Variations of leaf N, P concentrations in shrubland biomes across northern China: phylogeny, climate and soil
Summary: Leaf chemical concentrations are key traits in ecosystem functioning. Previous studies have biased for trees and grasses. Here, we explored the patterns of leaf N and P concentrations in relation to climate, soil and evolutionary history in Northern China. We found that climate influenced the community chemical traits through the shift in species composition, whereas soil directly influenced the community chemical traits.
Biogeosciences Discuss., 12, 18973-18998, doi:10.5194/bgd-12-18973-2015, 2015
N2 fixation in eddies of the eastern tropical South Pacific Ocean
Summary: The ocean is full of eddies and they play a key role for ocean biogeochemistry. In order to understand dinitrogen (N2) fixation, one major control of oceanic primary production, we investigated 3 eddies in the eastern tropical South Pacific off Peru. We conducted the first detailed survey and found increased N2 fixation in the oxygen depleted cores of anticyclonic mode water eddies. Taken together, we could -for the first time- show that eddies play an important role for N2 fixation off Peru.
Biogeosciences Discuss., 12, 18945-18972, doi:10.5194/bgd-12-18945-2015, 2015
Key biogeochemical factors affecting soil carbon storage in Posidonia meadows
Summary: The recent focus on carbon (C) trading has intensified interest in ‘Blue Carbon’– C sequestered by coastal vegetation. However, the factors influencing C storage are poorly understood. The patterns found in this study support that C storage in Posidonia seagrass soils is influenced by interactions of biological, chemical and physical factors within the meadow. We conclude that there is a need to improve global estimates accounting for biogeochemical factors driving variability within habitats
Biogeosciences Discuss., 12, 18913-18944, doi:10.5194/bgd-12-18913-2015, 2015
Net global warming potential and greenhouse gas intensity in rice agriculture driven by high yields and nitrogen use efficiency: a 5 year field study
Summary: We asked American Journal Expert for help in re-editing our revised manuscript once again. We try to improve the overall readability. Of course, we have revised the whole manuscript incorporating all the comments raised by the two reviewers. Please see the following point-by-point answers as well as the tracking pdf files. Please notice that the attached revised manuscript with tracking system did not show the revisision we made before we send to the language office. Thank you once again!
Biogeosciences Discuss., 12, 18883-18911, doi:10.5194/bgd-12-18883-2015, 2015
Changing seasonality of the Baltic Sea
Summary: Using satellite-derived datasets we have found drastic changes in the timing of the annual cycle in physical and ecological variables of the Baltic Sea over the last 30 years. The summer season starts earlier and extends longer. The period with sea-surface temperature of at least 17 ˚C has doubled; the period with high water turbidity has quadrupled. While both the phytoplankton spring and summer blooms have become earlier, the annual maximum has switched to the summer cyanobacteria bloom.
Biogeosciences Discuss., 12, 18855-18882, doi:10.5194/bgd-12-18855-2015, 2015
Blooms of cyanobacteria in a temperate Australian lagoon system post and prior to European settlement
Summary: The Gippsland Lakes Australia, have suffered from periodic blooms of cyanobacteria (blue green algae) since the mid 1980s. Prior to this, little is known about the history of cyanobacterial blooms in this system. We investigated the history of cyanobacterial blooms using a sediment core taken from the Gippsland Lakes which had each layer dated using lead isotopes. The results showed, surprising blooms of cyanobacteria were also prevalent prior ro european settlement
Biogeosciences Discuss., 12, 18829-18853, doi:10.5194/bgd-12-18829-2015, 2015
Sex-associated variations in coral skeletal oxygen and carbon isotopic composition of Porites panamensis in the southern Gulf of California
Summary: Coral growth rate is known to influence the δ18O and δ13C isotope record to a lesser extent. Recent published data show differences in growth parameters between female and male coral; thus, skeletal δ18O and δ13C are hypothesized to be different in each sex. Our results support the hypothesis of a sex-associated difference in skeletal δ18O and δ13C signal, and suggest that environmental conditions and coral growth parameters affect skeletal isotopic signal differently in each sex.
Biogeosciences Discuss., 12, 18795-18827, doi:10.5194/bgd-12-18795-2015, 2015
The interaction between nitrogen and phosphorous is a strong predictor of intra-plant variation in nitrogen isotope composition in a desert species
Biogeosciences Discuss., 12, 18769-18794, doi:10.5194/bgd-12-18769-2015, 2015
Methods comparison to retrieve the refractive index of small scatterers
Summary: In this paper, several methods for the retrieval of the refractive indices are used in three different examples modelling different shapes and particle size distributions. The error associated with each method is discussed and analysed. It is finally demonstrated that those inverse methods using a genetic algorithm provide optimal estimations relative to other techniques that, although faster, are less accurate.
Biogeosciences Discuss., 12, 18723-18768, doi:10.5194/bgd-12-18723-2015, 2015
Technical Note: Sampling and processing of mesocosm sediment trap material for quantitative biogeochemical analysis
Biogeosciences Discuss., 12, 18693-18722, doi:10.5194/bgd-12-18693-2015, 2015
Distribution of Arctic and Pacific copepods and their habitat in the northern Bering Sea and Chukchi Sea
Biogeosciences Discuss., 12, 18661-18691, doi:10.5194/bgd-12-18661-2015, 2015
Increasing coccolithophore abundance in the subtropical North Atlantic from 1990 to 2014
Summary: In this study, we combine phytoplankton pigment data along with particulate inorganic carbon and chlorophyll measurements from the satellite record to assess recent trends in phytoplankton dynamics in the North Atlantic subtropical gyre, with a focus on coccolithophores. We show that coccolithophores in the North Atlantic are increasing in abundance. Correlations suggest that they have been responding positively to increasing inorganic carbon from anthropogenic inputs in the upper mixed layer.
