Geology and the Evolution of American Forests Soil Taxonomy: Orders Suborders Great groups Subgroups Families Series Drummer – State soil of Illinois

Geology and the Evolution of American Forests Soil Orders All end in “sol” which is derived from “solum” meaning soil The twelve soil orders are: Alfisols, Aridisols, Entisols, Gelisols, Histosols, Inceptisols, Mollisols, Andisols, Spodosols, Ultisols, Vertisols and Oxisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols Maps and soil profiles NRCS

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols High pH High OM accumulation in upper horizons Areas of low rainfall Grasslands with scattered trees

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols Moderately high pH Some clay in B horizons Usually rich in mineral nutrients Areas of moderate rainfall with seasonal deficiencies

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols Very recent deposits or exposures of raw parent material No soil development yet Result of a variety of events (volcanoes, landslides, etc)

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols Organic soils on poorly aerated sites where water accumulates

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Acidic Result of strongly leached soils with subsurface accumulations of aluminum and iron Usually coarse-textured Recently deposited by effects of glaciation Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols Moist, well-drained (adequate supply of water) Effects of leaching have not yet led to subsurface accumulations of aluminum, iron, clay, or OM

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols Acidic Result of strong leaching in temperate climates causing subsurface accumulation of clay Moist affected by brief seasonal dryness

Geology and the Evolution of American Forests Soil orders where natural forests occur Mollisols Alfisols Entisols Histosols Spodosols Inceptisols Ultisols

Soils Geologic definition: Loose surface of the earth as distinguished from solid bedrock (support of plant life not required). Traditional definition: Material which nourishes and supports growing plants (includes rocks, water, snow, air). Component definition: Mixture of mineral matter, organic matter, water, and air.

Soils Soil is the outer portion of the Earth’s crust that supports plant growth …. It is the natural medium on the Earth’s surface in which plants grow …. It is composed of organic and mineral materials …. 50% of soil volume is: decomposed rock plant and animal remains pore spaces (occupied by either air or water)

Soils Major Components Minerals Organic matter Air Water Air 25% Mineral Matter 45% Water 25% Organic Matter 5%

Soils Engineering Geology Chemistry Plant Sciences Physics Significance of soil science in natural resources: 1) matching plant species to soil types 2) evaluation of limitations to resource management

Soils Functions of soil Offers mechanical support Retains and transmits water and gases Serves as a habitat for macro- and micro-organisms Holds, exchanges, and fixes nutrients

Soils Soil Formation Translocations Transformations Additions Losses NRCS photo

Soils Soil formation is initiated by the process of weathering Weathering – the physical or chemical disintegration and/or decomposition of rocks and minerals under natural conditions

Soils Physical weathering – breaking down parent material by exposure to physical forces Moving ice Moving water Wind Growing roots Chemical weathering – breaking down parent material by exposure to chemical forces Rainwater Surface water Gases Secretions by organisms

Soils As a portion of the landscape: Collection of natural bodies occupying portions of the earth’s surface that support plants and that have properties due to the integrated effect of climate and living matter, acting upon parent material, as conditioned by relief, over periods of time.

Soils Factors influencing soil development Parent material Climate Living organisms Topography Time

Soils Parent Material The unconsolidated and more or less chemically weathered mineral or organic matter from which the solum of soils is developed Solum-The upper and most weathered part of the soil profile; the A and B horizons

Soils Climate From an over-all standpoint, climate is perhaps the most influential factor affecting soil development Temperature and precipitation greatly influence the rates of chemical and physical weathering. Warm, wet, and flat areas have more rapid rates of soil formation than areas where the opposite conditions occur

Soils Living Organisms Living organisms influence soil development by providing organic matter, profile mixing, nutrient cycling and structural stability

Soils Topography Can speed up or slow down climatic forces

Soils Time The actual length of time that materials have been subjected to weathering plays a significant role in soil formation Soils of the glaciated region are much younger and more fertile then soils that were not glaciated

Soils Residual soils – soils that are formed “in place” Transported soils – soils formed by the transfer of loose sediments from one area to another area by Blowing wind Moving water Moving glacier landslides

Soils The detachment and movement of soil particles from one place to another Wind and water are the primary forces causing soil erosion Vegetative cover and roots help to keep the loss of soil in balance with topsoil replacement Wind erosion NRCS photo

Soils Soil erosion by water is categorized into four types: Splash Sheet Rill Gully

Soils Soil erosion by water is categorized into four types: Splash Sheet Rill Gully The spattering of small soil particles caused by the impact of raindrops on very wet soils

Soils Soil erosion by water is categorized into four types: Splash Sheet Rill Gully Occurs when a wide flow of water moves across a sloping field Recently tilled farmland with no vegetative cover

Soils Soil erosion by water is categorized into four types: Splash Sheet Rill Gully Results from water moving through small channels in the soil surface Farmland that is partially tilled with some vegetative residue Moderately overgrazed rangeland

Soils Soil erosion by water is categorized into four types: Splash Sheet Rill Gully Occurs where water is concentrated into a high velocity flow through a large channel that lacks vegetation NRCS photo

Soils Controlling Erosion The key to controlling erosion is to maintain a good vegetative cover Farming practices used to control erosion include: conservation tillage, strip cropping, contour farming, terracing, gully reclamation, windbreak planting, and the retirement of highly erodible lands from cultivation

Soils Strip Cropping NRCS photo

Soils Contour Farming NRCS photo

Soils Buffer Strip (gully reclamation) NRCS photo

Soils Windbreak Planting NRCS photo

Soils Tree Planting NRCS photo

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms Most abundant elements in the soil: O Si Al Fe Ca Na K Mg SiO2, Al2O3, Fe2O3, CaCO3

