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Title: Information Sheet, Oak Masting in Glover-Archbold Park and GU Main Campus, Washington, D.C.

Instructors' Note

A student in Forest Ecology (fall 2002) at Georgetown University (GU), Washington, D.C., produced this report as an individual class project which had a limit of about 20 hours.

Goals of the projects included:

(1) learning about a relatively natural forest (Glover-Archbold Park which is adjacent to Georgetown University, in Washington, D.C.), the "open urban forest" of GU Campuses, and the "urban forest" in residential neighborhoods near GU.

(2) providing information about these subjects to interested parties via the Internet.

These are short projects that lay groundwork for further investigation in their respective areas. Therefore, these are pilot projects. To see all 12 of the 2002 projects, please use the keyword FE2002R on this Website. Projects of future Forest Ecology students might continue lines of investigation of the 2002 projects.

E. M. Barrows and N. Bakkour, instructors

Oak Masting at Georgetown University and Glover-Archbold Park

James Kelly
Department of Biology
Georgetown University
Forest Ecology 355 Fall 2002

Abstract

This study tests the hypothesis that oak masting is synchronous in the Georgetown Area in 2002. I examined the percent of trees masting on the Main Campus of Georgetown University, and in the relatively natural, adjacent forest Glover-Archbold Park. My study supports the hypothesis that local oaks masted synchoronously. Climate and weather effects on the trees was constant among both sets of trees, and these abiotic factors may have influenced synchronous masting.

Introduction

Masting is a tree's producing a large seed crop in a particular year subsequent to its producing no, or a small, crop in the preceding year(s) (Kricher & Morrison 1988, 302). Masting may be an evolutionary strategy that increases a tree’s offspring number. If a reproductive tree produced about the same number acorns every year, this food could help to maintain a relatively constant population size of squirrels and other animals. These animals might consume most, if not all, of the tree’s acorns. If the tree changed its crop size from year to year, the irregular food supply might reduce the population sizes of its seed predators. My study was designed to test the hypothesis that oak trees on Campus (an artificial, open urban forest) and in the Park (a relatively natural forest) were synchronously masting.

Materials and Methods

In order to test my hypothesis, I examined acorn crops from 10 trees on Ant Hill in Glover-Archbold Park and 10 trees on Main Campus. I picked the trees approximately randomly in the Park and 10 trees on Campus that grew in a row.

Results and Discussion

While recording data, I found it particularly interesting that the number of acorns steadily declined while I walked up Ant Hill. Gravity evidently affected the distribution of the acorns. Trees on the bottom of the Hill had a large number of acorns because many rolled down Hill.

Both Campus and Park of trees masted. Eight of the 10 trees and nine of 10 trees masted in Glover-Archbold Park and Campus, respectively. There was a problem with collecting the data on Campus. Some of the trees were very close to each other, so I could not be certain if the mast underneath a particular tree belonged to that tree. Therefore, I tried to see if there was an equal distribution of mast around a particular tree, or if it was only on one side. If mast was only on one side of the tree, I assumed that the mast did not belong to that tree.

Masting may have been similar in trees in both kinds of forest as result of abiotic factors (including climate and weather), biotic factors, or both. The Campus trees were in a different environment than the Park trees. The Campus trees are near buildings and are surrounded by lawns and plantings compared to the Park trees which are surrounded by forest organisms.

I learned that elevation and terrain greatly influence mast distribution on the ground. Even if a tree on a hillside produces a lot of acorns, many might not be near the tree because they rolled downslope. A tree at the bottom of a hill might appear to have more mast than it really produced.

Future experiments are necessary for understanding the masting of the trees in and around Georgetown, as well as elsewhere. Researchers should record masting data for decades to look for possible long-term patterns. A current hypothesis is that trees mast every 2 or 3 years as a fitness- maximizing strategy. One could examine if this is occurring in local oaks. Further one could look for possible correlations between weather and other factors and masting. It would take many years of research to draw conclusions. Like squirrels, future researchers must wait for the trees to mast.

Acknowledgement

I thank Dr. Barrows for directing my paper in a better direction than I had previously had chosen.