| Vegetation, as an important part of earth’s surface, which is thefoundation for the existence of the ecological system. Vegetation cover change has animportant influence and effect to regional ecology, environment, climate, etc. Stemstream of Yangtze River in Yibin is belong to Yangtze River upstream, is also theimportant region of economic district in south of Sichuan. For the last20years, becauseof country’s increasing efforts on economic development along the Yangtze River, andthe Sichuan province put forth effort to the economic constructing district in south ofSichuan in the meantime, the economy of stem stream of Yangtze River is increaserapidly. But with the population increasing, the needs of relevant natural and landresources were also increasing, and result in contradiction extrude between of humanand land, and environmental quality was deteriorated, and thus human health wasthreatened. Vegetation had a lot of important effect, such as conservation of water andsoil, windbreak and sand-fixation, climate regulation, purified air, maintain ecologicaldiversity, etc, it is play an important role in the stem stream of Yangtze River in Yibin,including ecology, environment, landscape, tour, regional culture, hydrology, etc, andthe vegetation construction had been put on to the agenda as early as in the beginning ofthis century, therefore, analysis and evaluation on the regional vegetation cover changethat had a significance obviously to regional ecological environmental protection andharmonious coexistence between man and land.In this study, the stem stream of Yangtze River in Yibin, including Cuiping district,Nanxi district and Gao county were took as the study area, the remote sensing data ofLandsat TM/ETM+, DEM, slope, aspect and Google Earth, and the relevant data ofstatistics yearbook and vector, etc, were used as the data source, based on remotesensing and GIS technique, combined with landscape ecology and mathematical statistics knowledge, it is through data preprocessing firstly, which can restore ETM+images gaps and eliminate or reduce the images cloud effectively, than analyzing andevaluating the vegetation cover change in study area for2000-2010a, as well asanalyzing their relationships with nature and anthropogenic factors, finally this studygot the imitated estimated model of vegetation coverage by using ridge regressionanalysis, and predicted the vegetation coverage area proportion of study area in2020a.The results indicated that:(1)Annual average NDVI value was decreased in2000-2003a, and increasedgradually in2003-2010a, the whole trend was increased in2000-2010a; NDVI meanvalue was mainly change between in0.28～0.4, which mean that the distribution of thewhole vegetation cover in study area was preferable. In the NDVI mean valuedistribution, the value between in0.3～0.6was accounted for90.58%，and the value>0.6was only accounted for3.5%. Between of annual average NDVI value and annualNDVI maximum value were exist significant relationship, which mean that annualNDVI maximum value can also show vegetation change condition.(2)The NDVI change trend analysis showed that, the moderate improvementdistributed more widely, and the improvement and degradation of the whole vegetationcover were existed simultaneously for the past11years, but improvement area(including slight improvement, moderate improvement and significant improvementarea) was accounted for about71.52%, the degradation area (including slightdegradation, moderate degradation and significant degradation area) was accounted forabout17.2%, which explain that the vegetation cover of stem stream of Yangtze Riverin Yibin had been improved obviously.(3)The trend of high value vegetation cover area was increased obviously indifferent vegetation cover levels for2000-2010a. By supported of knowledgeclassification system, the binary NDVI images of2000,2005and2010a were used tosuperimposed classification and got the vegetation cover dynamic change map, whichshowed that the vegetation cover area of study area had been improved, and the wholevegetation cover area present an increasing trend for the past11a. By overlying ofdifferent NDVI levels images showed that, the largest area was medium to highvegetation cover growing region, followed by high vegetation cover growing region,which mean that the vegetation cover change was mainly for medium to high and highvegetation cover for2000-2010a. Moreover, this study got the feature map of vegetationcover dynamic growing change in study area for2000-2010a through overlying and coupling classification the vegetation cover dynamic change and vegetation growingmaps.(4)Although the trend of per capita different vegetation cover levels area wasconsistent with the corresponding each vegetation cover area change’s, the trend of percapita NDVI>0.35area was decreased. Vegetation cover levels comprehensive index ofstudy area between of0.58～0.86, which showed that the study area was not onlypreferable in the vegetation spatial distribution, but also was higher in the vegetationcover of the whole area. In the landscape pattern analysis, the largest patch area of highvalue vegetation cover region present an increasing trend, but the degree offragmentation in study area was enhanced; perimeter area fractal dimension of highvalue vegetation cover region may have reduced, which mean that the vegetationdistribution would be regularization; it is variant to the area variable coefficient of eachvegetation level region, but the high value vegetation region in2010a was largercompared to2000a, which mean that the uneven degree of distribution of its internalarea was larger; Shannon’s diversity index present a decreasing trend, which showedthat the land use of study area was intensive for the past11a.(5)The relative factors analysis showed that, NDVI mean value had a significantnegative correlation with MNDWI and earth’s surface brightness temperaturerespectively, but had a significant positive correlation with effective irrigation area andtown green area. Vegetation cover change was affected by terrain, land use change,government decision, population increase. Moreover, this study got the effectivesignificant linear relation model of NDVI mean value with annual average atmospherictemperature, earth’s surface brightness temperature mean value, population, town greenarea, effective irrigation area and town ship area, by ridge regression analysis.(6)Google Earth was used as the data source of vegetation coverage samples, andthe fitting imitated estimated model of vegetation coverage indicated that, it is not onlyhad a reliable accuracy, but also was relative objectivity for calculation of vegetationcoverage. Markov prediction model was applied to predict the area proportion ofdifferent vegetation coverage of study area in2020a, and the results indicated that thehigh vegetation coverage area will be over50%of study area.The vegetation cover had been change obviously in stem stream of Yangtze Riverin Yibin for2000-2010a, the whole vegetation cover present an increasing trend,specially high vegetation coverage area, but the improvement and degradation of thevegetation area were existed simultaneously, therefore, in order to maintain ecological environment balance and insure harmonious coexistence between man and nature, itshould be kept on enhancing and perfecting the ecological protective measures. |
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