L14 - Introduction to the biodiversity of soil Flashcards
Why has soil historically been important to human communities?
Soil provided most of their food and nutrients, essential for survival and development
How do early Polynesian settlers view soil?
As the mantle of the Earth Mother, symbolizing its sacred importance.
What percentage of the world’s soil is degraded?
33% of land is moderately to highly degraded.
How much topsoil is lost to erosion annually?
25-40 billion tons of topsoil
What historical event exemplifies the catastrophic consequences of soil neglect?
The Dust Bowl in the American Great Plains during the 1930s.
How much carbon do soils store globally?
Soils contain 2,500 billion tons of carbon, which is 2.7 times more than the atmosphere
What are the hallmarks of a healthy soil?
A living soil ecosystem with biodiversity, good structure, nutrient cycling, neutral pH, and water retention.
How much of Earth’s living diversity resides below ground?
One-quarter of all living diversity is below ground
What are the classifications of soil biota by size?
- 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).
What is the primary role of microbial biomass in soil?
Breaking down organic material, nutrient transformation, structural stability, and forming symbiotic relationships.
What are mycorrhizal fungi?
Fungi that form symbiotic relationships with plant roots, exchanging carbon for nutrients
What is nitrogen fixation, and who performs it?
The conversion of atmospheric N₂ to ammonia by free-living or root-associated prokaryotes, such as rhizobia bacteria
What is the most abundant soil fauna?
Nematodes, with populations exceeding 2 billion per hectare.
What is the role of protozoa in soil?
Feeding on bacteria and fungi, serving as decomposers, and surviving unfavorable conditions through cyst formation.
Which soil fauna are dominant in acidic, peat soils?
Enchytraeid worms, which are keystone species in boreal forests and tundra.
How do earthworms contribute to soil fertility?
By aerating soil, recycling nutrients, and enhancing soil structure
What is the rhizosphere effect?
The zone around plant roots where microbial abundance and diversity are stimulated by root exudates.
What abiotic factors influence soil biodiversity?
Soil porosity, water availability, temperature, and pH levels
How does climate change affect soil biodiversity?
Increased aridity reduces soil microbial diversity, especially in global drylands
Are soil microorganisms geographically restricted?
Many microorganisms are widespread, but larger soil animals often have restricted, endemic distributions
What is the primary role of the soil food web?
Recycling organic matter from the plant-based food web.
What human activities have degraded soil?
Intensive farming, deforestation, climate change, and improper soil management practices
Why is soil protection urgent?
It takes thousands of years for soil to form, and degradation has long-term consequences for ecosystems and human survival.
