What is the Difference Between Gross Primary Productivity and Net Primary Productivity

The main difference between gross primary productivity and net primary productivity is that the amount of carbon fixed during photosynthesis by all producers of the ecosystem is the gross primary productivity, whereas the amount of organic material available to support consumers is the net primary productivity.  

Gross primary productivity and net primary productivity are two parameters of primary production. Primary production refers to the synthesis of organic compounds from carbon dioxide in a process called photosynthesis.     

Key Areas Covered

1. What is Gross Primary Productivity
– Definition, Features, Importance
2. What is Net Primary Productivity
– Definition, Features, Importance
3. Similarities Between Gross Primary Productivity and Net Primary Productivity
– Outline of Common Features
4. Difference Between Gross Primary Productivity and Net Primary Productivity
– Comparison of Key Differences

Key Terms 

Gross Primary Productivity, Net Primary Productivity

What is Gross Primary Productivity

Gross primary productivity (GPP) is the amount of chemical energy or the carbon biomass produced by the primary producers at a given period. However, some fraction of this energy is used by primary producers for cellular respiration. Net primary production is the remaining fixed energy. Plants produce chemical energy, converting light energy through complex processes called photosynthesis. Subsequently, it fixes carbon dioxide into sugars. The activity of heterotrophic organisms requires sugars. They are used in various cellular requirements, such as building structures and functioning. In addition to the fixation of carbon, plants use water for the reactions of photosynthesis. 

Figure 1: Gross Primary Productivity

Furthermore, plants are responsible for producing most terrestrial gross primary production. It resembles the 17% carbon of the atmosphere. Respiration is the process of removing the assimilated carbon in the form of carbon dioxide into the atmosphere. 

What is Net Primary Productivity

Net primary productivity (NPP) is the rate of organic matter used by primary producers. It uses the remaining fixed chemical energy after respiration for the consumers. The remaining chemical energy is important for the growth and reproduction of primary producers. Also, it is available for the consumption of herbivores. Then, it passes through food chains from primary consumers to secondary consumers. Net primary productivity is typically expressed as a mass per unit area per unit time interval. Therefore, it is the mass of carbon per unit area per year.

Figure 2: Lake Metabolism

Similarities Between Gross Primary Productivity and Net Primary Productivity

• Gross primary productivity and net primary productivity are two types of primary production in plants.
• They are the amount of organic compounds produced by primary producers. 

Difference Between Gross Primary Productivity and Net Primary Productivity

Definition

Gross primary productivity refers to the quantity of carbon fixed by all producers in the ecosystem during photosynthesis. At the same time, net primary productivity refers to biomass or energy accumulation rate.

Rate

Gross primary productivity is the rate of organic matter formed by producers, while net primary productivity is the rate of organic matter used by primary consumers.

Dependence

Gross primary productivity depends on the amount of photosynthetic area and photosynthetic efficiency, while net primary productivity depends upon the rate of photosynthesis and respiration.

Biomass

Gross primary productivity is the total biomass produced during photosynthesis, while net primary productivity is the net gain of biomass after respiration use.

Conclusion

In brief, gross primary productivity and net primary productivity are two parameters of primary production. They determine the amount of organic compounds produced by primary producers. Gross primary productivity is the rate of organic matter formed by producers. It depends on the photosynthetic area and photosynthetic efficiency. However, it is the total biomass produced during photosynthesis. In comparison, net primary productivity is the rate of organic matter consumers use. It depends on the rate of photosynthesis and respiration. Also, it is the net gain of biomass after respiration use. Therefore, the main difference between gross primary productivity and net primary productivity is the amount of organic matter.  

References:

1. Lemmons, R. (2023, August 7). Gross primary production – global climate. Climate Policy Watcher. https://www.climate-policy-watcher.org/global-climate-2/gross-primary-production.html
2. Net primary productivity. Biology Articles, Tutorials & Dictionary Online. (2023a, May 29). https://www.biologyonline.com/dictionary/net-primary-productivity

Image Courtesy:

1. “Kelp forest Otago 1s” By Muu-karhu – Own work (Public Domain) via Commons Wikimedia
2. “Lake metabolism cross section” By Jayzlimno – Own Work (CC-BY SA 4.0) via Commons Wikimedia