Cover of N C Agric Res Bull 467

Cover of N. C. Agric. Res. Bull. 467 Understanding Soil Formation

Hans Jenny (1899 - 1992) Mendocino Staircase

http: //static. panoramio. com/photos/original/1006030. jpg

Pygmy forest . The highest and oldest Extremely of five wave-cut acid terraces thatand rise from the chilly waters of the infertile Pacific Ocean. soil The Hans Jenny Pygmy Forest Reserve In this complex “ecological staircase, ” each terrace is ~ 100, 000 years older than the one below it and supports a distinct association of soils, plants, animals and microbes. Giant trees Beach sand

How is it possible that soil can naturally become so unproductive?

Where is Macomb in this sequence? Dr. Jenny also studied climosequences across the Great Plains. Brady and Weil, 20

H Jenny refined the ideas of Russian scientist VV Dokuchaev into the following equation: Soil = f (Cl, O, R, P, T…) lim ria l of soil formation e ate m Ti nt m re Pa f ie s el m R is an rg O ate C 5 factors

Climate Organisms Which factor is most important ? ? ? Young Older Soils Parent material Topography

Understanding parent materials in Illinois Glacial deposits cover most of Illinois Many of these deposits are hundreds of feet thick!

Retreating Glacier

Depth of loess cap LOESS silt sized glacial flour, transported by wind, deposited near rivers

Glaciation Primary minerals physical weathering chemical alteration weathering chemical dissolution weathering n atio t i p i rec p K+ HCO 3 - Ca+2 Cl -2 Na+ SO 4 ng secondary clay minerals chi ions in solution lea sand silt

Climatic variation Increasing temperature Increas ing rain fall RR Weil

Average annual precipitation in IL 1951 -1990 Have precipitation levels remained constant during the last 10, 000 years ? NO !

N. C. Agric. Res. Bull. 467 Topographic variation Poorly drained Somewhat poorly drained Interstream divide Moderately well drained Well drained Common in IL SOIL DRAINAGE CLASSES LANDSCAPE POSITIONS Poorly drained Shoulder Valley floor Backslope

Soil Associations in Mc. Donough County, Topography of Mc. Donough County, IL IL 800 feet above sea level A soil association is a group of soils that are found together in a landscape 470 feet above sea level

Vegetative variation Grassland Forest Organic- rich A horizon From Brady and Weil, 2002

How much of Illinois was originally covered by tallbygrass forest prairie ? ? 13. 8 millionacres 22 million Illinois once was covered by a complex mix of prairie and forest Old growth Prairie dominated in theforest flat expanses Forest dominated the hilly land Corn and soybean dominate IL landscapes today but we know where the prairie and forest use to be because of the soils

Lake terrace chronosequence in northeastern Michigan http: //soils. umn. edu/academics/classes/soil 2125/doc/s 4 chp 4. htm Temporal variation

Young Soil in NC Poorly Defined Horizons Low Degree of Weathering Slightly Leached Thin Solum http: //www. mo 15. nrcs. usda. gov/features/gallery/ Old Soil in NC Well Defined Horizons High Degree of Weathering Highly Leached Thick Solum

Additions Precipitation plus solutes, aerosols and particulates Sedd A dim iteionn s Soil forming processes SLeod simsee NS nst TR AN SL OC A TIO Capillary rise of dissolved ions AN SL OC AT IO NS E(i)lluviation humus Organic residues NS of TIO Ada ry FO ec. Mon SR RA ar. Ny. S Tm Pri clay minerals Ca. CO 3 dissolved ions dissolved OM Losses Leaching of dissolved ions & OM Additions TR t s ses a f gse. CO 2 o s 2 O, sso. N o L L 2, N Capillary rise of salts Adapted from Stewart (1990)

Water driven translocations Eluviation Illuviation http: //www. uwsp. edu/geo/faculty/ritter/geog 101/textbook/soil_systems/soil_development_profiles. html

Typical Florida flatwoods soil Eluviation = depletion Illuviation = accumulation http: //www. fnps. org/photos/spodosol. jpg

Conceptual chronosequence http: //courses. soil. ncsu. edu/resources/soil_classification_genesis/soil_formation/soil_transform. swf

Chronosequence in California Foth, 8 th ed.

Characteristics that differentiate soil horizons Color Texture Density Structure Organic Matter content Acidity Mineral Accumulations Biological activity RR Weil

Most Weathered Master Soil Horizons Soil horizons Least weathered RR Weil