Biogeosciences Discuss., 12, 18625-18660, doi:10.5194/bgd-12-18625-2015, 2015
Reconstructions of biomass burning from sediment charcoal records to improve data-model comparisons
Summary: Understanding why and how fire locations, sizes, and frequencies are shifting in many parts of the world requires data about the history of fire. Here we use 736 paleofire records from sediments around the world to understand changes in fire history, the controls on those changes, and to validate fire models. Trends and maps of the paleofire data show that biomass burning has increased rapidly in recent decades, following many decades of very low fire activity.
Biogeosciences Discuss., 12, 18571-18623, doi:10.5194/bgd-12-18571-2015, 2015
Ocean acidification challenges copepod reproductive plasticity
Summary: Ocean acidification is challenging phenotypic plasticity of individuals and populations. We studied phenotypic plasticity of the calanoid copepod Acartia bifilosa in the course of a pelagic, large-volume mesocosm study in the Baltic Sea. We found significant negative effects of ocean acidification on adult female copepod size and egg hatching success. Overall, these results indicate that A. bifilosa could be affected by projected near future CO2 levels.
Biogeosciences Discuss., 12, 18541-18570, doi:10.5194/bgd-12-18541-2015, 2015
Organic carbon burial efficiency in a large tropical hydroelectric reservoir
Summary: Hydroelectric reservoirs in the tropics emit greenhouse gases, but also bury carbon in their sediments. We investigated the efficiency of organic carbon (OC) burial in a large tropical reservoir, using spatially resolved measurements of sediment accumulation, and found that more than half (~57%) of the OC deposited onto the sediment is buried. This high efficiency in OC burial indicates that tropical reservoirs may bury OC more efficiently than natural lakes.
Biogeosciences Discuss., 12, 18513-18540, doi:10.5194/bgd-12-18513-2015, 2015
Simulating oxygen isotope ratios in tree ring cellulose using a dynamic global vegetation model
Summary: Records of stable oxygen isotope ratios in tree rings are valuable tools to reconstruct past climatic conditions. So far, they have not been made use of in global dynamic vegetation models. Here we present a model that simulates oxygen isotope ratios in tree rings. Our results compare well with measurements performed in European forests. The model is useful to study oxygen isotope patterns of tree-ring cellulose across large spatial and temporal scales.
Biogeosciences Discuss., 12, 18463-18512, doi:10.5194/bgd-12-18463-2015, 2015
Concentrations and ratios of Sr, Ba and Ca along an estuarine river to the Gulf of Mexico – implication for sea level rise effects on trace metal distribution
Summary: The study found that salinity strongly affects spatiotemporal distributions of Sr and Ca concentrations and their ratios, but has no effect on Ba concentration, which appears mainly geochemically controlled. These results indicate that concentrations of Sr and Ca in the world’s estuaries will very likely increase in the future as sea level rise continues, which could affect aquatic environments and biological communities.
Biogeosciences Discuss., 12, 18425-18461, doi:10.5194/bgd-12-18425-2015, 2015
Impact of climate extremes on wildlife plant flowering over Germany
Biogeosciences Discuss., 12, 18389-18423, doi:10.5194/bgd-12-18389-2015, 2015
Recording of climate and diagenesis through fossil pigments and sedimentary DNA at Laguna Potrok Aike, Argentina
Summary: Aquatic sediments record climatic conditions while providing ecological niches for microorganisms. In deep lacustrine settings, the relationship between environmental features and sedimentary DNA remains largely unknown. Here we compare microbial assemblages with lacustrine conditions defined for their respective sediments. Results of fossil pigments and 16S rRNA libraries show that sedimentary DNA from various time intervals provides essential information to complement environmental indicators.
Biogeosciences Discuss., 12, 18345-18388, doi:10.5194/bgd-12-18345-2015, 2015
Dead zone or oasis in the open ocean? Zooplankton distribution and migration in low-oxygen modewater eddies
Summary: In a low-oxygen eddy in the tropical Atlantic, total zooplankton biomass was increased. Larger plankton avoided the oxygen minimum zone (OMZ,<20 µmol O2 kg-1). We identified four strategies by different plankton groups: i) shallow OMZ avoidance and compression at surface, ii) migration to shallow OMZ core during daytime, migration to surface at nighttime, iii) residing in shallow OMZ day and night, and iv) migration through the shallow OMZ from oxygenated depths to surface and back.
Biogeosciences Discuss., 12, 18315-18344, doi:10.5194/bgd-12-18315-2015, 2015
Bathypelagic particle flux signatures from a suboxic eddy in the oligotrophic tropical North Atlantic: production, sedimentation and preservation
Summary: Particle fluxes at the Cape Verde Ocean Observatory in the eastern tropical North Atlantic for the period December 2009 until May 2011 are discussed based on deep sediment trap time series data collected at 1290 m and 3439 m water depth. The typically open ocean flux pattern with weak seasonality is modified by the appearance of a highly productive and low oxygen eddy in winter 2010. The eddy passage was accompanied by high biogenic and lithogenic fluxes, lasting from December 2009 to May 2010.
Biogeosciences Discuss., 12, 18253-18313, doi:10.5194/bgd-12-18253-2015, 2015
The climatic imprint of bimodal distributions in vegetation cover for West Africa
Biogeosciences Discuss., 12, 18213-18251, doi:10.5194/bgd-12-18213-2015, 2015
Estimation of nutrient contributions from the ocean across a river basin using stable isotope analysis
Summary: We conducted field experiments to understand the recycling of total nitrogen from the ocean across an entire river basin using stable isotope analysis. To our best knowledge, for the world's first we estimated the marine derived nutrients recycling rate. This study also demonstrates that TN may be recycled from the ocean to the river basin not only directly due to runs of salmon, but also indirectly due to subsequent transportation processes, such as sea eagles feeding and defecation.
