Calculating nitrogen deposition in Europe

Nitrogen deposition calculations for Europe were performed by separate models describing the long-range transport of ammonia and oxidized N. A linearized version of a non-linear atmospheric chemistry model was used for calculating oxidized N. Model computations were found to be consistent with the observed spatial pattern of wet nitrate deposition in Europe. Interannual meteorological variability was estimated to cause a typical year-to-year variation in annual oxidized N deposition of about 6 to 10%. Nitrogen deposition was computed for several NO _x emissions reduction scenarios. These scenarios were derived from an OECD study and applied to the 27 largest countries in Europe. Most reduction scenarios affected the deposition pattern of oxidized N, but the most extreme NO _x emission reduction scenario did not change very much the overall pattern of total (oxidized N plus ammonia N) N deposition. Depending on the desired level of environmental protection, it may be necessary to reduce ammonia emissions in addition to NO _x emissions in order to reduce N deposition in Europe.     

Contribution of dissolved organic nitrogen deposition to total dissolved nitrogen deposition under intensive agricultural activities

For elucidating the atmospheric deposition contribution of dissolved organic nitrogen (DON) to the total dissolved nitrogen (TDN) deposition rate, dissolved inorganic nitrogen (DIN: NH₄ ⁺ + NO₃ ^–) and DON deposition rates were annually and monthly estimated during 4 and half-yr monitoring period in an experimental multi-farm under intensive agricultural activities of N fertilizer use and animal husbandry in Central Japan. Annual NH₄ ⁺, DON and NO₃ ^– deposition rates in bulk and wet deposition data accounted for 48%, 32% and 20% of TDN deposition, respectively, which indicated that this area is strongly affected by the intensive agricultural activities. The DIN and DON deposition rates were respectively estimated at 21.6 and 10.1 kg N ha^?1 yr^?1, which ranked high in a worldwide regional data set. Consequently, this area has been exposed to a large amount of N deposition including DON with N fertilizer input. The difference between bulk and wet deposition rates (NH₄ ⁺ and DON) is one of important factors controlling the N deposition in this area. Monthly DON deposition showed positive correlations with DIN and NH₄ ⁺ deposition rates, respectively, with a significant linear regression curve. The linear regression curve of our monthly data (n = 127) indicates the same trend as the worldwide annual data set (n = 31).     

Nonlinear response of soil ammonia emissions to fertilizer nitrogen

Ammonia (NH₃) is an important atmospheric pollutant that threatens ecosystem and human health. Synthetic nitrogen (N) fertilizer applications are a major source of atmospheric NH₃. Most of current bottom-up estimates assume that the NH₃ emission response to increasing N application rates is linear, and thus constant emission factors (EFs) are used. However, increasing evidence suggests that NH₃ emissions increase exponentially with increasing N inputs. In the present study, we conducted a meta-analysis to generalize the relationship between N inputs and NH₃ emissions. Overall, the change in EF per unit of additional N fertilizer input (ΔEF) was positive from 70 experiments with at least three N application rates, suggesting that NH₃ emissions in response to increasing N additions grow at a rate higher than linear. Compared to our ΔEF model, the 10% EF model used by Intergovernmental Panel on Climate Change overestimated NH₃ emissions when fertilizer N is applied at low levels, but underestimated NH₃ emissions when N is applied in excess. Therefore, our results suggest that replacing the constant EF with the N-rate-dependent EF could improve the accuracy of NH₃ emission estimates.     

Approaches to measuring the contribution of nematodes and protozoa to nitrogen mineralization in the rhizosphere

Abstract. Nematodes and protozoa assist nitrogen mineralization by consuming bacteria, and this may increase the amount of nitrogen taken up by plants so that it exceeds the amount lost by root exudation. One of the methods used to determine bacterial consumption by protozoan grazers in aquatic ecosystems, namely progressive dilution of the grazing pressure, was tested in a sandy soil. The result suggests that a basic assumption of the technique, that grazing is directly proportional to the dilution factor, is untrue for soils, possibly because the increase in moisture content with increasing dilution enhances grazer activity.     

