Treehuggers

Treehuggers

Introduction

A number of studies have documented spatial patterns of trees within similar environments. The main purpose of this experiment was to analyze how tree species are grouped along a gradient as the elevation increases from 193 meters above sea level to 215 meters. Depending on the gradient, tree species and other various vegetation exhibit both clumping and dispersal patterns. There have been two main hypothesizes that have dominated the rational of community structure among ecologists. The tree patterns found within an environmental gradient support either the community - unit Hypothesis, individualistic hypothesis or both.

The community- unit hypothesis simply states that tree species are bound into whole units that form communities into a “super organism”. There are clear-cut boundaries along the environmental gradient and the plant species are grouped together by certain environmental factors. Graphically, this model has been portrayed as a series of species response curves in which the starting and ending points of species distribution are clustered. On the other hand, the Individualistic Hypothesis states that the location and distribution of different trees depended on certain conditions and many species could coexists and overlap in their dispersal. (3) There are no boundaries in the vegetation but the distribution and location of trees are affected by certain factors. This approach led to the continuum concept of vegetation, which is portrayed as a series of broadly overlapping species response curves with randomly, distributed starting and stopping boundaries, and modes along an environmental gradient. (2)

In this study, we statistically analyzed three quantitative characteristics of plant community structure among a gradient; the tree species, soil pH and soil moisture to determine if the vegetation corresponded to either hypothesizes. The focus of this study was to analyze the characteristics stated previously to develop a better understanding of vegetation community structure along a gradient. (4) Based on previous findings, the statistical results found within this study will coagulate with both the community unit hypothesis and the individualistic hypothesis. Therefore, it is likely that the percent moisture and pH will be higher near the flood plain and as the gradient increases so will the species diversity with species coexisting in some areas and forming a super organism in others depending on certain environmental factors.

The study area for this experiment was along a gradient near Toby Creek located on the campus of UNC Charlotte. The gradient was 193 meters above sea level in the flood plain to the top of the slope at 215 meters above sea level. The gradient was a total of 400 meters long. The experiment was preformed in April of 2015. The plots used to collect data were roughly .01 hectare or 10,000 square meters. Below is a visualization of the area used for measurements.

Materials and Methods

After collecting the tools the class walked to the gradient near Toby creek. The tools used in this experiment were a shovel, a metal collection bowl, measuring tape, a tree guide, labeled Pyrex jars, data collection sheets and a pH kit. At the testing site, in the middle section of the gradient there was a large soil sample collected with the shovel and placed into a large bowl. Then the trees were first identified based on their leaves and then measured to determine the diameter at chest height in a specific plot located within the top layer of the gradient. After walking back to the lab, two tests were performed to find the soil pH and percent moisture of our sample soil collected from the middle section.

To find the percent moisture the soil sample was placed into an 80 mL pre-weighed Pyrex jar. The sample was then weighed and the grams of the jar were subtracted from the initial weight of the soil. After this, the sample was dried in a Blue M Single-Wall Transite Oven for three days. This oven allowed for the complete evaporation of the water that was present in the soil. In the next lab, the samples were weighed again in order to find the final soil weight. Then the final soil weight was subtracted from the initial soil weight to give the final water weight. The number was then divided by the initial soil weight and multiplied by 100 to give the final percent moisture. (3)

The pH of the soil was found by performing a Truog Soil Reaction Test. First, there were two drops of the Reagent No. 697-27 Triplex Indicator added a cavity of the No. 697-24 Test Plate. After adding the No. 697-26 Soil Reaction Powder, the soil surface was covered with the powder uniformly and completely so that the color of the soil is hidden. Two minutes after applying the powder the color taken by the powder was compared to the pH and Lime Chart.

The first statistical test performed was the IV300, which was chosen because it is an index that represents how dominant or representative a certain tree species is within an area. This test includes the basal area, frequency and density of species relative to other tree species within the location tested. UNC Charlotte provided the software used to find these calculations on a predesigned Excel spread sheet.

The other statistical test performed was the Anova test because there were more than just two groups being tested (In the Dirt on Dirt Lab there was 5 variables tested). In this case the sample size was at 3. The flood plain, middle section and top area were the three samples used. Of these three samples there were 2 variables tested, the percent moisture and the soil pH. The software used to find the statistical data was vassarstats.net.

Results

The percent moisture was calculated at 29.4%. Figure 1 shows that the top section of the gradient had the highest percent moisture. Looking at the chart for percent moisture the mean was calculated to be 31.8. The p-value for the percent moisture was 0.679883. This is greater than 0.05 this proves data for percent moisture was not significant.

Moreover, Figure 2 displays the highest pH values being at the top area. In other words, the top area was found to be more neutral. Looking at the table for pH the average pH for the top area was 7.0, the middle area was 6.0 and the flood plain had an average pH of 6.1. The total mean between all three areas was 6.36. The pH of the individual