Flux variations and vertical distributions of siliceous Rhizaria (Radiolaria and Phaeodaria) in the western Arctic Ocean: indices of environmental changes
Biogeosciences, 12, 2019-2046, doi:10.5194/bg-12-2019-2015, 2015
The combined effects of nitrification inhibitor and biochar incorporation on yield-scaled N2O emissions from an intensively managed vegetable field in southeastern China
Summary: New nitrification inhibitor CP (chlorinated pyridine) application caused a significant decrease in yield-scaled N2O emissions in an intensively managed vegetable field, while biochar amendment had no significant influence on cumulative N2O emissions but significantly decreased soil pH and yield-scaled N2O emissions. Overall, taking environmental and economic benefits into consideration, CP application in the vegetable field was the best procedure for reducing the yield-scaled N2O emissions.
Biogeosciences, 12, 2003-2017, doi:10.5194/bg-12-2003-2015, 2015
Biostratigraphic evidence for dramatic Holocene uplift of Robinson Crusoe Island, Juan Fernández Ridge, SE Pacific Ocean
Biogeosciences, 12, 1993-2001, doi:10.5194/bg-12-1993-2015, 2015
Fe and C co-limitation of heterotrophic bacteria in the naturally fertilized region off the Kerguelen Islands
Biogeosciences, 12, 1983-1992, doi:10.5194/bg-12-1983-2015, 2015
Marine sources of bromoform in the global open ocean – global patterns and emissions
Biogeosciences, 12, 1967-1981, doi:10.5194/bg-12-1967-2015, 2015
The contribution of zooplankton faecal pellets to deep-carbon transport in the Scotia Sea (Southern Ocean)
Summary: In the Scotia Sea, the zooplankton community shifting from a herbivorous to omnivorous diet strongly influences the chance of faecal pellets to reach the bottom. Faecal pellet flux was mainly a product of the vertically migrating and deeper-dwelling zooplankton in the iron-fertilized and iron-limited region respectively. The results demonstrate that the behaviour of the zooplankton community plays a critical role in controlling the quantity and quality of carbon exported in this area.
Biogeosciences, 12, 1955-1965, doi:10.5194/bg-12-1955-2015, 2015
Riparian and in-stream controls on nutrient concentrations and fluxes in a headwater forested stream
Summary: Terrestrial inputs are considered the major driver of longitudinal patterns of nutrient concentration. Yet we show that longitudinal trends result from hydrological mixing with terrestrial inputs and in-stream processes. We challenge the idea that nutrient concentrations decrease downstream when in-stream net uptake is high. Conversely, in-stream processes can strongly affect stream nutrient chemistry and fluxes even in the absence of consistent longitudinal trends in nutrient concentration.
Biogeosciences, 12, 1941-1954, doi:10.5194/bg-12-1941-2015, 2015
Dissolved greenhouse gases (nitrous oxide and methane) associated with the naturally iron-fertilized Kerguelen region (KEOPS 2 cruise) in the Southern Ocean
Biogeosciences, 12, 1925-1940, doi:10.5194/bg-12-1925-2015, 2015
Poor correlation between phytoplankton community growth rates and nutrient concentration in the sea
Summary: We question here is whether phytoplankton community growth rates respond to nutrient concentration in a similar manner to phytoplankton species composing the community, that is, following Monod's model. In situ marine community growth rates in relation to nutrient concentration and the behaviour of a simple multi-species community model show that community growth rate does not follow Monod's model. We observed here that this can be explained as a consequence of change in size structure.
Biogeosciences, 12, 1915-1923, doi:10.5194/bg-12-1915-2015, 2015
Technical Note: Methionine, a precursor of methane in living plants
Summary: Plants are known as a source of methane (CH4), but the biochemical mechanisms involved in CH4 formation are still unknown. Employing 13C-labelled methionine clearly identified the sulfur-bound methyl group of methionine as a carbon precursor of CH4 released from lavender plants. When relating CH4 emission rates to dark respiration of intact plants, we found a molar CH4:CO2 emission ratio of 2.0 ±1.1 (pmol:µmol). After physical stress CH4 release rates greatly increased.
