The rate at which food is manufactured by the producers in unit area in unit time is called productivity. There are following types of productivity:

  1. Primary Productivity

The rate at which solar energy is converted into organic energy by green plants or total food assimilation rate of producers is called primary productivity. Primary ,reproductivity can be measured in grams of carbohydrate produced per unit of land surface per year. Primary productivity is of two types

(a) Gross primary productisity: The total rate of photosynthesis or the total amount of organic matter fixed is called gross primary

productivity. It also includes the organic matter used up in plant respiration.

(b) Net primary productivity: The organic matter stored in plant tissues is called net primary productivity. The organic matter used up in the process of respiration is excluded from it. It is the food available to the consumers.

Relationship between the two types of productivity may well be understood by the following simple equations

Gross primary productivity = Photosynthesis + Respiration



Net primary productivity = Gross primary productivity—Respiration

  1. Secondary productivity

The amount of energy available to other trophic level i.e. the heterotrophs or the consumers is called secondary Productivity.

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