南仁山溪谷樣區土壤水份含量與土壤溶液組成隨時間與空間之變異

Temporal and Spatial Variability in Soil Water Content and Soil Solution Compositions at Nanjenshan Subtropical Rain Forest

陳慧美(Hui-Mei Chen)

指導教授 ： 陳尊賢

國立臺灣大學/生物資源暨農學院/農業化學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01405

摘要

土壤水份及土壤溶液化學組成的動態變化，對於了解南仁山亞熱帶雨林森林生態系統內，水份及養份之輸出與輸入間的平衡關係非常有幫助，是一個重要的基本資料。土壤水份及土壤溶液組成的化學性質，可提供土壤中養分或元素隨空間與時間的分佈情形，以及對於植物的養分分佈與貯存的重要訊息。本研究的目的為探討南仁山樣帶樣區中，在不同的季節（乾、濕季）、不同的地形位置（頂坡、背坡及麓坡）及不同的土層深度下（0-20、20-40、40-60、60-80公分）：（1）土壤水份含量隨空間（地形位置）與時間（季節變化）的變異，（2）比較不同的溶液收集方式（現地壓力溶液、實驗室壓力溶液、滲漏平衡溶液及離心平衡溶液）之間，土壤溶液組成隨空間的變異，（3）實驗室壓力之溶液組成隨空間分佈與季節性的變異以及（4）滲漏平衡溶液（重力水溶液）於各土層中的養分流通量推估。
本研究選擇南仁山長期生態研究站中，南仁山西北側稜線之一公頃長形溪谷樣帶為研究區域，包括四種地形位置，即麓坡（海拔250-330公尺之間）、下位背坡（海拔330-400公尺之間）、上位背坡（海拔400-450公尺之間）及頂坡（海拔450-470公尺之間）。在此研究區共劃分25區，每區20×20 公尺，於2001年十月至2003年五月期間以TDR現地測量各土層深度的土壤水份含量，另外，在2002年至2003年期間，現地以多孔性的土壤溶液收集器抽取土壤溶液及取土回實驗室進行不同方法溶液萃取分析，分析土壤溶液中各陰陽離子之組成。
研究結果顯示，植被組成及地形可能是影響本研究區中土壤水份含量及土壤溶液組成的關鍵因子。表土20公分水份含量有較高的趨勢，底土的水份含量測值變異較小，較不受季節影響。不同土壤溶液抽出方式的比較中，以實驗室壓力萃取法的溶液組成與現地壓力萃取法所得之溶液組成之間相關最好，其中以硝酸態氮、氨態氮、鉀、鈉等離子的監測結果較一致。鈉及氯離子是實驗室壓力溶液中較佔優勢的陰陽離子，養分來源主要受降雨及東北季風挾帶鄰近海洋中之鹽分的輸入所致，因此受季節變化較大。氨態氮、鐵、鋁、矽等離子濃度除了在土層20公分有較大變異外，隨著土層深度的增加而有減少的趨勢。滲漏溶液中硝酸態氮、硫酸、鉀、鈉離子於各地形位置的輸出量均大於輸入量（kg/ha/yr），有淨釋放現象，可能藉由雨水洗入附近河川，而滲漏溶液中的鐵、鋁、鈣離子於各地形位置中輸入量則大於輸出量，有淨吸持的現象，推測其來源為礦物風化而來。

關鍵字

時間與空間變異 ； 養分輸出及輸入 ； 土壤水份含量 ； 土壤溶液組成

並列摘要

The dynamics of soil water content and soil solution composition plays an important role on the nutrient and water cycling in natural forest ecosystem, especially on the nutrient balance between input and output of water and nutrient. They control and reflect the development and differentiation of the soil profile. The soil water content and chemical composition of soil solutions provide to understand the important information about the spatial and temporal distribution of soil nutrients and their mobility and bioavailability for the plants. The objectives of this study are（1）to examine the spatial distributions and seasonal changes of soil water contents,（2）to compare the difference of soil solution composition collected by field tension, laboratory tension, centrifuge, and percolation methods for different landscape and different depth soils,（3）to examine the spatial distributions and seasonal changes of ionic concentrations of soil solution extracted by laboratory tension method for different landscape and different depth soils, and（4）to estimate the potential annual leaching of cations and anions from different soil depth and different landscapes in the study area.
The study site was located at the River valley region of Nanjenshan long-term ecological research site of southern Taiwan. One hectare of study site has four landscape positions including footslope ranging from 250 to 330m, lower backslope ranging from 330 to 400m, upper backslope ranging from 400 to 450m, and summit ranging from 450 to 470m, respectively. Each representative sampling plot is 20 x 20 meter square. Soil moisture content was monitored in the field by the time-domain reflectometry（TDR）from 2001 to 2003. The soil solution compositions were monitored by two collecting methods including directly sampled soil solution in the field and taking the soil samples for extracted the soil solution by different methods in the laboratory from 2002 to 2003.
The results indicated that vegetation types and landscape positions are key factors to affect the soil water content and soil solution composition in the study area. Higher spatial variability of soil water content was occurred in the 20cm depth of topsoil, but much lower spatial variability occurred in the deeper soil layer. The ionic concentration of soil solution extracting from field tension method have significant correlation with laboratory tension method, especially for NO3-N, NH4-N, K+, and Na+. Sodium and chloride ion are the dominant cations and anions extracted by laboratory tension method. Nutrient concentration input from rainfall and monsoon carrying salt come from the sea can lead to high spatial variability of the chemical composition of soil solutions in this study. The concentrations of NH4-N, Fe, Al, and Si are generally highest in the soil solution of 20cm depth of topsoil, and decreased with soil depth. The net nutrient release was calculated by percolation balance method for NO3-N, SO42-, K+, and Na+ ions, but the net nutrient retention mainly cause by weathering process.

並列關鍵字

seasonal change ； spatial and temporal variation ； Soil moisture content ； Nanjenshan long term ecology research site ； landscape position ； monsoon ； soil solution composition

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