1) natural process during which a mature tree reduces its crown and increases its girth to consolidate resources and increase longevity. 2) the deliberate process of reducing tree height to mimic natural processes.
Merriam-Webster Online Dictionary
retrenchment (noun) - reduction curtailment , specifically a cutting of expenses
retrenchment (Wikipedia)
Retrenchment (French: retrenchment, an old form of retranchement, from retrancher, to cut down, cut short) is an act of cutting down or reduction, particularly of public expenditure.