bluuebunny/crossref_metadata_2025 huggingface dataset:
Fast and accurate irradiance calculations for ecosystem models
Authors: Mobley C. D. , Sundman L. K. , Bissett W. P. , Cahill B.
Published: April 2010

Abstract. Coupled physical-biological-optical ocean ecosystem models often use sophisticated treatments of their physical and biological components, while oversimplifying the optical component to the possible detriment of the ecosystem predictions. To bring optical computations up to the standard required by recent ecosystem models, we developed a computationally fast numerical model, named EcoLight, that solves the azimuthally averaged radiative transfer equation to obtain accurate in-water spectral irradiances for use in calculations of photosynthesis and photo-oxidation. To evaluate its computational features, we incorporated EcoLight into an idealized physical-biological model for open-ocean Case 1 waters and compared ten-year simulations for a simple analytical irradiance model vs. EcoLight numerical calculations. After optimization, the EcoLight run times are less than 30% more than for the analytical irradiance model. Moreover, EcoLight is suitable for use in Case 2 and optically shallow waters, for which no analytical irradiance models exist. EcoLight also computes ancillary quantities such as the remote-sensing reflectance, which can be useful for ecosystem validation.
Measurement and modelling ozone fluxes over a cut and fertilized grassland
Authors: Mészáros R. , Horváth L. , Weidinger T. , Neftel A. , Nemitz E. , Dämmgen U. , Cellier P. , Loubet B.
Published: April 2010

Abstract. During the GRAMINAE intensive field campaign between 20 May and 15 June 2000, ozone flux was measured and modelled above grassland in northern Germany, Braunschweig. Results of flux measurement and model calculations are presented in this study. Effects of agricultural activities (cut and fertilization) on ozone fluxes have also been analysed. A detailed deposition model for ozone is used to parameterise and to calculate the deposition velocity and flux of the ozone. Model calculations also provide an evaluation of the ratio of stomatal and non-stomatal fluxes. Measured and modelled flux and deposition velocity values have been compared for each period (before cut of grass, after cut, and after fertilization). Results show that agricultural activities hardly have any influence on total O3 fluxes, although both cutting and fertilization have complex impacts on different deposition pathways. Reduced vegetation decreased the stomatal exchange, while at the same time for this short canopy, the role of both soil emission of NO (promoting ozone loss close to the surface) and deposition of ozone to soil surface have increased. These effects demonstrate the importance of canopy structure and non-stomatal pathways on O3 fluxes.
Dissolution of atmospheric cobalt and zinc in seawater
Authors: Thuróczy C.-E. , Boye M. , Losno R.
Published: April 2010

Abstract. Atmospheric dust inputs to the open ocean are major source of trace metals bioavailable for the phytoplankton after their dissolution in seawater. Among them, cobalt (Co) and zinc (Zn) are essential for the growth and for the distribution of major phytoplankton taxon such as coccolithophorids and diatoms. The solubility in seawater of Co and Zn present in atmospheric dusts was studied using an open-flow reactor with and without light irradiation. The analyses of cobalt and Zinc were conducted using voltammetric methods and the global elemental composition of dust determined by ICP-AES. This study highlights the role of the dust origin in revealing the solubility characteristics. Higher dust solubility was found for zinc as compared to cobalt. Cobalt in anthropogenic particles is much more soluble in seawater than in natural particles after 2 h of dissolution. Zinc showed opposite solubilities, higher in natural particles than in anthropogenics. This work is a contribution to ongoing studies which focus on the impact of atmospheric inputs of trace metals onto the primary production.
Effects of long-term high CO2 exposure on two species of coccolithophores
Authors: Müller M. N. , Schulz K. G. , Riebesell U.
Published: April 2010

Abstract. The physiological performance of two coccolithophore species, Emiliania huxleyi and Coccolithus braarudii, was investigated during long-term exposure to elevated pCO2 levels. Mono-specific cultures were grown over 152 (E. huxleyi) and 65 (C. braarudii) generations while pCO2 was gradually increased to maximum levels of 1150 μatm (E. huxleyi) and 930 μatm (C. braarudii) and kept constant thereafter. Rates of cell growth and cell quotas of particulate organic carbon (POC), particulate inorganic carbon (PIC) and total particulate nitrogen (TPN) were determined repeatedly throughout the incubation period. Increasing pCO2 caused a decrease in cell growth rate of 9% and 29% in E. huxleyi and C. braarudii, respectively. In both species cellular PIC:TPN and PIC:POC ratios decreased in response to rising pCO2, whereas no change was observed in the POC:TPN ratios of E. huxleyi and C. braarudii. These results are consistent with those obtained in shorter-term high CO2 exposure experiments following abrupt pertubations of the seawater carbonate system, indicating that for the strains tested here i) a gradual CO2 increase does not alleviate CO2/pH sensitivity, and ii) observed CO2 sensitivities are persistent over multiple generations.
Dynamics of ammonia exchange with cut grassland: synthesis of results and conclusions of the GRAMINAE Integrated Experiment
Authors: Sutton M. A. , Nemitz E. , Milford C. , Campbell C. , Erisman J. W. , Hensen A. , Cellier P. , David M. , Loubet B. , Personne E. , Schjoerring J. K. , Mattsson M. , Dorsey J. R. , Gallagher M. W. , Horvath L. , Weidinger T. , Meszaros R. , Dämmgen U. , Neftel A. , Herrmann B. , Lehman B. E. , Flechard C. , Burkhardt J.
Published: April 2010

