Primary Production: Autotrophs Build Biomass by Fixing Carbon
- Production in ecosystems is the accumulation of carbon compounds in biomass.
- This process forms the foundation of life on Earth, as both autotrophs and heterotrophs contribute to biomass production through growth and reproduction.
Definition
Primary production
Primary production refers to the synthesis of organic carbon compounds from carbon dioxide by autotrophs, such as plants and algae, using external energy sources like sunlight.
- Plants are termed primary producers because they generate the carbon compounds that sustain other organisms in the ecosystem.
This measurement focuses on carbon because it is the backbone of organic molecules, making it a key indicator of biomass accumulation.
Key Metrics of Primary Production
- Gross Primary Production (GPP): The total biomass of carbon compounds made by plants during photosynthesis.
- Net Primary Production (NPP): The biomass available to consumers after accounting for carbon lost due to plant respiration. NPP = GPP - Respiration.
Units of Measurement
- GPP and NPP are typically measured over long time intervals (e.g., a year) and at the ecosystem level.
- Units include:
- Grams of carbon per square meter per year (g C m⁻² yr⁻¹).
- Alternate units: grams per square meter per hour or tonnes per hectare per year.
- It’s a common misconception that plants gain most of their mass from soil.
- In reality, the majority of their biomass comes from carbon dioxide in the air, converted into organic matter through photosynthesis.
Why Primary Production Matters
- Foundation of Food Chains: Primary production provides the energy and organic matter that sustain all other organisms in an ecosystem.
- Carbon Cycling: Autotrophs play a critical role in the carbon cycle by removing carbon dioxide from the atmosphere and storing it in biomass.
- Ecosystem Services: High primary production supports biodiversity, stabilizes ecosystems, and contributes to services like oxygen production and climate regulation.
How might differences in primary production across biomes influence human activities, such as agriculture or conservation efforts?
