1. OM  humus 1º minerals  clays OM, clay, ions Transformations: runoff leaching Rain, OM capillary rise Four processes: Additions Losses Translocations Transformations

2. Influence of climate on Carbonate Layer Depth i.e., near surface Depth

3. Effect of Climate on Soil Formation limestone dry climate 40cm A R limestone wet climate 60cm A Bw Cr note depths of these profiles

4. T ppt

5. Organisms / Climate influences on soil formation Feb 18, 2002

6. Effect of Vegetation on SOM Grass/Agric Land Deciduous Forest Coniferous Forest Nutrient content of OM residue OM decomposition O horizon present High Low Rapid Slow NoSeasonalYes SOM = soil organic matter

8. Blocky structure Unweathered loess Organic matter CaCO 3 Time Grassland Time Temperate Deciduous Forest Organic layer Leached zone Unweathered bedrock Weathered PM Clays, oxides Effect of Vegetation on Development Soil Samples!

9. Time Temperate Deciduous Forest Organic layer Leached zone Unweathered bedrock Weathered PM Clays, oxides Effect of Vegetation on Development Ultisol Sample!

10. Blocky structure Unweathered loess Organic matter CaCO 3 Time Grassland Effect of Vegetation on Development Meadow Soil Sample!

11. Trinity Alps Wilderness Area Northern California Topography as an Influence on Soil Formation Relief Aspect Elevation (steep vs. flat) (N,S,E,W) (link to climate, organisms)

12. Landscape positions Figure 2.13 Brady & Weil Footslope Toeslope

13. Effect of topography on soil formation Summit Backslope Toeslope

14. Effect of Topography on Soils PositionSummitShoulderBackslopeFootslopeToeslope % OC in A horizon Thickness of A (cm) Texture of A 4.0 1.5 lowest 3.04.5 5.5 highest 15 6 lowest 1018 25 highest si ll si c l Most clay si c l Most clay E. Colorado; grassland; limestone pH7.0 7.2

15. Effect of time on soil development Very mature Mature Young Parent material 1m>1m15m C C AC A Bw C A E Bt

16. Effect of time on soil development

17. Modern floodplain Higher terraces 10cm 80cm Time A C A Bt1 C Bt2 both formed in alluvium from mixed sources similar topography

18. Effect of Time on Soils Soil age, development Immature (young) Mature (old) Mineral status Fertility Amount of clay Primary: quartz, feldspar, etc. Secondary: smectites, illite, etc. low high

19. Factors That Retard Soil Development Low rainfall and RH Cold temperatures High water table Parent materials that are mostly quartz Very high clay content Presence of substances toxic to plants Very steep slopes  erosion Disturbance frequency – e.g. fire

20. Soil Orders Study Guide Saved as a separate file on-line