Annual litterfall dynamics and nutrient deposition depending on elevation and land use at Mt. Kilimanjaro
Biogeosciences Discuss., 12, 10031-10057, doi:10.5194/bgd-12-10031-2015, 2015
Changing nutrient stoichiometry affects phytoplankton production, DOP build up and dinitrogen fixation – a mesocosm experiment in the eastern tropical North Atlantic
Biogeosciences Discuss., 12, 9991-10029, doi:10.5194/bgd-12-9991-2015, 2015
Composition and sources of sedimentary organic matter in the deep Eastern Mediterranean Sea
Biogeosciences Discuss., 12, 9935-9989, doi:10.5194/bgd-12-9935-2015, 2015
Thermocline mixing and vertical oxygen fluxes in the stratified central North Sea
Biogeosciences Discuss., 12, 9905-9934, doi:10.5194/bgd-12-9905-2015, 2015
Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil
Biogeosciences Discuss., 12, 9879-9903, doi:10.5194/bgd-12-9879-2015, 2015
Earth system responses to cumulative carbon emissions
Biogeosciences Discuss., 12, 9839-9877, doi:10.5194/bgd-12-9839-2015, 2015
Controls on dissolved organic matter (DOM) degradation in a headwater stream: the influence of photochemical and hydrological conditions in determining light-limitation or substrate-limitation of photo-degradation
Summary: This study investigates how sunlight, dissolved organic matter (DOM) concentration and composition, and hydrology interact to control DOM degradation in headwater streams. In Imnavait Creek, a shallow, low-relief stream in the Arctic, DOM degradation by sunlight was limited by light under all conditions. Study results were used to synthesize controls on DOM degradation by sunlight for a river reach, expressed as a function of light attenuation and water residence times.
Biogeosciences Discuss., 12, 9793-9838, doi:10.5194/bgd-12-9793-2015, 2015
Water quality, isoscapes and stoichioscapes of seagrasses indicate general P limitation and unique N cycling in shallow water benthos of Bermuda
Summary: The landscape-scale spatial pattern in the elemental and isotopic composition of organisms offers valuable information about the ecological processes operating across the landscape. When used in parallel, spatial patterns in stable isotopic composition (called isoscapes) and elemental stoichiometry (we propose the term "stoichioscapes") of seagrasses in Bermuda indicate nutrient sources and unique nitrogen cycling on this isolated oceanic platform.
Biogeosciences Discuss., 12, 9751-9791, doi:10.5194/bgd-12-9751-2015, 2015
Microbial carbon recycling: an underestimated process controlling soil carbon dynamics
Biogeosciences Discuss., 12, 9729-9750, doi:10.5194/bgd-12-9729-2015, 2015
Future fisheries yield in shelf waters: a model study into effects of a warmer and more acidic marine environment
Summary: - Effects of ocean acidification in shelf waters on fish yield can be of the same order of magnitude as climatic impacts. - Local differences in response within one shelf sea due to different governing hydrodynamic regimes and variation in importance of benthic food web. - Future fish yields in the North Sea: seasonally stratified areas show increased yield, transitional waters show decreased yield and permanently mixed waters show increased yield moderated by acidification impacts.
Biogeosciences Discuss., 12, 9695-9727, doi:10.5194/bgd-12-9695-2015, 2015
Challenges in modelling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman
Summary: Interannual variability of phytoplankton blooms in northwestern Arabian Sea and Gulf of Oman is examined. Interannual variability of the wintertime bloom is dominated by cyclonic eddies which vary in location from one year to another. We suggest that for the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies.
Biogeosciences Discuss., 12, 9651-9693, doi:10.5194/bgd-12-9651-2015, 2015
Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers
Summary: This simulation study found that dry legacy imposed positive impacts on net ecosystem production (NEP) whereas wet legacy had negative impacts on NEP, indicating that dry legacy can fostering more C sequestration and wet legacy more C release. The carryover of soil nitrogen was mainly responsible for the gross ecosystem production (GEP) responses while the carryovers of plant biomass, litter and soil organic matter were mainly responsible for the ecosystem respiration (Re) responses.
Biogeosciences Discuss., 12, 9613-9650, doi:10.5194/bgd-12-9613-2015, 2015
The relative contributions of forest growth and areal expansion to forest biomass carbon sinks in China
Summary: Our findings suggested that the mechanisms underlying the C sinks for natural and planted forests of China differed markedly with various effects from areal expansion and increase in carbon density. The increasing trend in the relative contribution of forest growth to C sinks for planted forests highlight that afforestation can continue to increase the C sink of China's forests in the future subject to persistently-increasing forest growth after establishment of plantation.
Biogeosciences Discuss., 12, 9587-9612, doi:10.5194/bgd-12-9587-2015, 2015
Annual cycle of volatile organic compound exchange between a boreal pine forest and the atmosphere
Biogeosciences Discuss., 12, 9543-9586, doi:10.5194/bgd-12-9543-2015, 2015
Ecosystem model-based approach for modelling the dynamics of 137Cs transfer to marine plankton populations: application to the western North Pacific Ocean after the Fukushima nuclear power plant accident
Biogeosciences Discuss., 12, 9497-9541, doi:10.5194/bgd-12-9497-2015, 2015
Micro-topographic variation in soil respiration and its controlling factors vary with plant phenophases in a desert-shrub ecosystem
Biogeosciences Discuss., 12, 9465-9495, doi:10.5194/bgd-12-9465-2015, 2015
Technical Note: Towards resolving in situ, centimeter-scale location and timing of biomineralization in calcareous meiobenthos – the Calcein-Osmotic pump method
Biogeosciences Discuss., 12, 9443-9463, doi:10.5194/bgd-12-9443-2015, 2015
An objective prior error quantification for regional atmospheric inverse applications
Biogeosciences Discuss., 12, 9393-9441, doi:10.5194/bgd-12-9393-2015, 2015
Insights into the transfer of silicon isotopes into the sediment record
Biogeosciences Discuss., 12, 9369-9391, doi:10.5194/bgd-12-9369-2015, 2015
The ability of atmospheric data to resolve discrepancies in wetland methane estimates over North America
Summary: We use atmospheric data from the US and Canada to examine seven wetland methane flux estimates. Our analysis indicates a wetland source that is smaller with a broader seasonal cycle than in existing estimates. Furthermore, we estimate the largest fluxes over the Hudson Bay Lowland, a spatial distribution that differs from commonly-used remote sensing estimates of wetland location.