Biogeosciences Discuss., 12, 18185-18211, doi:10.5194/bgd-12-18185-2015, 2015
Foraging segregation of two congeneric diving seabird species (common and thick-billed murres) breeding on St. George Island, Bering Sea
Biogeosciences Discuss., 12, 18151-18183, doi:10.5194/bgd-12-18151-2015, 2015
The keystone species of Precambrian deep bedrock biosphere belong to Burkholderiales and Clostridiales
Summary: This study describes the microbial community structure, networks and the keystone organisms in the deep crystalline bedrock fracture fluid systems of depth range from 180 m to 2.3 km. The functionality of these microbial communities is assessed through predictive analysis of the metagenome and correlation of the microbial communities to geochemistry. The microbial communities in this bedrock fracture system share features with serpenization-driven microbial communities in alkaline aquifers.
Biogeosciences Discuss., 12, 18103-18150, doi:10.5194/bgd-12-18103-2015, 2015
Ideas and perspectives: why Holocene thermokarst sediments of the Yedoma region do not increase the northern peatland carbon pool
Summary: We investigate the properties of soils and sediments in a particular and ancient Siberian permafrost landscape. We critically examine statements from a recent study that specific permafrost landforms affected by thawed permafrost (alases) in this region contain very large quantities of peat that previous studies had failed to include because of dataset biases. We conclude that there is no evidence to suggest biases in existing datasets or that alas deposits increase the northern peatland pool.
Biogeosciences Discuss., 12, 18085-18101, doi:10.5194/bgd-12-18085-2015, 2015
Biological and climatic controls on leaf litter decomposition across European forests and grasslands revealed by reciprocal litter transplantation experiments
Summary: We studied tree and grass litter decomposition across several climates in Europe. This study demonstrates that climatic (air temperature and precipitation regimes) controls on litter decomposition are quantitatively more important than species, litter origin and soil type. The data was used to generate prediction models of carbon and nitrogen release during the decomposition period. These models are also relevant to predict litter nutrient turnover in a climate change scenario.
Biogeosciences Discuss., 12, 18053-18084, doi:10.5194/bgd-12-18053-2015, 2015
Combining multi-spectral proximal sensors and digital cameras for monitoring grazed tropical pastures
Summary: Proximal sensors could assist in managing feed in livestock production systems but raw data needs calibration to biophysical values such as biomass and ground cover. Our pilot project monitored tropical pastures for 18 months using digital cameras, multispectral sensors, soil moisture sensors and field measurements. Multispectral sensor data were unreliable and required stringent cleaning. Despite this we found strong relationships between sensor and field measurements during the wet season.
Biogeosciences Discuss., 12, 18007-18051, doi:10.5194/bgd-12-18007-2015, 2015
Modeling spatial–temporal dynamics of global wetlands: comprehensive evaluation of a new sub-grid TOPMODEL parameterization and uncertainties
Summary: Based on state-of-the-art modeling technology and remote sensing, the estimate of the mean annual maximum of global wetlands is ~5.17 Mkm2 for 1980-2010, with a global wetland potential of ~10.3 Mkm2. This study shows the opportunity to minimize the uncertainty of wetland estimates across existing results and will consequently provide accurate estimates of methane (CH4) emissions from wetlands at global scale.
Biogeosciences Discuss., 12, 17953-18006, doi:10.5194/bgd-12-17953-2015, 2015
Methane and sulfate dynamics in sediments from mangrove-dominated tropical coastal lagoons, Yucatán, Mexico
Summary: A transport-reaction model was used to simulate porewater methane and sulfate concentrations. Model results and sediment slurry incubation experiments show high methane production rates supported by non-competitive substrates and ample dissolved and labile organic matter as well as methane from deeper sediment through bubbles dissolution and diffusion. The shallow methane production and accumulation depths in these sediments promote high methane fluxes to the water column and atmosphere.
Biogeosciences Discuss., 12, 17913-17951, doi:10.5194/bgd-12-17913-2015, 2015
Trace elements transport in western Siberia rivers across a permafrost gradient
Summary: Towards a better understanding of trace element transport in permafrost-affected Earth surface environments, we sampled 60 rivers of Western Siberia Lowland (WSL) during spring, summer and winter across a 1500 km-gradient of various permafrost zones and we analyzed 40 trace elements (TE) in the river water. The climate change in western Siberia will affect mainly the elements controlled by underground water feeding (Ca, Sr, Mo, Sb, As and U). The impact of the permafrost thaw on TE export from t
Biogeosciences Discuss., 12, 17857-17912, doi:10.5194/bgd-12-17857-2015, 2015
Ideas and perspectives: truffles not radioactive
Summary: Although ranging among the most expensive gourmet foods, it remains unclear if truffles accumulate radioactivity at a harmful level comparable to other fungi. Insignificant radiocaesium concentrations in specimens from Switzerland, Germany, France, Italy and Hungary provide an all clear for truffle hunters and cultivators in Europe as well as dealers and customers from around the world.
Biogeosciences Discuss., 12, 17851-17856, doi:10.5194/bgd-12-17851-2015, 2015
Prescribed-burning vs. wildfire: management implications for annual carbon emissions along a latitudinal gradient of Calluna vulgaris-dominated vegetation
Summary: We modelled carbon emissions after prescribed burning in heathlands and showed they are linked to biomass production patterns determined by climate. Burning rotations that minimize C losses in one specific place can maximize losses in others. It is a challenge to design management plans for reducing carbon losses, especially when we superimposed wildfires on burning rotations. Predicted increases in wildfire frequencies interact and modify these optimum burning rotation intervals for C loss.
Biogeosciences Discuss., 12, 17817-17849, doi:10.5194/bgd-12-17817-2015, 2015
The significance of nitrogen regeneration for new production within a filament of the Mauritanian upwelling system
Summary: Based in the Mauritanian Upwelling System, the article describes a lagrangian study of biogeochemical processes within a freshly upwelled body of water as it advects offshore. We report rates of primary production, nitrogen assimilation and regeneration and describe how these processes relate to the dynamics of the upwelling regime. This system is perhaps the least studied of the four major eastern boundary upwelling systems and so these measurements provide important new insights.
