| As the human industrialization and global climate change caused by excessive emissions of CO2 and other gases have threatened the human existence and development. The forecasting of climate change requires accurate estimation of carbon uptake's amounts and changes in terrestrial ecosystems. Forests are the main part of terrestrial ecosystems and forest ecosystems play an important role in the global carbon cycle. Carbon storage in forest ecosystems is not only the important index reflecting the basic characteristics of forest ecosystems, but also the theoretical basis of the evaluation of the production potential of forest ecosystems and forest structure and function. As a result of a vast terroritory, diverse vegetation types and the complexity of forest ecosystems in China, regional estimates of biomass and carbon storage is a difficulty. According to the region's natural environment, it is extremely important to select the appropriate research methods and get the statistics of the carbon storage and density of different forest types and in different regions so as to estimate the national or global carbon sink of forest ecosystem. It is of practical significance to find the biomass estimation method being compatible to Forest Resource Inventory and use forest resource survey data for regional estimates of biomass and carbon stocks.In this paper, ecological principles, mathematical statistical methods and GIS spatial analysis techniques are adopted, with the use of the latest data of Forest Management Inventory in Babu County, Guangxi, application of the biomass expansion factor (BEF) which is relatively more mature source to studying the forest biomass and carbon storage in the area, and the analysis of characteristics and spatial distribution of carbon storage, and variance analysis of environment factors to carbon storage. In the study, combining land types of the technical specification of Forest Inventory with the requirements of biomass estimation and the characteristics of the biomass estimation model, the forest vegetation types are divided, the calculation methods of all vegetation types are described accurately, the database of forest biomass and carbon storage is established based on the sub-compart database of forest resources, with producing the maps of forest biomass and carbon storage by the use of geographic information system software, and establishing the biomass and carbon density spatial variation map by the use of vector graphics data gridding method. A study on temporal and spatial changes of carbon storage during 1999 and 2009 has been implemented. The primary results are:(1) 1172180.2t the total amount of forest vegetation biomass, among it, 8283011.3t the tree and shrub layer,1282786.8t under storey carbon storage, and 2146382.lt litter layer carbon storage, in Babu County.(2) 5942324.2t the total carbon storage of forest vegetation,5849565.3t the forest land, only 92758.9t the non forest land, in the whole county. The tree forest belong to forest land is the highest rate with an occupation 88.07% of the total. There are an average of 17.65t/hm2 of total,22.05t/hm2 of woodland, and 23.69t/hm2 of forest of carbon density.(3) The distribution and features are, that the carbon stock of forest vegetation is on the increase with the decrease in population density, and the carbon stock of forest vegetation is related to the land use, the carbon storage amount of forest is the biggest, closed forest is the biggest in which, and the carbon density of timber tree species is the biggest in which. It is shown that the forest carbon storage is closely related to the forest dominant species; the carbon storage of broad-leaved trees in timber forest is the biggest with the largest area, and Chinese fir take the first place of carbon density with 45.04t/hm2. The forest carbon storage is also related to the forest category and age group, the carbon density of special-forest is the highest with 33.87t/hm2, and forest carbon storage is increased with age group. The carbon density of artificial forest is higher than that of natural forest in Babu County. In the ecological public welfare forest, the carbon density of the provincial level of protection is ranked as the highest. In the vertical spatial distribution, the carbon storage is highest in an elevation of less than 500m, but the density of forest carbon is highest in an elevation of from 500m to 1500m, these just reflect that the different species have different biological characteristics. In the horizontal distribution, the carbon density with 15-50t/hm2 is the highest area, which is located in the eastern county of Nanxiang, forest farm of Huangdong Forest Farm, Daning town, the southwest of Pumeng, the north of Guiing, Lisong and the central of Butou town, etc. The area with Carbon density of more than 75t/hm2 is mainly distributed in the middle of inconvenient Huashui protection zone, the east of Hejie town, forest farm of Huangdong.(4) Applied the map of biomass and carbon density to analyzing the temporal and spatial changes uncovers the regulation of that:the carbon storage of forest vegetation increase greatly during 1999 and 2009 for the area of closed forest increased while non stocked land and sparse forest decreased, the mean carbon density increased, results increase of carbon storage. Except the broad-leaved forest, the carbon density of Chinese fir, Chinese red pine and eucalyptus is increased, the carbon density of age group of yang forest, middle age forest and near mature forest are decreased, and mature forest and over mature forest are increased. There is acreage of 103463.07hm2 in which the carbon storage decreased, it scattered over Huangdong Forest Farm and east of Hejie Town for the cutting and regeneration of mature forest and over mature forest, the change class of 0-10t/hm2 has the biggest acreage which distributed the plain towns and district with high density of population for the projects of "plantation of four sides" and "town and city greening ", the change class of over 75t/hm2 is fewer which is land of "return the grain plots to forestry". The paper put forward a series of forest management measures to increase the carbon storage contra posed the analysis result.(5) The advantages of estimating biomass and carbon storage in middle and small scale region with the Forest Management Inventory data are:A geographical coverage of the whole area, the detailed spatial distribution of information, abundant tree information, being able to establish biomass and carbon storage databases based on Sub-compartment, more comprehensive and accurate estimation of biomass in county scope. With reasonable forest vegetation type division according to the land use types of Forest Resource Inventory, we increase the compatibility of biomass and carbon density estimation and Forest Resource Inventory, put up with the reasonable solutions to incompatible parts and improve the estimation accuracy biomass and carbon stock of forest vegetation. Converting vector data into grid with geographical information systems is beneficial to the temporal and spatial variation analysis on carbon storage spatial distribution of matched grids. (6) It has been found with the variance analysis of qualitative ecological environment factors to biomass and carbon storage of forest vegetation:The terrain is the most important factor for it has significant effect on annual carbon density of Chinese fir, Chinese red pine, eucalyptus, and fast grow hard wood. Type of soil, aspects, and slopes affect significantly the annual carbon density of respective four spices, while the slope positions has significant effect only on other pine and hard wood. The Soil thickness has no significant effect on primary tree spices. The results of the analysis can guide local forest management.It point out in the paper, that there are some problems that the estimation biomass model of the bushes and other forest types is incompatible by making use of forest inventory data, and more model being compatible to Forest Inventory should be set up, to fully use multi data resources such as the environment, meteorology, and soil, to integrate the ensemble model to estimate the biomass and the carbon storage above and below ground of the timber forest, shrub forest, and bamboo forest.The methods and techniques of estimation of biomass and carbon storage, its feature analysis, and the temporal and spatial changes of carbon storage with GIS in the county level based the sub-compartments of Forest Inventory have been made by the paper have practical value and making reference of monitoring and evaluating forest vegetation biomass and carbon storage in the small and middle scale region.
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