Types of Productivity

The productivity of an ecosystem can be broadly classified into 2 types as follows:

Primary Productivity

The production of biomass by autotrophs such as plants is called primary productivity. In primary productivity, plants use water and carbon dioxide in the presence of sunlight for photosynthesis and cooking. This results in the formation of both organic and inorganic substances. Primary productivity is also seen in some algae that use other chemical methods to obtain biomass. The tropical rainforest was the most productive ecosystem per unit area, the most productive ecosystem was the coral reef, and the least productive ecosystem was the deep lake ecosystem. Primary productivity depends on the types of plants growing in a given area. The annual net primary productivity of the entire biosphere is estimated at about 170 billion tonnes of organic matter. Of these 170 billion tonnes, the sea provides only 55 billion tonnes of productivity.

• Gross primary productivity: The total amount of fixed energy and organic matter consumed by respiration per unit of time in an ecosystem is called gross primary productivity (GPP). It can also be defined as the rate of formation of organic matter during photosynthesis. The GPP of an ecosystem depends on the rate of photosynthesis and environmental conditions. Plants use large amounts of GPP during respiration.
• Net primary productivity: As a significant amount of the GPP produced by the plants is consumed by plants themselves for respiration, the amount of energy that is left stored in plants is much less than GPP. This is termed as net primary productivity. This is the energy that plants can transfer to heterotrophs in the ecosystem. Thus, NPP can be defined as the difference between GPP and GPP lost during plant respiration.

Secondary Productivity

New organic matter is formed as heterotrophs or consumers consume organic matter from producers. The rate of formation of this biomass or organic matter is called secondary productivity. It is the result of energy transfer or energy flow in an ecosystem from one trophic level to another. It can also be referred to as the biomass growth of heterotrophs.

Productivity is an essential component of an ecosystem and is responsible for the sustenance of life in the ecosystem. The higher the productivity of an ecosystem, more is the energy available in that ecosystem. This energy that is available in the ecosystem keeps transferring from plants to animals and back to plants. The productivity of an ecosystem also influences the diversity of the ecosystem. An ecosystem with higher productivity has higher diversity as compared to an ecosystem with lesser productivity. The productivity of an ecosystem is responsible for the stability of an ecosystem.