ftemp_inst_vcmax {rpmodel}

Calculates the instantaneous temperature response of Vcmax

Description

Given Vcmax at a reference temperature (argument tcref) this function calculates its temperature-scaling factor following modified Arrhenius kinetics based on Kattge & Knorr (2007). Calculates f for the conversion

V = f Vref

Usage

ftemp_inst_vcmax(tcleaf, tcgrowth = tcleaf, tcref = 25)

Arguments

tcleaf

Leaf temperature, or in general the temperature relevant for photosynthesis (degrees Celsius)

tcgrowth

(Optional) Growth temperature, in the P-model, taken to be equal to tcleaf (in degrees Celsius). Defaults to tcgrowth = tcleaf.

tcref

Reference temperature (in degrees Celsius)

Details

The function is given by Kattge & Knorr (2007) as

fv = f(T, \Delta Hv) A/B

where f(T, \Delta Hv) is a regular Arrhenius-type temperature response function (see ftemp_arrh) with Hv=71513 J mol-1,

A = 1 + exp( (T0 \Delta S - Hd) / (T0 R) )

and

B = 1 + exp( (T \Delta S - Hd) / (TK R) )

Here, T is in Kelvin, T0=293.15 K, Hd = 200000 J mol-1 is the deactivation energy and R is the universal gas constant and is 8.3145 J mol-1 K-1, and

\Delta S = aS - bS T

with aS = 668.39 J mol-1 K-1, and bS = 1.07 J mol-1 K-2, and T given in degrees Celsius (!)

Value

A numeric value for fv

References

Kattge, J. and Knorr, W.: Temperature acclimation in a biochemical model of photosynthesis: a reanalysis of data from 36 species, Plant, Cell and Environment, 30,1176–1190, 2007.

Examples

## Relative change in Vcmax going (instantaneously, i.e. 
## not acclimatedly) from 10 to 25 degrees (percent change):
print((ftemp_inst_vcmax(25)/ftemp_inst_vcmax(10)-1)*100 )