Energy transfer and its efficiency
As seen previously, plants produce a great deal of energy which is used up increasingly at every trophic level. This is the basis on which decisions are made in agriculture and rearing of domestic livestock.
In the wild, both plants and animals are subject to a lot of energy loss due to pests, physical activity or insufficient nutrients. This results in a relatively inefficient flow of energy between trophic levels. We think of this in terms of net productivity.
Net productivity is equal to gross productivity minus respiratory loss.
In both terms, productivity refers to the amount of leftover useful tissue such as cereals or animal flesh.
Gross primary production (GPP) is the chemical energy stored in plant biomass in a specific area or volume, while net primary production (NPP) is the chemical energy store in plant biomass after accounting for respiratory losses (R) to the environment.
This gives NPP = GPP – R
NPP can end up in plants’ own growth and reproduction or it can be taken up by herbivores and…