PARENT SESSION
Poster Session 19: Biodiversity
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Plant species effects on ecosystem functioning in the Patagonian steppe, Argentina.

Flombaum, Pedro^{*,1, 2}, Sala, Osvaldo², ¹ IFEVA / Departmen of Ecology, Buenos Aires, Argentina² Center for Environmental Studies, Providence, R.I., USA

ABSTRACT- Previous experiments showed that increasing plant-species richness results in increasing aboveground net primary production. The objective of this paper was to identify the characteristics of different plant species that affect ecosystem functioning and therefore foster our understanding of the mechanisms behind the observed relationship between biodiversity and ecosystem functioning. We evaluated the effects of the 6 dominant-plant species in the Patagonian steppe on N and C cycle. We selected 5 to 10 individuals per species and evaluated their effects on soil N- and C-potential mineralization, soil temperature, soil humidity, root depth, and species phenology. We found that some plant-effects on ecosystem functioning could be assigned to life forms. Grass differed from shrub species in i) shallow versus deep roots, ii) perennial versus deciduous leaves, iii) high versus low soil temperature amplitude, and iv) low versus high labile C-potential mineralization. The 3 shrub species differed in the length of time with green leaves and in the soil respiration rate, in contrast grass species showed similar values for these variables. Other variables related with N- and C- potential mineralization were unrelated to life forms. The shrubs Adesmia campestris and Senecio filaginoides had the extreme values for nitrification (ratio 30:1), and Stipa humilis had the highest amonification among species. S. filaginoides had the highest soil respiration rate for the 1^st week of incubation and then it shifted to S. humilis for the 2^nd week. Our results showed first that most species differed in at least one trait that affects the N- and C-cycle, and second that characteristics associated with life form mainly affected the microclimate and water dynamics.

Key words: species effect, ecosystem processes, nitrogen cycling, carbon cycling