| The Qinghai-Tibet Plateau is one of the sensitive regions of global climate change.The rise of global temperature has different degrees of influence on the spatio-temporal evolution of climate,the distribution characteristics of water resources and the future development of vegetation in different regions of the Qinghai-Tibet Plateau.The Qinghai-Tibet Plateau is also the birthplace of several rivers.The research on the dynamic response of climate gravity center and vegetation gravity center and the prediction of future vegetation coverage levels can provide a scientific basis and reference for the plateau to improve vegetation quality,monitor ecological environment,stabilize river runoff,water conservation and formulate relevant policies in the future.Taking the Tibetan Plateau in China as the research area,the measured data of daily precipitation and daily temperature of the Tibetan Plateau from 1978 to 2018 were first selected.EOF was used to analyze the typical spatial distribution pattern of the Tibetan Plateau climate.With the Tibetan Plateau precipitation elements as variables,the Tibetan Plateau was objectively divided into geographical regions using REOF.Then,statistical analysis of climate in each region is carried out to explore the temporal and spatial evolution characteristics and future trends of climate in each region.Secondly,the measured data of daily precipitation and daily maximum temperature over the Tibetan Plateau from 1978 to 2018 and the normalized vegetation NDVI data over the Tibetan Plateau from 1998 to 2019 were selected to analyze the barycentric shift characteristics of precipitation,maximum temperature and vegetation cover over the Tibetan Plateau using the barycentric shift model.Correlation analysis and partial correlation analysis were used to investigate the dynamic response of climate barycenter and vegetation barycenter migration over the Qinghai-Tibet Plateau.Finally,the GeoSOS-FLUS model was used to predict the future vegetation cover of the Qinghai-Tibet Plateau in 2035under different development scenarios by selecting driving factors such as precipitation,maximum temperature,relative humidity,sunshine duration,elevation,slope direction,spatial distribution of population,ecological protection restricted area,distance to road and distance to railway.The following conclusions were drawn:(1)The rainy areas of the Qinghai-Tibet Plateau are distributed in the southwest of the Plateau,the lower reaches of the Yarlung Zangbo River,the southeast of the Plateau,the west of Sichuan,the middle and lower reaches of the Nujiang River,the Songpan area east of the Bayankela Mountain and the head of the Three Rivers,while the less rainy areas are distributed in the south of the Qilian Mountains,the Qinghai Lake Area,the Qaidam Basin,the northern foot of the Himalayas,the Qiangtang Plateau and the west of the Pamir Plateau.The precipitation on the Qinghai-Tibet Plateau has an obvious difference between dry and wet.Its relative variability gradually decreases around the lower reaches of the Yarlung Zangbo River,the lower reaches of the Lancang River and the west of Sichuan,while its average temperature gradually increases around the southeast of Hoh Xil Mountains,the upper reaches of the Tongtian River and the southern Bayan Khara Mountains.(2)Among the 8 geographical regions obtained by REOF,precipitation in the lower reaches of the Yarlung Zangbo River tends to increase weakly;The precipitation in western Sichuan and southeastern Plateau areas showed a downward trend,decreasing by 1.5%and3.7%,respectively.Precipitation in Sanjiangyuan Region,Karakoram Range region,Qaidam Basin region,Qiangtang Plateau region and the northern foot of the Himalayas increased by8.6%,28.3%,10%,3.8%and 6%,respectively.There are five precipitation anomalies in the Karakoram Mountains region,the Qaidam Basin region,the western Sichuan region,the southeastern Plateau region and the Qiangtang Plateau region.The average annual temperature in regionsⅰ-ⅷshowed an increasing trend,with the maximum increase of 0.2℃/10a and the minimum increase of 0.11℃/10a,and the temperature increase in some regions was slightly altitudinal dependent.In the future,the longest effective influence time of past precipitation trend on future trend is 11a and the shortest is 6a.The longest temperature is 8a and the shortest temperature is 5a.(3)On the annual scale,the gravity centers of precipitation,maximum temperature and vegetation NDVI over the Qinghai-Tibet Plateau were distributed in the southeast to northwest.On the monthly scale,the overall trend of precipitation gravity center over the Qinghai-Tibet Plateau is northeast to southwest.The overall trend of the maximum temperature center of gravity is southeast to northwest;The overall trend of vegetation NDVI center of gravity was east-west distribution.On the seasonal scale,the precipitation barycenter changes obviously in spring and autumn,and July is the turning point of its barycenter track.The seasonal variation of the maximum temperature barycenter was mainly in winter with the longest migration distance,and July was the turning point of its barycenter trajectory.The seasonal variation of the center of gravity of vegetation in NDVI was mainly in summer.The average monthly migration distance in the growing season(May to October)reached 101.1km,and the turning point of the center of gravity migration was in August.The barycenter migration of annual vegetation NDVI in the Qinghai-Tibet Plateau is formed under the combined action of precipitation and the highest temperature barycenter.The overall vegetation coverage in the western part of the plateau is developing in a good direction at present.(4)Under the scenario of natural development,in 2035,the bare land area of the Qinghai-Tibet Plateau will account for 1.1×10~6km~2,low vegetation cover area will account for4.66×10~5km~2,medium vegetation cover area will account for 2.72×10~5km~2 and high vegetation cover area will account for 2.66×10~5km~2,and high vegetation cover area will account for5.02×10~5km~2.In the future,the vegetation cover level of the Qinghai-Tibet Plateau has a good trend,but the increase trend of low vegetation cover area and middle vegetation cover area will weaken.Under the ecological protection scenario,in 2035,the bare land,low vegetation cover,medium vegetation cover,medium vegetation cover and high vegetation cover will account for1×10~6km~2,4.68×10~5km~2,2.73×10~5km~2,2.93×10~5km~2 and 4.9×10~5km~2,respectively.Compared with the future vegetation coverage status of the Qinghai-Tibet Plateau following natural laws,the future vegetation of the Qinghai-Tibet Plateau is very obvious after ecological protection,and the positive trend is mainly dominated by the contribution of the middle vegetation coverage.(5)Under the two scenarios,the overall vegetation coverage of the Qinghai-Tibet Plateau under the ecological protection scenario improved better than that under the natural development scenario,and the same result was found in each REOF zone,especially in Qiangtang Plateau Area of theⅦzone.With the increase of precipitation and temperature in the future,the vegetation ecology of the Qinghai-Tibet Plateau will become better and better.The higher the altitude,the lower the vegetation coverage level.Therefore,in some areas with suitable climate and altitude,active ecological protection measures can significantly improve the vegetation coverage of the Qinghai-Tibet Plateau.It has also played a key role in the Qinghai-Tibet Plateau’s efforts to cope with global climate change,improve vegetation quality,conserve water sources,monitor the ecological environment,conserve water and soil,stabilize river runoff,mitigate flood disasters,improve water quality at the source of rivers,and reveal the interaction between earth and air. |
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