Pacific region climate change
ABSTRACT Due to the pervasive effect of El Niño-related climate anomalies on societies over broad regions of the Indian and Pacific Ocean regions, climate model simulations can provide valuable information concerning possible future climate change that could have a similar signature in those regions. Average climate change in the Pacific region from increased carbon dioxide (CO2) in a global coupled ocean-atmosphere general circulation model is characterized by greater warming of the ocean surface in the eastern tropical Pacific than in the western tropical Pacific. This pattern resembles El Niño conditions as well as the decadal timescale climate anomalies observed during the 1980s. As a consequence, average increases in precipitation in the central equatorial Pacific in the model with increased CO2 are accompanied by precipitation decreases in the northern and southern tropical Pacific, Australasia and eastern Indian Ocean regions. A deepened Aleutian low pressure center in the North Pacific is also associated with mean climate changes due to increased CO2 in the model and is similar to El Niño conditions and the decadal timescale observed anomaly pattern. The model results suggest that future droughts in the Australasian region, already associated with naturally-occurring El Niño events, would increase in intensity due to the juxtaposition of climate anomalies of the same sign from increasing CO2 in the atmosphere. This result has implications for the management of fresh water resources in these regions.
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ABSTRACT: Summary • Rain forest understorey plants suffer leaf area losses due to natural causes or when leaves are harvested as non-timber forest products. The negative effects of defoliation on plant fitness can be exacerbated during periods with strong water shortage and high temperatures, typical during ENSO (El Niño Southern Oscillation) years in Mexico and Central America. At present, the isolated and combined demographic effects of ENSO events and repeated defoliation on tropical rain forest plants are poorly understood. • We studied the consequences of repeated defoliation and an ENSO event on vital rates (mortality, growth, and reproduction) of the dioecious understorey palm Chamaedorea elegans. From March 1997 to March 2000 (including the 1998 ENSO year), we subjected 814 mature individuals to one of five defoliation treatments (0–100% of newly produced leaves were removed twice a year), recording mortality, growth (leaf production) and reproduction (inflorescence and seed production) every 6 months. • Increasing defoliation strongly reduced reproduction but had smaller effects on growth and mortality. Among non-defoliated palms, the probability of mortality increased with light availability, likely due to drought stress during the dry season, but this was not the case for the defoliated plants, probably because leaf area removal lowered transpiration and increased the root mass-to-leaf area ratio. During the ENSO year, growth and inflorescence production were stimulated, but survivorship and seed production diminished significantly, independent of defoliation level. • Synthesis. Variation in light availability and the occurrence of severe droughts can strongly affect demographic behaviour of understorey plants such as C. elegans, significantly influencing the effects of defoliation. Thus, strong episodic disturbance events (such as ENSO, insect outbreaks, strong storms, fires and landslides) should be taken into account to adequately understand the mechanisms that determine the population dynamics of forest plants and the potential for sustainable utilization of non-timber forest products.Journal of Ecology 07/2009; 97(5):1050 - 1061. · 5.69 Impact Factor
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ABSTRACT: Measurements of new production based on uptake of 15N-labeled nitrate in the equatorial Pacific are compared with estimates derived from empirical and theoretical models. Average f-ratios and new production are predicted to within 10–20% by a theoretical steady-state model in which temperature and primary production are the independent variables that determine new production. Examination of the results reveals that the theoretical model gives a very accurate representation of the pattern in new production at primary production rates below ∼60–70 mmol C m−2 d−1 but systematically underestimates new production at higher primary production rates. The discrepancy between measured and predicted new production rates is significantly (p<0.005) correlated with mean euphotic zone nitrate concentrations and drops to zero at nitrate concentrations less than 3 μM. A likely explanation for the bias is the imbalance between primary production and herbivore grazing that occurs in recently upwelled water. This imbalance cannot be taken into account in a steady-state model. At nitrate concentrations less than 3 μM, the new production characteristics of the system closely resemble those predicted by the steady-state model. An empirical model, based on data collected prior to 1979, significantly overestimates new production in the equatorial Pacific at primary production rates above roughly 20 mmol C m−2 d−1. Likely causes of the bias in the empirical model are the need to take temperature effects into account and artifacts in rate measurements made prior to the widespread acceptance of the need to use clean sampling and incubation techniques.Deep Sea Research Part I Oceanographic Research Papers 02/2004; 51(2):205-211. · 2.83 Impact Factor
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ABSTRACT: Abstract The birds nest fern, Asplenium nidus, contributes greatly to the epiphytic biomass in the canopies of both south-east Asia and tropical north Queensland rainforests. It is generally believed that their abundance and their capacity to store water is an important feature for habitat fragmentation in the canopy. We investigated the microclimate of A. nidus and the effects of severe drought periods on the A. nidus population over a 20-year period, hypothesizing that water availability is the most important factor controlling the population under drought conditions. One of two neighbouring A. nidus plants of the same size and age was irrigated artificially before, during and after a significant dry period in 2000. By monitoring the microclimate within and around both ferns we were able to estimate that four continuous weeks of rainless weather completely dried out the accumulated humus of the non-irrigated A. nidus fern. Prolonged dry periods were shown to kill the roots of A. nidus, which attach the fern to the bark and eventually the affected A. nidus on verticals stems fell to the ground. Periods longer than 8 weeks may even kill adult plants sitting in more protected branch forks. Analysis of the whole A. nidus population within the 1-ha Canopy Crane plot and the determination of the morphological age of all plants enabled an evaluation of the historical development of the population. The oldest plant originated in 1985, just 1 year after the longest recorded drought for the site. We suspect that the 1984 drought killed every A. nidus plant within the study plot. Years with low recruitment coincide with years with long drought periods.Austral Ecology 01/2007; 32(1):70 - 76. · 1.74 Impact Factor