Biogeosciences, 12, 1907-1914, doi:10.5194/bg-12-1907-2015, 2015
Microbial iron uptake in the naturally fertilized waters in the vicinity of the Kerguelen Islands: phytoplankton–bacteria interactions
Summary: In this manuscript, we present the results of iron uptake measured in the naturally iron-fertilized area during the Kerguelen Ocean and Plateau compared Study 2 cruise (KEOPS2). Iron uptake by bulk community and several size fractions (microplankton, pico-nanoplankton and bacteria) are presented, compared and discussed in the present paper. This work also presents first investigations on the potential competition between bacteria and phytoplankton for access to iron.
Biogeosciences, 12, 1893-1906, doi:10.5194/bg-12-1893-2015, 2015
Carbon dioxide transport across the hillslope–riparian–stream continuum in a boreal headwater catchment
Summary: Carbon dioxide transport between the terrestrial and aquatic systems was dominated by export from the near-stream riparian zone. Over the year, riparian export was highest during autumn storms and the spring snowmelt event. This resulted in high downstream export during these periods with vertical evasion from the stream surface accounting for 60% of the total stream water export, highlighting the importance of evasion to carbon export via the aquatic conduit.
Biogeosciences, 12, 1881-1892, doi:10.5194/bg-12-1881-2015, 2015
Multi-isotope labelling of organic matter by diffusion of 2H/18O-H2O vapour and 13C-CO2 into the leaves and its distribution within the plant
Summary: We present a new technique to label organic matter (OM) at its place of formation by the application of 13C, 18O and 2H through the gaseous phase. The label diffused into leaves was incorporated into assimilates and was detected in plant tissues. This technique can be applied in soil sciences, e.g. to trace the decomposition pathways of soil OM inputs, or in plant physiology and palaeoclimatic reconstruction, e.g. to further investigate the origin of the 18O and 2H signal in tree ring cellulose.
Biogeosciences, 12, 1865-1879, doi:10.5194/bg-12-1865-2015, 2015
Pyrogenic carbon from tropical savanna burning: production and stable isotope composition
Summary: Around half of all pyrogenic carbon (charcoal+soot) derived from wildfires comes from semi-annual burning of tropical savannas. This pyrogenic carbon is significant because it is a component of global aerosols capable of modulating the greenhouse effect and is resistant to degradation. We use controlled field burns in northern Australian savannas to determine how much pyrogenic carbon is formed, how much of this is recalcitrant and how it is partitioned between ground residues and airborne soot.
Biogeosciences, 12, 1849-1863, doi:10.5194/bg-12-1849-2015, 2015
Forests, savannas, and grasslands: bridging the knowledge gap between ecology and Dynamic Global Vegetation Models
Biogeosciences, 12, 1833-1848, doi:10.5194/bg-12-1833-2015, 2015
A probabilistic risk assessment for the vulnerability of the European carbon cycle to weather extremes: the ecosystem perspective
Summary: Extreme weather events can but do not have to cause extreme ecosystem response. Here, we focus on hazardous ecosystem behaviour and identify coinciding weather conditions. We use a simple probabilistic risk assessment and apply it to terrestrial ecosystems, defining a hazard as negative net biome productivity. In Europe, ecosystems are vulnerable to drought in the Mediterranean and temperate region, whereas vulnerability in Scandinavia is not caused by water shortages.
Biogeosciences, 12, 1813-1831, doi:10.5194/bg-12-1813-2015, 2015
Drivers of long-term variability in CO2 net ecosystem exchange in a temperate peatland
Summary: The CO2 sink strength of a temperate peatland in SE Scotland exhibited large inter-annual variability which was well-correlated to the length of the growing season. Mean winter air temperature explained 87% of the inter-annual variability in the sink strength of the following summer, indicating a phenological memory effect. Autotrophic respiration is thought to be dominant, but heterotrophic processes might have been enhanced during dry spells increasing the loss of CO2 to the atmosphere.
Biogeosciences, 12, 1799-1811, doi:10.5194/bg-12-1799-2015, 2015
The trophic and metabolic pathways of foraminifera in the Arabian Sea: evidence from cellular stable isotopes
Biogeosciences, 12, 1781-1797, doi:10.5194/bg-12-1781-2015, 2015
Organic N and P in eutrophic fjord sediments – rates of mineralization and consequences for internal nutrient loading
Biogeosciences, 12, 1765-1779, doi:10.5194/bg-12-1765-2015, 2015
Boron incorporation in the foraminifer Amphistegina lessonii under a decoupled carbonate chemistry
Summary: Culture experiments based on a decoupled pH and CO32- chemistry indicate that the δ11B of the test of A. lessonii is related to pH whereas the B/Ca of the foraminiferal shells show a positive correlation with B(OH)4-/HCO3-. The latter observation suggests a competition between B(OH)4- and HCO3- of the culture media for B uptake into the test.
