PARENT SESSION
Contributed Oral Session 166: Soil Communities and Plant-Root Interactions
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 522 A, Level 5, Palais des congrès de Montréal

Relationship between ecosystem nutrient limitation and fine root foraging for soil nutrients in a floodplain forest in southern Georgia, USA.

Neatrour, Matthew^{*,1, 2}, Jones, Robert¹, Golladay, Stephen², ¹ Department of Biology, Blacksburg, VA, USA² Joseph W. Jones Ecological Research Center, Newton, GA, USA

ABSTRACT- We explored relationships between ecosystem-level nitrogen and phosphorus limitations and fine root foraging behavior in a floodplain forest in the Gulf Coastal Plain of Georgia, USA. We predicted that fine root proliferation would be greatest in microsites that were rich in the most limiting nutrient. Root ingrowth cores were installed in three replicate sites and were either not fertilized (control) or fertilized with nitrogen (N), phosphorus (P), or nitrogen and phosphorus (N+P). We collected plant litter using litterfall traps to measure litter N and P content. Litter N:P ratios were used to determine whether N or P was limiting. Fine roots responded to microsite N fertilization at two sites (p < 0.05), but not to P fertilization. However, litter N:P ratios ranged from 18 to 24 indicating strong P limitation. We propose three reasons why roots responded to the apparently less limiting nutrient. First, P may have been unavailable to plants due to leaching from the cores or P sorption into aluminum and iron complexes. Second, plants may have been genetically unable to respond to P. Third, N may have been limiting suggesting that litter N:P ratios may be a poor indicator of whether N or P limits plant growth in these forest ecosystems.

Key words: fine roots, nutrient heterogeneity, fine root foraging