Shiitake mushroom log softening

I was wondering if any of you knew how long it takes for the outdoor log technique with Shiitake mushrooms to 1) permeate the log with mycelia ("roots") and 2) soften the wood significantly? For instance, can a person break a 4 inch log that has had the mushrooms growing on it for a year or two?
Thanks!

Hi, David and welcome to Permies!
My husband and I grow shiitakes on logs outdoors. We plug the logs early march and can expect to get a handful in the fall of that same year. The next spring we will get a lot. The logs last years depending on the size...I have heard an inch of log per year...which seems about what we have experienced.. I am just now using the oldest logs that have stopped fruiting at about seven years, for buried wood projects, but just the outer inch or two is completely soft..they are still whole logs. We soak our logs to produce a flush of mushrooms. I think if you let them produce naturally the logs last longer but we don't have much sucess doing them that way. We buy dowel plugs from Field and Forest out of Wisconsin...they have been helpful answering our questions. There are a lot of growers in our area also who have been really helpful with local advice.

Thanks! What percent of the volume of the spent log would you say is mushroom roots? Do you know if these are edible for humans or animals?

Hi, David...Just yesterday I buried a couple spent logs from 2006 in a 'pie cherry' tree hole. I was able to bend them and break apart but there was no mycelium left that I could see although I assumed there was something good there for my soil. I think by the time the logs quit producing shiitakes on the surface of the log there is no mycelium in the log or only a bit. I am curious if you have some logs available or are intending to plug some? There are fungi folks on these forums who know much more than I ...so we will hope that they will answer your question.

Thanks again, Judith! I am not actually growing them, but doing research project you can see here: http://www.appropedia.org/Feeding_Everyone_No_Matter_What . Another question-do you have any idea what fraction of the dry mass of the wood is left after the mushrooms stop producing?