Fine Root Production of Loblolly Pine Clones Growing In Two Contrasting Soil Types.

Fine root production and distribution were estimated in four different loblolly pine clones during the second growing season at a Piedmont site and a Coastal Plain site with contrasting soil types.  These four clones varied in their growth rate and canopy architecture.  Our objective was to determine if they also varied in the fine root production and if those differences help explain above-ground growth differences among the clones. Two intact soil cores (0-20cm) were collected using a bulk density sampler at 40, 80, and 120 cm from the base of two selected trees within each clonal block plot.  Trees were selected to represent the plot average for each clone. Roots were collected after hydro-pneumatic elutriation of the soil cores then fine pine roots were scanned and analyzed using the WinRhizo^TM 2005 software. Analysis of variance were performed on total root length, and root length by diameter class, to determine site, clone, and sampling location differences, as well as interactions among these factors. Results show significant differences in root production among clones, as well as significant clone x site interactions. Although these results are not strongly correlated with above-ground growth at this stage, continuing measurements will elucidate if fine root production could be a good indicator of future growth.