Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment
Summary: This research is directly relevant to the emerging field of blue carbon research, which seeks to determine the carbon sequestration capacity of coastal habitats. Seagrasses are highly productive, and have a particularly large storage capacity, relative to area. Our study detected relatively high carbon content in the soils, indicating that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.
Biogeosciences Discuss., 12, 16285-16312, doi:10.5194/bgd-12-16285-2015, 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
Effects of management thinning on CO2 exchange by a plantation oak woodland in south-eastern England
Summary: We measured the exchange of carbon between the atmosphere and a commercially managed oak plantation in the south-east of England for several years before and after a management thinning took place. We also measured changes in the structure of the forest canopy using aerial light detection and ranging (LiDAR). Whilst management thinning had a large discernable effect on the canopy structure, for example creating more gaps, the effects of thinning on the carbon balance were not as evident.
Biogeosciences Discuss., 12, 16197-16232, doi:10.5194/bgd-12-16197-2015, 2015
The nature of organic carbon in density-fractionated sediments in the Sacramento-San Joaquin River Delta (California)
Summary: Bed sediments from the Sacramento-San Joaquin River Delta (CA) were fractionated according to density and analyzed for sediment mass distribution, elemental (C and N) composition, mineral surface area, and stable carbon and radiocarbon isotope compositions of organic carbon (OC) and fatty acids to evaluate the nature of organic carbon in river sediments. These data demonstrate the complex source and age distributions within river sediments.
Biogeosciences Discuss., 12, 16159-16196, doi:10.5194/bgd-12-16159-2015, 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
Differential resilience of ancient sister lakes Ohrid and Prespa to environmental disturbances during the Late Pleistocene
Biogeosciences Discuss., 12, 16049-16079, doi:10.5194/bgd-12-16049-2015, 2015
Technical Note: Semi-rigid chambers for methane gas flux measurements on tree-stems
Summary: There is increasing interest in measuring methane emissions from tree stems in a wide range of ecosystems. This is commonly done with bulky closed chambers, which limit measurement to a very narrow range of tree stem sizes and shapes. We designed, described and tested new semi-rigid stem-flux chambers with decisive advantages (reduced permeability, fast deployment, adapted headspace volume, easy to carry in multiple sizes, extremely light and economical) ideal for use in remote ecosystems.
Biogeosciences Discuss., 12, 16019-16048, doi:10.5194/bgd-12-16019-2015, 2015
Estimate of changes in agricultural terrestrial nitrogen pathways and ammonia emissions from 1850 to present in the Community Earth System Model
Summary: Future increases in reactive nitrogen applied to the land surface for agricultural purposes is predicted. However, the climate dependence of the subsequent fate of this nitrogen has not been evaluated; it is expected to be significant, however. Here we describe, analyze and evaluate a mechanistic parameterization of the climate dependence of the predominant loss pathways of reactive nitrogen applied to the land surface. The parameterization is suitable for use within a global terrestrial model.
Biogeosciences Discuss., 12, 15947-16018, doi:10.5194/bgd-12-15947-2015, 2015
Comparing solubility algorithms of greenhouse gases in Earth-System modelling
Biogeosciences Discuss., 12, 15925-15945, doi:10.5194/bgd-12-15925-2015, 2015
Improving estimations of greenhouse gas transfer velocities by atmosphere–ocean couplers in Earth-System and regional models
Biogeosciences Discuss., 12, 15901-15924, doi:10.5194/bgd-12-15901-2015, 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
Vanishing coccolith vital effects with alleviated CO2 limitation
Biogeosciences Discuss., 12, 15835-15866, doi:10.5194/bgd-12-15835-2015, 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
Carbon dynamics and changing winter conditions: a review of current understanding and future research directions
Biogeosciences Discuss., 12, 15763-15808, doi:10.5194/bgd-12-15763-2015, 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
Particulate organic matter composition and organic carbon flux in Arctic valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden
Summary: Svalbard archipelago have lots of valley glaciers, and its position in organic carbon flux to ocean remains unclear. In this manuscript, we found that these valley glaciers have a much higher area-weighted organic carbon flux, relative to Greenland ice sheet, and is comparble to other valley glaciers like those in alaska region.
Biogeosciences Discuss., 12, 15655-15685, doi:10.5194/bgd-12-15655-2015, 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
Increasing P-stress and viral infection impact lipid remodeling of the picophytoplankter Micromonas pusilla
Biogeosciences Discuss., 12, 15583-15610, doi:10.5194/bgd-12-15583-2015, 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
Pollen-based paleoenvironmental and paleoclimatic change at Lake Ohrid (SE Europe) during the past 500 ka
Summary: Lake Ohrid (FYROM/Albania) is the deepest, the largest and the oldest lake in Europe. To understand the climatic and environmental evolution of its area a palynological study was undertaken for the last 500 ka. We found a correspondence between forested/non-forested periods and glacial/interglacial cycles of marine isotope stratigraphy. Our record shows a progressive change from cooler and wetter to warmer and dryer interglacial conditions. This shift is visible also in glacial vegetation.
Biogeosciences Discuss., 12, 15461-15493, doi:10.5194/bgd-12-15461-2015, 2015
First tephrostratigraphic results of the DEEP site record from Lake Ohrid, Macedonia
Biogeosciences Discuss., 12, 15411-15460, doi:10.5194/bgd-12-15411-2015, 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
Climate impacts on multidecadal pCO2 variability in the North Atlantic: 1948–2009
Summary: Natural variability of the North Atlantic carbon cycle is modeled for 1948-2009. The dominant mode of surface ocean CO2 variability is associated with sea surface temperature (SST) variability composed of (a) the Atlantic Multidecadal Oscillation (AMO) and (b) a positive SST trend. In the subpolar gyre, positive AMO is associated with reduced vertical mixing that lowers pCO2. In the subtropical gyre, AMO-associated warming increases pCO2. Since 1980, the SST trend has amplified AMO impacts.
