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Spatial boundary of urban ‘acid islands’ in China
Du, E. ; Vries, W. de; Liu, X. ; Fang, J. ; Galloway, J.N. ; Jiang, Y. - \ 2015
Scientific Reports 5 (2015). - ISSN 2045-2322 - 9 p.
atmospheric deposition - nitrogen deposition - air-pollution - soil acidification - emissions - canopy - forest - rain - ecosystems - cities
Elevated emissions of sulfur dioxide, nitrogen oxides and ammonia in China have resulted in high levels of sulfur and nitrogen deposition, being contributors to soil acidification, especially in and near large cities. However, knowledge gaps still exist in the way that large cities shape spatial patterns of acid deposition. Here, we assessed the patterns of pH, sulfate, nitrate and ammonium in bulk precipitation and throughfall in southern China’s forests by synthesizing data from published literature. Concentrations and fluxes of sulfate, nitrate and ammonium in bulk precipitation and throughfall exhibited a power-law increase with a closer distance to the nearest large cities, and accordingly pH showed a logarithmic decline. Our findings indicate the occurrence of urban ‘acid islands’ with a critical radius of approximately 70¿km in southern China, receiving potential acid loads of more than 2 keq ha-1 yr-1. These urban acid islands covered an area of 0.70¿million km2, accounting for nearly 30% of the land area in southern China. Despite a significant capacity to neutralize acids in precipitation, our analysis highlights a substantial contribution of ammonium to potential acid load. Our results suggest a joint control on emissions of multiple acid precursors from urban areas in southern China
Inorganic nitrogen deposition in China's forests: Status and characteristics
Du, E. ; Jiang, Y. ; Fang, J. ; Vries, W. de - \ 2014
Atmospheric Environment 98 (2014). - ISSN 1352-2310 - p. 474 - 482.
atmospheric deposition - canopy uptake - throughfall measurements - ammonia emissions - reduced nitrogen - bulk deposition - wet deposition - air-pollution - higher-plants - transport
Nitrogen (N) deposition in China has been dramatically enhanced by anthropogenic emissions and has aroused great concerns of its impacts on forest ecosystems. This study synthesized data on ammonium (NH4+) and nitrate (NO3-) contents in bulk precipitation and throughfall from 38 forest stands in published literature to assess the status and characteristics of N deposition to typical forests in China between 1995 and 2010. Our results showed that ammonium dominated N deposition in this period, with a mean NH4+–N:NO3-–N ratio of ~2.5 in bulk deposition and throughfall. Mean throughfall N deposition in China's forests was as high as 14.0 kg N ha-1 yr-1 for ammonium, 5.5 kg N ha-1 yr-1 for nitrate and 21.5 kg N ha-1 yr-1 for total inorganic N (TIN), respectively. Mean bulk deposition was 9.4 kg N ha-1 yr-1 for ammonium, 3.9 kg N ha-1 yr-1 for nitrate and 14.0 kg N ha-1 yr-1 for TIN, respectively. Canopy captured dry deposition, calculated as the difference between throughfall and bulk deposition, was thus approximately half of the bulk deposition. Spatial patterns of N deposition were in accordance with our urban hotspot hypothesis, showing a strong power-law reduction of ammonium with increasing distance to large cities but only slightly lower nitrate deposition. Our results suggest that high N deposition, especially of ammonium, exceeds critical N loads for large areas of China's forests.
Driving factors behind the eutrophication signal in understorey plant communities of deciduous temperate forests
Verheyen, K. ; Baeten, L. ; Frenne, P. De; Bernhardt-Römermann, M. ; Brunet, J. ; Cornelis, J. ; Decocq, G. ; Eriksson, O. ; Dierschke, H. ; Hommel, P.W.F.M. - \ 2012
Journal of Ecology 100 (2012)2. - ISSN 0022-0477 - p. 352 - 365.
