Potential and limitations of finite element modelling in assessing structural integrity of coralline algae under future global change
Summary: Using Finite element modelling (FEM) we show that a simplified geometric FE-model can predict the structural strength of the coralline algal skeleton. We compared a series of 3D geometric FE-models with increasing complexity to a biologically accurate model derived from computed tomography (CT) scan data. Using geometric models provides the basis for a better understanding of the potential effect of climate change on the structural integrity of these organisms.
Transmissivity of solar radiation within a Picea sitchensis stand under various sky conditions
Summary: We tested the hypothesis that diffuse radiation from cloudy and overcast skies penetrates the canopy more effectively than direct radiation from clear skies. We compared the flux density and spectral properties of direct and diffuse radiation above, within and below a forest stand under sunny, cloudy and overcast conditions in a thinned Sitka spruce forest. We recorded vertical (1m resolution) and horizontal (2.5m resolution) profiles of radiation penetration at 1nm resolution.
Drivers and uncertainties of future global marine primary production in marine ecosystem models
Summary: We analyze changes of marine net primary production (NPP) and its drivers for the 21st century in 9 marine ecosystem models under the RCP8.5 scenario. NPP decreases in 5 models, increases in 1 model and 3 models show no significant trend. The main drivers include stronger nutrient limitation, but in many models warming-induced increases in phytoplankton growth outbalance the nutrient effect. Temperature-driven increases in grazing and other loss processes cause a net decrease in biomass and NPP.
C. Laufkötter, M. Vogt, N. Gruber, M. Aita-Noguchi, O. Aumont, L. Bopp, E. Buitenhuis, S. C. Doney, J. Dunne, T. Hashioka, J. Hauck, T. Hirata, J. John, C. Le Quéré, I. D. Lima, H. Nakano, R. Seferian, I. Totterdell, M. Vichi, and C. Völker Biogeosciences Discuss., 12, 3731-3824, 2015 AbstractDiscussion Paper (PDF, 7324 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
27 Feb 2015
Modeling photosynthesis of discontinuous plant canopies by linking Geometric Optical Radiative Transfer model with biochemical processes
Summary: We advance the Geometric Optical Radiative Transfer model and derive analytical solutions to radiation absorption by sunlit/shaded leaves. We link the radiative transfer process with biochemical diffusion process to model canopy photosynthesis. Modeled Gross Primary Production could explain more than 80% variance of flux tower measurements at both hourly and daily scales. Ambient CO2 concentration influences daytime photosynthesis, which needs to be considered in terrestrial ecosystem models.
Ground cover rice production system facilitates soil carbon and nitrogen stocks at regional scale
M. Liu, M. Dannenmann, S. Lin, G. Saiz, G. Yan, Z. Yao, D. Pelster, H. Tao, S. Sippel, Y. Tao, Y. Zhang, X. Zheng, Q. Zuo, and K. Butterbach-Bahl Biogeosciences Discuss., 12, 3647-3674, 2015 AbstractDiscussion Paper (PDF, 578 KB)Supplement (227 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
27 Feb 2015
Spatio-temporal analysis of nitrogen cycling in a mixed coniferous forest of the northern United States
Summary: We used stable nitrogen isotopes from red pine trees to determine the history of nitrogen cycling within the Deming Lake watershed at Itasca State Park. With nearly 250 years of data, results suggest a major decline in nitrogen availability in red pine beginning in the early 20th century. We believe this synchronous decline is the result of the fire suppression in the state park, which has allowed the emergence of competing understory species.
Sediment CO2 efflux from cleared and intact temperate mangroves and tidal flats
Summary: We investigated the impact of temperate mangrove clearance on CO2 efflux from the sediment to the atmosphere. Our results suggest that carbon stored within temperate mangrove sediment is released over a period of years to decades after mangrove clearance. Disturbance of the surface biofilm resulted in elevated CO2 efflux across all habitats, suggesting the important role of surface biofilm communities in mediating CO2 efflux.
The contribution of tephra constituents during biogenic silica determination: implications for soil and paleoecological studies
Summary: Biogenic silica (BSi) is used as a proxy by soil scientists to identify biological effects on the Si cycle and by paleoecologists to study environmental changes. We show the presence of tephra constituents can make measurements erroneous at low BSi concentrations, with repercussions for soil and paleoecological studies. However, we also show that glass shards do not produce an identical dissolution signal to that of BSi, meaning they can be distinguished with appropriate experimental setups.
W. Clymans, L. Barão, N. Van der Putten, S. Wastegård, G. Gísladóttir, S. Björck, B. Moine, E. Struyf, and D. J. Conley Biogeosciences Discuss., 12, 3505-3545, 2015 AbstractDiscussion Paper (PDF, 1471 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
25 Feb 2015
Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, Northeast China
Representing northern peatland microtopography and hydrology within the Community Land Model
X. Shi, P. E. Thornton, D. M. Ricciuto, P. J. Hanson, J. Mao, S. D. Sebestyen, N. A. Griffiths, and G. Bisht Biogeosciences Discuss., 12, 3381-3418, 2015 AbstractDiscussion Paper (PDF, 1243 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
20 Feb 2015
Sources and transfer mechanisms of dissolved organic matter during storm and inter-storm conditions in a lowland headwater catchment: constraints from high-frequency molecular data
Summary: The origin of stream dissolved organic matter (DOM) in a lowland headwater catchment was investigated using high frequency sampling combined with chemical biomarkers analysis. Inter-storm stream DOM corresponds to the flushing of soil DOM reservoirs, while storm stream DOM would also result from three additional mechanisms: biofilm destabilization, surface and sub-surface erosion.
Deriving seasonal dynamics in ecosystem properties of semi-arid savannas using in situ based hyperspectral reflectance
Summary: Relationships between ecosystem properties of semi-arid savanna and reflected solar radiance between 350-1800 nm were investigated. Normalised combinations of reflectance for the near infrared, shortwave infrared, and 600 to 700 nm were strongly affected by solar and viewing angular effects. Ecosystem properties of savannas were strongly correlated to reflectance 350-1800nm, and normalised combinations of reflectance were strong predictors of the savanna ecosystem properties.
Redox regime shifts in microbially-mediated biogeochemical cycles
Summary: Despite their global importance redox reactions mediated by micro-organisms are often crudely represented in biogeochemical models. We show that including the dynamics of microbial growth in such a model can cause sudden shifts between redox states in response to an environmental change. We identify the conditions required for these redox regime shifts, and predict that they are likely in the modern day sulfur and nitrogen cycles, and potentially the iron cycle in the ancient ocean.
