Characteristics and Pedogenesis of Podzolic Forest Soil along a Toposequence Near a Subalpine Lake in Northern Taiwan

台灣北部冷涼潮濕的亞高山檜木林下，經常可發現淋澱化土壤。本項研究乃針對高山湖泊(太平山加羅湖)旁，由山頂至湖畔的地形序列上的淋澱化土壤，探討土壤高濕度狀態對植物和土壤化育的影響，並釐清土壤中淋澱化作用的機制。研究結果顯示：除湖邊位置外，其餘各地形位置上之土壤皆具淋澱化作用。山頂與麓坡位置上土壤中的鐵鋁聚積土層（Bs層）中，以有機結合態的鐵和鋁為主。和腐植成份的黃酸所結合的鐵與鋁，由表層往下淋洗並聚積於Bs層。至於麓坡位置的土壤，鐵與鋁所蓄積形成之薄膠層（Bsm層），鐵和鋁的成份是以無定形態為主。根據此等結果可推論薄膠層的形成，主要是受到高雨量與季節性湖水位影響，導致水份長期滯留於麓坡位置上之土壤洗出層(AE層)和鐵鋁聚積層（Bs層）間，致使鐵還原並往下移動，經由反覆的氧化－還原作用，在土壤剖面洗出層與洗入層交界處形成一鐵磐層（薄膠層）。就地形效應而言，趨向湖邊位置，土壤水成特徵愈趨明顯，淋澱化作用則愈趨減弱。研究區域之土壤皆具淋澱化作用，但依目前美國土壤分類標準，卻未能將之歸類為淋澱土。主要的癥結，在於土壤中含有高量的黏粒及鐵鋁氧化物，使得有機物質或是和有機結合態的鐵鋁成份，皆未能順利往下洗入，以至於無法形成淋澱層。

關鍵字

黃酸；薄膠層；淋澱化土壤；淋澱化作用

並列摘要

Podzolic soils are commonly found under cypress forests in the subalpine region of northern Taiwan where the climatic conditions are cold and humid. Toposequential change from summit to lake shore along a subalpine lake (Lake Jialo) was selected to evaluate the influence of high soil moisture conditions on vegetation and pedogenic processes, and to clarify the mechanism of podzolization. Along this toposequence, the podzolization process occurs at all landscape sites except for the one at the lakeshore. Organicallycomplexed Fe and Al are the dominant forms in the Bs horizons at summit and footslope sites. The fulvic acids complex Fe and Al and translocate the latter downwards into the Bs horizons. The placic horizon in soils at the footslope is dominated by amorphous Fe oxides. Formation of placic horizons is mainly attributed to perched water, which is caused by heavy rainfall and seasonally high lake water level between the AE and Bs horizons. This situation causes Fe reduction and translocation to lower parts of the soil profile, resulting in formation of a placic horizon between E and Bs horizons. The soils towards the lakeshore are characterized by increasing dominance of hydromorphic process over podzolization. However, although the podzolization process occurs, the studied soils cannot be classified as Spodosols. High clay and crystalline Fe oxide contents derived from parent materials retard the mobility of organically-complexed metal cations and thus slow down the podzolization process and formation of spodic horizons in this area.

並列關鍵字

Fulvic acids ； Placic horizon ； Podzolic soils ； Podzolization

國際替代計量

Characteristics and Pedogenesis of Podzolic Forest Soil along a Toposequence Near a Subalpine Lake in Northern Taiwan

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