Biogeosciences Discuss., 12, 15223-15244, doi:10.5194/bgd-12-15223-2015, 2015
Fire vs. fossil fuel: all CO2 emissions are not created equal
Summary: We simulated both fire pulses and stable fire regimes, and found the resulting climatic impacts to be irreconcilable with equivalent amounts of CO2 emissions from produced by fossil fuel combustion. Consequently, side-by-side comparisons of fire and fossil fuel CO2 emissions—implicitly implying that they have similar effects—should be avoided. Our study calls for the explicit representation of fire in climate models in order to improve our understanding of its impacts in the Earth system.
Biogeosciences Discuss., 12, 15185-15222, doi:10.5194/bgd-12-15185-2015, 2015
Environmental controls on leaf wax δD ratios in surface peats across the monsoonal region of China
Biogeosciences Discuss., 12, 15157-15184, doi:10.5194/bgd-12-15157-2015, 2015
Sedimentological processes and environmental variability at Lake Ohrid (Macedonia, Albania) between 640 ka and present day
Biogeosciences Discuss., 12, 15111-15156, doi:10.5194/bgd-12-15111-2015, 2015
The 2009–2010 step in atmospheric CO2 inter-hemispheric difference
Summary: A step in the annual average CO2 difference between Mauna Loa and the Southern Hemisphere of 0.8ppm in 2009/2010 has no precedence in 50 years. Variations in inter-hemispheric exchange coincide with the step, the subsequent 5 year north-south CO2 stability, and historic differences. This behaviour provides a critical test for studies that employ atmospheric transport models to interpret global carbon budgets and inform management of anthropogenic emissions.
Biogeosciences Discuss., 12, 15087-15109, doi:10.5194/bgd-12-15087-2015, 2015
Ecosystem regimes and responses in a coupled ancient lake system from MIS 5b to present: the diatom record of lakes Ohrid and Prespa
Biogeosciences Discuss., 12, 15051-15086, doi:10.5194/bgd-12-15051-2015, 2015
Climate, CO2, and demographic impacts on global wildfire emissions
Summary: Wildfires are the largest contributor to atmospheric pollution from all fires globally, with major consequences for health and air quality. This study examines the main contributing factors governing wildfire emissions during the 20th and 21st centuries using simulations with climate and ecosystem models. Contrary to common perception, climate change is only one of several important factors, but population change, urbanization and changing atmospheric CO2 levels are at least equally important.
Biogeosciences Discuss., 12, 15011-15050, doi:10.5194/bgd-12-15011-2015, 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
Mussel shells of Mytilus edulis as bioarchives of the rare earth elements and yttrium distribution in seawater and the potential impact of pH and temperature on the partitioning behaviour
Summary: Our study demonstrates that Rare Earth elements and Yttrium (REY) accumulating in mussel shells emerge as potential proxies for environmental changes. Focusing on pH and temperature variation effects on the distribution of REY in seawater, we show that shells incorporate the free REY3+ species,and decreasing pH leads to increased REY concentrations while rising temperatures impact the REY distribution pattern with minor effects on the absolute REY concentrations in shells.
Biogeosciences Discuss., 12, 14911-14939, doi:10.5194/bgd-12-14911-2015, 2015
Microbial methanogenesis in the sulfate-reducing zone of surface sediments traversing the Peruvian margin
Summary: The concurrence of methanogenesis and sulfate reduction was investigated in surface sediments (0-25 cmbsf) traversing the Peruvian margin. Surface methanogenesis was mainly based on non-competitive substrates to avoid competition with sulfate reducers. Accordingly, surface methanogenesis was mainly controlled by the availability of labile organic matter. The high relevance of surface methanogenesis especially on the shelf indicates its underestimated role within benthic methane budgeting.
Biogeosciences Discuss., 12, 14869-14910, doi:10.5194/bgd-12-14869-2015, 2015
How past fire disturbances have contributed to the current carbon balance of boreal ecosystems?
Summary: Pan-boreal biome (>N45°) is currently removing CO2 from the atmosphere (i.e., a carbon sink). Fires can alter this carbon balance because they release CO2 to the atmosphere but also initiate a long-term carbon sink during post-fire vegetation recovery. We found that historical fires of 1850-2009 have a small net sink contribution (~6%) to the 2000-2009 regional carbon sink, which is a balance between immediate source effect of fires in 2000-2009 and sink effects of those in 1850-1999.
Biogeosciences Discuss., 12, 14833-14867, doi:10.5194/bgd-12-14833-2015, 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
Biogeochemical and suspended sediment responses to permafrost degradation in stream banks in Taylor Valley, Antarctica
Summary: The landscape of the McMurdo Dry Valleys, Antarctica has been considered quite stable. In 2012, we discovered extensive permafrost degradation along several km of Crescent Stream. Here we document the responses to water quality, specifically changes to dissolved major ion and suspended sediment characteristics.
Biogeosciences Discuss., 12, 14773-14796, doi:10.5194/bgd-12-14773-2015, 2015
Modelling above-ground carbon dynamics using multi-temporal airborne lidar: insights from a Mediterranean woodland
Summary: Repeat-survey airborne laser scanning is used to build a simulation model of vegetation carbon dynamics in a Spanish woodland. Analyses of National Forest Inventory and tree-ring data are used to validate the woodland growth estimates. An average carbon sequestration rate of 1.95 Mg C/ha/year over a 100 year period is predicted, but this is highly sensitive to fire frequency. The study contributes to the important need to monitor large-scale carbon dynamics in the age of climate change.
