PARENT SESSION
Poster Session #71: Plant Ecology: Physiology and Function.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Uptake capacity of loblolly pine roots measured in the field varies seasonally.

Lucash, Melissa^*,1, Yanai, Ruth¹, Joslin, J.², McFarlane, Karis¹, ¹ SUNY College of Environmental Science and Forestry, Syracuse, NY² Belowground Forest Research, Oak Ridge, TN

ABSTRACT- Most estimates of root uptake capacity are derived from laboratory experiments with crop plants or seedlings. In this study, we measured uptake capacity of intact roots of loblolly pine (Pinus taeda L.), at Calhoun Experimental Forest, SC, in April, July and October. At each sampling period, roots were excavated, placed in simulated soil solutions and changes in concentration of Ca²⁺, Mg²⁺, K⁺, Na⁺ and NH₄⁺ were monitored over time. Uptake capacity varied with nutrient solution concentration but was 2-14 times greater in July than in October. In July, uptake capacity was highest at high concentrations. Uptake capacity was negative at high concentrations in October indicating efflux of nutrients. These results suggest that representing seasonal changes in root uptake capacity may be important for accurate simulation of nutrient uptake by trees.

KEY WORDS: uptake kinetics, nutrient uptake, intact roots