Effect of site treatments on soil temperature and moisture and oak and pine growth and nutrient concentrations

Five years after planting, measurements of soil moisture and temperature, leaf nutrient concentrations and growth, were compared for plots of northern red oak, white oak, and shortleaf pine for treatment combinations that included two levels each of harvesting intensity (organic matter removal), site disturbance (soil compaction), and weed control (control of the understory). There were significant interactions between organic matter removal and soil compaction for height, height growth, and d.b.h. of northern red oak, and for the height of white oak, but not for shortleaf pine. Controlling the understory contributed to a marked increase in height, height growth, and d.b.h. of northern red oak and white oak, but only the d.b.h. of shortleaf pine. Mean soil moisture and temperatures were significantly higher for treatment combinations without an understory. Also, with some exceptions, leaf nutrient concentrations were higher for treatment combinations without an understory compared to treatment combinations with an understory. The two-way and three-way interactions for the effect of treatments on variables increased the difficulty of sorting out dominant influences among main effects. However, at age 5, interactions involving understory vegetation seemed to impact soil moisture and temperature, tree nutrition, and growth as much or more than organic matter removal or soil compaction on this site.