By Sean Cummings
For newly sprouted trees, cattle and deer are usually a curse, come to nibble away what little body they have. But an advance article posted in October in the Annals of Botany suggests that in certain circumstances, the browsing animals could be a blessing in disguise: Losing leaves may help California oak seedlings conserve water during drought, boosting their chances of surviving.
The finding, based on seedlings grown in a greenhouse, hasn’t been verified in the wild. But if it holds up, it could inspire forest managers to try trimming their seedlings or allowing limited browsing early on to give these trees a better shot at maintaining their populations as climate change intensifies drought in places such as California and Spain.
“It contradicts a lot of what we think we know about the effects of drought and herbivory,” says Virginia Matzek, a restoration ecologist at Santa Clara University who was not involved in the study. “For them to interact in a way that might actually be offsetting … is encouraging.”
Across the Northern Hemisphere, oaks are keystones in their ecosystems—providing shade, habitat, and nourishment (via leaves and acorns) to hundreds of species of insects, birds, mammals, and fungi. “Oaks punch above their weight,” says Ian Pearse, an ecologist with the U.S. Geological Survey who has studied California oaks but wasn’t involved in the research. “The amount of biodiversity up in the canopy of oak trees can be pretty staggering.”
But oaks today face challenges their ancestors didn’t. Ranching and the decline of predators have intensified grazing of oak ecosystems by cattle and deer, and droughts are lasting longer in many regions. These pressures make it increasingly difficult for seedlings to reach adulthood, says Ramón Perea, an ecologist at the Polytechnic University of Madrid (UPM) and senior author of the new study. As a result, he notes, many oak woodlands and savannas are struggling.
