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1.
Simulations with the process oriented Forest-DNDC model showed reasonable to good agreement with observations of soil water contents of different soil layers, annual amounts of seepage water and approximated rates of nitrate leaching at 79 sites across Germany. Following site evaluation, Forest-DNDC was coupled to a GIS to assess nitrate leaching from German forest ecosystems for the year 2000. At national scale leaching rates varied in a range of 0–>80 kg NO 3–N ha −1 yr −1 (mean 5.5 kg NO 3–N ha −1 yr −1). A comparison of regional simulations with the results of a nitrate inventory study for Bavaria showed that measured and simulated percentages for different nitrate leaching classes (0–5 kg N ha −1 yr −1:66% vs. 74%, 5–15 kg N ha −1 yr −1:20% vs. 20%, >15 kg N ha −1 yr −1:14% vs. 6%) were in good agreement. Mean nitrate concentrations in seepage water ranged between 0 and 23 mg NO 3–N l −1. 相似文献
2.
Short-term increases in soil solution nitrate (NO 3−) concentration are often observed after forest harvest, even in N-limited systems. We model NO 3− leaching below the rooting zone as a function of site productivity. Using national forest inventories and published estimates of N attenuation in rivers and the riparian zone, we estimate effects of stem-only harvesting on NO 3− leaching to groundwater, surface waters and the marine environment. Stem-only harvesting is a minor contributor to NO 3− pollution of Swedish waters. Effects in surface waters are rapidly diluted downstream, but can be locally important for shallow well-waters as well as for the total amount of N reaching the sea. Harvesting adds approximately 8 Gg NO 3-N to soil waters in Sweden, with local concentrations up to 7 mg NO 3-N l −1. Of that, ∼3.3 Gg reaches the marine environment. This is ∼3% of the overall Swedish N load to the Baltic. 相似文献
3.
The role of nitrogen (N) in acidification of soil and water has become relatively more important as the deposition of sulphur has decreased. Starting in 1991, we have conducted a whole-catchment experiment with N addition at Gårdsjön, Sweden, to investigate the risk of N saturation. We have added 41 kg N ha −1 yr −1 as NH 4NO 3 to the ambient 9 kg N ha −1 yr −1 in fortnightly doses by means of sprinkling system. The fraction of input N lost to runoff has increased from 0% to 10%. Increased concentrations of NO 3 in runoff partially offset the decreasing concentrations of SO 4 and slowed ecosystem recovery from acid deposition. From 1990-2002, about 5% of the total N input went to runoff, 44% to biomass, and the remaining 51% to soil. The soil N pool increased by 5%. N deposition enhanced carbon (C) sequestration at a mean C/N ratio of 42-59 g g −1. 相似文献
4.
Nitrogen concentration and δ15N in 175 epilithic moss samples were investigated along four directions from urban to rural sites in Guiyang, SW China. The spatial variations of moss N concentration and δ15N revealed that atmospheric N deposition is dominated by NH x-N from two major sources (urban sewage NH 3 and agricultural NH 3), the deposition of urban-derived NH x followed a point source pattern characterized by an exponential decline with distance from the urban center, while the agricultural-derived NH x was shown to be a non-point source. The relationship between moss N concentration and distance ( y = 1.5e −0.13x + 1.26) indicated that the maximum transporting distance of urban-derived NH x averaged 41 km from the urban center, and it could be determined from the relationship between moss δ15N and distance [ y = 2.54 ln( x) − 12.227] that urban-derived NH x was proportionally lower than agricultural-derived NH x in N deposition at sites beyond 17.2 km from the urban center. Consequently, the variation of urban-derived NH x with distance from the urban center could be modeled as y = 56.272e −0.116x − 0.481 in the Guiyang area. 相似文献
5.