Biogeosciences Discuss., 12, 14739-14772, doi:10.5194/bgd-12-14739-2015, 2015
Automation of soil flux chamber measurements: potentials and pitfalls
Biogeosciences Discuss., 12, 14693-14738, doi:10.5194/bgd-12-14693-2015, 2015
Responses of two nonlinear microbial models to warming or increased carbon input
Summary: Comparing two nonlinear microbial models, we found that in response to warming, soil C decreases in one model, but can increase or decrease in the other model sensitivity of priming response to carbon input increases with soil T in one model, but decreases in the other model Significance: these differences in the responses can be used to differentiate which model is more realistic, which will improve our understanding of the significance of soil microbial processes in terrestrial C cycle.
Biogeosciences Discuss., 12, 14647-14692, doi:10.5194/bgd-12-14647-2015, 2015
Technical Note: Drifting vs. anchored flux chambers for measuring greenhouse gas emissions from running waters
Summary: Flux chambers represent a potentially powerful methodological approach for measuring greenhouse gas emissions from running water. Here we compare the use of anchored and freely drifting chambers on various streams and provide novel guidance on how to apply flux chambers in these systems. The study clearly shows that drifting chambers have a very small impact on the water turbulence under the chamber, while anchored chambers enhance turbulence under the chambers and thus elevate fluxes.
Biogeosciences Discuss., 12, 14619-14645, doi:10.5194/bgd-12-14619-2015, 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
Autotrophic fixation of geogenic CO2 by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette
Biogeosciences Discuss., 12, 14555-14592, doi:10.5194/bgd-12-14555-2015, 2015
Water limitations on forest carbon cycling and conifer traits along a steep climatic gradient in the Cascade Mountains, Oregon
Summary: We investigated the role of water availability in shaping forest carbon cycling and conifer morphological traits in the Cascade Mountains, Oregon; a region that is expected to become warmer and drier in the coming century. Forest leaf area, productivity, and biomass were strongly related to mean annual water availability. Across the hydroclimatic gradient, trees exhibited inter-specific variation in traits that balanced maintaining hydraulic function against the need to compete for light.
Biogeosciences Discuss., 12, 14507-14553, doi:10.5194/bgd-12-14507-2015, 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
Box-modeling of the impacts of atmospheric nitrogen deposition and benthic remineralization on the nitrogen cycle of the eastern tropical South Pacific
Summary: Previously identified positive feedbacks within the nitrogen cycle in the eastern tropical South Pacific (ETSP) have challenged our understanding of the observed dynamics and stability of the nitrogen inventory. We present a box-model analysis of the biological and biogeochemical relations in the ETSP among nitrogen deposition, benthic denitrification and phosphate regeneration. Our results suggest dominant stabilizing feedbacks tending to keep a balanced nitrogen inventory in the ETSP.
Biogeosciences Discuss., 12, 14441-14479, doi:10.5194/bgd-12-14441-2015, 2015
Nitrogen fixation in sediments along a depth transect through the Peruvian oxygen minimum zone
Summary: Benthic nitrogen fixation and sulfate reduction were investigated in the Peruvian oxygen minimum zone. The data suggests a coupling of both activities to a large extent, but that also sulfide and organic matter availability are controlling the benthic diazotrophy in this area. The molecular analysis confirms the presence of heterotrophic diazotrophs. This work improves our understanding of N cycling in OMZ sediments and the understanding of N sources in the marine environment.
Biogeosciences Discuss., 12, 14401-14440, doi:10.5194/bgd-12-14401-2015, 2015
Influence of measurement uncertainties on soluble aerosol iron over the oceans
Biogeosciences Discuss., 12, 14377-14400, doi:10.5194/bgd-12-14377-2015, 2015
Complexity of diatom response to Lateglacial and Holocene climate and environmental change in ancient, deep, and oligotrophic Lake Ohrid (Macedonia/Albania)
Biogeosciences Discuss., 12, 14343-14375, doi:10.5194/bgd-12-14343-2015, 2015
Photomineralization and photomethanification of dissolved organic matter in Saguenay River surface water
Biogeosciences Discuss., 12, 14303-14341, doi:10.5194/bgd-12-14303-2015, 2015
Constant diversification rates of endemic gastropods in ancient Lake Ohrid: ecosystem resilience likely buffers environmental fluctuations
Summary: Based on our molecular data and performed analyses we found that the gastropods studied represent a comparatively old group that most likely evolved with a constant rate of diversification. However, preliminary data of the SCOPSCO deep-drilling program indicate signatures of environmental/climatic perturbations in Lake Ohrid. We therefore propose that the rate homogeneity observed has been caused by either a potential lack of catastrophic environmental events and/or a high ecosystem resilience.
Biogeosciences Discuss., 12, 14271-14302, doi:10.5194/bgd-12-14271-2015, 2015
Sediment source attribution from multiple land use systems with CSIA
Summary: Origin of suspended sediments in rivers is of crucial importance for optimization of catchment management. Sediment source attribution to a lowland river in Central Switzerland with compound specific stable isotopes analysis (CSIA) indicated that 65% of the suspended sediments originated from agricultural land during base flow, while forest was the dominant source during high flow. We achieved significant differences in CSIA signature from land uses dominated by C3 plant cultivation.
