Spatiotemporal 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 (N) cycling within the Deming Lake watershed at Itasca State Park. With nearly 250 years of data, results suggest a major decline in N availability in red pine beginning in the early 20th century based on detection of significant breakpoints. We believe this synchronous decline is the result of the fire suppression in the state park, though alternative biological and physical mechanisms cannot be ruled out.
Biogeosciences, 12, 3941-3952, doi:10.5194/bg-12-3941-2015, 2015
Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources
Biogeosciences, 12, 3925-3940, doi:10.5194/bg-12-3925-2015, 2015
Coupling δ2H and δ18O biomarker results yields information on relative humidity and isotopic composition of precipitation – a climate transect validation study
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 for (i) calculating the deuterium-excess of leaf water as a proxy for relative humidity and (ii) calculating the plant source water isotopic composition (~precipitation). The approach is validated by the presented climate transect results.
Biogeosciences, 12, 3913-3924, doi:10.5194/bg-12-3913-2015, 2015
Wet-season spatial variability in N2O emissions from a tea field in subtropical central China
Summary: We examined the spatial variability in N2O emissions from a tea field in a wet season using 147 static chambers. The N2O fluxes for a 30min snapshot ranged from -1.73 to 1659.11 g N ha-1 d-1 (average flux of 102.24 g N ha-1 d-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).
Biogeosciences, 12, 3899-3911, doi:10.5194/bg-12-3899-2015, 2015
Growth response of temperate mountain grasslands to inter-annual variations in snow cover duration
Summary: It is shown 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.
Biogeosciences, 12, 3885-3897, doi:10.5194/bg-12-3885-2015, 2015
High variability in dissolved iron concentrations in the vicinity of the Kerguelen Islands (Southern Ocean)
Summary: Dissolved Fe (dFe) concentrations were measured in the vicinity of the Kerguelen Islands. Direct island runoff, glacial melting, and resuspended sediments were identified as important inputs of dFe that could potentially fertilise the northern part of the plateau. Overall, heterogeneous sources of Fe over and off the 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.
Biogeosciences, 12, 3869-3883, doi:10.5194/bg-12-3869-2015, 2015
Effects of CO2-driven ocean acidification on early life stages of marine medaka (Oryzias melastigma)
Biogeosciences, 12, 3861-3868, doi:10.5194/bg-12-3861-2015, 2015
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 to our understanding of carbon cycling and greenhouse gas balances. We are currently 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 labor time, opening new opportunities to advance our knowledge of CO2 across landscapes.
Biogeosciences, 12, 3849-3859, doi:10.5194/bg-12-3849-2015, 2015
Carbon export in the naturally iron-fertilized Kerguelen area of the Southern Ocean based on the 234Th approach
Biogeosciences, 12, 3831-3848, doi:10.5194/bg-12-3831-2015, 2015
The stable isotopic composition of Daphnia ephippia reflects changes in δ13C and δ18O values of food and water
Summary: We show that the stable (C, N, O) isotopic composition of the water flea Daphnia pulicaria is strongly related to that of its 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.
Biogeosciences, 12, 3819-3830, doi:10.5194/bg-12-3819-2015, 2015
Carbon stocks and soil sequestration rates of tropical riverine wetlands
Summary: Riverine wetlands of the south 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 mangroves in the upper than in the lower estuary.
Biogeosciences, 12, 3805-3818, doi:10.5194/bg-12-3805-2015, 2015
The contribution of tephra constituents during biogenic silica determination: implications for soil and palaeoecological studies
Summary: Biogenic silica (BSi) is used as a proxy by soil scientists to identify biological effects on the Si cycle and by palaeoecologists to study environmental changes. We show the presence of tephra constituents can make measurements erroneous at low BSi concentrations, with repercussions for soil and palaeoecological 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.
Biogeosciences, 12, 3789-3804, doi:10.5194/bg-12-3789-2015, 2015
Characterization of particulate organic matter in the Lena River delta and adjacent nearshore zone, NE Siberia – Part I: Radiocarbon inventories
Biogeosciences, 12, 3769-3788, doi:10.5194/bg-12-3769-2015, 2015
GDGT distributions on the East Siberian Arctic Shelf: 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.