Abstract. Improved data on biosphere-atmosphere exchange are fundamental to understanding the production and fate of ammonia (NH3) in the atmosphere. The GRAMINAE Integrated Experiment combined novel measurement and modelling approaches to provide the most comprehensive analysis of the interactions to date. Major inter-comparisons of micrometeorological parameters and NH3 flux measurements using the aerodynamic gradient method and relaxed eddy accumulation (REA) were conducted. These showed close agreement, though the REA systems proved insufficiently precise to investigate vertical flux divergence. Grassland management had a large effect on fluxes: Emissions increased after grass cutting (−50 to 700 ng m−2 s−1 NH3) and after N-fertilization (0 to 3800 ng m−2 s
Upscaling of gross ecosystem production to the landscape scale using multi-temporal Landsat images, eddy covariance measurements and a footprint model
Authors: Chen B. , Ge Q. , Fu D. , Liu G. , Yu G. , Sun X. , Wang S. , Wang H.
Published: April 2010

Abstract. In order to use the global available eddy-covariance (EC) flux dataset and remote sensing measurements to provide estimates of gross primary production (GPP) at landscape (101–102km2), regional (103–106km2) and global land surface scales, we developed a satellite-based GPP algorithm using Landsat data and an upscaling framework. The satellite-based GPP algorithm uses two improved vegetation indices (Enhanced Vegetation Index – EVI, Land Surface Water Index – LSWI). The upscalling framework involves flux footprint climatology modeling and data-model fusion. This approach was first applied to an evergreen coniferous stand in South China subtropical monsoon climatic zone. The EC measurements at Qian Yinzhou tower site (26° 44'48'' N, 115° 04'13'' E), which belongs to the Chinaflux network, and the Landsat images for this region in 2004 were used in this study. The seasonal dynamics of GPP predicted by the satellite-based algorithm agreed well with observed GPP in 2004 at this site. These results demonstrate the potential of combining of the satellite-based algorithm, flux footprint modeling and data-fusion, for scaling-up of GPP at the CO2 flux tower sites, a key component for the study of the carbon cycle at regional and global scales.
Nitrogen stable isotopes of ammonium and nitrate in high mountain lakes of the Pyrenees
Authors: Bartrons M. , Camarero L. , Catalan J.
Published: April 2010

Abstract. Nitrogen stable isotopes (δ15N) are increasingly used to trace food web relationships and the flow of matter in lakes. However, there is high variability in δ15N among primary producers and other primary energy resources that can eventually propagate throughout the lake food web. To increase our understanding of the origin of this variability, we measured ammonium and nitrate δ15N in atmospheric deposition (AD), epilimnetic water (EW), deep chlorophyll maximum water (DCMW), and sediment porewater (SPW) in eight mountain lakes. A general δ15N (−3.4‰) for AD was estimated as the signature for AD ammonium and nitrate did not differ. All lakes showed similar high δ15N-NH4+ values for SPW (ca. 2.2‰). In contrast, the variability among lakes in water column values was high, although differences between EW and DCMW within a lake were low. δ15N-NO3- correlated with the altitude of the lakes, and its variability was interpreted as the influence of catchment nitrification, which is higher in talus landscapes. δ15N-NH4+ distribution had two modes, positive values (ca. 3‰) were associated to DCMW of shallow lakes, and probably reflect the SPW influence. Lower values (ca. −3‰) occur in EW and DCMW of deep lakes, and its variability was related to the degree that NO3- was up taken by primary producers and recycled within the food-web when NH4+ availability was low compared to demand. Overall, altitude, lake depth and seasonal cumulative primary production largely explain the patterns of δ15N variability observed in nitrogen dissolved compounds.
The ACCENT-VOCBAS field campaign on biosphere-atmosphere interactions in a Mediterranean ecosystem of Castelporziano (Rome): site characteristics, climatic and meteorological conditions, and eco-physiology of vegetation
Authors: Fares S. , Mereu S. , Scarascia Mugnozza G. , Vitale M. , Manes F. , Frattoni M. , Ciccioli P. , Loreto F.
Published: April 2010

