| Global warming has become the undisputed facts, while since the last century, climate change is becoming the focus of governments, scientists and public concern, and focusing on the science of climate change has become one of the topics the active participation of domestic and foreign scholars. Climate change on Earth’s ecosystems change is enormous, and vegetation as the most sensitive ecosystems and the most vulnerable part responded to climate change mechanism, which attracted a lot of research scholars’attention. West Kunlun Mountains located in China’s westernmost region, northwestern Qinghai-Tibet Plateau, which is a typical alpine arid area, ecologically fragile vegetation by high climate impact. There is less vegetation growth conditions on the western Kunlun Mountains region under climate change research. So pending further study is that West Kunlun Mountains how to change in vegetation region in recent years, and vegetation growth how to respond to climate change. Meanwhile vegetation changes in West Kunlun Mountains and the surrounding areas whether they are differences, and so on.In this paper, data are TERRA satellite MODIS-NDVI data, which combined with the region’s digital elevation model DEM, vegetation type and temperature and precipitation data. Based on a linear regression, correlation analysis Theory, we researched 2000-2013, a total of 14 years, that the overall vegetation time and space in the growing season NDVI maximum and average distribution and trends of different vegetation types and its relationship with climatic factors (temperature and precipitation), topographic features (altitude, slope aspect, slope) in West Kunlun Mountains. Then we explored that the relationship between changes in vegetation and terrain factors and their response to climate change under the currently background of climate change in West Kunlun Mountains area. It is help to ecological protection and vegetation in Tibet alpine area which provides a reference value and reference recovery. The following is the content and conclusions:Using software ENVI and ArcGIS Spatial Analyst, we calculate the spatial and temporal distribution and 2000-2013 annual maximum NDVI trends in West Kunlun Mountains. The results showed that:Overall, the vegetation of West Kunlun Mountains in the past 14 years is stable, and NDVI values are slightly on the rise, but not significantly. NDVI showed the variation characteristic that "up-down-up again", since 2003 NDVI started to decrease, until to 2009 it dropped to the lowest value. And then gradually increased, reaching a peak in 2012. From the Maximum NDVI’s spatial variation trends,2000--2013 the vegetation showed overall stable trend in West Kunlun Mountains. The stable area of vegetation is the largest in the entire region which occupies the vegetation area of 83.24 percent, and it is widely distributed in the West Kunlun Mountains inside. Secondly by vegetation improvement district occupies 14.7 percent of the total area. It distributes mainly in the West Kunlun Mountains on the north side of the mountain area near the Tarim Basin, western West Kunlun Mountain Taxkorgan Valley and southern West Kunlun Mountain Yurunkax and Karakax River plateau, where these regions had relatively good vegetation status. The vegetation degraded area is the smallest, only 2% of the total area of vegetation, and it is distributes scattered debris.Based on meteorological grid data, we analyzed 2000-2013 the changes of temperature and precipitation in growing season of West Kunlun Mountains. The results showed that:in 14 years, the change of temperature in growing season is mainly fluctuation, and there is a relatively high temperature and low temperature years, but overall there was no significant variation. The changes of precipitation in growing season also showed characteristic fluctuations, and there is weak growth trend, but not significant, large fluctuations between years.NDVI combined with meteorological data, using correlation analysis to analyze the relationship between overall vegetation NDVI annual maximum and air temperature and rainfall in growing season in West Kunlun Mountains. Then we analyze correlation between climatic factors of each month and NDVI maximum. The results show that:the NDVI maximum and average temperature in growing season showed no significant negative correlation with temperature in May by the negative correlation significant test. Vegetation NDVI maximum and growing season precipitation showed no significant positive correlation. Precipitation of each month had different influence to NDVI, and precipitation and vegetation NDVI 7 month maximum had a significant negative correlation, but in other months showed no significant positive correlation.With the Tibetan Plateau vegetation classification data, the type of vegetation in West Kunlun Mountains were reclassified into the desert, alpine meadows, alpine steppe, and non-vegetation area four types. In three vegetation types, the largest was desert area, accounting for 52.26% of the total area, and alpine steppe followed by the total area of 11.9%, and only 2.95% of the total area was alpine meadow. Three kinds of vegetation types of annual maximum NDVI’s interannual variation showed no significant increase in the trend, showing "up-down-up" features. In the study period, the alpine steppe is relatively stable vegetation type, and followed is alpine meadows by changes, and the largest change is desert. Three vegetation types of changes in the spatial distribution of the main area are stable, secondly improving the area, and the smallest proportion of degraded areas. Desert vegetation area ratio of the stable region is the smallest, with highest degradation ratio, reflecting the desert vegetation vulnerability of West Kunlun Mountains.Alpine steppe, alpine meadow and desert NDVI and temperature in growing season exhibit no significant negative correlation, and between precipitation growing season and NDVI have no significant positive correlation. Three vegetation types in response to climate factors each month does not exist difference. Three vegetation types exhibited a negative correlation significantly with the May temperature, due to the low spring precipitation in West Kunlun, while during this period continued warming will accelerate the evaporation of soil moisture leading to droughts, so it affects the growth of vegetation. In terms of precipitation three vegetation types exhibit that precipitation in July has a significant negative correlation, and most of the other months do not have significant positive correlation.West Kunlun ridge line along the study area was divided into two regions, the southern slope and the northern slope, comparative analysis of the 2000-2013 north-south differences in slope vegetation growth conditions, and climate conditions. We discussed two regional vegetation responses to climate change, and the southern slope of precipitation slightly higher than the northern slope, with temperature much below the northern slope. Due to differences in climate background, the southern slope and the northern slope of vegetation showed significant differences. The northern slope of vegetation was better and alpine meadows, alpine grassland distributed larger area, but NDVI have no significant upward trend. The southern slope of vegetation was in poor condition, mainly desert vegetation types, and its growth trends of NDVI had by testing, but the growth rate is very small. This difference of north-south slope vegetation in West Kunlun reflects that vegetation in plateau ecosystems adapt the climatic conditions by adjusting the structure and function.Combined with vegetation trends and research area DEM data, we discussed the distribution of vegetation change in elevation, slope, sloping upward.2400m altitude region below, a large proportion of improving the area, in addition to other altitudes, area stability zone is greater than improvement area, larger than the degraded area, 2800m above, three trends area ratio remained stable.Most vegetation of the West Kunlun Mountains is growing in areas less than slope 30 °, and improvement vegetation district is mainly concentrated in regions less than slope 10 °. Degraded vegetation mainly distribute in areas where the slope of less than 20 °. Improvement vegetation district distribute in the mountains from the eastern slope to the northern slope (NE-ESE) in West Kunlun Mountains, and degraded vegetation distribute from the western slope of the mountain’s to southern slope (W～SSW). This may be due to the shady slope by less solar radiation, and soil moisture is easier to save, thereby facilitating improved vegetation. |
PDF Full Text Request