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Mentor: Dr. Charles Bicak, Professor, Department of Biology, University of Nebraska at Kearney, Nebraska 68849-1140, USA. Email: firstname.lastname@example.org)
To Cite This Paper:
Krohn, B. and R. Windhorst. 1997. Burrow spacing and plant diversity in prairie dog habitats. Senior Research Thesis, Department of Biology, University of Nebraska at Kearney, Kearney, Nebraska.
Abstract: In 1997 burrow spacing and plant diversity of Cynomys ludovicianus was studied north of Harlan County Dam (N 40.750, W 99.160 ), Harlan County, Nebraska, and north of Cottonmill Park (N 40.090, W 99.220 ), Buffalo County, Nebraska. One 60-yard diameter transect at each site allowed averages in burrow spacing and plant diversity counts from eight subplots per transect. The studies compared a small habitat versus a large habitat. Variabilities in location, soil type, and water availability showed a difference between the two prairie dog habitats.
The purpose of this study was to prove the following null hypotheses: (1) there is no significant difference between burrow spacing versus the size of the prairie dog habitat at alpha = 0.05, (2) there is no significant difference between plant diversity versus the size of the prairie dog habitat at alpha = 0.05.
The first procedure started in the northwest quadrant, connecting the points all the way around the transects until reaching the starting point. The average burrow spacing was found and the procedure was run on both transects for comparison (Fig. 1).
Fig. 1. Burrows from two different prairie dog towns in central Nebraska in fall 1997.
The second procedure started with the addition of an equation to the spreadsheet, distance equals the square root of (x2-x1)2 + (y2-y1)2, computing distances between burrows. The last burrow of each quadrant was compared to the first burrow of the next quadrant continuing through the entire transect. This allowed the use of the equation down the entire spreadsheet. The distances showed average burrow spacing results for each transect. Completion of these studies resulted in determining plant diversity for each transect. A 1.0-m2 grid, divided and numbered into 16 equal squares, allowed specific ground areas to be counted and recorded for lab study. Each quadrant had two sites where plants and grasses were retrieved, making a total of eight sites per transect. The 1.0-m2 grid was set at predetermined x and y coordinates before laying out the transects.
Each sample taken was placed in brown paper sacks and labeled with its correct transect location and quadrant number for further testing in the laboratory. Two plant/grass identification books identified all of the plants and grasses found in each sample (Stubbendieck et al., 1994; Whitson et al., 1992). Two different studies were ran, one to make sure enough samples were taken and the other to show plant diversities between transects. Shannon’s principle allowed the first test to be completed by listing the plant species, the number of new species and cumulative number of new species. The zero in the eighth test proved enough tests had been run for each study. The plant diversity index was derived by using the Shannon-Weaver Diversity Index Computation (Table 1). The program allowed entering of each plant species discovered. The transects were labeled, the number of individuals in each taxa were entered in the computation, omitting any line that had a zero, allowing a true diversity number to compare the transects.
Table 1. Plant species, number of individuals occurring in transects and diversity difference significance.
The second method of study also resulted in acceptance of the null hypothesis. The burrow spacing proved to be 7.75 yards vs. 6.13 yards. Numbers in the spreadsheet ranged from 1 to 55, influencing the outcome. Rearrangement of numbers in the spreadsheet could change the outcome, but could lead to a biased study. No other studies were found to incorporate information and findings into the procedures. Many more studies need to be done in central Nebraska to find an overall relationship between prairie dog habitats and burrow spacing. Studies could include several transects within one habitat, habitats under the same stress and an equation that would compare one burrow to all burrows within the same transect continuing throughout the entire transect.
Plant diversity studies concluded the null hypothesis was rejected. Differences between habitat location (Harlan transect being in a flood plain, while Cottonmill transect is located in loess hills), showed differences of 0.79 and 0.60 respectively. This proved to be a statistically significant difference even though 7 out of 12 species were found in both transects.
The comparisons of the mound spacing was significant between small and large habitats, although the tests were subjected to a highly different conditions. These conditions included a different arrangement of burrows on the spreadsheet which under other arrangements could lead to different P-values other than the concluded P = .0678 obtained in this study. Plant diversities did prove to be greatly influenced by the size and/or location of the habitats. Differences in the soils, water content, and location of the habitats are all factors of influence that proved the null hypothesis wrong.
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