Tutorial

growR implements the grassland growth model ModVege. The basis of the model is thoroughly described by (Jouven, Carrère, and Baumont 2006).

In short, ModVege takes a values relating to daily weather conditions, the nutrition availability and water holding capabilities as well as the prevailing functional composition of plant population of the simulated site as inputs and uses them to simulate grass growth on a daily time step.

Functions and data provided by growR allow users to

The following section provides a step-by-step tutorial intended to show how growR can be used. Deeper insights can be gained by the vignette("parameter_descriptions").

Step 0: Goal of the tutorial

In this tutorial we are going to make use of the example input and reference datasets to go through the whole process of

  1. setting up all input files
  2. running ModVege simulations with the specified inputs
  3. have a look at the results
  4. change inputs and run a new simulation

Since quite a number of input files are required to even get started with growR, the package ships with example files for each of them. When following the tutorial, the reader will have an opportunity to inspect all of them and can use those as templates in order to create their own simulations with their own data.

When running simulations, data is loaded from and written to files. In the following, we assume that we are working in an empty directory of the filesystem and that this is the working directory for the running R sessions or Rscript commands. To be on the safe side, for this tutorial we will create a temporary directory working_dir. All necessary or created files are assumed to be located under this working directory.

working_dir = file.path(tempdir(), "growR_tutorial")
dir.create(working_dir)
setwd(working_dir)

Step 1: Setting up all input files

To help users having a somewhat clean directory structure, the function setup_directory() is provided. It also offers the option to copy all example files from the package directory into appropriate location in the newly created directory structure. Our first step is therefore to execute the following from an R session:

library(growR)
#> +---------------------------------+
#> | Welcome to growR Version 0.0.1! |
#> +---------------------------------+
# Check that working directory is correct
print(working_dir)
#> [1] "/tmp/Rtmp2BwUB7/growR_tutorial"
getwd()
#> [1] "/tmp/Rtmp2BwUB7/growR_tutorial"
setup_directory(force = TRUE)
#> [1] "Initialized directory structure in `.`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/posieux_weather.txt` to `./input/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/posieux_parameters.csv` to `./input/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/posieux_management1.txt` to `./input/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/posieux_management2.txt` to `./input/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/sorens_weather.txt` to `./input/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/sorens_parameters.csv` to `./input/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/sorens_management1.txt` to `./input/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/sorens_management2.txt` to `./input/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/posieux1.csv` to `./data/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/posieux2.csv` to `./data/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/sorens1.csv` to `./data/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/sorens2.csv` to `./data/`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/extdata/example_config.txt` to `.`."
#> [1] "Copying `/tmp/Rtmpynctq6/temp_libpath94ef49393008/growR/scripts/compare.R` to `.`."
#> [1] "Copied example files to respective directories."

We used force = TRUE here such that we can skip the safety prompt which would otherwise ask for confirmation.

Afterwards, check the working directory. You should find a couple of subdirectories and some files:

First, we’ll have a look at example_config.txt. We are later going to adjust and make use of this file for running our simulation in this tutorial. It contains information about the types of simulation we want to run and what input files should be used for each simulation. Have a look at its structure and compare it to the explanations given in the documentation of read_config().

As you can infer, in order to completely run a simulation, we require at least a parameter and a weather data file (the management file is optional). growR comes with example data for two real-world experimental sites: Sorens and Posieux, both in Switzerland. You can find the respective example parameter files at input/sorens_parameters.csv and input/posieux_parameters.csv. Likewise for the input/..._weather.txt and input/..._management1/2.txt files. Again, have a look at these files and the respective descriptions in WeatherData and ManagementData to familiarize yourself with the required data structures and the meaning of the different columns.

2. Run ModVege with the example configuration

Everything is now set up for us and we are ready to proceed with a simulation. Run:

environments = read_config("example_config.txt")

As you may have already seen from the documentation of read_config(), this reads in the given configuration file, skipping any lines starting with #. For each line, it then looks for the given input files and creates a [ModvegeEnvironment] object with the data from the corresponding files. These [ModvegeEnvironment]s are essentially data structures that hold all the information needed in order to run a ModVege simulation.

We are now ready to do so:

results = growR_run_loop(environments, store_results = TRUE)
#> [INFO]Starting run 1 out of 2.
#> [INFO][Run 1/2]Simulating year 2013 (1/3)
#> [INFO][Run 1/2]Simulating year 2014 (2/3)
#> [INFO][Run 1/2]Simulating year 2015 (3/3)
#> [INFO]Starting run 2 out of 2.
#> [INFO][Run 2/2]Simulating year 2013 (1/3)
#> [INFO][Run 2/2]Simulating year 2014 (2/3)
#> [INFO][Run 2/2]Simulating year 2015 (3/3)
#> [INFO]All runs completed.

