| The potential effects of global warming are threatening the global economy, society, the ecological environment and even human survival. These threats have caused governments and scientists to examine and research as a top priority methods and policies regarding the adaptation and mitigation of climate change. Since forests contain the world's largest terrestrial carbon pool, activities that change the carbon dynamics of forests can affects the balance of the global carbon cycle. Land use change is one such activity that has great potential to change the carbon storage, sinks and sources of these ecosystems. Subsequently, terrestrial carbon emissions resulting from land use change has the potential to be only second to the carbon emitted from the combustion of fossil fuels. Therefore, evaluating ecosystem carbon stocks and dynamics within the context of different land use patterns not only provides basic data for ecosystem carbon cycle research, but also important knowledge necessary for development of strategies for forest ecosystem management and sustainable forestry.The carbon storage contribution of forest ecosystems in plantations, Karst holly hill and barren hill forests, and factors influencing this storage were studied in this dissertation. Also studying the ecological ethics of minority groups in regard to forest protection, and maintaining ecological balance and sequestered carbon is important in regard to future land use changes. The status of their traditional cultures and land inheritance in the future has the potential to impact future land use. Accordingly, a summary of the main conclusions of this research are as follows:1. The Composition and structure of vegetation measured in this studyA total number of66species, belonging to21families and representing35genera, were recorded in the plantation forests, with37species of eucalyptus (Eucalyptus sp.),34species of Masson pine (Pinus massoniana) and34Species of Chinese fir (Cunninghamia lanceolata). In the Karst holly hill ecosystem a total of35species belonging to20families and representing34genera were recorded. This was comparable to the Karst barren hill ecosystem where a total of32species, belonging to21families and representing32genera, were recorded. The species richness of Karst barren hill vegetation was the highest, followed by the Karst holly ecosystem and the Masson pine plantation in descending order.Evident vertical structure in three plantation ecosystems are as follows from top to botton:tree layer, shrub, herb and litter. Macrophanerophytes dominated the vegetation communities in all three ecosystems.2. The carbon storage of plantation ecosystemThe carbon storage of Masson pine, Chinese fir and eucalyptus plantation ecosystems are135.61t·hm-2,144.3t·hm-2and87.54t·hm-2respectively. The mean carbon stocks in these ecosystems are lower than average carbon stock reported for all of China's forest ecosystems (258.83t·hm-2).Tree layers were the important carbon pools in plantation ecosystems, the carbon stored in the tree layer of these plantations ranged from0.45~106.47t·hm-2,0.18~87.44t·hm-2, and2.68~31.62t·hm-2for Masson pine, Chinese fir, and eucalyptus, respectively, and increased with age. The average tree carbon storage of these plantations displayed a relationship of Masson pine> Chinese fir> eucalyptus. Except for young plantations, the tree carbon stocks contribute a significant portion to the total ecosystem, accounting for28.22%-62.43%of total ecosystem carbon storage.The understory carbon storage of Masson pine, Chinese fir and eucalyptus ranged from0.39~1.67t·hm-2,1.34~3.14t·hm-2and0.83~3.93t·hm-2respectively, accounting for0.23%-3.73%of total ecosystem carbon. The litter carbon stocks of Masson pine, Chinese fir and eucalyptus ranged from1.5~2.55t·hm-2,1.95~16.04t·hm-2and0.85~2.36t·hm-2respectively, accounting for0.85%~10.86%of the total ecosystem carbon.The soil carbon storage of Masson pine, Chinese fir and eucalyptus plantations are74.13,86.48and62.95t·hm-2respectively, accounting for60.6%~76.96%of total ecosystem carbon storage. The soil carbon sequestered within0-60cm depth decreases as soil depth increases. Carbon sequestered within0-20cm depth accounts for41.24%-62.54%of total soil carbon, and contributes the most to the total soil carbon pool. The carbon stored in the soil component of these plantation forests accounts for the highest carbon pool within these ecosystems. The total soil carbon stocks in all plantations decreases as plantations become older.3. The carbon storage of Karst holly hill ecosystemIt was determined that the total carbon stock within the Karst holly hill ecosystem was137.06t·hm-2. The tree carbon storage was35.41t·hm-2, accounting for25.83%of total ecosystem carbon. The carbon stored in the understory and litter layers is2.81t·hm-2and2.24t·hm-2, accounting for2.05%and1.63%of total ecosystem carbon, respectively. The carbon storage within the soil layers at depths of0-20cm and20-40cm ranged from41.01~88.92t·hm-2and33.19~47.4t·hm-2, respectively. The total soil carbon storage accounted for70.48%of total Karst holly hill ecosystem. The carbon stored in the tree and soil layers combined comprised the majority of the carbon stored in Karst holly hill ecosystem. The soil carbon layer contained2.73times more carbon than what was found in the tree layer.4. The carbon storage of Karst barren hillThe Karst barren hill vegetation was divided into two successional stages for the purpose of this study, represented by the herb community and the herb-shrub community. Each stage was separated into three layers for carbon analysis-the vegetation layer, the litter layer, and the soil layer. The total ecosystem carbon storage within the herb-shrub community was determined to be126.53t·hm-2, compared to60.93t·hm-2found in the herb community.Within the herb community, the carbon stock in the vegetation and litter layers was determined to be1.86t·hm-2and0.44t·hm-2, respectively. The carbon stock in the vegetation and litter layers within the herb-shrub community were determined to be8.43t·hm-2and0.32t·hm-2, respectively. The soil carbon stocks in the herb-shrub community and the herb community are117.78t·hm-2and58.63t·hm-2, accounting for 93.08%and96.23%of the total carbon within each of ecosystem, respectively. The carbon stored in the soil accounted for the majority of the carbon stock in the barren hill ecosystem.5. The comparsion of ecosystem of carbon storage in plantation, Karst holly hill and Karst barren hillThe amount of tree carbon stored in Masson pine and Chinese fir plantations was higher than the tree carbon stored in the Karst holly hill forests, with Masson pine forests displaying the highest of the three forests. However, the carbon stored in the vegetation and litter layers of the Karst holly hill and barren hill ecosystems was found to be higher than the understory layers in all the plantation forests. The carbon stored in the soil of the Karst holly hill was higher than that of the barren hill ecosystem, and the Masson pine and eucalyptus plantations, respectively, but lower than Chinese fir. The total carbon stocks found in middle-aged to over-mature Chinese fir and middle-aged to near mature Masson pine plantations were higher than the total carbon stocks found in the Karst holly hill ecosystem. The average value of carbon stored in the Masson pine ecosystem is lower than carbon found in the Karst holly hill ecosystem due to the number of young Masson pine plantations that were sampled. The total eucalyptus ecosystem carbon stocks were lower than what was found in the Karst holly hill and barren hill ecosystems due to the fact that young eucalyptus plantations were sampled in this study.6. Ethnography of protection of holly hillThrough literature review, semi-structured and key informant interviews, this study revealed that the traditional culture of animism has been formed in Sibao village over a long period of time. During this long period of time the vegetation of Karst holly hill ecosystem was well protected under their simple ecological ethic in this harsh Karst environment. This has played a significant role in protecting the vegetation of this ecosystem at the village level. Meanwhile, national policy has also affected the development of the Karst holly hill forest ecosystem. The combination of a national ecological compensation mechanisms and development of carbon sequestration projects to mitigate climate change will provide a better way to not only protect the Karst ecosystems but also improve living conditions of local villagers.
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