Vegetation Cover Change and Climate Response in Three Gorges Reservoir Area
|School||Huazhong Agricultural University|
|Keywords||Vegetation cover NDVI Climate Change Climate response Three Gorges Reservoir Area|
In this paper, the 1960-2009 temperature and precipitation data from 2000 to 2009 MODIS / NDVI data sets, using the linear trend method, R / S analysis, spatial interpolation method analysis on the regional level and grid level in the Three Gorges Reservoir AREA 50a climate change characteristics of the reservoir area for the past 10 years the vegetation cover change and climatic factors. The study revealed a vegetation variability and its climate response relationship in the Three Gorges Reservoir Area, and the vegetation of the study area and ecological and environmental protection and research has important practical significance and reference value. The main conclusions are as follows: (1) temperature interpolation based on the spherical model of the effect of kriging DEM (digital elevation) data is generally good, kriging, followed by the index model based on DEM data IDW (inverse distance) interpolation relative effects of the worst. Precipitation interpolation using consider the elevation of CK (co-kriging) interpolation the best, the worst effect of IDW interpolation. The results from the statistical point of view, IDW SPLNE (spline function), OK (ordinary kriging) and CK interpolation between different effects is not great, but the geostatistical method is significantly better than the conventional method. (2) the overall average annual temperature was significantly upward trend, linear heating rate of 0.13 ℃ / 10a, but lower than the national average; seasonal temperature changes, a weak cooling trend in summer 2006, and the other three quarters have increased temperature trends, autumn, winter warming trend is significant, the largest contribution to the average annual temperature. The spatial variation of temperature, the annual average temperature rendered the law of increasing from east to west, from south to north, the temperature change is no consistent trend in the eastern region increased gradually from south to north, average annual temperature change has a significant spatial differences. The spatial distribution of spring, summer, autumn, winter temperatures are west is generally higher than the eastern and central regions, Chongqing city is the center of a high-value, low value area in the eastern Pakistani Southeast. (3) The average annual precipitation overall downward trend, the average annual reduction 2.24mm; seasonal precipitation in addition to fall significantly reduce the spring downward trend was not significant, summer, winter precipitation increasing trend, but no significant decrease in annual precipitation mainly by Fall contributions. The spatial variation of precipitation, average annual precipitation presents the law of increasing from west to east, the highest precipitation in Padang and Zigui minimum value of Chongqing City, southern, and Jiangjin region. Annual precipitation trends exist a rise in the heart of the western region of Fuling, longevity, Yubei, most of the rest area for the downward trend. Seasonal precipitation: the contours of the eastern region from east to west, and are increasing from north to south, Pakistan southeast highest value Xingshan low value area. (4) climate transition, the annual average temperature jump occurred in 1996; spring, summer, autumn and winter seasons transition points followed 1996,1993,1997,1996 years, with an average annual temperature of seasonal temperature transitions than good synchronization. Year, quarter precipitation did not reach the mutation level, year, season precipitation in recent 50a is a random fluctuation phenomena. The sustainability of the trends of climate change, with R / S analysis shows that the overall warming trend of the past 50 years indicates that the temperature will continue to rise, and the annual average temperature in spring of this trend is quite strong; autumn and winter, with a moderate degree of continuity; summer temperature trend continued weak, is a random fluctuation. Annual average spring precipitation slowly decreased with moderate persistent, summer, winter precipitation for the steady growth trend of autumn rainfall significantly decreasing trend continued strong. That future temperature, precipitation has long-range correlation, that is, the overall trend is more consistent with the past, and this trend is strong. (5) vegetation overall change in annual average NDVI linear trend 0.02/10a. Spring, summer, autumn and winter NDVI linear trend were 0.045/10a, 0.01/10a, 0.02/10a, 0.002/10a. Rising trend of spring NDVI is the most obvious; relatively stable upward trend in the summer and autumn NDVI; summer, autumn NDVI in 2006 to achieve a minimum of 10 years, due to the sustained high temperatures in the summer of 2006 in the southwest region, the impact of dry weather 10; the winter NDVI overall trend minimal. The overall trend of growth since the 1990s, the reservoir area to implement a comprehensive returning farmland to forest and grasslands and natural forest protection project has achieved remarkable results. Similar NDVI overall change of the three types of woodland, farmland, shrub and grass, showed rising trends, linear trends were 0.02/10a, 0.03/10a, 0.02/10a, woodland, farmland, shrub and grass NDVI upward trend obvious, and other types of weak downward trend -0.001/10a. (6) spatial distribution of vegetation, for many years, the annual average NDVI presents a plaque inlaid interlaced ribbon graded, on the whole, the law of diminishing order from east to west. Years quarter average vegetation coverage overall law and for many years the average annual NDVI changes similar NDVI Four Seasons emerged from northeast to southwest diminishing space distribution law; Hubei section of the northeastern part of the four counties (Yiling, Xingshan, Zigui, Badong) NDVI values ??of the highest value, lowest NDVI values ??of the western city of Chongqing and the surrounding region; central region and the western region of the south bank of the Yangtze River is relatively north shore. Spatial trends, years of vegetation NDVI changes slope is positive pixels total 82.4% of the number of pixels, only 17.6% decline pixel. F test that does not exist in most of pixel vegetation cover significant changes in trends, only 5.07% as there has been a significant increase in a significant reduction accounted for 0.79% of pixels. This shows that 10 years, most of the area's vegetation cover changes in the case of random fluctuations, rather than the the vegetation landscape changes caused by human activities is now like. The increasing trend each season vegetation of the area is much larger than the decline in the area of ??each season to increase space, the Shapingba, Fuling all season showed varying degrees of degradation risk. (7) related to the overall vegetation NDVI and annual average air temperature, precipitation was positively correlated with annual precipitation related significant, was not significantly correlated with the average annual temperature. Annual precipitation is the impact of the Three Gorges Reservoir Area Vegetation Annual Dynamic Change of main meteorological factors. Seasonal scale climatic factors that affect the entire reservoir area of ??vegetation, the sensitivity of precipitation compared to temperature, which affect a large seasonal climatic factors mainly winter temperatures and precipitation, summer precipitation. Can be seen in summer and winter climatic conditions have a large impact on the region's annual average NDVI. From the relationship between the different vegetation types of NDVI annual meteorological factors, temperature, precipitation, and a variety of vegetation types NDVI are positively correlated, temperatures and all vegetation types NDVI positive correlation was not significant, but related; annual precipitation and farmland NDVI significant, indicating that the number of annual precipitation directly affect the growth of cultivated vegetation. Spring temperatures and precipitation of forest land is not significant; significant arable land and summer climate related summer temperatures too high is not conducive to the improvement of woodland NDVI of summer precipitation more obvious impact on cultivated land; spring, summer precipitation increases there is conducive to shrub and grass NDVI growth. (8) the spatial correlation, the average annual temperature, precipitation and NDVI are positively related to the area of ??positive correlation occupies an area of ??more than 60%. Temperature-related, northeast, south central and southwest performance most related significantly to about 0.7, a significant negative correlation between a relatively small area; related with precipitation in north-central Kaixian, Wuxi, Yunyang northern region related significant reach 0.8 left rear. Seasonal spatial variation, NDVI and air temperature, precipitation positively related to the area occupied mainly in spring, summer, winter precipitation for most regional NDVI have a positive impact on certain negative; summer temperatures too high for most of the regional vegetation impact; spring, autumn temperatures for most of the region have a positive impact.