Biogeosciences Discuss., 12, 14245-14269, doi:10.5194/bgd-12-14245-2015, 2015
Climatic control on the occurrence of high-coercivity magnetic minerals and preservation of greigite in a 640 ka sediment sequence from Lake Ohrid (Balkans)
Summary: High-coercivity (hematite and goethite) magnetic mineral concentration of a Lake Ohrid sediment sequence reveals phases of increased soil erosion in the catchment on orbital and millennial time scales. Superimposed on this detrital magnetic pattern is the occurrence of early-diagenetic greigite during severe glacials, when lake productivity was low and mixing enhanced. Our study highlights the application of rock magnetism for terrestrial and lacustrine paleoenvironmental reconstructions.
Biogeosciences Discuss., 12, 14215-14243, doi:10.5194/bgd-12-14215-2015, 2015
Hidden biosphere in an oxygen-deficient Atlantic open ocean eddy: future implications of ocean deoxygenation on primary production in the eastern tropical North Atlantic
Summary: The waters of the tropical Atlantic Open Ocean usually contain compareably high concentrations oxygen. Now, it became clear that there are watermasses related to eddies that are nearly anoxic. We surveyed one of those eddies and found a biosphere that largely differed from the usual biosphere present in this area with a specific community responsible for primary production and for degradation processes. Further, we found the very first indication for active nitrogen loss in the open Atlantic.
Biogeosciences Discuss., 12, 14175-14213, doi:10.5194/bgd-12-14175-2015, 2015
Identification and analysis of low molecular weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography
Summary: We use a novel ion chromatographic analysis that provides the first identification and quantification of major low molecular weight dissolved organic carbon (LMW-DOC) compounds in basal ice. LMW-DOC concentrations were dependent on the bioavailability of the overridden organic carbon, which in turn, was influenced by the type of overridden material. The overridden material may thus act as a direct (abiotic leaching) and indirect (microbial cycling) source of DOC to the subglacial environment.
Biogeosciences Discuss., 12, 14139-14174, doi:10.5194/bgd-12-14139-2015, 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
Data-based estimates of the ocean carbon sink variability – first results of the Surface Ocean pCO2 Mapping intercomparison (SOCOM)
Summary: This study investigates variations in the CO2 uptake of the ocean from year to year. These variations have been calculated from measurements of the surface-ocean carbon content by various different interpolation methods. The equatorial Pacific is estimated to be the region with the strongest year-to-year variations, tied to the El Nino phase. The global ocean CO2 uptake gradually increased since about year 2000. The comparison of the interpolation methods identifies these findings as robust.
Biogeosciences Discuss., 12, 14049-14104, doi:10.5194/bgd-12-14049-2015, 2015
Marine regime shifts in ocean biogeochemical models: a case study in the Gulf of Alaska
Summary: Regime shifts have been suggested in the late 1970s and late 1980s in the Gulf of Alaska with important consequences for fisheries. Here we investigate the ability of a suite of ocean biogeochemical models of varying complexity to simulate these regime shifts. Our results demonstrate that ocean models can successfully simulate regime shifts in the Gulf of Alaska region, thereby improving our understanding of how changes in physical conditions are propagated from lower to upper trophic levels.
Biogeosciences Discuss., 12, 14003-14048, doi:10.5194/bgd-12-14003-2015, 2015
Uncertainty analysis of gross primary production partitioned from net ecosystem exchange measurements
Summary: We present a Bayesian estimation of uncertainty in half-hourly GPP partitioned from flux tower measurements of NEE. The results show that it is possible to do this at any desirable time step. This, in turn, can be used to quantify the propagated uncertainty when validating process-based simulators. We further show the importance of using non-informative priors compared to informative priors of the parameters of flux partitioning model as they speed up calculation without loss of precision.
Biogeosciences Discuss., 12, 13967-14002, doi:10.5194/bgd-12-13967-2015, 2015
Methane dynamics in warming tundra of Northeast European Russia
Summary: Arctic region is experiencing an unprecedented rise in permafrost temperatures leading to permafrsot thawing with dire implications for ecosystem structure and functioning. Therefore, it imperative to understand the behaviour of arictic ecosystems under present climatic conditions so that we are equipped with the information to predict their future behaviour. This study presents field data on methane exchange from Seida, located in NW Siberia, Russia measured using various biogeochemical tools.
Biogeosciences Discuss., 12, 13931-13965, doi:10.5194/bgd-12-13931-2015, 2015
Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a soil evolution model (SoilGen2.25)
Summary: This study evaluated the sensitivity of silicate mineral dissolution rates to intrinsic and extrinsic factors using a soil evolution model, SoilGen2.25. Modelling results showed a dominant role of pH and a direct effect of soil texture on dissolution rates. Clay migration and plant nutrient recycling influenced the pH and thus the dissolution rates. These results demonstrate the need to couple different soil processes in order to explain differences between lab and field dissolution rates
Biogeosciences Discuss., 12, 13887-13929, doi:10.5194/bgd-12-13887-2015, 2015
Testing the D/H ratio of alkenones and palmitic acid as salinity proxies in the Amazon Plume
Biogeosciences Discuss., 12, 13859-13885, doi:10.5194/bgd-12-13859-2015, 2015
Estimation of microbial metabolism and co-occurrence patterns in fracture groundwaters of deep crystalline bedrock at Olkiluoto, Finland
Summary: Over 95% of the microbial communities in isolated groundwater in Olkiluoto bedrock, Finland, is composed of only a few common species. The remaining rare microbiome contains over 3- and 6-fold more microbial diversity. The rare microbiome is an unlimited source of genomic functionality in the ecosystem. These microorganisms can respond to change caused by physical or biological factors that may lead to alterations in the diversity and function of the microbial communities in crystalline bedrock.
