| Abstract: | 133 stands from the uplands of Land Between The Lakes (LBL) were sampled. Stand data were ordinated to identify clinal patterns in the overstory vegetation. A coeno-cline, accounting for 52% of the species variance, was developed from the first ordination axis. Classification of stands identified nine dominance types: Pinus echinata-Quercus spp., Q. prinus, Q. prinus-Q. alba, Q. stellata-Q. alba, Q. velutina-Q. alba, Q. alba, Q. alba-Q. rubra, Acer saccharum-Q. alba-Fagus grandifolia sadF. grandifolia-A. saccharum. Compositionally-stable (climax) and unstable (successional) stands were analyzed separately. Trajectories of unstable stands include the succession of P. echinata to Quercus-dominated communities on xeric sites and of Quercus types to more mesophytic communities (e.g. A. saccharum and F. grandifolia) onmesic sites. These shifts indicate the nature of the future climax overstory composition at LBL. The first axis DCCA ordination for climax stands accounted for 45% of the vegetation variance. Factor Analysis identified two significant suites of variables related to vegetation: soil chemistry/soil moisture and soil texture. Specific variables related to variation in the climax vegetation include soil pH, calcium and magnesium, effective soil depth, available water capacity, percent rock in the soil, slope position, aspect, elevation and distance to the opposing slope. Modal positions of species along the direct gradient ordination were similar in rank order to those derived from the indirect gradient ordination of all stands. The latter ordination represents the present forest vegetation pattern at LBL. Climax stands showed a shift in modes of Quercus spp. toward the xeric end of the gradient and increases in habitat width of mesophytic species. Following a reduction in disturbance, species appear to adjust to changes in competition and available habitat. That is, the dimensions of realized niches (i.e. habitat widths) change with succession. The climax vegetation at LBL appears to show centrifugal organization. |
