Compacting Coastal Plain soils changes midrotation loblolly pine allometry by reducing root biomass

Factorial combinations of soil compaction and organic matter removal were replicated at the Long Term Site Productivity study in the Croatan National Forest, near New Bern, North Carolina, USA. Ten years after planting, 18 pre- selected loblolly pine (Pinus taeda L.) trees were destructively harvested to quantify treatment effects on total above- and below-ground tree biomass and to detect any changes in the absolute and relative allocation patterns. Stem volume at year 10 was not affected by compaction treatments, even though the ultisols on these sites continued to have higher bulk den- sities than noncompacted plots. However, even when site preparation treatments were undetectable aboveground, the treat- ments significantly altered absolute root growth and tree biomass allocation patterns. Soil compaction decreased taproot production and significantly increased the ratio of aboveground to belowground biomass. Decreased root production will decrease carbon and nutrient stores belowground, which may impact future site productivity.