Biogeosciences Discuss., 12, 13819-13857, doi:10.5194/bgd-12-13819-2015, 2015
Spatial distribution and sources of organic carbon in the surface sediment of the Bosten Lake, China
Biogeosciences Discuss., 12, 13793-13817, doi:10.5194/bgd-12-13793-2015, 2015
Climate-driven shifts in continental net primary production implicated as a driver of a recent abrupt increase in the land carbon sink
Summary: Recent analyses of the global carbon budget found a substantial increase in the land sink in the late 1980s whose origin remains unknown. Consistent with this shift, we find that plant growth has increased in the late 1980s especially in Eurasia and northern Africa. There climatic constraints on plant growth have eased possibly due to linked climate modes in the North Atlantic. Better understanding of North Atlantic climate may be essential for more credible projections of the land carbon sink.
Biogeosciences Discuss., 12, 13767-13791, doi:10.5194/bgd-12-13767-2015, 2015
Molecular characterization of dissolved organic matter from subtropical wetlands: a comparative study through the analysis of optical properties, NMR and FTICR/MS
Summary: Wetlands commonly feature high levels of natural dissolved organic matter (DOM), a critical component in their biogeochemical functions. Here we describe the first detailed, comparative, molecular characterization of DOM in three sub-tropical, pulsed, wetlands, using optical properties, high field nuclear magnetic resonance and ultrahigh resolution mass spectrometry, and compare compositional features to variations in organic matter sources and flooding characteristics.
Biogeosciences Discuss., 12, 13711-13765, doi:10.5194/bgd-12-13711-2015, 2015
Characterizing Leaf Area Index (LAI) and Vertical Foliage Profile (VFP) over the United States
Summary: This paper provides a unique insight into vertical distribution of leaf area index across North American ecosystems using spaceborne lidar data. This data set of leaf area index and vertical foliage profile can help set up a baseline of canopy structure needed for evaluating climate and land use induced forest changes at continental scale in the future.
Biogeosciences Discuss., 12, 13675-13710, doi:10.5194/bgd-12-13675-2015, 2015
Spring bloom onset in the Nordic Seas
Summary: We investigated the bloom onset in the Nordic Seas using 5 bio-optical floats. We found that the float data are consistent with two possible scenarios for the onset of blooms in the Nordic Seas. The Nordic Seas blooms could have started either when the light became sufficiently abundant that the division rates exceeded the loss rates, or when the photoperiod, the number of daily light hours experienced by phytoplankton, exceeded a critical value.
Biogeosciences Discuss., 12, 13631-13673, doi:10.5194/bgd-12-13631-2015, 2015
Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica
Biogeosciences Discuss., 12, 13593-13629, doi:10.5194/bgd-12-13593-2015, 2015
Nitrogen cycling in the subsurface biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic
Summary: In the sediments underlying the global oligotrophic ocean, low levels of microbial activity persist, despite low input of organic matter from surface ocean productivity. Using measured nitrogen and oxygen isotopes of porewater nitrate we estimate the magnitude and extent of microbial nitrogen cycling. We find evidence for the overlap of both denitrification as well as autotrophic pathways such as nitrification and nitrogen fixation - pointing to a relatively large role for subsurface autotrophy.
Biogeosciences Discuss., 12, 13545-13591, doi:10.5194/bgd-12-13545-2015, 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
Protist communities in a marine oxygen minimum zone off Costa Rica by 454 pyrosequencing
Summary: Photosynthetic Dinoflagellates predominated in the surface, while potential parasitic Dinoflagellates and Ciliates dominated in the OMZ and deeper water in Costa Rica Dome. Total and active protists in the anoxic core were distinct from those in others depths. Reduced community diversity and presence of parasitic/symbiotic trophic lifestyles in the suboxic/anoxic OMZ suggests that oxygen deficiency could cause a change of protist community and the associated microbial food web as well.
Biogeosciences Discuss., 12, 13483-13509, doi:10.5194/bgd-12-13483-2015, 2015
Mediterranean climate since the Middle Pleistocene: a 640 ka stable isotope record from Lake Ohrid (Albania/Macedonia)
Biogeosciences Discuss., 12, 13427-13481, doi:10.5194/bgd-12-13427-2015, 2015
Technical Note: A generic law-of-the-minimum flux limiter for simulating substrate limitation in biogeochemical models
Biogeosciences Discuss., 12, 13399-13425, doi:10.5194/bgd-12-13399-2015, 2015
Hydroxy fatty acids in fresh snow samples from northern Japan: long-range atmospheric transport of Gram-negative bacteria by Asian winter monsoon
Summary: Our manuscript represents the first field-based data set on the abundances of hydroxy fatty acids (FAs) in fresh snow and its filtering capacity to reduce hydroxy FAs burden from the atmosphere.
• Hydroxy fatty acids (FAs) in snow indicate contribution from soil microbes and higher plants.
• Air mass back-trajectories reveal their transport from Russia, Siberia and China.
Biogeosciences Discuss., 12, 13375-13397, doi:10.5194/bgd-12-13375-2015, 2015
Using satellite data to improve the leaf phenology of a global Terrestrial Biosphere Model
Summary: Previous model evaluation studies have shown that Terrestrial Biosphere Models (TBMs) need a better representation of model phenology, but the model deficiency could be related to incorrect model parameters or inaccurate model structure. This paper presenting a framework for optimising the parameters of phenology models that are commonly used in TBMs. It further demonstrates that the optimisation can result in changes to trends in vegetation productivity and an improvement in gross C fluxes.