大气氮素沉降研究进展

人为干扰下的大气氮素沉降已成为全球氮素生物化学循环的一个重要组成部分。作为营养源和酸源, 大气氮沉降数量的急剧增加将严重影响陆地及水生生态系统的生产力和稳定性。本文从大气氮沉降对土壤和水体环境、农业和森林生态系统以及生物多样性等方面综述了近年来国内外大气氮素沉降的研究现状及其对生态系统的影响, 并总结探讨了前人采用的大气沉降氮测定方法, 展望了我国大气氮沉降的研究前景。     

Microbial community response to nitrogen deposition in northern forest ecosystems

The productivity of temperate forests is often limited by soil N availability, suggesting that elevated atmospheric N deposition could increase ecosystem C storage. However, the magnitude of this increase is dependent on rates of soil organic matter formation as well as rates of plant production. Nonetheless, we have a limited understanding of the potential for atmospheric N deposition to alter microbial activity in soil, and hence rates of soil organic matter formation. Because high levels of inorganic N suppress lignin oxidation by white rot basidiomycetes and generally enhance cellulose hydrolysis, we hypothesized that atmospheric N deposition would alter microbial decomposition in a manner that was consistent with changes in enzyme activity and shift decomposition from fungi to less efficient bacteria. To test our idea, we experimentally manipulated atmospheric N deposition (0, 30 and 80 kg NO₃⁻-N) in three northern temperate forests (black oak/white oak (BOWO), sugar maple/red oak (SMRO), and sugar maple/basswood (SMBW)). After one year, we measured the activity of ligninolytic and cellulolytic soil enzymes, and traced the fate of lignin and cellulose breakdown products (¹³C-vanillin, catechol and cellobiose).In the BOWO ecosystem, the highest level of N deposition tended to reduce phenol oxidase activity (131±13 versus 104±5 μmol h⁻¹ g⁻¹) and peroxidase activity (210±26 versus 190±21 μmol h⁻¹ g⁻¹) and it reduced ¹³C-vanillin and ¹³C-catechol degradation and the incorporation of ¹³C into fungal phospholipids (p<0.05). Conversely, in the SMRO and SMBW ecosystems, N deposition tended to increase phenol oxidase and peroxidase activities and increased vanillin and catechol degradation and the incorporation of isotope into fungal phospholipids (p<0.05). We observed no effect of experimental N deposition on the degradation of ¹³C-cellulose, although cellulase activity showed a small and marginally significant increase (p<0.10). The ecosystem-specific response of microbial activity and soil C cycling to experimental N addition indicates that accurate prediction of soil C storage requires a better understanding of the physiological response of microbial communities to atmospheric N deposition.     

Preliminary study on the distribution of ammonia oxidizers and their contribution to potential ammonia oxidation in the plant-bed/ditch system of a constructed wetland

Purpose

Ammonia oxidation—as the rate-limiting step of nitrification—has been found to be performed by both ammonia-oxidizing archaea (AOA) and bacteria (AOB). However, how ammonium content and oxidation–reduction status regulate the distribution of ammonia oxidizers in constructed wetlands and their contribution to potential ammonia oxidation rate are still in dispute. This study aimed to explore the effects of ammonium content and oxidation–reduction status on the abundances of AOA/AOB and examine the contributions of AOA and AOB populations to ammonia oxidation rates in the plant-bed/ditch system of a constructed wetland.

Materials and methods

Sampling was carried out in the plant-bed/ditch system of the Shijiuyang Constructed Wetland, China. Three plant-bed soil cores were collected using a soil auger and sampled at depths of 0, 20, and 50 cm in 5-cm increments. Five ditch surface sediments (0–5 cm) were collected along the water flow direction. The abundances of AOA and AOB were investigated by quantitative polymerase chain reaction based on amoA genes. The potential ammonia oxidation rate was determined using the chlorate inhibition method.

Results and discussion

The results showed that AOA outnumbered AOB in the plant-bed surface soil which had lower ammonium content (4.67–7.63 mg kg^?1), but that AOB outnumbered AOA in the ditch surface sediment which had higher ammonium content (14.0–22.9 mg kg^?1). Ammonium content was found to be the crucial factor influencing the relative abundances of AOA and AOB in the surface samples of the plant-bed/ditch system. In the deep layers of the plant bed, AOA abundance outnumbered AOB, though much lower oxidation–reduction potential occurred along the water flow direction. Thus, the oxidation–reduction potential may be another factor influencing the distributions of AOA and AOB in the deep layers of the plant bed without significant difference in ammonium content (p?<?0.05). Moreover, the potential ammonia oxidation rate was significantly dominated by AOB rather than AOA in the plant-bed/ditch system.