Ideas and Perspectives: On the emission of amines from terrestrial vegetation in the context of atmospheric new particle formation
Summary: In this article we summarise recent science, which shows how airborne amines, specifically methylamines (MAs), play a key role in atmospheric new particle formation (NPF) by stabilising small molecule clusters. Agricultural emissions are assumed to constitute the most important MA source, but given the short atmospheric residence time of MAs, they can hardly have a direct impact on NFP events observed in remote regions. This leads us to the presentation of existing knowledge focussing on natural
Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska
Summary: Tundra fires may have increased as a result of anthropogenic climate change. To evaluate this hypothesis in the context of natural variability, we reconstructed fire history of the late Quaternary in the Alaskan tundra. Fire-return intervals are spatially variable, ranging from 1648 to 6045 years at our sites. The rarity of historical fires implies that increased fire frequency may greatly alter the structure and function of tundra ecosystems.
M. L. Chipman, V. Hudspith, P. E. Higuera, P. A. Duffy, R. Kelly, W. W. Oswald, and F. S. Hu Biogeosciences Discuss., 12, 3177-3209, 2015 AbstractDiscussion Paper (PDF, 1858 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
12 Feb 2015
Identifying climatic drivers of tropical forest dynamics
Summary: We used a forest dynamic model, calibrated with data from the 20-year study site of Paracou, French Guiana, to test a set of climatic variables on tree growth and mortality probabilities. Severe droughts decreased annual growth and mortality rates, high precipitation increased mortality rates and high temperature decreased tree growth. Best resistance to drought was found for trees with high wood density and for trees with small current diameters.
Global soil nitrous oxide emissions in a dynamic carbon–nitrogen model
Summary: The response of terrestrial nitrous oxide production to global change is strongly controlled by the response of tropical soils. We show - by applying a new model – that global N2O production is strongly sensitive to temperature, but the sensitivity is dampened if CO2 increase co-occurs.
Growth and production of the copepod community in the southern area of the Humboldt Current System
Summary: Increasing coastal upwelling in the Humboldt Current is negatively affecting zooplankton biomass and secondary production, as reflected in a gradual decrease in copepod biomass in recent years. A more extended upwelling period causes substantial loss of copepod biomass from the coastal zone due to offshore advection. Excess of upwelling, induced by climate change, may thus negatively impact biological production at lower trophic levels in this highly productive large marine ecosystem.
Growth response of temperate mountain grasslands to inter-annual variations of snow cover duration
Summary: It is shwon that inter-annual variations in the primary productivity of mountain grasslands are primarily governed by variations in the length of the snow-free period and to a much lesser extent by temperature and precipitation during the growing season. Meteorological variables controlling snow cover dynamics are thus of paramount importance to understand and model the amount and timing of biomass production in mountain pastures.
Environmental controls on the boron and strontium isotopic composition of aragonite shell material of cultured Arctica islandica
Summary: We report the first high-resolution strontium (87Sr/86Sr and δ88/86Sr) and boron (δ11B) isotopic values in the aragonite shell of cultured Arctica islandica. These results suggest that well-preserved sub-fossil specimens may be use to determine the past Sr isotopic composition of seawater. The δ11B in this experiment suggests that the boron uptake of the shell changes at a temperature threshold of 13 °C and a species-specific fractionation factor may be required for seawater pH reconstructions.
Monitoring seasonal and diurnal changes in photosynthetic pigments with automated PRI and NDVI sensors
Summary: NDVI and PRI sensors (SRS, Decagon Inc.) exhibited complementary responses during spring photosynthetic activation in evergreen and deciduous stands. In evergreens, PRI was most strongly influenced by changing chlorophyll:carotenoid pool sizes over the several weeks of the study, while it was most affected by xanthophyll cycle pigment activity at the diurnal time scale. These automated PRI and NDVI sensors offer new ways to explore environmental and physiological constraints on photosynthesis.
Carbon export and transfer to depth across the Southern Ocean Great Calcite Belt
Summary: The transfer of particulate organic carbon (POC) into the deep ocean is an important atmospheric carbon dioxide sink. Concentration and flux measurements from the Southern Ocean Great Calcite Belt region show that the relationship between POC and biogenic mineral fluxes varies with depth, from the surface to 1000 meters below. The results suggest that the transfer of POC into the deep ocean is more closely related to phytoplankton community structure than to mineral composition alone.
High methane emissions dominate annual greenhouse gas balances 30 years after bog rewetting
M. Vanselow-Algan, S. R. Schmidt, M. Greven, C. Fiencke, L. Kutzbach, and E.-M. Pfeiffer Biogeosciences Discuss., 12, 2809-2842, 2015 AbstractDiscussion Paper (PDF, 1004 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
10 Feb 2015
Temperature-dependence of the relationship between pCO2 and dissolved organic carbon in lakes
Summary: The relationship between the pCO2 and DOC concentration was tested in a Tropical area. Unlike the positive relationship reported for lake waters before, we found no significant relationship in our lakes, despite very broad ranges in both pCO2 and DOC. The strength of pCO2 vs. DOC relationships declines with increasing water temperature, suggesting substantial differences in carbon cycling in warm lakes, which must be considered when upscaling limnetic carbon cycling to global scales.
Modelling the climatic drivers determining photosynthesis and carbon allocation in evergreen Mediterranean forests using multiproxy long time series
Summary: We developed a process-based model for evergreen Mediterranean forests. We used multiproxy data including eddy covariance CO2 flux and annual growth dendrochronological time series. The model explicitly takes into account the influence of climatic variability to calculate photosynthesis and carbon allocation. We analyzed long-time acclimation processes and climatic trade-offs between the C-source and the C-sink. There is much potentiality to apply the model at a larger scale.
G. Gea-Izquierdo, F. Guibal, R. Joffre, J. M. Ourcival, G. Simioni, and J. Guiot Biogeosciences Discuss., 12, 2745-2786, 2015 AbstractDiscussion Paper (PDF, 4840 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
06 Feb 2015
Storage and transformation of organic matter fractions in cryoturbated permafrost soils across the Siberian Arctic
N. Gentsch, R. Mikutta, R. J. E. Alves, J. Barta, P. Čapek, A. Gittel, G. Hugelius, P. Kuhry, N. Lashchinskiy, J. Palmtag, A. Richter, H. Šantrůčková, J. Schnecker, O. Shibistova, T. Urich, B. Wild, and G. Guggenberger Biogeosciences Discuss., 12, 2697-2743, 2015 AbstractDiscussion Paper (PDF, 4486 KB)Supplement (9891 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
06 Feb 2015
Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model
Summary: Results are presented from a numerical model that explicitly includes spectral
irradiance and optically important water constituents. The model captures 3D
biogeochemical, ecosystem and optical observations, including surface
reflectance analogous to ocean colour satellite observations. Sensitivity
experiments demonstrate the relative importance of each of the water
constituents, and the feedbacks between the light field, fitness of
phytoplankton types and the biogeochemistry of the ocean.
