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

Abstract

Changing environmental conditions have the potential to alter allometric relationships between plant parts, possibly leading to ecosystem-level feedbacks. We quantified allometric shifts in field-grown loblolly pine (Pinus taeda L.) in response to altered resource availability based on data from multiple harvests to correct for size-related changes in biomass partitioning. A replicated factorial arrangement of irrigation and fertilization treatments 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 nondestructive growth measurements were used to develop treatment-specific regressions to estimate stand-level biomass for ephemeral and perennial plant parts, both above- and belowground. Stand-level allometric analysis indicated that irrigation increased biomass partitioning to fine roots and decreased partitioning to foliage, relative to other plant parts. Fertilization increased 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, indicating that biomass partitioning in loblolly pine changes with altered resource availability, but is probably under strong ontogenetic control.

Weak growth response to nitrogen deposition in an old‐growth boreal forest

“…However, some studies suggest that resourceinduced shifts in biomass allocation may largely be attributed to the accelerated development of trees and N enrichment may not change the parameters of allometric relationships. Nitrogen fertilization can result in larger, developmentally advanced trees with allometry inherently different from the allometry of trees grown without N enrichment (King et al 1999, Coleman et al 2004, Coyle and Coleman 2005. Unfortunately, we could not conduct field investigations to assess whether changes occurred in allometric relationships because the destructive sampling of whole trees was not allowed in our site (a nature reserve) and such investigations might also greatly disturb our long-term N enrichment experiment.…”

Harvesting Carbon from Eastern US Forests: Opportunities and Impacts of an Expanding Bioenergy Industry

“…Irrigation is used infrequently (usually only at the time of planting) but sometimes supplements precipitation during periods of drought. We analyzed results from 24 forested sites measured in 13 independent studies of loblolly pine plantations in the southeastern US [53][54][55][56][57][58][59][60][61][62][63][64] to determine the effect of water (including both precipitation and irrigation), nitrogen (N), and phosphorus (P) inputs on biomass production. Using a 3-way ANOVA, we tested the effects of water, N, P, and the interactive effects of these variables on annual wood growth of loblolly pine plantations.…”

Forest production responses to irrigation and fertilization are not explained by shifts in allocation

“…This observed shift from below to aboveground production has been proposed as an important cause of increased stem growth with intensive management (Axelsson and Axelsson, 1986;Cannell et al, 1988;Heilman et al, 1994;Misra et al, 1998). However, recent information suggests that resource-induced shifts in allocation may largely be due to accelerated development-that is, that fertilization and irrigation simply result in larger, developmentally advanced trees with inherently different relative belowground growth than that observed in trees grown without amendments (Coleman et al, 2004a;King et al, 1999). Separating the effect of development from resource-induced allocation requires sequential sampling so that comparisons can be made among developmentally similar trees rather than among chronologically similar ones (Drew and Ledig, 1980;Hunt, 1978).…”