Abstract. Biosphere-atmosphere interactions were investigated on a sandy dune Mediterranean ecosystem in a field campaign held in 2007 within the frame of the European Projects ACCENT and VOCBAS. The campaign was carried out in the Presidential estate of Castelporziano, a peri-urban park close to Rome where several investigations on the emission of biogenic volatile organic compounds (BVOC) in Mediterranean area were performed in the past 15 y. While specific aspects of the campaign will be discussed in companion papers, the general climatic and physiological aspects will be presented here together with information regarding BVOC emission from the most common plants present in this ecosystem. During the campaign regular air movements were observed, dominated by moderate nocturnal land breeze and diurnal sea breeze. A regular daily increase of ozone concentration in the air was also observed, but daily peaks of ozone were much lower than those measured downwind of the Rome conurbation. The site was ideal as a natural photochemical reactor to observe reaction, transport and deposition processes occurring in the Mediterranean basin, where a sea-land breeze circulation system allows a strong mixing between biogenic and anthropogenic emissions and secondary pollutants. The campaign investigated emissions from a poorly studied and largely biodiverse ecosystem, often subjected to a combination of environmental stresses and to anthropogenic pollution. Measurements were run in May, when plant physiological conditions were still optimal, in absence of severe drought and heat stress. Foliar rates of photosynthesis and transpiration were as high as generally recorded in unstressed Mediterranean sclerophyllous plants. Most of the plant species emitted high level of monoterpenes, despite measurements being made in a period in which emissions of volatile isoprenoids could be restrained by developmental and environmental factors, such as leaf age and relatively low air temperature. No high isoprene emitting plants were found in the ecosystem. It is speculated that environmental stresses limit the emission during summer, differently than in other Mediterranean ecosystems. Accounting for the high spring emission of the dune ecosystem may be important to correct current algorithms at regional, ecosystem levels, and to interpret measurements of fluxes of volatile isoprenoids and pollutants.
Ion microprobe assessment of the heterogeneity of Mg/Ca, Sr/Ca and Mn/Ca ratios in Pecten maximus and Mytilus edulis (bivalvia) shell calcite precipitated at constant temperature
Authors: Freitas P. S. , Clarke L. J. , Kennedy H. , Richardson C. A.
Published: April 2010

Abstract. Small-scale heterogeneity of biogenic carbonate elemental composition can be a significant source of error in the accurate use of element/Ca ratios as geochemical proxies. In this study ion microprobe (SIMS) profiles showed significant small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca ratios in new shell calcite of the marine bivalves P. maximus and Mytilus edulis that was precipitated during a constant-temperature culturing experiment. Elevated Mg/Ca, Sr/Ca and Mn/Ca ratios were found to be associated with the deposition of elaborate shell features, i.e. a shell surface stria in P. maximus and surface shell disturbance marks in both species, the latter a common occurrence in bivalve shells. In both species the observed small-scale elemental heterogeneity most likely was not controlled by variable transport of ions to the extra-pallial fluid, but by factors such as shell Mg content influencing Sr and Mn heterogeneity, the influence of shell organic content and/or conditions at the shell crystal-solution interface. Invariant Mg/Ca ratios observed in the mid and innermost regions of the P. maximus shell suggests a potential application as a palaeotemperature proxy.
On observational and modelling strategies targeted at regional carbon exchange over continents
Authors: Gerbig C. , Dolman A. J. , Heimann M.
Published: April 2010

Abstract. Estimating carbon exchange at regional scales is paramount to understanding feedbacks between climate and the carbon cycle, but also to verifying climate change mitigation such as emission reductions and strategies compensating for emissions such as carbon sequestration. This paper discusses evidence for a number of important shortcomings of current generation modelling frameworks designed to provide regional scale budgets. Current top-down and bottom-up approaches targeted at deriving consistent regional scale carbon exchange estimates for biospheric and anthropogenic sources and sinks are hampered by a number of issues: We show that top-down constraints using point measurements made from tall towers, although sensitive to larger spatial scales, are however influenced by local areas much stronger than previously thought. On the other hand, classical bottom-up approaches using process information collected at the local scale, such as from eddy covariance data, need up-scaling and validation on larger scales. We therefore argue for a combination of both approaches, implicitly providing the important local scale information for the top-down constraint, and providing the atmospheric constraint for up-scaling of flux measurements. Combining these data streams necessitates quantifying their respective representation errors, which are discussed. The impact of these findings on future network design is highlighted, and some recommendations are given.
Planktic foraminiferal shell thinning in the Arabian Sea due to anthropogenic ocean acidification?
Authors: de Moel H. , Ganssen G. M. , Peeters F. J. C. , Jung S. J. A. , Brummer G. J. A. , Kroon D. , Zeebe R. E.
Published: April 2010