Biogeosciences Discuss., 12, 9341-9368, doi:10.5194/bgd-12-9341-2015, 2015
Impact of forest harvesting on water quality and fluorescence characteristics of dissolved organic matter in Eastern Canadian Boreal Shield lakes
Summary: In this study, we showed that logging activities have a short-term impact (one year after the perturbation) on water quality in boreal Eastern Canadian Shield lakes. However, this effect seems to mitigate two years after the perturbation. Further, the analysis of the absorbance and fluorescence data showed that while DOC concentrations did significantly increase in perturbed lakes, the DOM quality did not measurably change.
Biogeosciences Discuss., 12, 9307-9339, doi:10.5194/bgd-12-9307-2015, 2015
C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean
Biogeosciences Discuss., 12, 9275-9305, doi:10.5194/bgd-12-9275-2015, 2015
Influence of mesoscale eddies on the distribution of nitrous oxide in the eastern tropical South Pacific
Summary: We present the first measurements of N2O across three mesoscale eddies in the eastern tropical South Pacific. Eddie's vertical structure, offshore transport, properties at the time of formation and increased primary production at the near-surface, determined the N2O distribution. Substantial depletion of N2O within the core of anticyclonic eddies suggests that although these are transient features, eddy-driven increase in N-loss processes in the Peruvian oxygen minimum zone can be significant.
Biogeosciences Discuss., 12, 9243-9273, doi:10.5194/bgd-12-9243-2015, 2015
Transpiration in an oil palm landscape: effects of palm age
Summary: The study provides first insights into hydrological consequences of the continuing oil palm expansion in the tropics. Stand transpiration rates of some studied oil palm stands compared to or even exceed values reported for tropical forests, indicating a high water use of oil palms under certain conditions. Oil palm dominated landscapes show some spatial variations in (evapo)transpiration rates, e.g. due to varying age, but the temporal variability of oil palm transpiration is rather low.
Biogeosciences Discuss., 12, 9209-9242, doi:10.5194/bgd-12-9209-2015, 2015
Soil fertility controls soil–atmosphere carbon dioxide and methane fluxes in a tropical landscape converted from lowland forest to rubber and oil palm plantations
Summary: We found that in Indonesia, oil palm displayed reduced soil CO2 fluxes compared to forest and rubber plantations, which was mainly caused by reduced litter input. Furthermore, we measured reduced soil CH4 uptake in oil palm and rubber plantations compared to forest which was due to a decrease in soil N availability in the converted land uses. Our study shows for the first time that differences in soil fertility control soil-atmosphere exchange of CO2 and CH4 in a tropical landscape.
Biogeosciences Discuss., 12, 9163-9207, doi:10.5194/bgd-12-9163-2015, 2015
Environmental controls on the greening of terrestrial vegetation across northern Eurasia
Summary: The vegetation of northern Eurasia has been observed to be greening over the last few decades and we assess how changes in temperature, precipitation, cloudiness and forest fires have affected the photosynthetic activity of the region. We find that while in most parts of northern Eurasia, increasing temperatures have lead to the increase in photosynthesis, in the south-western region, warming has lead to a decrease in the photosynthetic activity implying a comparatively higher drought stress.
Biogeosciences Discuss., 12, 9121-9162, doi:10.5194/bgd-12-9121-2015, 2015
Global assessment of Vegetation Index and Phenology Lab (VIP) and Global Inventory Modeling and Mapping Studies (GIMMS) version 3 products
Summary: We compared two new Earth observation based long-term global vegetation index products used in global change research (Global Inventory Modeling and Mapping Studies and Vegetation Index & Phenology Lab- VIP version 3). The two products showed a high level of consistency throughout the primary growing season and were less consistent during green-up and brown-down, which impacted trends in phenology. VIP was generally higher and more variable, which led to poorer correlations with in situ data.
Biogeosciences Discuss., 12, 9081-9120, doi:10.5194/bgd-12-9081-2015, 2015
Diazotroph community succession during the VAHINE mesocosms experiment (New Caledonia Lagoon)
Summary: -Shift from diatom associated diazotrophs (DDAs) to unicellular cyanobacterial group C (UCYN-C) in response to DIP fertilization was captured in a large-scale mesocosm experiment in the Noumea Lagoon (NL), a low nutrient low chlorophyll coastal environment. -First report of in situ net growth and mortality rates for unicellular diazotrophs UCYN-A2, and UCYN-C. -First quantitative abundance data for diazotrophs in NL indicates that DDAs and UCYN-A1/A2 may be important N2 fixers in this region.
Biogeosciences Discuss., 12, 9043-9079, doi:10.5194/bgd-12-9043-2015, 2015
Map-based prediction of organic carbon in headwaters streams improved by downstream observations from the river outlet
Summary: In this study we test whether river outlet chemistry can be used as an additional source of information to improve the prediction of the total organic carbon (TOC) of headwaters, relative to models based on map information alone. Including river outlet TOC as a predictor in the models gave 5-15% lower prediction errors than using map information alone. Thus, data on water chemistry measured at river outlets offers information which can complement GIS-based modelling of headwaters chemistry.
