ambience: Rainforest, Iquitos, Peru
In the Amazonian Rainforest, not all soil is created equal, and the reason why different plants thrive in different types of soil is a riddle that scientists have only recently been able to unravel. I’m Jim Metzner, and this is the Pulse of the Planet.
“Well, the Amazon basinâ€™s famous for having not very fertile soils. You have white sand soil, which is the least fertile, probably the least common, covering about three percent of the Amazon. You have red clay soil, which is the most common, say, in the western Amazon, which is generally a relatively fertile soil type.”
Paul Fine is an Assistant Professor in Ecology and Evolutionary Biology at the University of Michigan in Ann Arbor.
“Since white sand forests and clay forests have different compositions of species and very few plants live in both habitats, we wondered why that was. Whether it was simply a factor of them not being able to tolerate the other soil type or whether an interaction with their enemies, the insects that eat them, would actually contribute to plants only living in one habitat or another.”
Different plants have different strategies for dealing with hungry insects, depending on which soil the plants thrive in.
“Thereâ€™s a tradeoff between living in a nutrient rich soil type, like clay, and living in a nutrient poor soil, like white sand. A plant growing in fertile soil will not invest in costly chemical defenses because it will just keep growing. Whereas a plant growing in nutrient poor white sand soil doesnâ€™t have the same amount of resources available to it. And so, it makes more sense evolutionarily to invest in some kind of chemical or physical defense against its enemies.”
We’ll hear more on insects and plant diversity in the Amazon in future programs. Pulse of the Planet is presented by the National Science Foundation. I’m Jim Metzner.