Abstract. About one third of the anthropogenic carbon dioxide (CO2) released into the atmosphere in the past two centuries has been taken up by the ocean. As CO2 invades the surface ocean, carbonate ion concentrations and pH are lowered. Laboratory studies indicate that this reduces the calcification rates of marine calcifying organisms, including planktic foraminifera. Such a reduction in calcification resulting from anthropogenic CO2 emissions has not been observed, or quantified in the field yet. Here we present the findings of a study in the Western Arabian Sea that uses shells of the surface water dwelling planktic foraminifer Globigerinoides ruber in order to test the hypothesis that anthropogenically induced acidification has reduced shell calcification of this species. We found that light, thin-walled shells from the surface sediment are younger (based on 14C and δ13C measurements) than the heavier, thicker-walled shells. Shells in the upper, bioturbated, sediment layer were significantly lighter compared to shells found below this layer. These observations are consistent with a scenario where anthropogenically induced ocean acidification reduced the rate at which foraminifera calcify, resulting in lighter shells. On the other hand, we show that seasonal upwelling in the area also influences their calcification and the stable isotope (δ13C and δ18O) signatures recorded by the foraminifera shells. Plankton tow and sediment trap data show that lighter shells were produced during upwelling and heavier ones during non-upwelling periods. Seasonality alone, however, cannot explain the 14C results, or the increase in shell weight below the bioturbated sediment layer. We therefore must conclude that probably both the processes of acidification and seasonal upwelling are responsible for the presence of light shells in the top of the sediment and the age difference between thick and thin specimens.
Calcification of the cold-water coral Lophelia pertusa under ambient and reduced pH
Authors: Maier C. , Hegeman J. , Weinbauer M. G. , Gattuso J.-P.
Published: April 2010

Abstract. The cold-water coral Lophelia pertusa is one of the few species able to build reef-like structures and a 3-dimensional coral framework in the deep oceans. Furthermore, deep cold-water coral bioherms are likely among the first marine ecosystems to be affected by ocean acidification. Colonies of L. pertusa were collected during a cruise in 2006 to cold-water coral bioherms of the Mingulay reef complex (Hebrides, North Atlantic). Calcium-45 labelling was conducted shortly after sample collection onboard. After this method proved to deliver reliable data, the same experimental approach was used to assess calcification rates and the effect of lowered pH during a~cruise to the Skagerrak (North Sea) in 2007. The highest calcification rates were found in youngest polyps with up to 1% d−1 new skeletal growth and average values of 0.11±0.02% d−1(±S.E.). Lowering the pH by 0.15 and 0.3 units relative to ambient pH resulted in a strong decrease in calcification by 30 and 56%, respectively. The effect of changes in pH on calcification was stronger for fast growing, young polyps (59% reduction) than for older polyps (40% reduction) which implies that skeletal growth of young and fast calcifying corallites will be influenced more negatively by ocean acidification. Nevertheless, L. pertusa revealed a positive net calcification (as indicated by 45Ca incorporation) at an aragonite saturation state (Ωa) below 1, which may indicate some adaptation to an environment that is already relatively low in Ωa compared to tropical or temperate coral bioherms.
Sensible and latent heat flux from radiometric surface temperatures at the regional scale: methodology and validation
Authors: Miglietta F. , Gioli B. , Brunet Y. , Hutjes R. W. A. , Matese A. , Sarrat C. , Zaldei A.
Published: April 2010

Abstract. The CarboEurope Regional Experiment Strategy (CERES) was designed to develop and test a range of methodologies to assess regional surface energy and mass exchange of a large study area in the south-western part of France. This paper describes a methodology to estimate sensible and latent heat fluxes on the basis of net radiation, surface radiometric temperature measurements and information obtained from available products derived from the Meteosat Second Generation (MSG) geostationary meteorological satellite, weather stations and ground-based eddy covariance towers. It is based on a simplified bulk formulation of sensible heat flux that considers the degree of coupling between the vegetation and the atmosphere and estimates latent heat as the residual term of net radiation. Estimates of regional energy fluxes obtained in this way are validated at the regional scale by means of a comparison with direct flux measurements made by airborne eddy-covariance. The results show an overall good matching between airborne fluxes and estimates of sensible and latent heat flux obtained from radiometric surface temperatures that holds for different weather conditions and different land use types. The overall applicability of the proposed methodology to regional studies is discussed.
After trees die: quantities and determinants of necromass across Amazonia
Authors: Chao K.-J. , Phillips O. L. , Baker T. R. , Peacock J. , Lopez-Gonzalez G. , Vásquez Martínez R. , Monteagudo A. , Torres-Lezama A.
Published: April 2010

Abstract. The Amazon basin, one of the most substantial biomass carbon pools on earth, is characterised by strong macroecological gradients in biomass, mortality rates, and wood density from the west to the east. These gradients could affect necromass stocks, but this has not yet been tested. This study aims to assess the stocks and determinants of necromass patterns across Amazonian forests. Field-based and literature data were used to find relationships between necromass and possible determinants. The final regression result was used to estimate and extrapolate the necromass stocks across terra firma Amazonian forests. In eight northwestern and three northeastern Amazonian permanent plots, volumes of coarse woody debris (≥10 cm diameter) were measured in the field and density of each decay class was estimated. Forest structure and historical mortality data were used to determine controlling factors of necromass. Necromass is greater in forests with low stem mortality rates (northeast) rather than forest with high stem mortality rates (northwest) (58.5±10.6 and 27.3±3.2 Mg ha−1, respectively). After integrating all published necromass values, we find that necromass across terra firma forests in Amazonia is positively related to stand biomass, mortality mass input, and average wood density of live trees (ρBA j). We applied these relationships to estimate necromass for plots where necromass has not been measured. The estimates, together with other actual measurements of necromass, were scaled-up to project a total Amazonian necromass of 9.6±1.0 Pg C. The ratio of necromass (on average weighted by forest region) to coarse aboveground biomass is 0.127. Overall, we find (1) a strong spatial trend in necromass in parallel with other macroecological gradients and (2) that necromass is a substantial component of the carbon pool in the Amazon.
Net loss of CaCO3 from coral reef communities due to human induced seawater acidification
Authors: Andersson A. J. , Kuffner I. B. , Mackenzie F. T. , Jokiel P. L. , Rodgers K. S. , Tan A.
Published: April 2010

