ou are a researcher studying succession in a desert community. you discover that wherever a particular pioneer shrub species is found, you consistently find diverse communities of small flowering plants under the shrubs but not out in the open. to explain this phenomenon, you perform an experiment with four treatments. in the first treatment, you leave the shrubs intact. you find that the flowers last a normal life span, and after they die, new flowers emerge under the shrub. in the second treatment, you remove the shrub and keep the flowers intact. you find that the flowers last a normal life span, but when they die, no new flowers emerge. in the third treatment, you replace the shrub with an umbrella. you find that the flowers last a normal life span, but when they die, no new flowers emerge. finally, in the fourth treatment, you replace the shrub with a t-shaped post. you find that the flower species last a normal life span and when they die, new flowers emerge under the post. what mechanism best explains why flower populations can be sustained under the desert shrubs?