Where do tropical trees grow?

Researchers at the Smithsonian can predict the location of tropical trees based on their ability to resist drought and their need for phosphorus--an essential step in anticipating the effects of global change on the planet’s most biodiverse terrestrial ecosystem.

Because tropical forests contain vast numbers of tree species, many of them rare, it’s extremely difficult to predict the outcomes of environmental change. But STRI’s Richard Condit and colleagues took advantage of Panama’s unique geography to build predictive models.

"The marked variation in rainfall and soil properties across the Isthmus of Panama let us isolate the effects of drought and individual soil nutrients on the regional distributions of more than 500 trees species − never done before at that scale" said STRI staff scientist Ben Turner. "We knew that drought determines why many species occur where they do. More surprising was that soil phosphorus strongly influenced the distribution of more than half the species in the study."

A non-renewable resource mined predominantly in a few locations, phosphorus is a component of the inexpensive fertilizers that sparked the green revolution. However, recent forecasts suggest phosphorus could begin to run out in the next few decades. "If current predictions are true, phosphorus depletion poses a more significant risk to society than climate change, as it will impact us sooner and will affect all through increasing food prices," said Turner.

Tropical tree species that thrive in low phosphorus soils might be part of the solution. "Ecologists tend to think about phosphorus as something that limits forest productivity," said Turner. "But the strong link between phosphorus availability and species distributions opens up the possibility of identifying the genetic basis for tolerance of low phosphorus − the first step in breeding plants that are not so dependent on phosphorus-containing fertilizers."

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Asner Wright Hall Muller Winter Potvin
Turner Detto Hubell Rubinoff Davies