Biogeosciences Discuss., 12, 17781-17816, doi:10.5194/bgd-12-17781-2015, 2015
Change in coccolith morphology by responding to temperature and salinity in coccolithophore Emiliania huxleyi (Haptophyta) isolated from the Bering and Chukchi Seas
Summary: Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic Oceans during the R/V MIRAI cruise in 2010 (MR10-05) were established as clone cultures and have been maintained in the laboratory at 15°C and 32‰ salinity. This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. Taken together, our results suggest that calcification productivity may be used to predict future ocea
Biogeosciences Discuss., 12, 17751-17780, doi:10.5194/bgd-12-17751-2015, 2015
Seasonal distribution of short-tailed shearwaters and their prey in the Bering and Chukchi Seas
Summary: To investigate seasonal distribution of short-tailed shearwaters we conducted vessel-based seabird surveys and net samplings of krill, i.e., their main prey, during summer and fall in the Bering Sea and Chukchi Sea. Short-tailed shearwaters in the Bering Sea during summer moved to feed in the Chukchi Sea during fall when the large size of krill increased in the Chukchi Sea.
Biogeosciences Discuss., 12, 17721-17750, doi:10.5194/bgd-12-17721-2015, 2015
Differential responses of seabirds to inter-annual environmental change in the continental shelf and oceanic habitats of southeastern Bering Sea
Summary: In the southeastern Bering Sea where sea-ice cover has been decreasing, red-legged kittiwakes did not change their foraging locations largely in relation to marine environmental changes between two years probably due to their reliance on myctophids, while thick-billed murres showed fluctuations in physiological condition and flexible foraging behavior on the shelf. The results suggest there might be interspecific differences in these species’ response to warming in the Bering Sea, which may refl
Biogeosciences Discuss., 12, 17693-17720, doi:10.5194/bgd-12-17693-2015, 2015
Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales
Summary: A more than two-decadal sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analyzed with respect to deep ocean mass fluxes, flux components and their variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal timescales possibly linked to the Atlantic Multidedadal Oscillation (AMO). High winter fluxes of biogenic silica (BSi), used as a measure of mar
Biogeosciences Discuss., 12, 17643-17692, doi:10.5194/bgd-12-17643-2015, 2015
Estimates of common ragweed pollen emission and dispersion over Europe using RegCM-pollen model
Summary: To study the distribution of airborne ragweed pollen in changing environment and associated health risk over Europe, we introduce an approach with explicit treatment of pollen ripening, release and dispersion due to environmental driver in an online modelling framework where climate is integrated with dispersion and vegetation production. From simulated pollen season and concentration pattern health risks are evaluated through calculation of exposure time above health-relevant threshold levels.
Biogeosciences Discuss., 12, 17595-17641, doi:10.5194/bgd-12-17595-2015, 2015
Effects of CO2 perturbation on phosphorus pool sizes and uptake in a mesocosm experiment during a low productive summer season in the northern Baltic Sea
Summary: Studies investigating the effect of increasing CO2 levels on the phosphorus cycle in natural waters are lacking although phosphorus often controls phytoplankton development in aquatic systems. The aim of our study was to analyze effects of elevated CO2 levels on phosphorus pool sizes and uptake. Therefore, we conducted a CO2-manipulation mesocosm experiment in the Storfjärden (western Gulf of Finland, Baltic Sea) in summer 2012. We compared the phosphorus dynamics in different mesocosm treatment
Biogeosciences Discuss., 12, 17543-17593, doi:10.5194/bgd-12-17543-2015, 2015
No observed effect of ocean acidification on nitrogen biogeochemistry in a summer Baltic Sea plankton community
Biogeosciences Discuss., 12, 17507-17541, doi:10.5194/bgd-12-17507-2015, 2015
Evolution of dissolved and particulate chromophoric materials during the VAHINE mesocosm experiment in the New Caledonian coral lagoon (South West Pacific)
Summary: In the framework of the VAHINE project, we investigated the spectral characteristics and the variability of dissolved and particulate chromophoric materials throughout a 23-day mesocosm experiment conducted in the South West Pacific at the exit of the New Caledonian coral lagoon. We found that the dynamics of CDOM and particulate matter absorption were strongly coupled with those of cyanobacteria Synechococcus spp. and bacterial production.
Biogeosciences Discuss., 12, 17453-17505, doi:10.5194/bgd-12-17453-2015, 2015
Water level, vegetation composition and plant productivity explain greenhouse gas fluxes in temperate cutover fens after inundation
Summary: Small sedges with water close to surface were minor methane emitters and net CO2 sinks, while shallow or deep flooded Phragmites australis sites released large amounts of CH4 and sequestered very much CO2. Floating mats of Carex tussocks and Typha latifolia were a source for both CH4 and CO2. Shallow, stable flooding of cutover fens seems to be a better measure to arrive at low GHG emissions than deep flooding, but the latter could be an alternative when Phragmites australis can be established.
Biogeosciences Discuss., 12, 17393-17452, doi:10.5194/bgd-12-17393-2015, 2015
Temperature-mediated changes in microbial carbon use efficiency and 13C discrimination
Biogeosciences Discuss., 12, 17367-17392, doi:10.5194/bgd-12-17367-2015, 2015
Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions
Summary: The diel vertical migration of zooplankton and nekton results in an active export of carbon and nitrogen from the oceans surface layer. In vast areas of the ocean the daytime distribution depth of migrating organisms corresponds to the core of an oxygen minimum zone (OMZ). We show that exposure to OMZ conditions can result in a strong depression of respiration and ammonium excretion in zooplankton, a fact that needs to be considered when calculating carbon and nitrogen fluxes in OMZ regions.
Biogeosciences Discuss., 12, 17329-17366, doi:10.5194/bgd-12-17329-2015, 2015
Importance of within-lake processes in affecting the dynamics of dissolved organic carbon and dissolved organic and inorganic nitrogen in an Adirondack forested lake/watershed
Biogeosciences Discuss., 12, 17285-17327, doi:10.5194/bgd-12-17285-2015, 2015
Generation of a global fuel dataset using the Fuel Characteristic Classification System
Summary: This paper presents the first global fuel dataset, containing all the parameters required to be input in the Fuel Characteristic Classification System (FCCS). It was developed from different spatial variables, both based on satellite Earth Observation products and fuel databases. This dataset could be used for different applications, including fire danger assessment, fire behavior estimations, fuel consumption calculations and emissions inventories.