Biogeosciences Discuss., 12, 9005-9041, doi:10.5194/bgd-12-9005-2015, 2015
The effect of warm-season precipitation on the diel cycle of the surface energy balance and carbon dioxide at a Colorado subalpine forest site
Summary: The effect of warm-season precipitation on environmental conditions and ecosystem-scale fluxes at a high-elevation subalpine forest site was investigated. As would be expected (based on the surface energy balance), precipitation caused an increase in latent heat flux (evapotranspiration) and a decrease in sensible heat flux. The evaporative component of evapotranspiration was, on average, estimated to be around 6% in dry conditions and 20% in wet conditions.
Biogeosciences Discuss., 12, 8939-9004, doi:10.5194/bgd-12-8939-2015, 2015
Reviews and synthesis: Carbon capture and storage monitoring – an integrated biological, biophysical and chemical approach
Summary: Here we review current knowledge about the impact of CO2 leaks from marine carbon capture storage sites, and use a recent case study to assess current monitoring techniques. We integrate aspects of microbiology, geophysics, chemistry and bioinformatics to suggest a future integrative monitoring technique, using metagenomics, to prevent large-scale leakages and associated consequences. This novel approach is generic and can be adapted to other systems of interest for environmental monitoring.
Biogeosciences Discuss., 12, 8909-8937, doi:10.5194/bgd-12-8909-2015, 2015
The first records of deep-sea fauna – a correction and discussion
Summary: The recovery of a basket star in 1818 from deep waters of Baffin Bay is often cited as the first organism that was brought up from the deep sea. Yet recoveries of stalked crinoids from the Caribbean and catches of several bathyal fishes occurred decades earlier. Yet these accidental catches remained largely neglected during the 19th and 20th century because the bathyal nature of these animals was not recognized.
Biogeosciences Discuss., 12, 8883-8907, doi:10.5194/bgd-12-8883-2015, 2015
Fossil invertebrates records in cave sediments and paleoenvironmental assessments: a study of four cave sites from Romanian Carpathians
Biogeosciences Discuss., 12, 8849-8881, doi:10.5194/bgd-12-8849-2015, 2015
Recycling vs. stabilisation of soil sugars – a long-term laboratory incubation experiment
Biogeosciences Discuss., 12, 8819-8847, doi:10.5194/bgd-12-8819-2015, 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
Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin
Biogeosciences Discuss., 12, 8747-8787, doi:10.5194/bgd-12-8747-2015, 2015
Response of respiration and nutrient availability to drying and rewetting in soil from a semi-arid woodland depends on vegetation patch and a recent wild fire
Biogeosciences Discuss., 12, 8723-8745, doi:10.5194/bgd-12-8723-2015, 2015
Drivers of summer oxygen depletion in the central North Sea
Summary: In stratified shelf seas, physical and biological conditions can lead to seasonal oxygen depletion when consumption exceeds supply. An ocean glider obtained a high resolution 3-day data set of biochemical and physical properties in the central North Sea. The data revealed very high oxygen consumption rates, far exceeding previously reported rates. An consumption/supply oxygen budget indicates a localised or short lived resuspension event causing rapid remineralisation of benthic organic matter.
Biogeosciences Discuss., 12, 8691-8722, doi:10.5194/bgd-12-8691-2015, 2015
Latitudinal and temporal distributions of diatom populations in the pelagic waters of the Subantarctic and Polar Frontal Zones of the Southern Ocean and their role in the biological pump
Summary: Diatom and major components of the flux collected by two sediment traps in Subantarctic and Polar Frontal Zones were studied. Despite significant differences in the composition and magnitude of the flux, POC flux was similar between sites. The development of a group of bloom-forming diatoms during summer led to the formation of aggregates and enhanced POC export. Our results suggest that high biogenic silica accumulation rates should be interpreted as a proxy for iron-limited diatom assemblages.
Biogeosciences Discuss., 12, 8615-8690, doi:10.5194/bgd-12-8615-2015, 2015
Integrated radar and lidar analysis reveals extensive loss of remaining intact forest on Sumatra 2007–2010
Summary: We integrated satellite Synthetic Aperture Radar (SAR), lidar and forest plot data to calculate the amount and loss of above ground biomass in remaining tall natural forests in a section of Sumatra, with quantified uncertainties. We estimate very high deforestation rates of 3.8% yr-1, and the loss of 11.3% remaining forest biomass in only three years. L-band SAR is valuable for penetrating cloud for deforestation analyses, and for reliably estimating the carbon emissions from land use change.
Biogeosciences Discuss., 12, 8573-8614, doi:10.5194/bgd-12-8573-2015, 2015
Comparative study of vent and seep macrofaunal communities in the Guaymas Basin
Summary: The absence of biogeographic barrier between seep and vent ecosystems in the Guaymas basin offers the opportunity to assess the role of environmental conditions on the distribution of macrofaunal communities. Our results showed that community structure was primarily shaped by common abiotic factors. In addition, a high number of common species were shared, suggesting frequent connections between the two ecosystems. Overall, this study supports the hypothesis of a continuum among vents and seeps.
Biogeosciences Discuss., 12, 8497-8571, doi:10.5194/bgd-12-8497-2015, 2015
Does Juncus effusus enhance methane emissions from grazed pastures on peat?
Biogeosciences Discuss., 12, 8467-8495, doi:10.5194/bgd-12-8467-2015, 2015
Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation
Summary: We calculate the carbonate saturation state of surface water from the Ross Sea and along a transect between the Ross Sea and southern Chile using ~ 1700 total alkalinity measurements. Our results suggest that variability in surface carbonate saturation state is driven by biological productivity. We argue that in the Ross Sea the aragonite saturation state of surface water during the early spring never falls below 1.2.
