Effect+of+Trees+on+Soil+pH

Thesis: Our thesis is that the density of fern patches will lower the pH of the soil around it. We think this will happen for two reasons: 1) There are more roots absorbing nutrients from the soil. 2) In a more dense patch there will more fallen leaves that will disperse acid into the soil.

 Abstract :  We are attempting to see if there is a relationship between the density of a fern patch and the pH of the soil. We took 3 samples from 3 different locations long the red path a flat rock brook. At the first location we took 3 samples from one fern that with an approximate radius of 5 meters. At the second location we took samples from 2 different patches in a 10 meter radios. The 3rd site has a larger radius and samples were taken from 3 different fern patches within a 20 meter radius.

Materials: 9 Zip-lock bags One Spade One centrifuge 9 Test tubes LaMotte testing kit One awl pH paper

Background Info: pH affects plant growth and the availability of nutrients. pH can affect the absorption of nutrients by plant roots. pH above 7.5 cause iron, manganese, copper, zinc and boron ions to be less available to plants. pH values below 6 cause the solubility of phosphoric acid, calcium and magnesium to drop. pH values between 3 and 5 and temperature above 26 degrees Celsius encourage the development of fungal diseases. More cations in the soil cause the pH to be lower, and more anions cause the pH to go up. Iron which is important to plants, can change significantly due to pH. pH of the soil is above 5.5, plants are able to absorb nitrogen. Phosphorus, becomes available when soil pH is between 6.0 and 7.0.

Methods: We will use an awl and put it two inches into an sample of dirt we want to collect. The samples of dirt will come from anywhere within the fern patch. We will put the samples we collect into bags, and then label the bags with time, date, and location. Originally, we were going to then use the following procedure with a LaMotte testing kit:

"1. Fill test tube (0845) to line with Tricon Flocculating Solution (5941). 2. Use 0.5g spoon (0698) to add three level measures of soil. Cap and gently shake by nverting the tube back and forth slowly for one minute. Allow soil particles to settle. 3. Add 9 drops of *Tricon Soil pH Indicator (5937). Cap and invert the test tube gently one time to mix the contents. Allow soil to settle. 4. Place test tube in the Tricon pH Comparator (5936). Match sample color to a color standard. Record as soil pH."
 * NOTE:** The amount of time required for a soil to settle varies with textrue; clay soils may require additional time, but in most instances the solution will be clear in several minutes.

However, we found that the LaMotte testing kit was not as accurate as using pH paper because the pH paper is much more accurate. We used a centrifuge to separate the indicator from the soil.

 Results: (The numbers in this table represent the pH of the location listed.)  ([|http://www.flatrockbrook.org/features/trails.html)]
 * || Red 1 || Red 2 || Red 3 ||
 * Spot 1 || 4.3 || 4.7 || 4.6 ||
 * Spot 2 || 4.2 || 4.8 || 4.7 ||
 * Spot 3 || 4.3 || 4.6 || 5.0 ||

The three numbers written on this map represent approximately the three major locations we took samples from. From each one of these locations we took three samples. In the list of results, the second sample from spot one is labeled "Red 1 Spot 2," or the first sample from the third location is labeled "Red 3 Spot 1." We labeled the major locations "Red" because that's the trail we were on.

Discussion: From what we observed, the soil's pH is directly related to the fern density in the area. The more ferns there are in a certain location, the lower the pH. We believe this is a result of the amount of decaying matter in each area. The more decaying matter there is, the higher the acidity of the soil will be. This is because decaying ferns, and decaying organic matter in general, produces H+, the ion responsible for acidity. The decaying ferns also produces (CO2), which, when it mixes with water and H+, produces a weak acid called **carbonic acid**. Carbonic acid can be found in acid rain. Red 1, and its three sub-locations, had the highest density of ferns. Red 2 had the second highest, and Red 3 the lowest. There seems to be a steady progression up until Red 3 spot 3, where the pH goes up significantly. This area was by far the least densely populated, and part of the jump could be attributed to that, but other external factors could include varying rainfall (due to tree cover) and the primary formative substances of the soil. Certain limestones could increase the pH significantly, whereas a granite founding material would give the soil much lower pH.

Conclusion: We concluded that, through a combination of increased H+ ions and carbonic acid, the more densely populated areas had soils with higher pH's. The increased amount of decaying matter was directly responsible for this. It is also possible that the parental materials had an effect on the sites, which would account for the degree of difference in the soil pH's. Red 3 Spot 3 is an outlier.

 References:

http://soil.gsfc.nasa.gov/soil_pH/plant_pH.htm Website used to get background information. http://www.esf.edu/pubprog/brochure/soilph/soilph.htm http://hgic.clemson.edu/factsheets/HGIC1650.htm http://www.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/surface-soil-pH http://extension.usu.edu/files/publications/publication/AG_Soils_2003-02.pdf