This document provides an overview of soil biodiversity and the roles of different soil organisms. It discusses microorganisms, microfauna, mesofauna, macrofauna and their functions. Key groups include earthworms, termites, ants and their roles in nutrient cycling, soil structure formation, and carbon sequestration. Land use and management practices can positively or negatively impact soil biodiversity. Maintaining soil organic matter and reducing tillage are important for soil health improvement.

1. Soil Biodiversity
General overview
Shreeram Ghimire
M.Sc. Zoology
(Soil ecology)

2. Microbiota
• Soil organisms 20-200 µm in length and <0.1 mm in diameter
• Comprises Microorganisms and Microfauna
• Microorganisms: algae, bacteria, cyanobacteria, fungi, yeast,
myxomycetes and actinomycetes
Transform organic material into plant nutrients
• Microfauna: Collembola, Mites, Nematodes and Protozoa
Live in soil-water film and feed on microflora

3. Mesobiota (mesofauna)
• 200µm to 20 mm in size and 0.1 to 2 mm diameter
• Microarthropods: pseudoscorpions, protura, diplura, springtails,
mites, small myriapods (Pauropoda and Symphyla)
• Inhabits in soil pore
• Feeding on organic materials, microflora, microfauna and soil
invertebrates

4. Macrobiota (soil Macroinvertebrates)
• Earthworms, Millipedes, Centipedes, Ants, Termites, Coleoptera,
Spiders, Isopoda, Slug, Snail, Dermaptera, Lepidoptera larvae and
Diptera larvae

5. Soil functional group
• Micropredator
• Litter transformers
• Ecosystem engineers

6. Micropredators
• Smallest invertebrates, Nematodes and Protozoans
• Mineralization of soil organic matter (SOM)

7. Litter transformers
• Mesofauna and macrofauna
• Re-ingest own secretion to incubate bacteria and assimilate
metabolite liberated by microbial action in digestive system

8. Ecosystem engineers
• Earthworms, termites and ants
• Producing physical structures to modify availability of resources for
other soil organisms
• Excavating soil to produce organo-mineral structures (excretions,
nests, mounds, macropores, galleries and caverns) also called
“Biogenic structure”
• Major roles in: Stimulation of soil microbiological activities,
formation of soil structure, SOM dynamics, exchange of water and
gases

9. Major functions in Soil
• Decomposition and nutrient cycles
• Soil structures
• Carbon sequestration and gas (GHGs) exchange
• Soil hydrology
• Soil detoxification
• Plant nutrients
• Pest and diseases control
• Live associations: Rhizobium, Mycorrhiza,

10. Soil macrofauna: physical roles
• Macromixing: of deep soil to upper layer and own excretion to low
layer
• Micromixing: of organic matter to soil by Diptera larvae
• Fragmentation: dead and decayed material
• Gallery costruction: earthworms and termites forming burrow
• Aggregate formation: humus and soil aggregate essential for plants

11. Soil macrofauna: chemical roles
• Mineralization of organic matter when passing through gut
• Combination of SOM and soil microfauna producing chemical changes

12. Soil macrofauna: biological roles
• Competition and Predation
• Necrophagy and coprophagy
• Network of galleries, accumulation of biogenic aggregates and soil
deposits
• Controlling pathogen population

13. Land use management and Soil macrofauna
• Inversely affected by increased intensity of crop cultivation:
mechanization and agrochemical application
• Soil macrofauna very sensitive to SOM and nutrient value of soil
• Micromanagement: abundance root system in lower layer and leaf
litter in upper layer
• Cropping: decrease in taxonomic richness, density and biomass

14. Indirect land management practices
• Managing soil biotic processes such as habitat, microclimate, nutrient
and energy resources
• Application of organic materials, tillage management, green manuring
and liming to soil
• Pest management: nematode management

