1. The Living Earth
Chapter 15

2. Where does soil come from?
Rocks
Minerals
Organic Matter

3. Ecological definition of soil
Soil is a mixture of mineral particles, organic matter, water, and air that is capable of supporting plant life

4. a vertical section of soil from the ground surface to the parent rock
What is a Soil Profile?
a vertical section of soil from the ground surface to the parent rock

5. Bedrock Igneous, metamorphic and sedimentary rock of the lithosphere
Bedrock is the parent rock
For soil (as it breaks down)
Pavement is the bedrock
of the desert

8. How are climate and soil thickness related?

9. Sagebrush-Cold Desert
Mollisol Profile
Profile is only a few cm thick due to lack of water to break down the bedrock

10. Desert Varnish—leaching of minerals and flowing over rocks

11. Permafrost

12. What are the main components of soil?
Mineral Matter
Air
Water
Organic Matter

13. Mineral component
• Anchorage for plant roots. • Pore space for water and air. • Source of many plant nutrients through weathering. • Exchange sites for plant nutrients.

14. Organic component
• Source and exchange site for nutrient cycling. • Influences soil structure, pore space, and water holding capacity. • Energy source for soil microbes and other heterotrophs.

15. Water component
• Solvent for many essential plant nutrients. • Maintains equilibrium between cation and and anions that are held on exchange sites.

16. Air component
• Contains O2 for aerobic metabolism of plant roots and soil organisms. • Exchange of CO2 from soil respiration and which facilitates weathering. • Provides N2 for N-fixing soil organisms.

17. Why are soils so crucial to ecological studies?
• They provide all or part of all essential factors for plant growth except light. • Rooting material for the plants: the platform on which trophic levels of the ecosystem are built. • Contains most of the decomposers that recycle energy and nutrients of the ecosystem. • Contain the history of the site, which can be interpreted through paleoecological reconstructions. • The soil is an ecosystem in itself (producers, consumers, and decomposers

18. What are the FACTORS that make SOIL? TIME LAY OF THE LAND
1000’S TO 10,000’S OF YEARS
LAY OF THE LAND
TOPOGRAPHY
LIVING ORGANISMS
ANIMALS AND PLANTS
CLIMATE
HOT/COLD, WIND/RAIN
PARENT MATERIAL
ROCKS AND MINERALS

19. Major process of soil development
Physical weathering
Chemical weathering
Decomposition
Mineralization
Nitrification

20. Physical weathering:
The breakdown of rock (the regolith) into finer particles through weathering

21. Chemical weathering: The breakdown and redeposition of
organic and inorganic substances primarily through the processes of oxidation, dissolving, and leaching.

22. Decomposition: The breakdown of organic matter by bacteria
and fungi into simpler organic substances (carbohydrates, lignins, proteins).

23. Mineralization:
The ultimate breakdown of organic substances into nonorganic substances (minerals, carbon
dioxide, water, salts).

24. Nitrification:
The transformation by soil bacteria of ammonia compounds into nitrates and nitrites.

25. What causes soil erosion?
Water
Wind
No Vegetation

26. Over half of the topsoil has been lost over the past 200 years

27. Salinization Accumulation of salts in the soil Causes: Natural
Irrigation by raising groundwater level temporarily and evaporation

28. Soil and Erosion Consequences
-Topsoil loss (90% of soil
fertility)
– Sedimentation (rivers and
coastal ecosystems)
– Desertification – loss of
water-holding properties
of soils

29. Desertification & Land Degradation
Land Degradation happened when human activity or natural processes damage the land so that it can no long support the local ecosystem.
Desertification is the process by which land in arid or semiarid areas become more desert like due to human impact.

30. SOIL CONSERVATION? Terracing Strip Cropping Contour Plowing Tilling
What are some practices Of
SOIL CONSERVATION?
Terracing
Strip Cropping
Contour Plowing
Tilling
Wind Breaks
Ground Covers

31. Tilling Soil on flat land

32. Furrow Irrigation

33. Minimum Tillage

34. Strip Crop Farming

35. Organic Farming
Ecosystem management rather than external inputs • Considers environmental and social impacts of fertilizer and pesticide use • Conserves water and soil • Certification: USDA accreditation (farms must be certified) • Organic products: 100%organic, organic (95%), > 70% organic, < 70% organic

36. Does Organic Farming Work?
21-y Swiss study (2002)
– Yield – 20% less
– Resource use reduced
Fertilizer (34-53%)
Pesticides (97%)
– Increased biodiversity
• Health benefits
– WHO: million pesticide
poisonings per y
– Nutrient content
– Benefits to consumers?

37. Rain drop erosion

38. The Great Dust Bowl
Wind Erosion

39. Wind Erosion removed topsoil

40. Rill Erosion

41. Gully Erosion
How did the Canyon Lands
of Utah form?

42. Construction

43. Overgrazing

44. Pest Control
Insects eat approx imately 13% of crops in North America Pesticides are chemicals used to kill insects, weeds, and other crop pests.

45. Pesticide Issues Pesticide Resistance ---evolution of resistance
Human Health Concerns
--cancer rates; illness of workers
Pollution and Persistence
--pesticides are designed to not break down rapidily—so they accumulate in soil and magnify up the food chain

46. Biological Pest Control
Introduction of a non-native species can remain unchecked and go wild unless natural predators are in ecosystem
Pathogens—using bacteria to control pests
Defensive Chemicals from plants--biodegradable