| Climate conditions are the basis for the survival of the ecosystem and have a great impact on the global ecosystem.We use the temperature and monthly precipitation data of 11 meteorological stations from 1971 to 2015 in Inner Mongolia Daxing ' anling forest region,analysis the characteristics of forestry related climate indicators and the changes of main climatic factors,tha provides a scientific basis for the study of the response of forests to climate change in high latitudes in China.Main conclusion is:(1)In recent 45 years,the precipitation showed an upward trend in spring,summer and winter,the trend of interannual variation is 4.5mm/10 a,2.0mm/10 a and 3.5mm/10 a respectively.Autumn precipitation showed a decreasing trend(-1.1mm/10a).The annual precipitation shows a rising trend(8.9mm/10a),but the change trend was not passed the significance test at the level of ? < 0.01,the mean annual precipitation is 465 mm.Seasonal and annual precipitation changes occured 1-3 distinct mutations.The precipitation in the four seasons contains periodic changes of several different time scales,the annual precipitation has only 1 obvious periodic changes of 27-30 a time scales.The spatial distribution of precipitation tendency rate in the four seasons and the whole year was different.(2)The four seasons and the annual mean temperature showed an upward trend,among which the spring,summer,autumn and annual average temperature increased significantly,but the winter temperature rising trend not passed the significance test at the level of ? < 0.01.The average temperature rise rate in the four seasons was 0.48?/10 a,0.46?/10 a,0.47?/10 a and 0.35?/10 a respectively.The increase in annual mean air temperature of 0.42?/10 a.The seasonal and annual average temperatures contains periodic changes of several different time scales;The seasonal average temperature and annual average temperature contains at least 1 times warming mutation,the mutation in spring is the earliest,followed by winter,autumn and summer.The climate tendency rate of annual average temperature spatial distribution showed increasing trend.(3)The frost-free period showed an increasing trend,the change rate was 5.2d/10 a,the first day of frost-free period showed a trend in advance,however the last day of frost-free period showed trend of delay,the change rate was 3.4d/10 a and 1.8d/10 a respectively.The change trend of frost-free days,frost-free first day and frost-free day is not obvious in the middle of the forest region,and the range of variation is small,while the margin of forest region is relatively large.Pearson regression analysis showed that frost-free days,frost-free first day and frost-free day and annual average temperature,annual mean minimum temperature has a close relationship.(4)The number of days in 0 ?growing season showed a significant upward trend(3.38d/10a?),the average value was 196 d,and the number of days in 5? growing season showed a significant upward trend,the interannual variation rate was 3.33 d/10 a.The start date of growth season at 0 ?and 5 ?showed a trend of change in advance,and the end date showed a trend of delaying.Pearson regression analysis showed that the three indexes of growth season at 0? and 5 have a high correlation with the average tem? perature,the lowest temperature and the highest temperature. |
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