Heartwood correction — tdm

The function corrects for the proportion of the probe that is installed within the non-conductive heartwood according to Clearwater et al. (1999). The function requires $\Delta T_{max}$, the probe length and the sapwood thickness. The correction is applied on the $\Delta T$ (or $\Delta V$) values and $K$ is recalculated accordingly. When an is.trex-compliant object is provided, the $K$ values for each method are determined (see tdm_dt.max.

tdm_hw.cor (input, dt.max, probe.length = 20,
            sapwood.thickness = 18, df = FALSE)

Arguments

input: A tdm_dt.max ouput or is.trex-compliant object of $\Delta T $ (or $\Delta V$) values containing a timestamp and a value column.
dt.max: Optional zoo object or data.frame (columns = “timestamp” or “value”) containing the $\Delta T_{max}$ when no is.trex-compliant object is provided.
probe.length: Numeric, the length of the TDM probes in mm.
sapwood.thickness: Numeric, the sapwood thickness in mm.
df: Logical; If TRUE, output is provided in a data.frame format with a timestamp and a value column. If FALSE, output is provided as a zoo vector object (default = FALSE).

Value

A zoo object or data.frame in the appropriate format for other functionalities. See tdm_dt.max for output specifications. All $K$ values for each method are provided when an output from tdm_dt.max was provided. If individual time series are provided for input and tdm_dt.max an alternative output is provided:

input: = $\Delta T$ input data.
dt.max: $\Delta T_{max}{\Delta Tmax}$ input data.
dtsw: Corrected $\Delta T$ data.
k.value: $K$ values calculated according to Clearwater et al. (1999).
settings: data.frame of the applied probe.length and sapwood.thickness

Details

The function applied the correction provided by Clearwater et al. 1999. $\Delta T$ (or $\Delta V$) was corrected (denoted as $\Delta T_{sw}$) for the proportion of the probe that was inserted into the conducting sapwood vs the proportion of the probe that was inserted into the nonconductive heartwood ($\gamma$ in mm mm-1). Together with $\Delta T_{max}$, $\Delta T$ was corrected according to the following equation: $$\Delta T_{sw} = (\Delta T~-~(1~–~\gamma) * \Delta T_{max}) / \gamma$$

$\Delta T_{sw}$ together with $\Delta T_{max}$ is then recalculated to $K$.

References

Clearwater MJ, Meinzer FC, Andrade JL, Goldstein G, Holbrook NM. 1999. Potential errors in measurement of nonuniform sap flow using heat dissipation probes. Tree Physiology 19:681–687 doi:10.1093/treephys/19.10.681

Examples

if (FALSE) {
#correct for probes being inserted into the heartwood
raw   <-is.trex(example.data(type="doy"),
          tz="GMT",time.format="%H:%M",solar.time=TRUE,
          long.deg=7.7459,ref.add=FALSE)
input <- dt.steps(input=raw,
                   start="2014-05-08 00:00",
                   end="2014-07-25 00:50",
                  time.int=15,max.gap=60,decimals=6,df=F)
input[which(input<0.2)]<-NA
input <-tdm_dt.max(input, methods=c("pd","mw","dr"),
                 det.pd=TRUE,interpolate=FALSE,max.days=10,df=FALSE)
output.data<-tdm_hw.cor(input,probe.length=20,
                   sapwood.thickness=18,df=FALSE)
plot(output.data$k.dr,col="orange")
lines(input$k.dr)
}