Forest for the trees

I am doing a lot of ecology reading right now, trying to figure out what happens when and why. Ecology is really complicated, and there's no nifty table that tells you what to program. Things are going to be a bit dodgy. (Awesome.)

My notes are an absolute MESS.

Here's what I've got:
- a list of native trees in Wisconsin.
- a list of native communities in Michigan.
- the sketchiest understanding of forest succession in the history of ecology.

Basically, a forest proceeds from grassland -> shrubland -> shade intolerant forest (aspen/pine) -> shade tolerant forest (usually maple mix in the fictional world of Minneconigan).

This is driven mostly by the relative shade tolerance/intolerance of the species involved.

But clearly, some sites do not progress beyond grassland. Or, rather, they progress to a mature prairie type grassland. Why? That's what no ecology text seems to want to tell me. I've been able to identify a few factors by looking around: rise and fall of the water tables can drown out trees. Beavers cut them down. Fire burns them. It looks like beavers were a much bigger presence I thought, both in actual tree removal and in creation of dams that created wetlands (or destroyed them, depending on whether the land was upstream or downstream of the dam).

So designing a model of progression is a bit iffy right now, because *everything* would proceed merrily to a maple-fir forest. Also, all shade tolerant species would grow in a mature forest, whereas usually it's a weird balance.

So I'm trying to tease out other factors that are decisive.
Other factors, arranged in what I'm hoping is descending order:
- soil moisture (saturated, wet, moist, dry, parched - I'm pretending this stays mostly constant right now, because I don't really understand how and when it changes)
- soil fertility (changes over time, but am pretending it doesn't, except on actively farmed land)
- soil depth (also changes over time)
- soil type (ie clay, loam, sand, loamy sand . . .)

It really tough, though, because many of the different types are pretty similar, except for a small difference, some not even easily codeable. So it's a case of trying to figure out how to manage all the data available, and make it realistic without being total overkill.

Fun fact of the day: As far as Catholic dietary rules are concerned, beavers are fish.