| People have given great attention to the vegetation and its changes all the time,because the vegetation plays an important role in the earth system,and it affects the coordination and balance between the earth and the atmosphere system.It is able to perceive and express ideal basis for environmental changes.Remote sensing technology is a powerful tool for studying vegetation changes in a wide range.It is possible to study the regional and global vegetation distribution patterns and characteristics under the influence of human factors and natural factors.Combination of vegetation index from remote sensing image band,effective expression characteristics of surface vegetation cover has been frequently used in vegetation distribution,land cover,drought assessment and other regional or global aspects.In a variety of surface features of parametric representation,normalized difference vegetation index(NDVI)on the growth of vegetation perception is very sharp.At the same time,changes of the vegetation and lushness of vegetation cover degree can be truly reflected by the generation and usage of NDVI data.Since the beginning of the twenty-first Century,the process of socialist construction has been accelerated,and the goal of a comprehensive well-off society to further clarification is also clear.When compared with the previous difference,certain changes in a small range of the climate in Shandong Province has occured,which leads to the distributive characteristics of vegetation there,so the impact is eroding the natural environment and social economy condition of the study area step by step.This study deeply analyzed the temporal and spatial variation of the vegetation coverage in Shandong Province by using medium resolution imaging spectrometer after treatment(Moderate-resolution Imaging Spectroradiometer,MODIS)data which was after 2000.It aims to promote to maintain further ecological environment in Shandong province and realize the sustainable development of limited energy.It can helps to make environmental management regulations and laws more scientificly.Meanwhile,it is good to provide basis and methods for city construction.This paper selects Shandong Province as the main research area,and selected the image of MODIS L1 B and MOD13 Q1 from 2000 to 2015,which of the two resolution ratio was 250 V meters.It chose Maximum Value Composite to calculate NDVI of every period of ten days andeach month in 2015.It eliminated the individual value and non vegetation area from the data from2000 to 2015 after the classification.With the average value method,it generated monthly time-series data of NDVI year by year.This paper used the observation data of 44 meteorological observatories in Shandong province from 2000 to 2015 and put it in order.Then,the measured data was combined with the yearly and monthly NDVI time series data generation and combined remote sensing data and meteorological data.A more detailed analysis was made which was of the relationship between the variation of vegetation coverage during the last 16 years the period and temperature and precipitation of two factors.The main results are as follows:(1)The vegetation coverage of 2015 in Shandong Province is that the maximum to ten days as units of normalized difference vegetation index is 0.73,which appears in mid August.The minimum value is 0.23,which is in late December.The change of the curve has two peaks,which is consistent with the farming law of Shandong Province.As is known to all,Shandong is an important farming area in China.The crop maturity is usually two times each year or three times eachtwo years,and most of the cultivated land is alternately sown with two crops,such as winter wheat and summer corn.(2)The analysis of average monthly change trend of NDVI from 2000 to 2015 in Shandong province is that there is little difference between January and February,and the largest area of green vegetation grade is less vegetation(0.15<NDVI<0.3).The green vegetation level was significantly increased in March and April in the southwest and northwest of Shandong,and the coverage area has a clear increase trend.There are three types of green vegetation grade whose area has been increased in May and June,which are moderate vegetation(0.3<NDVI<0.45),thick vegetation(0.45<NDVI<0.6)and bushy vegetation(NDVI>0.6).The average monthly NDVI is the largest in July and August,and 80% of the total area with green vegetation classification is bushy vegetation.Most of the green vegetation classification has changed to moderate vegetation in September and October,and the average monthly NDVI has decreased in southwest,northwest and central area,which has the most obvious changes.The changes of monthly variation of NDVI is the largest in central,southern and eastern area of Shandong in November and December.At this time,the largest vegetation area was sparse vegetation.(3)The green vegetation area has decreased during the annual growth season from 2000 to 2015,and there was an obvious negative correlation between the area and the built-up area(R2=0.5452>0.5,P<0.01).After the year of 2000,the rapid development of urban construction has changed greatly in Shandong.The built-up urban areas and trade complexes are also increasing rapidly.In 2000,the built area of Shandong Province was 1500km2.Up to 2015,the built-up area of whole Shandong has increased to 4500km2,compared to 2000 which increased by two times.So the rapid development of urbanization is an important reason which led to the reduction of the green vegetation area.(4)The average monthly NDVI and monthly mean temperature showed a significant positive correlation from 2000 to 2015,and R2 is 0.8322,which shows that the temperature is an important factor to control the changes of vegetation coverage on the scale of a month in Shandong province.The average monthly NDVI has some correlation with the precipitation,and R2 is0.5705.There are 34 sites passing by 95% confidence test.Correlation between monthly NDVI and precipitation lagged for one month is relatively high,and R2 is 0.6995.There are 41 sites passing by95% confidence test.The correlation was obviously higher than the correlation between monthly NDVI and monthly precipitation.Correlation between monthly NDVI and precipitation lagged for two months is weak and R2 is0.3518.There 24 sites passing by 95% the confidence test.The correlation is lower than the correlation between monthly NDVI and monthly precipitation.After complex analysis,we get the results as follows:There are obvious correlation between the average NDVI of 16 years and precipitation precipitation lagged for one month.(5)During the 16 years,the average NDVI growth season has increased of Shandong Province.The vegetation coverage is improved.However,with the increase of the province built area,green vegetation area decreased significantly.This paper has positive significance for understanding the spatial pattern characteristics of vegetation cover changes in Shandong Province and evaluating the influence of temperature and precipitation on vegetation cover in climate factors. |
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