Effect of early age woody and herbaceous competition control on wood properties of loblolly pine

Early age competition control has been reported to significantly improve the growth and yield of plantation grown loblolly pine. The objective of this paper is to understand the changes in wood properties: basal area weighted whole disk SG, earlywood SG (EWSG), latewood SG (LWSG) and latewood percent (LWP) of 14 year-old trees which received early age herbaceous and hardwood competition control, using data collected from 13-sites across 4-physiographic regions in the southeastern USA. The study was laid out in a randomized complete block design and had four levels of weed control (no weed control; woody vegetation control; herbaceous vegetation control; and woody and herbaceous vegetation control), with four blocks at each site. Increment cores 12 mm in diameter were collected at breast height (1.37 m) from 9-trees in each plot and ring-by-ring SG, EWSG, LWSG and LWP measured using a X-ray densitometer. Whole disk basal area weighted SG and LWP were determined for each tree and used for analysis. A reduction in whole disk SG of 0.039 and 0.0014 and LWP of 7.38% and 3.62% was observed for trees which received total weed control compared to no weed control, for lower and upper Coastal Plain sites, respectively. For trees receiving total weed control compared to no weed control, it was observed that the diameter of the juvenile core increased by 20% on average across all physiographic regions. However, no change in the length of the juvenile period was observed among treatments other than the regional differences.