coppice-with-standards - ellenberg indicator values - ground-layer vegetation - white-tailed deer - nitrogen deposition - leaf-litter - species richness - atmospheric deposition - soil acidification - field-measurements
1. Atmospheric nitrogen (N) deposition is expected to change forest understorey plant community composition and diversity, but results of experimental addition studies and observational studies are not yet conclusive. A shortcoming of observational studies, which are generally based on resurveys or sampling along large deposition gradients, is the occurrence of temporal or spatial confounding factors. 2. We were able to assess the contribution of N deposition versus other ecological drivers on forest understorey plant communities by combining a temporal and spatial approach. Data from 1205 (semi-)permanent vegetation plots taken from 23 rigorously selected understorey resurvey studies along a large deposition gradient across deciduous temperate forest in Europe were compiled and related to various local and regional driving factors, including the rate of atmospheric N deposition, the change in large herbivore densities and the change in canopy cover and composition. 3. Although no directional change in species richness occurred, there was considerable floristic turnover in the understorey plant community and a shift in species composition towards more shade-tolerant and nutrient-demanding species. However, atmospheric N deposition was not important in explaining the observed eutrophication signal. This signal seemed mainly related to a shift towards a denser canopy cover and a changed canopy species composition with a higher share of species with more easily decomposed litter. 4. Synthesis. Our multi-site approach clearly demonstrates that one should be cautious when drawing conclusions about the impact of atmospheric N deposition based on the interpretation of plant community shifts in single sites or regions due to other, concurrent, ecological changes. Even though the effects of chronically increased N deposition on the forest plant communities are apparently obscured by the effects of canopy changes, the accumulated N might still have a significant impact. However, more research is needed to assess whether this N time bomb will indeed explode when canopies will open up again.
Integrated analysis of the effects of agricultural management on nitrogen fluxes at landscape scale
Kros, J. ; Frumeau, K.F.A. ; Hensen, A. ; Vries, W. de - \ 2011
Environmental Pollution 159 (2011)11. - ISSN 0269-7491 - p. 3171 - 3182.
agrarische bedrijfsvoering - ammoniakemissie - nitraatuitspoeling - distikstofmonoxide - stikstofverliezen - landgebruik - platteland - bemesting - natura 2000 - nederland - friesland - farm management - ammonia emission - nitrate leaching - nitrous oxide - nitrogen losses - land use - rural areas - fertilizer application - netherlands - atmospheric deposition - emissions - ammonia - farm
The integrated modelling system INITIATOR was applied to a landscape in the northern part of the Netherlands to assess current nitrogen fluxes to air and water and the impact of various agricultural measures on these fluxes, using spatially explicit input data on animal numbers, land use, agricultural management, meteorology and soil. Average model results on NH3 deposition and N concentrations in surface water appear to be comparable to observations, but the deviation can be large at local scale, despite the use of high resolution data. Evaluated measures include: air scrubbers reducing NH3 emissions from poultry and pig housing systems, low protein feeding, reduced fertilizer amounts and low-emission stables for cattle. Low protein feeding and restrictive fertilizer application had the largest effect on both N inputs and N losses, resulting in N deposition reductions on Natura 2000 sites of 10% and 12%, respectively.
Global assessment of nitrogen deposition effects on terrestrial plant diversity: a synthesis
Bobbink, R. ; Hicks, K. ; Galloway, J. ; Spranger, T. ; Alkemade, R. ; Ashmore, M.R. ; Bustamante, M. ; Cinderby, S. ; Davidson, E. ; Dentener, F. ; Emmett, B. ; Erisman, J.W. ; Fenn, M. ; Gilliam, F. ; Nordin, A. ; Pardo, L. ; Vries, W. de - \ 2010
Ecological Applications 20 (2010)1. - ISSN 1051-0761 - p. 30 - 59.
