d_climate               Climate input
d_parameters            Parameters input
d_site                  Site input
d_sizeDist              sizeDist input
d_species               Species input
d_thinning              Thinning input
i_output                Information about model outputs
i_parameters            Information about parameters
i_sizeDist              Information about size distribution parameters
prepare_climate         Subsets or replicate a climate data
prepare_input           Check and prepare input for running 3-PG model
prepare_parameters      Prepare parameters table
prepare_sizeDist        Prepare parameters table
prepare_thinning        Check and prepare management information.
r3PG                    Simulating Forest Growth using the 3-PG
                        Process-Based Vegetation Model
run_3PG                 Runs a 3-PG model simulation
