Primary Productivity Patterns in Terrestrial and Aquatic Ecosystems

Primary productivity is the rate at which plants and other photosynthetic organisms produce organic matter in a specific area over time. It is measured as biomass (dry mass) accumulated per unit area per year (g/m²/year).

Terrestrial ecosystems

Terrestrial primary productivity is influenced by Temperature, Moisture, and Nutrient Availability.

In 1968, Michael Rosenzweig studied how moisture and temperature affect primary production by looking at the relationship between annual net primary production and annual Actual Evapotranspiration (AET).

High AET and High Primary Production : Ecosystems characterized by high AET, such as tropical rainforests, exhibit high levels of primary production. This is attributed to the warm temperatures and abundant rainfall that facilitate optimal conditions for photosynthesis, leading to greater biomass accumulation.

Low AET and Low Primary Production : Conversely, ecosystems with low AET, such as deserts and tundras, show low primary production. Limited rainfall and colder climates restrict plant growth, resulting in minimal biomass accumulation. For instance, deserts have some of the lowest NPP due to extreme aridity, while tundras are constrained by cold temperatures

Source-review note: The original graph labels its horizontal scale g C/m²/year, while the surrounding text gives biomass dry-mass units. The original graph and text are both retained; values must not be silently treated as the same measurement basis.

Productivity across terrestrial ecosystems

Tropical Rainforests : These ecosystems are among the most productive globally, attributed to consistent temperatures, abundant rainfall, and year-round sunlight. Their NPP ranges between 2,200-2,500 grams per square meter per year (g/m²/year).​

Grasslands : Productivity varies based on type:​

Savannas : Characterized by seasonal rainfall and sunlight, with NPP between 900-1,200 g/m²/year.​

Temperate Grasslands : Experience NPP ranging from 200-600 g/m²/year.​

Deserts : Due to extreme water scarcity, high temperatures, and nutrient-poor soils, deserts have very low productivity, with NPP between 50-200 g/m²/year.​

Temperate Forests : These forests exhibit distinct seasonal patterns, with productivity peaking during spring and summer when sunlight and rainfall are abundant. Their NPP ranges from 600-1,500 g/m²/year.​

Taiga (Boreal Forests) & Tundra : Boreal forests have moderate productivity due to cold temperatures and limited growing periods, with NPP between 200-600 g/m²/year. Tundras, characterized by extremely cold temperatures, short growing seasons, and permafrost, have very low productivity, with NPP ranging from 50-200 g/m²/year.

Aquatic primary production

Aquatic ecosystems, particularly oceans, contribute approximately half of the world's NPP, primarily through the activity of phytoplankton. Large seaweeds also play a role. The productivity of aquatic ecosystems is often limited by the availability of nutrients such as nitrogen, phosphorus, and iron.​

Freshwater and wetlands

Freshwater Ecosystems : Including rivers and lakes, these ecosystems exhibit highly variable productivity depending on nutrient levels, temperature, and light availability. Their NPP ranges from 50-1,500 g/m²/year.​

Wetlands : Due to the constant availability of water and nutrients, wetlands are highly productive ecosystems. They often serve as biodiversity hotspots and significant carbon storage areas, with NPP between 1,000-2,000 g/m²/year.​

Marine ecosystems

Coral Reefs : Among the most productive ecosystems per unit area, with NPP ranging from 2,000-5,000 g/m²/year.​

Estuaries : Highly productive due to nutrient availability and sunlight, with NPP between 1,500-3,000 g/m²/year.

In general, primary production is highest in tropical rainforests and progressively decreases toward the poles. The productivity of the open ocean is very low, approximately equivalent to that of the Arctic tundra.

Chapter 6 reading order

1. Energy Flow in Ecosystems: Processes and Thermodynamic Laws
2. Energy Flow Models: Single Channel, Y Shaped and Universal
3. Biomass: Types, Accumulation and Energy Uses in India
4. Ecosystem Productivity: Primary, Secondary and Influencing Factors
5. Methods of Measuring Primary Productivity
6. Primary Productivity Patterns in Terrestrial and Aquatic Ecosystems