Plant functional type classification for earth system models: results from the European Space Agency's Land Cover Climate Change Initiative
Poulter, B. ; MacBean, N. ; Hartley, A. ; Khlystova, I. ; Arino, O. ; Betts, R. ; Bontemps, S. ; Boettcher, M. ; Brockmann, C. ; Defourny, P. ; Hagemann, S. ; Herold, M. ; Kirches, C. ; Lamarche, C. ; Lederer, D. ; Ottlé, C. ; Peters, M. ; Peylin, P. - \ 2015
Geoscientific Model Development 8 (2015). - ISSN 1991-959X - p. 2315 - 2328.
global vegetation model - world map - ecosystems - forests - cycle - uncertainties - resolution - feedbacks - phenology - database
Global land cover is a key variable in the earth system with feedbacks on climate, biodiversity and natural resources. However, global land cover data sets presently fall short of user needs in providing detailed spatial and thematic information that is consistently mapped over time and easily transferable to the requirements of earth system models. In 2009, the European Space Agency launched the Climate Change Initiative (CCI), with land cover (LC_CCI) as 1 of 13 essential climate variables targeted for research development. The LC_CCI was implemented in three phases: first responding to a survey of user needs; developing a global, moderate-resolution land cover data set for three time periods, or epochs (2000, 2005, and 2010); and the last phase resulting in a user tool for converting land cover to plant functional type equivalents. Here we present the results of the LC_CCI project with a focus on the mapping approach used to convert the United Nations Land Cover Classification System to plant functional types (PFTs). The translation was performed as part of consultative process among map producers and users, and resulted in an open-source conversion tool. A comparison with existing PFT maps used by three earth system modeling teams shows significant differences between the LC_CCI PFT data set and those currently used in earth system models with likely consequences for modeling terrestrial biogeochemistry and land–atmosphere interactions. The main difference between the new LC_CCI product and PFT data sets used currently by three different dynamic global vegetation modeling teams is a reduction in high-latitude grassland cover, a reduction in tropical tree cover and an expansion in temperate forest cover in Europe. The LC_CCI tool is flexible for users to modify land cover to PFT conversions and will evolve as phase 2 of the European Space Agency CCI program continues.
The uncertain climate footprint of wetlands under human pressure
Petrescu, A.J. ; Lohila, A. ; Tuovinen, J.P. ; Baldocchi, D.D. ; Desai, A.R. ; Veenendaal, E.M. ; Schrier-Uijl, A. - \ 2015
Proceedings of the National Academy of Sciences of the United States of America 112 (2015)15. - ISSN 0027-8424 - p. 4594 - 4599.
methane emissions - carbon-dioxide - peatlands - ecosystem - fluxes - variability - dynamics - drainage - balance - cycle
Significant climate risks are associated with a positive carbon–temperature feedback in northern latitude carbon-rich ecosystems, making an accurate analysis of human impacts on the net greenhouse gas balance of wetlands a priority. Here, we provide a coherent assessment of the climate footprint of a network of wetland sites based on simultaneous and quasi-continuous ecosystem observations of CO2 and CH4 fluxes. Experimental areas are located both in natural and in managed wetlands and cover a wide range of climatic regions, ecosystem types, and management practices. Based on direct observations we predict that sustained CH4 emissions in natural ecosystems are in the long term (i.e., several centuries) typically offset by CO2 uptake, although with large spatiotemporal variability. Using a space-for-time analogy across ecological and climatic gradients, we represent the chronosequence from natural to managed conditions to quantify the “cost” of CH4 emissions for the benefit of net carbon sequestration. With a sustained pulse–response radiative forcing model, we found a significant increase in atmospheric forcing due to land management, in particular for wetland converted to cropland. Our results quantify the role of human activities on the climate footprint of northern wetlands and call for development of active mitigation strategies for managed wetlands and new guidelines of the Intergovernmental Panel on Climate Change (IPCC) accounting for both sustained CH4 emissions and cumulative CO2 exchange.
Intertidal biofilm distribution underpins differential tide-following behavior of two sandpiper species (Calidris mauri and Calidris alpina) during northward migration
Jimenez, A. ; Elner, R.W. ; Favaro, C. ; Rickards, K. ; Ydenberg, R.C. - \ 2015
Estuarine Coastal and Shelf Science 155 (2015). - ISSN 0272-7714 - p. 8 - 16.
