Wandering around a mulched orchard is always an adventure. In the early days of commercial mulching of citrus orchards, it wasn't uncommon to come across golf balls, discarded wallets, and all kinds of things you would not want in your orchard. This can still be a problem when the grower is not watching to make sure the loads are clean.
As the material settled in, over time more commonly, there would be the evidence of the decomposers - the fungi that breakdown the organic mulch into nutrients. It would show up in the fruiting bodies, like those below
The fruiting bodies would show up, but the real activity would be in the mulch itself. The decomposition is done with enzymes that are secreted into the mulch to breakdown the lignin and cellulose that make up plant based materials. When you dig into the mulch, you find the mycelial mats of those fruiting bodies. The fungus part that actually does the enzyme secretion and nutrient absorption. These enzymes also help control disease organisms like Phytophthora.
But sometimes wandering the orchard, you come across odd things, like slime molds
And then you come across what looks like trash. At this stage of commercial mulching, it's hard to find trash in good quality mulch. Recently, I found some what looked like plastic trash in an orchard. This turns out to be a fungus, though. A stinkhorn. Another decomposer good for plants and the soil.