Abstract. Acidification of seawater owing to oceanic uptake of atmospheric CO2 originating from human activities such as burning of fossil fuels and land-use changes has raised serious concerns for its adverse effects on corals, coral reefs and carbonate communities in general. Here we demonstrate a transition from net accumulation towards net loss of calcium carbonate (CaCO3) material owing to decreased calcification and increased carbonate dissolution from replicated subtropical coral reef communities (n=3) incubated in continuous-flow mesocosms subject to present and future seawater conditions. The calcifying community was dominated by the coral Montipora capitata. Daily average community calcification or Net Ecosystem Calcification (NEC = CaCO3 production – dissolution) was positive at 4.5 mmol CaCO3 m−2 h−1 under ambient seawater pCO2 conditions as opposed to negative at −0.1 mmol CaCO3 m−2 h−1 under seawater conditions of double the ambient pCO2. These experimental results provide support for the conclusion that some net calcifying communities could become subject to net dissolution in response to anthropogenic ocean acidification within this century.
Detecting regional variability in sources and sinks of carbon dioxide: a synthesis
Authors: Dolman A. J. , Gerbig C. , Noilhan J. , Sarrat C. , Miglieta F.
Published: April 2010

Abstract. The papers of this special issue are put into the context of progress made in experiments and modelling aimed at understanding the carbon balance at regional scale. Mesoscale meteorological effects such as seas breezes and topographically induced flow have the potential to generate significant heterogeneities in the CO2 concentration fields. This has consequences for the interpretation or inverse modelling, of sources and sinks from these concentrations. Results of experiments executed in South West France in 2005 and 2007 are described and subsequent analysis of modelling results. Overall we conclude that we now have capability to model with mesoscale models realistic CO2 concentration fields, within the constraint of other model errors, such as in boundary layer characteristics. We show that progress has been made in inverting concentration field at regional scale and indicate the direction of future research efforts.
Key Arctic pelagic mollusc (Limacina helicina) threatened by ocean acidification
Authors: Comeau S. , Gorsky G. , Jeffree R. , Teyssié J.-L. , Gattuso J.-P.
Published: April 2010

Abstract. Thecosome pteropods (shelled pelagic molluscs) can play an important role in the food web of various ecosystems and play a key role in the cycling of carbon and carbonate. Since they harbor an aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The impact of changes in the carbonate chemistry was investigated on Limacina helicina, a key species of Arctic ecosystems. Pteropods were kept in culture under controlled pH conditions corresponding to pCO2 levels of 350 and 760 μatm. Calcification was estimated using a fluorochrome and the radioisotope 45Ca. It exhibits a 28% decrease at the pH value expected for 2100 compared to the present pH value. This result supports the concern for the future of pteropods in a high-CO2 world, as well as of those species dependent upon them as a food resource. A decline of their populations would likely cause dramatic changes to the structure, function and services of polar ecosystems.
The impact of a declining water table on observed carbon fluxes at a northern temperate wetland
Authors: Sulman B. N. , Desai A. R. , Cook B. D. , Saliendra N. , Mackay D. S.
Published: April 2010

Abstract. Wetland biogeochemistry is strongly influenced by water and temperature dynamics, and these interactions are currently poorly represented in ecosystem and climate models. A decline in water table of approximately 6 cm/year was observed at a wetland in northern Wisconsin, USA over a period from 2001–2007. Eddy covariance measurements of carbon dioxide exchange in conjunction with the declining water table revealed an increase in ecosystem respiration of over 20% as water table depth fell through a range between 5 and 35 cm below the surface. Ecosystem respiration was not correlated with water table outside of this range. The limits of the range were dependent on temperature, with the effect of water table penetrating deeper at higher temperatures. Yearly average ecosystem production was approximately 20% higher in years with low water table than in years with high water table. As the water table declined, evapotranspiration decreased and ecosystem water use efficiency increased. Wetland net ecosystem exchange was not correlated with water table, but in 2007, a year with an exceptionally dry growing season, the wetland site was a net carbon source. These results suggest that changes in hydrology may not have a large impact on wetland carbon flux over inter-annual time scales due to opposing responses in both ecosystem respiration and productivity. However, this balance appears to be sensitive to changes in the seasonal distribution of precipitation.
Carbon dioxide and methane annual emissions from two boreal reservoirs and nearby lakes in Quebec, Canada
Authors: Demarty M. , Bastien J. , Tremblay A.
Published: April 2010

