The effect of human interaction on Shannon diversity along the organic horizon
Craig Michael Hansen

Department of Botany, Oklahoma State University, Stillwater Ok 74078

ABSTRACT This study aims to ascertain information on diversity of invertebrates in samples gathered from both near a trail and 1.5m away from the trail on a preserve in Payne County, OK. Samples are examined for invertebrates. Diversity, evenness, and richness are calculated using the number of each taxonomic order found and then compared using a t test. I found that there is not a large difference in mean diversity values between the two samples. I also found that there is not a correlation to human interaction at this study site.

Keywords Species Diversity, Richness, Disturbance, Evenness,

INTRODUCTION Diversity of invertebrate populations varies with the habitat or niche inhabited by the organism. For example, the differences between grass-dominated fields and cultivated fields affect species diversity because of the different conditions and amount of disturbance in the area. Having an understanding of the importance of soil invertebrates is important to understanding the purpose of the study. Soil invertebrates play a large role in maintaining soil nutrients, and therefore the plant life in the area. This correlates to oxygen in the ecosystem and affects us directly. This also provides a necessity for research of invertebrate species in the organic horizon. Studies conducted to find the effects of various disturbances and soil types on the distribution and diversity of invertebrate species have yielded various results. In most cases, human interaction leads to decreased biodiversity (Giller 1996). Other sources have found that species diversity is greatest in areas that are intermediately disturbed (Callaham 2006). In addition to these findings, Scheu and Schulz studied invertebrates and found that multiple successional stages yielder greater levels of population diversity, while Delgado, et al. state that disturbance can accumulate over time and cause reductions on ecosystems and their invertebrate diversity (1994 and 2013). The purpose of this study will be to acquire numerical evidence in the differences between invertebrates near a trail and 1.5m away from a trail. If Sheu and Shulz hypothesized correctly, than the diversity along the trail will be greater than that of 1.5m away from the trail. However, if the disturbances between the sample locations are alike, than diversity will be greater further from the trail (Kotze 2013). To help study the diversity along and off a trail, I will use the Shannon Index to combine species richness and evenness to better scale the diversity of organism into a spectrum easier to analyze. I predict that there is higher diversity away from a trail as opposed to near one because of decreased human interaction.
METHODS
STUDY SITE The location being used for this study is the James K. McPherson Botanical Preserve, South of Highway 51 in Payne County, Oklahoma. The site is in a section dominated by Quercus stellata and Q. marilandica. It was approximately 2:00 PM on January 16th, 2015. PROCEDURES I traveled along a trail for 100m and stopped at a predetermined location. I then flipped a coin to determine which side of the trail to sample. I obtained two samples from the Organic Horizon. I took one immediately adjacent to the trail and another about 1.5m away from the trail. Once I was back in the lab, I measured .5L of matter from each sample and placed them in separate Berlese funnels with ethanol to preserve the invertebrate samples. After a week, I sorted and counted individual organisms present in my samples that had fallen through the Berlese funnels and calculated the Species Diversity. I hypothesize that there will be more Species Diversity farther from the trail than there will be close to it. To test my hypothesis I will be using the Shannon Index of Diversity to measure the number of species, amount of each species and the total number of individuals in the sample to determine the diversity.

