Stand Dynamics and Plant Associates of Loblolly Pine Plantations to Midrotation after Early Intensive Vegetation Management—A Southeastern United States Regional Study

Abstract

Abstract Increasingly, pine plantations worldwide are grown using early control of woody and/or herbaceous vegetation. Assured sustainable practices require long-term data on pine plantation development detailing patterns and processes to understand both crop-competition dynamics and the role of stand participants in providing multiple attributes such as biodiversity conservation and wildlife habitat. This study examined loblolly pine (Pinus taeda L.) plantations across 13 southeastern sites grown for 15 yr with near-complete control of woody, herbaceous, and woody plus herbaceous components during the first 3–5 yr compared to no plant control. This multiple objective experiment (the COMProject) documents stand dynamics at the extreme corners of a response surface that encompasses most conditions of woody and herbaceous competition common to pine plantations in the region. This is the first of two companion reports. After 15 yr, patterns of stand development remained significantly altered by early control treatments and were influenced most by the amounts of hardwoods and shrubs present or controlled. Herbaceous components were more similar across the region. Associated plants in these plantations included 68 species of trees, 33 species/genera of shrubs, and 140 genera of herbaceous and semiwoody plants, woody vines, clubmoss, and ground lichen—241 total taxa or an estimated 490 total species—more richness than previously reported or assumed. Hardwood rootstock numbers were on average maintained at fairly constant levels from yr 1–15 when not controlled, with no initial lag phase evident for reestablishment, indicating prior stand origin. Dynamics of associated vegetation were significantly altered with woody control initially increasing herbaceous cover, while herbaceous control increased hardwood cover and decreased shrub cover. After early herbaceous control, hardwood basel area (BA) was increased by an average of 28%. After rapid early colonization, herbaceous plants began to decline on all treatments about yr 8 as pine and/or hardwood canopy cover reached a total of 50–60%, while woody vines continued to increase. By age 15, plant component richness remained significantly changed by early treatments at all locations, most notably fewer tree species after early woody control. South. J. Appl. For. 27(4):221–236.