Assistant Professor Ohio University, Ohio, United States
Background/Question/Methods
Masting is a reproductive strategy in plant populations, defined by large variation in seed production among years synchronized at the population level. While most of the research on masting events in oak trees has focused on understanding masting at the population level, there is a lot of unexplained variation among individuals within a population. For example, certain individuals (known as super producers) have been found to have consistently higher or more frequent seed production compared to other individuals. The aim of this research is to determine if intraspecific variation in acorn production is related to the level of phenological synchrony between individuals, as driven by differences in microclimate. Phenological synchrony refers to the timing of flowering and release of pollen, with the idea that individuals that flower at the same time will have increased fertilization due to increased pollen availability and therefore, increased acorn crops. Data was collected on temperature, humidity, slope, and elevation at 36 individual chestnut oak trees within the Vinton Furnace Experimental Forest and the Zaleski State Forest in Vinton County, Ohio. Phenological observations were made at each tree and combined with data from a 20 year seed collection study to quantify reproduction.
Results/Conclusions
Chestnut oak individuals had a mean number of acorns that ranged from 2.78 to 54.33 acorns per m2 of canopy. Super producers were classified as those individuals that had a mean seed production greater than one standard deviation above the population mean. We identified 14% of the individuals as super producers, and they contributed 34% of the total acorns produced. There was also a strong positive relationship between mean acorns per m2 of crown and elevation, with super producing individuals located on ridgetops at higher elevations. Topographic similarities in the locations of the super producers, would suggest that individuals are experiencing similar microclimatic temperature and humidity conditions (the weather data from individual trees will aid in distinguishing and comparing the microclimatic conditions at each individual chestnut oak). Homogeneity in microclimate will be compared with phenological synchrony, to identify if super-producers are experiencing higher synchrony with each other and/or the population. Examining masting at the individual level can be useful in understanding forest ecosystem dynamics and predicting how oak populations will respond to climate change.
