Thursday, August 5, 2010
Exhibit Hall A, David L Lawrence Convention Center
Ryan B. Homsher and Brian C. McCarthy, Environmental and Plant Biology, Ohio University, Athens, OH
Background/Question/Methods Masting, the synchronous, intermittent production of large seed crops by a population of trees, is a well known biological phenomenon. However, the effects of stand level disturbance to this phenomenon have not been well studied. Moreover, researchers have not often recognized the role of genetics or how the local environment dictates how a tree will perform in an ecosystem. Our objective was to determine if forest disturbances would have on effect on masting and how tree resources are allocated for seed production. Two experimental forests were divided into four, 20-ha silvicultural treatments: thinning, prescribed burning, thinning followed by prescribed burning, and an untreated control. Five chestnut oaks (Q. prinus) and five black oaks (Q. velutina) were selected from each treatment. Basal area increments, seed production, and canopy shoot length were measured for eight years. Basal area increments were calculated from tree rings using standard dendrochronological procedures. Seed production was assessed annually by directly measuring seedfall from August to December via two, 0.25 m² seed traps at the canopy line. Samples of branch internode lengths were collected from the outer canopy of each oak tree at the end of the 2009 growing season with a .22 cal. rifle.Results/Conclusions
Chestnut oak acorn production was greater in the thinning and burning treatments for the 2002 and 2005 mast years (Kruskal-Wallis chi-square = 18.291, df = 3, P < 0.001). Thinning treatments resulted in increased secondary growth in Black oak trees (Kruskal-Wallis chi-square = 20.47, df = 3, P < 0.001). Stand level treatments had no significant effect (P > 0.05) on the branch internode length. There was no correlation between mast events, basal area increments, and branch internode length across treatments. The chestnut and black oak populations demonstrated an individual variability in levels of acorn production. Collectively, the data suggest a population level response to reproduction (i.e., masting); however, there appears to also be a strong genetic or microsite component that influences this, irrespective of stand disturbance regime.
