Variations of Frost-free Period and Its Impact on Grain Yields in Henan Province during 1961-2013

Junhui YAN,Hui FU,Hongsheng ZHOU,Xinchuang XU

1.College of Urban and Environmental Sciences,Xinyang Normal University,Xinyang 464000,China;

2.College of Geography and Tourism,Chongqing Normal University,Chongqing 400047,China

3.Southern Henan center for mineral rock and gem-jade identification and processing,Xinyang Normal University,Xinyang 464000,China

4.The School of Resources Environment Science and Technology,Hubei University of Science and Technology,Xianning 437100,China

5.Key Laboratory of Land Surface Pattern and Simulation,Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences,Beijing 100101,China

Variations of Frost-free Period and Its Impact on Grain Yields in Henan Province during 1961-2013

Junhui YAN1*,Hui FU2,Hongsheng ZHOU1,3,Xinchuang XU4,5*

1.College of Urban and Environmental Sciences,Xinyang Normal University,Xinyang 464000,China;

2.College of Geography and Tourism,Chongqing Normal University,Chongqing 400047,China

3.Southern Henan center for mineral rock and gem-jade identification and processing,Xinyang Normal University,Xinyang 464000,China

4.The School of Resources Environment Science and Technology,Hubei University of Science and Technology,Xianning 437100,China

5.Key Laboratory of Land Surface Pattern and Simulation,Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences,Beijing 100101,China

The aim of this study was to investigate the responses of frost dates to global warming and its influences on grain yields.In this study,based on the frost date series defined by daily minimum ground temperature,the spatial and temporal characteristics of first frost date (FFD),last frost date (LFD)and frost-free period (FFP)were analyzed.The impact of extending FFP on major crop yields was also studied.The results were as follows:FFD showed a significantly delaying trend of 2.2 d/10 y,and LFD presented an advancing trend of 2.4 d/10 y.FFP extended at a rate of 4.5 d/10 y due to the later FFD and earlier LFD.The most obvious trend of FFD was in western Henan,while the most significant trend of LFD and FFP occurred in south central parts of the study area.However,in eastern region,the trends of FFD,LFD and FFP were not so obvious.Major crop yield showed a significant correlation with frost-free period for Henan during 1961-2013.The yields of grain,rice,wheat,and maize increased by 79.5,90.0,79.5 and 70.5 kg/hm2with FFP extending by one day.

Dailyminimum ground temperature;Frost-free period;Grain yield; Henan province;1961-2013

T he IPCC Fifth Assessment Report(AR5)pointed out that the globally averaged combined land and ocean surface temperature has increased by 0.85℃ [0.65℃to 1.06℃]over the period 1880 to 2012[1]. This warming trend has also been observed in China[2].Under this warming background,there isincreasing concern thatglobalwarming has brought key effects on ecological system,agriculturalenvironmentand crop yields[3].In China,the impacts of climate change on agriculture have been comprehensively reviewed[4].Using improved datasets of crop production by county,Tao et al.investigated climate trends during the growing period and their impacts on crop yields[5]. Li et al.found that natural disasters deeply influence the security of the crop’s production by analyzing the relationship between crop production and the influence factors[6].Frost-free period is an important index of heat in agriculture,which has an important impact on crop yield and quality[7]. The frost-free period lengthened during the past 50 years due to the later first frost date and the earlier last frost date[8-11].However,the quantitative relationship between this prolonged period and grain yield has not been as well understood.The study attempted to investigate the statistical relationship between frost-free period andyields of major crops(rice,wheat,and maize)in Henan province,using linear regression model.This study will help to improve the adaptability of agricultural system to climate change and ensure China’s food security.

Data and Methods

Data sources

Two types of data were used in this study,meteorological data and grain yield data of major crops.China monthly surface climate data from 1961-2013 are published every year by the Chinese Meteorological Administration (CMA).To obtain the starting and ending date of frost-free period in Henan province,the research downloaded daily minimum ground temperature data of 17 stations from the CMA website(http://cdc.cma.gov.cn) (Fig.1).The meteorological data were derived from instrumental measurements,and quality assurance checks were undertaken,including examining the data for completeness,reasonableness and accuracy.Major crop yield data were obtained from China Statistical Yearbook.