S. Dutkiewicz, A. E. Hickman, O. Jahn, W. W. Gregg, C. B. Mouw, and M. J. Follows Biogeosciences Discuss., 12, 2607-2695, 2015 AbstractDiscussion Paper (PDF, 8113 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
04 Feb 2015
Experimental assessment of environmental influences on the stable isotopic composition of Daphnia pulicaria and their ephippia
Summary: We show that the stable (C, N, O) isotopic composition of the water flea Daphnia pulicaria is strongly related to that of the diet (C, N) and the water they live in (O). We also show that the stable isotopic composition of the sheaths of Daphnia resting eggs (ephippia) is indicative of the isotopic composition of Daphnia that produced them. This implies that stable isotope ratios of fossil Daphnia ephippia can provide information on past ecological and climatic developments in and around lakes.
J. Schilder, C. Tellenbach, M. Möst, P. Spaak, M. van Hardenbroek, M. J. Wooller, and O. Heiri Biogeosciences Discuss., 12, 2573-2606, 2015 AbstractDiscussion Paper (PDF, 423 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BG
04 Feb 2015
Changes in soil carbon, nitrogen and phosphorus due to land-use changes in Brazil
J. D. Groppo, S. R. M. Lins, P. B. Camargo, E. D. Assad, H. S. Pinto, S. C. Martins, P. R. Salgado, B. Evangelista, E. Vasconcellos, E. E. Sano, E. Pavão, R. Luna, and L. A. Martinelli Biogeosciences Discuss., 12, 2533-2571, 2015 AbstractDiscussion Paper (PDF, 979 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
04 Feb 2015
Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration
Summary: In the southern parts of the Sierra Nevada Mountains in California, we investigated erosion of carbon and nitrogen from low-order catchments. We found that eroded sediments were OM rich, with a potential for significant gaseous and dissolved loss of OM during transport or after depositional in downslope or downstream depositional landform positions.
Coupled isotopes of plant wax and hemicellulose markers record information on relative humidity and isotopic composition of precipitation
Summary: Stable water isotopes (18O/16O and 2H/1H) are invaluable proxies for paleoclimate research. Here we use a coupled 18O/16O and 2H/1H biomarker approach based on plant-derived sugars and n-alkanes. Applying this innovative approach to a topsoil transect allows (i) calculating the deuterium-excess of leaf water as proxy for relative humidity and (ii) calculating the plant source water isotopic composition (~precipitation). The approach is validated by the presented climate transect results.
M. Tuthorn, R. Zech, M. Ruppenthal, Y. Oelmann, A. Kahmen, H. F. del Valle, T. Eglinton, and M. Zech Biogeosciences Discuss., 12, 2459-2489, 2015 AbstractDiscussion Paper (PDF, 2065 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
04 Feb 2015
The role of photo- and thermal degradation for CO2 and CO fluxes in an arid ecosystem
Summary: Recent studies have suggested the potential importance of abiotic decomposition (photodegradation) in arid ecosystems. This study focuses on the measurement and understanding of abiotic fluxes. Photodegradation fluxes have not been observed. Thermal degradation fluxes were observed in the field (for CO) and in the laboratory (for CO2). Previous studies have potentially overestimated the role of photodegradation or misinterpreted thermal degradation fluxes as photodegradation fluxes.
H. van Asperen, T. Warneke, S. Sabbatini, G. Nicolini, D. Papale, and J. Notholt Biogeosciences Discuss., 12, 2429-2457, 2015 AbstractDiscussion Paper (PDF, 604 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for BG
04 Feb 2015
Mesozooplankton structure and functioning during the onset of the Kerguelen phytoplankton bloom during the Keops2 survey
Technical Note: Cost-efficient approaches to measure carbon dioxide (CO2) fluxes and concentrations in terrestrial and aquatic environments using mini loggers
Summary: Measurements of concentrations and fluxes of carbon dioxide (CO2) are fundamental for our understanding of carbon cycling and greenhouse gas balances. We are presently limited by the high cost of such measurements making it difficult to properly investigate variability in space and time. This study presents measurement approaches that are very resource efficient in terms of equipment cost and measurement labour time, opening new opportunities to advance our knowledge on CO2 across landscapes.
Relationship between N : P : Si ratio and phytoplankton community composition in a tropical estuarine mangrove ecosystem
Summary: The present work aims at understanding importance of Brzezinski-Redfield ratio as a determinant of natural phytoplankton community composition in a mangrove ecosystem. Results show that nutrient concentrations were intricately balanced that never became limited and complemented well with concept of modified Redfield ratio in study area. Based on microscopy and rbcL sequencing, we show recent concepts of phytoplankton functional traits and elemental stoichiometry also occur in mangrove habitat.
Assessment of model estimates of land–atmosphere CO2 exchange across Northern Eurasia
Summary: Each year the forests and tundra of Northern Eurasia sequester carbon dioxide (CO2), helping to offset sources to the atmosphere such as fossil fuel emissions. We used results from climate models to better understand the region's land-atmosphere CO2 exchange from 1960-1990. Model estimates were assessed in comparisons to independent ground and satellite measurements. The model suggest the region is storing less carbon over time, and the stored carbon is cycling through soils more quickly.
M. A. Rawlins, A. D. McGuire, J. K. Kimball, P. Dass, D. Lawrence, E. Burke, X. Chen, C. Delire, C. Koven, A. MacDougall, S. Peng, A. Rinke, K. Saito, W. Zhang, R. Alkama, T. J. Bohn, P. Ciais, B. Decharme, I. Gouttevin, T. Hajima, D. Ji, G. Krinner, D. P. Lettenmaier, P. Miller, J. C. Moore, B. Smith, and T. Sueyoshi Biogeosciences Discuss., 12, 2257-2305, 2015 AbstractDiscussion Paper (PDF, 4493 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
03 Feb 2015
The dynamic of annual carbon allocation to wood in European forests is consistent with a combined source-sink limitation of growth: implications for modelling
Summary: We provide an evaluation of the spatio-temporal dynamics of annual carbon allocation to wood in European forests. Our study supports the premise that European forest growth is under a complex control including both source and sink limitations. The relative influences of the different growth drivers strongly vary across years and spatial ecological gradients. We suggest a straightforward modelling framework to implement these combined forest growth limitations into terrestrial biosphere models.
