BLOOMINGTON, Ind. -- Microbes in the soil beneath a parent tree may kill most of the tree's seedlings in that particular area. This would clear the way for unaffected seeds of other species to take root and flourish near that tree, thereby promoting diversity of trees in forests, according to a study published in the March 16 issue of the journal Nature by Indiana University biologists Alissa Packer and Keith Clay.

The study is described in an article on Nature's Web site at http://helix.nature.com/nsu/000316/000316-12.html

"We showed that a soil pathogen causes the patterns of seedling mortality that we observed in a temperate tree, the black cherry -- high mortality close to the parent tree and low mortality farther away," said Clay, professor of biology. "Animal predators and herbivores may be less important than microbial pathogens in the soil in creating the diversity of tree species in temperate forests. Our results provide the most complete evidence that native pathogens influence tree distributions."

This work has both national and international significance because it extends to temperate forests one of the best-known ideas in ecology, the Janzen-Connell hypothesis. According to this hypothesis, the diversity of tropical forests is enhanced by the presence of host-specific natural enemies that kill offspring around parental trees, creating opportunities for other species to become established.

"While this hypothesis has often been tested in tropical forests, with some supporting results, our study demonstrates for the first time that the same process can occur in temperate forests," Clay said.

Black cherry (Prunus serotina) produces large numbers of bird-distributed fruits throughout the forests of eastern North America. Preliminary studies showed that black cherry seedlings experience high mortality in soil collected beneath black cherry adults, but low mortality in s
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Contact: Hal Kibbey
hkibbey@indiana.edu
812-855-0074
Indiana University
19-Mar-2000