Biogeosciences, 12, 3753-3768, doi:10.5194/bg-12-3753-2015, 2015
Seasonal lake surface water temperature trends reflected by heterocyst glycolipid-based molecular thermometers
Biogeosciences, 12, 3741-3751, doi:10.5194/bg-12-3741-2015, 2015
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.
Biogeosciences, 12, 3725-3740, doi:10.5194/bg-12-3725-2015, 2015
Redox regime shifts in microbially mediated biogeochemical cycles
Summary: Despite their global importance, redox reactions mediated by microorganisms 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.
Biogeosciences, 12, 3713-3724, doi:10.5194/bg-12-3713-2015, 2015
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.
Biogeosciences, 12, 3695-3712, doi:10.5194/bg-12-3695-2015, 2015
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. On the other hand, the structure of bacterial community analyzed using PCR-SSCP was shown to be affected by both hydrocarbons and radioactivity.
Biogeosciences, 12, 3681-3693, doi:10.5194/bg-12-3681-2015, 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 to 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.
Biogeosciences, 12, 3665-3680, doi:10.5194/bg-12-3665-2015, 2015
Soil moisture influence on the interannual variation in temperature sensitivity of soil organic carbon mineralization in the Loess Plateau
Biogeosciences, 12, 3655-3664, doi:10.5194/bg-12-3655-2015, 2015
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 phytoplankton surface spring blooms in the North Atlantic. We applied 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.
Biogeosciences, 12, 3641-3653, doi:10.5194/bg-12-3641-2015, 2015
Corrigendum to "Disruption of metal ion homeostasis in soils is associated with nitrogen deposition-induced species loss in an Inner Mongolia steppe" published in Biogeosciences, 12, 3499–3512, 2015
Biogeosciences, 12, 3639-3639, doi:10.5194/bg-12-3639-2015, 2015
Understanding emissions of ammonia from buildings and the 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.
Biogeosciences, 12, 3623-3638, doi:10.5194/bg-12-3623-2015, 2015
Heterotrophic prokaryote distribution along a 2300 km transect in the North Pacific subtropical gyre during a strong La Niña conditions: relationship between distribution and hydrological conditions
Summary: This study focuses on the distribution of three heterotrophic prokaryote groups in relation to the environmental conditions met in the western part of NPSG. Our results showed that the high variability between the various heterotrophic prokaryote cluster abundances depend both on the mesoscale structures and the oligotrophic gradient. To the best of our knowledge, this study is the first report of the heterotrophic prokaryotes distribution under La Niña conditions in the western part of NPSG.
Biogeosciences, 12, 3607-3621, doi:10.5194/bg-12-3607-2015, 2015
Corrigendum to "The Australian Terrestrial Carbon Budget" published in Biogeosciences, 10, 851–869, 2013
Biogeosciences, 12, 3603-3605, doi:10.5194/bg-12-3603-2015, 2015
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 450m 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.
Biogeosciences, 12, 3579-3601, doi:10.5194/bg-12-3579-2015, 2015
Photosynthesis–irradiance responses in the Ross Sea, Antarctica: a meta-analysis
Summary: A compilation of photosynthesis-irradiance measurements from the Ross Sea, Antarctica, was analyzed for spatial and temporal trends, as well as the oceanographic factors that control the responses. The maximum, chlorophyll-specific, irradiance-saturated rate averaged 1.07+/-0.060 ug C per ug Chl per hour. Spring rates were 59% greater than summer rates. Irradiance, CO2, and iron had significant effects on rates. The effects of time need to be incorporated into models of Antarctic production.
Biogeosciences, 12, 3567-3577, doi:10.5194/bg-12-3567-2015, 2015
A 50 % increase in the mass of terrestrial particles delivered by the Mackenzie River into the Beaufort Sea (Canadian Arctic Ocean) over the last 10 years
Summary: Eleven years (2003-2013) of satellite data were processed to observe the variations in 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 in the river plume have increased by 46%, 71% and 33%, respectively, since 2003. This corresponds to a more than 50% increase in particulate export from the river into the Beaufort Sea.