simulated environmental-change - arctic polar semidesert - western united-states - long-term - n-deposition - nutrient limitation - critical loads - racomitrium-lanuginosum - atmospheric deposition - southern california
Atmospheric nitrogen (N) deposition is a recognized threat to plant diversity in temperate and northern parts of Europe and North America. This paper assesses evidence from field experiments for N deposition effects and thresholds for terrestrial plant diversity protection across a latitudinal range of main categories of ecosystems, from arctic and boreal systems to tropical forests. Current thinking on the mechanisms of N deposition effects on plant diversity, the global distribution of G200 ecoregions, and current and future (2030) estimates of atmospheric N-deposition rates are then used to identify the risks to plant diversity in all major ecosystem types now and in the future. This synthesis paper clearly shows that N accumulation is the main driver of changes to species composition across the whole range of different ecosystem types by driving the competitive interactions that lead to composition change and/or making conditions unfavorable for some species. Other effects such as direct toxicity of nitrogen gases and aerosols, long-term negative effects of increased ammonium and ammonia availability, soil-mediated effects of acidification, and secondary stress and disturbance are more ecosystem- and site-specific and often play a supporting role. N deposition effects in mediterranean ecosystems have now been identified, leading to a first estimate of an effect threshold. Importantly, ecosystems thought of as not N limited, such as tropical and subtropical systems, may be more vulnerable in the regeneration phase, in situations where heterogeneity in N availability is reduced by atmospheric N deposition, on sandy soils, or in montane areas. Critical loads are effect thresholds for N deposition, and the critical load concept has helped European governments make progress toward reducing N loads on sensitive ecosystems. More needs to be done in Europe and North America, especially for the more sensitive ecosystem types, including several ecosystems of high conservation importance. The results of this assessment show that the vulnerable regions outside Europe and North America which have not received enough attention are ecoregions in eastern and southern Asia (China, India), an important part of the mediterranean ecoregion (California, southern Europe), and in the coming decades several subtropical and tropical parts of Latin America and Africa. Reductions in plant diversity by increased atmospheric N deposition may be more widespread than first thought, and more targeted studies are required in low background areas, especially in the G200 ecoregions.
Uncertainties in critical loads and target loads of sulphur and nitrogen for European forests: Analysis and quantification
Reinds, G.J. ; Vries, W. de - \ 2010
Science of the Total Environment 408 (2010)8. - ISSN 0048-9697 - p. 1960 - 1970.
soil acidification model - quantifying uncertainty - terrestrial ecosystems - atmospheric deposition - bayesian calibration - acid deposition - aluminum - sensitivity - solubility - horizons
An analysis of the uncertainties in critical loads and target loads of sulphur (S) and nitrogen (N) for 182 European forest soils was carried out using the Very Simple Dynamic (VSD) model. The VSD model was calibrated with a Bayesian approach using prior probability functions for model parameters based on literature data, data from 200 Dutch forest sites and from simulated denitrification rates from a detailed ecosystem model. The calibration strongly improved the fit of the model to observed soil and soil solution concentrations, especially for pH and base saturation. Calibration also narrowed down the ranges in input parameters. The uncertainty analysis showed which parameters contribute most to the uncertainty in the critical loads and target loads. Base cation weathering and deposition and the parameters describing the H–Al equilibrium in the soil solution determine the uncertainty in the maximum critical loads for S, CLmax(S), when based on the aluminium to base cation (Al/Bc) criterion. Uncertainty in CLmax(S) based on an acid neutralizing capacity (ANC) criterion is completely determined by base cation inputs alone. The denitrification fraction is the most important source of uncertainty for the maximum critical loads of N, CLmax(N). N uptake and N immobilisation determine the uncertainties in the critical load for N as a nutrient, CLnut(N). Calibration of VSD reduced the uncertainty: the coefficient of variation (CV) was reduced for all critical loads and criteria. After calibration, the CV for CLmax(S) was below 0.4 for almost all plots; however for CLmax(N) high values occurred for plots with high denitrification rates. Model calibration also improved the robustness of target load estimates: after calibration, no target loads were needed in any of the simulations for 40% of the plots, with the uncalibrated model there was a positive probability for the need of a target load for almost all plots
Assessment of the optimal time interval for repeated soil surveys at intensively monitored forest plots
Vries, W. de; Reinds, G.J. ; Bierkens, M.F.P. - \ 2009
Journal of Environmental Monitoring 11 (2009). - ISSN 1464-0325 - p. 2009 - 2021.
carbon sequestration - european forests - organic-carbon - atmospheric deposition - projected changes - landscape units - bulk-density - ecosystems - nitrogen - stocks
Statistical methods were developed to assess required changes in the contents and pools of major nutrients and exchangeable base cations in the organic layer and the mineral soil of European forest soils, to derive significant differences. Furthermore a simple element retention model is described and applied to assess the variation time periods, as a function of site and soil characteristics and atmospheric inputs, that are needed before repeating soil surveys in order to assess significant differences in element pools. Time periods that are needed to assess a significant difference have been limited to N in the organic layer and base cations in the mineral layer, since those pools are liable to change caused by nitrogen or acid deposition. Results showed that a time interval of 10 years, which is generally considered for a repetition of the soil survey, might give a significant difference in N and exchangeable base cation pools for approximately 25% and 10% of the plots, only.
