Temporal changes in surface partial pressure of carbon dioxide and carbonate saturation state in the eastern equatorial Indian Ocean during the 1962–2012 period
Summary: A mean rate of increase in sea surface partial pressure of carbon dioxide and decrease in carbonate saturation state in the eastern equatorial Indian Ocean, a CO2 source to the atmosphere, during the 1962–2012 period was determined. These changes were most likely associated with the increasing atmospheric CO2 concentration, and the transport of accumulated anthropogenic CO2 from a CO2 sink region via basin-scale ocean circulations.
Retrieval of the photochemical reflectance index for assessing xanthophyll cycle activity: a comparison of near-surface optical sensors
Summary: Lower-cost optical sensors, which can be left outdoors, are often used to provide information regarding plant photosynthetic activity. A lower-cost sensor was compared with an expensive instrument to see if the data collected were comparable. Both instruments were able to track changes in photosynthetic activity, but the values recorded by each were different. This can cause difficulties when comparing data across space and time. We provide advice on how best to use these sensors in the field.
Corrigendum to "Inter-annual variation of chlorophyll in the northern South China Sea observed at the SEATS Station and its asymmetric responses to climate oscillation" published in Biogeosciences, 10, 7449–7462, 2013
Summary: We have discovered and verified a new CO2 sink in one of the most unlikely places on earth－a saline desert located in a desert-oasis ecotone. The observed downward CO2 flux was not found in either plants or soil, but in groundwater. Fluctuation of the groundwater table moves the dissolved inorganic carbon in soil, which originated from soil/root respiration, downward into the groundwater body and forms a carbon sink hidden under the desert.
Effects of seabird nitrogen input on biomass and carbon accumulation after 50 years of primary succession on a young volcanic island, Surtsey
Summary: We studied the influence of allochthonous N inputs on primary succession and soil development of a 50-year-old volcanic island, Surtsey. Seabirds increased the ecosystem N accumulation rate inside their colony to ~47 kg ha-1 y-1, compared to 0.7 kg ha-1 y-1 outside it. A strong relationship was found between total ecosystem N stock and both total above- and belowground biomass and SOC stock, which shows how fast external N input can boost primary succession and soil formation.
Disentangling the response of forest and grassland energy exchange to heatwaves under idealized land–atmosphere coupling
Summary: This study disentangles the response of forest and grassland to heatwaves, to interpret the findings of Teuling et al. (2010), who found systematically higher temperatures over forests than over grasslands in European heatwaves. By means of a study with a simple coupled land–atmosphere model, we show that the increase in stomatal resistance of vegetation under high values of vapor pressure deficit explains most of the differences and that this increase is enhanced by boundary layer feedbacks.
The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate
Summary: The ratio of nitrogen-15 to nitrogen-14 of macroalgae has been termed the DNA of sewage. Higher amounts of N-15 have been suggested to indicate the influence of sewage-derived N. But what exactly does the ratio of 15N/14N record?
We found that the nitrogen isotopic ratio was dependent upon not only the value in the water but also its concentration of nitrate. At low concentration there was little fractionation, but at higher values the uptake by algae left more of the N-15 in the water.
Export, biodegradation, and disinfection byproduct formation of dissolved and particulate organic carbon in a forested headwater stream during extreme rainfall events
Summary: Storm-enhanced export of particulate organic carbon in a mountainous headwater stream increased nonlinearly above thresholds of precipitation and discharge, far exceeding the relatively small increases of dissolved organic carbon. Particulate organic carbon exported during extreme storm events provide potential sources of reactive organic components that can rapidly biodegrade and form disinfection byproducts such as trihalomethanes in the headwater stream.
Summary: Estimates of ocean carbon uptake from ocean biogeochemical models are key to our understanding of the global carbon cycle. Such estimates suggest that ocean carbon uptake is decreasing due to climate change, and particularly due to strengthening of the Southern Hemisphere winds. We show that these model-based estimates are highly uncertain due to poorly resolved physical processes (mesoscale ocean eddies) and uncertainty in the observed surface wind forcing used to drive the models.