fraser-river estuary - western sandpipers - shorebird distribution - sediment - waders - microphytobenthos - invertebrates - predation - abundance - cycle
The discovery that some shorebird species graze heavily on biofilm adds importance to elucidating coastal processes controlling biofilm, as well as impetus to better understand patterns of shorebird use of intertidal flats. Western sandpipers (Calidris mauri) and dunlin (Calidris alpina) stopover in the hundreds of thousands on the Fraser River estuary, British Columbia, Canada, during northward migration to breeding areas. Western sandpipers show greater modification of tongue and bill morphology for biofilm feeding than dunlin, and their diet includes more biofilm. Therefore, we hypothesized that these congeners differentially use the intertidal area. A tide following index (TFI) was used to describe their distributions in the upper intertidal during ebbing tides. Also, we assessed sediment grain size, biofilm (= microphytobenthic or MPB) biomass and invertebrate abundance. Foraging dunlin closely followed the ebbing tide line, exploiting the upper intertidal only as the tide retreated through this area. In contrast, western sandpipers were less prone to follow the tide, and spent more time in the upper intertidal. Microphytobenthic biomass and sediment water content were highest in the upper intertidal, indicating greater biofilm availability for shorebirds in the first 350 m from shore. Invertebrate density did not differ between sections of the upper intertidal. Overall, western sandpiper behaviour and distribution more closely matched MPB biofilm availability than invertebrate availability. Conservation of sandpipers should consider physical processes, such as tides and currents, which maintain the availability of biofilm, a critical food source during global migration.
A multilevel analysis of fruit growth of two tomato cultivars in response to fruit temperature
Okello, R.C. ; Visser, P.H.B. de; Heuvelink, E. ; Lammers, M. ; Maagd, R.A. de; Struik, P.C. ; Marcelis, L.F.M. - \ 2015
Physiologia Plantarum 153 (2015)3. - ISSN 0031-9317 - p. 403 - 418.
cell-division - size - endoreduplication - arabidopsis - expression - expansion - genotype - plants - genes - cycle
Fruit phenotype is a resultant of inherent genetic potential in interaction with impact of environment experienced during crop and fruit growth. The aim of this study was to analyze the genetic and physiological basis for the difference in fruit size between a small (‘Brioso’) and intermediate (‘Cappricia’) sized tomato cultivar exposed to different fruit temperatures. It was hypothesized that fruit heating enhances expression of cell cycle and expansion genes, rates of carbon import, cell division and expansion, and shortens growth duration, whereas increase in cell number intensifies competition for assimilates among cells. Unlike previous studies in which whole-plant and fruit responses cannot be separated, we investigated the temperature response by varying fruit temperature using climate-controlled cuvettes, while keeping plant temperature the same. Fruit phenotype was assessed at different levels of aggregation (whole fruit, cell and gene) between anthesis and breaker stage. We showed that: (1) final fruit fresh weight was larger in ‘Cappricia’ owing to more and larger pericarp cells, (2) heated fruits were smaller because their mesocarp cells were smaller than those of control fruits and (3) no significant differences in pericarp carbohydrate concentration were detected between heated and control fruits nor between cultivars at breaker stage. At the gene level, expression of cell division promoters (CDKB2, CycA1 and E2Fe-like) was higher while that of the inhibitory fw2.2 was lower in ‘Cappricia’. Fruit heating increased expression of fw2.2 and three cell division promoters (CDKB1, CDKB2 and CycA1). Expression of cell expansion genes did not corroborate cell size observations.
Effects of Irrigation in India on the Atmospheric Water Budget
Tuinenburg, O.A. ; Hutjes, R.W.A. ; Stacke, T. ; Wiltshire, A. ; Lucas-Picher, P. - \ 2014
Journal of Hydrometeorology 15 (2014)3. - ISSN 1525-755X - p. 1028 - 1050.
soil-moisture - part i - precipitation - climate - monsoon - scheme - models - cycle - parameterization - representation
The effect of large-scale irrigation in India on the moisture budget of the atmosphere was investigated using three regional climate models and one global climate model, all of which performed an irrigated run and a natural run without irrigation. Using a common irrigation map, year-round irrigation was represented by adding water to the soil moisture to keep it at 90% of the maximum soil moisture storage capacity, regardless of water availability. For two focus regions, the seasonal cycle of irrigation matched that of the reference dataset, but irrigation application varied between the models by up to 0.8 mm day(-1). Because of the irrigation, evaporation increased in all models, but precipitation decreased because of a strong decrease in atmospheric moisture convergence. A moisture tracking scheme was used to track individual evaporated moisture parcels through the atmosphere to determine where these lead to precipitation. Up to 35% of the evaporation moisture from the Ganges basin is recycling within the river basin. However, because of a decreased moisture convergence into the river basin, the total amount of precipitation in the Ganges basin decreases. Although a significant fraction of the evaporation moisture recycles within the river basin, the changes in large-scale wind patterns due to irrigation shift the precipitation from the eastern parts of India and Nepal to the northern and western parts of India and Pakistan. In these areas where precipitation increases, the relative precipitation increase is larger than the relative decrease in the areas where precipitation decreases. It is concluded 1) that the direct effects of irrigation on precipitation are small and are not uniform across the models; 2) that a fraction of up to 35% of any marginal evaporation increase (for example, due to irrigation) will recycle within the river basin; and 3) that when irrigation is applied on a large scale, the dominant effect will be a change in large-scale atmospheric flow that decreases precipitation in eastern India and increases it in western and northern India.
