Remote Sensing Monito Of Vegetation Phenology And Its Response To Hydrothermal Conditions In The Xilin Gol

Vegetation phenology is the sensor of ecosystem response,which is one of the important indicators reflecting climate and environmental changes due to the dual effects of temperature and precipitation.Therefore,vegetation phenology monitoring and its response to short-term and long-term Hydrothermal Conditions are the focus of current global climate change research.As an important animal product production base in China,XilinGol League is based on animal husbandry.The quality of its grassland ecological environment not only directly affects the development of local social economy,but also has an important impact on the ecological environment in northern China.Studying the relationship between phenology and climate factor change in XilinGol area has an important scientific and practical significance for better protection of grassland ecosystem and rational use of grassland resources.Based on MODIS NDVI data and meteorological data,this paper analyses the characteristics of phenology and Hydrothermal Conditions in Xilingol area for 2001-2015 years,and then analyses the correlation between vegetation phenology and climate factors at different time scales,and discusses the response mechanism of vegetation phenology to Hydrothermal Conditions.The result is as follows:(1)During the period from 2001 to 2015,the returning start of season of XilinGol was delayed from southwest to northeast,the end of season was reversed,and the length of the growing season was shortened.In terms of time,the overall return period was insignificantly delayed,and the end of season showed an early trend.Affected by the delay in returning to the start of season and the advance of the dry season,the length of the growing season was significantly shortened.This pattern is closely related to the division of temperature and precipitation in the study area.Spatially,during the return period,the central region was postponed and all other areas were advanced.Except for a small part of the southwest region,the end of seasons showed an early trend,and the end of season showed an early trend and the length of the regional growing season was shortened.The phenological period of different vegetation types showed significant differences.(2)From 2001 to 2015,the annual precipitation in XilinGol region has a significant increase trend,and the annual average temperature shows no significant downward trend.From the seasonal point of view,the changes in winter temperature and precipitation in autumn contributed most to the changes in annual average temperature and annual precipitation.Average temperature changes in the average annual,spring and autumn seasons have the largest changes in the southern part of the West Uzumuqi Banner,while the most obvious regions in which the summer temperature decreases are located in the western part of the East Ujimqin Banner.The largest changes in winter temperature are located in the northern border areas,mainly in the northern part of the Abaqin Banner.The region with the most obvious change in autumn precipitation is the northern part of East Ujumqin Banner,and the area with the most significant increase in precipitation in other seasons is in Xilinhot.(3)The response of phenological parameters to Hydrothermal Conditions is delayed by temperature and precipitation.The increase in temperature in March and the increase in precipitation in April will lead to an early return period.The decrease in temperature in September in precipitation have a significant impact on the early end of season.The length of the growing season is mainly affected by the annual average temperature and annual precipitation.The annual average temperature and precipitation increase make the length of the growing season shorter.On the smaller time scale,the returning start of season is mainly driving factors affecting the returning start of season are the precipitation of 15 days and 30 days before the arrival,and the end of season is more sensitive to the temperature of the first 5 days and the first 15 days.(4)on the spatial distribution,the northwest and southeast regions of XilinGol district are most sensitive to temperature,and only the southwestern part of the study area is sensitive to precipitation.Sandy vegetation and the end of season in most parts of typical grasslands are sensitive to the temperature response in autumn.Vegetation-sensing areas in the 15 days prior to the arrival of vegetation during the start of season are distributed in the southwestern sandy vegetation,typical grasslands,farmland vegetation areas,and typical grassland areas in the east.The end of season of the vegetation in the southwestern sand was most sensitive to the temperature change of the first 5 days.(5)Among the different vegetation types,except for sandy vegetation and farmland vegetation,the response of other vegetation types to the green temperatures in March is very obvious,except for the effects of precipitation in April on the meadow grassland and other vegetation types in sandy land.Obviously,especially the effect of precipitation on the shrubs is particularly obvious.Typical grassland,sandy vegetation,wetland vegetation,and forest end of season are very sensitive to the September temperature response.Only forest and shrub vegetation have a strong correlation with October temperatures.From the short-term scale,with the exception of meadow grassland,the returning start of season and the browning period of other vegetation types have obvious responses to the precipitation in the first 15 days and the temperature in the first 5 days.