Bayesian calibration of the VSD soil acidification model using European forest monitoring data
Reinds, G.J. ; Oijen, M. van; Heuvelink, G.B.M. ; Kros, J. - \ 2008
Geoderma 146 (2008)3-4. - ISSN 0016-7061 - p. 475 - 488.
acid deposition - critical loads - atmospheric deposition - chemistry - ecosystems - reduction - water
Over the past years, Bayesian calibration methods have been successfully applied to calibrate ecosystem models. Bayesian methods combine prior probability distributions of model parameters, based on assumptions about their magnitude and uncertainty, with estimates of the likelihood of the simulation results by comparison with observed values. Bayesian methods also quantify the uncertainty in the updated posterior parameters, which can be used to perform an analysis of model output uncertainty. In this paper, we applied Bayesian techniques to calibrate the VSD soil acidification model using data from 182 intensively monitored forest sites in Europe. Out of these 182 plots, 122 plots were used to calibrate VSD and the remaining 60 plots to validate the calibrated model. Prior distributions for the model parameters were based on available literature. Since the available literature shows a strong dependence of some VSD parameters on, for example, soil texture, prior distributions were allowed to depend on soil group (i.e. soils with similar texture or C/N ratio). The likelihood was computed by comparing modelled soil solution concentrations with observed concentrations for the period 1996¿2001. Markov Chain Monte Carlo (MCMC) was used to sample the posterior parameter space. Two calibration approaches were applied. In the single-site calibration, the plots were calibrated separately to obtain plot-specific posterior distributions. In the multi-site approach priors were assumed constant in space for each soil group, and all plots were calibrated simultaneously yielding one posterior probability distribution for each soil group. Results from the single-site calibrations show that the model performed much better after calibration compared to a run with standard input parameters when validated on the 60 validation plots. Posterior distributions for H-Al equilibrium constants narrowed down, thus decreasing parameter uncertainty. For base cation weathering of coarse textured soils the posterior distribution shifted to larger values, indicating an initial underestimation of the weathering rate for these soils. Results for the parameters related to nitrogen modelling showed that the nitrogen processes model formulations in VSD may have to be reconsidered as the relationship between nitrogen immobilization and the C/N ratio of the soil, as assumed in VSD, was not substantiated by the validation. The multi-site calibration also strongly decreased model error for most model output parameters, but model error was somewhat larger than the median model error from the single-site calibration except for nitrate. Because the large number of plots calibrated at the same time provided very many observations, the Markov Chain converged to a very narrow parameter space, leaving little room for posterior parameter uncertainty. For an uncertainty analysis with VSD on the European scale, this study provides promising results, but more work is needed to investigate how the results can be used on a European scale by looking at regional patterns in calibrated parameters from the site calibration or by calibrating for regions instead of all of Europe.
Scale-dependent homogenization: changes in breeding bird diversity in the Netherlands over a 25-year period
Turnhout, C.A.M. van; Foppen, R.P.B. ; Leuven, R.S.E.W. ; Siepel, H. ; Esselink, H. - \ 2007
Biological Conservation 134 (2007)4. - ISSN 0006-3207 - p. 505 - 516.
biotic homogenization - atmospheric deposition - north-america - urbanization - population - biodiversity - abundance - declines - britain - trends
Changes in breeding bird diversity in the Netherlands between 1973-1977 and 1998-2000 were evaluated by testing three hypotheses related to the loss of biodiversity: (1) species diversity is declining, (2) biotic homogenization is increasing and (3) rare species are declining more severely than abundant species. Using data collected for two successive national breeding bird atlases, changes in diversity were assessed at different spatial scales (local, regional and national) and among species characteristic for different landscapes (farmland, woodland, heathland, wetland, coastal habitats and urban habitats). National species richness, diversity and equitability had increased between the two atlas periods, with more species increasing than decreasing in range and abundance. Most species in the large groups of woodland and wetland birds showed positive trends, whereas most in the smaller groups of heathland, reed-breeding and meadow birds showed negative trends. However, findings varied between regions and localities. Increases in species richness occurred mainly in regions in the low-lying, western part of the country which were previously relatively poor in species. By contrast, species richness decreased in some previously species-rich regions in the eastern part of the country. This has resulted in a homogenization of breeding bird communities between regions. We advocate the conservation and restoration of regional identity as a priority for landscape planning in the Netherlands. We did not find a clear relation between species abundance and trends, although both rare and very abundant species tended to decrease on average.
