| The 24 solar terms are the crystallization of many disciplines such as phenology,meteorology and agronomy in ancient China.The information on the order of time and the change of phenology,which is reflected by 24 solar terms,has important guiding significance for agricultural activities.With global warming,the spatial and temporal distribution of climatic elements in the 24 solar terms will change inevitably.Based on the climatic data of daily average temperature,maximum temperature,minimum temperature,precipitation and sunshine hours in 86 meteorological stations from 1960-2016 and the winter wheat phenophase data in 38 agricultural meteorological stations from 1993 to 2012 in the main planted areas of winter wheat in China,Using the linear regression analysis,Mann-Kendall test,sliding T-test,correlation analysis and Arcgis10.0 to analyze the characteristics of climate change of twenty-four solar terms in the main planted areas of winter wheat in China.The results indicated:(1)The maximum temperature,average temperature and minimum temperature of the 24 solar terms in the main planted areas of winter wheat in China in 1960-2016 are all increasing,with the lowest temperature warming the most significant.The highest temperature in a year occurred during Great Heat,and the minimum temperature occurred during Slight Cold.The temperature fluctuated largely during the days around Pure Brightness and Beginning of Winter.The variation range of the daily temperature difference and the temperature difference between two adjacent solar terms between the spring and the autumn type solar terms are both large.In terms of seasonal solar terms,the spring solar terms warming most significant.From the perspective of the changes of the times,the temperature of the 24 solar terms fluctuated and rised with the change of age.The temperature in 1960s and 1980s was low than average,and the temperature was high in the early 21st century.The temperature differences of 24 solar terms in1990s vareid greatly.The temperature of the Waking of Insects,Prue Brightness,Lesser Fullness of Grain,and Grain in Beard rose in the fluctuation.The warming rate of Waking of Insects and the Prue Brightness has been reached the extremely significant level.Compared to the Waking of Insects and Prue Brightness,the temperature in Lesser Fullness of Grain and Grain in Beard rose slow relatively.In the past 57 years,Waking of Insects,Prue Brightness and Grain in Beard suddenly warmed in 2000,1983 and 1997,and the temperature in Lesser Fullness of Grain did not mutate.The temperature in Waking of Insects and Prue Brightness increased from south to north in the main planted areas of winter wheat in China,while the temperature in Lesser Fullness of Grain and Grain in Beard increased from centre to east and west.Each meteorological stations in study region showed a increasing trend for average temperature in Waking of Insects and Prue Brightness.The temperature tendency rate of the stations in the region was mainly positive,but some of sites showed a weak cooling trend in Lesser Fullness of Grain and Grain in Beard.The temperature tendency rate of Waking of Insects,Prue Brightness,Lesser Fullness of Grain and Grain in Beard in the north are higher than that in the south.(2)The precipitation of 24 solar terms did not change obviously in the main planted areas of winter wheat in China from 1960 to 2016.The Great Heat solar term exhibited the largest precipitation which was 79.7mm,on the contrast,the Winter Solstice solar term exibited the smallest precipitation which was 3.3mm.Precipitation in Grain Rain-Autumnal Equinox solar terms was relatively concentrated,and the cumulative precipitation accounted for 82%of the whole year.The precipitation of Summer Solstice increased quickly,and the autumn precipitation decreased most quickly.The precipitation of more than half of 24 solar terms showed a downward trend,and the decreasing trend in spring and autumn type solar terms was relatively obvious.Only the inclination rate of precipitation in Beginning of autumn has been reached the significant level.There is no obviously decadal difference in precipitation between the 24 solar terms.The precipitation reduced first and then increased during 1960-2016.The precipitation in 1980s and 1990s is lower than the annual average,and the precipitation increased after 2000.The precipitation of phenological solar terms did not change significantly in the main planted areas of winter wheat in China from 1960 to 2016.The precipitation of Waking of Insects and Prue Brightness showed a slight downward trend,while the precipitation of Lesser Fullness of Grain and Grain in Beard showed a weak upward trend.The Lesser Fullness of Grain solar term precipitation varied violently in decadal precipitation from 1960 to 2016.In the past 57 years,only the precipitation of Grain in Beard mutated,and the year of mutation is 1971.The precipitation of Waking of Insects and Prue Brightness decreased from south to north along the latitude direction.The precipitation of Lesser Fullness of Grain and Grain in Beard decreased from south to north in the south of the study area,while the precipitation in the northern region is different.From the Waking of Insects to the Grain in Beard,The precipitation tendency rate at the most meteorological stations in the study area changed from negative to positive value.The precipitation of stations with more precipitation in the Waking of Insects,Pure Brightness and Grain in Beard showed a downward trend,while the precipitation of stations with less precipitation showed an upward trend,which will further narrow the regional gap.