PARENT SESSION
Oral Session #8: Plant Ecology: Nutrient Uptake, Movement, Use.
Presiding: V. Gutschick
Monday, August 5. 8:00 AM to 11:30 AM. Grand Ballroom West, Radisson.
Exploring effects of relative growth rates on morphological root foraging of fast and slow-growing Mediterranean-climate grass species.
AANDERUD, ZACHARY*,1, BLEDSOE, CAROLINE1, RICHARDS, JAMES1, 1 University of California Davis, Davis
ABSTRACT- We explored effects of nutrient rich microsites (RICH) and relative growth rates on morphological root foraging by two fast-growing annual (Bromus diandrus Roth, Bromus hordeaceus L) and two slow-growing perennial (Elymus glaucus Buckley, Nassella pulchra A. Hitchc.) grass species from California oak woodlands. Plants were harvested at either at a common time (TIME, plants varied in size) or at a common leaf number (LEAF, surrogate for biomass). Leaf number and plant biomass were positively correlated for all species, except slow-growing N. pulchra. At TIME, all species (except fast-growing B. hordeaceus) had higher root length density (RLD) in RICH than in control microsites (CONTROL). Slow-growing E. glaucus elevated RLD to the greatest extent in RICH compared to CONTROL followed by fast-growing Bromus diandrus and slow-growing N. pulchra. Selective root placement within RICH was due to significant increases in root biomass density (RBD) and minor alterations in specific root length, but no modifications in branching frequency. Fast-growing species produced 1.5 times more RLD and RBD than slow-growing species in RICH. When compared at LEAF, none of the four species significantly enhanced RLD in RICH compared to CONTROL. When evaluated at TIME, root foraging of the four species did not reflect the typical responses of fast- and slow-growing species, but did reflect the typical responses of species adapted to nutrient poor and nutrient rich environments.
KEY WORDS: morphological root foraging, selective root placement, nutirent-rich soil microsites