Carbon Sequestration in a Large Hydroelectric Reservoir: An Integrative Seismic Approach
Mendonca, R. ; Kosten, S. ; Sobek, S. ; Cole, J.J. ; Bastos, A.C. ; Albuquerque, A.L. ; Cardoso, S.J. ; Roland, F. - \ 2014
Ecosystems 17 (2014)3. - ISSN 1432-9840 - p. 430 - 441.
lake-sediments - organic-carbon - burial - cycle - stratigraphy - terrestrial - phosphorus - emission
Artificial reservoirs likely accumulate more carbon than natural lakes due to their unusually high sedimentation rates. Nevertheless, the actual magnitude of carbon accumulating in reservoirs is poorly known due to a lack of whole-system studies of carbon burial. We determined the organic carbon (OC) burial rate and the total OC stock in the sediments of a tropical hydroelectric reservoir by combining a seismic survey with sediment core sampling. Our data suggest that no sediment accumulation occurs along the margins of the reservoir and that irregular bottom morphology leads to irregular sediment deposition. Such heterogeneous sedimentation resulted in high spatial variation in OC burial-from 0 to 209 g C m(-2) y(-1). Based on a regression between sediment accumulation and OC burial rates (R (2) = 0.94), and on the mean reservoir sediment accumulation rate (0.51 cm y(-1), from the seismic survey), the whole-reservoir OC burial rate was estimated at 42.2 g C m(-2) y(-1). This rate was equivalent to 70% of the reported carbon emissions from the reservoir surface to the atmosphere and corresponded to a total sediment OC accumulation of 0.62 Tg C since the reservoir was created. The approach we propose here allows an inexpensive and integrative assessment of OC burial in reservoirs by taking into account the high degree of spatial variability and based on a single assessment. Because burial can be assessed shortly after the survey, the approach combining a seismic survey and coring could, if applied on a larger scale, contribute to a more complete estimate of carbon stocks in freshwater systems in a relatively short period of time.
Cell Turnover and Detritus Production in Marine Sponges from Tropical and Temperate Benthic Ecosystems
Alexander, B.E. ; Liebrand, K. ; Osinga, R. ; Geest, H.G. van der; Admiraal, W. ; Cleutjens, J.P.M. ; Schutte, B. ; Verheyen, F. ; Ribes, M. ; Loon, E. van; Goeij, J.M. de - \ 2014
PLoS ONE 9 (2014)10. - ISSN 1932-6203 - 11 p.
fresh-water sponge - stem-cells - ephydatia-fluviatilis - intestinal epithelium - tissue homeostasis - coral-reefs - in-vitro - demospongiae - cycle - population
This study describes in vivo cell turnover (the balance between cell proliferation and cell loss) in eight marine sponge species from tropical coral reef, mangrove and temperate Mediterranean reef ecosystems. Cell proliferation was determined through the incorporation of 5-bromo-2'-deoxyuridine (BrdU) and measuring the percentage of BrdU-positive cells after 6 h of continuous labeling (10 h for Chondrosia reniformis). Apoptosis was identified using an antibody against active caspase-3. Cell loss through shedding was studied quantitatively by collecting and weighing sponge-expelled detritus and qualitatively by light microscopy of sponge tissue and detritus. All species investigated displayed substantial cell proliferation, predominantly in the choanoderm, but also in the mesohyl. The majority of coral reef species (five) showed between 16.1±15.9% and 19.0±2.0% choanocyte proliferation (mean±SD) after 6 h and the Mediterranean species, C. reniformis, showed 16.6±3.2% after 10 h BrdU-labeling. Monanchora arbuscula showed lower choanocyte proliferation (8.1±3.7%), whereas the mangrove species Mycale microsigmatosa showed relatively higher levels of choanocyte proliferation (70.5±6.6%). Choanocyte proliferation in Haliclona vansoesti was variable (2.8–73.1%). Apoptosis was negligible and not the primary mechanism of cell loss involved in cell turnover. All species investigated produced significant amounts of detritus (2.5–18% detritus bodyweight-1·d-1) and cell shedding was observed in seven out of eight species. The amount of shed cells observed in histological sections may be related to differences in residence time of detritus within canals. Detritus production could not be directly linked to cell shedding due to the degraded nature of expelled cellular debris. We have demonstrated that under steady-state conditions, cell turnover through cell proliferation and cell shedding are common processes to maintain tissue homeostasis in a variety of sponge species from different ecosystems. Cell turnover is hypothesized to be the main underlying mechanism producing sponge-derived detritus, a major trophic resource transferred through sponges in benthic ecosystems, such as coral reefs.
