Accumulation of starch in roots and foliage of loblolly pine (Pinus taeda L.): effects of season, site and fertilization.

Accurate predictions of stand response to nitrogen fertilization require a better understanding of the plant processes associated with stand nutrition. This study examined the relationship between stand nutrition and starch accumulation in roots and foliage of loblolly pine (Pinus taeda L.). A field study was located on the lower Coastal Plain of North Carolina on four sites of differing soil types. Stands of 8-year-old trees were fertilized with nitrogen (225 kg ha(-1)) or nitrogen plus phosphorus (225 kg N ha(-1) + 75 kg P ha(-1)) in 1981. Roots and foliage were collected from five trees per plot at six sampling dates from July 1983 through January 1985 and analyzed for starch. Starch concentrations showed seasonal fluctuations, with levels generally highest in early spring prior to budbreak. Root starch concentrations were lowest in autumn, whereas foliar concentrations were lowest in winter.