Biogeosciences Discuss., 12, 8429-8465, doi:10.5194/bgd-12-8429-2015, 2015
Technical Note: Time lag correction of aquatic eddy covariance data measured in the presence of waves
Summary: Extracting benthic oxygen fluxes from eddy covariance data measured in the presence of surface gravity waves requires careful consideration of the temporal alignment of the vertical velocity and the oxygen concentration. We show that substantial errors in flux estimates can arise if these two variables are not aligned correctly in time, and propose a new correction for this problem.
Biogeosciences Discuss., 12, 8395-8427, doi:10.5194/bgd-12-8395-2015, 2015
Biodegradability of dissolved organic carbon in permafrost soils and waterways: a meta-analysis
Summary: We found that dissolved organic carbon (DOC) in arctic soils and aquatic systems is increasingly degradable with increasing permafrost extent. Also, DOC seems less degradable when moving down the fluvial network in continuous permafrost regions, i.e. from streams to large rivers, suggesting that highly bioavailable DOC is lost in headwater streams. We also recommend a standardized DOC incubation protocol to facilitate future comparison on processing and transport of DOC in a changing Arctic.
Biogeosciences Discuss., 12, 8353-8393, doi:10.5194/bgd-12-8353-2015, 2015
Ideas and perspectives: use of tree-ring width as an indicator of tree growth
Summary: By coring trees, studies can reconstruct growth over the lifespan of a tree. This provides unparalleled sampling of temporal variation of growth. However, many studies focus on the variation of annual ring width. With increasing prevalence of such studies in global change science, we caution that ring width is not directly comparable with primary productivity of the tree and advocate a straightforward solution to facilitate comparison between studies.
Biogeosciences Discuss., 12, 8341-8352, doi:10.5194/bgd-12-8341-2015, 2015
Fate of peat-derived carbon and associated CO2 and CO emissions from two Southeast Asian estuaries
Summary: We studied organic carbon and the dissolved greenhouse gases carbon dioxide (CO2) and carbon monoxide (CO) in two estuaries in Sarawak, Malaysia, whose coast is covered by carbon-rich peatlands. The estuaries received terrestrial organic carbon from peat-draining tributaries. A large fraction was transformed to CO2 and a minor fraction to CO. Both gases were released to the atmosphere. This shows how these estuaries function as efficient filters between land and ocean in this important region.
Biogeosciences Discuss., 12, 8299-8340, doi:10.5194/bgd-12-8299-2015, 2015
Historical reconstruction of ocean acidification in the Australian region
Summary: We reconstruct the observed variability and mean state in pH and aragonite saturation state around Australia at high spatial resolution and reconstruct the changes that have occurred in the Australian region over the last 140 years. We find that large changes in aragonite saturation state and pH have very different spatial patterns, which suggests that the biological responses to ocean acidification are likely to be non-uniform and dependent on the relative sensitivity of organisms to change.
Biogeosciences Discuss., 12, 8265-8297, doi:10.5194/bgd-12-8265-2015, 2015
Relationships between burned area, forest cover loss and land use change in the Brazilian Amazon based on satellite data
Biogeosciences Discuss., 12, 8235-8263, doi:10.5194/bgd-12-8235-2015, 2015
Biologically labile photoproducts from riverine non-labile dissolved organic carbon in the coastal waters
Summary: Irradiations of filtered water samples from ten major rivers stimulated bacterial production and respiration. The stimulus depended on photobleaching of chromophoric dissolved organic matter (CDOM). Assuming complete photobleaching of CDOM in the global coastal ocean, sunlight-induced photochemical reactions transform >15% (>38 Mt yr-1) of riverine dissolved organic carbon flux into biologically labile photoproducts, which are consumed by bacteria with 13% growth efficiency.
Biogeosciences Discuss., 12, 8199-8234, doi:10.5194/bgd-12-8199-2015, 2015
A latitudinally-banded phytoplankton response to 21st century climate change in the Southern Ocean across the CMIP5 model suite
Summary: Using the latest earth system models, we find that shifts in nutrient and light availability with future climate warming drive latitudinally-banded changes in Southern Ocean phytoplankton distributions, which have the potential to significantly alter nutrient cycling as well as higher trophic level productivity throughout the global ocean. Spatial patterns in the modeled mechanisms driving these predicted phytoplankton trends qualitatively agree with recent observations.
Biogeosciences Discuss., 12, 8157-8197, doi:10.5194/bgd-12-8157-2015, 2015
A novel paleo-bleaching proxy using boron isotopes and high-resolution laser ablation to reconstruct coral bleaching events
Summary: This paper offers a new methodology to study paleo-coral bleaching events using high-resolution femtosecond Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry. Coral bleaching records only go back several decades, but this new proxy allows the study of bleaching events that occurred tens of thousands of years ago. Unlike other methods, the high-resolution of the method can detect bleaching events that occur over very short time periods, just a few weeks.
