FLAVIANA M. SOUZA / IF Close-up of Esenbeckia leiocarpa: high mortality under the mother treeFLAVIANA M. SOUZA / IF
If you pay a visit to a forest like the one at the Caetetus ecological station in the central region of the state of São Paulo, you will see highly aggregated clusters of tropical trees of the species Esenbeckia leiocarpa, with few competitors under their canopies. It was formerly thought that the presence of this species is somehow prejudicial to the growth of others and that the nearly complete absence of other species might favor the survival of the descendents of Esenbeckia. But that’s not actually how things are. “Contrary to what we had believed, Esenbeckia has a much greater impact on its own plants than on other native species,” concluded botanist Flaviana Maluf de Souza, of the São Paulo Forest Institute (IF), based on controlled field experiments conducted in collaboration with her IF colleague Geraldo Franco as well as with Ragan Callaway, of the University of Montana (Plant Ecology, April).
“The survival of Esenbeckia seedlings is much greater under the canopies of other species,” she says. In her field study, Souza planted groups of 200 seeds (100 Esenbeckia and 100 cedar) under adult Esenbeckia and another 200 under trees of other species. Underneath Esenbeckia, 64% fewer seedlings of this species germinated as compared to the germination rate beneath other species; in the case of cedar seedlings, the difference was 35%. This shows that Esenbeckia has a much greater negative impact on its own descendents than on cedar, possibly because Esenbeckia seedlings compete more with each other than with other species.
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