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Juniper and sycamore growth rates

Ellen Buening, Linda Sebisaho, Jia Qi, Ashley Junger, and Cassidy Ragains
Ecology class, BIO 342, Biology Department, DePauw University
Fall semester 2014

We were interested in the potential effects of competition between juniper and sycamore trees in the Quarry Bottom of the DePauw Nature Park.  We observed that sycamore trees growing next to juniper trees in the Quarry Bottom appeared to be dying whereas sycamore trees growing alone appeared to be healthy and lively.    

We hypothesized that juniper trees growing next to sycamore trees would have a negative effect on the growth of sycamore trees in the Quarry Bottom. 

We selected paired and unpaired sycamore trees in four areas of the Quarry Bottom:  A = moist soil, limited sunlight, moderate competition; B = moist soil, unlimited sunlight, low competition; C = rocky soil, moderate competition; and D = rocky soil, high competition, low sunlight.  “Paired” refers to a sycamore tree growing less than 3 meters from a juniper tree.  “Unpaired” refers to a sycamore tree growing more than 3 meters from a juniper tree.  We measured height and circumference of the sycamore trees and distance between the trees.  We used an increment borer to core individual trees and measured width of growth rings to estimate growth rates. 

There was no difference in growth rates between paired and unpaired sycamore trees (p = 0.36). Growth rates of sycamores differed significantly among the four sites (p = 0.006).

We observed no effect of junipers on growth of sycamore trees.  Area B had the most distinct growth conditions.  Closer to the Quarry Bottom, the soil is rockier with higher limestone content, large soil particles, more rocks, and lower water content.  The soil may not hold enough water needed for optimal growth of sycamores.  Juniper trees, on the other hand, can survive in a wide range of stressful conditions.  Other plants were competing with sycamore and juniper trees in each location.  The lack of effect of junipers on sycamore growth rates may have been due to the presence of other competitors.