Methodology

Frost is a deposit of small white ice crystals formed on the ground or other surfaces when the temperature falls below freezing[12].It is difficult to obtain a continuous longer frost date series,due to the fact that frost observation data are usually missing in early years for some reason[13].Some researchers have defined frost dates by surface ground temperature and air temperature in precious studies[9,14-19]. However,Han et al.found that frost date defined by surface ground temperature was very close to first frost observation date[20].Hence,the research used daily minimum ground temperature to define frost dates.First frost date(FFD)is defined as the surface ground temperature falls below 0℃ for the first time in autumn,while last frost date (LFD)is defined as the surface ground temperature rises above 0℃for the first time in spring time.The period between FFD and LFD is defined as frost-free period (FFP).

It analyzed the long-term frost trends by calculating the regression coefficients using simple linear regression model.The coefficient k was computed as follows:

Note that assuming the linear regression y=kx+b,predictor(x)is the year,and the predictant (y)is frost date anomaly with the reference period of 1961-1990.It analyzed the spatial characteristics of FFD,LFD and FFP by plotting the trend coefficients on map using ArcGIS software.

Results

The temporal variations of FFD, LFD and FFP

Fig.2 presents the regional interannual variations of FFD,LFD andFFP during 1961-2013.FFD shows a significantly delaying trend while LFD indicates a significantly advancing trend.The FFP extends during the past 53 years due to the later first frost date and the earlier last frost date.The trend coefficients of FFD,LFD and FFP are 0.22,0.24,and 0.45 d/y,respectively.Meaning that FFD is postponed for 11.5 days and LFD is advanced for 12.9 days during the past 53 years.As a result,FFP lengthens for 23.6 days during the past 53 years. It is worth noting that the inter-annual variation of LFD is a little larger than that of FFD,and the inter-annual variation of FFP is much larger than that of LFD.

On decadal timescales,FFD changed little before 2000.However,it delayed markedly since the 21stcentury.FFD of 2001-2010 is postponed for 9 days compared to 1961-1970 mean. Unlike FFD,LFD was obvious ahead of time since 1980s,especially after 2000.Mean LFD of 2001-2010 is advanced for 13 days than that of 1961-1970.FFP has almost no obvious trend in the 1960s and 1970s.It began to extend since 1980s,especially after 2000.Mean FFP of 2001-2010 has prolonged for 22 days than 1961-1970 (Table 1).

The spatial variations of FFD,LFD and FFP

Fig.3 shows the spatial trend map of FFD,LFD and FFP.In all stations except Gushi,FFD shows a significantly delaying trend during the past 53 years.But the magnitude varies from region to region.The largest delaying trend occurs in the western region of Henan Province,with the maximum value occurring in Lushi(with a trend of 4.0 d/10 y).However,in eastern region,the delaying trend is not obvious,with the minimum delaying trend locating in Shangqiu (with a trend of 1.1 d/10 y).In Gushi,however, FFD is slightly advanced during the period 1961-2013 (at a rate of-0.3 d/10 y).Unlike FFD,LFD in all stations presents a significantly advancing trend.These trends are ranging from 1.2 to 4.6 d/10 y,with the maximum trend occurring in Zhumadian and minimum trend locating in Gushi.The most obvious trend occurs in south central region.But in eastern region, the trend is not so obvious.

Due to the later FFD and earlier LFD,FFP shows an extending trend in Henan province.The magnitude is ranged from 2.3 to 38.3 days during the past 53 years.The most obvious trend occurs in south central region. However,in eastern region,the trend is not so obvious.Our results are consistent with previous studies[8-11],although there are some minor differences.For instance,the amplitude of changing trend varies in different studies.These differences may be due to the following reasons.On the one hand,data source used to define FFD and LFD are different.On the otherhand,different study area and reference period may be the causes of these differences.

Table 1 Decadal change of FFD,LFD and FFP

Table 2 Linear regression between FFP and grain yield

The relationship between frost-free period and grain yield

The impactsoffroston major crops have been studied previously[20-25],but these studies mainly focused on the abnormal frost events and its influence on agriculture. The relationship between frost-free period and grain yield is not clear.To answer this question,the research established regression equations using FFP as predictors and crop yields as predictant.