Simulating the integrated summertime d14CO2 signature from anthropogenic emissions over Western Europe
Bozhinova, D.N. ; Molen, M.K. van der; Velde, I.R. van der; Krol, M.C. ; Laan, S. van der; Meijer, H.A.J. ; Peters, W. - \ 2014
Atmospheric Chemistry and Physics 14 (2014)14. - ISSN 1680-7316 - p. 7273 - 7290.
fossil-fuel co2 - carbon-dioxide - atmospheric co2 - field campaign - (co2)-c-14 observations - transport models - c-14 discharges - mixing ratios - radiocarbon - cycle
Radiocarbon dioxide (14CO2, reported in d14CO2) can be used to determine the fossil fuel CO2 addition to the atmosphere, since fossil fuel CO2 no longer contains any 14C. After the release of CO2 at the source, atmospheric transport causes dilution of strong local signals into the background and detectable gradients of d14CO2 only remain in areas with high fossil fuel emissions. This fossil fuel signal can moreover be partially masked by the enriching effect that anthropogenic emissions of 14CO2 from the nuclear industry have on the atmospheric d14CO2 signature. In this paper, we investigate the regional gradients in 14CO2 over the European continent and quantify the effect of the emissions from nuclear industry. We simulate the emissions and transport of fossil fuel CO2 and nuclear 14CO2 for Western Europe using the Weather Research and Forecast model (WRF-Chem) for a period covering 6 summer months in 2008. We evaluate the expected CO2 gradients and the resulting d14CO2 in simulated integrated air samples over this period, as well as in simulated plant samples. We find that the average gradients of fossil fuel CO2 in the lower 1200 m of the atmosphere are close to 15 ppm at a 12 km × 12 km horizontal resolution. The nuclear influence on d14CO2 signatures varies considerably over the domain and for large areas in France and the UK it can range from 20 to more than 500% of the influence of fossil fuel emissions. Our simulations suggest that the resulting gradients in d14CO2 are well captured in plant samples, but due to their time-varying uptake of CO 2, their signature can be different with over 3‰ from the atmospheric samples in some regions. We conclude that the framework presented will be well-suited for the interpretation of actual air and plant 14CO2 samples. © Author(s) 2014. CC Attribution 3.0 License.
Food choices, health and environment: Effects of cutting Europe's meat and dairy intake
Westhoek, H. ; Lesschen, J.P. ; Rood, T. ; Wagner, S. ; Marco, A. de; Murphy, D. ; Leip, A. ; Grinsven, H. van; Sutton, M.A. ; Oenema, O. - \ 2014
Global environmental change : human and policy dimensions 26 (2014). - ISSN 0959-3780 - p. 196 - 205.
greenhouse-gas emissions - livestock production - integrated assessment - nitrogen losses - recent trends - agriculture - cycle - consumption - cancer - sustainability
Western diets are characterised by a high intake of meat, dairy products and eggs, causing an intake of saturated fat and red meat in quantities that exceed dietary recommendations. The associated livestock production requires large areas of land and lead to high nitrogen and greenhouse gas emission levels. Although several studies have examined the potential impact of dietary changes on greenhouse gas emissions and land use, those on health, the agricultural system and other environmental aspects (such as nitrogen emissions) have only been studied to a limited extent. By using biophysical models and methods, we examined the large-scale consequences in the European Union of replacing 25–50% of animal-derived foods with plant-based foods on a dietary energy basis, assuming corresponding changes in production. We tested the effects of these alternative diets and found that halving the consumption of meat, dairy products and eggs in the European Union would achieve a 40% reduction in nitrogen emissions, 25–40% reduction in greenhouse gas emissions and 23% per capita less use of cropland for food production. In addition, the dietary changes would also lower health risks. The European Union would become a net exporter of cereals, while the use of soymeal would be reduced by 75%. The nitrogen use efficiency (NUE) of the food system would increase from the current 18% to between 41% and 47%, depending on choices made regarding land use. As agriculture is the major source of nitrogen pollution, this is expected to result in a significant improvement in both air and water quality in the EU. The resulting 40% reduction in the intake of saturated fat would lead to a reduction in cardiovascular mortality. These diet-led changes in food production patterns would have a large economic impact on livestock farmers and associated supply-chain actors, such as the feed industry and meat-processing sector.
