Test 1 Flashcards
Where are soil organisms mainly found?
Upper, organic soil horizons.
Mineralization is frequently carried out by what?
Microorganisms (fungi and bacteria)
Describe ericoid mycorrhizae
Similar to arbuscular but instead of arbuscules, they form hyphal coils. Roots associated with ericoid tend to be very thin with few layers of cortical cells
What does extended periods of waterlogging do to the soil?
Extended periods of waterlogging alters the soil community, composition, affecting process rates.
What is the result of rock weathering?
Small particles of mineral rock that form the basic material of soil
Definition: Jenny’s Soil Forming Factors
Soil = a function of (cl, o, r, p, t); climate, organisms, relief (topography), parent material, time
Definition: components that are non-living and regenerated from weathering of rock
Abiotic components
What does the biotic or living components of the soil consist of?
A wide diversity of taxa of plants, animals, bacteria, actinomycetes
What is the role of the biotic components in soil?
Effect processes that result in maintenance of the fertility of soil.
What is the importance of air spaces between soil particles for larger organisms?
Air spaces allow for larger soil organisms to move as well as reduce soil bulk density.
What is a pedosphere and what components make it up?
A pedosphere is the sum total of all the soils. It is made up of the lithosphere (rock), atmosphere (air), hydrosphere (water), and the biosphere (organisms and life).
What is soil fertility and why is it important?
Chemical reactivity of the surface of weathered rock particles and the nature of the mineral elements give soil fertility. The fertility of soil is the amount of mineral nutrients dissolved in soil solution available for plant uptake.
How is organic material added to the soil?
Death of organisms
The cascade of decomposition results in?
-Faster loss of readily utilized, simple substrates by r-strategists
–Longevity of recalcitrant, complex substrates
–Increased homogeneity of environmental variables
(moisture, temperature fluctuations, aeration etc.)
–Reduced resource niche size
–Restriction of fungal species diversity
–Selection for K-strategists
What process provides more soil fertility?
Mineralization
What’s the main difference between a grassland soil profile and a forest soil profile?
Grassland has a large A horizon with a lot of decomposing organic material. There is little to no O horizon unlike the forest soil profile. There is no leaching zone in grassland.
Definition: partially decomposed material is found that is less easy to identify
A horizon or humic horizon
Definition: incorporation of fine organic particles with mineral particles
B horizon
What is the function of fungi as decomposers?
Drive the global carbon cycle
What does the nitrogen cycle not have?
Parent rock input
What is the function of fungus in lichens?
They clothe what might otherwise be bare parts of the planet.
What are some functions of fungus?
Produce extracellular enzymes to break down organic substrates and to absorb that break down. Fungi produce organic acids which is important in changing the environment and dissolving substrates
What are some important properties of water?
A stabilizing influence (buffer) on soil temperature, essential for biotic activity, free water or humidity
Definition: breakdown of the organic molecules into inorganic molecules by living organisms
Mineralization
Is soil synonymous with dirt?
No!
Definition: organic matter accumulates on the soil profile
O Horizon or litter horizon
When does denitrification usually occur?
Anaerobic conditions in deep soil and aquatic sediments.
Definition: dead remains of biotic entities
Organic matter
Definition: organisms that live within the soil surface
Endogeic
What enzyme is required for nitrogen fixation?
Nitrogenase
Why do roots and their associate microflora go deeper into the soil?
For water and stability
What group of microorganisms plays an important role in the movement of nitrogen through the ecosystem in the nitrogen cycle?
Bacteria (nitrogen fixing, ammonifying, nitrifying, denitrifying)
Definition: accumulation of inorganic nutrient elements into organisms
Immobilization
Combining organic matter with clay and mineral soil particles
by ionic charges or other means results in the formation of?
Soil aggregates
What are soil aggregates bound by?
Hyphae, polysaccharide are from bacteria, and glycoproteins from fungi
What is the importance of aggregate stability?
Can protect organic matter from attack by microorganisms, and the soil pore water between aggregates contains nutrients for plant uptake as well as provide a habitat for small soil organisms
What are the four components that make up an ecosystem?
Abiotic substances, producers, consumers, decomposers
Definition: study of individual species
autecology
What is the relationship between nutrient availability and mycorrhizae?
It was suggested that the mycorrhizal symbiont present is related to the availability of nutrients in the soil.
Definition: the study of organisms within a community
Synecology
How does the carbon cycle take in and release carbon?