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms Macronutrients: C H from water and atmosphere O N P depleted K from inorganic Ca minerals in Mg the soil S

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms Micronutrients: Fe Mn Mo Zn from inorganic Cu minerals in the soil Cl B Co

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms Plant litter Animal and insect remains Feces OM serves as: reservoir for moisture temperature moderator barrier to water vapor diffusion home and food for microorganisms

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms Partially decomposed organic matter is called Humus Humus improves: soil water holding capacity soil ion-exchange capacity soil structure water infiltration aeration

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms Water holding capacity is the ability to retain water …. precipitation infiltration dissolved minerals plant uptake Infiltration rates depend on soil porosity Many spaces Few spaces poor water good water holding capacity holding capacity

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms Air is necessary for root respiration and gaseous exchange Pore spaces are either occupied by water or air Soils with high water holding capacity usually have poor aeration.

Soil Components Soil Components Inorganic minerals Organic matter Water Air Living organisms Living organisms mix, churn, aerate, and decompose soil and organic matter. bacteria earthworms fungi insects molds moles protozoa gophers mites ground squirrels nematodes badgers

Physical Properties of Soils Soil texture The individual mineral particles in a soil are classified into three texture size classes: Sand (.05-2.0 mm) Silt (.002-.05 mm) Clay (<.002 mm) The texture of a soil is then described as: The proportion in which particles of different size classes are found in the soil NRCS photo

Physical Properties of Soils

Physical Properties of Soils Soil structure The way soil particles clump together in larger lumps and clods are called ––– “Peds” ––– Peds are characterized on the basis of their - size - shape - degree of distinction

Factors that Affect Soil Structure Physical Properties of Soils Factors that Affect Soil Structure Kind of clay Amount of organic matter Freezing and thawing Wetting and drying Action of burrowing organisms Growth of root systems of plants All of these have a loosening effect on the soil, but they have no effect on aggregate stability

Aspects of Soil Structure Physical Properties of Soils Aspects of Soil Structure The arrangement into aggregates of desirable shape and size The stability of the aggregate The configuration of the pores

Aspects of Soil Structure Physical Properties of Soils Aspects of Soil Structure The arrangement into aggregates of desirable shape and size The stability of the aggregate The configuration of the pores NRCS photo

Aspects of Soil Structure Physical Properties of Soils Aspects of Soil Structure The arrangement into aggregates of desirable shape and size The stability of the aggregate The configuration of the pores Factors that affect aggregate stability - Kind of clay - Chemical elements associated with the clay - Nature of the products of decomposition or organic matter - Nature of the microbial population

Aspects of Soil Structure Physical Properties of Soils Aspects of Soil Structure The arrangement into aggregates of desirable shape and size The stability of the aggregate The configuration of the pores Effects of Bulk Density - Engineering properties - Water movement - Rooting depth of plants Bulk Density - Determined by dividing the weight of oven-dry soil in grams by its volume in cubic centimeters - The variation in bulk density is due largely to the difference in total pore space

Chemical Properties of Soils The chemical properties of soils are determined by: oxygen ( O2 ) water ( H2O ) mineral and nutrient content organic matter content pH degree of alkalinity or acidity depends on the concentration of H+ and OH- ions acidic neutral alkaline 0 7 14

Chemical Properties of Soils Water Holding Capacity The readily available soil water is considered to be the amount of moisture retained in the soil between field capacity (upper limit) and permanent wilting point (lower limit)

Relationship of Physical and Chemical Properties H2O H2O holding ion-exch texture infiltration capacity capacity aeration Sand good poor poor good Silt medium medium medium medium Clay poor good good poor Loam medium medium medium medium

Soil Horizons As soils develop, they form layers or horizons Each horizon has a distinctive thickness color texture composition Soil profiles are used to determine the properties of a soil to match species to the site to facilitate management

Soil Horizons Soil Color Indicator of different soil types Indicator of certain physical and chemical characteristics Due to humus content and chemical nature of the iron compounds present in the soil

Major Forms of Iron and Effect on Soil Color Soil Horizons Major Forms of Iron and Effect on Soil Color Form Chemical Formula Color Ferrous oxide FeO Gray Ferric oxide (Hematite) Fe2O3 Red Hydrated ferric oxide (Limonite) 2Fe2O3 3H2O Yellow

Soil Horizons NRCS photo NRCS photo

Ideal Soil Profile

Soil Profile under a Deciduous Forest

Soil Profile under a Coniferous Forest

Land Capability Classification Land Class Characteristics Primary Uses Secondary Uses Conservation I Excellent land flat, well-drained Agriculture Recreation Wildlife Pasture None II Good land minor limitations such as slight slope, sandy soil, or poor drainage Strip cropping Contour farming III Moderately good land important limitations of soil, slope, or drainage Watershed Urban Industry Waterways Terraces IV Fair land severe limitations of soil, slope, or drainage Orchards Limited agriculture Urban industry Limited contour farming

Land Capability Classification Land Class Characteristics Primary Uses Secondary Uses Conservation V Farming prevented by shallow soil, wetness, or slope. Slightly limited by rockiness Grazing Forestry Watershed Recreation Wildlife No special pre-cautions if properly grazed or logged; must not be plowed VI Moderate limitations for grazing and forestry Urban industry Grazing or logging limited at times VII Severe limitations for grazing and forestry Careful management required when used for grazing or forestry VIII Unsuitable for grazing or forestry due to steep slope, shallow soil, lack of water or too much water Not to be used for grazing or forestry