Allocation to fruit production

[davidorme]

The pyrealm package doesn't currently include reproductive tissues in its allocation model. It should do, but isn't there yet. For the moment, we need to handle allocating carbon to reproductive tissue production within VE. We need to define:

• The amount of reproductive tissue on a given stem. We'll start with having a simple fixed fraction of the leaf mass - that then scales with crown area.
• The turnover of that tissue - a proportion of the tissue that is actively lost to the ground.
• Propagule mass - we can then actually calculate a number of fruit.

I don't know if @TaranRallings cares about individual fruits - and he'd also like more than just one gigantic pot of "reproductive tissues", but that at least starts to populate a seedbank.

At the start of the simulation, the existing stems are assumed to have fruit but then at GPP allocation, we need to allocate new fruit costs as the canopy grows and turnover costs.

That's awkward:

• We can topslice the GPP to allocate to turnover in the known standing mass, but...
• until we calculate DeltaDBH, we don't know the change in leaf mass and hence the GPP required for new fruit.
• I think the easiest solution for now is to impose a delay - new canopy mass is fruitless and then topslice the next GPP with a fruit growth cost from the last iteration. That's hacky but has some biological plausibility. I think the alternative would be that we'd have to iterate the allocation process somehow to solve "deltaDBH that gives leaves enough GPP spare to grow the fruit added to the canopy", which seems worse given we'll have to do this properly at some point!

Note

• These will be global constant standing fruit mass. No differences in propagule strategy or seasonality etc. Gotta start somewhere

[TaranRallings]

Sounds like a reasonable start to me. I don't think I need individual fruits, we'll just need to navigate some relationship between fruit mass:seedmass.