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Fundamentals of Soil Science Soil Organisms. Introduction - Soil Organisms Reading Assignment: Brady and Weil, Chapter 10 Reading Assignment: Brady and.

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Presentation on theme: "Fundamentals of Soil Science Soil Organisms. Introduction - Soil Organisms Reading Assignment: Brady and Weil, Chapter 10 Reading Assignment: Brady and."— Presentation transcript:

1 Fundamentals of Soil Science Soil Organisms

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

3 Learning Objectives Lecture 1 – Its Alive 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 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 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 Survey of Soil Organisms Food Web Food Web

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

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

7 Lecture 1 It’s Alive

8 Learning Objectives Lecture 1 – Its Alive 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 Survey of soil organisms Food Web Food Web Vocabulary Vocabulary

10 Do you remember? How is organic matter important to the healthy functioning of soil? 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 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 million/g Fungi – million/g Protozoa – 1 million/g Nematodes – 50/g

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

14 Relative Size

15 Survey: Soil Microbes Soil bacteriaBacteria on fungiFungi decomposing leaf tissue Mycorrhizal bodies and hyphaeEctomycorrhizaeVesicles Images from NRCS:

16 Survey: Soil Flora and Microfauna Protozoa: amoeba eating bacteria Plant root, Fig 10.10Diatoms, Images from NRCS: Root feeding nematode

17 Survey: Mesofauna and Macrofauna Predators Shredders Fungal feeder – orabatid mite Images from NRCS: Herbivore

18 Satisfying Carbon Needs Soil Organism classification: 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 Source of Energy Source of CarbonBiochemical OxidationSolar Radiation Combined organic carbon Chemoheterotrophs: All animals, plant roots, fungi, actinomycetes, and most other bacteria Examples: Earthworms Aspergillus sp. Azotobacter sp. Pseudomonas sp. Photoheterophs: Just a few algae Carbon dioxideChemoautotrophs: Many archea and bacteria Examples: Ammonia oxidizers – Nitrosomonas sp. Sulfur oxidizers – Thiobacillus denitrificans Photoautotrophs: Plant shoots, algae, and cyanbacteria Examples: Chorella sp. Nostoc sp.

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

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. 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. A balance among these organisms make possible the functions of a healthy, high quality soil.

22 Measures of Diversity Species diversity – Species diversity – Functional diversity – Functional diversity – Functional redundancy – 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 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 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. Cultivated Fields – lower levels in numbers and biomass of soil organisms than native grasslands due to loss caused by tillage.

24 Soil Food Web Primary Producers Primary Consumers Secondary Consumers High Level Consumers Beetle, spider, centipede, ant predators Earthworms Predatory mites AmoebasNematodes Plants, algae, lichens, bacteria Plants debris (detritus) Solar Energy Saprophytic bacteria, actinomycetes Saprophytic fungi Earthworm shredders Mites & other shredders Nematodes (root feeders) Mycorrhizal fungi Protozoa Nematodes (root feeders) Mites SpringtailsEarthworms Bacteria, fungi & actinomycetes By-products Heat Energy Loss CO 2 Mammal and bird predators Feces and dead bodies Humus Mineral Nutrients

25 Summary Soil is a complex, diverse ecosystem Soil is a complex, diverse ecosystem ‒Organisms incorporate plant residues into soil, return CO 2 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.


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