stomatal.sensitivity {bigleaf} | R Documentation |
Stomatal Sensitivity to VPD
Description
Sensitivity of surface conductance to vapor pressure deficit.
Usage
stomatal.sensitivity(data, Gs = "Gs_mol", VPD = "VPD", ...)
Arguments
data |
Data.frame or matrix containing all required columns |
Gs |
Surface conductance to water vapor (mol m-2 s-1) |
VPD |
Vapor pressure deficit (kPa) |
... |
Additional arguments to |
Details
The function fits the following equation (Oren et al. 1999):
Gs = -m ln(VPD) + b
where b is the reference surface conductance (Gs) at VPD=1kPa (in mol m-2 s-1),
and m is the sensitivity parameter of Gs to VPD (in mol m-2 s-1 log(kPa)-1).
The two parameters b and m are fitted using nls
.
VPD can be the one directly measured at instrument height, or the
one at the surface, as returned by surface.conditions
.
Value
A nls
model object containing (amongst others) estimates for the mean
and standard errors of the parameters m and b.
References
Oren R., et al. 1999: Survey and synthesis of intra- and interspecific variation in stomatal sensitivity to vapour pressure deficit. Plant, Cell & Environment 22, 1515-1526.
Novick K.A., et al. 2016: The increasing importance of atmospheric demand for ecosystem water and carbon fluxes. Nature Climate Change 6, 1023 - 1027.
See Also
Examples
## calculate Ga, Gs, and the stomatal sensitivity to VPD for the site FR-Pue in
## May 2012. Data are filtered for daytime, sufficiently high ustar, etc.
FR_Pue_May_2012_2 <- filter.data(FR_Pue_May_2012,quality.control=TRUE,
vars.qc=c("Tair","precip","H","LE"),
filter.growseas=FALSE,filter.precip=TRUE,
filter.vars=c("Tair","PPFD","ustar","VPD"),
filter.vals.min=c(5,200,0.2,0.3),
filter.vals.max=c(NA,NA,NA,NA),
NA.as.invalid=TRUE,quality.ext="_qc",
good.quality=c(0,1),missing.qc.as.bad=TRUE,
precip="precip",tprecip=0.1,precip.hours=24,
records.per.hour=2)
Ga <- aerodynamic.conductance(FR_Pue_May_2012_2)
Gs <- surface.conductance(FR_Pue_May_2012_2,Ga=Ga[,"Ga_h"])
stomatal.sensitivity(FR_Pue_May_2012_2,Gs=Gs[,"Gs_mol"],VPD="VPD")