Equation For Net Primary Productivity

Updated September 30, 2021

By Marina Somma

Reviewed by: Sylvie Tremblay, M.Sc. Molecular Biological science and Genetics

Plants, algae and all organisms that utilise photosynthesis to produce free energy back up the vast bulk of life on our planet. Photosynthesis allows these organisms to produce organic matter using sunlight as their primary energy source. Because they produce energy in the nutrient web, researchers refer to these organisms as producers and study how much production occurs in a given area by calculating net primary productivity.

How Plants Produce Nutrients Using Photosynthesis

Before delving into how researchers summate net productivity, you should empathize how plants use photosynthesis to produce new biomass. Plants can produce brand new molecules of carbohydrates, sugars and lipids (organic molecules) by using just inorganic compounds. They have in sunlight, h2o, carbon dioxide and various minerals and produce new biomass in the food web.

Withal, even though plants have in carbon dioxide during photosynthesis, they also expel some carbon dioxide through respiration in the absence of sunlight. You'll want to remember this later when calculating net principal productivity.

Cyberspace Chief Productivity Definition

What is net principal productivity? Cyberspace primary productivity (NPP) is the net amount of carbon produced past a plant or group of plants in a given period of fourth dimension. Carbon dioxide entering the constitute via photosynthesis and exiting the establish via respiration both factor into net productivity. Mostly, the components of net primary productivity include the biomass the plant produces, the secretions from the roots of the plants and any losses to herbivores.

How to Calculate NPP

To calculate NPP, you take the full amount of carbon that the plant fixes (or turns into usable material) and subtract the amount of carbon lost during respiration. The total amount of carbon taken in past the institute is known every bit the gross primary productivity (GPP), and the corporeality of respiration is known every bit R_a .

This gives you the net primary productivity equation:

NPP = GPP - R_a

How to Calculate NPP: Example 1

Though relatively simple when broken down into an equation, determining the net primary productivity can prove more challenging than plugging in a few numbers. No matter how exact y'all continue your experiment, y'all will have a hard time factoring in any energy that the establish produced to sustain itself, and you also won't be able to factor in whatever potential losses to small-scale insects or other invertebrates.

With that in mind, scientists can perform experiments to come as close to the correct net productivity as possible. In ane blazon of experiment testing the net productivity of algae in a swimming, researchers use glass bottles and samples of h2o. They exam the amount of dissolved oxygen prior to the experiment, seal and place the bottle dorsum in the water, and and then examination the oxygen once more after a period of time.

Past taking the final amount of dissolved oxygen from the canteen and subtracting it by the initial amount, they can summate the net primary productivity.

How to Calculate NPP: Example 2

For terrestrial organisms, or those living on land, researchers by and large utilise the biomass of the plants to make up one's mind their net master productivity. However, as discussed previously, the verbal net productivity will differ slightly from these results, as minor factors such as insect consumption can touch the amount of biomass produced.

You lot could measure the net primary productivity of a corn found past planting a seed, assuasive the establish to grow for an allotted period of time, and then removing the constitute, including all leaves and roots, and allowing information technology to fully dry out to remove all water inside the establish. H2o volition increase the weight and skew your data. The total mass of the dried plant provides a skillful approximate of the net main productivity.