BI303 - Section 1 Lecture 8

What role do aerobic microbes play in soil?

They are key to decomposition and nutrient cycling

Why do aerobic microbes function best in well-aerated soil?

Because they require oxygen for their metabolic processes

What is the universal limiting factor for organic growth in soils?

Nitrogen

Which enzyme fixes atmospheric N2 into organic ammonium?

Nitrogenase

Which bacteria are known for nitrogen fixing?

Rhizobium

What do nitrifying bacteria like Nitrosomonas convert amonnium into?

Nitrite

What factors contribute to soil aeration and water mobility?

Physical struction and anion/cation balance

What is the principle source of energy for aerobia microbes in soil?

Microbidal oxidation of organic matter

What happens to CO2 produced by microbidal respiration?

It routes back to the atmosphere

What is net mineralisation in soil?

More nutrients are released than taken up

What occurs during net immobilisation in soil?

Microbes utilise most nutrients produced

What is the chemical equation for microbidal resipiration via decompositon of glucose?

C6H12O6 + 6O2 --> 6CO2 + 6H20 + energy

What is the ideal carbon to nitrogen ration in temperate arable soils?

20:1 to 30:1

What happens when the C:N ratio is low?

Excess nitrogen is relreased as NH4

What occurs with a high C:N ration?

Nitrogen is foraged by microbes

What is essential for sustainable farming regarding soil?

Well-aerated soil with good organic matter

What facotes influence the mean residence time for soil nutrients?

Temperature, soil structure, organic matter

What type of soils are generally less fertile?

Poorly drained soils

How does soil water saturation affect soil properties?

It impacts oxygen availability, pH, nutrients

What historical events were influenced by soil distribution in Ireland?

Norman colonisation, Elizabethan plantations, famine

What type of vegeation dominates modern Ireland?

Grassland

What are lazy beds in the context of Irish agriculture?

Abandoned potato plots cultivated by farmers

What was the impact of potato physiology on cultivation?

Allowed high yields in poor soils

What does the class data indicated about biomass per seedling?

Significant difference in well-drained soils

What is the relationship between soil quality and above-ground NPP?

Soil quality directly impacts NPP

How do global biome vegetation types differ?

In standing plant biomass and nutrient ratios

What characterises high energy ecosystems like tropical rainforests?

Very rapid nutrient cycling

What are the main drivers of deforestation in the Amazon?

Need for land and demand for timber

What is the impact of slash and burn agriculture in the Amazon?

Causes massive nutrient loss in soils

What are the predicted impacts of climate change on soils?

Changed rainfall patterns and temperatures

How does increased evaporation affect soil moisture?

It leads to soil moisture deficit

What is the effect of freeze/thaw cycles on plants?

They can damage roots and rhizosphere

What happens to soil community stability during drought?

Loss of soil community stability and resilience

What is the relationship between soil depth and nutrient status?

Soil depth impacts nutrient status significantly

How does soil type affect humanity?

It has a major impact on agriculture

What is the significance of the digital soil map of Ireland?

It shows complex spatial distribution of soils

What are Mor-type soils and where do they predominate?

A form of forest floor humus occurring mostly in coniferous forests in the west and Shannon basin

What was the role of potato cultivation in pre-famine Ireland?

Facilitated population expansion in poor soils