第 3 章 材料與方法
3.2 臺灣各縣市代表性土壤的分類
3.2.2 分類的經驗法則
當1960-70 年代所調查的舊土壤調查報告書，要使用近代 WRB 的診斷內容來 分類時，特別是WRB 的許多要求在以往從未出現過，往往會遇到舊資料沒有相關 資料可以符合WRB 內容的窘境，此時必須要秉持 2 項分類原則，分別是推估原則 以及呼應原則。
1. 推估原則
當WRB 的診斷特性要求某項內容時，若是舊資料沒有具備，將盡量以舊資料 具備的其他資訊推測，若是推測的結果不符合此項內容，則不會分入此診斷特性。
2. 呼應原則
由於要具備世界土壤的完整性，WRB 的診斷特性會有很多選項 (and/or)，在 分類時必須找到最主要特性來加以呼應。在診斷特性列出的項目都要符合下，當 丙項目的要求在舊資料中缺乏 (且也無法利用推估原則來符合)，而丙項目是較次 要或是可以被其他甲、乙項目取代時，則將考慮舊資料內能夠符合甲或乙的內容 來加以呼應。若舊資料沒有一個項目能夠符合時，則不會分入此診斷特性。
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Organic material > 40 cm Yes → Histosols
↓ No
Human induced horizons Yes → Anthrosols
↓ No
↓ NoPlinthite, petroplinthite or
pisoplinthic horizon Yes → Plinthosols
↓ NoNitic horizons Yes → Nitisols
↓ NoFerralic horizon Yes → Ferralsols
↓ NoAbrupt textural change Yes → Planosols
↓ NoStagnic properties Yes → Stagnozems
↓ NoChernic or blackish mollic horizon and secondary CaCO3
Yes → Chernozems
↓ NoBrownish mollic horizon and secondary CaCO3
Yes → Kastanozems
↓ NoMollic horizon Yes → Phaeozems
↓ NoGypsic or petrogypsic horizon Yes → Gypsisols
↓ NoDuric or petroduric horizon Yes → Durisols
↓ NoCalcic or petrocalcic horizon Yes → Calcisols
↓ No(接下頁)
16 Argic horizon with CECc > 24,
BS < 50% Yes → Alisols
↓ NoArgic horizon with CECc < 24, BS < 50%
Yes → Acrisols
↓ NoArgic horizon with CECc > 24,
BS > 50% Yes → Luvisols
↓ NoArgic horizon with CECc < 24,
BS > 50% Yes → Lixisols
↓ NoUmbric horizon Yes → Umbrisols
↓ NoCoarse texture Yes → Arenosols
↓ NoCambic or other developed
horizon Yes → Cambisols
↓ NoOther soils Yes → Regosols
圖1、簡易參考土類索引 Fig1. Key to the RSGs (修改自Deckers et al (2002))
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以下將提出本論文中所有新舊不接的情形，並列出各情形下利用推估及呼應 兩個原則來彌補不足的方法。另外也提出本論文常出現的參考土類之索引內容，
和診斷層、特徵及物質之診斷標準。
(一) 適用推估及呼應原則之情形 (按字母順序列出)
A. Anthraquic horizon (水田耕作層)
WRB 對 Anthraquic horizon 的診斷特性如下 An anthraquic horizon is a surface horizon and has:
1. a puddled layer with both:
a. a Munsell hue of 7.5 YR or yellower, or GY, B or BG hues; value (moist) of 4 or less; chroma (moist) of 2 or less1; and
b. sorted soil aggregates and vesicular pores; and
2. a plough pan underlying the puddled layer with all of the following:
a. a platy structure; and
b. a bulk density higher by 20 percent or more (relative) than that of the puddled layer; and
c. yellowish-brown, brown or reddish-brown iron-manganese mottles or coatings; and 3. a thickness of 20 cm or more.
