| The dynamic of vegetation activity and its responses to climate change have become a hot research topic in the background of global climate change.Due to its unique hydrothermal conditions,the vegetation activity and its response to climate change in southern subtropical monsoon region is very different when they are in arid and semi-arid regions.This paper compared and analyzed the difference of vegetation response with different vegetation cover to different time scales in Southern subtropical monsoon region,and provided an important basis for forest management and decision-making under climate change.Based on the daily meteorological observation data of the Fujian Provincial Meteorological Station from 1960 to 2017,we selected the commonly applicable meteorological drought indices in the subtropical monsoon region by calculating five drought indices and combining historical drought data.Using MODIS-EVI data and monthly meteorological data,we selected appropriate methods to extract phenology and calculated drought index at different time scales,then we analyzed the response characteristics of different tree species' EVI and key phenological parameters SOS?EOS and LOS to temperature,precipitation and meteorological drought index.Studies have shown that:(1)CInew,MI and Pa are suitable for monitoring extreme drought events and severe drought events,and SPEI and SPI are suitable for monitoring moderate drought and light drought events.When SPEI monitored a drought events,it's result was consistent with the mechanism of drought occurrence and the description of drought was consistent with the actual situation.SPEI is suitable for southern subtropical monsoon region;(2)Double Logistic combine and seasonal amplitude method has the highest precision when we extract phenology after the threshold was set to 0.1.The method is to delay the start time of the growing season SOS,the end time EOS,and the length LOS by 32 days,26 days,and 11 days respectively.(3)Vegetation coverage,EVI and precipitation increased significantly in the study area during the 18 years,the temperature decreased,hitting that the humidity increased.The increasing speed of EVI and the frequency of drought occurred in spring was greater than that in summer;(4)The start of the growing season is about 96-128 days,the end time is about 224-256 days,and the length is 144-155 days.The start time and end time of the growing season have a post-delay trend,which is 3.8 days/10a,0.67 days/10a,respectively,and the growth season length decreases by 2.2 days/10a;(5)the lag time of vegetation to climate is about 22-36 months,,EVI was more affected by precipitation than the temperature in the initial and final period of growing season,and EVI response to drought changes was the most obvious,the coverage change was more affected by temperature than precipitation,and the long-term sequence of drought and flood changes was significant correlation with the coverage in the initial period of growing season;(6)In the short-term,natural forests are more susceptible to climate change than plantations,and plantations on long-term scales are more vulnerable to climate change.The rank that the sensitivity of forests to climate change is:Phyllostachys heterocycla>broadleaf species>Cunninghamia lanceolata>Pinus massoniana Lamb,so we should pay careful attention to the impact of climate change on natural forests and the impact of long-term climate change on plantations when in production and management.(7)The influence of precipitation is greater than the temperature at the beginning of the growing season.The increase of the humidity in the short-term time scale will lead to the delay of the growing season,while the increase of the humidity on the long-term scale will promote the germination of the vegetation.The LOS is more affected by temperature than the precipitation in the end of the growing season,and the decrease in humidity in the area will lead to an extension of the growing season. |
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