Management rules and external factors - INRA Montpellier

Management rules and external factors - INRA Montpellier

Some final comments

Key problems identified as a consequence of implementing a DMM in the HySAFE

model :

Some rules will make comparisons of different scenarios very difficult for technical

reasons (e.g. unpredictable length of the tree rotation; unpredictable number of

trees in the final stand).

• Some rules need that we simulate a stand of trees, not an average tree.

• Rules based on NPV calculations are probably not playable (see below) 1

• Many rules need state variables that are probably unrealistic

• Many rules require a weed/grass/shrub component on the tree-row.

• Some rules need a fallow module in HySAFE…

1 Most rules based on NPV values are probably not playable : the operation cannot be rated by NPV values at the

time of applying the rule, as the impact of the action will only be effective during the following years. Therefore, a

« Valeur d’Avenir » value (the sum of all discounted cost and revenues expected after the current date until the tree

harvest) would be a better criterion. But the calculation of this criterion is impossible at the current year, as it would

require full runs of the model for the different options until tree harvest time (and many more runs as new choices

will occur later, including for the same rule). I am afraid an economic management rule is therefore not

possible at the year time step for most operations (pruning, thinning, fertilising, etc…).

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