Effects of lime, fertilizer, and herbicide on forest soil and soil solution chemistry, hardwood regeneration, and hardwood growth following shelterwood harvest

Abstract

Three sites with strongly to extremely acidic soils and forest floors dominated by hay-scented fern ( Dennstaedtia punctilobula) were divided into 400 m 2 treatment plots in southwestern Pennsylvania. Soil solution samples were taken bi-weekly using tension lysimeters for three growing seasons from three lysimeters on plots receiving herbicide (H); herbicide, lime, and fertilizer (HLF); and lime and fertilizer (LF) treatments. In addition soil samples were obtained before and after treatment. High magnesium pulverized limestone was applied at a rate of 3600 kg ha −1 with 1120 kg ha −1 of 10–20–20 fertilizer. Herbicide treatments were applied at a rate of 0.11 kg active ingredient (ai) ha −1 of Oust ®, a sulfometuron-methyl herbicide to control hay-scented fern. Two additional plots were used as controls and all plots were fenced to exclude white-tailed deer ( Odocoileus virginianus) and previously shelterwood harvested (within the year) to leave a residual basal area of 0.30–0.55 m 2 ha −1. Seedling regeneration height and residual tree diameters were measured (DBH) and basal area increment (BAI) was calculated. Analysis of variance procedures were used to analyze soil solution and soil data. Mann–Whitney non-parametric tests were used to compare treatment differences for residual tree DBH and BAI. Soil solution and soil data indicated calcium (Ca), magnesium (Mg), potassium (K), pH, and both base cation/aluminum (BC/Al) and Ca/Al ratios increased with the addition of lime and fertilizer. The addition of herbicide alone caused increased Al and H + concentrations and reduced Ca/Al ratios to critically low levels. Residual red oak ( Quercus rubra L.) measurements indicated that under normal moisture conditions trees in the HLF plot had significantly increased radial growth over all other treatments. Soil solution and soil chemistry data indicated rather strongly that sulfometuron-methyl alone increased soil acidity and subsequently reduced regeneration growth relative to a similar treatment with lime and fertilizer added. The combination of sulfometuron-methyl herbicide and dolomitic lime and fertilizer resulted in the tallest, most dense regeneration with the greatest species diversity and is recommended for hardwood shelterwood cuts on strongly to extremely acid soils dominated by hay-scented fern where hardwood regeneration is a management goal.