Date of Award
Master of Science
Information on forest composition and change over time is necessary to better understand processes, relationships and ecosystem management. In the late 1980s, 64 compositionally stable stands were studied at Land Between The Lakes National Recreational Area with the purpose of relating species composition to soil and topographic factors. Compositional Stability was determined by Franklin (1990, 1993) using a Similarity Index and a differential in composition indexes between overstory and understory for each stand. Tree species and diameters were recorded within two circular 0.06 ha plots with a minimum of 27 m between plot centers. At a distance of 6.91 m from plot centers and in cardinal directions seedling and sapling stem numbers were recorded by species using four nested 0.003 ha and 0.006 ha plots, respectively. We remeasured 57 stands in 2007 to determine how each has developed and what changes occurred over the past 20 years. Using COMPAH Franklin delineated eight forest community types and in the current study, PC-ORD nearly placed all stands within the same eight community types suggesting there were no major compositional changes. Minor changes in basal area did cause three stands to shift to a different community type. A paired t-test revealed a correlation coefficient of 0.978 for the two overstory compositional indexes (CI) and a correlation of 0.946 for the understory measurement, supporting the notion there was no major changes. A trend that did surface in the 20 years between measurements was an overall reduction of the red/black oak group (Q. marilandica, Q. falcata, Q. coccinea, Q. velutina, and Q. rubra). Because of widespread hybridization within the group analysis was done collectively. The five species had some level of decline in all of the stable communities where the red/black oak group was an important component. Quercus velutina had the greatest reduction while Q. rubra increased in importance in all communities except the A. saccharum community where Quercus trees were absent. Multiple stepwise regression was conducted to compare 2007 overstory CI to environmental factors and produce predictive models. The first model developed compared 14 environment factors to CI. Five factors (Slope position, Calcium, Available water capacity, Elevation, and Aspect) together accounted for 84% of the variance (R2=0.842). Slope position alone accounted for the most variance at about 61% (R2=0.607). The model accounted for 82.5% of the variance after adjustment for the number of samples (adjusted R2=0.825). The second model was developed for field use and compares CI to topographic factors (Slope position, Aspect, Elevation, and Distance to opposing slope or water). All factors except Distance to opposing slope or water were included in the model which accounted for 71% of the variance (R2=0.710) and 69.3% of the variance after adjustment for the number of samples (adjusted R2=0.693). A coenocline was developed to show the species and communities distributions across a moisture gradient. This study found that LBL's compositionally stable forests appear to be developing and remain in a state of equilibrium. Although species in the red/black oak complex appear to be losing importance either due to disease or shorter life spans in most community types. Management activities taking place across the landscape such as cutting and prescribed fire are certain to have some effect on these communities. Future studies of these stands could add to the knowledge of these steady state communities and possibly their response to disturbance.
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