The major crop yields show a significant correlation,ranging from 0.53 to 0.61,with frost-free period(Table 2). All equations passed the 99%confidence level.The value of F statistic is high,considering that the 95th percentile of its distribution under the null hypothesis of no real relationship is about 4.02.So using these equations, the quantitatively relationship can be investigated between the extendingFFP and crop yields.The regression coefficient between gain yield and FFP is 5.33,representing that gain yield increases by 79.5 kg/hm2when FFP extends by one day.Of the 3 major crops,rice yield is the most sensitive to FFP,which increases by 90 kg/hm2with FFP extends by one day.Wheat and maize yields increase by 79.5 kg/hm2and 70.5 kg/hm2,respectively, when FFP extends by a single day.

Conclusions

In this paper,the research defined frost dates by using daily minimum ground temperature.And then the research analyzed the temporal and spatialcharacteristics offirstfrost date,last frost date and frost-free period during the past 53 years.The research also investigated the influence of the extending FFP on major crop yields.The main conclusions are summarized as follows:

During the past 53 years,FFD showed a significantly delaying trend, and LFD showed an advancing trend. FFP lengthed due to the later FFD and earlier LFD.The trend coefficients of FFD,LFD and FFP are 0.217,0.244 and 0.445 d/y,respectively.

There existed some minor differences in the trend of FFD,LFD and FFP on decadal time scales.FFD obviously delayed since the 21thcentury, while LFD was obviously ahead of time since 1980s.FFP has almost no obvious trend in the 1960s and 1970s. It began to extend since 1980s,especially after 2010.

The trend of FFD,LFD and FFP at all stations is consistent,but the magnitude varies in different stations. The most obvious trend of FFD is in eastern region.And the most obvious trend of LFD and FFP occurs in south central region.However,in eastern region,the trend of FFD,LFD and FFP is not so obvious.

The major crop yields show a significant correlation,ranging from 0.53 to 0.61 with frost-free period.The yields of grain,wheat,rice,and maize increase by 79.5,79.5,90,and 70.5 kg/hm2when FFP extends by one day.

[1]IPCC,2013:Summary for Policymakers.In:Climate Change 2013:The Physical Science Basis.Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker,T. F.,D.Qin,G.-K.Plattner,M.Tignor,S. K.Allen,J.Boschung,A.Nauels,Y.Xia,V.Bex and P.M.Midgley(eds.)][M]. Cambridge UniversityPress,Cambridge,United Kingdom and New York, NY,USA.

[2]ECSCNARCC(Editorial Committee for Second China’s National Assessment Report on Climate Change)(《第二次气候变化国家评估报告》编写委员会). Second China’s National Assessment Report on Climate Change(第二次气候变化国家评估报告)[M].Beijing:Science Press(北京:科学出版社),2011: 38-40.

[3]SAMUEL HITZ,JOEL SMITH.Estimating global impacts from climate change [J].GlobalEnvironmentalChange, 2004,14(3):201-218.

[4]LIU QY,ZHENG JY,GE QS.Effects of global climate change on China’s agriculture[J].Chinese Agricultural Science Bulletin,2008,24(12):447-453.

[5]TAO FL,ZHANG Z,ZHANG S,et al. Response of crop yields to climate trends since 1980 in China [J].CLIMATE RESEARCH,2012,54(3):233-247.

[6]LI MS(李茂松),LI ZC(李章成),WANG DL(王道龙),et al.Impacts of natural disasters change on grain yield in China in the past 50 years(50年来我国自然灾害变化对粮食产量的影响)[J].JOURNAL OF NATURAL DISASTERS(自然灾害学报),2005,14(2):55-60.

[7]HE FF(贺芳芳),GU XD(顾旭东),XU JL (徐家良).Studies on heat resources change in Shanghai since 1990’s(20世纪90年代以来上海地区光能资源变化研究)[J].JOURNAL OF NATURAL RESOURCES(自然资源学报),2005,20 (6):806-813.

