Fundamentals of Soil Science

1. Fundamentals of Soil Science Soil Organisms

2. Introduction - Soil Organisms • Reading Assignment: Brady and Weil, Chapter 10 • 3 lectures • It’s Alive • Beneath the Surface • Soil Engineers • Blended learning materials available on web site and DVD

3. Learning Objectives • Lecture 1 – Its Alive • Define key terms pertaining to soil organisms • Survey of organism types • Identify soil organisms’ activities within Food Web • Lecture 2 – Beneath the Surface • Describe how a community of microorganisms assimilates plant and animal materials, creating soil organic matter, recycling carbon and mineral nutrients, and supporting plant growth. • Relate soil quality to microorganisms • Lecture 3 – Soil Engineers • Explain why earthworms, ants and termites are called soil engineers • Discuss how people can manage soil to encourage a healthy, diverse soil community.

4. Lecture 1 Topics • Survey of Soil Organisms • Food Web

5. Lecture 2 Topics • Microorganisms living beneath the surface • Symbiotic Relationships • Nitrogen Fixation

6. Lecture 3 Topics • Earthworms • Ants and Termites • Soil Management

7. Lecture 1It’s Alive

8. Learning Objectives • Lecture 1 – Its Alive • Define key terms pertaining to soil organisms • Survey of organism types • Identify soil organisms’ activities within Food Web

9. Lecture 1 – Topics • Survey of soil organisms • Food Web • Vocabulary

10. Do you remember? • How is organic matter important to the healthy functioning of soil? • Stabilization of soil aggregates • Improved water holding capacity • Reservoir of plant nutrients and cation exchange capacity • Now you’ll learn….Soil Organisms are the principle players in the dynamic processes that control organic matter turnover

11. Why is the soil alive? A handful of healthy soil likely contains billions of organisms. A diversity of unseen creatures interact in the soil – they are microorganisms.

12. How many soil organisms per gram of soil? Bacteria – 1 billion/g Actinomycetes - 200 million/g Fungi – 10-20 million/g Protozoa – 1 million/g Nematodes – 50/g

13. What are the creatures in the soil? • Fauna (animals) • Macrofauna >2 mm (moles, prairie dogs, earthworms, millipedes) • Mesofauna 0.1-2 mm (tiny springtails and mites) • Microfauna <0.1 mm (nematodes and single-celled protozoans) • Flora (plants) • Roots of plants as well as microscopic algae and diatoms • Microbes <0.1 mm • Fungi (Eukaryotes) • Bacteria and Archaea (Prokaryotes)

14. Relative Size

15. Survey: Soil Microbes Soil bacteria Bacteria on fungi Fungi decomposing leaf tissue Mycorrhizal bodies and hyphae Ectomycorrhizae Vesicles Images from NRCS: http://soils.usda.gov/sqi/concepts/soil_biology/biology.html

16. Survey: Soil Flora and Microfauna Plant root, Fig 10.10 Diatoms, http://www.ucmp.berkeley.edu/chromista/diatoms/ Root feeding nematode Protozoa: amoeba eating bacteria Images from NRCS: http://soils.usda.gov/sqi/concepts/soil_biology/biology.html

17. Survey: Mesofauna and Macrofauna Fungal feeder – orabatid mite Predators Herbivore Shredders Images from NRCS: http://soils.usda.gov/sqi/concepts/soil_biology/biology.html

18. Satisfying Carbon Needs • Soil Organism classification: • Heterotrophs – rely on organic compounds for carbon and most also for energy. • Autotrophs – obtain carbon from carbon dioxide and energy from photosynthesis or oxidation of various elements.

19. Metabolic Grouping – C and Energy

20. Who eats what? Soil organisms can be grouped by what they eat: • Herbivores – • Detritivores – • Predators – • Fungivores – • Bacterivores – • Parasites – Living plants (parasitic nematodes, insect larvae, rodents, termites, ants, beetle larvae) dead plants animals fungi bacteria live off of but do not consume other organisms.

21. What are Organisms Doing? • Soil is an ecosystem. Many scientists believe that there are more species in existence below the surface of the Earth than above it. • A balance among these organisms make possible the functions of a healthy, high quality soil.

22. Measures of Diversity • Species diversity – • Functional diversity – • Functional redundancy – organisms present are evenly distributed among a large number of species the capacity to use a variety of substrates and carry out an array of processes. presence of several organisms to carry out each enzymatic or physical process

23. Diversity by Location • Forested areas – more diverse soil fauna and more fungal-dominated microflora • Grasslands – Total fauna mass per hectare and level of activity higher than in forest • Cultivated Fields – lower levels in numbers and biomass of soil organisms than native grasslands due to loss caused by tillage.

24. Soil Food Web Solar Energy Plants, algae, lichens, bacteria Primary Producers By-products Plants debris (detritus) CO2 Saprophytic bacteria, actinomycetes Mites & other shredders Primary Consumers Earthworm shredders Saprophytic fungi Nematodes (root feeders) Mycorrhizal fungi Heat Energy Loss Feces and dead bodies Mineral Nutrients Secondary Consumers Bacteria, fungi & actinomycetes Nematodes (root feeders) Protozoa Mites Springtails Earthworms Humus High Level Consumers Beetle, spider, centipede, ant predators Mammal and bird predators Predatory mites Amoebas Earthworms Nematodes

25. Summary • Soil is a complex, diverse ecosystem • Organisms incorporate plant residues into soil, return CO2 to the atm where it can be re-fixed into plants. In the process, soil organic matter is formed and essential plant nutrients are released. • 80-90% of metabolic activity in soil food web is bacteria and fungi • The activity of organisms is more important than the identity. Functional diversity vs. species diversity.