| The main body of terrestrial ecosystem-- vegetation, it can effectively regulate the global carbon balance and slow down the rising trend of greenhouse gases in the atmosphere, then there is no substitutefor maintaining global climate change and environmental change positivly. Total primary productivity(GPP), as the earliest and most basic vegetation's physiological process parameter in terrestrial ecosystem, what is an important indicator of terrestrial ecosystem to absorb CO2, and better reflects the temporal and spatial variation of natural carbon flux. Tibet plateau, as a sensitive area of global climate change, a threatened area and an amplifier of the global, where northern is the Qaidam Basin that is the main oasis development area of China, but at present, due to the increasingly severe desertification, extreme weather events occur frequently, the development of the plateau oasis has been threatened by a certain degree, which will affect the production and life of the residents in the oasis. In the past, the researchwere limited to the mineral, climate, NDVI and other aspects of the Qaidam Basin, however, how the gross primary productivity(GPP) of the vegetation in Qaidam Basin? what the spatial and temporal distribution of GPP and its influencing factors?These are scientific issue worthy of study. Therefore, this paper based on MODIS / GPP data, the use of RS / GIS method(spatial analysis, overlay analysis), trend line analysis, correlation analysis, etc., and the rate of change is divided into six grades of GPP in Qaidam Basin in 2001-2013, study the spatial and temporal characteristics, and to explore the relationship between the GPP with climate,topographic factor, vegetation, land use/cover change. In this paper, the main conclusions are as follows:(1) The GPP of annual, spring, summer and autumn were rising trend in fluctuationin Qaidam Basin from 2001 to 2013, and the trend of GPP was the most significant increase in the year, which the rate of change was53.25 g C/(m2 ? 10a)(P<0.01)?GPP growth takes place between April 7th and October 8th of each year,wherein the GPP maximum in July. The fastest growing period of vegetation GPP is roughly between June 26 th and August 20 th of each year.(2) In the last 13 years, there were obvious differences in the spatial distribution of GPP in Qaidam Basin, overall showed decreasing a trend from east to west, fromoasis to mountain area. Wherein the maximum value of annual GPP is 618.22 g C/(m2? 10a),And its high-value areas are mainly distributed in the eastern of Qilian Mountain and region inside basin oasis.(3) 2001-2013, the area of annual and seasonal GPP showed an increasing trend greater than its decreasing trend in Qaidam Basin, and theincreasing trendin summer is the largest especially, which area accounted for 99.39% of the total vegetation.(4) By analysed theinfluence factors,like altitude, slope, slope, climatic factors(temperature and precipitation), vegetation types andLUCC impacted on GPP in Qaidam Basin, we can come to:?Annual and seasonal GPP reached a maximum at the lowest altitude that is2685 m, their fluctuation were more significant when the altitude is between2685-3000 m, and at an altitude of 3000-3700 m, which were decreased with elevation,Whereas, when the altitude is higher than 3700 m, annual and seasonal GPP were decreased with elevation,, which is closely related to the vertical zonal distribution of vegetation; The increase of and GPP in 2900 m was the most significant in the annual and summer, but it in 2685 m was the most significant in spring and autumn respectively.The annual and seasonal GPP and its increasing trend were the maximum when the slope is 24 ° and 27 ° respectively, but when the slope is greater than 24 °,27 °, which increased with the slope increases. When the aspect is 157.5 °, 337.5 °,annual and seasonal GPP reached the maximum, minimum, and its tendency to increase the slope is more significan attheaspect is112.5 ° ~ 247.5 °.?The precipitation had a significant impact on the annual GPP in Qaidam Basin,and the positively relationship betweenGPP with itwere occupied by 73.86% of the total vegetation area.But the temperature had a strong correlation with the spring and summer GPP, the area with a positive correlation was 98.8% and 98.12% of the total vegetation.However,the GPP of autumn was negatively correlated with temperature and precipitation,and the negative correlation with precipitation is stronger than the temperature.?The lag effect of GPP with temperature and precipitation in spring and summer show that: the precipitation in winter had a strong influence on GPP in the after year in Qaidam Basin,and the spring precipitation contributed most to GPP in thesame year.?GPP of different vegetation types had significant difference, as follows:crop> open shrub> grassland> bare land or low vegetation coverage, These four vegetation GPP all showed the increasing trendin 2001—2010,among them, the increasing trend of open shrub was the most obvious.?The land use / cover change(LUCC) is closely related to the annual GPP,specific performance as:the increase of GPP value was closely related to the high turn in of the grassland and the low turn outin 2001-2002,thelow transfer and high turn out of arable land made the annual GPP reduced in 2002-2003,in 2003-2006, the relationship between the increase of GPP with the farmland and forest land which is high turn inand low turn out was very significant,thelow transfer and high turn out of arable land made the annual GPP reduced in 2006-2008,GPP turn increased with the arable land was high turn in, low turn out were inseparable in2008-2010. |
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