Biogeosciences, 12, 1753-1763, doi:10.5194/bg-12-1753-2015, 2015
Oxygen and carbon isotope composition of modern planktic foraminifera and near-surface waters in the Fram Strait (Arctic Ocean) – a case study
Summary: Fossil planktic foraminifera and their geochemical composition are commonly used proxies in palaeoceanography. Our study with living specimens revealed that in the Fram Strait both Neogloboquadrina pachyderma and Turborotalita quinqueloba from the water column have lower δ18O and δ13C values than inorganically precipitated calcite/fossil tests from the sediment surface. These offsets indicate biological influence during calcification and a change of water column properties in the recent past.
Biogeosciences, 12, 1733-1752, doi:10.5194/bg-12-1733-2015, 2015
Early spring mesopelagic carbon remineralization and transfer efficiency in the naturally iron-fertilized Kerguelen area
Biogeosciences, 12, 1713-1731, doi:10.5194/bg-12-1713-2015, 2015
A halocarbon survey from a seagrass dominated subtropical lagoon, Ria Formosa (Portugal): flux pattern and isotopic composition
Biogeosciences, 12, 1697-1711, doi:10.5194/bg-12-1697-2015, 2015
Tidal controls on trace gas dynamics in a seagrass meadow of the Ria Formosa lagoon (southern Portugal)
Biogeosciences, 12, 1683-1696, doi:10.5194/bg-12-1683-2015, 2015
Reviews and Syntheses: Responses of coccolithophores to ocean acidification: a meta-analysis
Biogeosciences, 12, 1671-1682, doi:10.5194/bg-12-1671-2015, 2015
Disparities between in situ and optically derived carbon biomass and growth rates of the prymnesiophyte Phaeocystis globosa
Biogeosciences, 12, 1659-1670, doi:10.5194/bg-12-1659-2015, 2015
Spatiotemporal variability of alkalinity in the Mediterranean Sea
Biogeosciences, 12, 1647-1658, doi:10.5194/bg-12-1647-2015, 2015
Soil organic carbon in the Sanjiang Plain of China: storage, distribution and controlling factors
Summary: The Sanjiang Plain of China, an important grain production base, is typical of ecosystems. In this study, 419 soil samples and a geostatistical method were used to estimate total SOC storage and to determine its pattern-controlling factors. The results from this study provide the most up-to-date knowledge on the storage and pattern of SOC in this plain, and the analysis conducted here could contribute to the determination of ecosystem carbon budgets and our understanding of ecosystem services.
Biogeosciences, 12, 1635-1645, doi:10.5194/bg-12-1635-2015, 2015
Technical Note: Multispectral lidar time series of pine canopy chlorophyll content
Summary: A hyperspectral lidar produces point clouds with multiple spectral channels (colours) for each point. We measured a pine and used the spectral content to estimate chlorophyll content. We validated these results using chemical laboratory analysis of needles taken from the pine. Our prototype has limitations, but still shows the great potential of coloured point clouds. Potential applications include forestry, security, archaeology and city modelling.
Biogeosciences, 12, 1629-1634, doi:10.5194/bg-12-1629-2015, 2015
Continuous and discontinuous variation in ecosystem carbon stocks with elevation across a treeline ecotone
Summary: Here we investigate how ecosystem carbon stocks vary with elevation shifting from the closed forest to open alpine tundra, in the mountains of southern Norway. Above-ground carbon stocks decreased with elevation, with a clear breakpoint at the forest line, while the organic horizon soil carbon stocks increased linearly with elevation. Overall, ecosystem carbon stocks increased with elevation above the treeline and decreased with elevation below, demonstrating the importance of the treeline.