Biogeosciences, 12, 3551-3565, doi:10.5194/bg-12-3551-2015, 2015
Photosynthetic production in the central Arctic Ocean during the record sea-ice minimum in 2012
Summary: Photosynthetic production in the central Arctic Ocean is controlled by light availability below the ice, nitrate and silicate concentrations in the upper ocean, and the role of sub-ice algae that contributed up to 60% to primary production in summer 2012 during the record sea-ice minimum. As sea ice decreases, an overall change in Arctic PP would be foremost related to a change in the role of the ice algal production and nutrient availability.
Biogeosciences, 12, 3525-3549, doi:10.5194/bg-12-3525-2015, 2015
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 -8mmol CO2 m-2d-1 and +38mmol O2 m-2d-1. Outside an iron-enriched filament, the fluxes are in the opposite direction. NCP values of 60-140 mmol C m-2d-1 and stoichiometric ratios, O2/C, between 1.1 and 1.4 are computed.
Biogeosciences, 12, 3513-3524, doi:10.5194/bg-12-3513-2015, 2015
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 involvement of nutrient mobilization in decline in species richness of alkaline grasslands.
Biogeosciences, 12, 3499-3512, doi:10.5194/bg-12-3499-2015, 2015
Technical Note: Silica stable isotopes and silicification in a carnivorous sponge Asbestopluma sp.
Summary: The stable isotope composition of benthic sponge silica skeletons (spicules) has been shown to be a source of useful palaeoceanographic information about past deep seawater chemistry. Here, we investigate the biological vital effects on silica stable isotope composition in a Southern Ocean carnivorous sponge, Asbestopluma sp. We find significant variations in isotopic composition within the specimen – in both silicon and oxygen isotopes – that appear to be related to unusual spicule growth.
Biogeosciences, 12, 3489-3498, doi:10.5194/bg-12-3489-2015, 2015
Observation-based modelling of permafrost carbon fluxes with accounting for deep carbon deposits and thermokarst activity
Summary: We have modelled the carbon release from thawing permafrost soils under various scenarios of future warming. Our results suggests that up to about 140Pg of carbon could be released under strong warming by end of the century. We have shown that abrupt thaw processes under thermokarst lakes can unlock large amounts of perennially frozen carbon stored in deep deposits (which extend many metres into the soil).
Biogeosciences, 12, 3469-3488, doi:10.5194/bg-12-3469-2015, 2015
Modeling photosynthesis of discontinuous plant canopies by linking the 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 the 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.
Biogeosciences, 12, 3447-3467, doi:10.5194/bg-12-3447-2015, 2015
Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific
Biogeosciences, 12, 3429-3446, doi:10.5194/bg-12-3429-2015, 2015
Use of near-infrared spectroscopy to assess phosphorus fractions of different plant availability in forest soils
Summary: The analysis of soil phosphorus (P) in fractions of different plant availability is a common approach to characterize the P status of forest soils. However, quantification of organic and inorganic P fractions is very labour intensive and therefore rarely applied for large sample numbers. Prediction of P fractions with NIRS can be a promising approach to replace conventional analysis, if models are developed for sets of soil samples with similar physical and chemical properties.
Biogeosciences, 12, 3415-3428, doi:10.5194/bg-12-3415-2015, 2015
Differences in microbial community composition between injection and production water samples of water flooding petroleum reservoirs
Summary: Microbial communities in injected water are expected to have a significant influence on those of reservoir strata in long-term water-flooding petroleum reservoirs. We thereby investigated the similarities and differences in microbial communities in water samples collected from the wellhead and downhole of injection wells, and from production wells in a homogeneous reservoir and a heterogeneous reservoir using high-throughput sequencing.
Biogeosciences, 12, 3403-3414, doi:10.5194/bg-12-3403-2015, 2015
Modelling the impact of riverine DON removal by marine bacterioplankton on primary production in the Arctic Ocean
Biogeosciences, 12, 3385-3402, doi:10.5194/bg-12-3385-2015, 2015
Remote sensing the sea surface CO2 of the Baltic Sea using the SOMLO methodology
Summary: In this paper, we used combines two existing methods (i.e. self-organizing maps and multiple linear regression) to estimate the ocean surface partial pressure of CO2 in the Baltic Sea from the remotely sensed sea surface temperature, chlorophyll, coloured dissolved organic matter, net primary production, and mixed-layer depth. The outputs of this research have a horizontal resolution of 4km and cover the 1998–2011 period. These outputs give a monthly map of the Baltic Sea.
