CO2 transpiration modifier — fCO2_transpiration

Function describing the effects of elevated CO2 on transpiration.

Usage

fCO2_transpiration_mod(c_CO2, c_ref = 360)

Arguments

c_CO2: numeric Atmospheric CO2 concentration in ppm
c_ref: numeric Reference CO2 concentration in ppm.

Details

The function for the effect on transpiration is from equations (2-6) in Kruijt et al.

It appears in this paper that there is a small formal mistake in said equations. With the stated values, it is not possible to reproduce the tabulated values of $c$ close to 1, as in their table 3. Instead, we conclude that equation (4) should read:

  c = 1 + s_gs * s_T * F_T * deltaCO2

with the multiplicative terms giving small negative numbers. The factors $s_gs$, $s_T$ and $F_T$ for grasslands are taken from pages 260 and 261 in Kruijt et al. where we averaged over the stated ranges to get:

  c ~= 1 + 0.0001 * deltaCO2

References

Kruijt B, Witte JM, Jacobs CMJ, Kroon T (2008). “Effects of Rising Atmospheric CO2 on Evapotranspiration and Soil Moisture: A Practical Approach for the Netherlands.” Journal of Hydrology, 349(3), 257–267. ISSN 0022-1694, doi:10.1016/j.jhydrol.2007.10.052 , https://www.sciencedirect.com/science/article/pii/S0022169407006373.

Examples

fCO2_transpiration_mod(420)
#> [1] 0.994
# The modifier is always relative to *c_ref*. This returns 1.
fCO2_transpiration_mod(420, c_ref = 420)
#> [1] 1