| With the continuous development of human society, the relationship between human and ecological environment is becoming more and more closely, human impact on the nature of the ecological environment, and at the same time by the nature of feedback. With the warming of the climate, the ecological environment conditions have changed a lot, directly or indirectly affect the production and life of human beings.The bashang area is an important farming pastoral zone in China, the ecological environment is fragile, so this paper takes the dam area as an example, studies the change characteristics of NDVI and analyzes its influencing factors. Results show:(1) The vegetation NDVI in the research area of 2000-2013 is on the rising trend,increasing the amplitude of 0.03/10 a, which indicates that the vegetation coverage in the study area is gradually improved. In 2013, NDVI was 0.5631, reaching the peak value of 12 a. Influenced by precipitation, NDVI was low in 2009. From the point of view of the spatial change and the trend of the study area exists spatial difference, P <0.01 confidence level 16.93% of grid was significantly increased trend, the regional area of only 158km2 is significantly decreased. Description 14 a to study the growth trend of vegetation in the study area, there are only a very small number of local areas are also degraded.(2) Although the change trends of NDVI were different in the 2000-2013 years,the trend was consistent with the inter annual variation. The change range of NDVI in each season was 0.01/10 a, 0.04/10 a, 0.04/10 a, and NDVI in summer and autumn,which was the most obvious in summer and autumn. Spring, summer, autumn three season NDVI showed a significant increase in the area of 15456km2, while the spring area of only 3130km2 showed a significant increase trend. In all seasons, NDVI showed significant reduction of the regional area, which were 386km2, 30km2, and255km2, respectively.(3) In case study area forest, shrub and grassland, meadow, agricultural vegetation fifth vegetation types annual NDVI were presented increasing trend, the rate ofincrease of 0.02 / 10 a, 0.03/ 10 a, 0.04/10 a, 0.04/10 a. The average annual NDVI of various vegetation types are forest, shrub, meadow, agricultural vegetation and grassland. The vegetation types in summer and autumn in the two seasons of2000-2013 years showed an increasing trend. In spring, summer and autumn, all vegetation types are NDVI in the order of increasing the size order of shrub, meadow =agricultural vegetation > forest > grassland.(4) Using the DEM data from the study area, elevation, slope and aspect of the detailed analysis of the three aspects of topographic factors on vegetation cover change.Gao Cheng factor, altitude 0-500 m, vegetation coverage, with the elevation of elevation, vegetation improved faster, with the elevation of NDVI to improve speed began to slow down. Slope factor, in the range of 0 degrees-10 degrees NDVI degrees,the slope of the slope of the slope increased with the increase of slope, that is, the rate of increase of vegetation cover with the increase of slope; In the range of 8 degree-15 degree, the increase of vegetation coverage rate is relatively stable, that is, the trend of vegetation coverage is steadily rising; At 15 degrees-30 degrees, the vegetation cover increases the situation becomes slow, when the acting to the slope to reach 30 degrees,the NDVI changes the slope value is the lowest, 0.0013. To improve the speed of vegetation in slope, slope than sunny slope, vegetation growth status is more active than sunny.(5) The correlation coefficient of annual average NDVI and annual precipitation is larger, the average annual NDVI will increase with the increase of precipitation, and the correlation with the temperature is smaller than that of precipitation. Spring,summer, autumn three season NDVI and with the same temperature rise and fall, but will increase with the increase of precipitation, which spring NDVI and precipitation during the same period, which summer NDVI and precipitation during the same period reached(P < 0.05). From the perspective of spatial distribution, the proportion of NDVI and precipitation in the study area was positively related to the proportion of negative correlation, and negatively correlated. In the study area, the NDVI and climate of the 1-2 in September and the climate in the study area are lagging behind.(6) Different vegetation types in the spring, summer, autumn and the change of NDVI in the three quarter is more obvious. In addition to forests and shrubs, grassland,meadow, agricultural vegetation season average NDVI and annual precipitation,growth Ji Jiangshui and summer precipitation are all positive correlation, and the correlation is through the P<0.05 confidence test. In the three seasons of spring,summer and autumn, the forest and shrub had a weak positive correlation with the precipitation in the summer and autumn. The correlation coefficient between the meadow and the spring average temperature was the biggest, but the correlation was not significant.(7) The response of NDVI to temperature and precipitation changes in the study area was delayed. In June and May, NDVI was significantly correlated with the precipitation, and negatively correlated with precipitation, total precipitation of NDVI in August from the previous month to achieve significant positive correlation is not significant negative correlation with the first two months of the temperature.September NDVI and the first two months of precipitation have a strong positive correlation.(8) Research area vegetation cover and precipitation were positively correlated with the ratio of greater than was negatively related to the proportion, temperature and negative correlation is greater than the proportion is scale dependent, indicating that in most of the range of the study area precipitation increasing is beneficial to the growth of vegetation and temperature rise on vegetation growth of certain inhibition. And precipitation was significant positively correlated to the proportion of 54.4%, and the homochronous temperature was significantly negatively correlated with the area accounted for 90.54% of the total area of the study area are mainly distributed in Fengning, paddock, Duolun County in most parts of the country, as well as Shangyi,Guyuan County in the southern region.(9) The NDVI of spring, summer and autumn in the study area was positively related to the seasonal precipitation, but the area is relatively small, and theprecipitation in most areas of the study area was the dominant factor of NDVI growth.The negative correlation between NDVI and air temperature in summer and the positive correlation with precipitation were more than that in spring and autumn. |
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