Biogeosciences Discuss., 12, 8131-8155, doi:10.5194/bgd-12-8131-2015, 2015
The influence of C3 and C4 vegetation on soil organic matter dynamics in contrasting semi-natural tropical ecosystems
Summary: We demonstrate and explain differential patterns in SOM dynamics in C3/C4 mixed ecosystems at various spatial scales across contrasting climate and soils. This study shows that the interdependence between biotic and abiotic factors ultimately determine whether SOM dynamics of C3- and C4-derived vegetation are at variance in ecosystems where both vegetation types coexist. The results also highlight the far-reaching implications that vegetation thickening may have for the stability of deep SOM
Biogeosciences Discuss., 12, 8085-8130, doi:10.5194/bgd-12-8085-2015, 2015
Greenhouse gas balance of cropland conversion to bioenergy poplar short rotation coppice
Summary: The suitability of a land conversion from cropland to short rotation coppice (SRC) of poplar in Central Italy was investigated comparing the respective GHG budgets, including biogenic and anthropogenic CO2, CH4 and N2O fluxes, change in soil C stocks and effects of biomass use. Land conversion was suitable from a GHG perspective, saving 2358 ± 835 gCO2eq m-2, as C exports in the cropland compensated all the C taken up by plants, while in the SRC only in part. Soil non-CO2 fluxes were negligible
Biogeosciences Discuss., 12, 8035-8084, doi:10.5194/bgd-12-8035-2015, 2015
Interpreting canopy development and physiology using the EUROPhen camera network at flux sites
Summary: The timing of plant development stages and their response to climate and management were investigated using a network of digital cameras installed across different European ecosystems. Using the relative red, green and blue content of images we showed that the green signal could be used to estimate the length of the growing season in broadleaf forests. We also developed a model that predicted well the seasonal variations of camera RGB signals and how they relate to leaf pigment content and area.
Biogeosciences Discuss., 12, 7979-8034, doi:10.5194/bgd-12-7979-2015, 2015
Edaphic, structural and physiological contrasts across Amazon Basin forest-savanna ecotones suggest a role for potassium as a key modulator of tropical woody vegetation structure and function
Summary: Across tropical South America, forest soils are typically of a higher cation status than their savanna equivalents with soil exchangeable potassium a key soil nutrient differentiating these two vegetation types. Differences in soil water storage capacity are also important – interacting with both potassium availability and precipitation regimes in a relatively complex manner.
Biogeosciences Discuss., 12, 7879-7977, doi:10.5194/bgd-12-7879-2015, 2015
Calculating the global contribution of coralline algae to carbon burial
Summary: The ongoing increase in anthropogenic carbon dioxide (CO2) emissions is changing the marine environment. Reduction of CO2 to a sustainable level is required to avoid further change. In this manuscript, the carbon storage potential of coralline algae (CA) and their deposits is accessed. We show that CA represent an as yet unquantified significant carbon repository, storing similar amounts of carbon to seagrasses and mangroves. Critically, stored carbon will be stable at geological time scale.
Biogeosciences Discuss., 12, 7845-7877, doi:10.5194/bgd-12-7845-2015, 2015
Human land uses enhance sediment denitrification and N2O production in Yangtze lakes primarily by influencing lake water quality
Biogeosciences Discuss., 12, 7815-7844, doi:10.5194/bgd-12-7815-2015, 2015
Tree water relations trigger monoterpene emissions from Scots pine stem during spring recovery
Summary: Especially boreal coniferous trees emit plenty of volatile monoterpenes into the atmosphere. At our measurement site in Finland, we found a spring-time relation between the high monoterpene emission from Scots pine stem and tree water relations. Hence, we suggest that the transient monoterpene burst was a consequence of the spring recovery of the stem and that the dominant processes and environmental drivers triggering the monoterpene emissions are different between pine stems and foliage.
Biogeosciences Discuss., 12, 7783-7814, doi:10.5194/bgd-12-7783-2015, 2015
Wind-driven interannual variability of sea ice algal production over the western Arctic Chukchi Borderland
Summary: We have summarized our findings on seasonal and interannual variability of sea ice algal production and biomass over the western Arctic Chukchi Boderland using a pan-Arctic sea ice-ocean modeling approach. In particular, we focused on the relationship with wind pattern. Coupling physical and biogeochemical analyses would provide originality of our study.
Biogeosciences Discuss., 12, 7739-7781, doi:10.5194/bgd-12-7739-2015, 2015
Iron encrustations on filamentous algae colonized by Gallionella-related bacteria in a metal-polluted freshwater stream
Summary: We studied filamentous macroscopic algae growing in metal-rich stream water that leaked out in a former uranium-mining district. These algae were encrusted with Fe-deposits that were associated with microbes, mainly Gallionella-related Fe-oxidizing bacteria, and extracellular polymeric substances. Algae with lower number of chloroplasts often exhibited discontinuous series of precipitates likely due to the intercalary growth of algal filaments which allowed them to avoid fatal encrustation.
Biogeosciences Discuss., 12, 7705-7737, doi:10.5194/bgd-12-7705-2015, 2015
Age depth-model for the past 630 ka in Lake Ohrid (Macedonia/Albania) based on cyclostratigraphic analysis of downhole gamma ray data
Biogeosciences Discuss., 12, 7671-7703, doi:10.5194/bgd-12-7671-2015, 2015
Seasonal hydrology drives rapid shifts in the flux and composition of dissolved and particulate organic carbon and mercury in the Fraser River, Canada
Summary: This study presents seasonal cycles of organic carbon and mercury concentrations and organic matter composition in the Fraser River. Dissolved organic matter patterns are linked to flushing of shallow soil layers during spring snowmelt and fall rain events. Hg export does not indicate contamination from pollution or legacy gold mining. Organic carbon export--as both area-normalized yield and the proportion of basin primary productivity--in the Fraser is typical of large rivers globally.
Biogeosciences Discuss., 12, 7613-7669, doi:10.5194/bgd-12-7613-2015, 2015
Radiocarbon isotopic evidence for assimilation of atmospheric CO2 by the seagrass Zostera marina
Summary: Our empirical study first shows the quantitative evidence of assimilating atmospheric modern CO2 by the seagrass Zostera marina, by analyzing the radiocarbon isotope concentrations (Δ14C) of both the seagrass and two carbon sources in a brackish lagoon. CO2 exchange between the air and water would occur at the very thin film of water over the air-exposed seagrass leaves. Our finding offers better understanding of the role of seagrass meadows in global coastal carbon dynamics.
