HR: 1340h
AN: B43B-1171    [Abstracts]
TI: Complex Interactions Among Resources Drive Grassland Ecosystem Responses in two Transplanting Experiments
AU: * Sebastia, M T
EM: teresa.sebastia@ctfc.es
AF: Forest Technology Centre of Catalonia, Pujada del Seminari s/n, Solsona, 25289, Spain
AU: * Sebastia, M T
EM: teresa.sebastia@ctfc.es
AF: High School of Agronicultural Engineering, Univeristy of Lleida, Av. Alcalde Rovira Roure 191, Lleida, 25198, Spain
AB: Changes in patterns of above- and belowground biomass, biodiversity, plant species and guild composition, and biogeochemical cycles were assessed in two transplanting experiments in mesic mountain grasslands in the Pyrenees. In both experiments, turf sods were transplanted from upland to lowland locations. The first experiment aimed to evaluate general responses to warming and drought, and the second to disentangle the effects of possible underlying mechanisms through resource manipulation by means of a nitrogen x phosphorus fertilisation experiment. Mesic grasslands showed strong shifts in plant diversity and composition after a short period of warming and drought, as a consequence of acute vulnerability of some dominant grasses, rare species losses, and aggregate and trigger effects of originally uncommon forb species. Environmental factors interacted in complex ways, producing changes in biomass distribution and guild proportions. Grasses dominated in the upland and at high resource levels while forbs dominated in the lowland and when water and nutrients decreased. The increased aboveground biomass in grassland sods transplanted to the lowland suggests that biomass production was more temperature-limited than water-limited. The enhancement effect found in the upland sods following phosphorus fertilization supports the hypothesis of a strong limitation arising from reduced nutrient availability, confirming the central role played by phosphorus in these grasslands. Nitrogen addition did not stimulate total biomass but affected guild composition. The counterintuitive effect of increased biomass with decreased water in the lowland was related to shifts in dominance from grasses to forbs, probably enabled by decreased nutrient availability under drought conditions.
DE: 0410 Biodiversity
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0476 Plant ecology (1851)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting