臺灣溪頭柳杉林之樹冠結構與降雨及樹皮酸鹼性分佈： 利用攀樹技術的田野調查

Abstract

樹木截獲的降雨以及隨後產生的穿落水及幹流水在森林水文和生物地球化學循環中發揮著重要的功能。樹冠結構是影響森林生態系統的水輸入的重要因子。然而，關於三維的冠層結構對森林水文和生物地球化學循環的影響知之甚少。為了有助於詳細了解樹冠結構與雨水截留之間的關係，我重點研究了台灣溪頭柳杉林的樹冠投影模型、降雨截留和樹皮 pH 分佈。該研究的初步規劃是希望利用樹冠剖面模型的開發，有效地模擬柳杉的水分動態。然而，在溪頭柳杉林內的基礎研究尚未完成，因此在本研究中進行了初步研究。使用混合效應模型（線性和非線性）來表示樹枝級別的特徵（分支直徑、分支長度和分支角度）並發現具有完美的擬合度。樹木間的枝徑差異較小，枝長和角度則相反。除此之外，我從2021年7月至2022年4月採集了柳杉林分降雨再分配情況，計算截留率高達8.50%，穿落水比率80.12%，幹流水比率11.38%。在七個不同樹木參數中，樹冠投影面積是唯一顯著影響樹木幹流比率變化的因素。在我的最後一項研究中，使用瓊脂板沿樹幹垂直研究了樹皮 pH 值的周向和時間變化。結果表明，樹皮pH值隨時間和空間變化。由於幹流水浸出和附生植物導致樹皮pH值的變化，樹皮pH值的半方差在靠近地面處較高。未來的研究可能集中在通過與樹木對光和水的攔截相關聯以及樹皮結構對樹木垂直水分分佈的研究，將樹冠剖面模型應用到更大的應用中。本論文的研究可以為未來的研究提供非常實用的初步數據，這些研究側重於森林林分的樹冠和樹皮結構以及水動力學和養分循環的詳細建模。

Rainfall interception by trees and the subsequent production of throughfall and stemflow are known to play an important role in forest hydrological and biogeochemical cycles. Biotic factors like canopy structures are found to affect the water input in forested ecosystem. However, but less is known about the effects of three-dimensional canopy structure on forest hydrological and biogeochemical cycles. To contribute to the detailed understanding of the relationship between the crown structure and the canopy interception I focused on the crown projection model, rainfall interception, and bark pH distribution in a Cryptomeria japonica stand in Xitou, Taiwan. The initial planning of the study hopes to use the development of crown profile model so effectively model the water dynamics of Cryptomeria japonica. However, basic studies have not being done thus preliminary research was done in this study. A mixed-effect model (linear & non-linear) was used to represent tree branch level characteristics (branch diameter, branch length, and branch angle) and found to have a perfect fit. Variations among trees were small for branch diameter, while branch length and angle show the opposite. The rainfall redistribution of Cryptomeria japonica stand was collected from July 2021 through April 2022. Interception ratio was calculated as much as8.50% while throughfall ratio was 80.12% and stemflow ratio was 11.38%. Crown projection area was the only significant factor among seven tree parameters causing the variation of stemflow ratio among trees. For my final study, the circumferential and temporal changes of bark pH was studied vertically along the tree bole using agar panels. Results shows that bark pH changes along time and space. The semivariance of bark pH was higher closer to the ground due to the stemflow leaching and epiphytes that causes the change of pH in the bark. Future studies may focus at applying the crown profile model into great use by correlate with the interception of light and water by trees and the study of bark structures on the water distribution vertically on trees. The studies for this thesis can be very practical preliminary data for future studies that focus on the detailed modelling of canopy and bark structure and water dynamics and nutrient cycling in a forested stand.