Total carbon and nitrogen in the soils of the world
Batjes, N.H. - \ 2014
European Journal of Soil Science 65 (2014)1. - ISSN 1351-0754 - p. 10 - 21.
organic-carbon - storage - cycle
The soil is important in sequestering atmospheric CO2 and in emitting trace gases (e.g. CO2, CH4 and N2O) that are radiatively active and enhance the ‘greenhouse’ effect. Land use changes and predicted global warming, through their effects on net primary productivity, the plant community and soil conditions, may have important effects on the size of the organic matter pool in the soil and directly affect the atmospheric concentration of these trace gases. A discrepancy of approximately 350 × 1015¿g (or Pg) of C in two recent estimates of soil carbon reserves worldwide is evaluated using the geo-referenced database developed for the World Inventory of Soil Emission Potentials (WISE) project. This database holds 4353 soil profiles distributed globally which are considered to represent the soil units shown on a ½º latitude by ½º longitude version of the corrected and digitized 1¿:¿5¿M FAO–UNESCO Soil Map of the World. Total soil carbon pools for the entire land area of the world, excluding carbon held in the litter layer and charcoal, amounts to 2157–2293 Pg of C in the upper 100¿cm. Soil organic carbon is estimated to be 684–724 Pg of C in the upper 30¿cm, 1462–1548 Pg of C in the upper 100¿cm, and 2376–2456 Pg of C in the upper 200¿cm. Although deforestation, changes in land use and predicted climate change can alter the amount of organic carbon held in the superficial soil layers rapidly, this is less so for the soil carbonate carbon. An estimated 695–748 Pg of carbonate-C is held in the upper 100¿cm of the world's soils. Mean C : N ratios of soil organic matter range from 9.9 for arid Yermosols to 25.8 for Histosols. Global amounts of soil nitrogen are estimated to be 133–140 Pg of N for the upper 100¿cm. Possible changes in soil organic carbon and nitrogen dynamics caused by increased concentrations of atmospheric CO2 and the predicted associated rise in temperature are discussed.
Hydrological droughts in the 21st century, hotspots and uncertainties from a global multimodel ensemble experiment
Prudhomme, C. ; Giuntoli, L. ; Robinson, E.L. ; Clark, D.B. ; Arnell, N.W. ; Dankers, R. ; Fekete, B.M. ; Franssen, W.H.P. - \ 2014
Proceedings of the National Academy of Sciences of the United States of America 111 (2014)9. - ISSN 0027-8424 - p. 3262 - 3267.
climate-change - carbon-dioxide - elevated co2 - models - extremes - cycle - face
Increasing concentrations of greenhouse gases in the atmosphere are expected to modify the global water cycle with significant consequences for terrestrial hydrology. We assess the impact of climate change on hydrological droughts in a multimodel experiment including seven global impact models (GIMs) driven by bias-corrected climate from five global climate models under four representative concentration pathways (RCPs). Drought severity is defined as the fraction of land under drought conditions. Results show a likely increase in the global severity of hydrological drought at the end of the 21st century, with systematically greater increases for RCPs describing stronger radiative forcings. Under RCP8.5, droughts exceeding 40% of analyzed land area are projected by nearly half of the simulations. This increase in drought severity has a strong signal-to-noise ratio at the global scale, and Southern Europe, the Middle East, the Southeast United States, Chile, and South West Australia are identified as possible hotspots for future water security issues. The uncertainty due to GIMs is greater than that from global climate models, particularly if including a GIM that accounts for the dynamic response of plants to CO2 and climate, as this model simulates little or no increase in drought frequency. Our study demonstrates that different representations of terrestrial water-cycle processes in GIMs are responsible for a much larger uncertainty in the response of hydrological drought to climate change than previously thought. When assessing the impact of climate change on hydrology, it is therefore critical to consider a diverse range of GIMs to better capture the uncertainty.
Nitrogen Footprint in China: Food, Energy, and Nonfood Goods
Gu, B.J. ; Leach, A.M. ; Ma, L. ; Galloway, J.N. ; Chang, S.X. ; Ge, Y. ; Chang, J. - \ 2013
Environmental Science and Technology 47 (2013)16. - ISSN 0013-936X - p. 9217 - 9224.
ecological footprint - livestock production - reactive nitrogen - recent trends - systems - tracking - cycle
The nitrogen (N) footprint is a novel approach to quantify losses to the environment of reactive N (Nr; all species of N except N-2) derived from human activities. However, current N footprint models are difficult to apply to new countries due to the large data requirement, and sources of Nr included in calculating the N footprint are often incomplete. In this study, we comprehensively quantified the N footprint in China with an N mass balance approach. Results show that the per capita N footprint in China increased 68% between 1980 and 2008, from 19 to 32 kg N yr(-1). The Nr loss from the production and consumption of food was the largest component of the N footprint (70%) while energy and nonfood products made up the remainder in approximately equal portion in 2008. In contrast, in 1980, the food-related N footprint accounted for 86% of the overall N footprint, followed by nonfood products (8%) and energy (6%). The findings and methods of this study are generally comparable to that of the consumer-based analysis of the N-Calculator. This work provides policy makers quantitative information about the sources of China's N footprint and demonstrates the significant challenges in reducing Nr loss to the environment.
