以三種方法探討平地造林樹種碳吸存

Comparative Study Using Three Estimation Methods for Carbon Sequestration in the Plain Area

陳忠義(Chung-I Chen)

指導教授 ： 王亞男

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/博士(2017年)

https://doi.org/10.6342/NTU201700488

摘要

為了解平地造林之碳吸存量，本研究針對屏東萬隆農場12種平地造林樹種，分別以生長量、光合作用及渦流相關法估算林木碳吸存量，生長量法以每木調查配合材積式估算；光合作用推估法以光合作用光反應曲線配合葉面積指數估算碳同化；渦流相關法則藉由通量塔儀器架設監測林地碳吸存。結果顯示萬隆農場2010年造林木二氧化碳貯存量為23.36 Mg ha-1。以光合作用估算之二氧化碳吸存量為22.8 Mg ha-1 yr-1。生長量及光合作用推估法求得之林木淨初生產力(net primary production, NPP)，四年平均分別為4.13 Mg C ha-1yr-1及4.34 Mg C ha-1yr-1，兩種方法結果相近且有顯著正相關，可相互驗證。渦流相關法(net ecosystem production, NEP)與光合作用推估之碳吸存趨勢相近，且有顯著相關，顯示林木光合作用主導林分碳吸存的動態變化，進一步的回歸分析顯示，楝對試驗地固碳貢獻最高。以林分尺度來看，2010–2014年全林分碳吸存量平均為1.80 Mg C ha-1yr-1，主要受乾濕季影響而變動，年變動範圍在-0.88–4.25 Mg C ha-1yr-1之間，而環境因子中以相對濕度、土壤含水率及風速為主要影響林木固碳之因子。以屏東萬隆農場總面積約290 ha計算，每年可固碳共522 Mg。若欲建立以固碳為目的之森林，造林樹種選擇上應以楝較佳，而光蠟樹、陰香、欖仁、水黃皮、無患子則較不適合。通量塔可長期連續監測森林碳水收支及氣象資料，但仍需配合其他方法以了解各樹種之固碳貢獻，在應用上可配合生物量法或光合作用推估法。三種估算方式的量測與配合，除了可提供造林地在不同時間與空間尺度上，較精準且詳盡的碳吸存估算量，在以固碳為目標的森林經營方向上也能提供樹種選擇資訊。

關鍵字

生長量 ； 光合作用 ； 葉面積指數 ； 渦流相關法 ； 碳同化 ； 碳吸存

並列摘要

In this study, we used tree growth, photosynthesis measurement, and eddy covariance methods to estimate carbon sequestration in 12 plantation species in the Wan-Long farm. The tree growth method was based on complete enumeration of sample trees; the photosynthesis measurement method was based on construction of the light-response curve and measurement of leaf area index to estimate carbon assimilation; and the eddy-covariance method was based on measurement of CO2 exchange using instruments on a flux tower. In 2010, the woody tissue in this site fixed 23.36 Mg CO2 ha-1. The average CO2 sequestration was 22.8 Mg ha-1 yr-1, with large variation among years. The average woody net primary production was 4.13 Mg C ha-1 yr-1 as estimated by the tree growth method, and 4.34 Mg C ha-1 yr-1 as estimated by the photosynthesis measurement method (2011–2014). Thus, the significant positive correlation between the two methods provides confidence in the results. The eddy covariance-based net ecosystem production showed a similar pattern to, and a significant correlation with, photosynthetic-based carbon sequestration. According to the regression model, Melia azedarach might be the largest carbon sink among the 12 species. On the stand scale, carbon sequestration ranged from -0.88 to 4.25 Mg C ha-1 yr-1 during 2010–2014, and was 1.80 Mg C ha-1 yr-1 on average. The relative humidity, soil water content, and wind speed were the main factors affecting carbon sequestration. Therefore, the plantations were the main contributors to carbon sequestration in the stand, and the entire stand in the Wan-Long farm sequestered 522 Mg C yr-1. Therefore, we recommend Melia azedarach as the plantation species for the purpose of carbon sequestration in this site, but not Fraxinus formosana, Cinnamomum burmannii, Terminalia catappa, Pongamia pinnata, and Sapindus mukorossi. The flux tower is used for continuous long-term monitoring of the carbon–water budget and microclimate data; however, other estimating methods are required to understand the contribution of each species in the forest ecosystem. The use of a combination of these methods can aid in accurate estimation of carbon sequestration at different temporal and spatial scales. Additionally, this estimation can provide plantation species information for forest management.

並列關鍵字

tree growth ； photosynthesis ； leaf area index ； eddy covariance method ； carbon assimilation ； carbon sequestration

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