Stand-level allometry in Pinus taeda as affected by irrigation and fertilization

Changing environmental conditions have the potential to alter allometric re lationships between plant parts, possibly leading to ecosystem-level feedba cks. We quantified allometric shifts in field-grown loblolly pine (Pinus ta eda L.) in response to altered resource availability based on data from mul tiple harvests to correct for size-related changes in biomass partitioning. A replicated factorial arrangement of irrigation and fertilization treatme nts was applied for 4 years to an 8-year-old loblolly pine plantation on a well-drained, low fertility site in North Carolina. Destructive and nondest ructive growth measurements were used to develop treatment-specific regress ions to estimate stand-level biomass for ephemeral and perennial plant part s, both above- and belowground. Stand-level allometric analysis indicated t hat irrigation increased biomass partitioning to fine roots and decreased p artitioning to foliage, relative to other plant parts. Fertilization increa sed partitioning to perennial tissues (coarse roots, taproots, and branches ) and decreased partitioning to ephemeral tissues (foliage and fine roots). Changes in allometry were small (< 6 %) but statistically significant, ind icating that biomass partitioning in loblolly pine changes with altered res ource availability, but is probably under strong ontogenetic control.