| Jiuwan Mountain National Nature Reserve located in Guangxi province China. Forest vegetation type is various and the forest structure is complicated in this area which is very infrequent in the same latitude region in China. It is one of the most species-rich areas in subtropical China and it is also the important parts of biodiversity conservation in the same latitude around the global. The research on forest carbon storage is the most important one in the global carbon cycle under the global warming trend. This research takes Jiuwan Mountain National Nature Reserve as the research object. The vegetation growth and change by the using of NDVI vegetation index extracted form Modis remote sensing information and the relationship between NDVI vegetation index and climatic factors based on the local meteorological datas during 2000 to 2013 in the study area has been analysed. On the basis of collecting previous datas and forest inventory datas, the biomass remote sensing estimation model was constructed, and the carbon storage of forest vegetation was estimated. Research shows:(1) Jiuwan mountain annual average NDVI value fluctuated during 2000 to 2013, but from the point of view of the overall trend did not change significantly, which showing a slight upward trend, the average annual mean NDVI above 0.543 and varied in the range of 0.543～0.599.The main terrain in north and south region of Jiuwan mountain is mountainous region and hilly area which forest vegetation coverage rate is very high and also the core area of conservation zone. NDVI value over the years held steady above 0.6 in south area, followed by the north, the lowest in the middle. Among the years, NDVI showed a downward trend form 2002 to 2004, showing an upward trend after 2004, and reaching an extreme value in 2008. Vegetation cover variation rate show that the rate of change was the highest in 2009, reaching-10.4%, the reason is that the data recorded there was a serious drought in the region in 2009, the vegetation growth is restricted and weak vegetation coverage area and sparse vegetation coverage area increased significantly. Overall, Jiuwan Mountain basically in a stable and health forest ecosystem, vegetation coverage showed a slight upward trend, maintained at a high vegetation cover and dense vegetation coverage levels in the whole area.(2) The average annual air temperature showed a trend of decline in Jiuwan Mountain National Nature Reserve in the past 14 years. The average annual temperature is fluctuating between 19.93 and 21.97; The average annual precipitation change is not obvious, showing a slight downward trend. From different seasons, the average temperature and precipitation of spring and summer in this area showed a decreasing trend, and the precipitation in autumn was significantly increased and the temperature dropped. The correlation between average annual precipitation and NDVI is more significantly than the correlation of the temperature and NDVI. The reason is that the region is a subtropical climate, the average temperature of the growing season is basically maintained at 20 degrees Celsius and above, it is conducive to the growth of vegetation, so the average annual precipitation is more able to reflect the overall trend of vegetation growth.NDVI seasonal variation showed four distinctive seasons in the region, the vegetation coverage of spring was significantly affected by temperature changes. The reason is that spring is the germination period of vegetation, so the temperature is a major factor in regulating the growth of vegetation. The vegetation growth was mainly affected by the temperature of the month in April, March; Summer and autumn precipitation effect on the growth of vegetation in Jiuwan mountain areas is the most significant. The vegetation showed a certain lag behind the change of air temperature in summer, but not significant. From June to November, the vegetation growth in this area is mainly affected by the precipitation of the month, the lag of temperature and precipitation to vegetation growth in the region is not obvious. NDVI monthly average temperature and NDVI vegetation index showed a significant positive correlation. The region NDVI reached the highest value when the temperature between 30-27 degrees Celsius. Average monthly precipitation and NDVI significantly related to general, the correlation was general between mean monthly precipitation and NDVI, when the monthly rainfall in the following 50mm, the NDVI are basically maintained at a minimum level. Within the range of precipitation from 50 mm to 150 mm, the monthly average NDVI index fluctuated greatly, NDVI shows no obvious growth trend when the precipitation more than 2000 mm, the monthly average minimum NDVI remained at 0.7.(3) In 2009, for example, the forest biomass is 1908 396 tons, the total carbon storage is 936262.3 tons in the area of Jiuwan mountain National Nature Reserve. The main forest type is arbor forest, the proportion of arbor forest is 22 725.5 hm2, accounted for 98.3% of the whole forest area, the stem volume of arbor forest is 2573 839 m3, accounted for 99.98% of the stem volume in the area. The forest carbon sequestration function between different forest types was quite different, but the stem volume, carbon storage and forest area has a positive correlation. The stand biomass and carbon storage were from high to low:Broad leaved tree, Chinese fir, Bamboo forest, Masson pine, Shrubs, Economic trees. Middle-aged forest and near-mature forest accounted of 84.15% for the total forest area in Jiuwan Mountain, which has great carbon sequestration capacity. Since 2000 the average carbon storage in the area has increased by 14.47 t per hectare. The average carbon density of arbor in this area was 40.875 tC/hm2, it was much higher than the China average carbon density (23.41 tC/hm2). By using the established biomass estimation equation, the average biomass estimated value fluctuating in a reasonable range in the unit area, which has certain reference significance. Therefore, remote sensing technology can be used to understand the distribution of vegetation carbon storage, and it is a positive correlation between vegetation NDVI index, biomass and carbon storage. This study deeply reveals the level of forest vegetation coverage degree, growth regularity and distribution of carbon storage in the protection area, provides a scientific basis to establish the plan of forest development and environmental policy of Jiuwan Mountain National Nature Reserve. |
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