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Forest composition and structure

Iesha Brooks, Stephany Cook, Grace Harsha, Jamie Oriez, and Vanessa Fox
Nature Park Research, UNIV 350, DePauw University
Spring semester 2016

Introduction
A long-term research project was initiated in 2008, measuring forest structure and composition in the DePauw Nature Park.  In 2015, we continued the project to study the change in forest structure and composition over time.  We analyzed differences in the composition of trees, saplings, and seedlings.  We also looked at differences in survival, regeneration, and recruitment among tree species.  We made predictions about how the forest will change in the future. 

Methods
We collected and analyzed data at two sites in the DePauw Nature Park:  Quarry Hillside and Quarry South.  Quarry Hillside is located on a steep hill east of the Rail Trail.  Quarry South is located at the southern end of the Nature Park.  The area of both sites combined is 3.7 hectares, which is equivalent to the area of seven football fields.  Plots were initially set up in 2008.  Each plot is 10 x 10 meters. Within each plot, all trees, saplings, and seedlings were identified, mapped, tagged and measured. We re-measured all trees and saplings in 2015, and documented growth, survival, and recruitment of new trees into the population.

Results
We observed differences in the composition, survival, and recruitment of trees, saplings, and seedlings.  Sugar maple was the most abundant tree and sapling species, and has high survival.  Elm was common among the trees and saplings but has lower survival; 30 percent of elm trees died over a seven-year period.  Cherry, walnut, and red oak were common in the tree layer but rare in the sapling and seedling layers.  Ash and buckeye were less common in the tree layer but were abundant in the sapling and seedling layers; both have high survival. 

Discussion
Sugar maple will probably continue to dominate the forests in the DePauw Nature Park.  Sugar maple has high survival, and modest recruitment and regeneration.  Cherry, walnut, and red oak trees have high survival, but are unlikely to replace themselves because they are almost entirely absent from the sapling and seedling layers.  Ash trees have high survival, recruitment, and regeneration, but are likely to be threatened by the emerald ash borer sometime in the foreseeable future.  The ecological niche currently occupied by ash will most likely be filled by sugar maple.  Our results are typical of patterns seen in other studies of forest structure and composition in eastern deciduous forests.