Seasonal branch and fine root growth of juvenile loblolly pine five growing seasons after fertilization

Abstract

In 1989, we established two replications of two fertilization treatments in a 10-year-old loblolly pine (Pinus taeda L.) plantation. Between March and September 1993, branch internode and needle fascicle expansion in the upper and lower third of crowns were measured weekly on three south-facing branches of each of four trees, and new root initiation and elongation were measured at 10-day intervals in three vertical rhizotrons per plot. In one replication, soil water content was measured daily. Fertilization significantly increased the expansion of first flush internodes in the upper crown and first flush needle fascicles in the upper and lower crown. New root growth was stimulated by fertilization in the second half of the growing season. The timing of root growth responses to fertilization corresponded to branch phenologies in the upper and lower crown that were conducive to increased basipetal transport of photosynthate. We conclude, therefore, that new root growth was linked to source-sink activities in the crown. Root initiation was greater in the upper than in the lower part of the soil profile; however, as the growing season progressed and water deficit increased, this relationship was reversed. The effect of soil depth on seasonal root growth was closely associated with water availability, suggesting that root initiation deep in the soil profile is critical for the continued production of new roots in environments subjected to short-term, but relatively severe, water deficits.

Post-transplant root and shoot development inAbies nordmannianaSpach. seedlings after whorl bud and branch pruning

“…Removal of the whorl and lateral buds and whorl branches had a more severe effect on plant growth and caused a reduction in root length and DW. Removal of a significant part of the photosynthetic area was the likely reason for the reduction in root and shoot growth, which was in accordance with [26], who observed that current photosynthesis was responsible for new root growth in conifer species, and with [24], who found similar results in Pinus taeda L.…”

Seasonal photosynthesis and water relations of juvenile loblolly pine relative to stand density and canopy position

“…Sword et al (1996) found that on Gulf Coastal Plain sites, new fascicle needles of loblolly Fig. 2 Seasonal predawn and daytime xylem pressure potential (Y pd and Y d ) and soil volumetric moisture content (SMC) in a 16-year-old loblolly pine plantation.…”

“…The highest P n was observed in the spring, when ambient conditions were most favorable. The photosynthate exported from 1-year-old foliage during that period may have been one of the major carbon sources for flush shoot elongation and needle growth (Dickson 1989;Sword et al 1996). During the early growing season, therefore, tree carbon balance could be significantly affected by nonoptimal environmental conditions.…”

The effects of water availability on root growth and morphology in an Amazon rainforest

“…While rhizotrons also provide data on root length (e.g. : Field studies: Itoh 1985;Sword et al 1996;West et al 2003;Davis et al 2004. Reviews: Vogt et al 1998Hendricks et al 2006), the unit of measurement (root length per unit area of observation screen) is not easily integrated into models of plant water and nutrient uptake.…”