土壤有機碳庫是全球碳循環的重要組成部分，並且直接影響全球的碳素平衡。本研究利用五節芒與培地茅為試驗材料，探討模擬自然環境生長下五節芒與培地茅對土壤碳庫之影響。結果顯示：自展開葉所測得之光合作用速率，五節芒較培地茅高，且地上部乾物重累積可達1966g pot^(-1) year^(-1)，為培地茅之3.67倍。而種植五節芒之不同土層土壤的有機碳(SOC)含量、δ^13C值及C %均顯著高於培地茅，顯示五節芒根圈衍生碳素釋入土壤碳庫能力較培地茅高。五節芒與培地茅種植一年後，由地上部測得之δ^13C值分別為-13.75‰與-13.4‰，顯示兩者皆屬C4途徑具高光合效率。另自其土壤測得總碳含量(C%)比慣行法栽培之水稻、玉米、狼尾草田區之土壤C%含量均較多。因此以上各項優點使五節芒與培地茅成為土壤保育、生物質原料、生態環境改良與土壤碳庫蓄積功能之優良草種。

Soil organic carbon (SOC) is an important component of the global carbon cycle and has direct effects on the global carbon balance. The objectives of this study were to determine the effects of Silver-grass and Vetiver grass on soil carbon pool in natural environmental conditions. The results showed that: The photosynthetic rate of Vetiver grass was lower than Silver-grass. The biomass of Silver-grass was larger than Vetiver, and the maximum dry weight was 1966g•pot^(-1)•year^(-1) 3.67 times higher than Vetiver grass. The values of SOC, δ^13C and C % in different depth of the soil from Silver- grass-planted were significantly higher than that from Vetiver-planted soil. Which indicated that the ability of Silver-grass root-derived carbon (C) input into the soil was better than Vetiver grass. The δ^13C values in shoot of Silver-grass and Vetiver grass were -13.75‰ and -13.4‰, indicated that Silver-grass and Vetiver grass were both high in photosynthetic efficiency. The C﹪values of soil planted Silver-grass and Vetiver grass were higher than rice, corn and elephant-grass in traditional cultivation system. Hence, silver-grass and vetiver grass have been proved to be the ultimate grass species for soil and water conservation, Biomass Feedstock, ecologic environment improvement and SOC storage.