Conclusions

The high ammonium content in the ditch sediment likely favored AOB. AOA seemed to persist more readily even under low oxidation–reduction potential in the deep layers of the plant bed. Ammonium content and the oxidation–reduction potential were important parameters influencing the distribution of AOA and AOB in the plant-bed/ditch system of Shijiuyang Constructed Wetland. AOB contributed more to ammonia oxidation than AOA, both in the plant-bed soils (r?=?0.592, p?=?0.0096) and in the ditch sediments (r?=?0.873, p?=?0.0002).     

华南受干扰林和成熟林氮素流失对模拟氮沉降的响应

Current nitrogen (N) leaching losses and their responses to monthly N additions were investigated under a disturbed pine (Pinus massoniana) forest and a mature monsoon broadleaf forest in southern China. N leaching losses from both disturbed and mature forests were quite high (14.6 and 29.2 kg N ha^-1 year^-1, respectively), accounting for 57% and 80% of their corresponding atmospheric N inputs. N leaching losses were substantially increased following the first 1.5 years of N applications in both forests. The average increases induced by the addition of 50 and 100 kg N ha^-1 year^-1 were 36.5 and 24.9 kg N ha^-1 year^-1, respectively, in the mature forest, accounting for 73.0% and 24.9% of the annual amount of N added, and 14.2 and 16.8 kg N ha^-1 year^-1 in the disturbed forest, accounting for 28.4% and 16.8% of the added N. Great N leaching and a fast N leaching response to N additions in the mature forest might result from long-term N accumulation and high ambient N deposition load (greater than 30 kg N ha^-1 year^-1 over the past 15 years), whereas in the disturbed forest, it might result from the human disturbance and high ambient N deposition load. These results suggest that both disturbed and mature forests in the study region may be sensitive to increasing N deposition.     

Effects of habitat management on heathland response to atmospheric nitrogen deposition

A field experiment was carried out to investigate the impact of four different management treatments on the response of Calluna-dominated heathland to nitrogen additions of 0 or 30 kg ha⁻¹ yr⁻¹ at a lowland heath in Surrey, England. Post-management Calluna regeneration, growth and canopy development were significantly affected by both the form of management and by nitrogen addition. The effect of nitrogen on shoot growth was lower, in absolute terms, in those plots which had undergone more intensive management treatments. Seedling establishment was higher in plots which received a simulated accidental burn treatment, reflecting the greater proportion of bare ground and the high degree of physical disturbance associated with this treatment. Invasion by Deschampsia seedlings was increased by nitrogen addition, particularly in simulated accidental burn plots. In the long term, the need to maintain a low nutrient environment to favour Calluna dominance, particularly in the face of elevated nitrogen deposition, favours the use of managements which result in the export of a significant proportion of the organic nitrogen stores. However, further study is required to ensure that initial enhancement of seedling invasion by grass and other species, associated with these more intense managements, does not outweigh the long term benefits of associated nutrient removal.     

Effects of nitrogen deposition on animal-mediated nitrogen mobilization in coniferous litter

Summary In microcosm studies the organic layers of coniferous forest soils show high nitrate and low ammonium mobilization, in accord with the presence of high numbers of autotrophic nitrifiers. The fungivorous collembolan Tomocerus minor (Lubbock) increases ammonium mobilization, probably through its excretion products, and has an indirect effect on nitrate mobilization. An input of N seems to have a negative effect on the number of nitrifiers and on nitrate mobilization; a decrease in N mobilization in the presence of T. minor is probably due to stimulation of microbial growth, which has an immobilizing effect.     

Response of nitrogen transformation to glucose additions in soils at two subtropical forest types subjected to simulated nitrogen deposition

Journal of Soils and Sediments - Soil nitrogen (N) transformation is an important phenomenon in forest ecosystems and it is regulated by carbon (C) input. This study aimed to evaluate the impacts...     

