What support species work for zone 4a upstate New York?

Hello!

I am working on a food forest / forest garden in upstate New York, but I’m from Hawaii so I’m not very familiar with this whole temperate eastern forest thing. Mostly I am trying to learn about what species may work as support species. What options are there as far as plants that can grow quickly and be chopped back to boost soil fertility? Are these methods (methods like chop n drop, pollarding of fast-growing pioneers, etc) even viable in this climate / environment? Also, when is the best time of year to do the chopping? Seems like the process of leaves dropping in the fall is essentially natures chop n drop mechanism of adding fertility to the soil, but everything I’ve seen says to prune in spring. Maybe someone can explain to me the best way to think about this or point me in the right direction.

More specific site background:
We are converting former pasture / semi wooded areas with varied topography but generally south facing gentle slopes, good draining soils w/ swales and hugelkultur. The project is almost 6 years old. I had only been working on it during some summers but recently moved up here year round so I’ll be fully invested in this project now. Many fruit trees and productive species were planted, things like pears, apricots, plums, apples, shipova, hazelnut, blueberries, currants, elderberry, seaberry, hops, haskap, serviceberry, bur oaks, Joel bush cherry, lingonberry, raspberry. They are doing fine, some better than others, but some of the trees in particular seem to be quite alone and in need of companions and support species.

The past 2 years the project has seen some mostly beneficial neglect due to covid, which allowed the system to advance mostly undisturbed. So coming back after that hiatus I’ve noticed that there are other “wild” trees moving in, things like poplar and cherry. Are these potential candidates for support species? I’ve read that species like birch, beech, fire cherry, and poplars, (all of which we have on site) are considered pioneers that quickly grow after a disturbance, which sounds promising as pioneer support species. We also have various maples, pines, etc. Does anyone have any experience using these or other plants as support species?

Thanks for the help.

I saw your thread in our Zero Replies Topics.

Here is a thread that might be of interest:

https://permies.com/t/164931/Zone-Support-Species-Chop-Drop

Maybe some of our helpful forum members will also after some suggestions.