Biogeosciences Discuss., 12, 7599-7611, doi:10.5194/bgd-12-7599-2015, 2015
Isotopically enriched ammonium shows high nitrogen turnover in the pile top zone of dairy manure compost
Summary: δ15N-NH4+-N of dairy manure compost piles was studied. Piles with bulking agent showed significantly higher value 17.7±1.3‰ than that of the piles without bulking agent (11.8±0.9‰) at the end of the process, reflecting significant higher nitrogen conversion and NH3 loss occurred in the pile with bulking agent. The pile top samples which showed very high NH4+-N concentrations with significantly enriched δ15N values (12.7-29.8‰) indicate extremely high nitrogen conversion occurred in this zone.
Biogeosciences Discuss., 12, 7577-7598, doi:10.5194/bgd-12-7577-2015, 2015
Parameterization of biogeochemical sediment–water fluxes using in-situ measurements and a steady-state diagenetic model
Summary: In low oxygen environments, the lack of oxygen influences sediment biogeochemistry and in turn sediment-water fluxes. These non-linear interactions are often missing from biogeochemical circulation models because sediment models are computationally expensive. A method for parameterizing realistic sediment-water fluxes is presented and applied to the Mississippi River Dead Zone where high primary production, stimulated by excess nutrient loads, promotes low bottom water conditions in summer.
Biogeosciences Discuss., 12, 7537-7575, doi:10.5194/bgd-12-7537-2015, 2015
Derivation of greenhouse gas emission factors for peatlands managed for extraction in the Republic of Ireland and the UK
Summary: We quantified carbon dioxide emissions from drained peat extraction sites in the Republic of Ireland and the United Kingdom, and also measured a range of greenhouse gases that are released to the atmosphere with the burning of peat. Our derived carbon dioxide emission factors were considerably lower than those derived by the IPCC, which has major implications for National Inventory reporting under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol.
Biogeosciences Discuss., 12, 7491-7535, doi:10.5194/bgd-12-7491-2015, 2015
Detecting methane ebullition on thermokarst lake ice using high resolution optical aerial imagery
Summary: We used multi-temporal high-resolution aerial images of an Alaskan thermokarst lake acquired following freeze-up to map and characterize methane ebullition bubbles trapped in lake ice. We assessed their spatial pattern and also analyzed the spatio-temporal variability of seep occurrences. Our study helped to reveal the location and relative sizes of high- and low-flux seepage zones within the lake. A large number of seeps demonstrated spatio-temporal stability over our two-year study period.
Biogeosciences Discuss., 12, 7449-7490, doi:10.5194/bgd-12-7449-2015, 2015
Salinization alters fluxes of bioreactive elements from streams and soils across land use
Biogeosciences Discuss., 12, 7411-7448, doi:10.5194/bgd-12-7411-2015, 2015
Air–sea CO2 fluxes and the controls on ocean surface pCO2 variability in coastal and open-ocean southwestern Atlantic Ocean: a modeling study
Summary: We investigate surface ocean pCO2 and air-sea CO2 fluxes climatological variability through biogeochemical modeling in the southwestern Atlantic Ocean. Surface ocean pCO2 spatio-temporal variability was found to be controlled mainly by temperature and Dissolved Inorganic Carbon (DIC). Biological production, physical transport and solubility are the main controlling processes. With different behaviors on subtropical and subantarctic open ocean, and on inner/outer continental shelves.
Biogeosciences Discuss., 12, 7369-7409, doi:10.5194/bgd-12-7369-2015, 2015
A comparison of benthic foraminiferal Mn/Ca and sedimentary Mn/Al as proxies of relative bottom water oxygenation in the low latitude NE Atlantic upwelling system
Summary: We highlight the proxy potential of foraminiferal Mn/Ca determined by Secondary Ion Mass Spectrometry and Flow-Through Inductively Coupled Plasma Optical Emission Spectroscopy for recording changes in bottom water oxygen conditions. Comparisons with Mn sediment bulk measurements from the same sediment core largely agree with the results. High foraminiferal Mn/Ca occurs in samples from times of high productivity export and corresponds with the benthic foraminiferal faunal composition.
Biogeosciences Discuss., 12, 7335-7367, doi:10.5194/bgd-12-7335-2015, 2015
Colored dissolved organic matter in shallow estuaries: the effect of source on quantification
Summary: Colored dissolved organic matter (CDOM) is a factor in determining penetration of light in estuaries. Important plant species growing in the beds of estuaries depend on such light penetration for survival. Previous studies have used CDOM fluorescence to approximate light absorption by CDOM but have found variable relationships between fluorescence and absorbance. This paper describes this variability in three east coast estuaries, and shows that this conversion is dependent on CDOM source.
Biogeosciences Discuss., 12, 7301-7333, doi:10.5194/bgd-12-7301-2015, 2015
Nitrogen cycling in shallow low oxygen coastal waters off Peru from nitrite and nitrate nitrogen and oxygen isotopes
Biogeosciences Discuss., 12, 7257-7299, doi:10.5194/bgd-12-7257-2015, 2015
Effects of nitrate and phosphate supply on chromophoric and fluorescent dissolved organic matter in the Eastern Tropical North Atlantic: a mesocosm study
Biogeosciences Discuss., 12, 7209-7255, doi:10.5194/bgd-12-7209-2015, 2015
Characterization of active and total fungal communities in the atmosphere over the Amazon rainforest
Biogeosciences Discuss., 12, 7177-7207, doi:10.5194/bgd-12-7177-2015, 2015
Including high frequency variability in coastal ocean acidification projections
Summary: In this manuscript, habitat-specific acidification projections are presented for four near-shore habitats in the Southern California Bight using high-temporal resolution pH sensor data: surf zone, kelp forest, canyon edge, and the shelf break. All habitats were within 5 km of one another, and exhibited unique, habitat-specific CO2 variability signatures and acidification trajectories, demonstrating the importance of making projections in the context of habitat-specific CO2 signatures.