WRB 描述 Anthraquic horizon 包含 puddled layer (混攪層) 及 plough pan (耕犁 層) 兩個部分的描述，但在舊資料中的水田土壤調查內容中通常不包含整齊一致的 土壤團粒及囊洞 (sorted soil aggregates and vesicular pores) 來描述混攪層，也不包 含platy structure (盤狀構造) 及 bulk density (總體密度) 來描述壓實的耕犁層，因 此根據經驗法則及合理推論，若背景描述中提到此土壤主要為水田耕種，且表層 土壤符合顏色要求可呼應到混攪層，底層土壤 (表土以下至 30-40 cm 以上) 具有 符合規定的鐵錳斑紋可呼應到耕犁層，即可診斷具有Anthraquic horizon。
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B. Argic horizon (黏聚層)
WRB 對 Argic horizon 的診斷特性如下
1. has a texture of loamy sand or finer and 8 percent or more clay in the fine earth fraction; and
2. one or both of the following:
a. has, if an overlying coarser textured horizon is present that is not ploughed and not separated from the argic horizon by a lithological discontinuity, more total clay than this overlying horizon such that:
i. if the overlying horizon has less than 15 percent clay in the fine earth fraction, the argic horizon must contain at least 3 percent more clay; or ii. if the overlying horizon has 15 percent or more but less than 40 percent clay in the fine earth fraction, the ratio of clay in the argic horizon to that of the overlying horizon must be 1.2 or more; or
iii. if the overlying horizon has 40 percent or more total clay in the fine earth fraction, the argic horizon must contain at least 8 percent more clay; or b. has evidence of clay illuviation in one or more of the following forms:
i. oriented clay bridging the sand grains; or ii. clay films lining pores; or
iii. clay films on both vertical and horizontal surfaces of soil aggregates; or iv. in thin section, oriented clay bodies that constitute 1 percent or more of the section; or
v. a coefficient of linear extensibility (COLE) of 0.04 or higher, and a ratio of fine clay1 to total clay in the argic horizon greater by 1.2 times or more than the ratio in the overlying coarser textured horizon; and
3. has, if an overlying coarser textured horizon is present that is not ploughed and not separated from the argic horizon by a lithological discontinuity, an increase in clay content within a vertical distance of one of the following:
a. 30 cm, if there is evidence of clay illuviation; or b. 15 cm; and
4. does not form part of a natric horizon; and
5. has a thickness of one-tenth or more of the sum of the thicknesses of all overlying horizons, if present, and one of the following:
a. 7.5 cm or more, if it is not entirely composed of lamellae (that are 0.5 cm or more thick) and the texture is finer than loamy sand; or
b. 15 cm or more (combined thickness, if composed entirely of lamellae that are 0.5 cm or more thick).
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表3、pH 相對應之鹽基飽和度
Table 3. pH and its corresponding BS%
pH < 5 pH 5-6 pH > 6
BS% < 50% 當下層底土pH > 5.7 時, BS% > 50%。
當下層底土pH < 5.3 時, BS% < 50%。
BS% > 50%
註：此換算來自陳尊賢教授口述。
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D. Cation Exchangeable Capacity (陽離子交換能力，簡稱 CEC)
當土壤調查報告書中缺乏土壤剖面 CEC 的數據，原則上可利用以下運算式算 出，但倘若資料也無法提供有機碳及黏土礦物資料時，則可利用質地來大略推估 (表 4)。
CECtotal = CEC contribution by organic matter + CEC contribution by clay
E. Fluvic material (沖積物質)
WRB 對 Fluvic material 的診斷特性如下
Fluvic material is of fluviatile, marine or lacustrine origin that shows stratification in at least 25 percent of the soil volume over a specified depth; stratification may also be evident from an organic carbon content decreasing irregularly with depth, or remaining above 0.2 percent to a depth of 100 cm from the mineral soil surface. Thin strata of sand may have less organic carbon if the finer sediments below meet the latter requirement.
臺灣各縣市土壤調查報告書的各層有機碳數據常出現缺乏，因此需利用土壤各 層的土色、質地、構造及其他岩性的不規則變化來推估到沖積物質。
F. Gleyic colour pattern (灰白色彩型態)
WRB 對 Gleyic colour pattern 的描述如下Soil materials develop a gleyic colour pattern if they are saturated with groundwater, unless drained, for a period that allows Reducing conditionss to occur (this may range from a few days in the tropics to a few weeks in other areas), and show a gleyic colour pattern.
WRB 對 Gleyic colour pattern 的診斷特性如下
A gleyic colour pattern shows one or both of the following:
1. 90 percent or more reductimorphic colours, which comprise neutral white to black (Munsell N1/ to N8/) or bluish to greenish (Munsell 2.5 Y, 5 Y, 5 G, 5 B); or 2. 5 percent or more mottles of oximorphic colours, which comprise any colour,
excluding reductimorphic colours.