Biogeosciences, 12, 1615-1627, doi:10.5194/bg-12-1615-2015, 2015
Amelioration of marine environments at the Smithian–Spathian boundary, Early Triassic
Summary: The Smithian--Spathian boundary was a key event in the recovery of marine environments and ecosystems following the end-Permian mass extinction ~1.5 million years earlier. Our analysis of the Shitouzhai section in South China reveals major changes in oceanographic conditions at the SSB intensification of oceanic circulation leading to enhanced upwelling of nutrient- and sulfide-rich deep waters and coinciding with an abrupt cooling that terminated the Early Triassic hothouse climate.
Biogeosciences, 12, 1597-1613, doi:10.5194/bg-12-1597-2015, 2015
Spatial variability and hotspots of soil N2O fluxes from intensively grazed grassland
Summary: The spatial variability of N2O fluxes measured at the field scale were investigated using a high-precision closed loop dynamic chamber. The results highlight the large and often unpredictable variation in N2O flux magnitude measured from agricultural soils at a relatively small scale. Available nitrogen content of the soils accounts for some of the variability in N2O emissions. The study suggests animal waste is an important source of N2O emissions released from livestock farms.
Biogeosciences, 12, 1585-1596, doi:10.5194/bg-12-1585-2015, 2015
Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin
Summary: This study looks at the combined impacts of hypoxia and acidification, two major environmental stressors affecting coastal systems, in a seasonally stratified basin. Here, the surface water experiences less seasonality in pH than the bottom water despite higher process rates. This is due to a substantial reduction in the acid-base buffering capacity of the bottom water as it turns hypoxic in summer. This highlights the crucial role of the buffering capacity as a modulating factor in pH dynamics.
Biogeosciences, 12, 1561-1583, doi:10.5194/bg-12-1561-2015, 2015
Organic carbon production, mineralisation and preservation on the Peruvian margin
Biogeosciences, 12, 1537-1559, doi:10.5194/bg-12-1537-2015, 2015
A 22 570-year record of vegetational and climatic change from Wenhai Lake in the Hengduan Mountains biodiversity hotspot, Yunnan, Southwest China
Biogeosciences, 12, 1525-1535, doi:10.5194/bg-12-1525-2015, 2015
Thermal-based modeling of coupled carbon, water, and energy fluxes using nominal light use efficiencies constrained by leaf chlorophyll observations
Biogeosciences, 12, 1511-1523, doi:10.5194/bg-12-1511-2015, 2015
Comparison of ten packages that compute ocean carbonate chemistry
Summary: Basic marine carbonate system variables such as pH are often computed from others. Such calculations are made with many public software packages, but their results have never been compared. A new study compares 10 of these packages, quantifying differences, isolating causes, and making recommendations to reduce future discrepancies. This comparison effort has led to more than a 10-fold reduction in differences between packages for some computed variables.
Biogeosciences, 12, 1483-1510, doi:10.5194/bg-12-1483-2015, 2015
Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions
Summary: We investigated the nitrate N, O isotopic composition for the Southern Ocean Kerguelen Plateau area, aiming at understanding the N-cycling in this naturally iron fertilized area characterized by large recurrent phytoplankton blooms. The system is characterized by moderate consumption of nitrate over the season while silicic acid, on the contrary, becomes depleted, suggesting significant recycling of N. Mixed layer nitrate isotopic signatures corroborate this.
Biogeosciences, 12, 1459-1482, doi:10.5194/bg-12-1459-2015, 2015
Seasonal response of air–water CO2 exchange along the land–ocean aquatic continuum of the northeast North American coast.
Summary: This study quantifies the exchange of carbon dioxide (CO2) between the atmosphere and the land-ocean aquatic continuum (LOAC) of the northeast North American coast, which consists of rivers, estuaries, and the coastal ocean. Our analysis reveals significant variations of the flux intensity both in time and space across the study area. Ice cover, snowmelt, and the intensity of the estuarine filter are identified as important control factors of the CO2 exchange along the LOAC.
Biogeosciences, 12, 1447-1458, doi:10.5194/bg-12-1447-2015, 2015
Seasonal survey of the composition and degradation state of particulate organic matter in the Rhône River using lipid tracers
Biogeosciences, 12, 1431-1446, doi:10.5194/bg-12-1431-2015, 2015
Use of Ra isotopes to deduce rapid transfer of sediment-derived inputs off Kerguelen
Summary: We investigated the origin and mechanisms of the natural iron fertilization that sustains a phytoplankton bloom downstream of the Kerguelen Islands. We used radium isotopes to trace the fate of shelf waters that may transport iron and other micronutrients towards offshore waters. We show that shelf waters are rapidly transferred offshore and may be transported across the polar front (PF). The PF may thus not be a strong physical barrier for chemical elements released by the shelf sediments.