This will simulate grass growth for every year in every environment present in environments. After some console output, we now have the results of these runs in the list results. Check the documentation of growR_run_loop() ro see how this list is organized.

Furthermore, the default value for write_files in growR_run_loop() is TRUE. This means that the results have also been written to files in the output directory.

3. Have a look at the results

Since we have the simulation results at our fingertips in our interactive R sessions, the quickest way to inspect them is through the results list. The output of

# Just print the first years of the first run (i.e. year 2013 at site Sorens)
results[[1]][[1]]
#> <ModvegeSite>
#>   Public:
#>     ABSDR: 0
#>     ABSDV: 0
#>     AET: 0.425137788528002 0.4583695833186 0.515292206584979 0.59 ...
#>     AgeDR: 503.61 505.1 505.96 510.44 516.05 519.75 520.81 523.24 5 ...
#>     AgeDRp: 2657.32101804528
#>     AgeDV: 503.61 505.1 505.96 510.44 516.05 519.75 520.81 523.24 5 ...
#>     AgeDVp: 402.971516618328
#>     AgeGR: 0 1.49 2.35 6.83 12.44 16.14 17.2 19.63 20.83 22.84 25.2 ...
#>     AgeGRp: 2611.14747753357
#>     AgeGV: 103.61 105.1 105.96 110.44 116.05 119.75 120.81 123.24 1 ...
#>     AgeGVp: 409.59851513876
#>     BM: 774.6427 773.271684397 772.483820568807 768.389958595924 ...
#>     BM_after_cut: 1070
#>     BMDR: 29.8917 29.847161367 29.8214928082244 29.6878925204435 2 ...
#>     BMDRp: 2.25091345308294
#>     BMDV: 296.751 295.42452303 294.662327760583 290.70206607548 28 ...
#>     BMDVp: 269.208204690527
#>     BMG: 448 448 448 448 448 448 448 448 448 448 448 448 448 448  ...
#>     BMGR: 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 ...
#>     BMGRp: 140
#>     BMGV: 420 420 420 420 420 420 420 420 420 420 420 420 420 420  ...
#>     BMGVp: 502.155806916888
#>     cBM: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  ...
#>     cBMp: 7236.91352648116
#>     clone: function (deep = FALSE) 
#>     cut_delays: 0
#>     cut_DOYs: 106 134 162 190 218 246 274 302
#>     cut_during_growth_preriod: TRUE
#>     cut_height: 0.05
#>     days_per_year: 365
#>     dBM: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  ...
#>     determine_cut: function (DOY) 
#>     determine_cut_automatically: function (DOY) 
#>     determine_cut_from_input: function (DOY) 
#>     dry_days_after_cut: 2
#>     dry_days_before_cut: 1
#>     dry_precipitation_limit: 1
#>     dry_window: NULL
#>     end_of_cutting_season: NULL
#>     ENV: 0 0 0 0 0.122 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  ...
#>     ENVfPAR: 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1  ...
#>     ENVfT: 0 0 0 0 0.122 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  ...
#>     ENVfW: 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1  ...
#>     get_management: function () 
#>     get_target_biomass: function (DOY, intensity = "high") 
#>     get_weather: function () 
#>     GRO: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  ...
#>     GROGR: 0
#>     GROGV: 0
#>     hvBM: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  ...
#>     initialize: function (parameters, site_name = "-", run_name = "-") 
#>     j_start_of_growing_season: 69
#>     LAI: 0.8651776 0.8651776 0.8651776 0.8651776 0.8651776 0.8651 ...
#>     LAIGV: 0.811104 0.811104 0.811104 0.811104 0.811104 0.811104 0. ...
#>     last_DOY_for_initial_cut: 150
#>     management: list
#>     max_cut_delay: 5
#>     max_cut_period: 55
#>     n_state_variables: 31
#>     OMD: 0.685348189289133 0.685491836840731 0.685573921772576 0. ...
#>     OMDDR: 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4  ...
#>     OMDDV: 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0 ...
#>     OMDG: 0.860279780783582 0.859802516526619 0.859527048566224 0. ...
#>     OMDGR: 0.89 0.889202204724409 0.888741732283465 0.8863429921259 ...
#>     OMDGV: 0.858298432835821 0.857842537313433 0.857579402985075 0. ...
#>     parameters: ModvegeParameters, R6
#>     PGRO: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  ...
#>     plot: function () 
#>     REP: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  ...
#>     run: function (year, weather, management) 
#>     run_name: -
#>     SENGR: 0
#>     SENGV: 0
#>     set_parameters: function (params) 
#>     site_name: sorens1
#>     ST: 3.61 5.1 5.96 10.44 16.05 19.75 20.81 23.24 24.44 26.45  ...
#>     state_variable_names: AgeGV AgeGR AgeDV AgeDR BMGV BMGR BMDV BMDR OMDGV OMDGR  ...
#>     STp: 3364.63
#>     target_biomass: NULL
#>     time_step: 1
#>     version: package_version, numeric_version
#>     weather: list
#>     WR: 160 159.805206625861 159.94517316524 159.850342649062 15 ...
#>     write_output: function (filename, force = FALSE) 
#>     WRp: 159.696976217117
#>     year: 2013
#>   Private:
#>     apply_cuts: function () 
#>     calculate_ageing: function () 
#>     calculate_digestibility: function () 
#>     calculate_growth: function () 
#>     carry_over_from_last_day: function () 
#>     current_DOY: 365
#>     get_start_of_growing_season: function (critical_temperature = 5, consider_snow = FALSE, critical_snow = 1) 
#>     initialize_state_variables: function () 
#>     make_header: function () 
#>     REP_ON: 0.653846153846154
#>     update_biomass: function () 
#>     vars_to_exclude: OMDDV OMDDR