Biogeosciences Discuss., 12, 17245-17284, doi:10.5194/bgd-12-17245-2015, 2015
Soluble trace metals in aerosols over the tropical south east Pacific offshore of Peru
Summary: Concentrations of major ions and trace metals were measured in aerosols off the coast of Peru in December 2012. A few trace metals (iron, copper, nickel and cobalt had anomalously high concentrations, which may be associated with industrial metal smelting activities in the region. The atmosphere appears to supply an excess of iron (relative to atmospheric nitrogen supply) to the phytoplankton community of the Peruvian upwelling system.
Biogeosciences Discuss., 12, 17219-17243, doi:10.5194/bgd-12-17219-2015, 2015
Impact of water table level on annual carbon and greenhouse gas balances of a restored peat extraction area
Biogeosciences Discuss., 12, 17177-17218, doi:10.5194/bgd-12-17177-2015, 2015
Structural effects of liana presence in secondary tropical dry forests using ground LiDAR
Summary: Lianas, woody vines, tend to respond positively to disturbance and show high density in secondary forests. Lianas are a key component of tropical forests, because they may reduce carbon potential. Identifying tools for liana detection, it is therefore essential for monitoring changes in tropical forests. In this study, we describe how terrestrial laser scanning can be used to detect the presence of lianas in forest stands of different ages in secondary tropical dry forests at a regional scale.
Biogeosciences Discuss., 12, 17153-17175, doi:10.5194/bgd-12-17153-2015, 2015
Photochemical mineralisation in a humic boreal lake: temporal variability and contribution to carbon dioxide production
Summary: Temporal variability in the apparent quantum yield of photochemical CDOM mineralisation in a humic boreal lake was severalfold smaller than previously reported across different lakes. Simulated DIC photoproduction (2012-2014) averaged 4.5 ± 0.2 g C m-2 yr-1, which represented 3% of the mean CO2 emissions observed from this lake. Even when using the most photoreactive water sample for annual simulation the contribution of sunlight to CO2 emissions remained minor (7%).
Biogeosciences Discuss., 12, 17125-17152, doi:10.5194/bgd-12-17125-2015, 2015
Negligible effects of ocean acidification on Eurytemora affinis (Copepoda) offspring production
Summary: We studied the effects of ocean acidification (OA) on the aquatic crustacean Eurytemora affinis and measured offspring production in relation to pH, chlorophyll, algae, fatty acids and oxidative stress. No effects on offspring production or effects via food were found. E. affinis seems robust against OA on a physiological level and did probably not face acute pH stress in the treatments, as the species naturally face large pH fluctuations.
Biogeosciences Discuss., 12, 17093-17123, doi:10.5194/bgd-12-17093-2015, 2015
A multiproxy approach to understanding the "enhanced" flux of organic matter through the oxygen deficient waters of the Arabian Sea
Summary: Drifting sediment traps were deployed in the oxygen deficient waters of the Arabian Sea, where the sinking flux is less attenuated than in more oxic waters. Six mechanisms that might explain this ‘enhanced flux’ were evaluated. In the upper 500 meters, evidence was found supporting an oxygen effect and/or changes in the efficiency of the microbial loop including the addition of chemoautotrophic carbon to the sinking flux.
Biogeosciences Discuss., 12, 17051-17092, doi:10.5194/bgd-12-17051-2015, 2015
The mechanism of oxygen isotope fractionation during N2O production by denitrification
Summary: Oxygen isotopic signatures of N2O are formed in a complex multistep enzymatic reactions and depend on isotopic fractionation during enzymatic reduction of nitrate to N2O and on the oxygen isotope exchange with soil water. We propose a new method for quantification of oxygen isotope exchange, with simultaneous determination of oxygen isotopic signatures, to decipher the mechanism of oxygen isotopic fractionation. We indicate the differences between fractionation mechanisms by various pathways.
Biogeosciences Discuss., 12, 17009-17049, doi:10.5194/bgd-12-17009-2015, 2015
Aligning MIS5 proxy records from Lake Ohrid (FYROM) with independently dated Mediterranean archives: implications for core chronology
Biogeosciences Discuss., 12, 16979-17007, doi:10.5194/bgd-12-16979-2015, 2015
Processes regulating progressive nitrogen limitation under elevated carbon dioxide: a meta-analysis
Biogeosciences Discuss., 12, 16953-16977, doi:10.5194/bgd-12-16953-2015, 2015
The fate of 5N-nitrate in mesocosms from five European peatlands differing in long-term nitrogen deposition rate
Biogeosciences Discuss., 12, 16913-16951, doi:10.5194/bgd-12-16913-2015, 2015
Autotrophic component of soil respiration is repressed by drought more than the heterotrophic one in a dry grassland
Summary: In the dry grassland investigated in this study the components of the soil CO2 efflux decreased at different rates under drought conditions. During drought the contribution made by the heterotrophic components was the highest and the rhizospheric component was the most sensitive to soil drying. According to our results, the heterotrophic component of soil respiration is the major contributor to the respiration activities during drought events.
Biogeosciences Discuss., 12, 16885-16911, doi:10.5194/bgd-12-16885-2015, 2015
The effect of using the plant functional type paradigm on a data-constrained global phenology model
Summary: The plant functional type (PFT) concept is widely used in global vegetation models but recent studies have attempted to replace this with a more biologically representative formulation by using plant traits. In this study we aim to quantify the performance of a data-constrained leaf phenology model that uses PFTs when compared to one that uses local traits. We show that the PFT model performs relatively poorly but we can identify a small number of traits that improve model performance and form a
Biogeosciences Discuss., 12, 16847-16884, doi:10.5194/bgd-12-16847-2015, 2015
Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific
Biogeosciences Discuss., 12, 16803-16845, doi:10.5194/bgd-12-16803-2015, 2015
Benthic phosphorus cycling in the Peruvian oxygen minimum zone
Summary: The study presents a P budget including the P input from the water column, the P burial in the sediments as well as the P release from the sediments. We found that the P input could not maintain the P release rates. Consideration other P sources, e.g. terrigenous P and P released from the dissolution of Fe oxyhydroxides, showed that none of these can account for the missing P . Thus, it is likely that abundant sulfide oxidizing bacteria release the missing P during our measurement period.
