UNIT 4

Soil ecosystem services

Nutrient cycling, water filtration, carbon storage, plant support, habitat for organisms

Soil formation

Weathering of rock + organic matter accumulation

Soil formation rate factors

Climate, organisms, topography, parent material, time

Weathering

Breakdown of rock into smaller particles

Erosion

Movement of soil by wind, water, or gravity

Carbon in soil

Stored as organic matter; released by decomposition, erosion, or burning

O horizon

Organic layer (leaf litter)

A horizon

Topsoil; most nutrients and roots

E horizon

Leached layer (loss of minerals)

B horizon

Subsoil; accumulation of minerals

C horizon

Weathered parent material

R horizon

Bedrock

Leaching

Removal of nutrients by water moving downward

Soil particle sizes

Sand (largest), silt (medium), clay (smallest)

Soil texture triangle

Used to determine soil type based on % sand, silt, clay

Best soil texture

Loam (balanced mix of sand, silt, clay)

Porosity

Amount of space in soil

Permeability

Rate water moves through soil

Porosity vs permeability

High porosity ≠ always high permeability (clay has high porosity but low permeability)

Soil moisture and texture

Clay holds most water, sand holds least

Macronutrients in soil

Nitrogen (N), phosphorus (P), potassium (K)

Plants preventing erosion

Roots hold soil, reduce runoff

Causes of soil erosion

Deforestation, overgrazing, agriculture, construction

Effects of erosion

Loss of fertility, sediment pollution, desertification

Dust Bowl

1930s Midwest drought + poor farming → severe erosion

Food security

Access to sufficient, safe, nutritious food

Undernutrition

Not enough calories

Malnutrition

Lack of essential nutrients

Famine

Severe food shortage leading to mass starvation

Overnutrition

Excess calorie intake

Human macronutrients

Carbohydrates, proteins, fats

Vitamin A deficiency

Night blindness

Iron deficiency

Anemia

Iodine deficiency

Goiter, thyroid issues

Major global grains

Rice, wheat, corn

Old-growth forest

Undisturbed, high biodiversity

Second-growth forest

Regrown after disturbance

Tree plantation

Monoculture trees for harvest

Forest services

Habitat, carbon storage, water regulation, recreation

Clear-cutting

All trees removed; efficient but damaging

Strip-cutting

Trees cut in strips; less damage than clear-cutting

Selective cutting

Only some trees removed; most sustainable

Logging roads

Cause erosion, habitat fragmentation

Fire in ecosystems

Recycles nutrients, promotes biodiversity

Fire prevention

Controlled burns reduce fuel buildup

Rangeland

Land used for grazing livestock

Overgrazing

Removes vegetation → soil erosion, degradation

Sustainable rangeland

Rotational grazing, limit livestock numbers

Food desert

Area with limited access to affordable nutritious food

Food security obstacles

Poverty, conflict, climate, poor infrastructure

Industrial agriculture

Large-scale, high-input farming

Subsistence agriculture

Small-scale farming for personal use

Slash-and-burn

Clearing land by burning vegetation

Intensive agriculture

High labor input on small land

Polyculture

Multiple crops grown together

Monoculture

Single crop grown; less sustainable

Green revolution

Increased food production via tech, fertilizers, irrigation

Artificial selection

Humans breed organisms for traits

Genetic engineering

Direct DNA modification

Meat consumption increase

Higher income, urbanization, demand for protein

Desertification

Land becomes desert due to degradation

Salinization

Salt buildup in soil from irrigation

Waterlogging

Soil becomes saturated, roots lack oxygen

GM foods pros

Higher yields, pest resistance

GM foods cons

Ethical concerns, biodiversity loss

CAFO

Concentrated Animal Feeding Operation

Agriculture and biodiversity

Habitat loss, monoculture reduces diversity

Increasing crop yields

Tech, improved crops, better practices

Limits to more land/irrigation

Land scarcity, water depletion

Rachel Carson

Author of Silent Spring; exposed pesticide dangers

Pesticide persistence

How long pesticide remains in environment

Pesticide pros

Increased crop yield, disease control

Pesticide cons

Resistance, harm to non-target species

Genetic resistance

Pests evolve resistance to pesticides

Terracing

Steps on slopes to reduce erosion

Strip cropping

Alternating crops to reduce erosion

Contour planting

Plowing along land contours

Alley cropping

Trees planted between crops

Windbreaks

Trees reduce wind erosion

No-till farming

Minimal soil disturbance

Perennial plants

Live multiple years; reduce erosion

Fertilizer disadvantages

Runoff pollution, eutrophication, soil degradation

Natural fertilization

Compost, manure, crop rotation

Alternative pest control

Biological control, crop rotation, traps

IPM

Integrated Pest Management; combines methods to reduce pests

Eating lower trophic level

More energy efficient, less resource use

Organic agriculture

No synthetic chemicals; more sustainable

Local/seasonal food

Less transportation emissions

Feedlot disadvantages

Waste pollution, disease, animal welfare issues

Grass-fed benefits

Less pollution, healthier ecosystems