Parameterizing forest management in PATH

[JPrice]

We are currently transitioning from TELSA to PATH in our efforts to model forest dynamics. Natural disturbances are handled the same in both platforms, but management activities must be parameterized differently. In TELSA, management activities were captured by defining three sets of parameters:

1) the probabilistic transition (specifying from and to classes as well as TSD, but the probability didn’t matter)

2) defining the management system, where activity sets limit the (a) age range in which an activity can occur and (b) activity constraints specify the size range for a single instance of the management activity). And these systems are assigned to the specific cover type/planning zone combinations.

3) assigning activity group limits for each transition type in each planning zone (in our case, the total area of each planning zone to which a particular management activity can be applied in a single time step)

Therefore, we have obtained the following information for each planning zone: the management activities that occur in each cover type, including the age and size range for particular activities, and the total area in that planning zone to which a particular activity can be applied in a single time step. For instance, we know that a total of 500 acres can be selectively harvested on privately owned land (rather than 500 acres can be selectively harvested in the northern hardwoods on privately owned land).

However, management is parameterized more similarly to natural disturbances in PATH, with steps 1 and 2a above being captured in the transition information for each cover type in each planning zone (which are individual strata in PATH). Which warrants two questions:

1) How can the probability for each management transition be calculated given our information at hand (area of each cover type in each planning zone [area of each strata] and total area in a single planning zone to which an activity can be applied)?

2) Under the “Advanced” tab, do size distributions limit transitions similarly to assigning activity group limits in TELSA (step 3 above) or is this where we specify the size range for particular management activities as when setting up management systems in TELSA (step 2b above)? How is the information in the “Relative Amount” column used?

Answers to the above questions and any advice is most appreciated.

[leonardo-frid]

Question 1 – How can the probability for each management transition be calculated given our information at hand (area of each cover type in each planning zone [area of each strata] and total area in a single planning zone to which an activity can be applied)?

Answer: As you have done using TELSA, you can choose to use Area Limits (called Transition Targets in Path) to define how much area is affected by a particular management activity during each timestep. Transition targets can be set by transition group and are optional for each transition group. If you choose not to use transition targets you can instead set the probability by deciding what proportion of the total area eligible for the activity you would like to happen during each timestep. In this case the absolute amount of area undergoing the transition will vary over time as the eligible area will also likeley vary.

Question 2 – Under the “Advanced” tab, do size distributions limit transitions similarly to assigning activity group limits in TELSA (step 3 above) or is this where we specify the size range for particular management activities as when setting up management systems in TELSA (step 2b above)? How is the information in the “Relative Amount” column used?

Answer: This is where you set the size frequency distributions for both management activities and natural transitions and it only applies when you are running the model spatially. Note that for spatially explicit simulations, transition groups must have a size distribution defined to be simulated.

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