[8]XU Y(许艳),WANG GF(王国复),WANG PX(王盘兴).Climatic change of frost in China in recent 50 a(近50 a中国霜期的变化特征分析)[J].SCIENTIA METEOROLOGICA SINICA(气象科学),2009, 29(4):427-433.

[9]YE DX(叶殿秀),ZHANG Y(张勇).Characteristic of frost changes from 1961 to 2007 over China(1961-2007年我国霜冻变化特征)[J].JOURNAL OF APPLIED METEOROLOGICAL SCIENCE (应用气象学报),2008,19(6):661-665.

[10]WANG GF(王国复),XU Y(许艳),ZHU YJ(朱燕君),et al.The spatial and temporal characteristics and trend of frost days over China for the past 50 years (近50年我国霜期的时空分布及变化趋势分析)[J].METEOROLOGICAL MONTHLY(气象),2009,35(7):61-67.

[11]MA ZG(马柱国).Variation of frost days and its relationship to regional warming in Northern China(中国北方地区霜冻日的变化与区域增暖相互关系)[J]. ACTA GEOGRAPHIC SINICA(地理学报),2003,58(Supplement):31-37.

[12]Chinese Meteorological Administration (中国气象局).The ground meteorological observation norm(中国地面观测规范)[M].Beijing:China Meteorological Press(北京:中国气象出版社), 2003:21.

[13]LI FY(李凤云),WANG YS(王玉山), WANG RB(王荣波).The characteristic of frost occurrence and its recording method(霜的出现特点与录记方法)[J]. Journal of Guizhou Meteorology(贵州气象),2013,37(3):63-64.

[14]MA SQ(马树庆),LI F(李锋),WANG Q (王琪),et al.Cold wave and frost(寒潮和霜冻)[M].Beijing:China Meteorological Press(北京:中国气象出版社), 2009:67-68.

[15]LI X(李想),CHEN LJ(陈丽娟),ZHANG PQ(张培群).Characteristics of interdecadal variations in first-frost date in Northern China during 1954-2005 (1954-2005年长江以北地区初霜期变化趋势)[J].ADVANCES IN CLIMATE CHANGE RESEARCH(气候变化研究进展),2008,4(1):21-25.

[16]CHEN QJ(陈乾金),XIA HX(夏洪星), ZHANG YS(张永山).Analyses of unusual first and last frost during the last 40 years in the Changjiang and Huaihe valley(我国江淮流域近40年异常初终霜冻的分析)[J].Quarterly Journal of Applied Meteorology(应用气象学报), 1995,6(1):50-55.

[17]HE WX(何维勋),FENG YX(冯玉香), CAO YH(曹永华),et al.Changes of first and last frost date in Beijing during the last 50 years(北京近50年初?终霜冻日的变化)[J].Chinese Journal of A-grometeorology(中国农业气象),1992, 13(4):33-36.

[18]PAN SK(潘淑坤),ZHANG MJ(张明军), WANG BL(汪宝龙),et al.Changes of the first frost dates,last frost dates, and duration of frost-free season in Xinjiang during the period of 1960-2011(1960-2011年新疆初终霜日及无霜期的变化特征)[J].Arid Zone Research(干旱区研究).2013,30(4):735-742.

[19]FENG PZ(冯佩芝),LI CJ(李翠金),LI XQ(李小泉),et al.Analysis of Chinese main meteorological disasters(中国主要气象灾害分析)[M].Beijing:China Meteorological Press(北京:气象出版社),1985:58-59.

[20]HAN RQ(韩荣青),LI WJ(李维京),AI WX(艾婉秀),et al.The climatic variability and influence of first frost dates in Northern China(中国北方初霜冻日期变化及其对农业的影响)[J].ACTA GEOGRAPHICA SINICA(地理学报). 2010,65(5):525-532.

[21]ZHANG X(张霞),QIAN JX(钱锦霞). Frost characteristics and its effect onagriculture in Taiyuan under climate warming(气候变暖背景下太原市霜冻发生特征及其对农业的影响)[J].Chinese Journal of Agrometeorology(中国农业气象).2010,31(1):111-114.

