Concept:Alley cropping requires tree species that coexist with crops without competing too much for soil resources.
Explanation:In alley cropping, trees are planted alongside food crops.
Suitable tree species must have a deep root system.
Deep roots reduce competition with crop roots in the upper soil layers.
A shallow rooting system would compete heavily with crops for nutrients and water.
Therefore, shallow roots are not a true characteristic of alley-cropping trees.
Ideal trees also regenerate rapidly after pruning.
They should form an excellent canopy.
Many of them are capable of fixing atmospheric nitrogen.
These traits help improve soil fertility and crop yield.
Thus, only option A describes an unsuitable characteristic.
Answer:A. Shallow rooting system