Biogeosciences Discuss., 12, 16755-16801, doi:10.5194/bgd-12-16755-2015, 2015
Distribution of tetraether lipids in agricultural soils – differentiation between paddy and upland management
Biogeosciences Discuss., 12, 16709-16754, doi:10.5194/bgd-12-16709-2015, 2015
Carbon dioxide exchange of a perennial bioenergy crop cultivation on a mineral soil
Summary: We showed that the reed canary grass (RCG) was environmentally friendly from the CO2 balance point of view when cultivated on a mineral soil. When compared to the earlier findings on the same crop on organic soil site, the capacity of the crop to withdraw atmospheric CO2 was even stronger on mineral soil site than that on the organic soil site. For full estimation of the climatic impacts of this bioenergy system, a life cycle assessment will be needed.
Biogeosciences Discuss., 12, 16673-16708, doi:10.5194/bgd-12-16673-2015, 2015
Interactive effects of and light on growth rates and RUBISCO content of small and large centric diatoms
Summary: Marine photosynthetic diatoms span a range of cellular sizes, with important implications for carbon cycling. Nitrogen is increasing rapidly in coastal areas. We grew small and large marine centric diatoms and found that under low nitrogen media both strains conserved their cellular allocation of nitrogen to their photosynthetic system. The large diatom grew faster under low nitrogen, while the small diatom could exploit high levels of nitrogen to grow faster.
Biogeosciences Discuss., 12, 16645-16672, doi:10.5194/bgd-12-16645-2015, 2015
Runoff- and erosion-driven transport of cattle slurry: linking molecular tracers to hydrological processes
Summary: Our interdisciplinary research brings together methodologies from hydrology, soil science and biogeochemistry to address key questions about the transport of cattle slurry in the environment. The paper provides a novel approach to trace dissolved and particulate components of cattle slurry through an experimental hillslope system. This work provides one of the first examples of using biomarkers to assess the effects of slope gradient and rainfall intensity on the movement of slurry derived-OM.
Biogeosciences Discuss., 12, 16603-16644, doi:10.5194/bgd-12-16603-2015, 2015
Upwellings mitigated Plio–Pleistocene heat stress for reef corals on the Florida platform (USA)
Summary: We present the first record of reef coral calcification rates from the fossil record. The corals investigated derive from the Florida carbonate platform and are of middle Pliocene to early Pleistocene age. The calcification data in combination with stable isotope proxy data document intermittent upwelling on annual to decadal time-scales. Calcification rates were lower than at present, but enhanced during periods of upwelling. This is likely an effect of dampened SSTs during the upwelling.
Biogeosciences Discuss., 12, 16553-16602, doi:10.5194/bgd-12-16553-2015, 2015
Phosphorus fertilisation under nitrogen limitation can deplete soil carbon stocks – evidence from Swedish meta-replicated long-term field experiments
Summary: Nutrients determine the balance between inputs and outputs to and from the soil and thus exert a strong impact on the total soil organic carbon stock. However, for phosphorus, this impact has not been comprehensively addressed. Here we show in ten different long-term experiments, that phosphorus fertilization can significantly deplete soil carbon stocks, despite a positive impact on plant growth and thus carbon inputs. Thus, soil carbon decay is most likely stimulated even stronger.
Biogeosciences Discuss., 12, 16527-16551, doi:10.5194/bgd-12-16527-2015, 2015
Reviews and syntheses: Greenhouse gas emissions in natural and agricultural lands in sub-Saharan Africa: synthesis of available data and suggestions for further studies
Summary: This paper synthesizes the available data on greenhouse gas (GHG) emissions from African agricultural and natural lands. African natural and agricultural lands are a significant source of GHG. However, there are huge research gaps and understanding of Africa’s contribution to global GHG emissions remains highly uncertain. The strategy for addressing this data gap involves identifying priorities for data acquisition, utilizing appropriate technologies, and establishing networks and collaboration.
Biogeosciences Discuss., 12, 16479-16526, doi:10.5194/bgd-12-16479-2015, 2015
Isotopic evidence for biogenic molecular hydrogen production in the Atlantic Ocean
Summary: Oceans are a source of H2, an indirect greenhouse gas. Measurements constraining the temporal and spatial patterns of oceanic H2 emissions are sparse and although H2 is assumed to be produced mainly biologically, direct evidence for biogenic marine production was lacking. By analyzing the H2 isotopic composition (δD) we were able to constrain the global H2 budget in more detail, verify biogenic production and point to additional sources. We also showed that current models are reasonably working.
Biogeosciences Discuss., 12, 16431-16477, doi:10.5194/bgd-12-16431-2015, 2015
Effects of different N sources on riverine DIN export and retention in subtropical high-standing island, Taiwan
Summary: The mean riverine DIN export of 49 watersheds in Taiwan is ~3,800 kg-N km-2 yr-1, 18 times the global average. The mean riverine DIN export ratio is 0.30-0.51, which is much higher than the average of 0.20-0.25 of large rivers around the world indicating excessive N input relative to ecosystem retention capacity. DIN export ratio is positively related to agriculture input and levels of human disturbanc and watersheds with high DIN export rations are likely at advanced stages of N excess.
Biogeosciences Discuss., 12, 16397-16430, doi:10.5194/bgd-12-16397-2015, 2015
Water mass characteristics and their temporal changes in a biological hotspot in the southern Chukchi Sea
Summary: We analysed mooring and ship-based data obtained from a biological hotspot in the southern Chukchi Sea. Mooring data were collected for the first time in this site and were captured during spring and fall blooms with high chlorophyll a concentrations. The data suggest that a dome-like structure of the bottom water and nutrient regeneration at the bottom play important roles in maintaining the fall bloom of the biological hotspot.
