Walsh B.J., Rydzak F., Palazzo A., Kraxner F., Herrero M., Schenk P.M., Ciais P., Janssens I.A., Peñuelas J., Niederl-Schmidinger A., Obersteiner M. (2015) New feed sources key to ambitious climate targets. Carbon Balance and Management. 10: 0-0.LinkDoi: 10.1186/s13021-015-0040-7
Net carbon sinks capable of avoiding dangerous perturbation of the climate system and preventing ocean acidification have been identified, but they are likely to be limited by resource constraints (Nature 463:747-756, 2010). Land scarcity already creates tension between food security and bioenergy production, and this competition is likely to intensify as populations and the effects of climate change expand. Despite research into microalgae as a next-generation energy source, the land-sparing consequences of alternative sources of livestock feed have been overlooked. Here we use the FeliX model to quantify emissions pathways when microalgae is used as a feedstock to free up to 2 billion hectares of land currently used for pasture and feed crops. Forest plantations established on these areas can conceivably meet 50 % of global primary energy demand, resulting in emissions mitigation from the energy and LULUC sectors of up to 544 ± 107 PgC by 2100. Further emissions reductions from carbon capture and sequestration (CCS) technology can reduce global atmospheric carbon concentrations close to preindustrial levels by the end of the present century. Though previously thought unattainable, carbon sinks and climate change mitigation of this magnitude are well within the bounds of technological feasibility. © 2015 Walsh et al.
Wang R., Balkanski Y., Bopp L., Aumont O., Boucher O., Ciais P., Gehlen M., Peñuelas J., Ethé C., Hauglustaine D., Li B., Liu J., Zhou F., Tao S. (2015) Influence of anthropogenic aerosol deposition on the relationship between oceanic productivity and warming. Geophysical Research Letters. 42: 10745-10754.LinkDoi: 10.1002/2015GL066753
Satellite data and models suggest that oceanic productivity is reduced in response to less nutrient supply under warming. In contrast, anthropogenic aerosols provide nutrients and exert a fertilizing effect, but its contribution to evolution of oceanic productivity is unknown. We simulate the response of oceanic biogeochemistry to anthropogenic aerosols deposition under varying climate from 1850 to 2010. We find a positive response of observed chlorophyll to deposition of anthropogenic aerosols. Our results suggest that anthropogenic aerosols reduce the sensitivity of oceanic productivity to warming from -15.2 ± 1.8 to -13.3 ± 1.6 Pg C yr-1 °C-1 in global stratified oceans during 1948-2007. The reducing percentage over the North Atlantic, North Pacific, and Indian Oceans reaches 40, 24, and 25%, respectively. We hypothesize that inevitable reduction of aerosol emissions in response to higher air quality standards in the future might accelerate the decline of oceanic productivity per unit warming. © 2015. American Geophysical Union. All Rights Reserved.
Wang R., Balkanski Y., Boucher O., Bopp L., Chappell A., Ciais P., Hauglustaine D., Penuelas J., Tao S. (2015) Sources, transport and deposition of iron in the global atmosphere. Atmospheric Chemistry and Physics. 15: 6247-6270.LinkDoi: 10.5194/acp-15-6247-2015
Atmospheric deposition of iron (Fe) plays an important role in controlling oceanic primary productivity. However, the sources of Fe in the atmosphere are not well understood. In particular, the combustion sources of Fe and the subsequent deposition to the oceans have been accounted for in only few ocean biogeochemical models of the carbon cycle. Here we used a mass-balance method to estimate the emissions of Fe from the combustion of fossil fuels and biomass by accounting for the Fe contents in fuel and the partitioning of Fe during combustion. The emissions of Fe attached to aerosols from combustion sources were estimated by particle size, and their uncertainties were quantified by a Monte Carlo simulation. The emissions of Fe from mineral sources were estimated using the latest soil mineralogical database to date. As a result, the total Fe emissions from combustion averaged for 1960-2007 were estimated to be 5.3 Tg yr-1 (90% confidence of 2.3 to 12.1). Of these emissions, 1, 27 and 72% were emitted in particles 10 μm (PM> 10), respectively, compared to a total Fe emission from mineral dust of 41.0 Tg yr-1 in a log-normal distribution with a mass median diameter of 2.5 μm and a geometric standard deviation of 2. For combustion sources, different temporal trends were found