1. is a combination of: rock and mineral fragments organisms (such as plants, animals, fungi, bacteria, etc.) organic matter water and air Soils are a complex part of the ecosystem and contain layers with varying physical, chemical and biological properties. Soil organisms 1 Dr. Darlene Zabowski School of Forest Resources

2. For Plants: water, aeration, nutrients, anchorage (and root symbionts) For Ecosystems and Society in general: food habitat clean water (soils filter water) structural/building materials wood/fiber/energy

3. Western WA forest soil Central China soil 3

4. A very young floodplain soil from western Washington used to grow cabbages old fire 4

5. A very old tropical soil from Puerto Rico farmed for pineapple 5

6. Subalpine forest soil

7. An example of a cross section of a soil showing a soil profile that includes possible soil horizons. Actual soil profiles will vary in the number and type of horizons that are present. 7

8. O A B C A A B Western WA forest soil Central China soil 8

9. A very young floodplain soil from western Washington used to grow cabbages A C C 9

10. Subalpine forest soil O BC Bs Bh E

11. Physical properties of importance aggregation infiltration rate texture (sand, silt and clay) rock and gravel content abrupt textural changes bulk density BD = mass dry soil/ volume Typical range is 0.8 to 1.2 g cm -3 hydrophobicity moisture regime temperature regime color (OM, Fe, wetness) soil depth

12. Chemical properties of importance pH (measure of acidity and alkalinity—forest soils naturally acidic) Organic matter content ( Is an O horizon present? Is there an A horizon? OM content varies by soil type and decreases with depth in mineral soil). What affects OM accumulation? Decomposition is faster when oxygen is present. Nitrogen (in young soils, often the most limiting nutrient) Total and available nutrient content Cation Exchange Capacity (available nutrient storage capacity of a soil) clays, OM and oxides provide CEC Base Saturation % of storage sites filled with certain nutrients (Ca, Mg, K, Na) Trace metal content Carbonates Oxidizing/Reducing conditions

13. Soil ecology Decomposers for OM breakdown and cycling Root symbionts (mycorrhizae and N fixers) Is there abundant micro and macro flora and fauna? Root pathogens? Are there changes in species in urban areas? Carabus nemoralis Ground beetle Lumbricus terrestris Nightcrawler

14. Natural and Disturbed Alderwood Soil Examples of a natural soil with its urban counterpart

15. Natural and Disturbed Everett Soil Examples of a natural soil with its urban counterpart

16. Natural and Disturbed Valley bottom Soil Examples of a natural soil with its urban counterpart

17. Examples of some urban soils

18. Common differences observed in urban soils compared to natural soils: 1. mixing – loss of horizons 2. new parent materials 3. high spatial diversity 4. abrupt textural changes 5. crusts 6. contaminants 7.more exposed mineral soil 8.bulk density Craul, 1992

19. Problems frequently encountered in urban soils 1. Abrupt textural changes—potential for waterlogging, root restriction, erosion (often occurs when topsoil is brought in) 2. pH too high or too low 3. Poor nutrient availability 4. Contaminants (waste, pollutants)

20. (White and McDonnell, 1988)

21. Problems frequently encountered in urban soils 1. Abrupt textural changes—potential for waterlogging, root restriction, erosion (often occurs when topsoil is brought in) 2. pH too high or too low 3. Poor nutrient availability 4. Contaminants (waste, pollutants) Potential causes for reduced N availability: 1. Hydrophobic -- 'urban grime' hydrocarbons 2. Heavy metals, pH 3. Soil ecology -- trampling, metals, ?

22. Problems frequently encountered in urban soils 1. Abrupt textural changes—potential for waterlogging, root restriction, erosion (often occurs when topsoil is brought in) 2. pH too high or too low 3. Poor nutrient availability 4. Contaminants (waste, pollutants) 5. Altered moisture regime 6. Altered temperature regime 7. Over fertilizing, salts

23. 8. Exposed mineral soil, compaction, runoff…. from loss of understory

25. 9. Loss of topsoil: poor nutrient availability, potential for further erosion

26. 10. High Spatial Variability

27. 11. Crust: Development of a compacted crust with plugged pores – water infiltration and gas exchange will be limited, runoff increased 12. Compaction: General compaction increasing soil density— possibly restricting root growth

28. An urban soil from the UW campus showing compaction, deposition of new material, abrupt texture change, mixing, and contamination

29. This site has potential problems of: compaction, abrupt textural changes, contamination, low nutrient availability

30. Mixed soil, and not necessarily good soil, but may not have any special problems

31. More soils information: http://soils.usda.gov/ soil surveys, capability classes, profile descriptions etc. (limited urban information available!)