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Harmon M.E.,Oregon State University | Bond-Lamberty B.,Pacific Northwest National Laboratory | Tang J.,Ecosystems Center | Vargas R.,Research Center Cientifica Educacion Superior Of Ensenada
Journal of Geophysical Research: Biogeosciences | Year: 2011

Heterotrophic respiration (RH) is a major process releasing carbon to the atmosphere and is essential to understanding carbon dynamics in terrestrial ecosystems. Here we review what is known about this flux as related to forest disturbance using examples from North America. The global R H flux from soils has been estimated at 53-57 Pg C yr-1, but this does not include contributions from other sources (i.e., dead wood, heart-rots). Disturbance-related inputs likely account for 20-50% of all R H losses in forests, and disturbances lead to a reorganization of ecosystem carbon pools that influences how RH changes over succession. Multiple controls on RH related to climate, the material being decomposed, and the decomposers involved have been identified, but how each potentially interacts with disturbance remains an open question. An emerging paradigm of carbon dynamics suggests the possibility of multiple periods of carbon sinks and sources following disturbance; a large contributing factor is the possibility that postdisturbance RH does not always follow the monotonic decline assumed in the classic theory. Without a better understanding and modeling of RH and its controlling factors, it will be difficult to estimate, forecast, understand, and manage carbon balances of regions in which disturbance frequency and severity are changing. Meeting this challenge will require (1) improved field data on processes and stores, (2) an improved understanding of the physiological and environmental controls of R H, and (3) a more formal analysis of how model structure influences the RH responses that can be predicted. Copyright 2011 by the American Geophysical Union. Source

Alvarez-Borrego S.,Research Center Cientifica Educacion Superior Of Ensenada
Botanica Marina | Year: 2012

The Gulf of California has three main natural fertilization mechanisms: upwelling, tidal mixing, and water exchange with the Pacifi c Ocean. Waters high in nutrients occur at very shallow depths in the gulf, and little energy is required for these nutrients to reach the euphotic zone. Upwelling off the eastern coast is strong, chlorophyll a concentration (Chl) can exceed 10 mg m -3, and because of eddy circulation it increases the phytoplankton biomass across the gulf. Because of strong stratifi cation during summer, upwelling off the western coast causes Chl to increase only to - 0.5 mg m -3. The annual cycle is the dominant mode of Chl variability in most of the gulf. El Niño events cause the suppression of Chl mostly in areas on the eastern side of the central and southern gulf, with the effect decreasing from the mouth to the central gulf. 14C data show that highest productivities occur during winter - spring, and in the Guaymas Basin (up to > 4 g C m -2 day -1). Averages of total integrated production (P Tint) for " winter " and for whole regions within the gulf estimated from satellite imagery are in good agreement with averages of 14C estimates (∼ 1.8 g C m -2 day -1). P Tint values for " summer " are ∼ 30 % of those for " winter.". © 2012 by Walter de Gruyter. Source

Cudney R.S.,Research Center Cientifica Educacion Superior Of Ensenada
Optics Express | Year: 2011

A modified Shack-Hartmann wavefront sensor based on an array of electrically controlled zone plates made of ferroelectric domains is presented. The camera used for image acquisition is also used for wavefront sensing. An experimental simulation of the use of this sensor to enhance astronomical images obtained by "Lucky Imaging" is presented. © 2011 Optical Society of America. Source

O'Donnell K.A.,Research Center Cientifica Educacion Superior Of Ensenada
Physical Review Letters | Year: 2011

An experimental study of the dispersion cancellation occurring in frequency-entangled photon pairs is presented. The approach uses time-resolved up-conversion of the pairs, which has temporal resolution at the femtosecond level, and group-delay dispersion sensitivity of 20fs2 under experimental conditions. The cancellation is demonstrated with dispersion stronger than ±103fs2 in the signal (-) and idler (+) modes. © 2011 American Physical Society. Source

Water exchange between the Gulf of California and the Pacific has a significant vertical component. Surface (0-200 m) gulf water flows out into the Pacific and deep (200-600 m) water flows into the gulf. A biogeochemical method is proposed to estimate this vertical component of water exchange assuming steady state for the concentration of nutrients in the gulf and using the net average annual input of nitrate needed to support new phytoplankton production in the whole Gulf of California (P NEW). An annual average P NEW of (2586.7 ± 131.7) × 10 9 mol C yr -1 was deduced from the literature for the whole gulf and for non-El Niño years. Using the Redfield N:C ratio (16:122), the nitrate needed to support P NEW was estimated as (339 ± 17)× 10 9 mol yr -1. Annual representative averages of NO 3, for the mouth of the gulf and for the depth intervals 0-200 m and 200-600 m, were used to calculate the annual average vertical component of water exchange between the gulf and the Pacific to balance the nitrate needed to support P NEW with the net input of nitrate from the Pacific, and the result was (0.67 ± 0.10) Sv in and out of the gulf. This relatively low value, possibly only ~7% of the whole water exchange, indicates that when considering a particular depth most of the time the inflow from the Pacific is equal or very similar to the outflow. Thus, most of the exchange between the gulf and the Pacific consists of the horizontal component. Source

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