L14 - Introduction to the biodiversity of soil

Question 1

Why has soil historically been important to human communities?

Answer 1

Soil provided most of their food and nutrients, essential for survival and development

Question 2

How do early Polynesian settlers view soil?

Answer 2

As the mantle of the Earth Mother, symbolizing its sacred importance.

Question 3

What percentage of the world’s soil is degraded?

Answer 3

33% of land is moderately to highly degraded.

Question 4

How much topsoil is lost to erosion annually?

Answer 4

25-40 billion tons of topsoil

Question 5

What historical event exemplifies the catastrophic consequences of soil neglect?

Answer 5

The Dust Bowl in the American Great Plains during the 1930s.

Question 6

How much carbon do soils store globally?

Answer 6

Soils contain 2,500 billion tons of carbon, which is 2.7 times more than the atmosphere

Question 7

What are the hallmarks of a healthy soil?

Answer 7

A living soil ecosystem with biodiversity, good structure, nutrient cycling, neutral pH, and water retention.

Question 8

How much of Earth’s living diversity resides below ground?

Answer 8

One-quarter of all living diversity is below ground

Question 9

What are the classifications of soil biota by size?

Answer 9

• Microflora: Bacteria, archaea, fungi
• Microfauna: <0.1 mm (e.g., nematodes, protozoa)
• Mesofauna: 0.1-2.0 mm (e.g., microarthropods, enchytraeids)
• Macrofauna: >2 mm (e.g., earthworms, termites).

Question 10

What is the primary role of microbial biomass in soil?

Answer 10

Breaking down organic material, nutrient transformation, structural stability, and forming symbiotic relationships.

Question 12

What are mycorrhizal fungi?

Answer 12

Fungi that form symbiotic relationships with plant roots, exchanging carbon for nutrients

Question 13

What is nitrogen fixation, and who performs it?

Answer 13

The conversion of atmospheric N₂ to ammonia by free-living or root-associated prokaryotes, such as rhizobia bacteria

Question 14

What is the most abundant soil fauna?

Answer 14

Nematodes, with populations exceeding 2 billion per hectare.

Question 15

What is the role of protozoa in soil?

Answer 15

Feeding on bacteria and fungi, serving as decomposers, and surviving unfavorable conditions through cyst formation.

Question 16

Which soil fauna are dominant in acidic, peat soils?

Answer 16

Enchytraeid worms, which are keystone species in boreal forests and tundra.

Question 17

How do earthworms contribute to soil fertility?

Answer 17

By aerating soil, recycling nutrients, and enhancing soil structure

Question 18

What is the rhizosphere effect?

Answer 18

The zone around plant roots where microbial abundance and diversity are stimulated by root exudates.

Question 19

What abiotic factors influence soil biodiversity?

Answer 19

Soil porosity, water availability, temperature, and pH levels

Question 20

How does climate change affect soil biodiversity?

Answer 20

Increased aridity reduces soil microbial diversity, especially in global drylands

Question 21

Are soil microorganisms geographically restricted?

Answer 21

Many microorganisms are widespread, but larger soil animals often have restricted, endemic distributions

Question 22

What is the primary role of the soil food web?

Answer 22

Recycling organic matter from the plant-based food web.

Question 23

What human activities have degraded soil?

Answer 23

Intensive farming, deforestation, climate change, and improper soil management practices

Question 24

Why is soil protection urgent?

Answer 24

It takes thousands of years for soil to form, and degradation has long-term consequences for ecosystems and human survival.