Biogeosciences Discuss., 12, 16359-16396, doi:10.5194/bgd-12-16359-2015, 2015
Coupling carbon allocation with leaf and root phenology predicts tree-grass partitioning along a savanna rainfall gradient
Summary: We present a new approach for modelling coupled phenology and carbon allocation in savannas, and test it using data from the OzFlux network. Model behaviour emerges from complex feed-backs between the plant physiology and vegetation dynamics, in response to resource availability, and not from imposed hypotheses about the controls on tree/grass co-existence. Results indicate that resource limitation is a stronger determinant of tree cover than disturbance in Australian savannas.
Biogeosciences Discuss., 12, 16313-16357, doi:10.5194/bgd-12-16313-2015, 2015
Composition of ammonia-oxidizing archaea and their contribution to nitrification in a high-temperature hot spring
Summary: The oxidation of ammonia by microbes and associated organisms has been shown to occur in diverse natural environments. However, the contribution of ammonia- oxidizing archaea to nitrification in high-temperature environments remains unclear. Here, we studied in situ ammonia oxidation rates and the abundance of ammonia-oxidizing archaea (AOA) in a high-temperature hot spring. This study demonstrated that AOA were widely involved in nitrification in this hot spring.
Biogeosciences Discuss., 12, 16255-16283, doi:10.5194/bgd-12-16255-2015, 2015
Recent decline of the Black Sea oxygen inventory
Summary: We show that the Black Sea oxygen inventory has decreased by 36% from 1955 to 2013, while oxygen penetration depth decreased from 140m to 90m. A transient increase of the oxygen inventory during 1985-1995 supported the perception of a stable oxic interface and of a general recovery of the Black Sea after a strong eutrophication phase (1970-1990). Instead, we show that ongoing high oxygen consumption were masked by high ventilation rates, which are now limited by atmospheric warming.
Biogeosciences Discuss., 12, 16233-16253, doi:10.5194/bgd-12-16233-2015, 2015
Seasonal variations in metallic mercury (Hg0) vapor exchange over biannual wheat – corn rotation cropland in the North China Plain
Biogeosciences Discuss., 12, 16105-16158, doi:10.5194/bgd-12-16105-2015, 2015
Gastropod diversification and community structuring processes in ancient Lake Ohrid: a metacommunity speciation perspective
Biogeosciences Discuss., 12, 16081-16103, doi:10.5194/bgd-12-16081-2015, 2015
Age structure, carbonate production and shell loss rate in an Early Miocene reef of the giant oyster Crassostrea gryphoides
Summary: We present the first analysis of population structure and cohort distribution in a fossil oyster reef. Data derive from Terrestrial Laser Scanning of a Miocene shell bed covering 459 m². A growth model was calculated, revealing this species as the giant oyster Crassostrea gryphoides was the fastest growing oyster known so far. The shell half-lives range around few years, indicating that oyster reefs were geologically short-lived structures, which were degraded on a decadal scale.
Biogeosciences Discuss., 12, 15867-15900, doi:10.5194/bgd-12-15867-2015, 2015
Ocean acidification modulates expression of genes and physiological performance of a marine diatom
Biogeosciences Discuss., 12, 15809-15833, doi:10.5194/bgd-12-15809-2015, 2015
Vegetation structure and fire weather influence variation in burn severity and fuel consumption during peatland wildfires
Summary: We examined the variables controlling fire severity and the amount of vegetation burnt during wildfires and prescribed burns. Fire severity varied strongly within and between wildfires in relation to fire-weather conditions and vegetation type. The amount of surface vegetation burnt was a function of the amount available pre-fire, whilst moss layer consumption related to prolonged dry periods. Moss flammability may explain the higher carbon-release during wildfires compared to prescribed burns.
Biogeosciences Discuss., 12, 15737-15762, doi:10.5194/bgd-12-15737-2015, 2015
A new mechanistic framework to predict OCS fluxes from soils
Biogeosciences Discuss., 12, 15687-15736, doi:10.5194/bgd-12-15687-2015, 2015
Uncertainty and sensitivity in optode-based shelf-sea net community production estimates
Summary: Our work explores the estimation of NCP using an oxygen time-series from a surface SmartBuoy mooring located in the Thames river plume. Our study site is identified as a region of net heteotrophy with strong seasonal variability. Short term daily variability in oxygen is demonstrated to make accurate individual estimates challenging. The effects of bubble induced supersaturation is shown to have a large influence on cumulative annual estimates.
Biogeosciences Discuss., 12, 15611-15654, doi:10.5194/bgd-12-15611-2015, 2015
Predicting biomass of hyperdiverse and structurally complex Central Amazon forests – a virtual approach using extensive field data
Summary: Predicting biomass correctly at the landscape-level in tropical forests requires the inclusion of predictors related to species architecture. The model of interest should comprise the floristic composition and size-distribution variability of the target forest, implying that even generic pantropical models can lead to strong biases. Reliable biomass assessments for the Amazon basin still depend on the collection of destructive allometry data at the local/regional scale and forest inventories.
Biogeosciences Discuss., 12, 15537-15581, doi:10.5194/bgd-12-15537-2015, 2015
No-tillage lessens soil CO2 emissions the most under arid and sandy soil conditions: results from a meta-analysis
Summary: Discrepancies exist on the impact of tillage on soil CO2 emissions and on the main soil and environmental controls. Results from a meta-analysis using 174 paired observations comparing CO2 emissions over entire seasons or years from tilled and untilled soils across different climates, crop types and soil conditions show that on average: (1) tilled soils emit 21% more CO2 than untilled soils; (2) the difference increase to 29% in sandy soils from arid climates with low soil organic carbon content
Biogeosciences Discuss., 12, 15495-15535, doi:10.5194/bgd-12-15495-2015, 2015
Evidence of old soil carbon in grass biosilica particles
Summary: We characterize the origin of carbon within phytoliths (biosilica of higher plants) by a multi-isotope approach. We show that phytoliths occlude soil organic carbon, making them unsuitable for paleo-proxy studies, radiocarbon dating or atmospheric CO2 sequestration. Our findings are in parallel with recent soil paradigm-shifts showing that soil microbes access old carbon, and therefore adds important information on the role of old carbon in root-plant and biomineralization interactions.
