Nitrogen Fixers for Eastern Cascades

Hey all, I’m near Leavenworth WA and in the process of establishing a food forest of sorts, with various heartnuts, walnuts, apples, pears, almonds, plums, mulberry, currants, gooseberry, and various other native and cultivated edible perennials. What I’m lacking is good sources of nitrogen. I don’t have much access to animal manure currently, and I don’t have any nitrogen fixing plants, other than some volunteer alfalfa.

I’m hesitant to plant a bunch of black locust because I’m on 2.5 acres adjacent to a creek and it would be ideal conditions for them to spread throughout the entire area. Perhaps that’s something I want? Some people in this area frown upon black locust, although I think it has many beneficial properties, and it’s too dry around here for it to really spread like it would in western Washington. But it’s also kinda a thorny struggle when they’re young trees. I could be convinced to try them if someone’s had strong positive opinions about growing them for this application though. But, are there alternatives that might do the nitrogen fixing job just as well? Has anyone tried the native Ceanothus plant interplanted among cultivated trees? Seems a bit rough and hard to maneuver around. How about Siberian Pea Shrub? I’ve tried several times growing those and they don’t seem to grow all that abundantly. Otherwise I’d be leaning towards nitrogen fixing ground cover, which would be some kind of vetch, peas, clover, etc. I’m trying to stay away from annuals for this particular use. Does anyone have any suggestions and experience with this conundrum in this bioregion?

Thanks
-Sean

As I understand it the natural succession in nature is alders which are nitrogen fixers.  The leaves of the alders build organic soil mater until soil life takes over the nitrogen supply. Observe if the alders come up in cleared and burned areas in the Leavenworth area.  Generally they do not get large in cold dryer areas.  They have no thorns. they can be coped and dropped and used for firewood.   In my area alders can become true trees but only a small fraction of the many that come up after disturbance that manage to reach canopy size before being shaded out.

any of the pea/bean fraternity or for pasture situations clovers, medics which are low growing, or lupines (seeds also double as livestock feed, and the plants can be used as green manure.
All interact with nitrogen fixing bacteria in the soil.  There must be more, but I'm not familiar with what grows in your part of the globe.