A grower ask me the other week about if he maybe had pruned too much his truffle trees. He did it 2 years ago and yield dropped a lot last season and this season started poorly while other neighbor truffieres started with good fruitings.
Pruning is better to be done every year and light prune is better trying to remove less than 30% of branches. When we do a heavy pruning this may turn tree into a negative feedback due to hormones function:
Auxins (plant hormones) produced in the twig’s terminal buds stimulate root growth. Gibberellins (plant hormones) produced in the root tip stimulate canopy growth.
The tree balances root growth versus canopy growth by these hormones.
Excessive pruning may reduce auxins, slowing root growth, so decreasing gibberellins is followed by a decline in the canopy caused by the reduced root growth.