Spatial And Temporal Variation Of Vegetation Phenology And Its Response To Climate Change In Inner Mongolia

Phenology of vegetation refers to the periodic change of vegetation caused by environmental impact,especially by temperature and precipitation.Vegetation is sensitive to climate change,and different vegetation phenology shows different distribution patterns in time and space.The response of vegetation phenology to climate change has received more and more attention.In this study,the extreme value method of the fitted logistic curvature of cumulative NDVI was used to extract three phenological data of vegetation in Inner Mongolia from 1982 to 2015,namely start of growing season(SOS),end of growing season(EOS)and the length of growing season(LOS),to analyze the trend of vegetation phenology and its response to climate.The results show:(1)In Inner Mongolia,SOS of vegetation is mainly concentrated between the 82 nd and 162 th days,EOS of vegetation is mainly concentrated between 246 th and 276 th days,LOS lasts approximately 91 and 181 days.In spatial,SOS is early in the southwest and late in the northeast,and EOS is early in the northeast and late in the southwest,and LOS is short in the northeast and long in the southwest.In temporal,there is no obvious trend change in SOS,EOS presents an advanced trend,and LOS presents a shorten trend.The turning points of SOS,EOS,and LOS occurred in 2009,2008,and 2009 respectively.Before the turning point,there was no obvious trend change in the three phenologicaldata.After the turning point,SOS,EOS and LOS showed a trend of delay,advance and shorten.(2)In spatial,the temperature in Inner Mongolia shows a decreasing trend from southwest to northeast.The precipitation in Inner Mongolia generally shows a decreasing trend from northeast to southwest.The average temperature in the spring(March-May)and late-summer and early autumn(August-October)in Inner Mongolia did not change significantly.The trend of precipitation in March to April was not obvious,and in May was on the rise.The precipitation in August showed a decreasing trend,and in September and October wasnot obvious.The turning point of temperature in March to May was 1993,1998 and 2012,respectively.The turning point of temperature in August to October is 2011,2005 and 2000 respectively.The turning points of precipitation in March to May were as in 2008,1986 and 1994,respectively.The turning point of precipitation in August to October was 2012,2007 and 1995 respectively.(3)The SOS of Inner Mongolia has the most obvious response to March temperature and March precipitation.The increase in temperature will prompt the advancement of SOS in most areas of Inner Mongolia,but the increase in precipitation promotes the delay of SOS.This is related to the temperature in Inner Mongolia at 0?in March,that is,the precipitation increases and the temperature do not reach the demand for SOS.EOS has the most obvious response to August temperature and August precipitation.The increased temperature and the reduction in precipitation promoteadvances in EOS.The SOS response to spring(March-May)temperature is more pronounced,especially in the forest,where the temperature rises will promotes SOS advance.The response of EOS to temperature and precipitation in late summer and early autumn(August-October)is not obvious.The SOS of forests and grasslands has a negative correlation with the temperature of each month.The increase of temperature will promote the advance of SOS.The SOS of shrubs and sandy land are not related to the temperature of each month.The forest SOS has a positive correlation with the monthly precipitation.The SOS of grassland,shrubs,and sand are not related to precipitation in each month.Forest EOS is negatively correlated with monthly temperature.The EOS of grassland,shrubs,and sandy are not related to the temperature of each month.The EOS of forests,grasslands,shrubs and sandy land showed a negative correlation with precipitation in each month.(4)There is a relationship between SOS,EOS and LOS.The advance of SOS will lead to the advance of EOS,the advance of SOS will promote LOS extension,and the early stage of EOS will lead to the shortened of LOS.The correlation between SOS and LOS,EOS and LOS is very high.And the effect of SOS on LOS is greater than the effect of EOS on LOS.