Biogeosciences Discuss., 12, 13311-13373, doi:10.5194/bgd-12-13311-2015, 2015
Seasonal, sub-seasonal and spatial fluctuations in oxygen-depleted bottom waters in an embayment of an eastern boundary upwelling system: St Helena Bay
Summary: Seasonal, sub-seasonal and spatial fluctuations in bottom dissolved oxygen (DO) are examined in St Helena Bay, the largest and most productive bay of the southern Benguela upwelling system. Superimposed on the seasonal decline of DO concentrations in bottom waters were sub-seasonal events of hypoxia and anoxia linked to episodic deposition of organic matter as dictated by cell death processes of exceptional dinoflagellate blooms as indicated by increases in bottom Chl a concentrations.
Biogeosciences Discuss., 12, 13283-13309, doi:10.5194/bgd-12-13283-2015, 2015
Ash leachates from some recent eruptions of Mount Etna (Italy) and Popocatépetl (Mexico) volcanoes and their impact on amphibian living freshwater organisms
Biogeosciences Discuss., 12, 13241-13282, doi:10.5194/bgd-12-13241-2015, 2015
Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China
Biogeosciences Discuss., 12, 13215-13240, doi:10.5194/bgd-12-13215-2015, 2015
Southwestern Tropical Atlantic coral growth response to atmospheric circulation changes induced by ozone depletion in Antarctica
Biogeosciences Discuss., 12, 13193-13213, doi:10.5194/bgd-12-13193-2015, 2015
Spatial and temporal trends in summertime climate and water quality indicators in the coastal embayments of Buzzards Bay, Massachusetts
Biogeosciences Discuss., 12, 13159-13192, doi:10.5194/bgd-12-13159-2015, 2015
Natural variability in the surface ocean carbonate ion concentration
Summary: We investigate variability in surface ocean carbonate chemistry using output from a 1000-year control simulation of an Earth System Model. We find that the detection timescale for trends is strongly influenced by the variability. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results will aid the interpretation of trends calculated from spatially- and temporally-sparse observations.
Biogeosciences Discuss., 12, 13123-13157, doi:10.5194/bgd-12-13123-2015, 2015
EUROSPEC: at the interface between remote sensing and ecosystem CO2 flux measurements in Europe
Biogeosciences Discuss., 12, 13069-13121, doi:10.5194/bgd-12-13069-2015, 2015
The root economics spectrum: divergence of absorptive root strategies with root diameter
Biogeosciences Discuss., 12, 13041-13067, doi:10.5194/bgd-12-13041-2015, 2015
Improved end-member characterization of modern organic matter pools in the Ohrid Basin (Albania, Macedonia) and evaluation of new palaeoenvironmental proxies
Summary: Lake Ohrid is situated in the southern Balkans between Albania and Macedonia. It is a unique ecosystem with remarkable biodiversity and a sediment record of past climate that goes back more than a million years. Detailed reconstructions of past climate development and human alteration of the environment require underpinned and so in this study we go the present day lake vegetation and catchment soils and test new proxies over one of the known recent cooling events of the region 8200 years ago.
Biogeosciences Discuss., 12, 12975-13039, doi:10.5194/bgd-12-12975-2015, 2015
Millennial changes in North Atlantic oxygen concentrations
Summary: Models predict a decrease in future ocean O2, driven by surface water freshening in the polar regions and associated reduction in ocean circulation. Here we assess this effect in the past, focussing on the response of deep and intermediate waters from the North Atlantic Ocean during large-scale ice rafting and millennial scale cooling events of the last glacial. Our assessment agrees with the models, but also highlights the importance of biological processes driving ocean O2 changes.
Biogeosciences Discuss., 12, 12947-12973, doi:10.5194/bgd-12-12947-2015, 2015
Technical Note: A simple calculation algorithm to separate high-resolution CH4 flux measurements into ebullition and diffusion-derived components
Summary: Processes driving the production, transformation and transport of CH4 in wetlands are highly complex. Thus, serious challenges are constitutes in terms of process understanding, potential drivers and the calculation of reliable CH4 emission estimates. We present a simple calculation algorithm to separate CH4 fluxes measured with closed chambers into diffusion- and ebullition-derived components, which helps facilitating the identification of underlying dynamics and potential drivers.
Biogeosciences Discuss., 12, 12923-12945, doi:10.5194/bgd-12-12923-2015, 2015
Stable isotope study of a new chondrichthyan fauna (Kimmeridgian, Porrentruy, Swiss Jura): an unusual freshwater-influenced isotopic composition for the hybodont shark Asteracanthus
Summary: The oxygen isotopic composition of chondrichthyan teeth from the Late Jurassic of the Swiss Jura was measured to get ecological information. The main finding is a freshwater-influenced isotopic signature for the shark Asteracanthus (Hybodontiformes), classically considered as marine. Since those teeth were found in marine deposits and do not show any sign of transportation, we propose, in addition to a mainly marine ecology, excursions into areas of lower salinity, possibly for reproduction.
Biogeosciences Discuss., 12, 12899-12921, doi:10.5194/bgd-12-12899-2015, 2015
Climate change impacts on net primary production (NPP) and export production (EP) regulated by increasing stratification and phytoplankton community structure in CMIP5 models
Summary: Global NPP and EP are reduced considerably for RCP8.5; negative response of NPP and EP to stratification increases reflects a bottom-up control; Models with dynamic phytoplankton community structure show larger declines in EP than in NPP driven by phytoplankton community composition shifts; projections of the NPP response to climate change depend on the phytoplankton community structure, the efficiency of the biological pump, and the levels of regenerated production.
