Thanks mrtree, those are good questions. Those are better questions than I have answers at this moment! My main role at the TCI events up to this point has simply been to express a cautionary note based on the limited dissections I've done on injected trees and to encourage others: proponents, skeptics, and even-handed practitioners to do more evaluation of the effect of the treatment method and the formulated material on the tree. And some of the companies are doing just that, which is a big improvement.
The reminder of Anantha's comment is good, I will drop him a line. I had just figured that the decrease in wood density was due to reduced energy and biosynthetic reserves early in the growing season, due to impaired root and stem storage from partial girdling. But no, I don't know that.
In my observation of dissected trees, and this is not a big sample and does not cover all treatment materials and injection techniques, coalescence is not a big problem in current methods IF the manufacturer's guidelines are followed. Coalescence was indeed a big problem with the old high-pressure systems. Again in my limited observation, more damage can occur from techniques that don't use drilling but instead use a needle that introduces treatment materials into a reservoir formed by the separation of the bark (and phloem) from the wood, along the arc of the vascular cambium. That can be quite striking on the inside, but you don't see it without dissection.
The tradeoff of volume of treatment chemical is a tough one because the active ingredient is sometimes pretty phytotoxic or maybe the AI isn't too bad but it needs to be in very altered pH environment to be mobile. So that argues for larger volumes. And that brings up larger injuries and increased volume of cavitated sapwood...and then some folks want to crank up the pressure. And so it goes. The fundamental problem is that the transpiration stream is not designed to take up large molecular-weight organic compounds that are often not very miscible in neutral or slightly acidic water.
OK this helps me, thanks. I know I haven't answered the questions above, but they give me a piece to hop on to.