in fine and medium-to-coarse particles, with a notable increase in Fe emissions in PM1 since 2000 due to an increase in Fe emission from motor vehicles (from 0.008 to 0.0103 Tg yr-1 in 2000 and 2007, respectively). These emissions have been introduced in a global 3-D transport model run at a spatial resolution of 0.94° latitude by 1.28° longitude to evaluate our estimation of Fe emissions. The modelled Fe concentrations as monthly means were compared with the monthly (57 sites) or daily (768 sites) measured concentrations at a total of 825 sampling stations. The deviation between modelled and observed Fe concentrations attached to aerosols at the surface was within a factor of 2 at most sampling stations, and the deviation was within a factor of 1.5 at sampling stations dominated by combustion sources. We analysed the relative contribution of combustion sources to total Fe concentrations over different regions of the world. The new mineralogical database led to a modest improvement in the simulation relative to station data even in dust-dominated regions, but could provide useful information on the chemical forms of Fe in dust for coupling with ocean biota models. We estimated a total Fe deposition sink of 8.4 Tg yr-1 over global oceans, 7% of which originated from the combustion sources. Our central estimates of Fe emissions from fossil fuel combustion (mainly from coal) are generally higher than those in previous studies, although they are within the uncertainty range of our estimates. In particular, the higher than previously estimated Fe emission from coal combustion implies a larger atmospheric anthropogenic input of soluble Fe to the northern Atlantic and northern Pacific Oceans, which is expected to enhance the biological carbon pump in those regions. © 2015 Author(s).
Wang R., Balkanski Y., Boucher O., Ciais P., Peñuelas J., Tao S. (2015) Significant contribution of combustion-related emissions to the atmospheric phosphorus budget. Nature Geoscience. 8: 48-54.LinkDoi: 10.1038/ngeo2324
Atmospheric phosphorus fertilizes plants and contributes to Earth's biogeochemical phosphorus cycle. However, calculations of the global budget of atmospheric phosphorus have been unbalanced, with global deposition exceeding estimated emissions from dust and sea-salt transport, volcanic eruptions, biogenic sources and combustion of fossil fuels, biofuels and biomass, the latter of which thought to contribute about 5% of total emissions. Here we use measurements of the phosphorus content of various fuels and estimates of the partitioning of phosphorus during combustion to calculate phosphorus emissions to the atmosphere from all combustion sources. We estimate combustion-related emissions of 1.8 Tg P yr-1, which represent over 50% of global atmospheric sources of phosphorus. Using these estimates in atmospheric transport model simulations, we find that the total global emissions of atmospheric phosphorus (3.5 Tg P yr-1) translate to a depositional sink of 2.7 Tg P yr-1 over land and 0.8 Tg P yr-1 over the oceans. The modelled spatial patterns of phosphorus deposition agree with observations from globally distributed measurement stations, and indicate a near balance of the phosphorus budget. Our finding suggests that the perturbation of the global phosphorus cycle by anthropogenic emissions is larger thanpreviously thought. © 2014 Macmillan Publishers Limited. All rights reserved.
Wang W., Lai D.Y.F., Sardans J., Wang C., Datta A., Pan T., Zeng C., Bartrons M., Penuelas J. (2015) Rice straw incorporation affects global warming potential differently in early vs. late cropping seasons in Southeastern China. Field Crops Research. 181: 42-51.LinkDoi: 10.1016/j.fcr.2015.07.007
Paddy fields are a major global anthropogenic source of methane (CH4) and nitrous oxide (N2O), which are very potent greenhouse gases. China has the second largest area under rice cultivation, so developing valid and reliable methods for reducing emissions of greenhouse gases while sustaining crop productivity in paddy fields is of paramount importance. We examined the effects of applying straw, a residual product of rice cultivation containing high amounts of carbon and nutrients, to rice crops during both an early crop season (5 April - 25 July 2012) and a late crop season (1 August - 6 November 2012) on CH4 and N2O emissions in a subtropical paddy field in southeastern China. CH4 fluxes had two seasonal peaks, on 5 May and 28 June, in the early crop but only one peak, on 13 August, in the late crop, which could be attributed to the lower temperatures after the final tillering stage in the late crop. Straw application significantly increased mean CH4 cumulative production (gm-2) relative to the control in the late crop (37.3 vs. 8.34mgm-2, P 0.05). The application of straw significantly increased N2O cumulative production relative to the control in the late crop (75.9 vs. 43.4μgm-2h-1) but decreased N2O cumulative production by over 43% in the early crop (15.60 vs. 27.27μgm-2h-1) (P
