| The Tibetan Plateau is known as "Chinese water tower",which is the source of several large rivers,and is closely related to changes in the global ecosystem,the function of water conservation is particularly important.Soil moisture connects different biosphere circles and as the carrier of material exchange and energy transfer between them,and have an important impact on water circulation,ecological protection and climate change,and also have a corresponding response to their changes.In order to understand the temporal and spatial distribution of soil moisture in the Tibetan plateau and reveal the role of climate change on the process and the influence degree to it,this study is based on the remote sensing monitoring methods,from interannual,growing and non-growing season,seasonal,ecological geography,vegetation types and soil types,analyzing the temporal and spatial differences of soil water-heat patterns in the Tibetan plateau from 1981 to 2013.The results show that:(1)In 1981-2013,an average annual rainfall of the Tibetan Plateau showed increasing trend in fluctuation,the growing seasonal precipitation almost every year is four times that of non-growing season's and growth rate is much higher than the latter,precipitation during 1997-1998 mutations,and increased significantly after 1998,there are differences between rainfall in seasons,spring,summer,and autumn showed a trend of increase,while winter is a decreasing trend,but reducing rate is small,trend is also not significant.Uneven distribution of precipitation in the space,the overall performance of more in the eastern part and less in the western part,from southeast to northwest gradually decreasing characteristics,and has obvious transitional zone,the change rate also shows the increased track from northwest,north,and southeast to the central and southern.(2)1981-2013,the annual average temperature of the Tibetan Plateau shows the upward trend in fluctuations,and average temperature is-2 ?.Temperature in growing season and the non-growing season were significantly increased,and the rise rate in growing season higher than that of non-growing season.The mutation of the temperature happened in 1995,and after 2001,the trend of the temperature increase significantly.The average temperature of the four seasons are the rising trend of fluctuations,the average for many years order from high to low was: summer,spring,autumn,and winter.Temperature distribution in space gradually increased from the northwest inland to the Qaidam Basin,and temperature in various regions is on the rise in the past 33 years of the Tibetan Plateau.(3)From 1980 to 2013,the Tibetan Plateau soil moisture showed increasing significant trend of fluctuations,and in the 80 s decline significantly,while increase significantly in the 90 s;in the entire study period,growing seasonal and non-growing seasonal soil moisture all showed rising trend in fluctuation and the former rapidly rising faster than the latter;the content order of average soil water in four seasons is as follows: summer,autumn,spring and winter;and they all show a upward trend,but there are differences between seasons,with the increase of the summer trend is most obvious,followed by the fall,winter is the most stable,can be considered as nearly 34 years did not change,and summer and autumn seasonal soil moisture is the largest contribution to the total in the Tibetan Plateau.(4)The soil moisture of the Tibetan Plateau in space showing the overall east than in West,and distribution gradually decreasing from east to west,in addition to the northwest,the water content is relatively high in the edge of Tibetan Plateau,while the northwest is dryer,and the average value in inland of northwest is very low;soil moisture in the ecological geographic regions,VA6 and HIIA/ B1 region's is highest,followed by HIIC2,HIIC1 and HIB1 area,the smallest is HIC2 and HID1 area;The vegetation type,soil moisture for coniferous forest,shrub and broadleaf forest distribution area average value is relatively large,and the minimum value of soil moisture is grassland and desert areas;and in soil types value,the highest average is cold desert soils,followed by luvisols,ferralsol,dark felty soils,semi-luvisols and Felty soils,the smallest is the desert soil,primitive soil,saline-alkali soil,frigid calcic soils and cold desert soil;soil water in spatial variability of the Tibetan Plateau and the ecological geographic regions are characterized by medium variability,showed that soil moisture in different scales have good space structure.(5)Nearly 33 years,soil moisture content of the Tibetan Plateau is affected significantly by the temperature,the rise of temperature makes the seasonal frozen soil thawing and snow line up,and glaciers are melting increased,increases surface runoff,lead to soil moisture increase.Soil moisture has a lag of temperature;the influence of precipitation on soil moisture is not obvious.There is no significant correlation between soil moisture and precipitation in the Tibetan Plateau,but there is a significant correlation with temperature. |
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