Abstract. The results of dissolved GHG (CO2 and CH4) measurement campaigns carried out in Quebec (Canada) during the open-water periods and under-ice in a newly created reservoir (Eastmain 1), a 25 year old reservoir (Robert-Bourassa) and in three reference lakes are presented. While CO2 partial pressures varied with season with a net increase under the ice cover, CH4 partial pressures did not. We were able to extrapolate the highest CO2 partial pressures reached in the different studied systems just before ice break-up with high spring emission period. We then estimated the springtime CO2 fluxes and compared them to annual CO2 fluxes and GHG fluxes. Thus we clearly demonstrated that in our systems CH4 fluxes was of minor importance in the GHG emissions, CO2 fluxes representing around 90% of the annual fluxes. We also pointed out the importance of springtime emissions in the annual budget.
Carbon emissions from deforestation in the Brazilian Amazon region predicted from satellite data and ecosystem modeling
Authors: Potter C. , Klooster S. , Genovese V.
Published: April 2010

Abstract. A simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate monthly carbon fluxes in terrestrial ecosystems of Brazilian Amazon and Cerrado regions over the period 2000–2002. The NASA-CASA (Carnegie Ames Stanford Approach) model estimates of annual forest production were used as the basis to generate a prediction for the standing pool of carbon in above-ground biomass (AGB; g C m−2) for forested areas of the Brazilian Amazon region. Plot-level measurements of the residence time of carbon in wood in Amazon forest from Malhi et al. (2006) were interpolated by inverse distance weighting algorithms and used with CASA to generate a new regional map of AGB. Data from the Brazilian PRODES (Estimativa do Desflorestamento da Amazônia) project were used to map deforested areas. Results show that net primary production (NPP) sinks for carbon are highest across the eastern and northern Amazon areas, whereas deforestation sources of CO2 flux from decomposition of residual woody debris are more rapid and less seasonal in the central Amazon than in the eastern and southern areas. Increased woody debris from past deforestation events was predicted to alter the net ecosystem carbon balance of the Amazon region to generate annual CO2 source fluxes at least two times higher than previously predicted by CASA modeling studies. Variations in climate, land cover, and forest burning were predicted to release carbon at rates of 0.5 to 1 Pg C yr−1 from the Brazilian Amazon. When direct carbon emissions from forest burning of between 0.2 and 0.6−1 in the Legal Amazon are overlooked in regional budgets, the year-to-year variations in this net biome flux may appear to be large, whereas our model results implies net biome fluxes had actually been relatively consistent from year to year during the period 2000–2002.
Effect of CO2-related acidification on aspects of the larval development of the European lobster, Homarus gammarus (L.)
Authors: Arnold K. E. , Findlay H. S. , Spicer J. I. , Daniels C. L. , Boothroyd D.
Published: April 2010

Abstract. Oceanic uptake of anthropogenic CO2 results in a reduction in pH termed "Ocean Acidification" (OA). Comparatively little attention has been given to the effect of OA on the early life history stages of marine animals. Consequently, we investigated the effect of culture in CO2-acidified sea water (approx. 1200 ppm, i.e. average values predicted using IPCC 2007 A1F1 emissions scenarios for year 2100) on early larval stages of an economically important crustacean, the European lobster Homarus gammarus. Culture in CO2-acidified sea water did not significantly affect carapace length or development of H. gammarus. However, there was a reduction in carapace mass during the final stage of larval development in CO2-acidified sea water. This co-occurred with a reduction in exoskeletal mineral (calcium and magnesium) content of the carapace. As the control and high CO2 treatments were not undersaturated with respect to any of the calcium carbonate polymorphs measured, the physiological alterations we record are most likely the result of acidosis or hypercapnia interfering with normal homeostatic function, and not a direct impact on the carbonate supply-side of calcification per se. Thus despite there being no observed effect on survival, carapace length, or zoeal progression, OA related (indirect) disruption of calcification and carapace mass might still adversely affect the competitive fitness and recruitment success of larval lobsters with serious consequences for population dynamics and marine ecosystem function.
Impact of CO2-driven ocean acidification on invertebrates early life-history – What we know, what we need to know and what we can do
Authors: Dupont S. , Thorndyke M. C.
Published: April 2010

