planting pionner trees

Hi, im starting an edible forest garden and im gonna plant first pionner trees, and i have some questions:

I choosed this trees:
sauce ( salix)
tagasaste
algarrobo
casuarina

My land is a 2000 square meters aprox.
I was wondering, how many trees should i plant?
At this moment my land is empty, there are just a few bushes and trees in the limit of the land .
should i full all my land with pionner trees? and what distance between trees should i have? Which is a good distance for planting pionner trees?

I have another question:

I want to plant also a tree of moringa oleifera and a tree of pacay, ive read this trees grow in very poor soils ( pacay is also nitrogen fixer) , so i was wondering if its fine if i plant also these plants in combination with my pionner trees? or should i plant pionner trees alone?

I also want to plant comfrey, do you think now its a good moment to plant comfrey in combination of the pionner trees?




thanks in advance


R.

It depends on what microclimates and guilds you would like to add later. Pioneer trees are meant to add nutrients to the soil and then provide mulch when you transition into a mature food forest.After they've done their job of building up and livening up the soil, they can then be slowly removed for the food trees to take a place in. Some of the pioneers will still be necessary at the mature stage of the food forest. I'd advise planting them at least as far apart as their canopy size. Then, add more or less space depending on the amount of shade or lack thereof that you would like. Microclimates are just tiny pockets of places that are ideal for one species or another. It increases biodiversity. Comfrey and any other dynamic accumulators are great for the early stages building soil, and they are also good for making plant guilds. Plant whatever you desire; just to keep them alive, the proper microclimate would be necessary. For the moringa tree, it does not seem that poor soil is a prerequisite, they just don't like getting their feet too soggy.

If you have access to some soil amendments, mulch, fencing, and irrigation infrastructure, you could also go ahead and start planting your permanent food plants, especially the trees, at the same time as your nurse plants. You may have to pamper them a bit the first few years, but you will be that much further along toward yield. If you have abundant rain and lots of propagation material, you could crowd the nurse plants quite a bit, and then simply thin them later as needed to create space for the food plants, obtaining yields the while as mulch, fodder, fuel, etc.
I would research carefully, and perhaps do some local observation on the species you want to use in quantity as pioneers. Casuarina, for instance, is allelopathic according to some resources.

You want at least 75% of your pioneer trees to be nitrogen fixers