Fundamental molecules of life are pigments which arose and evolved to dissipate the solar spectrum
Summary: We show that the fundamental molecules of life (those common to all three domains of life; archea, bacteria, and eukaryote) including nucleotides, amino acids, enzyme cofactors, and porphyrin agglomerates, absorb light strongly from 230 to 280nm (in the UV-C) and have chemical affinity to RNA and DNA. This supports the "thermodynamic dissipation theory for the origin of life" which suggests that life and evolution got its start by dissipating the prevailing Archean UV-C sunlight into heat.
Patterns and persistence of hydrologic carbon and nutrient export from collapsing upland permafrost
Summary: As high latitudes warm, carbon and nitrogen stored in permafrost soil will be vulnerable to erosion and transport to Arctic streams and rivers. We sampled outflow from 83 permafrost collapse features in Alaska. Permafrost collapse caused substantial increases in dissolved organic carbon and inorganic nitrogen but decreased methane concentration by 90%. Upland thermokarst may be a dominant linkage transferring carbon and nutrients from terrestrial to aquatic ecosystems as the Arctic warms.
Understanding emissions of ammonia from buildings and application of fertilizers: an example from Poland
Summary: A Europe-wide dynamic ammonia emissions model has been applied for one of the largest agricultural countries in Europe, and its sensitivity on the distribution of emissions among different agricultural functions was analysed. The results suggest that the dynamic emission model is most sensitive to emission from animal manure, in particular how this is connected to national regulations. In contrast, the model is most robust with respect to emission from buildings and storage.
Seasonal dynamics of organic carbon and metals in thermokarst lakes from the discontinuous permafrost zone of western Siberia
Summary: A year-around hydrochemical study (including full winter freezing and spring flood) of shallow thermokarst lakes from a discontinuous permafrost zone of western Siberia revealed conceptually new features of element concentration evolution over different seasons within a large scale of the lake size.
R. M. Manasypov, S. N. Vorobyev, S. V. Loiko, I. V. Kritzkov, L. S. Shirokova, V. P. Shevchenko, S. N. Kirpotin, S. P. Kulizhsky, L. G. Kolesnichenko, V. A. Zemtzov, V. V. Sinkinov, and O. S. Pokrovsky Biogeosciences Discuss., 12, 1975-2019, 2015 AbstractDiscussion Paper (PDF, 2338 KB)Supplement (1877 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for BGSpecial Issue
30 Jan 2015
WETCHIMP-WSL: intercomparison of wetland methane emissions models over West Siberia
Summary: We evaluated 21 forward models and 5 inversions over West Siberia, in terms of CH4 emissions and simulated wetland areas and compared these results to an intensive in situ CH4 flux dataset, several wetland maps, and two satellite inundation products. In addition to assembling a definitive collection of methane emissions estimates for the region, we were able to identify the types of wetland maps and model features necessary for accurate simulations of high-latitude wetlands.
T. J. Bohn, J. R. Melton, A. Ito, T. Kleinen, R. Spahni, B. D. Stocker, B. Zhang, X. Zhu, R. Schroeder, M. V. Glagolev, S. Maksyutov, V. Brovkin, G. Chen, S. N. Denisov, A. V. Eliseev, A. Gallego-Sala, K. C. McDonald, M. A. Rawlins, W. J. Riley, Z. M. Subin, H. Tian, Q. Zhuang, and J. O. Kaplan Biogeosciences Discuss., 12, 1907-1973, 2015 AbstractDiscussion Paper (PDF, 5971 KB)Supplement (138 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
30 Jan 2015
Microbial communities responsible for fixation of CO2 revealed by using mcrA, cbbM, cbbL, fthfs, fefe-hydrogenase genes as molecular biomarkers in petroleum reservoirs of different temperatures
J.-F. Liu, S. M. Mbadinga, X.-B. Sun, G.-C. Yang, S.-Z. Yang, J.-D. Gu, and B.-Z. Mu Biogeosciences Discuss., 12, 1875-1906, 2015 AbstractDiscussion Paper (PDF, 951 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
30 Jan 2015
Phosphorus release capacity of soluble P fertilizers and insoluble rock phosphate in response to phosphate solubilizing bacteria and poultry manure and their effect on plant growth promotion and P utilization efficiency of chilli (Capsicum annuum L.)
Summary: P release capacity of soil amended with RP varied between 6.0–11.5mg kg-1 while the soluble P fertilizers i.e. SSP and DAP displayed a maximum of 73 and 68mg P kg-1 at the start of the experiment (day 0). However, the P released tendency from SSP and DAP declined during incubation and at the end 82 and 79% of P initially present had been lost from the mineral pool. Integrated use of PSB and PM with RP in ½RP+½PM+PSB treatment stimulated P mineralization by releasing a maximum of 25mg P kg-1.
Bayesian inversions of a dynamic vegetation model in four European grassland sites
Summary: We invert the CARAIB dynamic vegetation model with eddy covariance data from 4 European grassland sites, using a Markov chain Monte Carlo sampler. Although eddy covariance data are known to show heteroscedasticity, accounting for a heteroscedastic model of the residual errors in the inversion do not fully remove heteroscedasticity and lead to poorer agreements between measured and modelled data. Parameter values are compared between the four sites and are related to their characteristics.
Response of soil microorganisms to radioactive oil waste: results from a leaching experiment
Summary: Toxicity and effects on various soil microbial parameters of oily waste containing radionuclides in a leaching column experiment were estimated. Microbial metabolic quotient and cellulase activity were mainly influenced by oily components of the waste, but not by radionuclides, and the effect was more pronounced in the upper layer of the column. In opposite, structure of bacterial community analyzed using PCR-SSCP, was shown to be affected by both hydrocarbons and radioactivity.
