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G C (g + c)
Terms modified by G C Selected AbstractsTransport of subarctic large copepods from the Oyashio area to the mixed water region by the coastal Oyashio intrusionFISHERIES OCEANOGRAPHY, Issue 5 2009YUGO SHIMIZU Abstract The lateral transport of organic carbon in large grazing copepods (Neocalanus cristatus, Neocalanus flemingeri, Neocalanus plumchrus and Eucalanus bungii) from the Oyashio area to the mixed water region (MWR) by the coastal Oyashio intrusion was estimated using the data of VMPS (vertical multiple plankton sampler) and 1500 dbar-referred geostrophic transport from the CTD (conductivity temperature depth sensor) data of five cruises during June 2001 to April 2002 on a repeat observation section OICE (Oyashio Intensive observation line off Cape Erimo), which extends southeastward from Hokkaido Island, Japan. The transport to MWR by the coastal Oyashio intrusion was estimated to be 5.3 × 1011 g C for the four species. Data from profiling floats also indicated that the copepods were advected from OICE to MWR by the coastal Oyashio intrusion within about 2 months. This transport is considered to be one of the significant sources of organic carbon in MWR as it is larger than the amount of large zooplankton consumed by Pacific saury (Cololabis saira) in MWR, one of the dominant copepod predators in this region. [source] Peat carbon stocks in the southern Mackenzie River Basin: uncertainties revealed in a high-resolution case studyGLOBAL CHANGE BIOLOGY, Issue 6 2008DAVID W. BEILMAN Abstract The organic carbon (C) stocks contained in peat were estimated for a wetland-rich boreal region of the Mackenzie River Basin, Canada, using high-resolution wetland map data, available peat C characteristic and peat depth datasets, and geostatistics. Peatlands cover 32% of the 25 119 km2 study area, and consist mainly of surface- and/or groundwater-fed treed peatlands. The thickness of peat deposits measured at 203 sites was 2.5 m on average but as deep as 6 m, and highly variable between sites. Peat depths showed little relationship with terrain data within 1 and 5 km, but were spatially autocorrelated, and were generalized using ordinary kriging. Polygon-scale calculations and Monte Carlo simulations yielded a total peat C stock of 982,1025 × 1012 g C that varied in C mass per unit area between 53 and 165 kg m,2. This geostatistical approach showed as much as 10% more peat C than calculations using mean depths. We compared this estimate with an overlapping 7868 km2 portion of an independent peat C stock estimate for western Canada, which revealed similar values for total peatland area, total C stock, and total peat C mass per unit area. However, agreement was poor within ,875 km2 grids owing to inconsistencies in peatland cover and little relationship in peat depth between estimates. The greatest disagreement in mean peat C mass per unit area occurred in grids with the largest peatland cover, owing to the spatial coincidence of large cover and deep peat in our high-resolution assessment. We conclude that total peat C stock estimates in the southern Mackenzie Basin and perhaps in boreal western Canada are likely of reasonable accuracy. However, owing to uncertainties particularly in peat depth, the quality of information regarding the location of these large stocks at scales as wide as several hundreds of square kilometers is presently much more limited. [source] Constraining the Sheffield dynamic global vegetation model using stream-flow measurements in the United KingdomGLOBAL CHANGE BIOLOGY, Issue 12 2005G. Picard Abstract The biospheric water and carbon cycles are intimately coupled, so simulating carbon fluxes by vegetation also requires modelling of the water fluxes, with each component influencing the other. Observations of river streamflow integrate information at the catchment scale and are widely available over a long period; they therefore provide an important source of information for validating or calibrating vegetation models. In this paper, we analyse the performance of the Sheffield dynamic global vegetation model (SDGVM) for predicting river streamflow and quantifying how this information helps to constrain carbon flux predictions. The SDGVM is run for 29 large catchments in the United Kingdom. Annual streamflow estimates are compared with long time-series observations. In 23 out of the 29 catchments, the bias between model and observations is less than 50 mm, equivalent to less than 10% of precipitation. In the remaining catchments, larger errors are because of combinations of unpredictable causes, in particular various human activities and measurement issues and, in two cases, unidentified causes. In one of the catchments, we assess to what extent a knowledge of annual streamflow can constrain model parameters and in turn constrain estimates of gross primary production (GPP). For this purpose, we assume the model parameters are uncertain and constrain them by the streamflow observations using the generalized likelihood uncertainty estimation method. Comparing the probability density function of GPP with and without constraint shows that streamflow effectively constrains GPP, mainly by setting a low probability to GPP values below about 1100 g C,1 m2 yr,1. In other words, streamflow observations allow the rejection of low values of GPP, so that the potential range of possible GPP values is almost halved. [source] The growth respiration component in eddy CO2 flux from a Quercus ilex mediterranean forestGLOBAL CHANGE BIOLOGY, Issue 9 2004S. Rambal Abstract Ecosystem respiration, arising from soil decomposition as well as from plant maintenance and growth, has been shown to be the most important component of carbon exchange in most terrestrial ecosystems. The goal of this study was to estimate