Study On Growing Season And Analysis Of Its Influence Factors In Beijing Based On Modis Data

At present, more and more evidence that global climate is gradually warming, and plant phenology is the integrator of global change and natural environmental change indicator. The phenological response to climate change is becoming a hot issue of global change. Forests are an important part of the global ecosystem, and forest phenology biological indicators reflect the impact of short-term or long-term climate change on forest growth stage. Based on time-series analysis software TIMESAT, using double Logistic curve fit method, reconstructing MODIS-NDVI data and extracting growing season start date, end date and length of deciduous forest in Beijing in2001-2009, then analyzes the relationship between growing season climate changes and elevation. The conclusion is as follows:(1) In2001-2009, growing season start date of deciduous forest in Beijing area begins in mid-April to late April (100-120days). Among them, the growing season in deciduous forests in2006has late start date, and begins in mid-May to late May (130-150days). Using the linear fitting method to fit the growing season start date for9years, we find that the growing season start date in most parts is ahead of trends, the length of time is in advance for2-6days.(2) The growing season end in most of the deciduous forest area begins in mid-October to late October (290-310days).9years of the growing season end date in Beijing has a postponed trend in most parts,and delays a length of time for2-4days.(3) The length of growing season in majority of deciduous forest area is190-210days, the minimal length of growing season is less than160days. In2006, the growing season length is170-180d; In2007, length of growing season in most of the deciduous forest area is longer, between200-210days.9years in length of growing season in Beijing has a trend of2-4days in ahead.(4) The closer to city, the earlier to growing season start date, of Growing season start of deciduous forest in urban edge have an average of10-30days earlier than in the mountains.(5)At an altitude of300-800meters, growing season start date delay of0.2-1.4days/100m; At an altitude of800-1500meters, growing season start date delay of0.1-1.9days/100m; At an altitude of1500-1700meters, growing season start date delay of1.1-3.5days/100m; Compared the result to the average of the ground phenological survey data, the result is18days later. Remote sensing phenology monitoring of the overall mixed types of phenological changes, so the extraction of phenological date is later than the date of ground-based observations.(6) At an altitude of300-800meters, growing season end date put an advance of0.1-1.5days/100m; At an altitude of800-1500meters, growing season end date put an advance of0.6-1.8days/100m; At an altitude of1500-1700meters, growing season end date put an advance of1.3-3.0days/100m;(7) The growing season start date has a certain correlation with the average temperature, precipitation and sunshine. April temperature is increased by1℃, the growing season start date is4days in advance. Growing season start date of the growing season was not obvious to the end date and meteorological factors.