Plant Community Phenological Responses to Simulated Drought Stress: Preliminary Results from a Partial Throughfall Exclusion Experiment
Paulo
Brando, Instituto de Pesquisa Ambiental da Amazônia (IPAM), pmbrando@ipam.org.br
(Presenting)
David
Ray, Woods Hole Research Center (WHRC), dray@whrc.org
Daniel
Curtis
Nepstad, Instituto de Pesquisa Ambiental da Amazônia (IPAM); Woods Hole Research Center (WHRC), dnepstad@whrc.org
Lisa
Curran, Yale School of Forestry & Environmental Studies, lisa.curran@yale.edu
Paulo
Moutinho, Instituto de Pesquisa Ambiental da Amazônia (IPAM), moutinho@ipam.org.br
Droughts associated with El Niño Southern Oscillation (ENSO) and possibly deforestation-driven reductions in rainfall may alter flowering and fruiting in Amazonian rainforests. We hypothesized that persistent drought stress would: (1) initially increase, but ultimately diminish flower and fruit production; and, (2) alter timing of flowering and fruiting among 30 species. The study consists of two 1-ha plots: a dry-plot from which 50% of incoming precipitation is diverted from the soil during the 6 month wet season, and a wet-plot that receives natural inputs. Beginning in Jan-2001, phenological surveys of 30 species were conducted monthly in both plots. At each census, we quantified the presence or absence of reproductive structures. These analyses are restricted to individuals that flowered or fruited at least once during the period. Additionally, beginning in April-2000, flower and fruit production was measured every 15 days in 100 litter traps (0.6 x 0.8 m) in each plot. Our preliminary results indicate 42% greater fruit production in the dry-plot relative to the wet-plot from Jan-2001 to Feb-2004, despite a 5% decrease in flower production. The greatest difference was observed in 2002 when average monthly fruit production was 0.028 g.m-2 wet; 0.061 g.m-2 dry (p=0.008). However, the following year flower and fruit production in the dry plot was 12% and 27% lower than in the wet-plot, respectively, supporting our first hypothesis. In 2003 we detected some evidence of temporal shift in the peak of flowering and fruiting between plots.
Submetido por Paulo Monteiro Brando em 24-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)