Gopher tortoise (Gopherus polyphemus) populations have declined with longleaf pine (Pinus palustris) ecosystems across their historic range. The influence of gopher tortoise burrows on co-inhabiting plants and animals necessitates an understanding of how landscape features and management practices influence gopher tortoise presence, absence, and abandonment. In this study, naïve gopher tortoise burrow encounter rates from a line transect distance sampling (LTDS) pilot study were used for two methods of modeling gopher tortoise habitat.
In Chapter 1, naïve encounter rates were tested for a linear correlation to a HSI model created from three ranked geographic information system (GIS) landscape variables. Initial results showed a positive linear correlation (all P < 0.0001, 0.55 < r< to 0.70) but a second test using only transects with observed burrows resulted in the loss of all correlations (all P > 0.05, r values ranged from 0.17 to 0.42). However, logistic regression analysis revealed the HSI model was able to predict burrow presence along transects (P = 0.0003).
In Chapter 2, microhabitat variables and five GIS landscape variables were reduced into seven correlated principal components (PCs). According to a generalized linear (logit) model three PCs were significantly associated to active and abandoned borrows. Active burrows were positively associated to: 1) sandhill habitats, longleaf pine canopy, Lakeland soils, high elevations, xeric oak midstory, and wiregrass (Aristida beyrichiana) presence (overall P = 0.003; active P = 0.008); and 2) grassland habitats, little to no canopy, and increased herbaceous ground cover (overall P = 0.0042; active P = 0.0052). Active burrows were negatively associated to mesic flatwoods, Scranton soils, mixed pine canopy, high basal areas, and increased percent tree canopy (overall P = 0.003; Active P = 0.008). Abandoned burrows were positively associated to xeric hammocks, xeric hardwood canopy, mesic hardwoods midstory, increased canopy cover, increased litter ground cover, and increased mean years between burns (overall P = 0.0448; abandoned P = 0.0137). The relationship between fire suppression and burrow abandonment is widely accepted but poorly documented, and the poor resolution of this fire layer accentuates the importance of this detected relationship.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-05042012-104133 |
| Date | 11 May 2012 |
| Creators | Legleu, Christina |
| Contributors | Stouffer, Phil, Kaller, Mike, Nyman, John A, Austin, Christopher |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-05042012-104133/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.0018 seconds