NREM 301 Day 9 • Quiz on Thursday! • Continue discussing sequences (focusing on central IA) • Discuss Soil Taxonomy and major soil orders • Lab Today – “Identifying Soil Bio- and Toposequences” – Individual Assignment – due Thurs. Oct. 2. Soil Definition for Soil • A Natural Body • Unconsolidated Mixture • Mineral & Organic Matter • Living & Dead • Developing in Place Over Time Dirt So - soils vary dramatically spatially & temporally Because of: Soil = f(Cli, p, r, o, t) Cli = climate P = parent material R = relief O = organisms T = time High elevation – cold Soil = f(Cli, p, r, o, t) Cli = Climate What Soil Differences Would 5,000 ft – warm, humid You Expect? Why? Granite Glacial Till Soil = f(Cli, p, r, o, t) P = Parent Material What Soil Differences Would You Expect? Why? Soil Parent Materials – the raw mineral material soils are developing in. Rocks and Minerals Deposited in oceans -marine sediment Deposited in lakes ----lacustrine sediment Deposited in streams -alluvium – floodplain, delta terrace, fan ice Deposited by ice ----glacial till --- moraines transport Deposited by water --outwash – alluvium, marine lacustrine Deposited by wind - eolian --- loess, eolian sand, Residual sediment volcanic ash parent material (bedrock weathered Deposited by gravity –colluvium – creep, landslides in place) types of examples of deposits landforms or deposits Modified from Brady and Weil. 2002. The nature and properties of soils. 13th edition. Prentice Hall. N or E facing S or W facing Soil = f(Cli, p, r, o, t) r = Relief/Topography What Soil Differences Would You Expect? Why? What soils would you expect at each location? Summit (linear) Shoulder (convex) Lester Soil Depth Hayden Backslope (linear) Ice Transported Glacial Till Storden Residual Bedrock Footslope(concave) Toeslope (linear) Terril Colluvial Coland Alluvial Spillville Soils – Parent Material – Topography in Central Iowa Hillslope Soils – Hayden-Lester-Storden Association Parent Materials – Glacial Till, Storden 62 – back slope, shallow Bedrock, Colluvium, Alluvium loam, well-drained, formed under Hayden 168 – shoulder, upper back forest slope, well-drained loam, formed Terril 27 – foot slope, well-drained under forest loam, formed under forest Lester 236 – summit, shoulder, well- Coland 135 – foot slope, poorly drained drained, loam, formed under savanna Clay loam along small creeks vegetation Flood Plain Soils Along the Skunk River Coland-Spillville-Zook Soil Association Flood Plain- Toe Slope Spillville 485 – black loam, moderately well drained Coland 135 – black clay loam, poorly drained Zook 54 – black silty clay loam, poorly drained Parent Material – Hanlon 536 (1314) – natural levee, sandy loam Alluvium Wadena & Biscay - minor soils Upland Soils – Clarion-Webster-Nicollet Association Note: Parent materials – glacial till or local alluvium Upland depressional soil sequence from center out – Okoboji 6, Harps 95, Canisteo 507 Webster 107 - depressional, non-circular soil Best drained soils – Clarion 138 & Storden 62 but Storden is eroded Nicollet – somewhat poorly drained Soil Landscape Model for Central Iowa Hayden-Lester-Storden Association Clarion-Webster-Nicollet Association Coland-Spillville-Zook Association Prairie Soil = f(Cli, p, r, o, t) o = Organisms What Soil Differences Would Forest You Expect? Why? 75 -80-% Above Ground 20-25% Above Ground 20-25% Below Ground 75-80% Below Ground Approximate Lester - Depth (cm) developed in deciduous forest 20 – prairie transition 40 ecotone (savanna) 60 vs Hayden 80 Thicker A Thinner, less developed E 100 120 Source: Sandor Depth (cm) Pit 4 20 Hayden - developed 40 under deciduous forest in Des 60 Moines Lobe till. 80 Vs Lester Thinner A 100 Thicker E 120 Source: Aandahl 1982 Prairie Forest Do Prairie & Forest Soils have the same horizons with the same depths? - NO Why Are There These Differences? Young Iowa Soil = f(Cli, p, r, o, t) t = Time What Soil Old Appalachia Differences Would You Expect? Why? Time & Horizon Development Time Soil Classification • Soil Taxonomy – Just like plant and animal taxonomy, it’s how we name soils – Different areas of the world use different naming schemes – the U.S. scheme is the one we will discuss Basic Structure of Soil Taxonomy and other Hierarchical Classifications Source: Sandor Categories and Classes of Soil Taxonomy Category Number of Classes (as of 2002) Order 12 Suborder 64 Great Group 317 Subgroup 2,435 Family 8,062+ Series ~22,000 Source: USDA- NRCS; Sandor Differentiating Characteristics in Soil Taxonomy Differentiating Characteristics – the criteria by which soils are grouped into different classes. Some major kinds in Soil Taxonomy are: • Diagnostic Horizons • Diagnostic surface horizons (epipedons) • Diagnostic subsurface horizons • Soil Moisture and Temperature