Acidification and nutrient imbalance in forest soils subjected to nitrogen deposition

Emission of nitrogen oxides (NO_x) and ammonia (NH₃) from a fertilizer factory and the resulting input of nitrates (NO₃ ^?) and ammonium (NH₄ ⁺) into the soil were the main reasons of nitrogen (N) cycle disturbance in forest ecosystems near Novgorod, North-Western Russia (50°31′ North, 31°17′ East). Total N atmospheric input was about 100 kg/ha annually. NH₃ was a dominant pollutant, causing the increase of atmospheric precipitation pH within the polluted region compared to background territories (6.0–6.5 and 4.5–5.0, respectively). Soil acidification through NH₄ ⁺ nitrification was observed. N-NO₃ ^? concentrations in soil solution reached 20–30 mg/l, and proton (H) production was equal to 4.1 keq/ha per warm season (from April to October). Compared with soil status in 1983, pH decrease by 0.2 pH units was found in A horizon. The content of exchangeable calcium (Ca) and magnesium (Mg) decreased by the factor of 2–3 and 1.5–2 in A and B horizons, respectively. Triple increase of exchangeable aluminium (Al) content was detected in A horizon. Through recent decrease of pollutant emission, the polluted territory is now a suitable subject for recovery studies.     

Sensitivity of forest-floor mosses in boreal forests to nitrogen and sulphur deposition

The response of forest-floor mosses to deposition of nitrogen (N) and sulphur (S) was examined in field conditions in a 60-year-old Norway spruce (Picea abies Karst.) stand in southern Finland. The experimental plots received nitrogen (25 kg N ha^–1) and sulphur (30 kg S ha^–1) as ammonium sulphate once a year for 4 years.The dominant moss species on the site were Pleurozium schreberi (Mitt.) and Dicranum polysetum (Sw.). The biomass of the dominant moss species was decreased significantly by N and S deposition during the study period. Due to the addition of N and S, the biomass of Pleurozium schreberi was decreased by 60% and the biomass of Dicranum polysetum by 78%.     

Acidic deposition and its effects on the forests of Nordic Europe

Air pollution effects on the forest of Nordic Europe are analyzed with respect to the situation before and after 1980. No adverse effects were reported up to 1980. Inventories of forest vitality in terms of needle loss or crown density as well as tree growth have been made in parts of Norway and the whole of Sweden. For Norway spruce, needle loss was found to increase with tree age and climatic stress with increasing latitude and altitude. However, decreased crown density was also reported for SW Sweden. Needle loss is a non-specific signal not reacting to air pollution alone. Direct effects of gases such as SO₂ are not likely to occur, but high episodic levels of O₃ have been measured at a level possibly leading to chronic injuries. Increasing soil acidity is reported from forests in SW Sweden and also from an alpine locality in southern Norway. A differentiation of biological and deposition-dependent acidification has been attempted. A soil acidification of up to 1 pH unit has occurred in both humus and mineral soil layers. An increased release of A1 and heavy metals combined with an increased loss of basic cations is now occurring. Soil acidification probably also results in less available amounts of phosphorus and is suggested to interact with N as limiting forest growth.     

Recent changes in the deposition of heavy metals in northern Europe

Carpet-forming bryophytes (mosses) have been used extensively since the late 1960's in assessing regional and temporal variability of atmospheric heavy-metal deposition. A large-scale decrease in heavy-metal deposition occurred during the 1970's in Sweden, probably also in other parts of northern Europe. The decrease was closely related to known changes in atmospheric emissions.     

毛叶苕子替代化学氮肥对幼龄柑橘氮素营养的贡献

研究毛叶苕子(Vicia villosa Roth)替代化学氮肥对幼龄柑橘不同部位生物量、氮素吸收量的影响,定量其对幼龄柑橘氮素营养的贡献率,旨在为柑橘园绿肥利用及其替代化肥方案提供科学理论支撑。以盆栽柑橘幼苗为研究对象,采用15N 同位素标记的毛叶苕子进行化学氮肥替代,设置5 个绿肥替代比例处理:0%(100%CF)、25%(25%GM+75%CF)、50%(50%GM+50%CF)、75%(75%GM+25%CF)、100%(100%GM), 每个处理4 次重复。在温室中培养6 个月后测定柑橘总生物量,根、茎、叶各器官生物量,氮含量以及15N 丰度。结果表明,绿肥替代化学氮肥能显著提高柑橘各器官生物量和氮吸收量,且随着替代比例的升高,各器官生物量呈先显著上升后稳定的趋势;柑橘总生物量在绿肥替代化学氮肥75% 时最高,较对照提高了107.5%;柑橘总氮吸收量在绿肥替代化学氮肥100% 时最高,较对照提高了45.1%。绿肥对柑橘各器官氮素营养的贡献随着替代化学氮肥比例的提高而增加,在75%GM+25%CF 和100%GM 处理中,柑橘根、茎和叶的氮素来自绿肥的比率分别为36.56% ～ 50.00%、35.03% ～ 46.81% 和34.52% ～ 50.72%,而在25%GM+75%CF 和50%GM+50%CF 处理中,绿肥对柑橘根、茎和叶的氮素贡献率仅分别有8.96% ～ 20.77%、9.41% ～ 19.77% 和7.82% ～ 20.94%;同时,随着绿肥替代化学氮肥比例的增加,氮素向柑橘根的分配增加,而向茎与叶的分配减少。在柑橘园管理中,进行绿肥栽培、利用可有效地替代化学氮肥,减少化肥的投入,增加柑橘的氮素营养。     

