光蠟樹人工林碳貯存量和吸存量之估算

光蠟樹(Fraxinus griffithii C. B. Clarke)是台灣原生種，為台灣最重要的闊葉樹造林樹種之一。本研究以林業試驗所轄區內，位於六龜和太麻里試驗林的兩處光蠟樹人工林為對象，估算其造林木之生物量和生長量，建立根莖比和材積生物量轉換係數等參數和迴歸式，並估算其碳貯存量和吸存量。光蠟樹材積地上部生物量轉換係數，六龜林分為1.14 Mg m-3，高於太麻里林分的0.89 Mg m-3；根莖比則分別為0.235和0.233，兩林分相近。兩林分材積連年生長和平均生長曲線皆隨年齡而呈上升趨勢，但尚未相交。經估算，六龜林分光蠟樹地上部生物量為121 Mg ha-1，高於太麻里林分的114 Mg ha-1。光蠟樹林分全部植物地上部生物量達163-199 Mg ha-1，不低於台灣年齡相近的闊葉樹人工林。經分析光蠟樹植體的碳濃度為48.3-50.9%。推估光蠟樹全株碳吸存量，六龜林分光蠟樹平均可吸存碳2.58 Mg ha-1 yr-1，即吸存9.47 Mg ha-1 yr-1 CO2；太麻里林分則為1.93 Mg ha-1 yr-1，即吸存7.08 Mg ha-1 yr-1 CO2，大致上與台灣主要闊葉樹造林樹種全株碳吸存量相近。但低於熱帶地區闊葉人工林如桉樹等的碳吸存量。以整個生態系而言，兩林分碳貯存量，六龜林分為175 Mg ha-1，太麻里林分為230 Mg ha-1，土壤分別佔生態系碳貯存量的44.7%和47.7%，在生態系碳貯存量上扮演主要角色。

Fraxinus griffithii C. B. Clarke, a native tree species in Taiwan, is one of the most important broadleaf afforestation tree species in Taiwan. This study selected two planted Fraxinus griffithii forests located in the Liugui and Taimali experimental forests under the jurisdiction of the Taiwan Forestry Research Institute as research objects, aiming to estimate the biomass and growth of the planted trees, establish parameters such as root-to-shoot ratio and volume-to-biomass conversion factors, as well as regression equations, and calculate their carbon storage and carbon sequestration amounts. The volume-to-aboveground biomass conversion factor of Fraxinus griffithii was 1.14 Mg m⁻³ for the Liugui stand, which was higher than the 0.89 Mg m⁻³ of the Taimali stand; the root-to-shoot ratios were 0.235 and 0.233, respectively, with minimal differences between the two stands. The annual volume growth and mean volume growth curves of both stands showed an upward trend with stand age, and had not yet intersected. The estimated aboveground biomass of Fraxinus griffithii in the Liugui stand was 121 Mg ha⁻¹, higher than the 114 Mg ha⁻¹ of the Taimali stand. The total aboveground vegetation biomass of the Fraxinus griffithii stands ranged from 163 to 199 Mg ha⁻¹, which was not lower than that of broadleaf planted forests of similar ages in Taiwan. Analysis showed that the carbon concentration of Fraxinus griffithii tissues was 48.3–50.9%. The estimated whole-plant carbon sequestration rate was 2.58 Mg ha⁻¹ yr⁻¹ for the Liugui stand, equivalent to sequestering 9.47 Mg ha⁻¹ yr⁻¹ of CO₂; the rate for the Taimali stand was 1.93 Mg ha⁻¹ yr⁻¹, equivalent to 7.08 Mg ha⁻¹ yr⁻¹ of CO₂. This was generally comparable to the whole-plant carbon sequestration rates of major broadleaf afforestation tree species in Taiwan, but lower than those of tropical broadleaf planted forests such as Eucalyptus. For the entire ecosystem, the total carbon storage of the Liugui stand was 175 Mg ha⁻¹, and that of the Taimali stand was 230 Mg ha⁻¹; soil accounted for 44.7% and 47.7% of the ecosystem carbon storage, respectively, playing a dominant role in ecosystem carbon storage.