PARENT SESSION
Poster Session #36: Mycorrhizal Fungi and Root Processes.
Thursday, August 9, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
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Seasonal 15N acquisition and allocation in slow- and fast-growing families of loblolly pine (Pinus taeda L.).
Yang, Wei Qiang1, Phillips, Richard 1,2, Dunbar-Wallis, Amy1,3, Topa, Mary1, 1 2 3
ABSTRACT- Loblolly pine (Pinus taeda L.) is widely-distributed in the southeastern United States and is often found in N- and/or P-limited soils. We conducted an 15N-enrichment study to investigate genetic, seasonal and environmental effects on N acquisition and allocation in slow- and fast-growing families of loblolly pine. In June, late July and September of 1999, (15NH4)2SO4 was applied to the upper 0-10 cm soil horizon of selected 6-year-old trees in Scotland County, North Carolina. Seven weeks later, foliage, branch, stem, and root tissues were sampled from trees in fertilized and control plots. One-third of the enriched trees were harvested in January 2000, and tissue dry weights were used to calculate whole-tree 15N budgets. There were significant season, treatment, and family effects on total 15N acquisition and allocation. The highest 15N acquisition occurred during the July and September sampling dates. Fertilized trees acquired more 15N than control trees due to higher standing crop fine and coarse root biomass, and larger tree size. Faster-growing families also acquired more 15N than slower-growing families on some sampling dates. Regardless of treatment or family, trees allocated 83%, 86%, and 70% 15N to aboveground tissues in July, September, and November, respectively. Allocation of 15N nitrogen among various tissue types was not affected by fertilization. Our results suggest genetic differences in 15N acquisition by fast- and slow-growing families of loblolly pine. Funding was provided by DOE Grant #DE-FC07-97ID13527.
KEY WORDS: loblolly pine, nitrogen acquisition, 15N enrichment