Weed control and overstory reduction improve survival and growth of under-planted oak and hickory seedlings

Abstract

Weed control and overstory reduction are important silvicultural treatments for improving survival and growth of under-planted oak and hickory seedlings. Mast-producing trees in the bottomland forests of the blackland prairie and Post Oak Savannah ecoregions of Texas have declined in abundance. Oaks and hickories have been replaced by more shade-tolerant species, including green ash (Fraxinus pennsylvanica Marshall) and sugarberry (Celtis laevigata Willd.), which do not produce significant hard mast for priority wildlife species. A split-plot experiment design was installed on three sites at Richland Creek Wildlife Management Area in Freestone County, Texas, studying the effects of canopy coverage and competition control on survival and growth of bur oak (Quercus macrocarpa Michx.), Shumard oak (Quercus shumardii Buckl.), and pecan (Carya illinoinensis (Wagenh.) K. Koch) seedlings. Uprooting by hogs shortly after planting resulted in greater than 90% mortality of pecan on the two lower elevation sites. Year one survival of Shumard oak was significantly higher than bur oak. However, bur oak was more preferred by hogs than Shumard oak. Year one growth of bur oak was significantly greater than Shumard oak. Severe flooding during the second growing season caused complete mortality on the lower two sites. None of the species were well suited to such prolonged (3–4 months) inundation as seedlings. On the remaining site, density reduction and weed-barrier mats improved growth and survival while herbaceous weed control with herbicides actually reduced both growth and survival.