Biogeosciences Discuss., 12, 12851-12897, doi:10.5194/bgd-12-12851-2015, 2015
Optimizing the impact of temperature on bio-hydrogen production from food waste and its derivatives under no pH control using statistical modelling
Biogeosciences Discuss., 12, 12823-12850, doi:10.5194/bgd-12-12823-2015, 2015
Soil N2O and NO emissions from land use and land-use change in the tropics and subtropics: a meta-analysis
Summary: Land use change in the tropics may substantially alter soil N2O and NO emissions. We summarised available data and developed a set of statistical models that allows tropical countries to estimate, for example, agricultural N2O emissions from fertilisation rate and water filled pore space. Further, intermediate land use stages and time since conversion are often crucially lacking, whereas they could represent significant sources. Other gaps were peat forests and oil palm and soy plantations.
Biogeosciences Discuss., 12, 12783-12821, doi:10.5194/bgd-12-12783-2015, 2015
Dissolved organic carbon lability and stable isotope shifts during microbial decomposition in a tropical river system
Summary: Rivers transport a large amount of carbon as dissolved organic carbon (DOC). Our incubation experiments on water of the Tana River, Kenya, showed that microbial decomposition of 10-60% of the initial DOC occurred within the first 24-48h. Simultaneously, there was a decrease in isotopic composition, indicating that DOC derived from C4 vegetation is preferentially decomposed. This has implications for the assessment of vegetation in a catchment based on isotope signatures of riverine carbon.
Biogeosciences Discuss., 12, 12761-12782, doi:10.5194/bgd-12-12761-2015, 2015
Ocean dynamic processes causing spatially heterogeneous distribution of sedimentary caesium-137 massively released from the Fukushima Dai-ichi Nuclear Power Plant
Biogeosciences Discuss., 12, 12713-12759, doi:10.5194/bgd-12-12713-2015, 2015
Phytoplankton calcification as an effective mechanism to prevent cellular calcium poisoning
Summary: The white cliffs of Dover date back to the Cretaceous and are made up by microscopic chalky shells which were produced mainly by marine phytoplankton (coccolithophores). This is iconic proof for their success at times of relatively high seawater calcium concentrations and, as shown here, to be linked to their ability to precipitate calcium as chalk. The invention of calcification can thus be considered an evolutionary milestone allowing coccolithophores to thrive at times when others struggled.
Biogeosciences Discuss., 12, 12691-12712, doi:10.5194/bgd-12-12691-2015, 2015
Application of the 15N-Gas Flux method for measuring in situ N2 and N2O fluxes due to denitrification in natural and semi-natural terrestrial ecosystems and comparison with the acetylene inhibition technique
Biogeosciences Discuss., 12, 12653-12689, doi:10.5194/bgd-12-12653-2015, 2015
Influence of timing of sea ice retreat on phytoplankton size during marginal ice zone bloom period in the Chukchi and Bering shelves
Summary: This study provides the general relationship between the timing of sea ice retreat and phytoplankton size structure during marginal ice zone bloom period in the Chukchi and Bering shelves using satellite remote sensing approach. We also found not only the length of ice-free season but also annual phytoplankton size positively correlated with annual net primary production.
Biogeosciences Discuss., 12, 12611-12651, doi:10.5194/bgd-12-12611-2015, 2015
Looking beyond stratification: a model-based analysis of the biological drivers of oxygen depletion in the North Sea
Summary: We used the ECOHAM5 model to provide a consistent picture of the physical and biological drivers of hypoxia in the North Sea under stratified conditions. Regions susceptible to hypoxia are characterised by low tidal mixing and moderate water depth (~45 m). Variations in upper layer productivity drive the inter-annual variability of bottom O2 conditions. The model-based analysis revealed that benthic and pelagic remineralisation account for 90% of bottom O2 consumption observed at North Dogger.
Biogeosciences Discuss., 12, 12543-12610, doi:10.5194/bgd-12-12543-2015, 2015
The carbon cycle in Mexico: past, present and future of C stocks and fluxes
Summary: We modelled the carbon (C) cycle in Mexico for three different time periods: past (20th century), present (2000-2005) and future (2006-2100). We used different available products to estimate C stocks and fluxes in the country. Contrary to other current estimates, our results showed that Mexico was a C sink and this is likely to continue in the next century (unless the most extreme climate-change scenarios are reached).
Biogeosciences Discuss., 12, 12501-12541, doi:10.5194/bgd-12-12501-2015, 2015
Skeletal mineralogy of coral recruits under high temperature and pCO2
Summary: In recent years much research has focussed on whether corals will be able to build their skeletons under predicted ocean acidification. One strategy corals may employ is changing the mineralogy of their skeletons from aragonite to the less soluble polymorph of calcium carbonate; calcite. Here we show that newly settled coral recruits are unable to produce calcite in their skeletons under near-future elevations in pCO2, which may leave them more vulnerable to ocean acidification.
Biogeosciences Discuss., 12, 12485-12500, doi:10.5194/bgd-12-12485-2015, 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
Do land surface models need to include differential plant species responses to drought? Examining model predictions across a latitudinal gradient in Europe
Summary: Future climate change has the potential to increase drought in many regions of the globe, making it essential that land surface models (LSMs) used in coupled climate models, realistically capture the drought responses of vegetation. We tested whether variable drought sensitivities are needed in a LSM, to explain the observed large-scale patterns of drought, across a latitudinal gradient in Europe during the 2003 heatwave. Our results indicate that LSMs will over-estimate drought impacts in drier
Biogeosciences Discuss., 12, 12349-12393, doi:10.5194/bgd-12-12349-2015, 2015
Optical properties and bioavailability of dissolved organic matter along a flow-path continuum from soil pore waters to the Kolyma River, Siberia
Summary: In this study, we provide new findings with regards to the spatial distribution of dissolved organic matter (DOM) concentration, bioavailability, and optical properties during mid-summer hydrologic conditions throughout the Kolyma River basin in Northeast Siberia. This is particularly critical for this region, where the future fate of organic carbon currently frozen in permafrost soils (and whether it ultimately is released as CO2 and CH4) is tightly linked to the lability of this material.