Deposition monitoring networks : what monitoring is required to give reasonable estimates of ammonia/ammonium?
Erisman, J.W. ; Hensen, A. ; Mosquera Losada, J. ; Sutton, M. ; Fowler, D. - \ 2005
Environmental Pollution 135 (2005)3. - ISSN 0269-7491 - p. 419 - 431.
surface-exchange - throughfall measurements - atmospheric deposition - eu/icp forest - ammonia - vegetation - model - framework - emission - program
Deposition is one of the main loss terms for ammonia and ammonium from the atmosphere. It is also the input for ecosystems that can lead to drastic changes and effects. Deposition networks are needed to evaluate the need and the effect of policies to reduce nitrogen emissions, but also for studying deposition parameters and for developing deposition models. As with ambient concentrations of ammonia, deposition, especially dry deposition, varies strongly in space and in time. Furthermore, the bidirectional surface-atmosphere exchange of ammonia makes the combination of ambient concentration measurements with inferential models inadequate. Developing deposition monitoring networks with reasonable accuracy and representativeness is therefore not straightforward. In Europe several projects have addressed deposition monitoring. From these results it is concluded that a monitoring strategy should consist of a network with a limited amount of super sites combined with a larger number of sites where low cost methods are applied, together with models for generalisation. (c) 2004 Elsevier Ltd. All rights reserved.
Nitrogen content and d15N signature of ombrotrophic Sphagnum plants in Europe: to what extent is the increasing atmospheric N deposition altering the N-status of nutrient-poor mires?
Bragazza, L. ; Limpens, J. ; Gerdol, R. ; Grosvernier, P. ; Hajèk, M. ; Hajkova, P. ; Lacumin, P. ; Kutnar, L. ; Rydin, H. ; Tahvanainen, T. - \ 2005
Global Change Biology 11 (2005)1. - ISSN 1354-1013 - p. 106 - 114.
n-15 natural-abundance - atmospheric deposition - isotope composition - n-15/n-14 ratios - vascular plants - wet deposition - bog vegetation - carbon-dioxide - nitrate - growth
Alteration of the global nitrogen (N) cycle because of human-enhanced N fixation is a major concern particularly for those ecosystems that are nutrient poor by nature. Because Sphagnum-dominated mires are exclusively fed by wet and dry atmospheric deposition, they are assumed to be very sensitive to increased atmospheric N input. We assessed the consequences of increased atmospheric N deposition on total N concentration, N retention ability, and 15N isotopic signature of Sphagnum plants collected in 16 ombrotrophic mires across 11 European countries. The mires spanned a gradient of atmospheric N deposition from about 0.1 up to about 2 g m2 yr1. Mean N concentration in Sphagnum capitula was about 6 mg g1 in less polluted mires and about 13 mg g1 in highly N-polluted mires. The relative difference in N concentration between capitulum and stem decreased with increasing atmospheric N deposition, suggesting a possible metabolic mechanism that reduces excessive N accumulation in the capitulum. Sphagnum plants showed lower rates of N absorption under increasing atmospheric N deposition, indicating N saturation in Sphagnum tissues. The latter probably is related to a shift from N-limited conditions to limitation by other nutrients. The capacity of the Sphagnum layer to filter atmospheric N deposition decreased exponentially along the depositional gradient resulting in enrichment of the mire pore water with inorganic N forms (i.e., NO3+NH4+). Sphagnum plants had 15N signatures ranging from about 8 to about 3. The isotopic signatures were rather related to the ratio of reduced to oxidized N forms in atmospheric deposition than to total amount of atmospheric N deposition, indicating that 15N signature of Sphagnum plants can be used as an integrated measure of 15N signature of atmospheric precipitation. Indeed, mires located in areas characterized by greater emissions of NH3 (i.e., mainly affected by agricultural activities) had Sphagnum plants with a lower 15N signature compared with mires located in areas dominated by NOx emissions (i.e., mainly affected by industrial activities).