Soil sensitivity due to acid and heavy metal deposition in East Central Europe

Simultaneous soil acidification and deposition of heavy metals is a major concern for forest and agricultural soils of the Black Triangle region of East Central Europe including southern former East Germany, northern Bohemia of the Czech Republic, and southern Poland. The objective of this project was to develop historical and future projections of acid and heavy metal deposition to soils (As, Cd, Pb, Zn) and to produce a preliminary map of soil sensitivity to cadmium pollution and uptake by crops. Ultimately, we wish to assess the relative hazard and recovery times of soils to metals deposition in the region. Emission and deposition data bases obtained from several models developed at IIASA were linked using the Geographical Information System ARC/INFO to produce soil maps of sensitivity to cadmium mobility based on metals deposition, soil type, soil texture, organic matter content, and acid deposition. RAINS 6.1 (Alcamo et al., 1990) was utilized to produce maps of acid deposition for EMEP grids (150 km x 150 km). The largest amount of acid load is deposited in southern East Germany. Sulfur deposition in that area was 10–12 gS/m²/yr in 1990, and S+N deposition exceeded 8000 eq/ha/yr. But the hot spot for metals deposition is further to the east, in the Silesia area of southern Poland. The TRACE2 trajectory model of Alcamo, Bartnicki, and Olendrzynski (1992) was used to estimate cumulative metals deposition since 1955 with scenarios to 2010. Pb has improved over Europe since 1970 when depositions in the Ruhr River Valley of West Germany exceeded 60 mg/m²/yr. But cadmium deposition in southern Poland (Katowice and Krakow) has now accumulated to 60–70 mg/m² by atmospheric deposition alone. During base case simulations from 1955–87, approximately 1.8 mg/kg Pb and 0.12 mg/kg Cd have been added to the mixed plow-layer of 30 cm. If these emissions continue indefinitely, the accumulation of metals will become problematic for agriculture and the food chain.     

Rate-specific responses of prokaryotic diversity and structure to nitrogen deposition in the Leymus chinensis steppe

Serious nitrogen (N) deposition in terrestrial ecosystems causes soil acidification and changes the structure and function of the microbial community. However, it is unclear how these changes are dependent on N deposition rates, other factors induced by N (e.g., pH), and their interactions. In this study, we investigated the responses of soil prokaryotic community structure and stability after a 13-year N addition in the semi-arid Leymus chinensis steppe in Inner Mongolia, China. Our results demonstrated that the prokaryotic community structure changed at the low N addition rate of 1.75 g N m⁻² yr⁻¹; however, dramatic changes in microbial abundance, respiratory quotient, and prokaryotic diversity occurred at N addition rates of more than 5.25 g N m⁻² yr⁻¹ when the soil pH dropped below 6.0. The two patterns indicated the difference in driving forces for different microbial properties. The N-driven and pH-driven processes are likely the most important mechanisms determining the responses of bacterial community to N. Some copiotrophic/oligotrophic bacteria, e.g., Proteobacteria and Acidobacteria, changed their relative abundances with the N addition continuously even at a low rate, indicating that they were more sensitive to N directly. Some bacterial groups significantly changed their relative abundance at a high N addition rate when pH dropped below 6.0, e.g., Verrucomicrobia and Armatimonadetes, indicating that they were more sensitive to pH below 6.0. N addition altered the prokaryotic community structure through enrichment of copiotrophic bacteria (species adjustment) at low N addition rates and through enrichment of nitrophilous taxa and significant loss of diversity at high N rates. The results also demonstrated that a high N addition diminished the stability of the prokaryotic community structure and activity through reduction in species diversity and bacterial interaction. Overall, this study supported the hypothesis that the responses of prokaryota to N were dependent on deposition rates, and N-driven and pH-driven processes were the important mechanisms to control the shift of the prokaryotic community.