Taxonomy is a narrower term than classification. Classification includes taxonomy, but it also includes the grouping of soils according to limitations that affect specific practical purposes, such as the soil limitations affecting the foundations of buildings. Taxonomy is the part of classification that is concerned primarily with relationships.Our study focus on comparison between United State and Vietnam Soil Taxonomy, also aim to comprehend the classification systems in the both two nations.
VNU University of Science Wetland soil taxonomy in Vietnam and the US Instructor: Associated Professor Nguyen Thi Loan, Faculty of Environmental Science, VNU University of Science Group 1: Students: Do Thi Ngoc Bich - Phan Thi Thuy Dung Hoang Thi Giang - Tran Thu Trang - Trinh Thi Thu Trang Contents I Introduction Taxonomy is a narrower term than classification Classification includes taxonomy, but it also includes the grouping of soils according to limitations that affect specific practical purposes, such as the soil limitations affecting the foundations of buildings Taxonomy is the part of classification that is concerned primarily with relationships Our study focus on comparison between United State and Vietnam Soil Taxonomy, also aim to comprehend the classification systems in the both two nations II Study Methodology The knowledge we obtained and the document that we studied was from monograph books, science reports from US Department of Agriculture/ Department of Land Management, articles and other references… III Results and Discussion Comparison of soil taxonomy in VN and US 1.1 The US Soil Taxonomy: There are categories in the US soil taxonomy: 2|Group Wetland soil taxonomy Order (12 orders): This category is based largely on soil forming processes as indicated by the presence or absence of major diagnostic horizons A given order includes soils whose properties suggest that they are not dissimilar in their genesis They are thought to have been formed by the same general genetic processes Suborder (63 suborders): Suborders are subdivisions of orders that emphasize gentic homogeneity The presence or absence of properties associated with wetness, climatic environment, major parent material, and vegetation Great Group (319 great groups): Great groups are subdivisions of suborders according to similar kind, arrangement, and diagnostic horizons The emphasis is on the presence or absence of specific diagnostic features, base status, soil temperature, and soil moisture regimes Subgroup (2484 subgroups) Subgroups are subdivisions of the great groups The central concept of a great group makes up one group (Typic) Other subgroups may have characteristics that are intergrades between those of the central concept and those of the orders, suborders, or great groups Extra gradation is used to identify critical properties common in soils in several orders, suborders, and great groups Family (8000 families): Families are sound in soils with a subgroup having similar physical and chemical properties affecting their response to management and especially to the penetration of plant roots Differences in texture, mineralogy, temperature, and soil depth are bases for family differentiation Series (approximate 19000 series in the U.S.): Its differentiating characteristics are based primarily on the kind an arrangement of horizons, color, texture, structure, consistence, reaction of horizons, chemical, and mineralogical properties of the horizons Phases: Based on these differences are detailed mechanical components, surface, erosion rate, slope, or some other characteristic 1.1 The classification of soil in Vietnam In Vietnam taxonomy, we divided soil into Order => Suborder => Group 3|Group Wetland soil taxonomy At the level of order, soil classification has only 13 orders The basic of Vietnam soil classification is composition characteristic 1.2 Comparison between Soil taxonomy categories in VN and in the US: - VN classify soil in categories while in US taxonomy, there are categories Vietnam soil taxonomy is mainly based on composition characteristic of soil while in the US taxonomy, in each categories, they based on many other 1.3 criteria Reasons for the differences: • US taxonomy establishment: Implemented long time ago with big budget and many experts Consult: self-established Scale: whole territory • Vietnam taxonomy establishment: Newly implemented Consult: from three giant taxonomy systems: Xoviet Union’s, FAO’s, US Scale: small area or provinces Wetland soil in the US taxonomy and Vietnam taxonomy: In both two systems, we can find wetland in the areas of Histosols order and some other orders The orders with yellow marks indicates order that ave wetland areas US Vietnam Alfisol Arenoslos Andisol Solonchaks Aridisol