ANALYTICAL METHODS: The Shannon Index of diversity takes into account the richness, that is the total number of species collected, as well as the evenness of the population. I also take into account dominance of organisms over others. Comparison is possible by collecting data from 6 samples of 5 different lab sections in addition to the data from the teacher’s assistants. After summarizing the data and finding average values of richness, evenness, and dominance; I predict that the mean diversity will be higher 1.5m away from the trail as opposed to near the trail
RESULTS
As shown in Table 1, the average diversity of organisms on the trail was .436 while 1.5m away from the trail yielded an average diversity of .455. Species richness is needed to calculate the diversity and it is therefore worth noting that the average richness on the trail was 6.16 and 7.16 off of the trail. Evenness also plays a factor in diversity. The averages for on and off the trails are .574 and .547 respectively. The standard deviations of each of these metrics were also calculated. For diversity, evenness, and richness; samples on the trail yielded .069, .079, and 1.72 respectively. When comparing deviation of samples off of the trail, .14, .080, and 2.71 were calculated once again for diversity, evenness, and richness respectively. With the calculated average standard deviations, we can then use a paired t test in order to determine the amount of relatedness of diversity between the samples taken on and off of the trail. With the P value set at .05 and 5 degrees of freedom, the calculated t value is .39 for diversity and the critical value is 2.571. The t value is less than the critical value so I fail to reject the null hypothesis that there is no difference in the diversity between samples collected near the trail and those collected 1.5m away from the trail. Figure 1 shows the comparison in diversity values on and off of the trail with 95% confidence intervals. The evenness and richness also had t values lower than the critical value and therefore the null hypothesis was not rejected in each case.
DISCUSSION
The purpose of this study was to acquire numerical evidence in the differences between invertebrates near a trail and 1.5m away from a trail. After analyzing the difference in diversity, and therefore the evenness and richness of the samples near and off of the trail, I concluded that there is no significant difference in the mean diversity of invertebrates in the organic horizon. Regardless of more disturbances occurring close to the trail, my hypothesis that there would be higher diversity further from the trail is not supported by the findings of this study. One reason why there was not a significant difference between sample locations could be because of the distance between the samples. It is possible that the distance was not great enough to provide a truly significant difference. Studies have found that long term soil disturbance has a large impact on community richness (Callaham 2006). This could be one of the reasons there was no significant difference in diversity. There might not have been enough disturbances to the trail to provide results with drastic changes between samples. The study by Schue and Shulz determined that with wider range of habitats comes a wider range of diversity (1994). It could be that the habitat was too similar in the Nature Preserve to provide large difference in diversity regardless of the distance of minor increases in distance from the trail. In order to get a better grasp on the species diversity in the area, the test could be repeated with different parameters. For example, the study area could be enlarged to encompass a wider area and a larger number of habitats. Weather conditions at the time may have had an effect. This test was conducted in the heart of winter and could be one of the reasons for the lack of diversity. In addition to the weather, the soil conditions were most likely not favorable because the weather was not favorable. However, because it was winter, there was plenty of decaying leaf litter on the ground to promote richness. Though I failed to ascertain any significant numerical difference in the diversity of invertebrate organisms in the organic horizon in Payne County Oklahoma, other research has been conducted that favor increased as well as decreased diversity. In most cases the intermediate disturbance hypothesis hold true. In our case I believe there was too little disturbance and human interaction to show higher diversity. Perhaps if the study site is used continually the diversity will increase in the area. At this time human interaction has shown little impact on the diversity of invertebrates at my current site.
ACKNOWLEDGMENTS
Julie Glenn for pushing me to complete this paper.

LITERATURE CITED
Ashford O.S., W.A. Foster, B.L. Turner., E.J. Sayerd, L Sutcliffea, and E.V.J Tanner (2013). Litter manipulation and soil arthropod community in a lowland tropical rainforest. Soil Biology and Biochemistry 62:5-12
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Callaham M.A. Jr., D.D Richter JR., D.C. Coleman, and M. Hofmockel (2006). Long-term land-use on soil invertebrates communities in Southern Piedmont soils, USA. European Journal of Soil Biology .42 S150-S156.
Delgado Juan D, N.L. Arroyo, J. R. Arevalo, and J.M. Fernandez-Palacios (2013). Road edge effects on litter invertebrate communities of subtropical forests. Spain. Journal of Natural History. 47:3-4, 203-236
Giller Paul S.(1995). The diversity of soil communities, the ‘poor man’s tropical rainforest .Ireland. Biodiversity and Conservation 5, 135-168
Kotze D.j., S. Lehvavirta , M. Koivula , R.B. O’hara, and J.R. Spence (2012). Effects of habitat edges and trampling on the distribution of ground beetles (Coleoptera carabidae) in urban forests. J Insect Convserv. 16:883-897
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| Average | Standard Dev | | | Trail | Far | Trail | Far | T calculated | H' | 0.436 | 0.455 | .069 | .14 | 0.39 | Evenness | 0.574 | 0.547 | .079 | .080 | 1.16 | Dominance | 0.319 | 0.308 | .060 | .143 | 0.19 | Species-Richness | 6.16 | 7.16 | 1.72 | 2.71 | 1 |
Table 1. Shannon diversity (h’) and other metrics average values

FIGURE LEGENDS Figure 1. plots Diversity near the trail versus 1.5m off of the trail.

Species Diversity
Species Diversity

Location
Figure 1 Shannon Diversity as a function of location with 95% confidence intervals