[22]HUANG JJ(黄玖君),SHI GQ(师国强), DENG XX(邓小霞).Characteristics of frost change and its influence on main crops in Qiemo Oasis During 1961-2010(且末绿洲1961-2010年霜冻的变化特征及其对主要农作物的影响)[J]. Desert and Oasis Meteorology(沙漠与绿洲气象).2013,7(2):47-50.

[23]WANG RM(王荣梅),ZHANG XQ(张晓琴),LIU J(刘姣),et al.Frost variation and its influence on agricultural in Kashi of Xinjiang in recent 50 years(新疆喀什地区近50 a来霜冻变化特征及其对农业的影响)[J].Journal of Arid Meteorology(干旱气象).2013,31(2): 309-312.

[24]CHEN F(陈芳),WANG QC(汪青春), YIN WX(殷万秀).Characteristics of frost variations in recent 45 years over Qinghai province and its impact on major crops(青海省近45年霜冻变化特征及其对主要作物的影响)[J].Meteorological Science And Technology(气象科技).2009,37(1):35-41.

[25]LI MS(李茂松),WANG DL(王道龙), ZHONG XL(钟秀丽),et al.Current situation and prospect of research on frost of winter wheat(冬小麦霜冻害研究现状与展望)[J].Journal Of Natural Disasters(自然灾害学报),2005,14(4): 72-78.

Responsible editor:Xiaoxue WANG

Responsible proofreader:Xiaoyan WU

1961～2013年河南省无霜期变化及其对粮食产量的影响

闫军辉1*，傅辉2，周红升1,3，徐新创4,5*
（1.信阳师范学院城市与环境科学学院，信阳464000；2.重庆师范大学地理与旅游学院，重庆 400047；3.信阳师范学院豫南岩矿宝玉石鉴定及加工中心,河南信阳464000；4.湖北科技学院资源环境科学与工程学院，湖北咸宁437100；5.中国科学院地理科学与资源研究所陆地表层格局与模拟院重点实验室，北京100101）

该文的目的是研究无霜期变化对全球变暖的响应及其对粮食产量的影响。利用1961～2013年河南省17个测站均一化的逐日地面0 cm最低气温资料，根据霜冻气候指标计算了各站逐年的初、终霜日期，在此基础上分析了过去53年河南省初、终霜日期和无霜期的时空变化特征，并探讨了无霜期的变化对粮食产量的影响。结果表明：①近53年来，河南省平均初霜日期以2.2 d/10 y的速率显著推迟，平均终霜日期以2.4 d/10 y的速率显著提前，受此影响无霜期以4.5 d/10 y的速率延长；②就空间变化而言，初霜期推迟最为明显的地区位于河南西部地区，中、南部平原地区终霜期提前最为明显。东部地区初、终霜日期和无霜期变化趋势不明显；③1961～2013年河南省无霜期的变化与主要粮食产量呈显著正相关，无霜期每提前1 d，粮食总产量、稻谷、小麦和玉米分别提高79.5、90.0、79.5和70.5 kg/hm2。

日最低 0 cm地温；无霜期；粮食产量；河南省；1961～2013年

中国科学院战略性先导科技专项项目（XDA05090101，XDA05090104)；全球变化研究国家重大科学研究计划项目(2010CB950101,2012CB955403)；科技基础性工作专项项目(2011FY120300)；信阳师范学院博士科研启动基金(0201403)；国家自然科学基金项目(41271124，41101549)。

闫军辉（1983-），男，河北定州人，博士，讲师，主要研究方向为全球变化，E-mail：yanjh2015@126.com。*通讯作者。

2015-06-02

修回日期 2015-08-14

Funded by"Strategic Priority Research Program"of the Chinese Academy of Sciences (XDA05090101, XDA05090104); China GlobalChange Research Program (2010CB950101,2012CB955403);Basic Research Project of the Ministry of Science and Technology (2011FY120300);Doctor Foundation of Xinyang Normal University (0201403);National Natural Science Foundation of China(41271124,41101549).

*Corresponding author.E-mail:yanjh2015@126.com

Received:June 2,2015 Accepted:August 14,2015