Overyield assumes trees regrow, and regrowth is managed by farmers.
Regrowth rate is conditional on the yield model you program into a crop template. So for example, if it takes 10 years for the tree to regrow, there will be a 10 year lapse between the first and second harvest, which you indicate within the "percent trees harvested by year" field.
In cases where sprouting is nonexistent, replanting operations will need to be added to the crop template to account for these costs:
Nursery cost (i.e. "unit cost") is only auto-calculated for the initial planting and second year replanting.
Additional costs for replanting in later years will need to be accounted for within custom replanting operations (e.g. a "grubbing & replanting" task), that you add to your crop template under Operations.
Within a grubbing and repanting task, you'll want to add genetic stock as an input (first you'll need to create a genetic stock item within your "Materials & Fuel" tab. Then you can attach this to the operation).
In cases where regrowth is hindered by livestock or other factors, you can account for this by decreasing the yield of the second harvest within your yield model (i.e. estimating the percentage of trees damaged by livestock, then subtracting this from the % trees harvested).
The other option is to create a tree loss event; however, loss events are cumulative. Once a tree is removed from the system through a loss event, it does not resprout.