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I am leaning towards reccomending remove and replace. Mostly because silver maples are the second most frequent tree in the city, they account for about 12% of cities tree population, ... I left this info out on my original post because I thought it would make for better discusion.
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The decision depends on the assignment. If you are told to aim at some % of species, that changes everything. If you are told to assess the trees and not the population, then leave those sketchy at best numbers out of the "equation".
Most towns here have over 12% of some poor plants like defective bradfords and red maples, but removing and replacing would create holes in the treescape that would take years to fill. Species bias is seldom justified--bad silvers are due to bad mtc more than genetics.
How are the roots? I hope your assignment includes finding the flare, if reasonably possible.
"I would agree that rules can be broken given the right knowledge and experience but we need those rules to teach basic concepts."
"Rules are too strict for Mother Nature" A. Shigo
Concepts like "don't take off more than trees can tolerate" are better taught by reviewing a list of criteria rather than boxing the trainee's head into numerical rules. Once installed, these paradigms can rigidify and persist, limiting learning and giving every tree the same cookie-cutter treatments, much to their detriment.
"Rules are too strict for Mother Nature" A. Shigo
for reduction pruning, the 1/3 guideline is put in its place below:
1. Foundation. Cutting back to 100% sound wood is preferred. Some decay is tolerable if it is being walled off on the inside by black lines of wood preservative, and on the outside by callus—“scar”--tissue.
2. Vitality. Color, brightness, quality of buds, and growth rate show vitality.
3. Size of wound. The smaller, the sooner it will close and the less it will decay.
4. Thickness of “collar” at branch defense zone. The more incipient callus tissue there is, the sooner it will close.
5. Angle of attachment. A large lateral growing at a 90 degree angle may develop a “hollow elbow”, and not be very stable. Upright laterals make the best branches.
6. Angle of cut. Sloping cuts capture less spores, and shaded cuts are less likely to crack and decay.
7. Space to grow into and mature.
8. Size. One-third the diameter of the parent branch is a common guideline, sometimes exaggerated into “The One-Third Rule”, but size does not always matter more than the other criteria.
imho.
