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Dyk, Bobby?
(mander.xyz)
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Hi, arborist here! Fallen leaves are generally pretty low in nutrients--trees send back as much as they can into the tree before dropping them. So, you probably don't need to fertilize shade trees whether they stay or go. The bigger issue is that removing a huge input of carbon into the soil leaves you with low organic matter and lowered ability to retain what nutrients do exist. This poor soil quality will stress your trees, but adding fertilizer doesn't address the root issue.
Fruit trees generally do need to be fertilized since fruits are much higher in nutrients and are not generally returned to the soil unless you're doing some kind of poo composting scheme.
Point of clarification: organic matter doesn't really retain the nutrients but acts as the slowly mineralized pool of nutrients associated with soil quality.
The way you describe it is similar to how a sponge works rather than a storehouse.
You are right, though, in that you don't need to fertilize trees for the most part. Forest soils are hilariously low in nutrients: TOC is around 1% and N is next to non existent (N is highly labile), while P and K are moderate to high. As a result, forests veg is most competitive in nutrient poor conditions. If you fertilize a disturbed area, you get a pile of weeds and grass that can set back your revegetation timeline because your desirable woody spp now have to out-compete them. This process still happens if you don't fertilize, but it's generally less pronounced and allows some woody plants to gain the foothold they need
I read a while ago that trees attempt to reduce competition by dropping their leaves to prevent saplings growing too near. Was that all bunk?
Some trees do a bit, I guess? Like, beech trees will release some chemicals to inhibit other plant growth, and iirc their leaves do that as they decompose, as well as the root system itself. But depends on the plant and mostly bunk I believe.
Thanks