Overview
This lecture covers primary productivity, focusing on how solar energy is transformed by living organisms, the factors affecting productivity, and its relationship to biodiversity.
Primary Productivity Basics
- Primary productivity is the rate at which solar energy is converted into organic compounds by photosynthesis over time.
- Measured in kilocalories per square meter per year (kcal/m²/yr).
- Higher primary productivity means higher plant growth, providing more food and shelter for animals.
- Ecosystems with high primary productivity have higher biodiversity.
Calculating Primary Productivity
- Plants use some captured energy for cellular respiration to sustain basic life processes.
- Gross Primary Productivity (GPP): total solar energy captured and converted by plants.
- Respiration Loss: energy used by plants for maintenance.
- Net Primary Productivity (NPP): energy stored as biomass, available to consumers; calculated as NPP = GPP – Respiration Loss.
Ecological Efficiency and Energy Flow
- Only about 1% of incoming sunlight is captured by plants for photosynthesis (GPP).
- Of that 1%, about 40% is stored as biomass (NPP).
- The remainder of sunlight is reflected or passes through leaves without being used.
Productivity Trends and Influencing Factors
- More productive ecosystems support greater species diversity and higher biodiversity.
- Key factors increasing productivity: high water availability, warm temperatures, and abundant nutrients.
- Highly productive biomes: swamps, marshes, tropical rainforests, and coral reefs.
- Low productivity biomes: deserts (low water and nutrients), tundra (cold, low liquid water), and open ocean (low nutrients).
Key Terms & Definitions
- Primary Productivity — Rate of conversion of solar energy into organic compounds by producers.
- Gross Primary Productivity (GPP) — Total energy captured via photosynthesis.
- Respiration Loss — Energy used by plants to sustain themselves.
- Net Primary Productivity (NPP) — Energy stored in plant biomass, available to consumers; NPP = GPP – Respiration Loss.
- Ecological Efficiency — Percentage of incoming sunlight converted to biomass.
Action Items / Next Steps
- Practice describing the process of net primary productivity.
- Describe the relationship between primary productivity and biodiversity.
- Review the chart of biomes and factors influencing productivity.