Biogeosciences Discuss., 12, 7125-7176, doi:10.5194/bgd-12-7125-2015, 2015
Responses of leaf traits to climatic gradients: adaptive variation vs. compositional shifts
Summary: By analysing the quantitative leaf-traits along extensive temperature and moisture gradients with generalized linear models, we found that metabolism-related traits are universally acclimated to environmental conditions, rather than being fixed within plant functional types. The results strongly support a move towards Dynamic Global Vegetation Models in which continuous, adaptive trait variation provides the fundamental mechanism for changes in ecosystem properties along environmental gradients.
Biogeosciences Discuss., 12, 7093-7124, doi:10.5194/bgd-12-7093-2015, 2015
Impacts of climate and reclamation on temporal variations in CH4 emissions from different wetlands in China: from 1950 to 2010
Summary: Natural wetlands in China have experienced extensive conversion and climate warming, which makes the estimation of methane emission from wetlands highly uncertain. In this paper, we simulated an increase of 25.5% in national CH4 fluxes from 1950 to 2010, which was mainly induced by climate warming. Although climate warming has accelerated CH4 fluxes, the total amount of national CH4 emissions decreased by approximately 2.35 Tg (1.91－2.81 Tg), due to a large wetland loss of 17.0 million ha.
Biogeosciences Discuss., 12, 7055-7091, doi:10.5194/bgd-12-7055-2015, 2015
Methane distribution, flux, and budget in the East China Sea and Yellow Sea
Summary: Obvious seasonal variations of the distribution and emission of methane in the ECS and YS were reported based on data collected during five cruises in 2011. A box model was used to calculate the methane budget in the ECS, identify the main sources and sinks of dissolved methane in this area, and estimate the contribution of different sources to total methane quantitatively. It indicated that the most important source of methane in the ECS was in situ production in the water column.
Biogeosciences Discuss., 12, 7017-7053, doi:10.5194/bgd-12-7017-2015, 2015
Evaluating the Community Land Model in a pine stand with 13CO2 labeling and shading manipulations
Biogeosciences Discuss., 12, 6971-7015, doi:10.5194/bgd-12-6971-2015, 2015
Two decades of inorganic carbon dynamics along the Western Antarctic Peninsula
Summary: Evaluation of a unique 20 year long timeseries of inorganic carbon and nutrient observations from the Western Antarctic Peninsula region shows that summertime biological productivity and meltwater input drive a large range of surface aragonite saturation states from values < 1 (undersaturated) up to 3.9. pCO2 measurements from fall and spring indicate a statistically significant increasing trend of up to 23 μatm decade-1, pointing towards first signs of ocean acidification.
Biogeosciences Discuss., 12, 6929-6969, doi:10.5194/bgd-12-6929-2015, 2015
Effect of elevated CO2 on organic matter pools and fluxes in a summer, post spring-bloom Baltic Sea plankton community
Biogeosciences Discuss., 12, 6863-6927, doi:10.5194/bgd-12-6863-2015, 2015
Enhanced pH up-regulation enables the cold-water coral Lophelia pertusa to sustain growth in aragonite undersaturated conditions
Summary: We investigated the ability of cold-water corals to deal with changes in ocean pH. We uniquely combined morphological assessment with boron isotope analysis to determine if changes in growth are related to changes in control of calcification pH. We found that the cold-water coral Lophelia pertusa can maintain the skeletal morphology, growth patterns as well as internal calcification pH. This has important implications for their future occurrence and explains their cosmopolitan distribution.
Biogeosciences Discuss., 12, 6757-6781, doi:10.5194/bgd-12-6757-2015, 2015
Phytoplankton dynamics driven by vertical nutrient fluxes during the spring inter-monsoon period in the northeastern South China Sea
Summary: Phytoplankton patchiness in the northeastern SCS during May 2014 could be largely controlled by vertical nutrient fluxes including turbulent diffusion and curl-driven upwelling. There was an increasing turbulent diffusion but decreasing curl-driven upwelling from the coastal upwelling zones to the offshore pelagic zones. Elevated fluxes near Dongsha led to net growth of a diatom-rich community, whereas low fluxes near southwest Taiwan resulted in a decline of a picoplankton bloom.
Biogeosciences Discuss., 12, 6723-6755, doi:10.5194/bgd-12-6723-2015, 2015
Reconsidering the role of carbonate ion concentration in calcification by marine organisms
Summary: Calcification by marine organisms reacts to changing seawater carbonate chemistry but it is unclear which components of the carbonate system drive the observed response. This study uncovers proportionalities between different carbonate chemistry parameters. 1) These enable us to understand why calcification often correlates well with carbonate ion concentration. 2) They imply that net CaCO3 formation in high latitudes is not more vulnerable to ocean acidification than formation in low latitudes.
Biogeosciences Discuss., 12, 6689-6722, doi:10.5194/bgd-12-6689-2015, 2015
Oxygen minimum zones in the tropical Pacific across CMIP5 models: mean state differences and climate change trends
Summary: We analyze simulations of the Pacific Ocean oxygen minimum zones (OMZs) from 11 Earth System model contributions to the Coupled Model Intercomparison Project Phase 5, focusing on the mean state, climate change projections, and interannual variability. We analyze biases with respect to observations and consistency of results across simulations.