Biogeosciences, 12, 1415-1430, doi:10.5194/bg-12-1415-2015, 2015
Increase in soil organic carbon by agricultural intensification in northern China
Summary: Agricultural intensification has contributed to sustained Chinese food supply since 1980s and also influenced soil organic carbon (SOC) stock. The study, conducted in Huantai county - a typical intensive farming region in northern China, found that from 1982 to 2011, farmland SOC stock (0-20cm) of the entire county increased by 59% which can be well explained by the increasing crop residues input. More technologies must be developed for enhancement of SOC and reduction of non-CO2 GHG emissions.
Biogeosciences, 12, 1403-1413, doi:10.5194/bg-12-1403-2015, 2015
Rapid acidification of mode and intermediate waters in the southwestern Atlantic Ocean
Summary: The increase in anthropogenic atmospheric carbon dioxide is mitigated by uptake by the world ocean, which alters the pH of the water. In the South Atlantic we find the highest rates of acidification relative to increase in anthropogenic carbon (Cant) found in Subantarctic Mode Water and Antarctic Intermediate Water. The moderate rates of increase in Cant combined with low buffering capacities, due to low salinity and alkalinity values, have caused rapid acidification in the Subantarctic Zone.
Biogeosciences, 12, 1387-1401, doi:10.5194/bg-12-1387-2015, 2015
Diatom flux reflects water-mass conditions on the southern Northwind Abyssal Plain, Arctic Ocean
Biogeosciences, 12, 1373-1385, doi:10.5194/bg-12-1373-2015, 2015
Soil redistribution and weathering controlling the fate of geochemical and physical carbon stabilization mechanisms in soils of an eroding landscape
Summary: We link the mineralogy of soils affected by erosion and deposition to the distribution of soil carbon fractions, their turnover and microbial activity. We show that the weathering status of soils and their history are controlling the stabilization of carbon with minerals. After burial, aggregated C is preserved more efficiently while non-aggregated C can be released and younger C re-sequestered more easily. Weathering changes the effectiveness of stabilization mechanism limiting this C sink.
Biogeosciences, 12, 1357-1371, doi:10.5194/bg-12-1357-2015, 2015
Evaluation of coral reef carbonate production models at a global scale
Summary: Production of calcium carbonate by coral reefs is important in the global carbon cycle. Using a global framework we evaluate four models of reef calcification against observed values. The temperature-only model showed significant skill in reproducing coral calcification rates. The absence of any predictive power for whole reef systems highlights the importance of coral cover and the need for an ecosystem modelling approach accounting for population dynamics in terms of mortality and recruitment.
Biogeosciences, 12, 1339-1356, doi:10.5194/bg-12-1339-2015, 2015
Climate and land use change impacts on global terrestrial ecosystems and river flows in the HadGEM2-ES Earth system model using the representative concentration pathways
Biogeosciences, 12, 1317-1338, doi:10.5194/bg-12-1317-2015, 2015
Constraining ecosystem carbon dynamics in a data-limited world: integrating ecological "common sense" in a model–data fusion framework
Biogeosciences, 12, 1299-1315, doi:10.5194/bg-12-1299-2015, 2015
Trends and drivers in global surface ocean pH over the past 3 decades
Summary: This paper utilizes the SOCATv2 data product to calculate surface ocean pH. The pH data are divided into 17 biomes, and a linear regression is used to derive the long-term trend of pH in each biome. The results are consistent with the trends observed at time series stations. The uncertainties are too large for a mechanistic understanding of the driving forces behind the trend, but there are indications that concurrent changes in chemistry create spatial variability.
Biogeosciences, 12, 1285-1298, doi:10.5194/bg-12-1285-2015, 2015
Size-fractionated dissolved primary production and carbohydrate composition of the coccolithophore Emiliania huxleyi
Biogeosciences, 12, 1271-1284, doi:10.5194/bg-12-1271-2015, 2015