The activity of an ecosystem can be assessed by gross primary productivity (PPB), which corresponds to the total organic matter produced in grams over a period of time in a given environmental area:
PPB = mass of organic matter produced / time / area
Discounting from this total the amount of organic matter consumed by the community during this period in the breath (R), We have the net primary productivity (PPL), which can be represented by the equation:
PPL = PPB - R
The productivity of an ecosystem depends on several factors, among which the most important are light, water, carbon dioxide and nutrient availability.
In stable ecosystems, the production of (P) often equals the consumption of (R). In this case, the ratio P / R = 1 is worth.
Gross Primary Productivity (PPB) = Total Photosynthetic Rate
Net Primary Productivity (PPL) = PPB - Autotroph Respiration
Community Net Productivity (PLC) = PPL - Consumption by Herbivores
Ecological efficiency is the percentage of energy transferred from one trophic level to another in a food chain. In general, this efficiency is approximately only 10%that is, about 90% of the total energy available at a given trophic level is not transferred to the next, being consumed in the metabolic activity of the organisms at their level or lost as remains. In some communities, however, efficiency can reach 20%.