Productivity Review and Productivity Review and CalculationsCalculations

Recap of Definitions!Recap of Definitions!Key term Definition

Productivity The total gain in energy of the producers.

Primary Productivity The total gain in energy/biomass per unit area per unit time.

Secondary Productivity

Production per unit area per unit time

Gross Productivity (GP) The gain in energy/biomass per unit area per unit time remaining after allowing for respiration losses which is passed onto the herbivores.

Gross Primary Productivity (GPP)

The rate at which energy/biomass is formed through photosynthesis

Net Productivity (NP) The gain in energy/biomass per unit time remaining after allowing for respiration (R) loses.

Net Primary Productivity (NPP)

The rate at which primary material is synthesised into animal tissue per unit area in a given time.

How do we calculate GPP?How do we calculate GPP?GPP = NPP + RGPP = NPP + R

How do we calculate NPP?How do we calculate NPP?NPP = GPP – RNPP = GPP – R

How do we calculate GSP:How do we calculate GSP:GSP = food eaten – faecal lossesGSP = food eaten – faecal losses

Or… NSP + ROr… NSP + R

How do we calculate NSPHow do we calculate NSPNSP = GSP – RNSP = GSP – R

Important CalculationsImportant Calculations

Some easy ones to start you off!Some easy ones to start you off!

What is the % energy from sunlight that is fixed as GPP What is the % energy from sunlight that is fixed as GPP if the total energy from the sun in 3 x 10if the total energy from the sun in 3 x 1066 and the gross and the gross primary productivity = 2.8 x 10primary productivity = 2.8 x 1044??

What is the GPP of an ecosystem if the NPP is 1660 What is the GPP of an ecosystem if the NPP is 1660 kJmkJm-2-2yryr-1-1 and the energy lost during respiration is 573 and the energy lost during respiration is 573 kJmkJm-2-2yryr-1-1 ??

What is the NPP if the GPP is 2700 kJmWhat is the NPP if the GPP is 2700 kJm-2-2yryr-1-1 and the and the energy used in respiration is 1850 kJmenergy used in respiration is 1850 kJm-2-2yryr-1-1??

Calculating Productivity ValuesCalculating Productivity Values

Now for some slightly harder ones!Now for some slightly harder ones!

Calculating Productivity ValuesCalculating Productivity Values

Energy Flow Diagrams

Information from energy flow diagrams can be used to calculate ecological efficiencies

Photosynthetic Efficiency = Net production ÷ Light Energy Absorbed

Ecological Efficiency is the net production of new biomass at each trophic level as a percentage of the

total energy flowing through that trophic level

Therefore, for photoautotrophs, photosynthetic efficiency is determined as:

Energy flow diagrams illustrate energy flow through communities and include values for respiratory losses and energy flow through

the decomposers

• Explain the meaning of the term Gross Primary Production• Explain the meaning of the term Net Primary Production• Calculate the Photosynthetic Efficiency of the phytoplankton

Use information from the energy flow diagram to:

Gross Primary Production is the total energy fixed by photoautotrophs during photosynthesis

Net Primary Production is the energy stored as biomass (gross production – energy lost as heat in respiration)

Photosynthetic Efficiency =

3.7 x 104

------------ x 100172 x 104

= 2.15%

GPP = 24 x106 kJ m-2year-1

Photosyntheticefficiency = 1.3%

NPP = 800 kJ m-2year-1

NPP = 200 kJ m-2year-1

NPP = 69.7 x 103 kJ m-2year-1

114 x 103 kJ m-2year-1