Comparative site index of sweetgum (Ḻi̲q̲u̲i̲ḏa̲mḇa̲ṟ s̲ṯy̲ṟa̲c̲i̲f̲ḻu̲a̲ L.) and Southern red oak (Q̲u̲e̲ṟc̲u̲s̲ f̲a̲ḻc̲a̲ṯa̲ michx.) in West Tennessee

Sweetgum (Liquidambar styraciflua L.) and southern red oak (Quercus falcata Michx.) occur naturally together over a continuum of sites in West Tennessee; sweetgum performing better on the best bottomland sites and southern red oak out performing sweetgum on the poorest upland sites such as the dry ridges. Previous research conducted at Ames Plantation, the study area, suggested that the midslope topographic position was about equally productive for both species. However, this conclusion was tentative and was made with incomplete data. Hence an on-the-ground study for verification purposes was necessary. A major objective of this study was to verify that the site index curves of both species, developed for the study area, crossed or were equally productive on midslope sites as opposed to either the upper or lower slope topographic positions. A corollary objective of this study was to establish guidelines for the eventual site mapping of the study area. By identifying the sites of equal productivity and describing their characteristics, guidelines for species suitability delineation were concomitantly determined. In the study no significant difference was found in the mean site indexes for southern red oak and sweetgum on midslope topographic positions. Generally, both species were equally productive on the midslope and were found more often equal in productivity at the common site index of 80 feet (base 50 years). Regression equations were developed to predict the site index of either southern red oak or sweetgum in the absence of the other. Additionally, regression equations were developed using height of one species in an even-aged stand to predict the expected height of the other species in its absence. All prediction equations should be used with polymorphic site index curves for all species, especially sweetgum. Some midslope sites were found to be better for sweetgum than southern red oak and exhibited common characteristics. These sites were slightly concave and most often occurred on Ruston soil series and/or gullied silty land.