What are these?

[Hodge]

 

I was working at a property today and got chatting to the neighbour who was a retired arborist and he showed me something very interesting from various tree root systems that had failed during storm Arwen. The ones in the picture are from Oak and Beech. The are quite fascinating up close. Any ideas as to why these form and what they are? Some of them I have seen before when the roots squeeze through rocks but some of these are so strange.

 

[Bob Morris]

Maybe formed by root rot nematodes.

[petercb]

Look like root nodules, form when there is a lack of nitrogen so plant/tree forms a relationship with a bacteria which can absorb nitrogen from the atmosphere which is then used by the plant/tree to make proteins if i remember correctly.