Abstract. As a consequence of increasing atmospheric CO2, the world's oceans are becoming more acidic and the rate of change is increasingly fast. This ocean acidification is expected to have significant physiological, ecological and evolutionary consequences at many organizational levels of marine biodiversity. Alarmingly little is known about the long term impact of predicted pH changes (a decrease of −0.3/−0.4 units for the end of this century) on marine invertebrates in general and their early developmental stages in particular, which are believed to be the more sensitive to environmental disturbances, are essential as unit of selection, recruitment and population maintenance. Ocean acidification (OA) research is in its infancy and although the field is moving forward rapidly, good data are still scarce. Available data reveal contradictory results and apparent paradoxes. In this article, we will review available information both from published sources and work in progress, drawing a general picture of what is currently known, with an emphasis on early life-history larval stages. We will also discuss what we need to know in a field with very limited time resources to obtain data and where there is a high expectation that the scientific community should rapidly be able to provide clear answers that help politicians and the public to take action. We will also provide some suggestions about what can be done to protect and rescue future ecosystems.
Fine root dynamics for forests on contrasting soils in the colombian Amazon
Authors: Jiménez E. M. , Moreno F. H. , Lloyd J. , Peñuela M. C. , Patiño S.
Published: April 2010

Abstract. It has been hypothesized that in a gradient of increase of soil resources carbon allocated to belowground production (fine roots) decreases. To evaluate this hypothesis, we measured the mass and production of fine roots (<2 mm) by two methods: 1) ingrowth cores and, 2) sequential soil coring, during 2.2 years in two lowland forests with different soils in the colombian Amazon. Differences of soil resources were determined by the type and physical and chemical properties of soil: a forest on loamy soil (Ultisol) at the Amacayacu National Natural Park and, the other on white sands (Spodosol) at the Zafire Biological Station, located in the Forest Reservation of the Calderón River. We found that mass and production of fine roots was significantly different between soil depths (0–10 and 10–20 cm) and also between forests. White-sand forest allocated more carbon to fine roots than the clayey forest; the production in white-sand forest was twice (2.98 and 3.33 Mg C ha−1 year−1, method 1 and 2, respectively) as much as in clayey forest (1.51 and 1.36–1.03 Mg C ha−1 year−1, method 1 and 2, respectively); similarly, the average of fine root mass was higher in the white-sand forest (10.94 Mg C ha−1) than in the forest on clay soils (3.04–3.64 Mg C ha−1). The mass of fine roots also showed a temporal variation related to rainfall, such that production of fine roots decreased substantially in the dry period of the year 2005. Our results suggest that soil resources play an important role in patterns of carbon allocation in these forests; carbon allocated to above-and belowground organs is different between forest types, in such a way that a trade-off above/belowground seems to exist; as a result, it is probable that there are not differences in total net primary productivity between these two forests: does belowground offset lower aboveground production in poorer soils?
Conditional CO2 flux analysis of a managed grassland with the aid of stable isotopes
Authors: Zeeman M. J. , Tuzson B. , Emmenegger L. , Knohl A. , Buchmann N. , Eugster W.
Published: April 2010

Abstract. Short statured managed ecosystems, such as agricultural grasslands, exhibit high temporal changes in carbon dioxide assimilation and respiration fluxes for which measurements of the net CO2 flux, e.g. by using the eddy covariance (EC) method, give only limited insight. We have therefore adopted a recently proposed concept for conditional EC flux analysis of forest to grasslands, in order to identify and quantify daytime sub-canopy respiration fluxes. To validate the concept, high frequency (≈5 Hz) stable carbon isotope analyis of CO2 was used. We made eddy covariance measurements of CO2 and its isotopologues during four days in August 2007, using a novel quantum cascade laser absorption spectrometer, capable of high time resolution stable isotope analysis. The effects of a grass cut during the measurement period could be detected and resulted in a sub-canopy source conditional flux classification, for which the isotope composition of the CO2 could be confirmed to be of a respiration source. However, the conditional flux method did not work for an undisturbed grassland canopy. We attribute this to the flux measurement height that was chosen well above the roughness sublayer, where the natural isotopic tracer (δ13C) of respiration was too well mixed with background air.
Skill assessment of the PELAGOS global ocean biogeochemistry model over the period 1980–2000
Authors: Vichi M. , Masina S.
Published: April 2010

Abstract. Global Ocean Biogeochemistry General Circulation models are useful tools to study biogeochemical processes at gobal and large scales under current climate and future scenario conditions. The accuracy of the future estimate is however dependent on the adequate representation of the current ocean biogeochemical features. To this purpose, the results of an interannual simulation of the global ocean biogeochemical model PELAGOS have been objectively compared with multi-variate observations from the last 20 years of the XX century. The model was assessed in terms of spatial and temporal variability of chlorophyll and primary production derived from satellite sensors, with a specific focus on the simulation of carbon production/consumption rates observed in the equatorial Pacific ocean and at the long-term JGOFS stations. The predicted chlorophyll is acceptable in the northern mid-latitude regions and equatorial Pacific, but is underestimated in the upwelling regions of the Atlantic and Indian Oceans and markedly overestimated in the Southern Ocean. This latter bias is linked to the inadequate representation of the mixed layer seasonal cycle in the region, which favours primary production during austral spring. Simulated primary production is comparable with satellite estimates both at the global scale and when compared with an independent data-set in the equatorial Pacific. A comparison with other models showed that PELAGOS results are as good as the estimates from state-of-the-art diagnostic models based on satellite data. The skill in reproducing the interannual varibility was assessed in the equatorial Pacific and against the decadal JGOFS timeseries BATS and HOT. In the tropical Pacific our analysis suggests that interannual variability of primary production is related to the climate variability both in the observations and in the model. At the JGOFS stations PELAGOS has skill to simulate the observed bacterial biomass and shows realistic means of primary and bacterial production at BATS. These results have been further strenghtened with an analysis of spatial variability of microbial carbon production/consumption and comparison with observations along a transect in the Atlantic ocean. Within the limits of the model assumption and known biases, PELAGOS predicts that the system is net heterotrophic if the boreal winter period only is considered and especially in the more oligotrophic regions. However, at the annual time scale and over the global ocean, the model suggests that surface ocean is close to a slightly positive autotrophic balance in accordance with recent experimental findings and geochemical evidences.
Coastal hypoxia and sediment biogeochemistry
Authors: Middelburg J. J. , Levin L. A.
Published: April 2010

