关键词: 温度, 柴达木盆地, 植被变化, 可利用降水量

Abstract:

Global climate change has led to significant vegetation changes in recent decades. The Qaidam Basin, most of which was located in hyper-arid areas, is undergoing a process of prominent warming. It is necessary to investigate the response of vegetation to the climatic variations for a better understanding of the accumulated consequence of climate change. Vegetation NDVI is an important indicator for evaluating terrestrial eco-system change. Based on MODIS NDVI and climate data during the period 2001-2010, we analyzed spatial and temporal variation of vegetation change and its reasons for that by using methods of linear regression, partial correlation, the Hurst index and other methods. Results were shown as follows: 1) During 2001-2010, the growing season NDVI (NDVI) of the study area was improved progressively, with a linear tendency of 0.041/10 a. Trends in NDVI of shrubs, grasslands and shrub-deserts were +0.043/10 a, +0.034/10 a and +0.028/10 a respectively. The shrubs improved most significantly. 2) Vegetation restoration was characterized by two fast-growing periods, with an "S-shaped" increasing curve. 3) Vegetation restoration and degradation area accounted for about 12.43% and 0.35% of the whole study area. The restoration area was mainly distributed in high altitudes of the Burhan Budai Mt., Qimantag Mt., Ela Mt., Qaidam Mt. and Zongwulong Mt. surrounding areas of the Donggi Conga Lake and core areas of oasis. The degradation area was mainly distributed in margins of oasis, especially in the middle and lower reaches of the Qaidam and Leningrad rivers. 4) Vegetation NDVI was most positively related with average temperature (January to May) and available precipitation (May to August). The significant positive region between vegetation growth and temperature occupied about 8.36% of the vegetated lands and was mainly distributed in core areas of oasis and high latitude mountains. The significant positive region between vegetation growth and available precipitation made up about 30.95% of the vegetated lands and was mainly distributed in low latitude mountains and mountain valleys. Vegetation growth was more sensitive to hydrological conditions than to thermal conditions. 5) Vegetation growing season extension and growth acceleration were the main reasons for vegetation restoration in the Qaidam Basin. Warmer and wetter climate was the main driving force to promote vegetation growth in the Qaidam Basin. 6) The Hurst index of NDVI time series showed vegetation restoration was persistent. It is expected that promotion in vegetation growth will expand to the most parts of the region. This finding not only underlines the importance of temperature for vegetation growth in high latitudes, but also verifies the effects of precipitation on vegetation growth in low attitudes.

Key words: available precipitation, vegetation change, the Qaidam Basin, temperature