Thionic Fluviols Entisol Fluvisols Gelisol Gleysols 4|Group Wetland soil taxonomy Histosol Histosols Inceptisol Acrisols Mollisol Leptosols Oxisol Podzoluvisols Spodosol Luvisols Ultisol Ferralsols Vertisol Lixisols Alisols 2.1 Histosols Histosols are organic soils produced by the deposition and accumulation of dead plant remains The central concept of Histosols is that of soils forming in organic soil materials, that formed almost exclusively in wetlands, whereas the other orders are mineral soils The root element "histos" was used to indicate that these soils are composed largely of plant tissue (at least 20-30% in most of upper parts, Soil Survey Staff 1975, p 72) They are essentially the Peat, Bog, Half Bog, and Muck soils of classifications Obviously, the preservation of organic matter in these soils is associated with the predominance of saturated conditions These soils are of biogenic origin (along with marls) and are the most fertile soils worldwide Histosols form only under conditions of continuous to near continuous saturation or waterlogging The general rule is that a soil without permafrost is classified as a Histosol if half or more of the upper 80 cm is organic Having organic soil materials that meet one or more of the following: a Overlie cindery, fragmental, or pumiceous materials and/or fill their interstices and directly below these materials have either a densic, lithic, or paralithic contact; or 5|Group Wetland soil taxonomy b When added with the underlying cindery, fragmental, or pumiceous materials, total 40 cm or more between the soil surface and a depth of 50 cm; or c Constitute two-thirds or more of the total thickness of the soil to a densic, lithic, or paralithic contact and have no mineral horizons or have mineral horizons with a total thickness of 10 cm or less; or d Are saturated with water for 30 or more cumulative days during normal years (or are artificially drained), have an upper boundary within 40 cm of the soil surface, and have a total thickness of either: (1) 60 cm or more if three-fourths or more of their volume consists of moss fibers or if their bulk density, moist, is less than 0.1 g/cm3; or (2) 40 cm or more if they consist either of sapric or hemic materials, or of fibric materials with less than three-fourths (by volume) moss fibers and a bulk density, moist, of 0.1 g/cm3 or more Other Histosols that have more thickness of sapric soil materials than any other kind of organic soil materials either: In the organic parts of the subsurface tier if there is no continuous mineral layer 40 cm or more thick that has its upper boundary within the subsurface tier; or In the combined thickness of the organic parts of the surface and subsurface tiers if there is a continuous mineral layer 40 cm or more thick that has its upper boundary within the subsurface tier Histosols in US are divided into suborders: Folists, Wassists, Fibrists, Saprists, and Hemists Folists(“free drained” histosols’ found in cool mountainous regions): Histosols that are not saturated with water for long periods of time during the year Wassists: Histosols that are submerged for more than 21 hours every day 6|Group Wetland soil taxonomy Fibrists(fibers compose >2/3 of the mass; Sphagnum bogs): Histosols that are primarily made up of only slightly decomposed organic materials, often called peat Saprists(fibers compose 50 cm Thionic histosols is flooded 40-50cm in rain season lasting 5-6 months/year with pH (water) equals to 5.4 and clay percentage is 17.7% 7|Group Wetland soil taxonomy Figure 2: A tidal marsh Histosol The inset shows the fibric (peaty) organic material that contains recognizable roots and rhizomes of marsh grasses that died perhaps centuries ago, the anaerobic conditions having preserved the tissues from extensive decay The soil core (held horizontally for the photograph) gives some idea of the soil profile, the surface layer being at the right and the deepest layer at the left The water level is usually at or possibly above the soil surface (Photos courtesy of R Weil) 2.2 Comparisons of histosol in Vietnam and the U.S 2.2.1 Similarrities: Histosols soil in VN and US have some similarities: • • • Histosols are soils forming in organic soil materials Properties: they are rich in organic matter and the accumulation of peat Distribution in the wet and low-lying areas 8|Group Wetland soil taxonomy 2.2.2 Differences: • In US, wetland soil appears in two suborders: Hemists and Saprists: 1) Hemists Hemists are the Histosols that: Are saturated with water for 30 or more cumulative days during normal years (unless artificially drained); Do not have more thickness of fibric soil materials and not have more thickness of sapric soil materials than any other kind of organic soil material