README.md

RapidACi

An R package for the batch treatment of Rapid carbon dioxide response curves (A-Ci) generated by the LI-COR® portable photosynthesis systems.

The Rapid A-Ci measurement method (RACiR™) can save a lot of time characterising photosynthetic capacity of multiple plants. However, this gain in time is rapidly lost during post processing following the response curve measurements to obtain the Vcmax and Jmax values, especially since this repetitive task can produce errors. This script was created to help with the analysis of hundreds of measurement files at once. It will automatically match empty chamber measurement files to A-Ci files. When the leaf area does not entirely cover the chamber opening, like in conifers, it will insert the real leaf area into the measurement files and extract recalculated measurement values before correcting the A and Ci values required to compute Vcmax and Jmax.

For more information on the Rapid A-Ci method (RACiR™), see Stinziano et al. (2017) and this video produced by LI-COR® Inc. For the application of this method to conifers, see Coursolle et al. (2019).

Note: the package works with the Excel files generated by the LI-COR® systems only (not the text files) which contain formulas that need to be recalculated when the surface areas are measured after the RACiR™ curves.

IMPORTANT: the actual version is not yet adapted for files produced by the LI-6400 model.

Installation

if(!require("devtools")) install.packages("devtools")    
devtools::install_github("ManuelLamothe/RapidACi")     

The package requires the tidyverse and XLConnect packages to work. The plantecophys package is recommended for the calculation of Vcmax and Jmax on the corrected values but is optional (another model could be prefered by the user)

if (!require("plantecophys")) install.packages("plantecophys"); library(plantecophys)

Usage

First step: Generate a list of files

LeafArea_df <- read_tsv("data/leafArea.tsv")   #optional

list_files <- build_list(path_to_licor_files = "data/",
                         pattern_empty       = "^(mpty)+.xls",      
                         pattern_rapidACi    = "^(fast)+.xls",      
                         pattern_standardACi = "^(slow)+.xls",      
                         pattern_dark        = "^(dark)+.xls",
                         sampleID_format     = "[:upper:]{3}_[:digit:]{3}",
                         timestamp_column    = "BN",
                         leafArea_df         = LeafArea_df)    

Second step: Use empty chamber measurements to correct A and Ci values

There are two possible scenarios. The simple scenario is when leaves cover the whole opening of the chamber, so no leaf area correction is required. The alternative, is when the measured leaf area is smaller than the chamber opening and/or when leaves are distributed in multiple layers (e.g. conifers) and a correction is thus required. Since leaf area (“Const_S”) is generally evaluated after the measurements, both the A-Ci measurement files and matching empty chamber files have to be modified with the correct leaf area and their values recalculated before proceeding to the A and Ci corrections. Similarly, if you use your own measures of respiration (from the measurements of the samples in a dark chamber), these values will also be recalculated according to the leaf area provided.

For the correction of A and Ci, we use the coefficients of the best fitting polynomial curve (up to the fifth degree, optional with the max_degree argument) on the empty chamber measurements. delta_max can also be changed from the default settings (0.05). Before doing this, we recommand the use of the function diagnose_sample to see the impact of a possible change.

results <- Rapid_aci_correction(list_files, 
                                delta_max = 0.05, 
                                max_degree = 3,
                                priority_curve = "positive")

To produce a diagnostic figure for all the files in results (in the figure/ directory):

for(i in names(results)) diagnose_sample(results, i)

3. Calculate Vcmax and Jmax

The plantecophys package by Duursma (2015) to calculate Vcmax and Jmax for each samples. The option *useRd* = TRUE let you use your own measures of respiration (missing values will be estimated).

# We recommand to launch the fitaci function with the *safely* function from the purrr package to produce a list of separated `result` and `error` elements. This prevent the script to fail in the presence of an erroneous sample.

X <- map(results, `[[`, "Raci") %>%
     map(safely(~plantecophys::fitaci(., useRd=TRUE, Tcorrect=FALSE)))

# to generate the A-Ci plots
map(X, "result") %>% compact() %>% walk(plot)     

# to see errors
map(X, "error") %>% compact() 

### See variables names in an Excel file generated by the LI-6800
get_fromExcel(list_files$path[1], show.variables = TRUE)

#MORE TO COME SOON!



ManuelLamothe/RapidACi documentation built on Oct. 30, 2019, 9:10 p.m.