Wang W., Sardans J., Lai D.Y.F., Wang C., Zeng C., Tong C., Liang Y., Penuelas J. (2015) Effects of steel slag application on greenhouse gas emissions and crop yield over multiple growing seasons in a subtropical paddy field in China. Field Crops Research. 171: 146-156.LinkDoi: 10.1016/j.fcr.2014.10.014
Asia is responsible for over 90% of the world's rice production and hence plays a key role in safeguarding food security. With China being one of the major global producers and consumers of rice, achieving a sustainable balance in maximizing crop productivity and minimizing greenhouse gas emissions from paddy fields in this country becomes increasingly important. This study examined the effects of applying steel slag, a residual product derived from the steel industry, on crop yield and CH4 and N2O emissions over multiple growing seasons in a Chinese subtropical paddy field. Average CH4 emission was considerably higher during the periods of rice crop growth compared to that during the periods of fallowing and vegetable crop growth, regardless of the amount of steel slag applied. When compared to the controls, significantly lower mean emissions of CH4 (1.03 vs. 2.34mgm-2h-1) and N2O (0.41 vs. 32.43μgm-2h-1) were obtained in plots with slag addition at a rate of 8Mgha-1 over the study period. The application of slag at 8Mgha-1 increased crop yields by 4.2 and 9.1% for early and late rice crops, respectively, probably due to the higher availability of inorganic nutrients such as silicates and calcium from the slag. Slag addition had no significant effect on the concentrations of heavy metals in either the soil or the rice grains, although a slight increase in the levels of manganese and cobalt in the soil and a decrease in the levels of manganese and zinc in the rice grains were observed. Our results demonstrate the potential of steel slag as a soil amendment in enhancing crop yield and reducing greenhouse gas emissions in subtropical paddy fields in China, while posing no adverse short-term impacts on the concentrations of heavy metals in the soil or the rice grains. However, long-term implications of this management practice and the cost/benefit remain unknown, so further studies to assess the suitability at large scale are warranted. © 2014 Elsevier B.V.
Wang W., Wang C., Sardans J., Min Q., Zeng C., Tong C., Penuelas J. (2015) Agricultural land use decouples soil nutrient cycles in a subtropical riparian wetland in China. Catena. 133: 171-178.LinkDoi: 10.1016/j.catena.2015.05.003
We examined the impact of human changes in land use on the concentrations and stoichiometric relationships among soil carbon (C), nitrogen (N), phosphorus (P) and potassium (K) in a Phragmites australis riparian wetland (Minjiang River estuary, China). We compared a natural (unaltered) wetland with five altered land uses: intertidal mudflat culture and vegetable, flower, fruit and rice cultivations. All these land uses decreased C, N and K soil concentrations relative to those in the P. australis wetland. The close relationship between total soil C and N concentrations, under all land uses, suggested that N was the most limiting nutrient in these wetlands. The lower N concentrations, despite the use of N fertilizers, indicated the difficulty of avoiding N limitation in the agricultural land. Croplands, except rice cultivation, had lower soil N:P ratios than the original P. australis wetland, consistent with the tendency of favoring species adapted to high rates of growth (low N:P ratio). The release of soil C was less and the soil C:N and C:P ratios higher in the natural P. australis riparian wetland than in the croplands, whereas C storage was more similar. The levels of soil C storage were generally opposite to those of C release, indicating that C release by respiration was the most important factor controlling C storage. Cropland soil management promotes faster nutrient and C cycles and changes in soil nutrient stoichiometry. These impacts can further hinder the regeneration of natural vegetation by nutrient imbalances and increase C-cycling and C emissions. © 2015 Elsevier B.V.