Biogeosciences Discuss., 12, 12321-12347, doi:10.5194/bgd-12-12321-2015, 2015
Effects of dust additions on phytoplankton growth and DMS production in high CO2 northeast Pacific HNLC waters
Biogeosciences Discuss., 12, 12281-12319, doi:10.5194/bgd-12-12281-2015, 2015
Spatial variability of diploptene δ13C values in thermokarst lakes: the potential to analyse the complexity of lacustrine methane cycling
Biogeosciences Discuss., 12, 12157-12189, doi:10.5194/bgd-12-12157-2015, 2015
Metagenomic analyses of the late Pleistocene permafrost – additional tools for reconstruction of environmental conditions
Summary: A comparative analysis of the metagenomes from two 30,000 year-old permafrost samples, one of lake-alluvial origin and the other from late Pleistocene Ice Complex sediments, revealed significant differences within microbial communities. The late Pleistocene Ice Complex sediments (which have been characterized by the absence of methane with lower values of redox-potential and Fe2+ content) showed both a low abundance of methanogenic archaea and enzymes from the carbon, nitrogen and sulfur cycles.
Biogeosciences Discuss., 12, 12091-12119, doi:10.5194/bgd-12-12091-2015, 2015
Model aided quantification of dissolved carbon and nitrogen release after windthrow disturbance in an Austrian karst system
Summary: We consider the time period before and after a wind disturbance in an Austrian karst system. Using a process-based flow and solute transport simulation model we estimate impacts on DIN and DOC. We show that DIN increases for several years while DOC remains within its pre-disturbance variability. Simulated transit times indicate that impact passes through the hydrological system within some months but with a small fraction exceeding transit times of even a year.
Biogeosciences Discuss., 12, 11987-12026, doi:10.5194/bgd-12-11987-2015, 2015
Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles
Summary: We present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types, and use the model to quantitatively assess the relative roles of iron versus grazing in determining phytoplankton biomass in the Southern Ocean. Our results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community rather than iron limitation.
Biogeosciences Discuss., 12, 11935-11985, doi:10.5194/bgd-12-11935-2015, 2015
Modelling anomalies in the spring and autumn land surface phenology of the European forest
Biogeosciences Discuss., 12, 11833-11861, doi:10.5194/bgd-12-11833-2015, 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
Effect of sporadic destratification, seasonal overturn and artificial mixing on CH4 emissions at the surface of a subtropical hydroelectric reservoir (Nam Theun 2 Reservoir, Lao PDR)
Biogeosciences Discuss., 12, 11349-11385, doi:10.5194/bgd-12-11349-2015, 2015
Low methane (CH4) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)
Biogeosciences Discuss., 12, 11313-11347, doi:10.5194/bgd-12-11313-2015, 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
The organic sea surface microlayer in the upwelling region off Peru and implications for air–sea exchange processes
Biogeosciences Discuss., 12, 10579-10619, doi:10.5194/bgd-12-10579-2015, 2015
Water use strategies of a young Eucalyptus urophylla forest in response to seasonal change of climatic factors in South China
Summary: a) More dramatically decreased hydralic conductivity when stomatal conductance was decreasing may shed some light on the mechanism of the high WUE of Eucalyptus when exposed to drought conditions. b) As tree grows, ks is more sensitive to water loss. c) The decrease in stomatal sensitivity of GSref to D along the radiation gradient accounted for an important aspect of “plastic characteristics” for E. urophylla.
Biogeosciences Discuss., 12, 10469-10510, doi:10.5194/bgd-12-10469-2015, 2015
Effects of a windthrow disturbance on the carbon balance of a broadleaf deciduous forest in Hokkaido, Japan
Summary: Using the eddy covariance and biometrical methods, the carbon budget was measured in a deciduous broadleaf forest in Japan, where accidental damage by a strong typhoon damaged 40% of trees. Before the disturbance, the forest was an evident carbon sink, and it subsequently transformed to net a carbon source. GPP only decreased by 6% just after the disturbance. On the other hand, Re increased by 39%. Undergrowth dwarf bamboo has an important role in the carbon budget.
Biogeosciences Discuss., 12, 10425-10468, doi:10.5194/bgd-12-10425-2015, 2015
Co-occurrence patterns in aquatic bacterial communities across changing permafrost landscapes
Summary: Bacterial co-occurrence patterns were non-random, with evidence of habitat preferences. Co-occurrence networks revealed complex interdependencies within the bacterioplankton communities and showed contrasting linkages to environmental conditions among the main bacterial phyla. The thaw ponds and lakes networks were composed of a limited number of highly connected taxa, which render these communities more resilient to environmental change, but sensitive to the loss of these keystone species.
Biogeosciences Discuss., 12, 10233-10269, doi:10.5194/bgd-12-10233-2015, 2015
Soil carbon sequestration by three perennial legume pastures is greater in deeper soil layers than in the surface soil
Biogeosciences Discuss., 12, 10115-10135, doi:10.5194/bgd-12-10115-2015, 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
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
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
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