Rice, Stanley A. , Corbett, Erica A. , Moore, Sara A. .
Seasonal patterns of tannin production in post oaks (Fagaceae: Quercus stellata) in wet vs. dry years.
Like other oaks, post oaks (Fagaceae: Quercus stellata) defend their leaves against herbivores with tannins. Feeney’s study of Quercus robur showed that tannin levels were low in the spring and higher in the summer. This pattern matches the seasonal increase in insect populations and the moist summer in England. In Oklahoma, however, insects emerge quickly in the spring, and drought may reduce their populations in summer. We hypothesized that leaves of Quercus stellata would have a seasonal decrease in tannins rather than an increase, during dry years. Over the course of five years, we collected about 2,500 leaves. Our preliminary analyses indicate that tannin levels decreased through the growing season during three dry years (2004-2006) during which average early morning water potentials were -5.60, -5.30, and -9.13 MPa, respectively, but showed no seasonal change during 2003 when the average water potential was -4.78 MPa. We found no direct relationship between tannin levels and water potential, however, suggesting that the phenological response may not be directly caused by drought. We have not yet found a relationship between herbivore leaf damage and tannin levels. Our results confirm our hypothesis, but also agree with an optimal defense interpretation, in which the trees protect their younger leaves more than their older ones.
Log in to add this item to your schedule
1 - Southeastern Oklahoma State University, Biological Sciences, 1405 N. Fourth, Box 4027, Durant, OK, 74701, USA
2 - Southeastern Oklahoma State University, Biological Sciences
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 1:45 PM