Biogeosciences Discuss., 12, 15369-15410, doi:10.5194/bgd-12-15369-2015, 2015
Proximate and ultimate controls on carbon and nutrient dynamics of small agricultural catchments
Summary: Direct human impact on a catchment (fertilizer input, soil disturbance, urbanization) is asymmetrically linked with inherent catchment properties (geology, soil, topography), which together determine catchment vulnerability to human activity. To quantify the influence of physical, hydrologic, and anthropogenic controls on surface water quality, we used a five years high-frequency water chemistry dataset from three contrasting headwater catchments in western France.
Biogeosciences Discuss., 12, 15337-15367, doi:10.5194/bgd-12-15337-2015, 2015
Smallholder African farms in western Kenya have limited greenhouse gas fluxes
Biogeosciences Discuss., 12, 15301-15336, doi:10.5194/bgd-12-15301-2015, 2015
Combining two complementary micrometeorological methods to measure CH4 and N2O fluxes over pasture
Summary: We continuously measured CH4 and N2O fluxes on two pastures that differed with respect to management. Two micrometeorological ratio methods were used; one was more suitable for daytime and the other for night-time. Over a year, both methods indicated both sites as net sources of CH4 and N2O, similar to other managed grasslands. At the irrigated, fertilised and rotationally-grazed site, the N2O emissions were 1.19 (±0.15) % of the nitrogen inputs from animal excreta and fertiliser application.
Biogeosciences Discuss., 12, 15245-15299, doi:10.5194/bgd-12-15245-2015, 2015
Moderate topsoil erosion rates constrain the magnitude of the erosion-induced carbon sink and agricultural productivity losses on the Chinese Loess Plateau
Biogeosciences Discuss., 12, 14981-15010, doi:10.5194/bgd-12-14981-2015, 2015
Interannual variability of the Mediterranean trophic regimes from ocean color satellites
Biogeosciences Discuss., 12, 14941-14980, doi:10.5194/bgd-12-14941-2015, 2015
Time since death and decay rate constants of Norway spruce and European larch deadwood in subalpine forests determined using dendrochronology and radiocarbon dating
Summary: The time scales involved in the decay of coarse woody debris (CWD) of spruce and larch in Alpine forests are largely unknown. Dendrochronology and 14C dating were used to assess the time that had elapsed since tree death. Distinct differences between tree species occur only at an advanced stage of decay. Larch CWD reaches an age of 210 years and spruce 77 years. Using this approach, the half-lives of cellulose (21 y for spruce and 50 y for larch) and lignin (> 100 y) could be determined.
Biogeosciences Discuss., 12, 14797-14832, doi:10.5194/bgd-12-14797-2015, 2015
Calculations of automatic chamber flux measurements of methane and carbon dioxide using short time series of concentrations
Biogeosciences Discuss., 12, 14593-14617, doi:10.5194/bgd-12-14593-2015, 2015
Biogeochemical characteristics of a long-lived anticyclonic eddy in the eastern South Pacific Ocean
Biogeosciences Discuss., 12, 14481-14506, doi:10.5194/bgd-12-14481-2015, 2015
Contributions of dynamic environmental signals during life-cycle transitions to early life-history traits in lodgepole pine (Pinus contorta Dougl.)
Summary: We explored the causes and consequences for the evolution of life-history traits (seed dormancy & size) in lodgepole pine in British Columbia, Canada and found that dynamic climate rather than constant geography are the environmental driving forces in seed dormancy and size variations. Evapotranspiration and precipitation are the most critical climate variables and we predicted that levels of seed dormancy in lodgepole pine would increase across large geographical tracts in 2050s.
Biogeosciences Discuss., 12, 14105-14138, doi:10.5194/bgd-12-14105-2015, 2015
The potential effects of fresh water content on the primary production in the Chukchi Sea
Biogeosciences Discuss., 12, 13511-13544, doi:10.5194/bgd-12-13511-2015, 2015
Contribution of Marine Group II Euryarchaeota to cyclopentyl tetraethers in the Pearl River estuary and coastal South China Sea: impact on the TEX86 paleothermometer
Biogeosciences Discuss., 12, 12455-12484, doi:10.5194/bgd-12-12455-2015, 2015
Controls on microalgal community structures in cryoconite holes upon high Arctic glaciers, Svalbard
Summary: The diversity of microalgae and cyanobacteria in cryoconites on three high Arctic glaciers was investigated. Possible bottom-up controls via nutrient limitation, wind dispersal, and hydrological stability were measured. Grazer populations were quantified to estimate the effect of top-down controls. Nutrient limitation appeared to be the most important control on the diversity and competition outcomes of microalgae and cyanobacteria.
Biogeosciences Discuss., 12, 11751-11795, doi:10.5194/bgd-12-11751-2015, 2015
Technical Note: An improved guideline for rapid and precise sample preparation of tree-ring stable isotope analysis
Biogeosciences Discuss., 12, 11587-11623, doi:10.5194/bgd-12-11587-2015, 2015
Reviews and Syntheses: Ocean acidification and its potential impacts on marine ecosystems
Biogeosciences Discuss., 12, 10939-10983, doi:10.5194/bgd-12-10939-2015, 2015
Short-term changes in a microplankton community in the Chukchi Sea during autumn: consequences of a strong wind event
Summary: We studied short-term changes in microplankton community in the western Arctic Ocean with regards to responses to the strong wind event （SWE）during autumn (September 2013). SWE supplied sufficient nutrients to the surface layer that then enhance the small pennate diatom bloom under the weak stratification water column. SWE during autumn may have function to accelerate the seasonal succession of the microplankton community from summer to winter.
Biogeosciences Discuss., 12, 8789-8817, doi:10.5194/bgd-12-8789-2015, 2015