Early plant succession in loblolly pine plantations as affected by vegetation management.
A common study design has been used at 13 locations across the South of the USA to examine loblolly pine (Pinus taeda) plantations established using four vegetation control treatments after mechanical site preparation: (a) no control, (b) woody control with triclopyr and glyphosate, (c) herbaceous control for 4 yr with annual applications of sulfometuron, and (d) total control combining (b) and (c). This research, the Competition Omission Monitoring Project (COMP), is monitoring both pine growth and plant succession. During the first 8 yr, the cover of herbaceous components and prevalent genera, along with pine, woody (non-pine), and total herbaceous cover were estimated annually in September. Stem numbers and heights of arborescent and nonarborescent woody species were measured during the first 5 yr and yr 8. There were 101 prevalent genera of herbaceous plants and 76 species/genera of woody plants present on the study sites, with a core group common to most. Herbaceous cover was rapidly reestablished on no control and woody control treatments, with greater than 80% cover in the first year. After the first year, herbaceous cover steadily declined on no control plots and was sustained when woody plants were eliminated. In general, grasses dominated the herbaceous layer (mainly Andropogon and Panicum spp.) with cover peaking in yr 4. Woody control increased the actual cover of both grasses and forbs, but only the relative proportion of forbs, which peaked in yr 1-2. Woody control also increased the actual cover of vines and semi-woody plants (mainly nontargeted Rubus spp.) by yr 6-8, but only the relative cover of semi-woody plants. Development of the pine canopy cover was similar with woody and herbaceous control, but pine heights were greater with herbaceous control. Herbaceous control did not increase total woody cover until year 8, but the proportion of arborescent tree to nonarborescent shrub cover was increased. Most arborescent species and rootstocks became established in the first year.