PARENT SESSION
Oral Session # 41: Herbivory III: Forests and Soils.
Presiding: R Jones
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 103.

Deciduous leaf drop reduces herbivory.

Karban, Richard^*,1, ¹ University of California - Davis, Davis, CA

ABSTRACT- Trees in temperate latitudes tend to be deciduous while those in the mesic tropics and at higher latitudes tend to retain green leaves throughout the year. The deciduous habit is thought to be an adaptation to reduce snow and ice loading in winter and reduce drought stress for broad-leaved species. In contrast, the evergreen habit is thought to be an adaptation to increase the time available for photosynthesis, reduce rates of nutrient loss, and increase nutrient recovery from older leaves. None of these current explanations consider herbivory to be an important force in selecting for seasonal deciduous leaf drop. Here I report that oak saplings (Quercus lobata) that were experimentally forced to drop all of their leaves over the winter supported much smaller populations (less than 50%) of herbivores during the following spring compared to control saplings that naturally retained some of their leaves. One important consequence of a deciduous habit may be reducing rates of herbivory.

Key words: herbivory, evergreen, deciduous, Quercus lobata