the growth component of whole-ecosystem respiration in a Mediterranean evergreen oak (Quercus ilex) forest over the course of 3 years. Ecosystem respiration (Reco) was determined from night-time carbon dioxide flux (Fc) using eddy correlation when friction velocity (u*) was greater than 0.35 m s,1 We postulated that growth respiration could be evaluated as a residual after removing modeled base Reco from whole-ecosystem Reco during periods when growth was most likely occurring. We observed that the model deviated from the night-time Fc -based Reco during the period from early February to early July with the largest discrepancies occurring at the end of May, coinciding with budburst when active aboveground growth and radial growth increment are greatest. The highest growth respiration rates were observed in 2001 with daily fluxes reaching up to 4 g C m,2. The cumulative growth respiration for the entire growth period gave total carbon losses of 170, 208, and 142 g C m,2 for 1999, 2001, and 2002, respectively. Biochemical analysis of soluble carbohydrates, starch, cellulose, hemicellulose, proteins, lignin, and lipids for leaves and stems allowed calculation of the total construction costs of the different growth components, which yielded values of 154, 200, and 150 g C for 3 years, respectively, corresponding well to estimated growth respiration. Estimates of both leaf and stem growth showed very large interannual variation, although average growth respiration coefficients and average yield of growth processes were fairly constant over the 3 years and close to literature values. The time course of the growth respiration may be explained by the growth pattern of leaves and stems and by cambial activity. This approach has potential applications for interpreting the effects of climate variation, disturbances, and management practices on growth and ecosystem respiration. [source] Abundance, Population Structure and Production of Scrobicularia plana and Abra tenuis (Bivalvia: Scrobicularidae) in a Mediterranean Brackish Lagoon, Lake Ichkeul, TunisiaINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 4 2005Caterina Casagranda Abstract Abundance, growth and production of the deposit-feeding bivalves were studied in the Ichkeul wetland, northern Tunisia, from July 1993 , April 1994. Scrobicularia plana(Da Costa, 1778) occurred at annual mean densities (biomasses) of 299 ± 65 to 400 ± 100 individuals/m2 (22.54 ± 3.00 to 34.27 ± 3.96 g ash-free dry mass (AFDM)/m2) depending on the study area. The annual mean density of Abra tenuis(Montagu, 1803) amounted to 640 ± 74 individuals/m2 during the whole study period, in contrast the biomass rose from 2.87 g AFDM/m2 in July to 10.29 g AFDM/m2 in April. Both species were largely dominated by age class I. Although not very successful, recruitment presented a two-period pattern: the main period at the beginning of spring, and a secondary one in late summer/autumn. S. plana rarely exceeded 40 mm and lived for only 2 years, while most individuals of A. tenuis lived for only 15,18 months growing to a length of 12 mm. The annual bivalve deposit-feeder production for the whole lagoon system (90 km2) was 8.24 g AFDM/m2 (5.26 g C/m2, 0.65 g N/m2). The annual P/ ratio was about 0.4 and therefore in the same order of magnitude as estimates from other brackish coastal waters. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Carbon Sequestration in Two Alpine Soils on the Tibetan PlateauJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2009Yu-Qiang Tian Abstract Soil carbon sequestration was estimated in a conifer forest and an alpine meadow on the Tibetan Plateau using a carbon-14 radioactive label provided by thermonuclear weapon tests (known as bomb- 14C). Soil organic matter was physically separated into light and heavy fractions. The concentration spike of bomb- 14C occurred at a soil depth of 4 cm in both the forest soil and the alpine meadow soil. Based on the depth of the bomb- 14C spike, the carbon sequestration rate was determined to be 38.5 g C/m2 per year for the forest soil and 27.1 g C/m2 per year for the alpine meadow soil. Considering that more than 60% of soil organic carbon (SOC) is stored in the heavy fraction and the large area of alpine forests and meadows on the Tibetan Plateau, these alpine ecosystems might partially contribute to "the missing carbon sink". [source] Effects of Climate Change and Shifts in Forest Composition on Forest Net Primary ProductionJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 11 2008Jyh-Min Chiang Abstract Forests are dynamic in both structure and species composition, and these dynamics are strongly influenced by climate. However, the net effects of future tree species composition on net primary production (NPP) are not well understood. The objective of this work was to model the potential range shifts of tree species (DISTRIB Model) and predict their impacts on NPP (PnET-II Model) that will be associated with alterations in species composition. We selected four 200 × 200 km areas in Wisconsin, Maine, Arkansas, and the Ohio-West Virginia area, representing focal areas of potential species range shifts. PnET-II model simulations were carried out assuming that all forests achieved steady state, of which the species compositions were predicted by DISTRIB model with no migration limitation. The total NPP under the current climate ranged from 552 to 908 g C/m2 per year. The effects of potential species redistributions on NPP were moderate (,12% to +8%) compared with the influence of future climatic changes (,60% to +25%). The direction and magnitude of climate change effects on NPP were largely dependent on the degree of warming and water balance. Thus, the magnitude of future climate change can affect the feedback system between the atmosphere and biosphere. [source] | ||||||||||