Nathan Blevins wrote:Should I just got with the black locust just in case? Since the black locust is so coppicing friendly, it may have multiple purposes. However, I fear that coppicing it would result in reducing the nitrogen fixation.
My understanding is that coppicing, pollarding, pruning, or cutting back a nitrogen fixer will stimulate an equivalent die-back in the root system. The root system (and the associated relationship with the nitrogen-fixing bacteria) is costly to the plant and it will abandon what it doesn't actively need to survive + regrow.
This sounds like a negative, however, when the roots with the nitrogen-fixing relationship are allowed to die-back, the nitrogen stored in those nodules is released and made available to the surrounding soil. It will likely be taken up by the fruit trees if the pruning of the nitrogen fixer is timed to coincide with their active growth (such as in spring).
I would imagine that a vigorous tree like black locust wouldn't mind being pruned at the start of its growing season (although it might be sub-optimal for using the timber for things like fence posts, when ideally you want as little sap as possible in the wood for longevity - sap = starches = insect food!).
I have also heard that nitrogen nodules are not usually made available to plants other than the host (unless actively transported, by the host, to other organisms via mycelia). The nitrogen is made available in other ways, such as the dropping of leaves, but more slowly. Due to this, coppicing a nitrogen-fixer might be the best way to utilise its nitrogen for nearby plants in your system.
I have nothing to back this up - it's just my understanding from conversation, reading and other media - so I would be proven wrong or to open up more discussion about this.