Changes in patterns of understory leaf phenology and herbivory following hurricane damage

Hurricanes are important disturbance events in many forested ecosystems. They can have strong effects on both forest structure and animal populations, and yet few studies have considered the impacts on plant-animal interactions. Reduction of canopy cover by severe winds increases light availability to understory plants, providing an opportunity for increased growth. An increase in light availability should cause an increase in annual production of leaves and a more even production throughout the year (i.e., less seasonality in production). This change will affect the availability of food resources to folivorous insects that feed primarily on young leaves; outbreaks of these insects could nullify the temporary advantage of increased understory light levels. On 21 September 1998, Hurricane Georges struck Puerto Rico, providing an excellent opportunity to determine the effect of the hurricane on leaf production and herbivory in the forest understory by comparing post-hurricane data with data obtained from a previous study conducted at the same site. Eight species were analyzed at El Verde Field Station, a wet forest site in eastern Puerto Rico. For the eight species combined, there was an increase in number of leaves produced after the hurricane and a more even seasonal pattern of leaf production, as predicted. Levels of herbivory were much lower (2.03%) after the hurricane compared with pre hurricane conditions (16.05%), indicating that increased light availability to understory plants was not offset by increased herbivory. Lower levels of herbivory were possibly due to herbivore satiation, changes in leaf chemistry, changes in herbivore populations, changes in herbivore predator populations, or a combination of two or more of these factors.