Ten-year growth response of midrotation slash pine plantations to control of competing vegetation

Abstract

In 1976 a competing vegetation experiment using treated and control plots was installed across four soil drainage groups in 9- to 15-year-old site-prepared slash pine (Pinuselliottii Engelm.) plantations located throughout the lower coastal plain of Georgia and north Florida. All understory vegetation was removed from treated plots, which were then kept relatively free of competing vegetation for 10 years. Analysis of covariance revealed that treatment had a significant effect on height, basal area, and total and merchantable volume growth per tree and per hectare over the 10-year period. Both soil drainage group and its interaction with treatment were found to be nonsignificant for each response variable. Average stand height increased 7.1% (0.44 m) more on treated than on control plots, and average basal area per tree increased 18.4% (0.0019 m2) more after 10 growing seasons. Net total and merchantable volume growth per hectare during the 10 years increased by 13.2% (17.6 m3/ha) and 15.2% (15.7 m3/ha), respectively. Percent increases in net merchantable and total volume growth per hectare leveled off after about 4 years, but the absolute differences continued to increase throughout the 10-year measurement period.