Figure 20.2 Harvesting primary productivity. Net primary productivity is commonly measured by harvesting a defined area of an ecosystem at the end of the growing season and determining the accumulated biomass of producers. This technique can be used on (a) small scales, such as by these students, who are measuring the aboveground biomass of plants, or on (b) large scales, such as the harvesting of crops in a field.

Photos by (a) Jamie Shady and (b) Leonid Shcheglov/Shutterstock.