BI303 - Section 1 Lecture 7

What has the greatest impact on biome structure after temperature and rainfall?

Soil

What are the important aspects of soils that determine biome and habitat productivity?

Physical component.
Inorganic component.
Organic component.

What does the physical component of soil include?

Structural and chemical properties, water, temperature

What does the inorganic component of soil consist of?

Bedrock, weatherin and siltation

What is included in the organic component of soil?

Organic matter, soil microbes, protists, fungi, animals, plants

How does the organic component of soil affect habitat productivity?

It determines the functioning and efficiency of soil

What is the nature of soil as an ecosystem?

It is a complex, 3D ecosystem

What is concentrated in the uppermost layer of soil?

Biological activity and nutrient cycling

What is humus?

Decaying organic matter

What does topsoil consist of?

Humus, organic matter, minerals, clay mix

What is the composition of subsoil?

Clay and leached minerals

What is regolith?

Bedrock, rocks, clay

What characterises the leached layer of soil?

Sand and silt with low mineral conten

How does a typical soil profile vary across habitat types?

It's generally consistent with nutrient distibution

How do soils develop over time?

Through bedrock weather and biological activity

What influences the amount of soil biological activity?

Abiotic factors and soil biota

What are the inorganic components of soil?

Alumina-silicates, silica, calcium carbonate

What are the organic components of soil?

Raw decomposing material and collodial humus

What are the characteristics of Mull organic matter?

Fertile soils.
Good aeration and temperature.
Rapid cycling of organic matter.
Abundant microbes and soil animals.

What are the characteristics of Mor organic matter?

Forms in less favourable conditions.
Accumulates and acidifies.
Few decomposers, no nitrifying bacteria.

How does soil drainage affect soil chemistry?

Poor drainage increases waterlogging and decreases aeration

What types of soil are generally the most fertile?

Those with good drainage over base-rich bedrock

How does soil pH impact soil fertility?

Nutrient availability decreases with increasing acidity

What is the effect of low pH soils in the Arctic Tundra?

Fewer plant species survive compared to neutral soils

What groups comprise the soil biota?

Bacteria.
Fungi.
Earthworms.
Protists.
Animals.

What roles do bacteria play in soil health?

Nitrogen fixation, tissue degradation, nutrient cycling

What role do fungi play in soil health?

Tissue breakdown and nutrient cycling

What are the ecological niches of protists and animals in soil?

Tissue ingestion, predators, microbe feeders

What are actinomycetes?

Filamentous bacteria in soil

What do nitrifying bacteria do?

Oxidise ammonia to nitrite and nitrate

What is the role of soil protozoa?

They are bacteria eaters

What types of soil invertabrates are mentioned?

Earthworms, nematodes, beetles, flies

How does decomposition and nutrient cycling in soils get impacted?

By temparature and water content

How does temperature and water content affect decomposition?

Low soil moisture directly limits the activity of decomposers through desiccation.
Decompostion proceeds more rapidly at warmer temperatures.
High soil moisture limits the diffusion of oxygen, lowering the potential activity of decomposers.

What does the relatice soil microbidal respiration rate indicate?

Overall biological activity of the soil

How might climate related changes impact soil nutrient cycling?

Changes in temperature affect microbidal activity.
Altered rainfall impacts moisture levels.
Both factors influence nutrient availability.