P. Galitskaya, L. Biktasheva, A. Saveliev, S. Ratering, S. Schnell, and S. Selivanovskaya Biogeosciences Discuss., 12, 1753-1789, 2015 AbstractDiscussion Paper (PDF, 797 KB)Interactive Discussion (Open, 6 Comments)Manuscript under review for BG
29 Jan 2015
Scaling impacts on environmental controls and spatial heterogeneity of soil organic carbon stocks
Disruption of metal ion homeostasis in soils is associated with nitrogen deposition-induced species loss in an Inner Mongolia steppe
Summary: We demonstrate that N addition reduced species richness, acidified soil and disturbed nutrient homeostasis in soil in an Inner Mongolia steppe. We further reveal that an increase in inorganic-N concentration, depletion of base cations (Ca2+ and Mg2+) and mobilization of Mn2+ and Cu2+ in soils were involved in reduction in species richness in the temperate steppe of northern China, highlighting the involvment of nutrient mobilization in decline in species richness of alkaline grasslands.
Seasonality of sea ice controls interannual variability of summertime ΩA at the ice shelf in the Eastern Weddell Sea – an ocean acidification sensitivity study
Summary: As anthropogenic CO2 increases and sea ice dynamics change with climate, understanding the trend in these characteristics of variability in the seasonal drivers of ΩA will become increasingly important. We investigate the major drivers of interannual to seasonal scale variability of ΩA. We show that the critical climate (physical-biogeochemical) sensitivities for ΩA at the Antarctic ice self are the timing and rate of sea ice thaw and the resulting onset and persistence of phytoplankton blooms.
Assessing the potential of amino acid δ13C patterns as a carbon source tracer in marine sediments: effects of algal growth conditions and sedimentary diagenesis
Summary: A tiny fraction of marine algae escapes decomposition and is buried in sediments, but tools are needed to track the fate of algal organic carbon. We tested whether naturally occurring isotope variability among amino acids from algae and bacteria can be used as source fingerprints. We found that isotope fingerprints track algal amino acid sources with high fidelity across different growth conditions, and that the fingerprints can be used to quantify bacterial amino acids in sediments.
First on-line isotopic characterization of N2O emitted from intensively managed grassland
B. Wolf, L. Merbold, C. Decock, B. Tuzson, E. Harris, J. Six, L. Emmenegger, and J. Mohn Biogeosciences Discuss., 12, 1573-1611, 2015 AbstractDiscussion Paper (PDF, 2378 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BG
23 Jan 2015
Impact of seawater carbonate chemistry on the calcification of marine bivalves
Wet-season spatial variability of N2O emissions from a tea field in subtropical central China
Summary: We examined the spatial variability of N2O emissions from a tea field in a wet season using 147 static chambers. The N2O fluxes for a 30-min snapshot ranged from -1.73 to 1,659.11 g N ha-1 d-1 (average flux of 102.24 g N ha-1d-1). Cokriging with NH4Nt and NO3Nt as covariables (r=0.74 and RMSE=1.18) outperformed ordinary kriging (r=0.18 and RMSE=1.74), regression kriging with the sample position as a predictor (r=0.49 and RMSE=1.55) and cokriging with SOCt as a covariable (r=0.58 and RMSE=1.44).
Reconstruction of super-resolution fields of ocean pCO2 and air–sea fluxes of CO2 from satellite imagery in the Southeastern Atlantic
Summary: We have reconstructed maps of air-sea CO2 fluxes at high resolution (4 km) offshore of the Benguela region using Sea Surface Temperature and ocean colour data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km).
The inferred representation of pCO2 improves the description provided by CarbonTracker, enhancing the small scale variability.
We obtain that not only the resolution, but the inferred pCO2 data itself is closer to in-situ measurements of pCO2.
Predictors and mechanisms of the drought-influenced mortality of tree species along the isohydric to anisohydic continuum in a decade-long study of a central US temperate forest
Summary: Co-occurring tree species with varying physiologies were continuously monitored for mortality with concurrent observations of key physiological and environmental variables for a decade in a central US forest. New predictors of drought-induced mortality were developed. Time-delayed mortality was shown to be nonlinearly related to drought intensity and to species’ capacities in regulating their internal hydraulic status with elevated risk associated with extreme isohydric and anisohydric behaviors
Downward particle flux and carbon export in the Beaufort Sea, Arctic Ocean; the Malina experiment
Summary: POC fluxes obtained in the Eastern Beaufort Sea in August 2009 from drifting sediment traps were low (1-15 mg C m-2d-1), compared to long-term data which show higher but variable fluxes (10-40 mg C m-2d-1).
Composition of sinking particles, especially faecal pellets, highlighted the role of the zooplankton community and its trophic structure in the transition of carbon from the productive surface zone to the deep ocean, which was driven by heterotrophy compared to autotrophy during spring bloom.
Pleistocene sediment offloading and the global sulfur cycle
Summary: We present a new Quaternary S-isotope record of seawater sulfate. We
find that the steady decline in the seawater S-isotope ratios stops
around 700ka which we relate to the termination of the massive net
“sediment offloading”and a new equilibrium state between shelf erosion
during sea level lowstands and sediment resupply during sea level high
Modelling the effect of soil moisture and organic matter degradation on biogenic NO emissions from soils in Sahel rangeland (Mali)
Summary: This study provides seasonal and inter annual variation of biogenic NO emission fluxes in a Sahelian rangeland in Mali, a region where intense NO emissions occur during the wet season. Emissions are related to their biogeochemical origin, to the quantity of biomass, to the quantity of livestock, which drive the N pool and N turnover in the soil. This study gives an insight in the different N inputs to the soil and in N production processes in the soil at the origin of the emission.
Constraints on the applicability of the organic temperature proxies UK'37, TEX86 and LDI in the subpolar region around Iceland
Summary: This research reports a test the applicability of three organic-derived temperature proxies (UK'37, TEX86 and LDI) at high latitudes around Iceland. A range of samples including suspended particular material (SPM), trapped descending particles and surface sediments were collected for testing the different proxies in the water column and the sediment.The combination of three independent SST organic proxies provided important information about seasonality or differences in habitat depth.
