Overview
This lecture covers primary productivity, focusing on how solar energy is converted by plants into usable energy, the factors influencing productivity, and the relationship between productivity and biodiversity.
Primary Productivity Basics
- Primary productivity is the rate at which solar energy is converted into organic compounds by photosynthesis.
- Measured in kilocalories per meter squared per year (kcal/m²/yr).
- Higher primary productivity leads to greater plant growth and more available food and shelter for animals.
Types of Primary Productivity
- Gross Primary Productivity (GPP): Total amount of sunlight captured and converted by plants into energy.
- Respiration Loss (R): Energy plants use for their own metabolic processes.
- Net Primary Productivity (NPP): Energy stored as biomass and available for consumers; calculated as NPP = GPP - Respiration Loss.
Ecological Efficiency
- Only about 1% of incoming sunlight is captured by plants for photosynthesis (GPP).
- Of that, about 40% (0.4% of total sunlight) becomes NPP available for plant growth and consumers.
- Most sunlight is either reflected or passes through leaves without being captured.
Factors Affecting Productivity
- High productivity is found in biomes with abundant water, warm temperatures, and high nutrient availability.
- Swamps, marshes, and tropical rainforests have high NPP due to these favorable conditions.
- Coral reefs are also highly productive due to warm temperatures, nutrient availability, and water abundance.
- Deserts have low NPP due to lack of water and nutrients.
- Tundra has low NPP because of cold temperatures and limited liquid water.
- Open ocean is low in NPP due to nutrient deficiency despite abundant water and suitable temperatures.
Productivity and Biodiversity
- Ecosystems with high primary productivity support greater biodiversity.
- More plant growth provides more food and habitats for different animal species.
Key Terms & Definitions
- Primary Productivity — The rate of transformation of solar energy into organic compounds via photosynthesis.
- Gross Primary Productivity (GPP) — Total captured solar energy converted by plants.
- Respiration Loss (R) — Energy expended by plants for their own life processes.
- Net Primary Productivity (NPP) — Energy stored as plant biomass after accounting for respiration loss.
- Ecological Efficiency — The proportion of incoming sunlight actually converted into biomass.
Action Items / Next Steps
- Describe the process of net primary productivity in your own words.
- Explain the relationship between primary productivity and biodiversity.
- Review factors that determine productivity in various biomes for upcoming assessments.