Regimes • Special chemical or mineral properties Soil Formation Through Time How do Soils Form and Change through Time? C AC A Bw C A E Bt C A E1 E2 Bt1 Bt2 C Parent Entisol Inceptisol Alfisol Ultisol Oxisol Material Mollisol 0 Time Line Thousands of Years Trends with time and soil formation: • Soils become increasingly differentiated into layers. They develop more kinds and numbers of horizons. • With horizon development, soils deepen with time. Soil Map of the World Soil Map of the U.S. and Canada U.S. Soil Orders Map Source: http://www.nrcs.usda.gov/technical/land/meta/m4025.html Scheme for Learning the 12 Soil Orders of Soil Taxonomy Soils Mineral Soils Organic Soils Histosols Some Gelisols Soils without well-developed profiles or Mostly developed soils with diagnostic horizons or characteristics soils that reflect special parent material associated with certain climate-vegetation zones Entisols Inceptisols Vertisols Andisols Aridisols Mollisols Alfisols Ultisols Oxisols Spodosols Gelisols Key Un- Incipient Clay Volcanic Arid Grasslands; Deciduous forest; Forest veg.; Tropical Acidic Cold Factors developed development (shrink- ash climate temperate savanna veg.; strongly climate; vegetation; climate; soil swell) climate temperate climate weathered extremely humid permafrost acid soil weathered climate; soil sandy Genetic no B Bw varies varies some B thick A Bt Bt Bo Bhs varies Horizons (AC) Diagnostic ochric cambic varies varies • ochric mollic • ochric • ochric oxic spodic • histic Horizons • some • argillic • argillic common; subsurface • high in or kandic • gelic horizon bases • low in bases materials Source: Sandor Entisols • Young soils • A and C horizons only • Found in areas with lots of disturbance Typic Ustifluvent, Wisconsin River floodplain Source: Soil Science Society of America. 1968 The Marbut Memorial Slide Collection Inceptisols • Are more weathered than Entisols • Contain a weak B horizon (Bw) Inceptisol Source: Soil Science Society of America. Typic Eutrudept, Michigan 1968 The Marbut Memorial Slide Collection Mollisols Mollisols • Thick, dark A horizon • Grassland soils (usually) • Can have clay accumulation in B horizon (Bt) - but not always) • Very fertile (high base saturation) Typic Argiudoll, Iowa (Tama series) Source: Soil Science Society of America. 1968 The Marbut Memorial Slide Collection Alfisols Typic Hapludalf ~ Hayden Alfisols • Usually have thin gray to brown surface horizons • Medium to high base saturation (= fertility) • Accumulation of silicate clay in the B horizon. • More strongly weathered than Inceptisols, but less strongly weathered than Spodosols. Source: Soil Science Society of America. Hapludalf, Michigan 1968 The Marbut Memorial Slide Collection Spodosols • Have a strongly developed E horizon • Humus (a type of organic matter) plus Fe and Al oxides accumulate in B horizon • Form under coniferous forests that have coarse parent material Spodosol, New York Source: Soil Science Society of America. 1968 The Marbut Memorial Slide Collection Spodosol in hemlock, New York Source: Sandor Example of how to decipher a soil taxonomic name: Series = Clarion Map Unit = 138 Source: Sandor Ultisols • More weathered than Alfisols • Accumulation of silicate clay in the B horizon • Low base saturation (low fertility) • Found on old landscapes in warm, humid climates Typic Kandiudult, North Carolina Source: Soil Science Society of America. 1968 The Marbut Memorial Slide Collection Ultisol Humult, Oregon Source: Sandor Oxisols • Highly weathered (more than Ultisols) • Found in the tropics and subtropics • Most clays have been weathered to Fe and Al oxides • Very deep (10-20 meters) Eutrudox, Puerto Rico Source: Soil Science Society of America. 1968 The Marbut Memorial Slide Collection Oxisol - Kandiustox, Thailand Source: Sandor Weathered soil landscape, Thailand Source: Sandor Histosols • Contain > 20% organic matter • Generally form in saturated areas marl Limnic Udisaprist, Michigan Source: Soil Science Society of America. 1968 The Marbut Memorial Slide Collection Floating Histosol-Strawberry Bog, northern Minnesota Source: Sandor Histosol, spaghnum and black spruce, Minnesota Source: Sandor Histosol, southeast Alaska Source: Chad Allen Lab Today – Reactor Woods – site of the soil pits Identify and describe soil bio- and topo-sequences (logical orders of soils that are different because of position in the landscape) Remember you have an assignment due from this lab Depth (cm) Bio-sequence - forest 20 member. Hayden - developed 40 under deciduous forest in Des Moines Lobe till. 60 80 100 120 Source: Aandahl 1982 Approximate Depth (cm) Bio-sequence - Savanna Member 20 Lester - developed in 40 deciduous forest – prairie 60 transition ecotone (savanna) 80 100 120 Source: Sandor