Biogeosciences Discuss., 12, 6525-6587, doi:10.5194/bgd-12-6525-2015, 2015
The Measuring Ammonia in Nature (MAN) network in the Netherlands
Biogeosciences Discuss., 12, 6115-6146, doi:10.5194/bgd-12-6115-2015, 2015
Comment on "Solute specific scaling of inorganic nitrogen and phosphorus uptake in streams" by Hall et al. (2013)
Biogeosciences Discuss., 12, 5991-6001, doi:10.5194/bgd-12-5991-2015, 2015
Quantifying the influence of CO2 seasonality on future ocean acidification
Summary: Our results show that accounting for oceanic CO2 seasonality is crucial to projecting the future onset of critical ocean acidification levels (i.e. aragonite under-saturation). In particular, seasonality will bring forward the initial onset of month-long under-saturation by a global average of 17 years. Importantly, wide-spread under-saturation is projected to occur once atmospheric CO2 reaches 486ppm in the North Pacific and 511ppm in the Southern Ocean, independent of emissions scenario.
Biogeosciences Discuss., 12, 5907-5940, doi:10.5194/bgd-12-5907-2015, 2015
Seasonal characterization of CDOM for lakes in semi-arid regions of Northeast China using excitation-emission matrices fluorescence and parallel factor analysis (EEM-PARAFAC)
Summary: Our results of this study show that 1) Two humic-like peaks C and two protein-like B and T peaks were identified using PARAFAC in CDOM for lakes in Northeast China; 2)The average fluorescence intensity of the four components differed with seasonal variation; 3) Components 1 and 2 exhibited strong linear correlation (R2=0.633); 4)There were significantly positive linear relationships between CDOM absorption coefficients and Fmax; 5)A significant relationship (R2=0.931) was found between salinity
Biogeosciences Discuss., 12, 5725-5756, doi:10.5194/bgd-12-5725-2015, 2015
Dynamics of air–sea CO2 fluxes in the North-West European Shelf based on Voluntary Observing Ship (VOS) and satellite observations
Biogeosciences Discuss., 12, 5641-5695, doi:10.5194/bgd-12-5641-2015, 2015
Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue
Summary: This manuscript covers the first measurements of CHBr3, CH2Br2 and CH3I from the equatorial Atlantic during the Cold Tongue season, identifying this region and season as a source for these compounds. For the first time, we calculated diapycnal fluxes, and showed that the fluxes from below the mixed layer to the surface are not sufficient to balance the mixed layer budget. Hence, we conclude that mixed layer production has to take place despite a pronounced sub-mixed-layer-maximum.
Biogeosciences Discuss., 12, 5559-5608, doi:10.5194/bgd-12-5559-2015, 2015
Mitigation of agriculture emissions in the tropics: comparing forest land-sparing options at the national level
Summary: Emission from agriculture-driven deforestation can be mitigated by reducing the expansion of agriculture into forests through intensification and utilizing non-forested land for agriculture. Climate smart agriculture can reduce emissions from existing agricultural land. Tropical countries which are priorities for action, can be identified by assessing the mitigation potential of these interventions, by assessing capacity for implementation and the risks associated with these approaches.
Biogeosciences Discuss., 12, 5435-5475, doi:10.5194/bgd-12-5435-2015, 2015
Quantifying wind and pressure effects on trace gas fluxes across the soil–atmosphere interface
Summary: One continuing, significant source of uncertainty in global climate predictions is the combined effect of wind and pressure on trace gas fluxes. We quantified the effects of wind speed and pressure on fluxes of CO2 and CH4 within three different ecosystems. Trace gas fluxes are positively correlated with both wind speed and pressure near the soil surface but we argue that wind speed is a better proxy for general use. These results have implications for a number of global feedback mechanisms.
Biogeosciences Discuss., 12, 4801-4832, doi:10.5194/bgd-12-4801-2015, 2015
Stable isotopes in barnacles as a tool to understand green sea turtle (Chelonia mydas) regional movement patterns
Summary: We report on the oxygen isotope signatures in green sea turtle (Chelonia mydas) barnacles (Platylepas sp.) to suggest likely regional movement patterns by mapping these onto a predictive oxygen isotope map of the Pacific. Discussing barnacle proxies potential relevance as an alternative tool with which to study green sea turtle migration, we find that these could complement traditional methods of studying connectivity between turtle populations and help inform more effective conservation policy.
Biogeosciences Discuss., 12, 4655-4669, doi:10.5194/bgd-12-4655-2015, 2015
Interdependencies between temperature and moisture sensitivities of CO2 emissions in European land ecosystems
Summary: Our experiments showed that in cold areas (e.g. northern latitudes or mountain areas) warming as well as rain events will have a larger impact on CO2 emissions. Increased moisture in dry areas or drying of wet areas will largely promote CO2 emissions. Irrigation of arable lands might have a higher impact on CO2 emissions in warmer regions in the South of Europe than in the North.
Biogeosciences Discuss., 12, 4433-4464, doi:10.5194/bgd-12-4433-2015, 2015
Stable isotope paleoclimatology of the earliest Eocene using kimberlite-hosted mummified wood from the Canadian Subarctic
Summary: The recent discovery of mummified wood (non-petrified) within kimberlite diamond mines in Northwest Territories, Canada, has prompted a paleoclimatic investigation of the time in which the trees grew - the earliest Eocene (ca. 53.3 Ma). Multiple proxy records derived from these samples suggest that during greenhouse climates of the Eocene, subarctic Canada was characterized by high temperatures (+16 C above modern), and multidecadal variability in cloudiness and temperature on 20-30 year cycles.
Biogeosciences Discuss., 11, 16269-16308, doi:10.5194/bgd-11-16269-2014, 2014
Environmental factors controlling lake diatom communities: a meta-analysis of published data
Summary: I re-analyze information published during the last decades concerning the effect of different environmental predictors on the structure of benthic diatom communities in world lakes, providing a scientific basis for the implementation of new paleoenvironmental inference models. I consider highly relevant the publication of this article in a widely known journal, provided the noticeable demand on paleolimnological meta-studies supporting the use of such biological proxies at a pancontinental scale
Biogeosciences Discuss., 11, 15889-15909, doi:10.5194/bgd-11-15889-2014, 2014