Wednesday, November 15, 2006
298-8

Fire Suppression Influences Upon 15N Natural Abundance Profiles of a Longleaf Pine Ecosystem.

Richard Taylor, Jones Ecological Res. Ctr., J.W. Jones Ecological Research Center, Rt. 2 Box 2324 County Rd. 30, Newton, GA 39870, Lindsay Boring, J.W. Jones Eco. Res. Ctr. @ Ichauwa, Route 2, Box 2324, Newton, GA 39870, and Sarah E. Cathey, Univ of Florida, IFAS Agronomy, 2005 SW 23rd St, PO Box 110965, Gainesville, FL 32611.

This study examines the influence of fire suppression (>10years) upon δ15N profiles in a mature longleaf pine (Pinus palustris) ecosystem. The δ15N profiles of a replicated burned and unburned stand were determined in litter, soil, and tissues of N fixing legumes and reference plants including increment cores extracted from pines in burned and unburned plots. Pine foliage, litterfall and litter δ15N values from burned stands are -3, -3.5 and -3 respectively. Soil δ15N values from burned plots increase with depth from 4.5 to 8.5, but fire suppression significantly decreased values from 2.5-30cm depths. Reference non-nitrogen fixing plants ranged in value from -3.0 to -4.0, and legumes are significantly different, ranging from -.5 to -1.8. The δ15N values in pine wood increment cores are not significantly different between burned and unburned treatments, but outer-wood (3-10 years old) and inner-wood (16-23 years old) are significantly different, -2.1 and -1.7 respectively. This indicates that internal physiological processes determined δ15N of tree rings rather than fractionation due to soil processes associated with fire suppression.


Handout (.pdf format, 189.0 kb)