Biogeosciences, 12, 3369-3384, doi:10.5194/bg-12-3369-2015, 2015
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 subfossil specimens may be used 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.
Biogeosciences, 12, 3351-3368, doi:10.5194/bg-12-3351-2015, 2015
WETCHIMP-WSL: intercomparison of wetland methane emissions models over West Siberia
Summary: We evaluated 21 forward models and 5 inversions over western Siberia in terms of CH4 emissions and simulated wetland areas and compared these results to an intensive in situ CH4 flux data set, 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.
Biogeosciences, 12, 3321-3349, doi:10.5194/bg-12-3321-2015, 2015
Emergence of multiple ocean ecosystem drivers in a large ensemble suite with an Earth system model
Summary: A large initial-condition ensemble suite of simulations with an Earth system model is applied to evaluate emergence characteristics of four ocean ecosystem drivers under climate change. The drivers considered are warming, acidification, deoxygenation, and perturbations to biological productivity. The spatial and temporal hierarchies of the emergence of these drivers are considered, using concepts of both time of emergence (ToE) and confidence intervals.
Biogeosciences, 12, 3301-3320, doi:10.5194/bg-12-3301-2015, 2015
Technical Note: A simple method for vaterite precipitation for isotopic studies: implications for bulk and clumped isotope analysis
Summary: •Vaterite was synthesized from a NaCl-saturated CaCO3 solution at 23-91°C •Vaterite occurred as pure or dominating phase and amounted up to 235 mg per experiment •The precipitation technique allows thermal and isotopic equilibration and enables oxygen and clumped isotope analyses •18α(vaterite-H2O) has the same temperature dependence as calcite •Vaterite δ18O values can hardly be distinguished from calcite (offset +0.0±0.4‰) •Clumped isotope values are indistinguishable from calibration data
Biogeosciences, 12, 3289-3299, doi:10.5194/bg-12-3289-2015, 2015
The shape of the oceanic nitracline
Biogeosciences, 12, 3273-3287, doi:10.5194/bg-12-3273-2015, 2015
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 interannual variation of simulated 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, and to the quantity of livestock, which drive the N pool and N turnover in the soil, using a coupled vegetation–litter decomposition–emission model.
Biogeosciences, 12, 3253-3272, doi:10.5194/bg-12-3253-2015, 2015
Positive trends in organic carbon storage in Swedish agricultural soils due to unexpected socio-economic drivers
Summary: Soil carbon dynamics of the past 2 decades in Swedish agricultural soils were assessed using three consecutive soil inventories. We found a significant increase in country-wide soil carbon concentrations, which is in contrast to trends reported in neighbouring countries. We explained this by a significant rise of the proportion of leys in Swedish agriculture, which was found to be strongly related to the increase in horse population. Human lifestyle can affect soil carbon.
Biogeosciences, 12, 3241-3251, doi:10.5194/bg-12-3241-2015, 2015
Ideas and perspectives: on the emission of amines from terrestrial vegetation in the context of new atmospheric particle formation
Biogeosciences, 12, 3225-3240, doi:10.5194/bg-12-3225-2015, 2015
Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska
Summary: This study of methane (CH4) and carbon dioxide (CO2) emission modes from 40 lakes along a latitudinal transect in Alaska revealed that thermokarst lakes formed in Pleistocene-aged icy, organic-rich yedoma-type permafrost had the highest emissions. Ebullition and diffusion were the dominant modes of CH4 and CO2 emissions, respectively. Accounting for the global warming potentials of the gases, the climate warming impact of lake CH4 emissions was 2 times higher than that of CO2.
Biogeosciences, 12, 3197-3223, doi:10.5194/bg-12-3197-2015, 2015
Export fluxes in a naturally iron-fertilized area of the Southern Ocean – Part 2: Importance of diatom resting spores and faecal pellets for export
Biogeosciences, 12, 3171-3195, doi:10.5194/bg-12-3171-2015, 2015