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題 名 | 森林林下光照度之數學模型建立=Establishment of Forest General Light Index Model |
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作 者 | 黃皇男; 孫義方; 何肇寶; | 書刊名 | 東海學報 |
卷 期 | 39:2(理學院) 民87.07 |
頁 次 | 頁65-77 |
分類號 | 436.12 |
關鍵詞 | 光照度; 森林動態; 光度測量計; 有效輻射; 魚眼鏡照片; Light availability; General light index; GLI; Forest dynamics; Quantum sensor; Photosynthetically active radiation; PAR; Fisheye photography; |
語 文 | 中文(Chinese) |
中文摘要 | 影響森林動態的因子可分成二大煩:一類是非生物性的因子,如光照、土壤養分、 雨量等;另一類是生物性的因子,如種子傳播的行為、草食動物的行為等。本論文主要目的 在建立森林林下光照度之數學模型。森林林下光照度(GLI,單位為%)之值可表成為:[GLI= (T□ x P□ + T□ x P□)x100] 其中P□及P□指在樹冠層(Canopy)上所能收到太陽對 光合作用的有效輻射(PAR)量中,分別屬於背景輻射或直射輻射之光量;而T□及T□則 是指P□及P□的光量通過樹冠間到達地表之比率。GLI之值會受樹縫之形狀而從0到100 之間變動,而P□及P□原可依據氣象站之量測值來估算,但台灣本地之氣象站均無法提供 此值,因此參考國外研究,將其值分別假設為0.65及0.35。T□之值可藉由分析樹冠層下所 拍攝之魚眼鏡照片影像而得,又經由計算魚眼鏡照片拍攝當日之太陽每日之軌跡可T□之值。 最後,我們依據上述GLI數學模式,撰寫程式以計算出拍照地點之GLI值。雖然此值並無 法代表到達地面之實際光照,但卻可以提供樹冠層下不同地點之相對光照度的關係。 |
英文摘要 | The factors that affect forest dynamics include abiotic factors, such as light, soil nutrients, rainfall, as well as biotic factors, such as seed disperser, herbivores and intra-or inter-competitions. This paper is focused on how to simulate the environmental factors, especially light, affects that dynamics of the forest. A general light index (GLI) is defined to represent the local light availability at certain specified location in the understrory. The GLI is of the form GLI=(T□ x P□ + T□ x P□)x100 where P□ and P□ are the portions of incident seasonal photosynthetically active radiation(PAR) received at the top of the canopy as either sky radiation or direct beam radiation, respectively (P□=1-P□). And the T□ and T□ are the transmitted through the gap to a point in the understory. This index ranges from 0, when there is no clearly defined gap visible in the canopy, to 1 for a site in the open. Since there is no weather station can provide the values for P□ and P□ , we use 0.35 and 0.65 as their typical values, respectively, which are chosen according to the research results of some intermational projects. A computer program is developed to digitize the fisheye photography, and then compute the whole-season light availability due to the diffuse radiation, T□, But for the direct light availaility, T□, only the values for those days in which the photography was taken are computed. Finally, for any fisheye picture, we can compute the associated GLI for it. Although it can't indicate the real understory light availability, but it represents the relative light availability at different locations within the canopy. The computed GLI will be tested using the measurements of PAR by quantum sensor around the gaps of the forest in our future study. |
本系統中英文摘要資訊取自各篇刊載內容。