Wang W., Wang C., Sardans J., Tong C., Jia R., Zeng C., Penuelas J. (2015) Flood regime affects soil stoichiometry and the distribution of the invasive plants in subtropical estuarine wetlands in China. Catena. 128: 144-154.LinkDoi: 10.1016/j.catena.2015.01.017
Projections of climate change impacts over the coming decades suggest that rising sea levels will flood coastal wetlands, moving the range of wetlands inland from the current coastline. The intensity of flooding in wetland areas will thus increase, with corresponding impacts on soil properties and coastal ecosystems. We studied the impacts of two levels of water inundation on the concentration and stoichiometry of soil carbon, nitrogen, phosphorus and sulfur in areas dominated by the native C3 species Scirpus triqueter L., the native C4 species Cyperus malaccensis var. brevifolius Boecklr. and the invasive Gramineae C3 species Phragmites australis (Cav.) Trin. ex Steud in the Shanyutan wetland areas of the Minjiang River estuary in China. Comparison of the communities dominated by these three species in high- and low-water flood habitats showed that flooding enhanced anaerobiosis and salinity and altered the carbon and nitrogen plant-soil cycles. Higher flooding favored the invasive species more than the two native species. The invasive P. australis accumulated more carbon (65% increase in aboveground biomass), and took up more nitrogen under high flooding than did C. malaccensis and S. triqueter. The more conservative use of soil resources, particularly the limiting nutrient N, appeared to underlie the higher capacity of the invasive species to tolerate higher flooding intensity. Increases in flooding may thus enhance the success and expansion of the invasive P. australis to the detriment of the native plant species in these Chinese wetlands. © 2015 Elsevier B.V.
Wang W.-Q., Sardans J., Zeng C.-S., Tong C., Wang C., Peñuelas J. (2015) Impact of Plant Invasion and Increasing Floods on Total Soil Phosphorus and its Fractions in the Minjiang River Estuarine Wetlands, China. Wetlands. : 0-0.LinkDoi: 10.1007/s13157-015-0712-9
Plant invasion and increased flooding intensity projected by climate change models can change the soil capacity of marine wetland to store P. This is a key question to the nutrient balances and eutrophication processes of coastal areas, especially in China coastal area that is receiving the freshwaters of a country in fast economical developing process. We studied the impact of changes in flooding intensity and plant invasion on total soil-P concentrations in the Minjiang River estuarine wetland. Flooding had a weak positive effect on soil P-fractions concentrations, but this effect was largely counteracted by the negative effect of salinity. Soil clay concentration and pH, both of which were related more with species community composition than with flooding intensity, were directly related to the P-fraction concentrations. The replacement of the native mangrove community by the invasive plant Phragmites australis was related to a decrease in the soil capacity to store P. A suitable management to maintain this wetland area in optimum conditions to act as a natural eutrophication buffer should tend to favor mangrove communities in the new areas that reach more than 220 days y-1 of flooding, and a combination of the three tall-grasses communities below this level of flooding. © 2015 Society of Wetland Scientists
Wang W.-Q., Wang C., Sardans J., Zeng C.-S., Tong C., Penuelas J. (2015) Plant invasive success associated with higher N-use efficiency and stoichiometric shifts in the soil–plant system in the Minjiang River tidal estuarine wetlands of China. Wetlands Ecology and Management. : 0-0.LinkDoi: 10.1007/s11273-015-9425-3
The tidal estuarine wetlands of China are rich in plant diversity, but several human-driven processes, such as species invasion, can affect the biogeochemical cycles of these ecosystems, and by changing soil conditions can inhibit the regeneration of native vegetation. We seasonally analyzed the carbon (C), nitrogen (N) and phosphorus (P) concentrations in soils and in leaves, stems and roots of the invasive species Spartina alterniflora and of the native species Cyperus malaccensis var. brevifolius Boeckeler. This latter species was analyzed both in natural non-invaded stands and in stands that had been invaded by Spartina but from which it had been removed and replaced by Cyperus. The aim was to investigate the effect of plant invasion, subsequent removal and replanting with a native species on C, N and P stoichiometry of the plant–soil system in the tidal wetlands of the Minjiang River. C and N concentrations averaged across seasons did not differ significantly among the plant species. P concentration was lower in the stems of Spartina than in the stems of the native species Cyperus but was not significantly different in the roots of the two species. The soil C and N concentrations were higher in the Spartina stand than in the Cyperus stand, whereas the soil P concentrations were not significantly different. The invasive species had a higher N-resorption capacity, N:P ratios in stem and roots, biomass, absolute growth and biomass N and had a lower relative growth rate and litter production than the native species. After the removal of the invasive plants, the regenerating native plants have a higher capacity to resorb N and lower relative growth rates. All these traits show that a conservative strategy and a high N-use efficiency and internal plant control of the N in the ecosystem underlie the invasive success of Spartina in this N-limited wetland. Relative growth rate was associated with lower plant N:P ratios, whereas absolute growth rate was associated with higher nutrient-use efficiency and lower C and N turnover and storage capacities in the biomass. Changes in soil properties produced by the establishment of an invasive plant can condition the later regeneration of native plants. © 2015 Springer Science+Business Media Dordrecht
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