either In the organic parts of the subsurface tier if there is no continuous mineral layer 40 cm or more thick that has its upper boundary within the subsurface tier; Have a sulfuric horizon that has its upper boundary within 50 cm of the soil surface, or sulfidic materials within 100 cm of the soil surface These are wet Histosols in which the organic materials are moderately decomposed The botanic origin of much of the organic material cannot be readily determined The fiber content of much of the organic material is between onesixth and two-thirds after rubbing between the thumb and fingers The bulk density commonly is between 0.1 and 0.2 g/cm3 Ground water is at or very close to the surface of these soils much of the time unless artificial drainage has been provided The level of ground water may fluctuate but seldom drops much below the bottom of the surface tier Hemists occur from the Equator to latitudes with a cryic temperature regime, that means soils in this temperature regime have a mean annual temperature higher than 0°C but lower than 8°C They are in closed depressions and in broad flat areas, such as coastal plains and outwash plains Most Hemists are under natural vegetation and are used as woodland, rangeland, or wildlife habitat Some large areas of Hemists are cleared, drained, and used as cropland 2/ Saprists Saprists are the Histosols that: 9|Group Wetland soil taxonomy Are saturated with water for 30 or more cumulative days during normal years (unless artificially drained); and Have more thickness of sapric soil materials than any other kind of organic soil materials either These are the wet Histosols in which the organic materials are well decomposed The botanic origin of the organic material is difficult to determine in most of these soils The fiber content is less than one-sixth after rubbing between the thumb and fingers Most of these soils have a bulk density of more than 0.2 g/cm3 Saprists occur in areas where the ground water table tend to fluctuate within the soils or in areas where the soils were aerobic during drier periods in the past They consist of the residue that remains after the aerobic decomposition of organic matter When drained, fibric and hemic materials commonly decompose to form sapric materials If the organic materials are deep and are drained either artificially or naturally, the Fibrists and Hemists are converted after some decades to Saprists 3/ Comparison: Now we come to compare suborders of histosols order The reason to compare suborders is that these suborders have a similar capability of decomposing organic material Table 1: Comparision of wetland soil in US and Vietnam Properties OM Hemists (US) decompositio Moderately decomposed n Time residue Profile 30 days/year or more - Mineral layer: 0-40 cm Thionic (Vietnam) Moderately decomposed Mainly Melaleuca (câytràm) 5-6 months/year -Half-decomposed dead plant: 0- 30cm - Sulfuric horizon: 40-100 - Peat and dead plant layer: 30cm 10 | G r o u p W e t l a n d s o i l t a x o n o m y 100 cm - Alum accumulation Clay layer: 100-150 cm Cryic temperature regime Forming condition Ex: Minesota, Alaska Low-lying areas vegetation thrive Ex: U Minh where Thuong (KienGiang) national park and VồDơi Nature reserve (Ca Mau) 2.3 Other oders in US taxonomy and VN taxonomy that have wetland 2.3.1 In the US: Another order that contains wetland: Order Alfisols - Suborder Aqualfs - Great Groups JAJ Epiaqualfs They have episaturation condition: The soil is saturated with water in one or more layers within 200 cm of the mineral soil surface and also has one or more unsaturated layers with an upper boundary above 200 cm depth, below the saturated layer(s) 1) Epiaqualfs a Have episaturation and a frigid, mesic, isomesic, or warmer temperature regime; b Do not have a glossic, kandic, or natric horizon or a duripan; c Do not have a fragipan with an upper boundary within 100 cm of the mineral soil surface; d Do not have an abrupt textural change between the albic and argillic horizons if the saturated hydraulic conductivity of the argillic horizon is moderately low or lower; 11 | G r o u p W e t l a n d s o i l t a x o n o m y e Do not have one or more layers, at least 25 cm thick (cumulative) within 100 cm of the mineral soil surface, that have 50 percent or more (by volume) recognizable bioturbation, such as filled animal burrows, wormholes, or casts; and f Have, in all horizons at a depth between 30 and 150 cm from the mineral soil surface, less than 50 percent (by volume) plinthite Typic Epiaqualfs are the Epiaqualfs that: a Do not have, in any horizons between the A or Ap horizon and a depth of 75 cm below the mineral soil surface, in 50 percent or more of the matrix, one or a combination of the following: either • Hue of 7.5YR