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.
Chemical and physical properties of Amazon forest soils in relation to their genesis
Authors: Quesada C. A. , Lloyd J. , Schwarz M. , Patiño S. , Baker T. R. , Czimczik C. , Fyllas N. M. , Martinelli L. , Nardoto G. B. , Schmerler J. , Santos A. J. B. , Hodnett M. G. , Herrera R. , Luizão F. J. , Arneth A. , Lloyd G. , Dezzeo N. , Hilke I. , Kuhlmann I. , Raessler M. , Brand W. A. , Geilmann H. , Moraes Filho J. O. , Carvalho F. P. , Araujo Filho R. N. , Chaves J. E. , Cruz Junior O. F. , Pimentel T. P. , Paiva R.
Published: April 2010

Abstract. Soil samples were collected in six South American countries in a total of 71 different 1 ha forest plots across the Amazon Basin as part of the RAINFOR project. They were analysed for total and exchangeable cations, C, N, pH with various P fractions also determined. Physical properties were also examined and an index of soil physical quality proposed. A diverse range of soils was found. For the western areas near the Andean cordillera and the southern and northern fringes, soils tend to be distributed among the lower pedogenetic levels, while the central and eastern areas of Amazonia have more intensely weathered soils. This gives rise to a large variation of soil chemical and physical properties across the Basin, with soil properties varying predictably along a gradient of pedogenic development. Nutrient pools generally increased slightly in concentration from the youngest to the intermediate aged soils after which a gradual decline was observed with the lowest values found in the most weathered soils. Soil physical properties were strongly correlated with soil fertility, with favourable physical properties occurring in highly weathered and nutrient depleted soils and with the least weathered, more fertile soils having higher incidence of limiting physical properties. Soil phosphorus concentrations varied markedly in accordance with weathering extent and appear to exert an important influence on the nitrogen cycle of Amazon forest soils.
Regional and large-scale patterns in Amazon forest structure and function are mediated by variations in soil physical and chemical properties
Authors: Quesada C. A. , Lloyd J. , Schwarz M. , Baker T. R. , Phillips O. L. , Patiño S. , Czimczik C. , Hodnett M. G. , Herrera R. , Arneth A. , Lloyd G. , Malhi Y. , Dezzeo N. , Luizão F. J. , Santos A. J. B. , Schmerler J. , Arroyo L. , Silveira M. , Priante Filho N. , Jimenez E. M. , Paiva R. , Vieira I. , Neill D. A. , Silva N. , Peñuela M. C. , Monteagudo A. , Vásquez R. , Prieto A. , Rudas A. , Almeida S. , Higuchi N. , Lezama A. T. , López-González G. , Peacock J. , Fyllas N. M. , Alvarez Dávila E. , Erwin T. , di Fiore A. , Chao K. J. , Honorio E. , Killeen T. , Peña Cruz A. , Pitman N. , Núñez Vargas P. , Salomão R. , Terborgh J. , Ramírez H.
Published: April 2010

Abstract. Forest structure and dynamics have been noted to vary across the Amazon Basin in an east-west gradient in a pattern which coincides with variations in soil fertility and geology. This has resulted in the hypothesis that soil fertility may play an important role in explaining Basin-wide variations in forest biomass, growth and stem turnover rates. To test this hypothesis and assess the importance of edaphic properties in affect forest structure and dynamics, soil and plant samples were collected in a total of 59 different forest plots across the Amazon Basin. Samples were analysed for exchangeable cations, C, N, pH with various P fractions also determined. Physical properties were also examined and an index of soil physical quality developed. Overall, forest structure and dynamics were found to be strongly and quantitatively related to edaphic conditions. Tree turnover rates emerged to be mostly influenced by soil physical properties whereas forest growth rates were mainly related to a measure of available soil phosphorus, although also dependent on rainfall amount and distribution. On the other hand, large scale variations in forest biomass could not be explained by any of the edaphic properties measured, nor by variation in climate. A new hypothesis of self-maintaining forest dynamic feedback mechanisms initiated by edaphic conditions is proposed. It is further suggested that this is a major factor determining forest disturbance levels, species composition and forest productivity on a Basin wide scale.