These Photo's were taken from two different places but similar Environments. These are photos of tree stem galls. The Galls were photographed on different species of tree, consisting of Scot Pine , European Beech , Sweet Chestnut and Oak trees.
All of these trees are growing within twenty metres of still water, and have probably been infected by an insect vector transmitting viral or bacterial infection to the Tree. The pathogen causes the Tree gall which allows a cosy little environment to develop where the bacteria can breed. I would imagine that the still water has something to do with the life cycle of the Gall Pathogen. When a healthy Tree becomes infected with Galls it rarely displays any stress at all and continues to grow as normal. But if a stressed Tree becomes infected then quite often the stem Gall increases in size and spread and the growth of the Tree is markedly retarded, here you can see a Sweet Chestnut ( Castanea sativa) (chestnut leaf placed on trunk for id.) that has grown in shade (stressful situation) almost completly ringed by the growth of a stem Gall, the Tree recognizing its plight has started to put out new growth just below the choking effect of the Gall in an attempt to produce foliage so that when the Gall completes its circular choking action the tree might survive.