or redder; and (1) If peds are present, either chroma of or more on 50 percent or more of s or no redox depletions with chroma of or less in ped interiors; or (2) If peds are absent, chroma of or more in 50 percent or more of the matrix; • Hue of 10YR or yellower and: (1) Both a color value of or more (moist) and chroma of or more (moist and dry); or (2) Chroma of or more (both moist and dry) and no redox concentrations; b Do not have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, any of the following: • A fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling more than 1.0 12 | G r o u p W e t l a n d s o i l t a x o n o m y • More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumice like fragments • A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and (1) In the 0.02 to 2.0 mm fraction, percent or more volcanic glass; (2) [(Al plus 1/2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more; c Do not have a mollic or umbric epipedon, an Ap horizon that meets all of the requirements for a mollic or umbric epipedon except thickness, or materials between the mineral soil surface and a depth of 18 cm that meet these requirements after mixing; d Do not have a sandy or sandy-skeletal particle-size class throughout a layer extending from the mineral soil surface to the top of an argillic horizon at a depth of 50 cm or more; e Do not have either: • Cracks within 125 cm of the mineral soil surface that are mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface; or • A linear extensibility of 6.0 cm or more between the mineral soil surface and either a depth of 100 cm or a densic, lithic, or paralithic contact, whichever is shallower; and 13 | G r o u p W e t l a n d s o i l t a x o n o m y f Have fragic soil properties: • In less than 30 percent of the volume of all layers 15 cm or more thick that have an upper boundary within 100 cm of the mineral soil surface; and • In less than 60 percent of the volume of all layers 15 cm or more thick 2.3.2 In Việt Nam Other orders that contain wetland soil are: solonchaks, Thionic Fluvisols, and Fluvisols 1) Solonchaks a Gleyic Solonchaks • Area of 105 318 ha, accounted for 0:34% natural area and 10.63% nationally saline group’s area • Distribution: in many coastal areas from South to North, but most are in the southern coastal areas of Ca Mau and Ben Tre • Soil is slurry, muddy tidal wetland, saturated NaCl, strong Glay, neutral or alkaline soil The average amount of nitrogen is fair, average amount of phosphorus and total amount of potassium are rich, easily digestible phosphorus and potassium are pretty and rich, the ratio Ca ++ /Mg ++ is usually smaller than • Equivalent name in soil taxonomy: Epiaquents b Haplic Solonchaks 14 | G r o u p W e t l a n d s o i l t a x o n o m y • Area: 133 288 hectares, occupied 0:42% natural are and 15% of the country's saline group, and largely concentrated in the coastal plain Mekong river: 102,000 hectares • Distribution: saline lowland or coastal estuaries • Haplic Solonchaks due to soil salinity saltwater, tidal overflow, or by artesian waters which are affected by sodium chloride salt in seawater Amount of Cl- > 0.25%, total amount of soluble salts > 1%, the ratio Ca++/ Mg++ usually smaller than Mechanical components: from clay or loam to clay limon • Equivalent name in taxonomy name: hydraquents c Molli salic Fluvisols • Area: 732,584 hectares, occupied 2.4% total natural area, and 75% of saline group’s area, mostly distributed in Mekong river delta • Distribution: adjacent alluvial soils, inside haplic soils, • The majority topographies are medium and high terrain, and also be affected by the tide The amount of Cl- < 0.25%, the ratio Ca++/Mg++ [...]... park and VồDơi Nature reserve (Ca Mau) 2.3 Other oders in US taxonomy and VN taxonomy that have wetland 2.3.1 In the US: Another order that contains wetland: Order Alfisols - Suborder Aqualfs - Great Groups JAJ Epiaqualfs They have episaturation condition: The soil is saturated with water in one or more layers within 200 cm of the mineral soil surface and also has one or more unsaturated layers with... coastal areas of Ca Mau and Ben Tre • Soil is slurry, muddy tidal wetland, saturated NaCl, strong Glay, neutral or alkaline soil The average amount of nitrogen is fair, average amount of phosphorus and total amount of potassium are rich, easily digestible phosphorus and potassium are pretty and rich, the ratio Ca ++ /Mg ++ is usually smaller than 1 • Equivalent name in soil taxonomy: Epiaquents b Haplic Solonchaks... mostly distributed in Mekong river delta • Distribution: adjacent alluvial soils, inside haplic soils, • The majority topographies are medium and high terrain, and also be affected by the tide The amount of Cl- < 0.25%, the ratio Ca++/Mg++