Soil CO2 efflux from mountainous windthrow areas: dynamics over 12 years post-disturbance
Summary: In this study soil CO2 efflux was measured at a montane mixed-forest site and a subalpine spruce forest site. Each site consisted of an undisturbed forest and two adjacent windthrow areas, differing regarding the time since disturbance. The combination of chronosequence and direct time-series approaches enabled us to investigate soil CO2 efflux dynamics over 12 years post-disturbance. According to our estimates, ~ 500 to 700 g C m-2 yr-1 are released via soil CO2 efflux from younger windthrows.
Diversity and seasonal dynamics of airborne archaea
Summary: We have investigated the presence of archaea as well as their amoA gene diversity in aerosol particles collected over 1 year in central Europe and found that, within the 16S and amoA gene, Thaumarchaeota prevail and experience a diversity peak in fall, while only few Euryarchaeota were detected primarily in spring. We also compared the results with airborne archaea from Cape Verde and observe that the proportions of Euryarchaeota seem to be enhanced in coastal air compared to continental air.
J. Fröhlich-Nowoisky, C. Ruzene Nespoli, D. A. Pickersgill, P. E. Galand, I. Müller-Germann, T. Nunes, J. Gomes Cardoso, S. M. Almeida, C. Pio, M. O. Andreae, R. Conrad, U. Pöschl, and V. R. Després Biogeosciences, 11, 6067-6079, 2014 AbstractFinal Revised Paper (PDF, 658 KB)Supplement (797 KB)Discussion Paper (BGD)
11 Nov 2014
N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores
Summary: Atmospheric loss of N from savanna soil was dominated by N2 emissions (82-99% of total N loss to atmosphere). Nitric oxide emissions significantly contributed at 50% WFPS; high temperatures and N2O emissions were negligible. Based on a simple upscale approach we estimated annual loss of N to the atmosphere at 7.5kg yr-1. N2O emission was low for most samples, but high for a small subset of cores at 75% WFPS (due to short periods where such conditions occur this has little effect on totals).
Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification
H. Sahling, M. Römer, T. Pape, B. Bergès, C. dos Santos Fereirra, J. Boelmann, P. Geprägs, M. Tomczyk, N. Nowald, W. Dimmler, L. Schroedter, M. Glockzin, and G. Bohrmann Biogeosciences, 11, 6029-6046, 2014 AbstractFinal Revised Paper (PDF, 7794 KB)Discussion Paper (BGD)
06 Nov 2014
Climate versus carbon dioxide controls on biomass burning: a model analysis of the glacial–interglacial contrast
Effects of drought on nitrogen turnover and abundances of ammonia-oxidizers in mountain grassland
Summary: In mountain grasslands drought has distinct transient effects on soil nitrogen cycling and bacterial and archaeal ammonia-oxidizers (AOB and AOA), which could have been related to a niche differentiation of these two groups at increasing NH4+ levels. However, the effective strength of drought was modulated by the level of grassland management.
Fluid chemistry of the low temperature hyperalkaline hydrothermal system of Prony Bay (New Caledonia)
C. Monnin, V. Chavagnac, C. Boulart, B. Ménez, M. Gérard, E. Gérard, C. Pisapia, M. Quéméneur, G. Erauso, A. Postec, L. Guentas-Dombrowski, C. Payri, and B. Pelletier Biogeosciences, 11, 5687-5706, 2014 AbstractFinal Revised Paper (PDF, 1830 KB)Discussion Paper (BGD)
16 Oct 2014
Soil–atmosphere exchange of ammonia in a non-fertilized grassland: measured emission potentials and inferred fluxes
Corrigendum to "Mechanisms of microbial carbon sequestration in the ocean – future research directions" published in Biogeosciences, 11, 5285–5306, 2014
N. Jiao, C. Robinson, F. Azam, H. Thomas, F. Baltar, H. Dang, N. J. Hardman-Mountford, M. Johnson, D. L. Kirchman, B. P. Koch, L. Legendre, C. Li, J. Liu, T. Luo, Y.-W. Luo, A. Mitra, A. Romanou, K. Tang, X. Wang, C. Zhang, and R. Zhang Biogeosciences, 11, 5565-5565, 2014 AbstractFinal Revised Paper (PDF, 16 KB)Corresponding ArticleSpecial Issue