The ideal mulch for Florida’s sandy soil is living roots, a combination of grasses, weeds and herbs kept above 6 inches. Tall living mulch is a carbon drip system for what’s living in soil the soil life feeds and sustains the tree and provides the home for soil life like fungi and bacteria. Most weeds that grow in Florida attract and are home to beneficial insects. This perfect nutrient cycling system along with the cation exchange which will naturally bind nutrients and pollutants in a stable matter that will not easily leach into the environment.
Most members in cities don't have the option to let weeds grow over 6 inches, that is a code violation. Just like the Demeter certification system you chose restricts you from bringing in resources from off-farm, they can't grow weeds. No organic material source is higher in carbon than woody material, no weed, grass, or plant comes close.
There is no plant based carbon mulch that feeds the tree unless you are mixing synthetic fertilizers in it. The synthetic fertilizers will mostly pollute your yard and leach into the environment and this will stop natural nutrient cycling. Plant carbon feeds the soil biology.
Definitely not true. Any plant based mulch will recycle nutrients in the material back into the soil with no need for synthetic fertilizer. That is a natural process which happens in nature all the time. Mulch as it decomposes is a microcosm of life and is in fact an ecosystem of it's own with macro/microorganisms including bacteria, fungi, nematodes, protozoans, arthropods, insects, even snakes, lizards, toads, moles. The life itself which is in the mulch as it decomposes represents to a large extent the source of nutrients which will feed the tree. The life is cellular and contains all the components of life, the dead bodies of micro and macro life and their excrement. That is also what happens in natural forest systems we can observe any time.
Having a tall living mulch will trigger the cation exchange and build soil. Cation exchange happens under tall grass at soil levels. Mulch or plant carbon added in small increments every other week are an excellent way to provide a perfect environment for trees to thrive. A high quality compost is best for speeding this process. I have found biodynamic manure compost tea sprays are great for building soil thru the cation exchange.
Well first you say only roots can supply fertility then just small amounts of mulch. What I see is that larger amounts of mulch combined with macro and micro life does generate compost in place. When it rains, the composting mulch washes down obviating the need to prepare and spray manure or compost teas. Eventually shade from well grown trees will reduce if not eliminate most plants/weeds unless they are adaptable to shade, and leaf fall and pruning will begin to accumulate mulch on their own as if in a forest so why not jump start the process?
On my plantings I use mulch but also plants adjacent and far between trees, a full ground cover relying on legumes and so I am working with both ideas, one doesn't mean you can't do both.
The cation exchange will not happen under a thick layer of woodchips as they need grass roots and fungi to bind the organic matter and nutrients into soil structures. Eventually the carbon from thick mulch will get into the soil with the help of worms, rain and segregation but this is easily leached and will not build stable organic matter in soil. Living root system do a much better job at putting carbon and biology into the ground and for building soil thru the cation exchange. These are facts.
Cation exchange can happen or be improved absent any living plants or roots at all. Cation exchange can be simply from clay fractions or organic matter such as compost. There is no reason to say that thicker mulch would prevent cation exchange fro happening, would not build stable organic matter, or let it leach out. Mulch builds organic matter no different from any other organic matter.
Fungi happen to love mulch it is their food. Macro and micro life of all types consume organic matter and mulch, even thick mulch will form soil structures and build organic matter in soil. Organic matter from mulch will not leach any differently from organic matter from plant roots. One benefit of plant roots is that they advance down into the soil and is why I do use plants even trees and bananas since they have the most aggressive roots. I even use root crops which I can make productive use of. As root crops get harvested some deeper soil mixing happens for free.
However, my main complaint with the ideas you put forth is the dogmatic approach. Likely what you are saying is a result of the constraints imposed by your certification which limits off-farm inputs. That constaraint is your choice but isn't necesarily the only or possibly even the best way. It is your way and you are certainly free to do as you please.
Using mulch if ordinary precautions are followed does no harm, it has always been known to be beneficial.
Using mulch, even thick mulch definitely does not mean having no support plants/weeds/trees along with the mulches. You can have it both ways. Mulch does not have to be thin to work, it can be thick as well and many have proven that. I see mulch as being an entire ecosystem which produces as much as it recycles and works as an edge against sun, heat and evaporation, and a way to prevent unwanted plants so that more productive plants can be utilized.