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

Fine Root Growth and Belowground Carbon Allocation along a Genetic Gradient from Low to High Elevation Species.

Fischer, Dylan ^{*,1, 2}, Hart, Steve², ¹ Evergreen State College, Olympia, WA, USA² School of Forestry, Flagstaff, AZ, USA

ABSTRACT- Higher elevation species generally invest more resources in belowground growth and fewer resources in aboveground growth that lower elevation warmer climate adapted species. We examined this hypothesis along an intact natural genetic gradient between two species (Populus fremontii and P. angustifolia) and their natural F₁ and backcross hybrids. Demonstrating genetic control is important for two reasons, 1) it shows links between processes from small (genetic) to large (ecosystem) scales, and 2) it grants greater predictability to a hypothesis based on species differences by providing evidence for a genetic mechanism. For belowground measurements we used a combination of minirhizotron data and total belowground carbon allocation (TBCA) estimated from litterfall and soil respiration. Our data suggests that genetics play a strong role in regulating fine root growth, and high elevation-adapted individuals will invest more resources in belowground root production. Root growth represented a higher fraction of TBCA under trees that were more genetically similar to the high elevation P. angustifolia (P < 0.05). However, TBCA was highest in the low elevation species, P. fremontii (P < 0.05). TBCA declined as trees became more genetically similar to P. angustifolia (r² = 0.50, P < 0.05). We conclude that allocating more carbon belowground may not correspond with higher fine root production. Thus low elevation species may allocate more carbon belowground that may be used for mutualism associations and root respiration. As trees become more genetically similar to the high elevation P. angustifolia they allocate proportionally more carbon towards fine root production (P <0.05). These data help link processes from genes to ecosystems, which has been recognized as a major frontier in ecology.

Key words: Minirhizotron, TBCA, Fine Roots, Populus