I'm no expert but I will try to answer your questions anyway.
Andre LaS wrote:
Now my questions begin:
1) After These beans/peas/clovers grow and die in the soil, will the soil still have the Rhizobium? If I let the legumes go to seed and sprout, will there still be the bacteria in the soil and will the cycle continue?
At least the spores of the bacteria will remain and awaken with the new cycle/growing season.
Andre LaS wrote:2) What about planting a tree like Black Locust? Do I need to "innoculate" the roots?
It depends, if no legumes with the same type of bacteria are growing in the region, inoculation will help a lot. Perennial legumes will also build a reservoir of living bacteria for annual legumes with the same bacteria type.
Andre LaS wrote:3) What about before you could BUY a bag of innoculant? Obviously these bacteria had to exist prior to mass-availability of commerical-bacteria-producing companies?
I'm eager to know more about the relationship between these two and our "dependency" on bags of innoculant.
Get some earth from a patch where this kind of plants are growing vigorously and mix it with the soil you want to plant the seeds in. You can also grind up root nodules and dissolve them in water and use the water to start the seeds.
Andre LaS wrote:4) Can a permaculture system become independant from these commercial bacteria? Can the system start producing its own?
If you have a healthy polyculture there are enough legumes present to have the different types of Rhizobium for your different legumes always present in your soil.
You can push the production a bit if you dig up some root nodules from established plants and grind them up for mixing with the seeds before planting.
Important is that you get the same type of bacteria by choosing the nodules form the same plants you are going to plant.