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.
Fine root lifespan is correlated with root nitrogen content.
Withington, Jennifer*,1, Oleksyn, Jacek2, Reich, Peter2, Eissenstat, David1, 1 The Pennsylvania State University, University Park, PA2 The University of Minnesota, St. Paul, MN
ABSTRACT- Fine roots of trees are the means by which they get water and mineral nutrients. They have much shorter lifespans than the rest of the root system, and, as such, they are an important part of the cycling of nutrients in ecosystems. We wanted to compare root nitrogen content to root lifespan for a variety of species. It has been shown in other plants that as root nitrogen content increases, so does root respiration. In plants, as in animals, as respiration increases, lifespan generally decreases. We collected roots aged 0-3 months from eleven species of trees by using in-growth cores. These roots were collected and cleaned, then sorted into two groups by root branching order. Root orders 1 and 2 are the smallest and probably most important part of the root system for nutrient uptake. Root orders 3 and 4 are also relatively fine, but not as likely to be involved in nutrient uptake. The dried roots were analyzed for carbon and nitrogen with an elemental analyzer. Root lifespan was determined using a minirhizotron system to collect sequential images of individual roots over time. Roots were followed from birth to death over the course of two years. Approximately 80-600 roots were followed for each species. Among different species, root nitrogen decreases in 1st and 2nd order roots as root lifespan increases. For 3rd and 4th order roots, which are less directly involved in nutrient acquisition, N concentrations were lower than that found in lower order roots, and there was no significant variation across species. Consequently, our hypothesis that root nitrogen content decreases with increasing root lifespan was supported.
KEY WORDS: fine roots, lifespan, nitrogen