臺灣溪頭孟宗竹林土壤呼吸之時間變異及影響因子

Temporal variation in soil CO2 efflux and the controlling factors in a moso bamboo forest, central Taiwan

謝宜芳(I-Fang Hsieh)

指導教授 ： 久米朋宣

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/碩士(2013年)

https://doi.org/10.6342/NTU.2013.01616

摘要

土壤呼吸在陸域碳循環中扮演相當重要的角色，在評估森林固碳效益時為不可或缺之一環。土壤呼吸之特性依生態系統而異，植被以及土地利用型態的改變，必然會改變土壤呼吸之特性，進而影響區域之中的二氧化CO2釋出量。在台灣，孟宗竹林引進自中國大陸，主要分布於台灣中部地區，其快速生長的特性使得許多竹林在廢耕之後快速擴張，侵略並取代週遭植被。為了瞭解竹林擴張可能導致的碳循環改變，首先必須釐清孟宗竹林土壤呼吸的特性。本研究主要探究孟宗竹林土壤CO2通量之時間變異以及受環境因子的影響。自2012年4月起，於溪頭實驗林中選定孟宗竹純林，以動態密閉氣室法，進行每月一至二次，為期一年之土壤二氧化碳通量監測，並以數據配合前人提出之模式建立實驗式。結果指出，土壤呼吸速率具有不定趨勢之日變化現象，在總呼吸速率較高的測量日期之中，日變化中之最高速率可超出最低速率之兩倍；土壤呼吸速率亦具有明顯之季節變異，呼吸速率於生長季(4月)及夏季(6-9月)達最高，冬季月份最低，範圍由1.54至 7.98 μmol m-2s-1。土壤溫度對於土壤呼吸速率季節變化之影響力大於土壤含水率，溫度對呼吸速率具有非線性相關，評估結果以 Q10公式對於解釋土壤溫度對土壤呼吸速率影響表現最佳。Q10指數為5.14，亦即土壤溫度上升10℃，呼吸速率將增加5.14倍。以Q10公式預測本樣區土壤呼吸年量為1304.85 gCm-2yr-1，高於鄰近之柳杉林。本研究結果可用以評估植被改變對於土壤呼吸以及碳循環的影響，並在以減緩溫室氣體排放為導向的林相經營策略上具有重要參考價值。

關鍵字

土壤呼吸 ； 孟宗竹 ； 時間變化 ； 環境因子 ； Q10指數

並列摘要

Understanding soil respiration (RS) in moso bamboo stands is crucial for accessing potential impact of bamboo invasion on terrestrial carbon cycle in Asian regions. This study aimed to evaluate the seasonal and diurnal variations of RS in a moso bamboo (Phyllostachys pubescens) forest in central Taiwan with their abiotic drivers and to estimates annual Rs based on their temporal change characteristics. We selected a 401 m2 plot in a conservatively managed moso bamboo stand in National Taiwan University Forest, central Taiwan. The 20 measuring locations were set in a 401 m2 plot. RS rates were measured from April 2012 to April 2013 by using a closed dynamic chamber system. Once a month, we observed the RS averaged over the 20 locations and the diurnal variation at 2 locations with soil temperature (TS) and soil volumetric water contents (SWC) measurements. To characterize seasonal variations in Rs, using models proposed by previous studies, this study examined the model performs in describing RS with TS and/or SWC.
RS showed distinctive diurnal variations in some measurement campaigns. In the measurement campaign on June, we found the maximum RS rate exceed twice the minimum rate (from 3.43 to 9.91 μmol m-2s-1). One year observation showed RS averaged over 20 locations ranged from 1.54 to 7.98 μmol m-2s-1 with the highest RS in the summer season. Seasonal variations of RS were considerably corresponded to TS. The relationship between RS and TS could be described the most significantly with the exponential Q10 function. In the equation, the Q10 value of 5.07 estimated in this study was considerably higher than those of adjacent Japanese cedar plantations under the same weather condition and the average from worldwide literatures (= 2 to 3). Estimated annual RS rate using the function and continuously measured Ts was 1304.85 gCm-2yr-1, which was higher than that of the Japanese cedar plantations (661 to 729 gCm-2yr-1). Our results provided crucial information of the major CO2 source in moso bamboo forest in Sitou, Taiwan.

並列關鍵字

soil respiration ； moso bamboo ； biotic factors ； temporal variation ； Q10 value

參考文獻

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