Decline of lichen-diversity in calcium-poor coastal dune vegetation since the 1970s, related to grass and moss encroachment
Ketner-Oostra, H.G.M. ; Sykora, K.V. - \ 2004
Phytocoenologia 34 (2004)4. - ISSN 0340-269X - p. 521 - 549.
atmospheric deposition - ammophila-arenaria - soil - netherlands
Since the 1970s the encroachment by tall graminoids, especially of Ammophila arenaria, has changed the aspect of the calcium-poor 'grey dunes' of the Wadden Sea island Terschelling (The Netherlands) formerly dominated by Corynephorus canescens. In addition, the neophytic moss Campylopus introflexus, a species adapted to acid open sand invaded these dunes. In this paper the cryptogam vegetation inside dry dune-grassland (the Corynephorion, the Tortulo- and Polygalo-Koelerion) and dune-heath (Empetrion) before (the 1960s) and after these changes (the 1990s) are compared. It was found that in the former period the lichen diversity in several plant communities was very high, amounting to a total of 45 species, among which 10 epigeic growing species that are usually epiphytes. In the latter period, Campylopus introflexus not only outgrew the rare lichens from the pioneer stage of the Violo-Corynephoretum, but also the more common pioneer species of decalcified sand. However, when this moss has lower vitality through desiccation or being blown-over by sand, common humicolous lichens and some pioneer species may act as secondary pioneers on these withered moss carpets. In the 1990s some relatively open communities were still present in a transition stage of the Violo-Corynephoretum to the Phleo-Tortuletum and in the Phleo-Tortuletum itself, forming a suitable environment for some lichen pioneer species of subneutral sand, including some of the epigeic growing epiphytes.
Feldspar weathering as the key to understanding soil acidification monitoring data; a study of acid sandy soils in the Netherlands
Mol, G. ; Vriend, S.P. ; Gaans, P.F.M. van - \ 2003
Chemical Geology 202 (2003)39541. - ISSN 0009-2541 - p. 417 - 441.
atmospheric deposition - woodland soils - forest soil - compositional variation - geochemical record - aluminum - water - ecosystem - rates - neutralization
Monitoring activities pose special demands on the type of survey results needed. In the early 1990s a soil acidification monitoring methodology was adopted in the Netherlands that leaned heavily on methods developed in more fundamental research, most notably the use of proton budgets. Consequently, various controversies still not resolved in the scientific debate reflect on the current practice of soil acidity monitoring and complicate interpretation of the monitoring results. In a pilot study we address the most pressing issues: capacity versus intensity parameters, choice of monitoring objective, and natural variation in the compartment to be monitored. Focus is on the major source of buffering, the possible usefulness of the historic approach, and the regional patterns present in the sandy soils of the Netherlands. In a field campaign 92 locations in sandy regions all over the country were sampled at two depths. The solid phase, the displaced soil solution, and solid phase extractions with 0.01 M CaCl2 and 0.43 M HNO3, for the 184 samples were analyzed by a variety of methods. Aluminum release is the major source of buffering and is shown to contribute substantially to acid buffering already under natural conditions. The predominant Al bearing phases in Dutch sandy soils are feldspars and secondary Al minerals; feldspars are found to be the determinative phase in acid buffering. Application of the historic approach using the subsoil as a proxy for the initial composition of the topsoil proved feasible for this regional dataset. The average depletion of the ANC(s) of 230 mmolc kg¿1 in the topsoil matches well with estimates of the total proton load since the last ice age, with the anthropogenic contribution being between 20% and 50%. Fuzzy c-means cluster analyses of the solid phase and soil solution data show a distinct regionality that was also reflected in the parameters generally used to indicate the acidity status of soils, ¿ANC(s) and Al/BC ratios. A combined insight into both solid phase and soil solution, based on a comprehensive set of parameters, proves essential for interpreting soil acidity monitoring data.