Gleyic colour pattern是由地下水浸泡造成的還原特徵，會造成土壤出現高比例 的還原色彩型態。但由於舊土壤調查報告書並不會詳細寫出土層呈現還原色彩的 比例，因此將 「土壤基質的顏色」(土色) 當作相應的色彩型態，當土壤基質色彩 符合上述顏色要求時即推估到 Gleyic colour pattern。
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表4、質地所相對應之陽離子交換能力 (CEC) Table 4. Certain Texture with their corresponding CEC
Texture CEC (cmolc/kg soil)
Clay > 30
CL 15-30 Middle size (SiL, SiCL, L, SL, SCL) 5-15
Coarse size (LS, S) < 5 註：
1. 此表修改自 Hausenbuiller (1985)
2. 此僅討論一般土壤 (沖積土、化育黃壤及紅壤)，有機碳一般在 2%以下。有機質特 別高的有機質土及灰燼土、或是黏粒組成是特殊層狀黏土礦物的特殊情況不在此 考慮範圍。
3. CEC 是利用 pH 7, 1N NH4OAc 所測，若是較低的酸性土壤 (紅土)，則得到的 CEC 值通常會被高估，應該要減少2-4 cmolc/kg soil 才是真實 CEC。
4. 本表的單位為 cmolc/kg soil，需進一步換算成 WRB 使用的 cmolc/kg clay。
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G. Hydragric horizon (人為浸水層)
WRB 對 Hydragric horizon 的描述如下
A hydragric horizon (from Greek hydor, water, and Latin ager, field) is a humaninduced subsurface horizon associated with wet cultivation.
WRB 對 Hydragric horizon 的診斷特性如下
A hydragric horizon is associated with wet cultivation and has:
1. one or more of the following:
a. Fe or Mn coatings or Fe or Mn concretions; or
b. dithionite-citrate extractable Fe 2 times or more, or dithionite-citrate extractable Mn 4 times or more that of the surface horizon; or
c. redox depleted zones with a Munsell colour value 4 or more and a chroma of 2 or less (both moist) in macropores; and
2. a thickness of 10 cm or more.
由於診斷特性僅需符合其一及厚度即可，因此若報告書中具有游離鐵數據即以 其為診斷內容；若報告書缺乏游離鐵數據，僅描述出現在各層的斑紋 (將其代表為 鐵錳斑紋)，則斑紋量達多量 (或量 > 20%) 以上則也可符合 Hydragric horizon。
H. Irragric horizon (灌溉沉積層)
WRB 對 Irragric horizon 的描述如下
The irragric horizon is a humaninduced mineral surface horizon that builds up gradually through continuous application of irrigation water with substantial amounts of sediments, and which may include fertilizers, soluble salts, organic matter, etc.
WRB 對 Irragric horizon 的診斷特性如下 1. a uniformly structured surface layer; and
2. a higher clay content, particularly fine clay, than the underlying original soil; and 3. relative differences among medium, fine and very fine sand, clay and carbonates
less than 20 percent among parts within the horizon; and
4. a weighted average organic carbon content of 0.5 percent or more, decreasing with depth but remaining at 0.3 percent or more at the lower limit of the irragric horizon; and
5. 25 percent (by volume) or more of animal pores, coprolites or other traces of soil animal activity; and
6. a thickness of 20 cm or more.
舊土壤調查報告書的內容缺乏第1、3、5 項的統一構造及生物洞等要求，僅具 有第2、4 項及厚度等要求的內容，因此土壤符合第 2、4、6 項即可呼應到 Irragric horizon。
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I. Plinthic horizon (鐵網紋層)
WRB 對 Plinthic horizon 的描述如下
A plinthic horizon (from Greek plinthos, brick) is a subsurface horizon that consists of an Fe-rich (in some cases also Mn-rich), humus-poor mixture of kaolinitic clay (and other products of strong weathering, such as gibbsite) with quartz and other constituents, and which changes irreversibly to a layer with hard nodules, a hardpan or irregular aggregates on exposure to repeated wetting and drying with free access of oxygen.
