I've been using leaves as mulch my whole life, first in OH, now in AL. Totally agree, different leaves behave differently as mulch, even within a genus.
Not all oak leaves are the same. If they are totally flat, they seem to mat worse than the bigger ones with some curl to them. One general fact about any oak leaves is that they do take longer to decompose than most other leaves, mostly carbon, little nitrogen.
This is much more noticeable when gardening a "new" patch of ground, recently reclaimed from lawn, or otherwise very infertile ground. Used alone in a new bed like this, they can cause some chlorosis and slow growth. Not a terrible concern if you're a long-term-goal gardener, planting shrubs and perennials. Something you'd probably want to address with some added nitrogen in the spring if using annuals, or just impatient in general. (More below.) But after a year or more, assuming you have been adding enough organic matter periodically, so that there is a decent amount of microbial life and decomposers like worms in the soil, oak leaves start decomposing much more quickly.
Large amounts/percentage of walnut leaves can create problems for plants that are sensitive to juglone.
If leaves aren't either walnut or especially resistant to decomposing quickly like oak, and there are worms and/or smaller life forms from the decomposition crew, a couple feet of leaves will likely disappear over the course of winter. Yes, I meant to say feet, not inches. This is how mother nature does it in the forest, nobody rakes in there, and leaves disappear. The ground ends up being dark, spongy, full of healthy and fertile humus and microbial life. The same thing can happen in even the most modestly sized garden beds.
Matting and shedding water is a super way to zone cheat/push, keeping the ground temp from moderating too much, possibly preventing ground from freezing along the north/south border zones (Z6/7,) and being too soggy for marginally hardy plants regardless of the zone one is trying to push. A bit too cold + dry = possible survival. A bit too cold + wet = usually death via rotting. Should one find a mat of leaves in the spring, they can be fluffed, raked, possibly moved... and augmented with high-nitrogen sources such as grass from mower bag, kitchen scraps, anything with much more nitrogen than carbon.
As alluded to already, leaves are only one great source of organic matter for gardens. And unfortunately, only available once per year for most. Other forms of OM can be added to gardens, such as mulch, or composted in a pile or bin first and then added, to help increase the tilth and fertility of gardens. Different households have various OM, but common entities are kitchen scraps (that aren't bones, or anything very salty,) trimmings from yard plants (that don't have thorns,) mower bag (mow before grass shows seed heads if doing that,) straw, non-glossy paper/cardboard, pretty much anything that can decompose.
My style is to spread what I have when it presents itself, throughout the year. But any approach that results in a constant layer of constantly decomposing OM will help the soil to be in a constant state of improvement, provide all of the fertility plants need to thrive, keep the soil "alive," and help suppress weeds. Unwanted sprouts pull *very* easily from ground that has been gardened this way for a year or more. There is no form of mulching that will stop weeds permanently or completely.
Even if you go down the street in your town, you could find a patch of wildly different "dirt." But no matter what you find, or start with in your yard, it can and will be improved by adding OM. The amount, content, timing of which you'll get the hang of as you garden.
For more about soil microbiology in 'normal person terms,' this short video is priceless! (And so much easier to do on a small, personal property than the parts where she talks briefly about larger forms of agriculture.)
http://permaculturenews.org/20...
Happy decomposing and growing! The circle of life.