Plant and soil sequestration and biotic respiration, erosion, and combustion
Describe arbuscular mycorrhizae
Associated mainly with herbaceous plants and some trees. Limited range of zygomyete fungal species with a large range of host plant species. Fungal component penetrates epidermis and cortex cell walls. Develops an arbuscule. Produces spores within or outside the root
Describe ectomycorrhizae
Associated with tree species. Large range of basidiomycete and ascomytete fungi with small diversity of plant species. Fungal component DOES NOT penetrate plant cells. Creates a sheath and between cortical cells is a Hartig Net, extensive hyphal network within and on surface of root. Spores produced AWAY from the root
What allows bacteria to efficiently secrete enzymes and recover end products of enzyme activity?
Large surface area to volume ratio
What are some major functions of soil?
Agriculture, forestry, primary production, engineering media, regulate water movement, place to dump waste
How are deeper horizons distinguished?
They are entirely mineral and are described by their physical structure and deposition of material from upper horizons
Production of what assists in the development of soil aggregates?
Polysaccharide exudates
What does the depth of the organic horizons depend on?
Input:Output balance between litter accumulation and rates of decomposition
Definition: a structured entity of abiotic and biotic components that provide a medium for plant growth and nutrient acquisition
Soil
Describe orchidaceous mycorrhizae
Orchids and basidiomycete and ascomycete close with orchids. Often so close, a fungal propagule is carried in the seed of the plant
Explain fragile resource.
Soil is a fragile resource that may take centuries to recover from damage. The demand for agriculture is turning forests into farmland and causing the soil to be unable to maintain itself.
What do nodulating (symbiotic) bacteria produce to bind oxygen?
Haemoglobin
What are some ways fungi trap nematodes?
Sticky apparatus, constricting rings, once trapped, nematodes are digested by secretions
What is PGPR and what does it do?
Plant growth promoting rhizobacteria and they live around root surfaces to produce auxins, IAA, and cytokinins to influence root growth
Properties of fungal hyphae include:
Translocation of material between cells, Woronin bodies to control pore gaps, contains chitin and no nuclear membrane
What is the air space in soil to water relationship?
It dictates the drainage pattern of soil and degree to which soil can become waterlogged and anaerobic.
How does hyphae grow in relation to resource quality?
High resource quality leads to slow and dense hyphal growth. Low resource quality leads to fast and diffuse hyphal growth.
Definition: organisms that move between the soil structure and soil surface
Anecic
What does the phosphorous cycle not have?
Atmospheric input
What is the function of fungi as mycorrhizal symbionts?
Form absorptive accessories to roots, linking the activities of separate plants and underpinning primary production
What is the counteraction after the cascade of decomposition occurs?
–Secondary chemicals are produced by the fungi
–Simpler resources are created by the reduction of
complex substrates
–Resource niche size can increase
–Environmental resource niche size remains reduced
How are protozoan classified?
Body shape and presence or absence of cilia and flagella
What is the function of fungus as parasites?
Regulate population dynamics of their hosts.
What are the climate conditions like for AM, EctoM, and EricM?
AM is associated with warm conditions, mineral soils, and high rates of nutrient availability. EctoM is associated with boreal forests and greater accumulation of organic soil horizons. EricM associated with subartic and alpine with low nutrient mineralization and high organic accumulation.
What are the roles of mycorrhizae?
Nutrient and water acquisition, defense against plant pathogens, sequestration of heavy metals, and undetermined plant fitness improvement
What part of an ecosystem are protozoa?
Secondary producers
What are the major types of protozoa?
Amoebae have no flagella or cilia and move by a pseudopod (false foot), ciliates are large and covered in small hairs, and flagellates have a single or multiple long hair
Why is the significance of the C:N ratio of protozoa?
Protozoa C:N is for every 10 carbon, they need 1 nitrogen. Bacteria have a 3:1 ratio and when protozoa consume the bacteria, they take in too much N needed so it’s released as ammonium.
What are the four types of nematode mouths?
Bacterivore have a vacuum mouth, phytophagous have a stylet, fungivore have a spear, and carnivores have teeth
Definition: where minerals are leached
E horizon or eluviated
What form is nitrogen fixed into the bacterial biomass?
Amino acids and proteins
How long does the microbial loop take?
5 days
Definition: cause decay of plant roots and influence the ability of plants to take up nutrients
Pathogenic bacteria
Definition: organisms restricted to the soil surface
Epigeic
What are other factors that can influence the rate of decomposition of litter?
Moisture, temperature, altitude, pollutants, exotic litter
What is the purpose of a secondary metabolite?
Produced as a result of metabolism and are important in controlling community composition.
