Impact Of Climate Change On Vegetation In The Northern Slopes Of The Eastern KUNLUN Mountains And Their Downstream Oases In The Recent Ten Years

Under the background of the global warming, many natural systems are being affected by climate change.Vegetation is the most sensitive component to climate change in terrestrial ecosystems, and thus to understand the impact of climate change on vegetation mechanism has become one of the hot scientific community. The Northern Slopes of the Eastern KUNLUN Mountains and their downstream Oases is a typical ecological fragile high-altitude arid area, which located in the northern Tibet. The response of vegetation to the climate change becomes more sensitive and the vegetation is more vulnerable to climate change and human activities. This thesis analyzed the MODIS images and monthly meteorological records, after that, based on the results, we did preliminary research on the vegetation performance and changing trend of different land cover types, and analyzed the relationship between vegetation and climate. At last, some analyses on the spatial differences of the impact of climate change on vegetation and the relationship between vegetation and terrain factors were discussed in depth. This thesis contains six main contents as follows:1. this paper carried out a land cover classification of the Northern Slopes of the Eastern KUNLUN Mountains and their downstream Oases with the support of MOD09 surface reflectance data in growth season from 2000 to 2009, based on the classification results, we analyzed the dynamic changes of land cover. The results indicated that the whole study areas is showing a tendency to improve, and improve areas to degraded areas ratio of 2:1 in mountains areas and improve areas to degraded areas ratio of 3:1 in oases areas.2. We analyzed the inter-annual changes of average growing season NDVI and annual maximum NDVI of different vegetation types in the Northern Slopes of the Eastern KUNLUN Mountains and their downstream Oases using MOD13A1 data from 2000 to 2009. The results showed in mountain stable region, statistically significant growth trend in the alpine desert steppe, and no significant growth trend in the alpine meadow vegetation. The average growing season NDVI in the alpine desert meadow with no significant growth trend, while the annual maximum NDVI showed a significant growth trend. There is no significant growth trend in oases stable region.3. With annual average temperature anomalies, growing season average temperature anomalies, annual precipitation anomalies and growing season precipitation anomalies we analyzed the annual and growing season temperature and precipitation changes of different land cover types in the Eastern KUNLUN Mountains and their downstream Oases using MOD13A1 data from 2000 to 2009. The results showed that the annual and growing season precipitation were reflected in different degrees of increase, while the annual and growing season average temperature with no significant change in trend from 2000 to 2009.4. We analyzed the relationship between the vegetation activity in different land cover types and the average temperature, precipitation in the Eastern KUNLUN Mountains and their downstream Oases using MOD13A1 data from 2000 to 2009. The results indicated that the inter-annual changes of average growing season NDVI and annual maximum NDVI of the alpine desert steppe and alpine meadow vegetation were mainly controlled by the same period precipitation and the average temperature in early, while the alpine desert meadow vegetation significantly associated with the average temperature over the same period. The precipitation has some lag effect in the oases region.5. Through regional comparison, we analyzed the spatial differences of the impact of climate change in vegetation. The results showed that the temperature was slightly lower and precipitation increased significantly in the eastern mountains, while the vegetation change showed a better trend. In the western mountains, the temperature rose significantly and the precipitation increased weakly, while the vegetation showed a deterioration trend. Comparising of east and west from the mountains, we found that the positive effect of warming on the vegetation in the western part of East KUNLUN moutains may be reduced or disappeared, while the cooling and increased precipitation may be the main reason for vegetation cover significant improvement in the eastern section of East KUNLUN moutains. In the oases region, temperature increased rapidly and precipitation increased weakly, while the vegetation showed improvement trend. That is, oases vegetation growth may be impacted by the mountain precipitation and glacial melt water.6. Based on the Digital elevation model we analyzed the relation between the land cover change types and topography factors in the mountain region, the results showed that the change rates of area of desert to alpine desert steppe type increased with increasing altitude,and relatively strong at an altitude of 3900～4500m, mountains' southern slope. The change rates of area of alpine desert steppe to alpine meadow type increased with increasing altitude, and decreased slowly with the slope gradient, relatively strong at mountains'northern and western slope. The change rates of area of cold alpine meadow to alpine meadow type decreased with increasing altitude and the slope gradient, relatively strong at mountains'northern and eastern slope. The change rates of area of alpine meadow to alpine desert steppe type decreased with increasing altitude, and increased with the slope gradient, relatively strong at mountains' northern and western slope. The change rates of area of alpine meadow to cold alpine meadow type increased with increasing altitude and the slope gradient and then fluctuated around 15%, relatively strong at mountains'eastern slope.