PARENT SESSION
Poster Session 7: Grasslands
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Patterns of N uptake and allocation by plants in Inner Mongolia steppe.

Pan, Qingmin^*,1, Bai, Yongfei¹, Han, Xingguo¹, Wu, Jianguo^{1, 2}, ¹ Laboratory of Quantitative Vegetation Ecology, Beijing, China² Faculty of Ecology, Evolution, & Environmental Science, Tempe, AZ, USA

ABSTRACT- A handful of studies have showed that some plant traits are associated with effective resource acquisition and competition in plants, but which traits should be considered as index in predicting the competitive outcome and in structuring the communities remains debated. In order to understand the role of plant physiological traits related to nitrogen uptake and allocation in structuring the community, we conducted an experiment in Leymus chinensis community of Inner Mongolia steppe, a nitrogen limiting ecosystem, with 15N tracer. Ten plant species with different abundance in terms of relative biomass ranks were selected. We examined the nitrogen uptake and allocation characteristics for the species. The results showed that 1) the patterns of nitrogen uptake and allocation strikingly differed between species with different abundance in terms of relative biomass. The dominant species were characterized by the lowest nitrogen uptake rate, the highest (lowest) nitrogen allocation to root (shoot), the highest root/shoot ratio, and the highest nitrogen productivity. In contrast, the rare species were characterized by the highest nitrogen uptake rate, the lowest (highest) nitrogen allocation to root (shoot), the lowest R/S, and the lowest nitrogen productivity. 2) Patterns of plant traits dealing with nitrogen uptake and allocation were significantly correlated with species relative abundance. Nitrogen uptake rate and nitrogen allocation to shoot were negatively correlated to species relative abundance while nitrogen allocation to root, nitrogen productivity, and root/shoot ratio were positively correlated to species relative abundance. 3) Under this stressful environment, plant traits, such as, nitrogen uptake rate, nitrogen allocation to root (shoot), nitrogen productivity and root/shoot might be involved in important physiological index of competitive ability due to their significant correlation to species relative abundance. These results suggested that plant physiological traits related to nitrogen uptake and allocation played important roles in plant competition and in structuring community. Different patterns of plant traits related to nutrient uptake and allocation may provide an important basis for species coexistence in a stressful environment.

Key words: Interspecific competition, Relative abundance, Nitrogen uptake, Nitrogen allocation