might be a little overwhelming and not very helpful, though. A convenient way to quickly see what has happened is to plot the resulting grass growth curves. The [ModvegeSite] objects which are actually what’s stored in results provide a simple means of doing that through their plot() method.

For example, to see the growth curves for year 2013 at site Sorens we could do:

results[[1]][[1]]$plot()

The blue vertical lines in the top left plot indicate cutting events. They should coincide with the steps in the harvested biomass hvBM, bottom right plot.

Excellent! You have run your first ModVege simulation with growR!

4. Change inputs and run a different simulation

Now, for the sake of the example, let’s say that you want to check what the simulation would look like if both sides had a significantly lower nutritional index NI. First, check the current values of NI in the differnet parameter files (input/sorens_parameters.csv and input/posieux_parameters.csv). They should be 0.7 for both sites.

We want to investigate what the growth curves look like for different values of NI. For that purpose, we’ll focus only on the site Sorens and only on the year 2013 (just to keep the calculations required for the example quick).

One way to supply different parameters to the simulation, is by providing different parameter files. Copy sorens_parameters.csv twice and call the copies something like sorens_parameters_lowNI.csv and sorens_parameters_highNI.csv. In one of the files, change the value of NI to 0.5 and in the other, change it to 1.0.

Then, copy the example_config.txt file, give it a name of your choice (we’ll use NI_screening.txt here) and edit it such that there are only three uncommented lines. All of them should use site name sorens1 and only the year 2013. One of them should use the original sorens_parameters.csv file while the others should use the newly written parameter files with higher and lower NI values respectively. Since we now specify several runs with the same site name, we need to distinguish them by giving at least two of them a distinct run name as well.

When done, your new config file might look something like this:

# site name     # run name  # year(s)   # param file            # weather data          # cut dates
sorens1     -   2013    sorens_parameters.csv   sorens_weather.txt      sorens_management1.txt
sorens1     lowNI   2013    sorens_parameters_lowNI.csv sorens_weather.txt      sorens_management1.txt
sorens1     highNI      2013    sorens_parameters_highNI.csv    sorens_weather.txt      sorens_management1.txt

Be sure that the spelling of your file names is correct and consistent and that all the files reside in the correct locations (i.e. the input directory under our working directory).

If all seems fine, go for it (use the name of the config file you chose):

new_envs = read_config("NI_screening.txt")

And we’re ready to run and inspect our next run of simulations:

new_results = growR_run_loop(new_envs, write_files = FALSE, 
                             store_results = TRUE)
#> [INFO]Starting run 1 out of 3.
#> [INFO][Run 1/3]Simulating year 2013 (1/1)
#> [INFO]Starting run 2 out of 3.
#> [INFO][Run 2/3]Simulating year 2013 (1/1)
#> [INFO]Starting run 3 out of 3.
#> [INFO][Run 3/3]Simulating year 2013 (1/1)
#> [INFO]All runs completed.
# Plot all results
for (run in new_results) {
  print(run[[1]]$parameters$NI)
  run[[1]]$plot()
}
#> [1] 0.7

#> [1] 0.5

#> [1] 1

Jouven, M., P. Carrère, and R. Baumont. 2006. “Model Predicting Dynamics of Biomass, Structure and Digestibility of Herbage in Managed Permanent Pastures. 1. Model Description.” Grass and Forage Science 61 (2): 112–24. https://doi.org/10.1111/j.1365-2494.2006.00515.x.