M. Rodrigo-Gámiz, S. W. Rampen, H. de Haas, M. Baas, S. Schouten, and J. S. Sinninghe Damsté Biogeosciences Discuss., 12, 1113-1153, 2015 AbstractDiscussion Paper (PDF, 3409 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
16 Jan 2015
The impact of atmospheric CO2 and N management on simulated yields and tissue C : N in the main wheat regions of Western Europe
S. Olin, G. Schurgers, M. Lindeskog, D. Wårlind, B. Smith, P. Bodin, J. Holmér, and A. Arneth Biogeosciences Discuss., 12, 1047-1111, 2015 AbstractDiscussion Paper (PDF, 3775 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BG
16 Jan 2015
Carbon stocks and soil sequestration rates of riverine mangroves and freshwater wetlands
Summary: Riverine wetlands of the Pacific coast of Mexico had large ecosystem C stocks (784.5 MgC ha-1 for mangroves, 722.2 MgC ha-1 for peat swamps, and 336.5 MgC ha-1 for marshes). Long-term soil C sequestration values in mangroves were 1.3 ± 0.2 MgC ha-1yr-1. C stocks and soil nitrogen stocks were in general larger for upland compared to lowland mangroves
Primary productivity and its correlation with rainfall on Aldabra Atoll
J. Shekeine, L. A. Turnbull, P. Cherubini, R. de Jong, R. Baxter, D. Hansen, N. Bunbury, F. Fleischer-Dogley, and G. Schaepman-Strub Biogeosciences Discuss., 12, 981-1013, 2015 AbstractDiscussion Paper (PDF, 3976 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BG
16 Jan 2015
Carbon budget estimation of a subarctic catchment using a dynamic ecosystem model at high spatial resolution
Large fluxes and rapid turnover of mineral-associated carbon across topographic gradients in a humid tropical forest: insights from paired 14C analysis
Summary: We used measurements of radiocarbon to model the decomposition of organic matter associated with minerals in tropical rainforest soils, using contemporary and archived samples. Most organic matter decomposed over 10 to 30 years, while a smaller portion decomposed over centuries. Rates were similar among soils with strongly differing physical and chemical properties, but declined with a proxy for oxygen limitation. Previous models based on one time point may underestimate decomposition rates.
Seasonal dynamics of nitrogen fixation and the diazotroph community in the temperate coastal region of the northwestern North Pacific
Summary: The temperate coastal ocean is one of the regions where nitrogen fixation rates have been understudied and potentially underestimated. Active nitrogen fixation occurred and nifH sequences of UCYN-A were recovered when surface nitrate was depleted. Although nitrogen fixation was not detected in nitrate-rich waters in spring and winter, nifH sequences were recovered. The Cluster III diazotrophs, putative anaerobic bacteria, were found from the surface throughout years and sometimes dominated.
How can effect the synergy of climate change, soil units and vegetation groups the potential global distribution of plants up to 2300: a modelling study for prediction of potential global distribution and migration of the N2 fixing species Alnus spp.
Investigating the usefulness of satellite derived fluorescence data in inferring gross primary productivity within the carbon cycle data assimilation system
Summary: We investigate the utility of satellite measurements of chlorophyll fluorescence (Fs) in constraining gross primary productivity (GPP). We simulate Fs with the biosphere model BETHY coupled to the fluorescence model SCOPE. The model simulates well the patterns of Fs. Fs is sensitive to leaf chlorophyll and incoming radiation but not to the key physiological parameter Vcmax controlling GPP. Thus further model development is necessary before Fs can be used to constrain GPP
GDGT distributions in the East Siberian Sea: implications for organic carbon export, burial and degradation
Summary: Siberian permafrost contains large amounts of organic carbon that may be released by climate warming. We collected and analysed samples from the East Siberian Sea, using GDGT biomarkers to trace the sourcing and deposition of organic carbon across the shelf. We show that branched GDGTs may be used to trace river erosion. Results from modelling show that organic carbon on the shelf is a complex process involving river-derived and coastal-derived material as well as marine carbon production.
R. B. Sparkes, A. Doğrul Selver, J. Bischoff, H. M. Talbot, Ö. Gustafsson, I. P. Semiletov, O. V. Dudarev, and B. E. van Dongen Biogeosciences Discuss., 12, 637-674, 2015 AbstractDiscussion Paper (PDF, 3761 KB)Supplement (5317 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for BG
12 Jan 2015
Nutrient and mercury deposition and storage in an alpine snowpack of the Sierra Nevada, USA
Summary: Snowpack and precipitation samples were collected along two elevation gradients in the Tahoe Basin during winter and spring from 2011-2014 to evaluate spatial and temporal deposition patterns of nitrogen, phosphorus, and mercury. Study results reflect the highly dynamic nature of snowpack chemical storage, while basin-wide estimates identify snowpack chemical loading from atmospheric deposition as a substantial source of nutrient and pollutant input to the Lake Tahoe watershed each year.
C. Pearson, R. Schumer, B. D. Trustman, K. Rittger, D. W. Johnson, and D. Obrist Biogeosciences Discuss., 12, 593-636, 2015 AbstractDiscussion Paper (PDF, 3459 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
12 Jan 2015
Use of near-infrared spectroscopy to assess phosphorus fractions of different plant availability in forest soils
B. Todt, J. Niederberger, A. Boča, R. Nitschke, M. Kohler, P. Kühn, and J. Bauhus Biogeosciences Discuss., 12, 555-592, 2015 AbstractDiscussion Paper (PDF, 1170 KB)Interactive Discussion (Open, 3 Comments)Manuscript under review for BG
09 Jan 2015
The import and export of organic nitrogen species at a Scottish ombrotrophic peatland
R. M. McKenzie, M. Z. Özel, J. N. Cape, J. Drewer, K. J. Dinsmore, E. Nemitz, J. F. Hamilton, M. A. Sutton, M. W. Gallagher, and U. Skiba Biogeosciences Discuss., 12, 515-554, 2015 AbstractDiscussion Paper (PDF, 1110 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BG
09 Jan 2015
Distributions of glycerol dialkyl glycerol tetraethers in surface soils of Qinghai–Tibetan Plateau: implications of GDGT-based proxies in cold and dry regions
Environmental correlates of peatland carbon fluxes in a thawing landscape: do transitional thaw stages matter?
Summary: We found that the dominant abiotic and biotic correlates of CO2 and CH4 fluxes change in strength and interactions as permafrost thaw progresses in a sub-arctic peatland. Our results emphasize the importance of incorporating transitional stages of thaw in landscape level C budgets and highlight that end-member thaw stages do not adequately describe the variability in structure-function relationships present along a thaw gradient.
Ba, B, and U element partitioning in magnesian calcite skeletons of Octocorallia corals
Summary: The variations of element profiles in biogenic CaCO3 are widely used for identifying differences in biological and physicochemical processes associated with element partitioning. Octocorallia coral skeletons can provide long-term records of environmental conditions in intermediate and deep waters. The change in skeletal Ba/Ca with depth parallels that in the dissolved Ba concentration being linked to ocean nutrient cycling. We did not observe pronounced environmental controls in B/Ca and U/Ca.
