When humans cut contiguous tropical forests into smaller fragments, ecologists say, forests along the edges of those fragments tend to experience a number of changes (e.g. higher temperatures, lower humidity), collectively known as “edge effects.” One such edge effect is a decline in tree species diversity. What causes this effect, however, has never been fully understood.
A new Yale-led study
finds that the answer may lie in the complex and cryptic relationship between trees and their so-called “natural enemies.”
Writing in the journal Nature Communications
, a team of researchers demonstrates that fragmentation weakens the impact of some fungal pathogens and insect herbivores — specifically those specialized enemies that help maintain diversity in a tropical system — enabling some tree species to thrive near the forest edges in ways that they could not deeper in the forest.
“Despite the large body of work on edge effects in fragmented forests, barely any studies had actually shown the mechanisms that decrease tree diversity near fragment edges,” said Meghna Krishnadas
, a Ph.D. candidate at the Yale School of Forestry & Environmental Studies (F&ES) and lead author of the paper. “Also, few studies in fragmented forests linked to the theoretical and empirical work on plant community dynamics in intact forests.”