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Junipers and soil pH

Ellen Buening and Cassidy Ragains
Ecology class, BIO 342, Biology Department, DePauw University
Fall semester 2014

A pH range between 6 and 7 is optimal for plants to obtain nutrients from the soil.  Higher acidity of soil may be caused by presence of conifers such as juniper trees.  Acidity may also be caused by rainfall and leaching, acidic plant material, and high rates of organic matter decomposition.  High limestone content in the bedrock may increase the soil pH to more basic levels.  We compared the pH of soil in areas with and without juniper trees along the Quarry Trail in the DePauw Nature Park.

We hypothesized that the soil would be more acidic next to juniper trees and would be less acidic 5 to 10 meters from juniper trees.

We collected data in two locations, A and B, next to the Quarry Trail; 7 sites had juniper trees and 9 sites had no juniper trees.  At each site, we collected a soil sample 2 inches in diameter and 5 inches deep.  In the lab, we tested pH of the soil samples and used sieves to separate the soils by particle size.

There was no difference in the pH or particle size of soils between areas with junipers and areas without junipers.  

The soils in the Nature Park have a high content of limestone.  The limestone may be counteracting the acidity of the junipers.  Soil in this part of the Nature Park may be well buffered from acidity. Future studies could look at soil pH levels in other parts of the Nature Park.  Larger sample sizes could be collected to further test our hypothesis.