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.
Above and belowground growth responses to soil nutrient heterogeneity of three coastal shrubs of California.
COLE, E. SHELLY*,1, MAHALL, BRUCE1, 1 University of California, Santa Barbara, Santa Barbara, CA
ABSTRACT- Coastal dune environments demonstrate a high degree of spatial variability in the distribution of limiting nutrients, suggesting that dominant plants there may be able to respond to and exploit nutrient heterogeneity. We performed a comparative relative growth rate (RGR) study with concurrent root analyses on three dominant dune scrub species (Artemisia californica, Ericameria ericoides, and Eriogonum parvifolium) to determine the effects of nutrient heterogeneity on whole plant and root growth. Over nine weeks, we grew these species in pots under three different soil nutrient conditions: dispersed (D), layered (L), and aggregated (A), and we quantified changes in plant growth (size, total biomass, Amax) and root allocation (mass, length). All species attained the largest biomass in the D condition, while the A treatment produced the smallest individuals, except in E. parvifolium. RGR also varied among treatments. Individuals of A. californica showed a significant growth rate increase in the L and A treatments, while this rate remained constant in E. parvifolium. This response in A. californica corresponded with a significant increase in root allocation towards the nutrient-rich areas, a phenomenon not significantly present in the other species. Alternatively, at the whole plant level, root mass ratio was plastic in all species and highest in the A treatment. Therefore, these species could respond to nutrient stress, but they differed in their ability to utilize nutrient patches and maximize growth in heterogeneous conditions.
KEY WORDS: nutrient heterogeneity, dune, shrub, root