Interactions among loblolly pine (pinus taeda L.), associated vegetation and environmental variables on pine plantations on the Cumberland Plateau in eastern Tennessee

The objectives of this research were to characterize the temporal changes in competing vegetation that invaded harvested forest sites which had been intensively site prepared and planted with loblolly pine (Pinus taeda L.) on the Cumberland Plateau in Tennessee, and to evaluate the influence of the competing vegetation along with important environmental variables on the growth of the pine. During the summers of 1977 and 1978, 14 plantations were selected and studied. These locations had similar site conditions and had been undisturbed for 1 to 7 years since the pine had been planted. Environmental variables (soil pH, percent stone, depth, texture, slope and aspect) were measured at each site, and biomass, cover and taxa of the associated vegetation were determined simultaneously. Climatological data (precipitation, irradiance, elevation and temperature) were obtained from nearby weather stations and used in the data analysis. All data were analyzed using simple correlations, stepwise multiple regressions and analyses of variance.

Changes in taxonomic composition occurred seasonally through time. Composites and graminoids dominated the first year, and graminoids continued to dominate the cover on the study sites through the fifth year. Shrubs, woody vines and trees were the major dominants of the associated vegetation by the seventh year. In addition-to the broad successional trends of the major vegetation types, succession at the species level occurred.

Most of the variation in pine growth was explained on the basis of climatic factors. The climatic variables most important in influencing tree height were mean winter and autumn precipitation, mean March and spring temperatures and length of growing season. Variations in basal diameter were most closely related to mean winter. May and autumn precipitation and mean annual and spring temperatures. Mean autumn precipitation and mean winter, March and spring temperatures were most important in influencing tree volume. Soil characteristics and associated vegetation did not appear to have had a major impact on loblolly pine growth, which compared favorably to growth in other regions.