Plant Phenological Pattern And Its Influencing Factors In The Tarim River Basin

Vegetation phenology as a periodic feature of the adaptability of vegetation to the external environment,is an important role of ecosystem change.Therefore,the inversion and change monitoring of vegetation phenology help to understand the impact mechanism of global climate and environmental change on the ecosystem.With the rapid development of remote sensing technology,it has made up for the lack of spatial representation of traditional phenological observation at traditional stations and been widely used in long term monitoring on vegetation phenology.The uneven distribution of ecological monitoring stations and weather stations have led to the limitations of phenological monitoring in the basin.This paper selected the vegetation of the Tarim River Basin sensitive to climate change as the research object,and used remote sensing and geographic information system to reconstruct the long term vegetation index of the basin.Relevant inversion and analysis of the parameters were carried out,then the start of growing season(SOG),the end of growing season(EOG)and the length of growing season(LOG)were respectively extracted.And the spatio-temporal characteristics analysis and change monitoring were performed.In addition,the effects of influencing factors on vegetation phenology were further analyzed.The main conclusions were as follows:(1)By extracting the phenological parameters of the basin,this paper analyzed the vertical and horizontal zonal differentiation characteristics and interannual variation trends of each parameter.From 2000 to 2019,the SOG was mainly concentrated from the 80 th day to the 170 th day,showing a delayed distribution pattern gradually from northwest to southeast.The EOG was between the 290 th day and the 330 th day.The phenological changes of vegetation in the basin differed significantly in different altitude zones.The overall SOG in the basin was considered to be a slight delay in the rate of 0.5 d/10 a.The average changing rate of EOG was 2.3 d/10 a,showing a delayed trend.The SOG with delayed trend was mainly distributed in the central western and the northeastern edge region.In area where the SOG was advanced,the EOG also tended to advance significantly.(2)To research the response of the SOG and EOG to climate variables,the main controlling factors of vegetation phenology changes in different regions were analyzed.The SOG in the southwestern part was mainly controlled by temperature.As the temperature rose,the SOG came significantly earlier.The SOG controlled by precipitation was mainly distributed in the northeast and northwest part.The increase of precipitation can significantly promote the SOG.And the decrease of humidity will cause the water loss of the vegetation environment and the vegetation itself,which had a certain delay effect on the occurrence of SOG in the eastern part.The EOG in the southwest part was significantly affected by temperature.When the temperature rose,the EOG was obviously delayed.And the increase of precipitation during the growth of vegetation pushed the EOG to delay,especially in the northeast part.In the east marginal area and some parts of the southwest,the EOG had a greater control effect,which the increase of relative humidity will cause a significant delay of the EOG.(3)Based on the transfer matrix,the vegetation phenology change of different land use types of the basin was analyzed.The average SOG of cultivated land gradually delayed,but for woodland and grassland,the average SOG gradually advanced.The average EOG of grassland had a delayed trend.And the average EOG of cultivated land had a lower rising trend than that of grassland.But for the average EOG of woodland,it had an advanced trend.50% of the average SOG change rate of land use transfer types was positive,indicating that half of the SOG in the basin was delayed.For more than 60% of the land use transfer types,the average vegetation EOG change rate was negative,indicating that most of the EOG was advanced.(4)Winter precipitation and temperature in the previous year and altitude were the main factors affecting the change of the SOG,Followed by precipitation and relative humidity in spring.The interaction of each factor showed that the superposition of each factor greatly enhanced the independent impact on vegetation.Nonlinear synergy occurred in winter precipitation in the previous year with spring relative humidity and altitude,indicating that spring relative humidity and altitude promoted the impact of winter precipitation in the previous year on the SOG.Spring precipitation with winter temperature in the previous year,spring relative humidity,and altitude accelerated the impact of the spring precipitation on the SOG.And spring relative humidity and altitude enhanced the impact of winter temperature in the previous year on the SOG.Therefore,winter temperature in the previous year,spring relative humidity,and altitude can be used as auxiliary factors to monitor the SOG.Autumn relative humidity,altitude,and summer temperature were the main factors affecting the EOG,followed by autumn precipitation and summer relative humidity.The interaction of various factors showed that autumn precipitation with summer temperature,summer relative humidity,and altitude showed a nonlinear synergistic effect on the EOG,indicating that summer temperature and relative humidity,and altitude enhance the influence of autumn precipitation on the EOG.Therefore,summer temperature and relative humidity,and altitude can be used as auxiliary factors to monitor the EOG.