The Spatiotemporal Variation Characteristics And Regional Response Of Different Growth Seasons Of Populus Euphratica In Chinese Oases Between 1960 And 2016

Phenology is the “diagnostic fingerprint” of global climate change,It can not only directly indicate the changes in natural seasons,but also reflect the response process of the ecosystem to global change.Populus euphratica is the most important natural tree in Chinese oases,the phenological change of it can indicate the climate change of Chinese oases,it can provide a theoretical basis for the restoration and reconstruction of the ecological environment in Chinese oases.Daily average temperature data and minimum temperature data from 46 meteorological stations in Chinese oases that are within the distribution area of Populus euphratica were analyzed with a multi-year trend line and using the simple kriging in the software Arc GIS to determine the spatiotemporal responses of this tree to climate change.Using stepwise regression analysis method to explore the response degree of different growing seasons of Populus euphratica to temperature of each time period.The main conclusions are as follows:(1)Over the past 57 years,the spring phenology such as the budding date,the first flowering date and the leaf unfolding date are clearly advancing with the rates of-1.31 d/10a?-1.62 d/10 a and-1.32 d/10 a,respectively.The autumn phenology of the first leaf coloring date and the defoliating date are obviously delayed,and the change tendency are 0.86 d/10 a and 1.28 d/10 a,respectively.The change trend of spring phenology is obviously greater than that of autumn.From the interdecadal change,the advancing trend in spring phenology and the delaying trend in autumn phenology are most obviously in 21 st centry.(2)The results show that although spatial disparity in different growing seasons exhibit significant regional differences,the characteristics of spatial variation remain consistent.In general,the spring phenology has tended to be delayed while autumn phenology has advanced from southwest to northeast over Chinese oases.The earliest spring phenology and the latest autumn phenology were all seen in south-western Tarim Basin in the southern Xinjiang oasis,the latest spring phenology and the earliest autumn phenology were all seen in Qaidam Basin.(3)The phenology of Chinese oases is sensitive to the response of climate warming.The spring phenology and temperature of each time period are significantly negatively correlated with one another,among them,the average temperature of the month and the average spring temperature are the most obvious.The average temperature of the preceding period and the minimum temperatures also affecting spring phenology,but not significant.The budding date,the first flowering date and the leaf unfolding date are mainly influenced by the average temperature of the month,and the Qaidam Basin is the most sensitive oasis,with the rates of-5.02 d/?,-7.09d/?and-7.84 d/?,respectively.The autumn phenology is mainly influenced by the average temperature of the month,the average temperature of autumn and the average temperature of the preceding period.And all of them are positively correlated with the autumn phenology.In addition to the defoliating date of southern Xinjiang oasis is mainly affected by the average autumn temperature,the other oases first leaf coloring date and defoliating date were mainly influenced by the average temperature.Similarly,the Qaidam basin oasis is on the most sensitive response with the rate of 6.35 d/? and 3.34 d/?.