PARENT SESSION
Poster Session # 8: Agro-Ecology.

Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Using plant morphology, physiology and stress response to define plant functional groups in pasture systems.

Comas, Louise^*,1, Skinner, Howard¹, Sanderson, Matt¹, ¹ USDA-ARS, University Park, PA, USA

ABSTRACT- Interest in quantitatively defining plant functional groups has been increasing as ecologists strive to understand plant communities from a functional perspective. Plant functional groups in current literature are most often defined qualitatively. We divided 23 common pasture species from three commonly defined functional categories (grass, legume, forb) into 8 functional groups using principal component analysis on plant growth responses to low N and water availability determined in a greenhouse study. Sensitivity of plant biomass to drought explained similar variation between species as rooting depth. Growth of grasses was generally sensitive to N but grasses could be separated into deep- and shallow-rooted species. Most legumes were drought-sensitive/N-insensitive but a few were drought-sensitive/N-sensitive and drought-insensitive/N-sensitive. Shallow-rooted, N-insensitive forbs were separated from shallow-rooted/N-sensitive and deep-rooted/N-sensitive forbs. We also collected measurements of plant morphology, architecture and physiology to determine which traits were best correlated with plant growth responses to low N and water. With the exception of several fast-growing legumes, fast-growing species in general were the most sensitive to N and water availability. Fast-growing species had a greater percentage of their roots at deeper depths at the expense of shoot biomass.

Key words: pasture communities, plant growth strategies, fine root traits, plant biodiversity