APES 1.8 Primary Productivity - Exam Review

Typical units used for primary productivity

"grams" of biomass / [(area)(time)] "grams" of C / [(area)(time)]

Productivity is measured in units of energy per unit area per unit time

EX: kcal/m2/yr

High Primary Productivity

Ecosystems with high PP are usually more biodiverse (more div. of species) than ecosystems with low PP

NPP =

GPP - EUPR

EUPR =

GPP - NPP

GPP =

NPP + Energy Used for Producer Respiration

Generally, only 1% of all incoming sunlight is captured & converted into GPP via photosynthesis

Of that 1%, only about 40% (or 0.4% of total incoming solar energy) is converted into biomass/plant growth (NPP)

Gross and Net Primary Productivity

Producers typically capture only about 1 percent of available solar energy via photosynthesis. This is known as gross primary productivity, or GPP. About 60 percent of GPP is typically used for respiration. The remaining 40 percent of GPP is used for the growth and reproduction of the producers. This is known as net primary productivity, or NPP

Water availability, higher temperature, and nutrient availability are all factors that lead to high NPP

Shortage of any of these three factors will lead to decreased NPP Ex: Desert (low H2O & nutrients), Tundra (low temp & liquid H2O), Open ocean (low nutrients)

Net Primary Productivity (NPP)

The energy captured by producers in an ecosystem minus the energy producers respire

Trends in Productivity

The more productive a biome is, the wider the diversity of animal life it can support (high. biodiv.)

Ecological Efficiency

The portion of incoming solar energy that is captured by plants & converted into biomass (NPP or food available for consumers)

Gross Primary Productivity (GPP)

The total amount of solar energy that producers in an ecosystem capture via photosynthesis over a given amount of time

Respiration Loss (RL)

plants use up some of the energy they generate via photosynthesis by doing cell. respiration (movement, internal transportation, etc.); think of RL as taxes plant needs to pay

Primary Productivity

the rate at which solar energy (sunlight) is converted into organic compounds via photosynthesis over a unit of time

Net primary productivity is

the rate of energy storage by photosynthesizers in a given area, after subtracting the energy lost to respiration AKA the amount of energy (biomass) leftover for consumers after plants have used some for respiration; think of NPP as the actual amount of the plant's paycheck it keeps after taxes

Gross Primary Productivity is

the total rate of photosynthesis in a given area; think of GPP as the total paycheck amount the plant earns