Mechanism of O and C isotope fractionation in magnesian calcite skeletons of Octocorallia corals and an implication on their calcification response to ocean acidification
Summary: Skeletal oxygen and carbon isotope fractionation of Octocorallia corals, composed of more soluble calcium carbonate polymorphs of high-Mg calcite, represent a natural laboratory for the study of the response of coral calcification to pH changes. Skeletal isotopic compositions are enriched in light isotopes when conditions are less alkaline, suggsting an even stronger biological manipulation on the sources of dissolved inorganic carbon (DIC) under lower pH.
Responses of energy partitioning and surface resistance to drought in a poplar plantation in northern China
Summary: We found that energy partitioning to latent and sensible heat and surface resistance was dramatically responsive to climatological drought and the dry surface dominated in this poplar plantation regardless of water availability. We concluded that fast-growing and water-intensive species like poplar are poorly adapted for the water limited region, the water demand and reliance on artificial irrigation will only grow as the trees mature, leading to greater water shortages for surrounding areas
M. Kang, Z. Zhang, A. Noormets, X. Fang, T. Zha, J. Zhou, G. Sun, S. McNulty, and J. Chen Biogeosciences Discuss., 12, 345-388, 2015 AbstractDiscussion Paper (PDF, 1428 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BG
07 Jan 2015
A 50% increase in the amount of terrestrial particles delivered by the Mackenzie River into the Beaufort Sea (Canadian Arctic Ocean) over the last 10 years
Summary: 11 years (2003-2013) of satellite data were processed to observe the variations of suspended particulate matter concentrations at the mouth of the Mackenzie River and estimate the fluxes exported into the Canadian Arctic Ocean.
Results show that these concentrations at the river mouth, in the delta zone and river plume have increased by 46%, 71% and 33%, respectively, since 2003. This corresponds to a more than 50% increase in the particulate export from the River into the Beaufort Sea.
Synoptic scale analysis of mechanisms driving surface chlorophyll dynamics in the North Atlantic
Summary: Our main objective was to assess which bottom-up processes can best predict changes in the growth phase of phytoplankton surface blooms in North Atlantic. We used new phenology algorithms to satellite-derived data and compared four different metrics based on physical drivers of phytoplankton. We show that there is a dominant physical mechanism - mixed layer shoaling, and that different regions are governed by different physical phenomena.
High variability of dissolved iron concentrations in the vicinity of Kerguelen Island (Southern Ocean)
Summary: Dissolved Fe (dFe) concentrations were measured in the vicinity of Kerguelen Island. Direct island runoff, glacial melting and resuspended sediments were identified as important inputs of dFe that could potentially fertilize the northern part of the plateau. Overall, heterogeneous sources of Fe over and off the Kerguelen Plateau, in addition to strong variability in Fe supply by vertical or horizontal transport, may explain the high variability in dFe concentrations observed during this study.
F. Quéroué, G. Sarthou, H. F. Planquette, E. Bucciarelli, F. Chever, P. van der Merwe, D. Lannuzel, A. T. Townsend, M. Cheize, S. Blain, F. d'Ovidio, and A. R. Bowie Biogeosciences Discuss., 12, 231-270, 2015 AbstractDiscussion Paper (PDF, 4241 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BGSpecial Issue
06 Jan 2015
Imaging tropical peatlands in Indonesia using ground penetrating radar (GPR) and electrical resistivity imaging (ERI): implications for carbon stock estimates and peat soil characterization
Summary: We use a combination of hydrogeophysical methods and direct cores to better understand peatland thickness in Indonesia and estimate carbon storage in remote peatland systems where available information is limited. Results show that geophysical methods can help improving peat thickness accuracy (when compared to coring), and help identifying certain features within the peat matrix such as organomineral horizons, wood layers, or buttressed trees.
X. Comas, N. Terry, L. Slater, M. Warren, R. Kolka, A. Kristijono, N. Sudiana, D. Nurjaman, and T. Darusman Biogeosciences Discuss., 12, 191-229, 2015 AbstractDiscussion Paper (PDF, 5595 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for BG
06 Jan 2015
Late Pleistocene Glacial–Interglacial related shell size isotope variability in planktonic foraminifera as a function of local hydrology
Summary: The shells of planktonic foraminifera are used to reconstruct past ocean conditions. Researchers select these shells from a narrow size fraction in order to not only remove metabolic effects, but to also compare similar life-stages between samples. We test the differences between the oxygen and carbon stable isotope of different size fractions across an interglacial-glacial transition. Our results suggest that rather than using a single size fraction, researchers should use a dynamic size range.
Phytoplankton dynamics in contrasting early stage North Atlantic spring blooms: composition, succession, and potential drivers
C. J. Daniels, A. J. Poulton, M. Esposito, M. L. Paulsen, R. Bellerby, M. St. John, and A. P. Martin Biogeosciences Discuss., 12, 93-133, 2015 AbstractDiscussion Paper (PDF, 2141 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BG
06 Jan 2015
Assessing vegetation structure and ANPP dynamics in a grassland-shrubland Chihuahuan ecotone using NDVI-rainfall relationships
Summary: Exploration of NDVI-rainfall relationships provided ready biophysically based criteria to study the spatial distribution and dynamics of net primary production (NPP) for herbaceous and shrub vegetation across a Chihuahuan ecotone (Sevilleta NWR, New Mexico). Overall our results suggest that changes in the amount and temporal pattern of precipitation (i.e. reductions in summer precipitation and/or increases in winter rainfall) may intensify the shrub-encroachment process in American SW grasslands
Biological productivity regime and associated N cycling in the vicinity of Kerguelen Island area, Southern Ocean
Summary: Seasonal massive blooms are observed in the vicinity of Kerguelen Plateau. Unexpectedly we report unprecedented rates of nitrification. Such high contribution of nitrification to nitrate assimilation is suggested to be driven by (i) a deep mixed layer, allowing nitrifiers to compete with phytoplankton for the assimilation of ammonium, (ii) extremely high rates of primary production for the Southern Ocean, stimulating the release of dissolved organic matter, and (iii) an efficient food web.
A. J. Cavagna, F. Fripiat, M. Elskens, F. Dehairs, P. Mangion, L. Chirurgien, I. Closset, M. Lasbleiz, L. Flores–Leiva, D. Cardinal, K. Leblanc, C. Fernandez, D. Lefèvre, L. Oriol, S. Blain, and B. Quéguiner Biogeosciences Discuss., 11, 18073-18104, 2014 AbstractDiscussion Paper (PDF, 1640 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for BGSpecial Issue
19 Dec 2014
Iron budgets for three distinct biogeochemical sites around the Kerguelen archipelago (Southern Ocean) during the natural fertilisation experiment KEOPS-2
Summary: Iron biogeochemical budgets during the natural ocean fertilisation experiment KEOPS-2 showed that complex circulation and transport pathways were responsible for differences in the mode and strength of iron supply, with vertical supply dominant on the plateau and lateral supply dominant in the plume. The exchange of iron between dissolved, biogenic and lithogenic pools was highly dynamic, resulting in a decoupling of iron supply and carbon export, and controlling the efficiency of fertilization.