Feed-milk-manure nitrogen relationships in global dairy production systems
Powell, J.M. ; Macleod, M. ; Vellinga, Th.V. ; Opio, C. ; Falcucci, A. ; Tempio, G. ; Steinfeld, H. ; Gerber, P. - \ 2013
Livestock Science 152 (2013)2-3. - ISSN 1871-1413 - p. 261 - 272.
dietary-protein - nutrient management - use efficiency - urea nitrogen - farms - cows - excretion - cycle - performance - emissions
Nitrogen (N) inputs from fertilizer, biologically-fixed N, feed, and animal manure sustain productive agriculture. Agricultural systems are limited however in their ability to incorporate N into products, and environmental N losses may become local, regional and global concerns. The anticipated increases in global demand for food, especially for animal products, necessitate an urgent search for practices that enhance N use efficiency (NUE) and reduce environmental N loss. The objectives of this study were to determine feed-milk-manure N relationships for the global dairy herd, and to evaluate how well regional and production system determinations of these relationships correspond to measurements made under experimental conditions and on commercial dairy farms. Data on dairy cattle populations, feed and milk production from 142 countries were used in a Life Cycle Assessment (LCA) model to determine dry matter intake (DMI), N intake (NI), the percentage of NI secreted as milk N (NUE-milk), the percent of NI used by the whole-herd (NUE-herd), and manure N excretion (Nex). On a global basis, an average lactating cow weighs approximately 420 kg; per animal unit (AU = 1000 kg live weight) daily DMI and NI are 21.0 kg and 477 g, respectively; annual milk production is 5000 kg/AU; and NUE-milk and NUE-herd are 16.0% and 15.6%, respectively. Approximately 37% of global lactating cows have NUE-milk of <10% and these low efficient cows account for 10% of the milk production and 33% of Nex globally. Approximately 30% of global lactating cows have NUE-milk between 21% and 25% and these cows account for 53% of the milk production and 35% of Nex globally. Estimates of NUE-milk and Nex corresponded well to measurements under experimental and commercial farm conditions. Study determinations of Nex were however 3-50% lower than IPCC Tier 1 values of Nex for Africa, Middle East, Latin America and Asia. The apparent accuracy of LCA model calculations of Nex should enhance regional, production system and global determinations of dairy Nex loss during collection, storage, and land application, and the amounts of Nex actually recycled through crops and pastures. Published by Elsevier B.V.
Biosphere model simulations of interannual variability in terrestrial 13C/12C exchange.
Velde, I.R. van der; Miller, J.B. ; Schaefer, K. ; Masarie, K.A. ; Denning, S. ; White, J.W.C. ; Krol, M.C. ; Peters, W. ; Tans, P.P. - \ 2013
Global Biogeochemical Cycles 27 (2013)3. - ISSN 0886-6236 - p. 637 - 649.
carbon-isotope discrimination - ocean co2 sink - stomatal conductance - c-13 discrimination - atmospheric co2 - cycle - climate - fires - photosynthesis - assimilation
Previous studies suggest that a large part of the variability in the atmospheric ratio of (CO2)-C-13/(12)CO(2)originates from carbon exchange with the terrestrial biosphere rather than with the oceans. Since this variability is used to quantitatively partition the total carbon sink, we here investigate the contribution of interannual variability (IAV) in biospheric exchange to the observed atmospheric C-13 variations. We use the Simple Biosphere - Carnegie-Ames-Stanford Approach biogeochemical model, including a detailed isotopic fractionation scheme, separate C-12 and C-13 biogeochemical pools, and satellite-observed fire disturbances. This model of (CO2)-C-12 and (CO2)-C-13 thus also produces return fluxes of (13)CO(2)from its differently aged pools, contributing to the so-called disequilibrium flux. Our simulated terrestrial C-13 budget closely resembles previously published model results for plant discrimination and disequilibrium fluxes and similarly suggests that variations in C-3 discrimination and year-to-year variations in C(3)and C-4 productivity are the main drivers of their IAV. But the year-to-year variability in the isotopic disequilibrium flux is much lower (1 sigma=1.5PgCyr(-1)) than required (12.5PgCyr(-1)) to match atmospheric observations, under the common assumption of low variability in net ocean CO2 fluxes. This contrasts with earlier published results. It is currently unclear how to increase IAV in these drivers suggesting that SiBCASA still misses processes that enhance variability in plant discrimination and relative C-3/C(4)productivity. Alternatively, C-13 budget terms other than terrestrial disequilibrium fluxes, including possibly the atmospheric growth rate, must have significantly different IAV in order to close the atmospheric C-13 budget on a year-to-year basis.
Global atmospheric carbon budget: results from an ensemble of atmospheric CO2 inversions.
