calculate_chi_o: Calculation of chi_o

In oscarperezpriego/ETpartitioning: Partitioning of eddy covariance ET into flux components

Description

Calculation of chi_o (see Wang et al., 2017; Plant Nature).

Usage

calculate_chi_o(data, ColPhotos, ColVPD, ColTair, C, Z)

Arguments

data	Data.frame or matrix containing all required variables.
ColPhotos	column name of numeric vector containing time series of photosynthesis data (umol CO2 m-2 s-1)
ColVPD	column name of numeric vector containing time series of vapor pressure deficit (kPa).
ColTair	column name of numeric vector containing time series of air temperature (deg C).
C	Empirical coeficient for C3 species.
Z	Z- numeric value defining elevation (km).

Details

the following metrics are calculated:

logistic_chi_o:

logistic_chi_o = 0.0545*(Tair_g-25)-0.58*log(VPD_g)-0.0815*Z+C

chi_o <- exp(logistic_chi_o)/(1+exp(logistic_chi_o))

Tair_g and VPD_g are calculated based on the mean value of the growing period. The growing period is estimated as those periods over the 85 quantile of Photos.

Value

a numeric value:

chi_o

long-term effective "internal" leaf-to-ambient CO2 (r.u)

Note

chi_o is unitless. Photos is calculated based on night-time NEE partitioning approach (Reichstein et al., 2005).

References

Wang, H., I. C. Prentice, et al., (2017), Towards a universal model for carbon dioxide uptake by plants, Nature Plants, 3(9), 734-741.

Reichstein, M., et al. (2005), On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm, Global Change Biology, 11(9), 1424-1439.

Examples

## filter data for dry periods and daytime at DE-Tha in June 2014

calculate_chi_o(data= EddySample
,ColPhotos = "GPP_NT_VUT_MEAN"
,ColVPD = "VPD_F"
,ColTair = "TA_F"
,C = 1.189 ##<< Empirical coeficient for C3 species (see Wang et al., 2017; Plant Nature).
,Z=0.27)

oscarperezpriego/ETpartitioning documentation built on June 4, 2019, 12:13 a.m.