WRB 對 Plinthic horizon 的診斷特性如下 A plinthic horizon has:
1. within 15 percent or more of the volume single or in combination:
a. discrete nodules that are firm to weakly cemented, with a redder hue or stronger chroma than the surrounding material, and which change irreversibly to strongly cemented or indurated nodules on exposure to repeated wetting and drying with free access of oxygen; or
b. mottles in platy, polygonal or reticulate patterns that are firm to weakly cemented, with a redder hue or stronger chroma than the surrounding material, and which change irreversibly to strongly cemented or indurated mottles on exposure to repeated wetting and drying with free access of oxygen; and c. less than 40 percent of the volume strongly cemented or indurated nodules
and no continuous, fractured or broken sheets; and 2. both:
a. 2.5 percent (by mass) or more citrate-dithionite extractable Fe in the fine earth fraction or 10 percent or more in the nodules or mottles; and b. a ratio between acid oxalate (pH 3) extractable Fe and citrate-dithionite
extractable Fe of less than 0.101; and c. a thickness of 15 cm or more.
舊土壤調查報告書內不同型態鐵的數據並不完整，缺乏第2 項的要求，因此根 據呼應原則，若是土壤報告書內紀錄斑紋及鐵錳結瘤的數量及色彩符合規定，則 即可呼應到Plinthic horizon。
J. Reducing conditions (還原情形)
WRB 對Reducing conditions的規定原文如下
Reducing conditions (from Latin reducere) show one or more of the following:
1. a negative logarithm of the hydrogen partial pressure (rH) of less than 20; or 2. the presence of free Fe2+, as shown on a freshly broken and smoothed surface of
a field-wet soil by the appearance of a strong red colour after wetting it with a 0.2-percent α, α, dipyridyl solution in 10-percent acetic acid1; or
3. the presence of iron sulphide; or 4. the presence of methane.
原文規定中的每一點要求，在舊資料裡都沒有提供。為了使舊資料有效化，可 以利用合理知識推估，在此可用其他特性如顏色判斷，當色彩呈現厭氧 (N, 2.5Y, 5Y, 5G 或 5B) 及色度極低 (≦1) 時可判斷此土壤為 Reducing conditions。
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K. Stagnic colour pattern (淹水色彩型態)
WRB 對 Stagnic colour pattern 的描述如下Soil material has a stagnic colour pattern (from Latin stagnare, to stagnate) if it is, at least temporarily, saturated with surface water, unless drained, for a period long enough to allow Reducing conditionss to occur (this may range from a few days in the tropics to a few weeks in other areas).
WRB 對 Stagnic colour pattern 的診斷特性如下
A stagnic colour pattern shows mottling in such a way that the surfaces of the peds (or parts of the soil matrix) are lighter (at least one Munsell value unit more) and paler (at least one chroma unit less), and the interiors of the peds (or parts of the soil matrix) are more reddish (at least one hue unit) and brighter (at least one chroma unit more) than the non-redoximorphic parts of the layer, or than the mixed average of the interior and surface parts.
Stagnic colour pattern 乃受到表面水一段時間淹浸而產生的還原色彩型態，其診 斷特性內容包含表面土 (surfaces) 及內土 (interiors) 的斑紋與土壤基質的比較，
但舊土壤調查報告書型態描述中並未細分土壤的內外型態，因此合理推斷皆是土 壤表面的色彩型態，所以當報告書中記錄的斑紋色彩，所顯示的色值較基質大且 色度較基質小，即可呼應到Stagnic colour pattern。
(二) 常見診斷層、特徵及物質和參考土類的內容 (按字母順序列出)
A. Acrisols (聚鋁土)
WRB對Acrisols的診斷索引 (Key to Acrisols) 如下 Soils have
1. an argic horizon that has a CEC (by 1 M NH4OAc) of less than 24 cmolc kg-1 clay in some part to a maximum depth of 50 cm below its upper limit, either starting within 100 cm of the soil surface, or within 200 cm of the soil surface if the argic horizon is overlain by loamy sand or coarser textures throughout, and
2. a base saturation (by 1 M NH4OAc) of less than 50 percent in the major part between 50 and 100 cm.
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B. Alisols (高活性聚鋁土)
WRB對Alisols的診斷索引 (Key to Alisols) 如下 Soils have
1. an argic horizon, which has a CEC (by 1 M NH4OAc) of 24 cmolc kg-1
1. an argic horizon, which has a CEC (by 1 M NH4OAc) of 24 cmolc kg-1