Peylin, P. ; Law, R.M. ; Gurney, K.R. ; Chevallier, F. ; Jacobsen, A.R. ; Maki, T. ; Niwa, Y. ; Patra, P.K. ; Peters, W. ; Rayner, P.J. ; Rödenbeck, C. ; Laan-Luijkx, I.T. van der; Zhang, X. - \ 2013
Biogeosciences 10 (2013). - ISSN 1726-4170 - p. 6699 - 6720.
interannual variability - dioxide exchange - transport model - sinks - fluxes - sensitivity - ocean - land - cycle - emissions
Atmospheric CO2 inversions estimate surface carbon fluxes from an optimal fit to atmospheric CO2 measurements, usually including prior constraints on the flux estimates. Eleven sets of carbon flux estimates are compared, generated by different inversions systems that vary in their inversions methods, choice of atmospheric data, transport model and prior information. The inversions were run for at least 5 yr in the period between 1990 and 2010. Mean fluxes for 2001-2004, seasonal cycles, interannual variability and trends are compared for the tropics and northern and southern extra-tropics, and separately for land and ocean. Some continental/basin-scale subdivisions are also considered where the atmospheric network is denser. Four-year mean fluxes are reasonably consistent across inversions at global/latitudinal scale, with a large total (land plus ocean) carbon uptake in the north (-3.4 Pg C yr(-1) (+/- 0.5 Pg C yr(-1) standard deviation), with slightly more uptake over land than over ocean), a significant although more variable source over the tropics (1.6 +/- 0.9 Pg C yr(-1)) and a compensatory sink of similar magnitude in the south (-1.4 +/- 0.5 Pg C yr(-1)) corresponding mainly to an ocean sink. Largest differences across inversions occur in the balance between tropical land sources and southern land sinks. Interannual variability (IAV) in carbon fluxes is larger for land than ocean regions (standard deviation around 1.06 versus 0.33 Pg C yr(-1) for the 1996-2007 period), with much higher consistency among the inversions for the land. While the tropical land explains most of the IAV (standard deviation similar to 0.65 Pg C yr(-1)), the northern and southern land also contribute (standard deviation similar to 0.39 Pg C yr(-1)). Most inversions tend to indicate an increase of the northern land carbon uptake from late 1990s to 2008 (around 0.1 Pg C yr(-1)), predominantly in North Asia. The mean seasonal cycle appears to be well constrained by the atmospheric data over the northern land (at the continental scale), but still highly dependent on the prior flux seasonality over the ocean. Finally we provide recommendations to interpret the regional fluxes, along with the uncertainty estimates.
The stable isotopic signature of biologically produced molecular hydrogen (H-2)
Walter, S. ; Laukenmann, S. ; Stams, A.J.M. ; Vollmer, M.K. ; Gleixner, G. ; Rockmann, T. - \ 2012
Biogeosciences 9 (2012)10. - ISSN 1726-4170 - p. 4115 - 4123.
atmospheric hydrogen - stratosphere - economy - budget - model - cycle - air - fractionation - troposphere - photolysis
Biologically produced molecular hydrogen (H-2) is characterised by a very strong depletion in deuterium. Although the biological source to the atmosphere is small compared to photochemical or combustion sources, it makes an important contribution to the global isotope budget of H-2. Large uncertainties exist in the quantification of the individual production and degradation processes that contribute to the atmospheric budget, and isotope measurements are a tool to distinguish the contributions from the different sources. Measurements of delta D from the various H-2 sources are scarce and for biologically produced H-2 only very few measurements exist. Here the first systematic study of the isotopic composition of biologically produced H-2 is presented. In a first set of experiments, we investigated delta D of H-2 produced in a biogas plant, covering different treatments of biogas production. In a second set of experiments, we investigated pure cultures of several H-2 producing microorganisms such as bacteria or green algae. A Keeling plot analysis provides a robust overall source signature of delta D = -712 parts per thousand (+/-13 parts per thousand) for the samples from the biogas reactor (at 38 degrees C, delta D-H2O = +73.4 parts per thousand), with a fractionation constant epsilon H-2-H2O of -689 parts per thousand (+/-20 parts per thousand) between H-2 and the water. The five experiments using pure culture samples from different microorganisms give a mean source signature of delta D = -728 parts per thousand (+/-28 parts per thousand), and a fractionation constant epsilon H-2-H2O of -711 parts per thousand (+/-34 parts per thousand) between H-2 and the water. The results confirm the massive deuterium depletion of biologically produced H-2 as was predicted by the calculation of the thermodynamic fractionation factors for hydrogen exchange between H-2 and water vapour. Systematic errors in the isotope scale are difficult to assess in the absence of international standards for delta D of H-2. As expected for a thermodynamic equilibrium, the fractionation factor is temperature dependent, but largely independent of the substrates used and the H-2 production conditions. The equilibrium fractionation coefficient is positively correlated with temperature and we measured a rate of change of 2.3 parts per thousand/degrees C between 45 degrees C and 60 degrees C, which is in general agreement with the theoretical prediction of 1.4%/degrees C. Our best experimental estimate for epsilon H-2-H2O at a temperature of 20 degrees C is -731 parts per thousand (+/-20 parts per thousand) for biologically produced H-2. This value is close to the predicted value of -722 parts per thousand, and we suggest using these values in future global H-2 isotope budget calculations and models with adjusting to regional temperatures for calculating delta D values.
