Week 5 - soil bio properties (organisms)

animals, fungi, bacteria

Role of soil organisms

• mix + aerate soil 

• fix atmos nitrogen 

• decompose org substances 

• not all creatures decompose substances, some promote soil aggregation and change structure 

What are the 4 groups of soil organisms +1? sub groups?

plant, animal, fungi (& mycorrhizae), bacteria
+ protista

mseo + macro

name the different components

what % of species live in the soil?

59%

What soil animals are there? (4) name their functions

1. mice, rabbits, moles - aerate soil + change soil structure, fertility

2. earthworms - poop waste = nutrients, aerate + mix soil

3. anthropods + gastropods - feed on decaying veg, aerates

• termites - breaks down plant fibre and builds mounds (high OM)

4. soil nematodes - microscopic (<2mm long)

name the different types of soil nematodes

• classified according to diff feeding habits 

• omnivores – feed ono decaying OM 

• predacious – feed on bacteria, fungi, algae 

• parasitic – infest plant roots 

what are the functions of soil fungi?

• the greatest biomass of all soil organisms

• the GOAT of decomposition

  • eats dead/living OM

• first visual sign of decomp → speeds up OM decomp

• directly attack cellulose + complex compounds

fungi excrete org substances that aid in soil aggregation

types of soil fungi (3+)

1. yeast = unicellular

2. molds, mildew, mushrooms = multicellular

3. soil mycorrhizae = mutualistic association between fungi + plant roots

• roots → transmits energy to fungi

• fungi → transmits nutrients and water back

• good protection of plant root

what are soil protistias? what do they do?

• algae, protoza, slime molds 

• dont play a role in decomp 

  • produce nutrients 

  • improve soil aggregation

• abundant in water and surface soil 

what are soil bacterias? classified?

• unicellular organisms

• most imp to biologicall process in soil

• classified by:

  • nutritional pattern

  • oxygen demand

  • symbiotic relationships

• autotrophic vs heterotrophic (produce their own energy vs consuming)

  • autotrophs = very important → can nitrify bacteria

what role does bactiera play in nitrogen fixation?

• causes formation of root nodule → bacteria enter → transforms N2 from atmos into amino acids 

• symbiotic bacteria infect plant root hairs 

• leguminous plants, pod bearing plants, some trees (alders) 

what is the optimal environment for soil microbial activity?

1. temperature

• warm temperatures for good activity (15-20C) 

• microbes are dormant at freezing (except arctic soil) 

2. water

• near or at field capacity 

• some good in saturated. anaerobic conditions 

3. pH

• bac less tolerant of acidic cond vs fungi 

• some bac good at low pH (6) 

nutrient needs of bacteria, how does the amount affect the processes?

N, P to decompose

C for energy 

• low nutrients = hard to decomp material, immobilization (not available for plants) 

• high nutrients = mineralization 

2 categorizations of soil flora

macroflora

• sources of OM (carbon) - crops, litter

• plants roots = 50% of plant biomass

microflora

• some are N2 fixing

• help in nutrient acquisition 

• decomposition of OM 

What are 5 drivers of soil biodiversity loss?

1. land use change

2. invasive species

3. unsustainable soil mgmt practices

4. pollution

5. soil sealing + urbanization 

What is soil organic matter (SOM)?

• fraction of soil composed of material that was once alive 

• plant + animal remains = OM

  • diff stages of decomp (cells + tissues + roots + microbes)

• all org matter has carbon

  • org c undergoes combustion → transformed into other types of C → released as CO2

what are the major sources of SOM? (5)

1. manure + crop residues in agriculture 

2. above ground plant inputs leaves, needles, wood 

3. below ground roots 

4. microfauna 

5. macrofauna

Where can you find areas with a lot of SOM in canada?

peatlands, grasslands, praries

• places with a lot of soil carbon