Toward the end of summer I was cooking on the campfire in my friends woodland (the wood is predominantly Alder in a low-lying valley bottom with rivers either side) when I disturbed the loose soil with my boots, I noticed what my mind could only describe as a truffle, now I've not actually found a truffle in the wilds before (I haven't tried looking for them particularly hard either).. but considering the absurd prices you hear people paying for them I couldn't help get a little bit excited! - Not for the monetary value really, just that it was something new.
I dissected and quickly determined it probably wasn't a Truffle but it was interesting and new to me; it was an Alder root nodule which is Nitrogen fixing and improves the fertility of the soil, you can read about and see them here: https://en.wikipedia.org/wiki/Alder#Nitrogen_fixation
It was nice to learn that these two were a symbiotic relationship between the tree and something else, much like the truffle in the way if memory serves? (I think they are a symbiotic relationship between a fungi and the tree/root).
Turns out these root nodules were prolific beneath the woodland soil in this wood, so I learnt a few things and discovered that Alder improve your soil fertility