Agree entirely with Eric's definition
I was off looking at pics of ice storm trees (beautiful pics!)
Dose is one of those concepts that as Arborists we get better at judging it the longer we work with trees and the deeper we become envolved with the trees we work on. The longer the period of observation on the effects of all kinds of impacts on specific species in specific environments the better able we are to predict what potential impacts say a 20% reduction on one elongated scaffold limb on say Euc camaldulensis (to cross over to another thread!) will have.
Arboriculture is not an exact science we just don't have enough reliable data over long enough periods and our subjects are so very variable, the natives I work on interact with their changing environment very differently to the exotics, and even within the same State the trees (same species) Eric works on are often very different in form and structural integrity to those I encounter up here...Grevillea robusta is an example that comes immediately to mind, does very poorly here, have only seen probably 5 good reliable specimens in 15yrs up here, yet the same tree does
visually very well in and around Brisbane...the further South you go the better it likes it...they look great along the banks of the Parramatta river.
Basic tree biology and physiology doesn't change no matter where you are but your understanding of how particular environmental conditions here you live and work effect the growth patterns and cycles of specific species will have a massive influence on how you interpret dose for each and every tree...I view dose as much as a measure of how much pressure a tree can sustain in the long term rather than applying it solely to the process of pruning...so that would include root loss through trenching, compaction soil contamination etc...alterations in water cycles, impervious cover etc...
I hope I have made at least some of that makes sense to you, and not merely made it more confusing!.