Dead-wooding 
This is the removal of the non-living branches/limbs from a tree. Common causes of deadwood are natural aging or external influences such as lack of light, disease or damaged roots. Dead wood does not necessarily mean your tree is unwell, however sometimes if there is excessive deadwood within the crown, it can be an indicator that there are internal health issues. It is always best to have it checked by a professional as soon as you can. Most of the time, it is impossible to remove every single branch with deadwood, so usually there will be a specified diameter that we cut to.