Abstract
The Qinghai-Tibetan Plateau has been experiencing a distinct warming trend, and climate warming has a direct and quick impact on the alpine grassland ecosystem. We detected the greenness trend of the grasslands in the plateau using Moderate Resolution Imaging Spectroradiometer data from 2000 to 2009. Weather station data were used to explore the climatic drivers for vegetation greenness variations. The results demonstrated that the region-wide averaged normalized difference vegetation index (NDVI) increased at a rate of 0.036 yr −1 . Approximately 20% of the vegetation areas, which were primarily located in the northeastern plateau, exhibited significant NDVI increase trend (p -value <0.05 ). Only 4% of the vegetated area showed significant decrease trends, which were mostly in the central and southwestern plateau. A strong positive relationship between NDVI and precipitation, especially in the northeastern plateau, suggested that precipitation was a favorable factor for the grassland NDVI. Negative correlations between NDVI and temperature, especially in the southern plateau, indicated that higher temperature adversely affected the grassland growth. Although a warming climate was expected to be beneficial to the vegetation growth in cold regions, the grasslands in the central and southwestern plateau showed a decrease in trends influenced by increased temperature coupled with decreased precipitation.
Highlights
The Qinghai-Tibetan Plateau is regarded as a typical area for investigating the relationships between vegetation condition and climate variables, because the vegetation remains relatively undisturbed by human activities due to the low population and the plateau is dominated by alpine grasslands that appear to be highly sensitive to global climate change
By averaging the climate data of all the 46 weather stations in the Qinghai-Tibetan Plateau [Fig. 2(a)], we found that the annual mean temperature showed a significant increase trend from 2000 to 2009 (p-value
The partial correlation analysis at the weather stations with significant normalized difference vegetation index (NDVI) trends indicated that the NDVI was strongly related to temperature and precipitation at most sites
Summary
The warming climate in recent decades has promoted vegetation growth in the northern hemisphere,[1,2,3,4,5,6,7,8] such as Alaska,[9,10] Canada,[11,12,13] and Russia.[14,15] Global warming has caused an increase in precipitation that resulted in vegetation greening in the southern hemisphere, such as African Sahel[16,17,18,19,20,21] and South America,[22] some areas with a decrease in precipitation markedly reduced vegetation production.[23,24] The Qinghai-Tibetan Plateau is regarded as a typical area for investigating the relationships between vegetation condition and climate variables, because the vegetation remains relatively undisturbed by human activities due to the low population and the plateau is dominated by alpine grasslands that appear to be highly sensitive to global climate change. With the last decade counted, the annual mean temperature increased by 1.8°C from 1960 to 2007 with an increase rate of 0.036°C · yr−1 (Ref. 28), which doubles the rate of the second half of Journal of Applied Remote Sensing
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