Species list for niches/layers: canopy trees, small trees, vines, clumps and ground covers

Hello, 

I am trying to write a list of species to grow to occupy each different niche/layer: 
So that, when we design our gardens, one species doesn´t outcompete another. 

Actually I plan to divide the list in annuals and perennials, because many of us still enjoy growing a common annual vegetable patch (but doing companion planting). And also for sun loving species (grown in edges and clearings) and shade tolerant species (grown under the canopy). 

The niches would be: 
1) large wide trees, mixed with 2) some taproot tall and thin trees. 
3) overstory with smaller fruit trees (and some n-fixers). Think of apples, pawpaws, citrus... 
4) understory with tall herbaceous plant, with 5) climbers attached, and 6) ground covers. Think corn, beans and squash; or sunchockes, groundnut and chinese artichokes or mints (for a perennial mix) 
7) clumping species fill the rest of the nice (stuff like lavender, raspberries, onions, brassicas...) 


What worries me most is finding species for the layer 4) herbaceous tall plants, because in one function, they should support the grow of climbers without becoming choked, and also they must be able to grow easily above the clumping herbs and ground covers. So, they need to be vigorous species. 

Here goes the list. 
(I don´t go climate specific) 
I am starting from the bottom upwards, as it happens in ecological sucessions. And it´s easier for most of us. 

Ground covers: annual-wise squash and pumpkin are obvious choices, as are peanuts, parsley and coriander, sweet potatoes and probably most salad vegetables (lettuce, chicory, rocket) can also be grown as ground covers. Most except the cucurbits would tolerant some shade, and parsley could be grow in more deep shade. Perennial-wise, I think of strawberries, mints, chinese artichokes, ramps (for deep shade), new zeland spinach (more sun loving), rhubarb (for wider patches), and even oca, mashua, arrowhead and clover (for an easy next to ground layer) 
Clumps: clumps group whatever is not a creeping ground cover or a tall herbaceous. Annual-wise these are potatoes, bush tomatoes, broad beans, most brassicas, onion family, cereals and beet family. Actually they don´t allow a ground cover to grow nearby except if this is smaller species, like radish or lettuce, but from my own experience, most of these clumps vegetables will choke any other small vegetables growing next to it. So, that´s one of my problems: how to combine them. And perennial-wise, there are a lot of herbaceous clumping species, like taro, currants, asparagus: many diffifcult to combine with other perennials, except perhaps small plants like chives. 
Tall shrubs: these must grow above the ground covers. annual-wise the classic corn for the 3 sister, and probably also sunchokes, okra, amaranth or sunflowers. But I am not sure if these would support most climbers without being choked. I was able to grow corn with peas climbing it, and corn also tolerate a snake gourd, container in a pot. I don´t tried growing anything into the okra, amaranth or sunflowers, but beans or peas could probably do it. Climber-wise, cucurbits like cucumber and gourds are more agressive I think. Perennial-wise I think we could think sunchokes (for smaller climbers), bamboos and probably some smaller or larger trees (which ones for which climbers?). Also they all seem to dislike shade, which is a problem under a forest garden (where shades is abundant). Maybe non-edible species are a key solution as they provide a much wider range of choice, rather than thinking only of edibles. 
Vines: Annual-wise I think of legumes and cucurbits; perennial-wise are groundnuts, yams, akebia, chaoyte, kiwi, passionflower, malabar gourd, jícama, peppercorn and grapes (most are agressive so I don´t know which species to support them). Also, most are sun loving, which is a problem for forest garden understories. Which climbers are not agressive and tolerate some shade? 

At the moment I am not going into the tree layers yet. I can think of pawpaw, diospyros, amelanchier and hazelnuts as species for partial shade. All the other fruit trees for sun positions. Again, if you design your forest garden it will have to have a lot of clearings for those sun loving smaller size fruit trees (they are so many: apples, pears, citrus, prunus, almonds, mangos, avocados, berry trees, medlar...). 
But not so much edible choice for large trees (canopy), I think of mulberries, carob, chestnuts, walnuts (but then we have allelopathy). 
What about edible fruit taproot trees? I can only think of pecans. Dates/Palms could make another nice choice as they grow straight and tall. What more species? What for colder climates? 
Maybe the best would be to grow the smaller fruit trees as the canopy itself, and only ocasional tall or large trees. This way, we provide much more sunlight for our forest gardens! So our focus would be in sunchokes guilds, apple guilds, hazelnuts guilds, bamboo guilds, elaeagnus guilds, moringa guilds, corn and amaranth guilds... 

Annual-wise what I need to investigate is how to integrate potatoes, tomatoes, broad beans, most brassicas and most cereals within these layer design system. 
And both annual-wise and perennial-wise to investigate less agressive climbers are tall supportibve edible species for those climbers. 

Overall, I wish to focus in edible species (not forgetting other niches such as n-fixers and food for insects), and I want to focus particularly in high yielding foods, that could be used as staples. 

Please feel free to add more species recommendations (ground covers, climbers, tall herbaceous, shade trees) and to discuss this from a design perspective. 
I am niot going climate specific, but feel free to include species for all climates.

July 2012 - Permaculture at the Arctic, in Iceland

It is now early July, and our permaculture garden in Iceland is in full bloom.

We have outdoors, a thriving garden full of potatoes and sunchokes, plenty of onions and leeks, a carrot bed, salads here and there (lettuce, rocket, mizuna, radish, parsley and pak choi), some cabbages and kale, two squash plants (already gave a courgette), celery, cumin and fennel (overwintered from last year), peas and lentils (grown from seed outdoors), a few sunflowers and strawberries (now starting blooming), lovage and rhubarb (both grow very well in Iceland), several currants (which also provide shelter from wind), and even one surviving tomato and one pepper plant (helped by the heat of surrounding rocks which warm at the sunlight). We also have several flowers (tulips,  phacelia, rye and mustard (that work as green manure), poppies and other native flowers).

If last year, our garden outdoors was neat and organized in rows, this year the garden seems a bit wild, because we opted for some dense planting. We have been experimenting. We are testing companion planting, creating warm micro-environments (by using shelter from wind, mulching and warming rocks) and also by depositing organic matter to create a deep rich soil (where a shallow sandy soil was initially present).

Indoors we have a collection of tomatoes, eggplants and peppers from several varieties (some are rarities like a pink tomato); we even have a container with corn (now fruiting); some chia, fenugreek, anise and sesame (grown from kitchen seeds), some experiments which still have not cropped (quinoa, millet, amaranth and mung beans), different legumes (beans, cow peas, peanuts and chick peas), some perennial vegetables (yacon, chives, chinese artichokes, asparagus, skirett and walking onions), one moringa tree, one ginger plant, and finally some small tree seedlings of honey locust, avocado, pomegranate, manchurian apples, limes, mulberries and others that we started from seed.

We have resorted only to use local resources: our self-made compost, we don't want to import nutrients or organic matter, only use the hay and grass which already grow around the garden itself.