I do something a bit similar. I've built brush piles below my avocado and fig
trees that are planted on the steep hillside behind our place. The hill is quite steep, so my thinking is that any leaves and other organic material that falls from these trees will catch on those piles and contribute to soil health.
Additionally, it is a south-facing hill that gets full sun, so the sun just beats on the down-hill side of those trees. By building a brush pile below each of my trees (on the south side of them), it stops the sun from irradiating the soil, drying it out, and killing all the soil life. The soil is beautiful underneath those piles. The brush piles are anywhere from 2 to 4 feet tall. Some of them are 5 years old now, and I have to continually add new branches and additional organic matter to the top of them, as everything is slowly breaking down. I would imagine that they contribute significantly to the fungal network beneath the trees.
That would seem to me to be one of the most significant benefits of your brush berm: that you'll really
feed the
fungi all along the length of your pile.
"The rule of no realm is mine. But all worthy things that are in peril as the world now stands, these are my care. And for my part, I shall not wholly fail in my task if anything that passes through this night can still grow fairer or bear fruit and flower again in days to come. For I too am a steward. Did you not know?" Gandolf