Analysis of global tree population explains baffling trends in species richness

WEST LAFAYETTE, Ind. — Local species richness, the number of species that coexist in a local community, is a key measure of biodiversity. Scientists have known for more than 200 years that large numbers of local species live near the equator, then decline toward the middle and higher latitudes. However, why local species richness differs from place to place remains largely unknown.

Purdue University has now led a study involving 249 co-authors from more than 50 nations that analyzed a database of unrivaled size and detail to understand the geographic variation of local tree species richness across the world’s forested regions and the underlying causes of this global pattern. They found that multiple factors, such as landforms, soil and human impact control local species richness, especially in the tropics.

“Conventionally, people would’ve expected that temperature and precipitation are the main drivers behind the local species richness and biodiversity patterns,” said Jingjing Liang, associate professor of quantitative forest ecology at Purdue. “However, one of the surprises that we found, especially in the tropical region, is that it is actually a combination of different factors.”

The study, based on 1.3 million sample plots and 55 million trees archived in the Global Forest Biodiversity Initiative database, appears in the journal Nature Ecology and Evolution. The co-author list includes 11 Purdue scientists affiliated with the Forest Advanced Computing and Artificial Intelligence Laboratory, the departments of Forestry and Natural Resources and Botany and Plant Pathology and the Rosen Center for Advanced Computing

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