on the crop growth. But the decreasing summer rainfall was likely to influence the water resources in North China, especially the underground water, reservoir water, as well as river runoff, which would have influenced the irrigation of agriculture.  相似文献   

15.
基于GIMMS（global inventory modeling and mapping studies）NDVI 3g数据,在提取北半球荒漠草原过渡带每年植被物候期的基础上,研究了1982-2012年物候期的时间演化趋势及空间分异特征,并结合全球气候再分析资料,探讨了物候变化的气候驱动因素。结果表明：在1998年之前,荒漠草原过渡带植被物候期变化地区间差异较大,而在1998年之后,北半球荒漠草原过渡带生长季结束期整体提前,平均提前0.41 d/a;同时,除萨赫勒以外的各地区植被生长季长度普遍缩短,平均缩短0.88 d/a。植被物候期与气候因子的相关分析发现,荒漠草原过渡带植被物候变化受气候变化影响显著,且空间差异明显。在中高纬度地区,气温是限制植被活动的关键因子,温度升高可以促进生长季开始期的提前,而降水增加则会妨碍植被生长;在较低纬度地区,水分是影响植被活动的关键因素,高温造成的水分亏缺会导致植被生长季缩短。从植被物候期对各气候因子响应的时滞性来看,荒漠草原过渡带植被的物候期对气温变化的响应最迅速,对蒸散的响应存在一定的滞后性,而对降水的响应不存在时滞差异。  相似文献   

16.
Summary Changes in the thermal climate due to inter-annual climatic variability can potentially modify existing cropping pattern by forcing farmers to rearrange transplanting and harvesting dates. In the present study, a crop climate model, the YIELD, has been applied to 12 meteorological stations located in major rice growing regions in Bangladesh to estimate the effect of thermal climate variations on the transplanting and harvesting dates of boro rice and the resultant potential changes in cropping pattern and spatial shift. The abnormal thermal climate scenarios have been created by synthetically perturbing mean air temperatures (Tair) up to −5 °C to +5 °C with an interval of 1 °C for each of these stations. Historical meteorological records of air temperature in Bangladesh have been used to prepare these scenarios. The study finds that under abnormally cool conditions transplanting dates will be pushed well into February to avoid plant injury and harvesting dates will be moved into the monsoon. The growing seasons will be longer under cooler than normal thermal conditions. Under abnormally warm conditions harvesting dates will be established well into March and will cause reduction of yield due to a shorter growing season. These conditions will also cause spatial shift in crop potential and changes in the cropping pattern. Due to a longer boro rice growing season farmers will lose a significant amount of cropping land which is usually used for low and deep water rice cultivation. New crops will need to be introduced during the beginning of a year to overcome the loss of production under abnormally cool conditions. Wheat and potato can be good options for the farmers for such conditions. New aus rice variety needs to be introduced after the boro harvesting under warmer than the normal conditions to overcome the loss of yield due to a shorter growing season. Received September 16, 1996 Revised September 8, 1997  相似文献   

17.
The Californian Mono Lake Basin (MLB) is a fragile ecosystem, for which a 1983 ruling carefully balanced water diversions with ecological needs without the consideration of global climate change. The hydroclimatologic response to the impact of projected climatic changes in the MLB has not been comprehensively assessed and is the focus of this study. Downscaled temperature and precipitation projections from 16 Global Climate Models (GCMs), using two emission scenarios (B1 and A2), were used to drive a calibrated Soil and Water Assessment Tool (SWAT) hydrologic model to assess the effects on streamflow on the two significant inflows to the MLB, Lee Vining and Rush Creeks. For the MLB, the GCM ensemble output suggests significant increases in annual temperature, averaging 2.5 and 4.1 °C for the B1 and A2 emission scenarios, respectively, with concurrent small (1–3 %) decreases in annual precipitation by the end of the century. Annual total evapotranspiration is projected to increase by 10 mm by the end of the century for both emission scenarios. SWAT modeling results suggest a significant hydrologic response in the MLB by the end of the century that includes a) decreases in annual streamflow by 15 % compared to historical conditions b) an advance of the peak snowmelt runoff to 1 month earlier (June to May), c) a decreased (10–15 %) occurrence of ‘wet’ hydrologic years, and d) and more frequent (7–22 %) drought conditions. Ecosystem health and water diversions may be affected by reduced water availability in the MLB by the end of the century.  相似文献   

18.
Abstract

A model that uses daily climate data for calculating hay crop growth in the Peace River region of British Columbia was developed and evaluated using data obtained over four growing seasons. The performances of the ratio of growth to transpiration and the ratio of growth to transpiration (J) divided by vapour pressure deficit (VPD) in estimating crop growth were compared. Transpiration was calculated by subtracting evaporation losses from the soil and foliage from the calculated evapotranspiration. Evapotranspiration was calculated using solar radiation and air temperature, and a one‐layer root zone water balance model, which accounted for soil water supply limitation. Soil water storage measurements showed that the water balance model worked well. The model provided satisfactory estimates of growing season yield of above‐ground dry matter. The use of the ratio of growth toT/ vpd showed no improvement in growth estimation over the ratio of growth to transpiration.  相似文献   

19.
采用作物模型与数理统计相结合的方法,利用长期历史气象资料,以作物模型和地理信息系统技术为工具,系统分析了河南地区旱稻生育期水分盈亏情况。以模型模拟的雨养条件下实际蒸散量相对于潜在条件下的蒸散量(即需水量)的亏缺率,即水分亏缺指数,以雨养条件下产量相对于潜在产量的损失率(即灾损指数)作为产量灾损强度评价指标,从受旱程度和产量损失两个角度构建干旱风险评估模型,进行干旱风险评估。结果表明:河南省旱稻生育期集中在6—9月,水分亏缺最多的阶段为出苗—穗分化阶段,水分亏缺指数变化在0.50~0.60,其次是开花—成熟阶段和穗分化—开花阶段,水分亏缺指数变化在0.11~0.43;全生育期水分亏缺指数在0.36~0.50。出苗—穗分化阶段干旱发生的风险最大,其次是开花—成熟阶段,穗分化—开花阶段的最小。河南旱稻生育期干旱风险呈现为由东南向西北逐渐升高的分布,其中三门峡、济源西部一带风险最高,洛阳南部和南阳西北部一带最低,黄河以北大部地区和豫东、豫南地区风险居中。  相似文献   

20.
The potential effect of climate change on durum wheat in Tunisia is assessed using a simple crop simulation model and a climate projection for the 2071–2100 period, obtained from the Météo-France ARPEGE-Climate atmospheric model run under the IPCC (International Panel on Climate Change) scenario A1B. In the process-oriented crop model, phenology is estimated through thermal time. Water balance is calculated on a daily basis by means of a simple modelling of actual evapotranspiration involving reference evapotranspiration, crop coefficients and some basic soil characteristics. The impact of crop water deficit on yield is accounted for through the linear crop-water production function developed by the FAO (Food and Agriculture Organization of the United Nations). Two stations are chosen to study the climate change effect. They are representative of the main areas where cereals are grown in Tunisia: Jendouba in the northern region and Kairouan in the central region. In the future scenario, temperature systematically increases, whereas precipitation increases or decreases depending on the location and the period of the year. Mean annual precipitation declines in Jendouba and raises in Kairouan. Under climate change, the water conditions needed for sowing occur earlier and cycle lengths are reduced in both locations. Crop water deficit and the corresponding deficit in crop yield happen to be slightly lower in Kairouan; conversely, they become higher in Jendouba.  相似文献   

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