Alley cropping or intercropping options feature crops grown between strips of beneficial trees and shrubs.
Crop options (grown in the “alleys” as intercrops) are many, and could include cereal as row crops or forage, vegetables or fruits, therapeutic plants, flowers, nursery stock, biomass, etc.
Alley crops or intercrops are surrounded by perennial trees and shrubs, and for these surrounding plants, the options are also many, from deciduous to evergreen, fruit- or nut-bearing, those with edible leaves or therapeutic offerings, etc. Examples are many, and could include mulberries, persimmons, apples, paw paws, chestnuts, figs, cherries, hicans, serviceberries, aronia berries, and so on.
Historically, many planted (surrounding) trees for lumber, but as the incredible value of living trees becomes more widely understood, many are instead, opting to only harvest trees when they pose a direct safety risk or are dying.
One key is to select both alley and surrounding crops that are compatible in climate and soil type, and ensuring that their root systems are compatible.
Another key is appropriate spacing, along with the flexibility to change alley crops if sun/ shade conditions change as the canopy matures (depending on spacing).
There are numerous benefits to alley cropping (compared to mono-cropping), including diversification of yields, crop protection, biodiversity, improved soil and water health, wildlife and pollinator habitat, etc. There can though, be challenges as well, including managing the needs of the alley and surrounding crops as they change over time.
The Center for Agroforestry has a resource that offers some good, additional details, their Alley-cropping Agroforestry Training Manual.