複雜地形高大森林生態系統二氧化碳之收支模擬

Modeling CO2 Assimilation Patten within a Tall Forest Ecosystem over a Complex Terrain

蘇淳太(Chun-Tai Su)

指導教授 ： 張能復

共同指導教授 ： 莊振義(Len-Fu Chang)

國立臺灣大學/工學院/環境工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.01278

摘要

地形的起伏會對於森林生態系及大氣之間的交互作用產生許多方面的影響，但目前僅有少數的研究同時考慮了地形的地伏、冠層渦流結構的改變、冠層光合作用以及淨生態系統二氧化碳的交換。本研究將針對平緩的餘弦形式的山丘，探討其輻射交換、中性流體動力分層之間的互相影響，以及生態生理學對於二氧化碳的源與匯的控制。由於風場的模擬與預期不符，因此本研究目前僅考慮無擾動項的風場，模擬山丘上內部區域及冠層內之二氧化碳濃度分佈，並對於太陽天頂角、葉面積密度及山丘高度做敏感度的分析。
本研究中，冠層的二氧化碳濃度分佈模擬結果合理顯示冠層內部的光環境與其二氧化碳濃度分佈的相關性，位於向光側的冠層，因光合有效輻射照度較高而二氧化碳濃度偏低，背光側的冠層則反之。
由二氧化碳通量模擬結果顯示，無論是冠層內部或是冠層外部，其通量傳輸的方向皆是指向冠層的頂部，由冠層內二氧化碳之源與匯可驗証冠層頂端之光合吸收率最高 (≅13.5μmolm^(-2) s^(-1))。
參數敏感度分析的結果顯示，對於二氧化碳濃度的變異上，最為敏感的參數為葉面積密度(-2.02%)，次之為太陽天頂角(+1.94%)以及山丘高度(+0.24%)，最不敏感者為光照強度(-0.17)。

關鍵字

冠層 ； 光環境 ； 擾動風速 ； 渦流通量 ； 光合作用

並列摘要

Undulating terrain will cause some impacts on the carbon exchange between the forest and the atmosphere, but only a few studies taken into account the fact of topography the exchange of vortex structure between above plants and within plants the influences of the photosynthesis in canopy and the net ecosystem carbon dioxide exchange. In order to quantify the topographic influence, in this study, we investigate the radiation exchange, the dynamic interaction between the fluid of neutral stratification and ecophysiological controls on carbon sources and sinks over an artificial cosine-shaped hill. In addition, the sensitivity analysis were conducted to explore the influences of different parameters, such as zenith angle, leaf-area-density and height of hill, on the model results.
The simulated CO2 concentration distribution within the canopy reasonably shows the strong correlations between concentration distribution within the canopy and the light environment over the hill (for sunlit and shaded sides). According to the simulation results of the carbon fluxes, the net photosynthesis assimilation rate is highest at top of the canopy which is close to 13.5μmolm^(-2) s^(-1). Finally, the results of sensitivity analysis showed that the most sensitive parameters to the CO2 concentrations was leaf area density(-2.02%), followed by solar zenith angle(+1.94%), height of the hill(+0.24%) and the illumination intensity(-0.17).

並列關鍵字

canopy ； light environment ； perturbation velocity ； eddy flux ； photosynthesis

參考文獻

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