15. Direct land management practices
• Management of specific group of organisms
• Inoculation of seeds and roots with Rhizobium, Mycorrhiza and
Rhozobacteria
• Inoculation of soil and surrounding environment with biocontrol
agents for pest and diseases, antagonists and beneficial fauna like
earthworms
• Improved pasturing

16. Soil Macrofauna communities: structure and
ecology
• Key indicator: Earthworms, Termites, Ants, Myriapoda, Diptera and
Coleoptera

17. Earthworms
• Live in litter and soil in al except coldest regions of the world
• Ecosystem engineers
• Distinction: Epigeic (surface dwellers, phytophagous), Anecic
(Geophytophagous, subvertical galleries) and Anecic (Unpigmented,
Geophagous)
• Epigeic: composting earthworm
• Anecic: gallery forming earthworm near earthsurface

18. Termites
• Feeding dead log, soil (humus), mineral soil, clay and silt fraction
• Influence: i)soil porosity and texture through tunneling, soil ingestion
and gallery construction ii)nutrient cycling through shredding and
digestion of organic matter

19. Ants
• Modify soil chemical and physical properties by transporting food and
soil materials during feeding and mound and gallery construction
• Nest construction: incorporation of large amounts of organic matter
and nutrients into soil

20. Myriapoda
• Consuming plant debris and flourishing soil by their droppings
• Soil surface dwellers
• Little or no ability to penetrate soil

21. Diptera
• Feed on decaying plant materials
• Good agent of reducing dead plant and animal debris

22. Coleoptera (beetles)
• Most diverse
• Feeding on fungi, plant roots, buried wood, dung, corpses and other
rotting organic matter
• Dung beetles, white grubs, weevil larvae
• Digging sub-vertical galleries

23. Biogenic structures of soil macroinvertebrates
• Earthworm casts
• Earthworm burrows
• Termite mounds
• Ant heaps
• Roots

24. Earthworm casts
• Granular: small pellets produced by epigeic worms
• Globular: large aggregates produced by endogeic and anecic
worms, coalesce into large tower like structures
Earthworm burrows
• Sub-vertical and semi-permanent burrows by endogeic worms
• Horizontal burrows by endogeic worms
• Surface of gallery rich in soil microbes (5-25% of total soil
microflora resides in earthworm galleries)

25. Termite mounds (termitaria)
• Half of nest constructed below soil surface
• Bringing fine clay particles from deep soil
• Excretions rich in organic matter
Ant heaps
• Leaf cutting ants form huge nest which finally incorporate nutrient matter
and nutrient to soil
• Bioturbation by ants when nests are formed in soil
• Transporting food and soil materials modifying soil chemical and physical
properties

26. Roots
• Included as soil biota
• Rhizosphere (adjacent soil layer to root) with dynamic environment where
plants, soil, microorganisms, nutrients and water meet and interact
• Rhizosphere attracts large number of organisms
• Earthworm galleries along rhizosphere
• Mycorrhizal association establishes in rhizosphere region
• Rhizosphere provides space to control nematode by attracting other soil
organisms

27. Soil life improvement management practices
• No tillage: higher population of soil biodiversity, greater ration of
fungi/bacteria, organic matter accumulation on soil surface, nutrient
conservation, lower runoff and erosion
• Organic matter input: increased nutrient availability, improved soil
physical structure and water relations, reduction in acidity and
aluminium toxicity, greater microbial and fauna (detrivores) activity
• Crop rotations: improved pest and disease management, efficient
soil nutrient utilization, greater diversity aboveground and
belowground, improved soil aggregation and infiltration, reduced bulk
density, higher organic matter

28. Soil Health
• Soil living system
• Major components: Physical, Chemical and Biological factors
• SOM dynamics and nutrient cycling, purification of water,
detoxification of agrochemicals and modification of soil structure

29. Soil health improvement
• Crop rotation
• Crop residue, animal manure and vegetation scraps covering soil
• Reducing tillage intensity
• Balanced nutrient to plant without polluting water
Soil organic matter improvements
Soil microbes improvements