A. R. Bowie, P. van der Merwe, F. Quéroué, T. Trull, M. Fourquez, F. Planchon, G. Sarthou, F. Chever, A. T. Townsend, I. Obernosterer, J.-B. Sallée, and S. Blain Biogeosciences Discuss., 11, 17861-17923, 2014 AbstractDiscussion Paper (PDF, 2366 KB)Supplement (258 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for BGSpecial Issue
19 Dec 2014
Nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance in the diatom Phaeodactylum tricornutum
Daily burned area and carbon emissions from boreal fires in Alaska
Summary: We developed a statistical model of daily carbon consumption by fire for Alaska at 500 m resolution between 2001 and 2012. We used field measurements from black spruce forests in Alaska to build nonlinear multiplicative models predicting carbon consumption by fire in response to environmental variables. Our analysis highlights the importance of accounting for the spatial heterogeneity within fuels and consumption when extrapolating emissions in space and time.
Modeling the global emission, transport and deposition of trace elements associated with mineral dust
Summary: A new technique to determine a size-fractionated global soil elemental emission inventory based on a global soil and a mineralogical datasets is introduced. Spatial variability of mineral dust elemental fractions (8 elements such as Ca,Fe,Al ) is identified on a global scale, particularly for Ca. The ratio of Ca/Al, ranged between 0.1-5.0, and is confirmed as an indicator of dust source regions by global dust model. Total and soluble dust element fluxes into different ocean basins are estimated.
Y. Zhang, N. Mahowald, R. Scanza, E. Journet, K. Desboeufs, S. Albani, J. Kok, G. Zhuang, Y. Chen, D. D. Cohen, A. Paytan, M. D. Patey, E. P. Achterberg, J P. Engelbrecht, and K. W. Fomba Biogeosciences Discuss., 11, 17491-17541, 2014 AbstractDiscussion Paper (PDF, 2092 KB)Supplement (747 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
17 Dec 2014
Eutrophication mitigation in rivers: 30 years of trends and seasonality changes in biogeochemistry of the Loire River (1980–2012)
Summary: Based on large, long term and high quality datasets, this study describes eutrophication mitigation in the Loire river basin since 1980. Reducing phosphate direct inputs since the early 1990s led to a significant decrease of the algal biomass. A powerful seasonality analysis showed that these changes considerably affected the river biogeochemistry at the seasonal scale and questioned the exact role played by denitrification, terrestrial vegetation and fixed aquatic vegetation on the N cycle.
Biogeochemistry of a large and deep tropical lake (Lake Kivu, East Africa): insights from a stable isotope study covering an annual cycle
C. Morana, F. Darchambeau, F. A. E. Roland, A. V. Borges, F. Muvundja, Z. Kelemen, P. Masilya, J.-P. Descy, and S. Bouillon Biogeosciences Discuss., 11, 17227-17254, 2014 AbstractDiscussion Paper (PDF, 692 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for BG
11 Dec 2014
Lunar periodicity in the shell flux of some planktonic foraminifera in the Gulf of Mexico
Nitrogen fixation in the Southern Ocean: a case of study of the Fe-fertilized Kerguelen region (KEOPS II cruise)
Summary: This study shows for first time N2 fixation is occurring in the HNLC area of Southern Ocean and in naturally iron-fertilized waters, at rates exceeding previous reports for high latitudes (up to 20.11 nmol N L-1 d-1). Diazotrophs were identified as heterotrophic bacterioplankton; with an indirect role of dFe in the regulation of this process. Fertilization enhancing regenerated primary production may control N2 fixation via the availability od DOM for heterotrophic bacterioplankton.
Carbon, oxygen and biological productivity in the Southern Ocean in and out the Kerguelen plume: CARIOCA drifter results
Summary: One Carioca buoy deployed during the KEOPS2 expedition in Oct.-Nov. 2011 drifted eastward in the Kerguelen plume. Surface measurements of pCO2 and O2 were collected. Close to the polar front, the surface waters are a sink for CO2 and a source for O2, with mean fluxes equal to -8 mmol CO2 m-2d-1 and +38 mmol O2 m-2d-1. Outside an iron enriched filament, the fluxes are in opposite direction. NCP values from 60 to 140 mmol C m-2d-1and stoichiometric ratios, O2/C, between 1.1 and 1.4 are computed.
Stable isotope paleoclimatology of the earliest Eocene using kimberlite-hosted mummified wood from the Canadian Subarctic
Summary: The recent discovery of mummified wood (non-petrified) within kimberlite diamond mines in Northwest Territories, Canada, has prompted a paleoclimatic investigation of the time in which the trees grew - the earliest Eocene (ca. 53.3 Ma). Multiple proxy records derived from these samples suggest that during greenhouse climates of the Eocene, subarctic Canada was characterized by high temperatures (+16 C above modern), and multidecadal variability in cloudiness and temperature on 20-30 year cycles.
Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore Costa Rica
P. Steeb, S. Krause, P. Linke, C. Hensen, A. W. Dale, M. Nuzzo, and T. Treude Biogeosciences Discuss., 11, 16033-16083, 2014 AbstractDiscussion Paper (PDF, 8105 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for BG
25 Nov 2014
Environmental factors controlling lake diatom communities: a meta-analysis of published data
Summary: I re-analyze information published during the last decades concerning the effect of different environmental predictors on the structure of benthic diatom communities in world lakes, providing a scientific basis for the implementation of new paleoenvironmental inference models. I consider highly relevant the publication of this article in a widely known journal, provided the noticeable demand on paleolimnological meta-studies supporting the use of such biological proxies at a pancontinental scale
Experimental drought induces short-term changes in soil functionality and microbial community structure after fire in a Mediterranean shrubland
Summary: This manuscript reports the results of an experimental field study in which the joint effect of both fire and drought is tested. Drought modifies the short-term post-fire soil functionality and microbial community, in a fire-prone xeric ecosystem in which drought is projected to increase with climate change. This study allows to make a step forward on our integrated understanding of the processes underlying impacts of climate extremes in the recovery of ecosystems after fire.