Seasonal Fine-Root Carbohydrate and Growth Relations of Plantation Loblolly Pine After Thinning and Fertilization
In 1989, two levels each of stand density and fertilization were established in an 8-year-old loblolly pine (Pinus taeda L.) plantation. In March 1995, treatments were reapplied, and root elongation and carbohydrate concentrations were monitored for 2 years. Our objective was to evaluate relationships between seasonal root growth and carbohydrate concentration in response to thinning and fertilization. Peak root elongation occurred between May and July. Root elongation was greater in response to thinning throughout 1995 and, although not always significant, was consistently greater in thinned plots in 1996. Root growth was reduced in the fertilized plots throughout 1996. Positive effects of thinning on fine-root starch concentrations were observed. Starch levels were consistently lower in response to fertilization for most of 1995 but were greater in fertilized plots during winter 1996. Glucose levels tended to be greater in response to thinning both years and less in response to fertilization in 1995. We conclude that fine-root carbohydrate concentration and net root elongation are characterized by distinct seasonal patterns, and that the magnitude of seasonal root elongation and carbohydrate concentrations is influenced by silvicultural treatments.