Solar Radiation and Productivity in Tropical Ecosystems

J. L. Monteith

Thermal Dynamics Law

• First Law of Thermal Dynamics: Energy conservation

Rn=LE + H + G+A

• Second Law of Thermal Dynamics: Production of “useful” energy must be accompanied by simultaneous “waste” of heat.

Components of Efficiency

ε=εgεaεsεqεiεdεr

Where the components include geometric, atmospheric, spectral, quantum, interception, diffusion and respiration efficiencies

Geometric efficiency

Atmospheric Efficiency

Spectral Efficiency

• PAR to total radiation ratio: 50%

Quantum Efficiency

• Theoretical maximum: 1 Carbohydrate need 10 quanta.

215.0)106.3(10

107.719

19

q

Diffusion Efficiency

IbaP

/

1

Interception Efficiency

Respiration Efficiency

10/2}00375.0625.0{1 Tq P

W

W: standing dry weight (g/m^2)P: photosynthesis rate (g/m^2/day)