Methane. A review
Amstel, A.R. van - \ 2012
Journal of integrative Environmental Sciences 9 (2012). - ISSN 1943-815X - p. 5 - 30.
zoom model tm5 - atmospheric methane - nitrous-oxide - gas emissions - climate - cycle - ch4 - inventories - balance - plants
Earth's atmosphere is changing because of emissions of pollutants and greenhouse gases. Carbon dioxide emissions are important and result in half of the warming of the atmosphere. Pollutants from burning like black carbon (soot), nitrogen oxides and sulphur oxides have adverse health effects and result in cooling. Pollutants have long masked the greenhouse effect, but improved air quality through reductions in air pollutants increase the warming. Atmospheric processes are intricately linked. Methane is central in all atmospheric chemistry. Methane is also important as a greenhouse gas. Although carbon dioxide should be reduced to prevent global warming, it is relatively cheap to reduce the non-CO2 greenhouse gases such as methane at the same time. Methane's concentration in the troposphere, after a long period of stabiliszation, is rising again since 2006. Here I will give a review on methane, its atmospheric chemistry, its emission sources and global budget.
Hydroelectric carbon sequestration : Correspondence
Mendonca, R. ; Kosten, S. ; Sobek, S. ; Barros, N. ; Cole, J.J. ; Tranvik, L. ; Roland, F. - \ 2012
Nature Geoscience 5 (2012)12. - ISSN 1752-0894 - p. 838 - 840.
lake-sediments - burial - reservoirs - cycle
A bistable circuit involving SCARECROW-RETINOBLASTOMA integrates cues to inform asymmetic stem cell division
Cruz-Ramirez, A. ; Diaz-Trivino, S. ; Blilou, I. ; Benjamins, R. ; Long, Y. ; Scheres, B.J.G. - \ 2012
Cell 150 (2012)5. - ISSN 0092-8674 - p. 1002 - 1015.
protein-protein interactions - arabidopsis root-meristem - tumor-suppressor - split luciferase - auxin transport - cycle - gene - differentiation - plants - growth
In plants, where cells cannot migrate, asymmetric cell divisions (ACDs) must be confined to the appropriate spatial context. We investigate tissue-generating asymmetric divisions in a stem cell daughter within the Arabidopsis root. Spatial restriction of these divisions requires physical binding of the stem cell regulator SCARECROW (SCR) by the RETINOBLASTOMA-RELATED (RBR) protein. In the stem cell niche, SCR activity is counteracted by phosphorylation of RBR through a cyclinD6;1-CDK complex. This cyclin is itself under transcriptional control of SCR and its partner SHORT ROOT (SHR), creating a robust bistable circuit with either high or low SHR-SCR complex activity. Auxin biases this circuit by promoting CYCD6;1 transcription. Mathematical modeling shows that ACDs are only switched on after integration of radial and longitudinal information, determined by SHR and auxin distribution, respectively. Coupling of cell-cycle progression to protein degradation resets the circuit, resulting in a “flip flop” that constrains asymmetric cell division to the stem cell region.
Early warning of climate tipping points from critical slowing down: comparing methods to improve robustness
Lenton, T.M. ; Livina, V. ; Dakos, V. ; Nes, E.H. van; Scheffer, M. - \ 2012
Philosophical Transactions of the Royal Society. Series A, Mathematical, physical and engineering sciences 370 (2012). - ISSN 1364-503X - p. 1185 - 1204.
catastrophic shifts - system - signal - time - bifurcations - antarctica - ecosystems - states - cycle
We address whether robust early warning signals can, in principle, be provided before a climate tipping point is reached, focusing on methods that seek to detect critical slowing down as a precursor of bifurcation. As a test bed, six previously analysed datasets are reconsidered, three palaeoclimate records approaching abrupt transitions at the end of the last ice age and three models of varying complexity forced through a collapse of the Atlantic thermohaline circulation. Approaches based on examining the lag-1 autocorrelation function or on detrended fluctuation analysis are applied together and compared. The effects of aggregating the data, detrending method, sliding window length and filtering bandwidth are examined. Robust indicators of critical slowing down are found prior to the abrupt warming event at the end of the Younger Dryas, but the indicators are less clear prior to the Bølling-Allerød warming, or glacial termination in Antarctica. Early warnings of thermohaline circulation collapse can be masked by inter-annual variability driven by atmospheric dynamics. However, rapidly decaying modes can be successfully filtered out by using a long bandwidth or by aggregating data. The two methods have complementary strengths and weaknesses and we recommend applying them together to improve the robustness of early warnings