All that you say, Lorn, could very well be true. I just don't know. There certainly are a lot of terpenes and other resins in conifers. I never looked at it all from the point of possible negative impact on soil microbes, et al; only that those resins and lignins would be more resistant to breakdown. Most people want there mulch to last as long as possible. Good for you that you don't!
What an interesting topic this is coming to be. I am going to post a similar question on a private list I belong to, where a professor emeritus frequents and would know the ins and outs, I think. Will post back here with the answers.
