Whilst visiting Cambridge during November of last year, standing proudly outside a cathedral was a huge horse chestnut. Looking at its form, we can see how it has maintained a very full crown (likely due to the lack of competing trees, and its partially exposed setting), though some of its lower-most lateral limbs, over time, have subsided until they have reached the ground. The ground is now acting as a natural ‘prop’ of sorts, keeping the limbs free of any significant mechanical load and thus enabling their retention.
I have seen this before with horse chestnut, though only on old pollards down in Christchurch, Dorset (from memory) by one of the canals. The weight (and compressive forces of so many limbs trying to sit on one small ‘stool’) of the limbs had become so significant that they had subsided to below the water line. In that case, I suppose the buoyancy of the branches in water would have reduced some of the load. Unfortunately, I cannot find photos to show this example, though when visiting again I shall get some and post them here.
Arboriculture 