how to check if a parameter affects an output

[SarahAlidoost]

I plotted the changes in LAI and TWLV (outputs of the leafdynamics model) with respect to variations in the parameters SPAN and TDWI for every test file in the PCSE test folder. The notebook is available here.

From the plots, it seems that the parameter SPAN does not affect TWLV , see plot 2.2. For LAI, after SPAN reaches a certain threshold, further changes do not appear to affect the output either, see plot 2.1. Is this expected behavior of the leaf_dynamics module?

Additionally, how do other parameters in this model (and in other modules) influence the outputs? It would be good to know this in advance when calculating gradients of an output w.r.t. a parameter.

[michielkallenberg]

@SarahAlidoost See here: #8 (comment) for an answer on LAI <-> TWLV in the unit test

[SarahAlidoost]

Update: while working on #55, we found that in root_dynamics,the gradient of TWRT wrt parameter RDRRTB is zero. I plotted the changes in TWRT (one of the outputs of the root_dynamics model) with respect to variations in the parameters RDRRTB for every test file in the PCSE test folder. The notebook is available here. From the plots, it seems that the parameter RDRRTB does not affect TWRT. See also this discussion.

[michielkallenberg]

Update: while working on #55, we found that in root_dynamics,the gradient of TWRT wrt parameter RDRRTB is zero. I plotted the changes in TWRT (one of the outputs of the root_dynamics model) with respect to variations in the parameters RDRRTB for every test file in the PCSE test folder. The notebook is available here. From the plots, it seems that the parameter RDRRTB does not affect TWRT. See also this discussion.

@SarahAlidoost I think this is issue is pretty similar to #8 (comment):
Most likely, the following applies:
TWRT represents the total root weight, including both living and dead roots. RDRRTB modifies the root death rate, but this does not change the total root weight, since TWRT is defined as the sum of both living and dead root biomass. I figure RDRRTB will affect WRT (weight of living roots) and DWRT (weight of death roots), but not TWRT.

[ajwdewit]

I think you are correct regarding the impact of the RDRRTB on the total weight of roots. It affects the distribution between dead and living biomass but not the total.