PLANT SPECIES EFFECTS ON ECOSYSTEM FUNCTIONING IN THE PATAGONIAN STEPPE, ARGENTINA

P. FLOMBAUM; O. E. SALA

Montreal, Canada

Congreso; 90th Annual Meeting of the Ecological Society of America, IX INTECOL; 2005

Ecological Society of America, INTECOL

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 1st week of incubation and then it shifted to S. humilis for the 2nd 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.