(3)The hours of sunshine of the 24 solar terms in the main planted areas of winter wheat in China in 1960-2016 are all decreasing except Prue Brightness and Grain Rain.Curve of sunshine duration variation of twenty-four solar terms showed a single peak at Lesser Fullness of Grain which was 8.1h and single valley at the Winter Solstice which was 5.3h.The sunshine hours of spring and autumn type solar terms is the largest.Before and after Greater Cold and the Spring Equinox,The hours of sunshine increased significantly,and the hours before and after the Summer Solstice and Beginning of Winter decreased significantly.The sunshine hours of Grain Rain increased quickly which was 0.06h/10a,and the sunshine duration of Slight Heat decreased fastest which was-0.39h/10a.As far as seasonal solar terms are concerned,the decreasing trend of sunshine hours from strong to weak is as follows:summer type solar terms>winter type solar terms>autumn type solar terms>spring type solar terms.The changing characteristics of sunshine were obvious,and the sunshine duration decreased with the increase of age.The sunshine hours of 2000s and 2010s were lower than the average values,which of 1960s and 1970s were higher than the average values.The sunshine hours of the Waking of Insects,Prue Brightness,Lesser Fullness of Grain and Grain in Beard showed a down trend.And the decreasing rate of Waking of Insects and the Prue Brightness has been reached the extremely significant level.The sunshine duration of Pure Brightness showed a weak upward trend.The sunshine duration of Waking of Insects,Lesser Fullness of Grain and Grain in Beard mutated in 1975,1999 and 1982,respectively.The spatial characteristics of the sunshine duration of the Waking of Insects,Prue Brightness,Lesser Fullness of Grain and Grain in Beard showed that the sunshine hours increased from south to north in study area.The northern regions of Hebei,Shaanxi and Shanxi have the longest sunshine hours,while the southern regions of Henan have the shortest sunshine hours.In addition to Prue Brightness,phenological solar terms sunshine hours at the most of stations showed a downward trend.The sunhine hours of the Pure Brightness showed a slight upward trends at most stations.The decreasing rate of sunshine hours in the eastern part of the study area is higher than that in the western region.(4)The dates of overwintering,heading and maturity advanced in the main planted areas of winter wheat in China.On the other hand,The dates of sowing,emergence,tillering,greening,jointing,and milk ripen delayed in study area form 1993-2012.The duration of the whole growth period of winter wheat showed a decreasing trend,which reduced by 2.409 days per ten years.The vegetative growth stage of winter wheat shortened significantly.By contrast,the reproductive growth stage which is more important for output of winter wheat extended.The variation trend of winter wheat in phenological stages was different in different regions.The sowing stage had postponed in southern of Shanxi Province and Shandong peninsula,while the sowing stage had advanced in Henan,the southern region of Shaanxi and the northern region of the Beijing-Tianj in-Hebei region.The temporal variation of overwinter period change was not obvious,and the spatial change was not significant.Greening,heading and maturity stage had postponed in the northern region of the study area.(5)The main factor impacting wheat phenophases in the main planted areas of winter wheat in China was temperature.The duration of phenological periods showed a negative relationship with the temperature in the corresponding throttle.Precipitation and sunshine are important climatic factors that cause phenological change,and they have different influence on the duration of different phenological period.The duration from sowing to overwintering showed a significant positive relationship with the daily temperature difference and sunshine from Cold Dew to Greater Snow,and the duration from overwintering to greening showed a negative relationship with the temperature and precipitation from Greater Snow to Rains.The duration from heading to maturity showed a significant negative relationship with the highest temperature and precipitation form Grain Rain to Grain in Beard.However,the duration form heading to maturity was significantly positive relationship with the temperature difference.The duration of the whole growth period of winter wheat was negatively correlated with the temperature and precipitation from Great Snow to Grain in Beard,and the duration of phenological periods was the most sensitive to climate change in Greater Snow to Rains. |
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