A Research About The Response Of The Vegetation To The Climate Change In The Shiyang River Basin In 1999-2006

Under the background of the global warming, the climate in the Qilian Mountain has changed a lot. In order to study the characteristic of the climate change in the Qilian Mountain, this article selects Shiyang River basin which in the east of the Qilian Mountain to study the response of the vegetation change to the climatic change. The vegetation change in one year and its seasonal variation is very obvious, through monitoring the vegetation change; the climatic change can be reflected clearly, under the support of the software ArcGIS, together with the mature remote sensing technique, using the remote sensing succession data to study the vegetation change is becoming more and more preponderant. The paper mainly includes three aspects of content:First, based on the NDVI succession data of 10 day synthesis SPOT VEGETATION NDVI to analyse the change rule of the NDVI, and the correlativity which between the NDVI and the temperature as well as the precipitation in 1999-2006.Second, using the temperature and precipitation data of the 8 years from the 18 weather stations in the Hexi and 3 automatic weather stations and 7 conventional weather stations in the research area, and utilizing multianalysis method, we finally obtain the temperature and precipitation model in each summer, then make it become the grid data basing on the method of GIS, together with the homochronous NDVI grid data, we use the partial correlation coefficient formula to compute their coefficient in the Raster Calculator of Arc Map, using the coefficient of each grid we get the correlation coefficient distribution map, thus we can research the space correlation between the NDVI and the temperature as well as the precipitation.Third, on the help of the soft ENVI, MATLAB, TIMESAT, distilling the vegetation phenology of the 8 years, then we can research the response of which to the climatic change.Through the research of three aspects above, the preliminary results are as follows: First, after analyzing the NDVI change rule of the kinds of typical natural vegetation forest and lawn in the 8 years, we discovered that the NDVI of the forest and lawn were all showing the incremental tendency, the linear increment rate of the lawn was bigger than that of the forest, which explained that the meliorating status of the lawn was better than the forest. The NDVI peak value variation of the vegetation in the years may reflect the characteristic of the change of the vegetation growing-power. In 8 years, the NDVI peak value of the lawn was obviously higher than that of the forest, the peak value of the two types were increasing year by year, which explained that the energy of the two types were increasing year by year. The NDVI amplitude variation can also reflect the energy change of the vegetation, of which change was consistent with the peak value change. For 8 years, the amplitude variation of the forest and lawn were still in stable growth, which explained that the vegetation was developing to the good direction year by year.Second, after analysing the partial correlation coefficient of the NDVI of the two type with the homochronous temperature and precipitation, we discovered that the relation between the NDVI of the two type and the homochronous temperature belongs to moderate related, and the relativity of the lawn was bigger than the forest. The temperature in spring was the most important factor which affected the vegetation NDVI change in spring in the Shiyang River basin, but the linear rate of the forest and lawn was not the highest, this probably because the temperature in spring in the high altitude was lower than that of the same latitude but low altitude. In summer, the relation between the NDVI of the two types and the homochronous temperature performed as minus correlation, which illuminated the temperature in summer in the Shiyang River basin restrained the vegetation growth. The autumn temperature only had the high relativity with the forest, had not obvious relativity with the lawn, which explained that the autumn temperature elevation would accelerate the growth of the forest, which also possibly delayed the forest enter the wither time. The correlation of the winter temperature and homochronous NDVI is generally not obvious. In this season, the forest NDVI and homochronous temperature presented plus correlation, but the lawn presented the minus, which was not remarkable in our basin. The relation between the NDVI of the two types and the homochronous precipitation performed as lowness, only the forest and the summer precipitation had the good relativity, which illuminated that in the Shiyang River basin, the precipitation influence to the vegetation was smaller than the temperature, the temperature was the main force to the vegetation activity.Third, after analyzing the hysteresis between the two type with the temperature and precipitation, we had got the idea that to the climate the NDVI of the two type of vegetation were both have the hysteresis, the partial correlation between the NDVI of the forest and the temperature that one mouth advance was the highest, namely the influence that one mouth advance to the NDVI of the forest was bigger than that of the homochronous temperature; But regarding to the lawn, the homochronous temperature and the temperature that one mouth advance were not in difference, the partial correlation coefficient were both very high. Therefore, compared to the lawn, the NDVI of the forest to the temperature had obviously bigger hysteresis. But the two type of the vegetation had no hysteresis to the precipitation at all.Fourth, after analyzing the correlational space distribution map of the summer NDVI to the homochronous temperature and precipitation, we educed that the coefficient in the south Qilian was high, and the correlation between the NDVI and the temperature was minus, there was no relativity in the area of the middle part of corridor and the north low hill. After the statistics, the number of the grid which its value bigger or equal to 0.3 accounted for 2.07%, nearly completely distributed in the area of the south the Qilian, where was the area of the conifer and the partial meadow located.After splicing the correlational space distribution map to the vegetation type map, and then computing the number of the grid which its value bigger or equal to 0.3 by the tool of Zonal in the ArcGIS, we discovered that there had 492 forest grid and 334 lawn grid, accounted for 58.9%and 41.1%separately, proved that the response of the forest to the summer temperature was more sensitive than the lawn again. Similarly, the area of the high correlation coefficient of the summer summer NDVI to the homochronous precipitation was also distributed in the south Qilian, and the coefficient was plus, there nearly had no relativity in the middle part of corridor and the north low hill. After the statistics we discovered that the number of the grid which its value bigger or equal to 0.3 was only 10, accounted for 0.024%of the total, proved again that in this area, summer precipitation was not the control factor to the summer NDVI change, just the temperature was.Fifth, after distilling and analyzing the phenology information of the two type vegetation, such as the beginning time of the growth season, the ending time of the growth season, and the length of the growth season in the area, we discovered that the beginning time of the lawn was later than the forest, in the 8 years, the beginning time of the growth season of both the forest and the lawn had the tendency. of advance. The ending time of the growth season of the forest was later than the lawn; the forest had the postponing tendency, but the change of the lawn was not obvious. The length of the growth season of the two type vegetation were in steady rise in the 8 years, length's extension was the response to the climate change, was the strong evidence to the global warming, which was consistent with the other scholar's research conclusion.