This study examined the influence of distance to the forest edge, forest type, and time on Cl −, SO 42−, NO 3−, and NH 4+ throughfall deposition in forest edges. The forests were dominated by pedunculate oak, silver birch, or Corsican/Austrian pine, and were situated in two regions of Flanders (Belgium). Along transects, throughfall deposition was monitored at distances of 0-128 m from the forest edge. A repeated-measures analysis demonstrated that time, forest type, and distance to the forest edge significantly influenced throughfall deposition of the ions studied. The effect of distance to the forest edge depended significantly on forest type in the deposition of Cl −, SO 42−, and NO 3−: the edge effect was significantly greater in pine stands than in deciduous birch and oak stands. This finding supports the possibility of converting pine plantations into oak or birch forests in order to mitigate the input of nitrogen and potentially acidifying deposition. 相似文献
6.
Critical loads (CLs) define maximum atmospheric deposition levels apparently preventative of ecosystem harm. We present first nitrogen CLs for northwestern North America’s maritime forests. Using multiple linear regression, we related epiphytic-macrolichen community composition to: 1) wet deposition from the National Atmospheric Deposition Program, 2) wet, dry, and total N deposition from the Communities Multi-Scale Air Quality model, and 3) ambient particulate N from Interagency Monitoring of Protected Visual Environments (IMPROVE). Sensitive species declines of 20-40% were associated with CLs of 1-4 and 3-9 kg N ha −1 y −1 in wet and total deposition. CLs increased with precipitation across the landscape, presumably from dilution or leaching of depositional N. Tight linear correlation between lichen and IMPROVE data suggests a simple screening tool for CL exceedance in US Class I areas. The total N model replicated several US and European lichen CLs and may therefore be helpful in estimating other temperate-forest lichen CLs. 相似文献
7.
Effects of elevated N deposition on forest aboveground biomass were evaluated using long-term data from N addition experiments and from forest observation plots in Switzerland. N addition experiments with saplings were established both on calcareous and on acidic soils, in 3 plots with Fagus sylvatica and in 4 plots with Picea abies. The treatments were conducted during 15 years and consisted of additions of dry NH 4NO 3 at rates of 0, 10, 20, 40, 80, and 160 kg N ha −1 yr −1. The same tree species were observed in permanent forest observation plots covering the time span between 1984 and 2007, at modeled N deposition rates of 12-46 kg N ha −1 yr −1. Experimental N addition resulted in either no change or in a decreased shoot growth and in a reduced phosphorus concentration in the foliage in all experimental plots. In the forest, a decrease of foliar P concentration was observed between 1984 and 2007, resulting in insufficient concentrations in 71% and 67% of the Fagus and Picea plots, respectively, and in an increasing N:P ratio in Fagus. Stem increment decreased during the observation period even if corrected for age. Forest observations suggest an increasing P limitation in Swiss forests especially in Fagus which is accompanied by a growth decrease whereas the N addition experiments support the hypothesis that elevated N deposition is an important cause for this development. 相似文献
8.
Surface water concentrations of dissolved organic carbon ([DOC]) are changing throughout the northern hemisphere due to changes
in climate, land use and acid deposition. However, the relative importance of these drivers is unclear. Here, we use the Integrated
Catchments model for Carbon (INCA-C) to simulate long-term (1996–2008) streamwater [DOC] at the four Swedish integrated monitoring
(IM) sites. These are unmanaged headwater catchments with old-growth forests and no major changes in land use. Daily, seasonal
and long-term variations in streamwater [DOC] driven by runoff, seasonal temperature and atmospheric sulfate (SO 4
2−) deposition were observed at all sites. Using INCA-C, it was possible to reproduce observed patterns of variability in streamwater
[DOC] at the four IM sites. Runoff was found to be the main short-term control on [DOC]. Seasonal patterns in [DOC] were controlled
primarily by soil temperature. Measured SO 4
2− deposition explained some of the long-term [DOC] variability at all sites. 相似文献
9.
The intensive investigation site ‘Mühleggerköpfl’ in the North Tyrolean Limestone Alps can be classified as a clean-air area site. The mean concentrations of NOx are far below the effect-related limit value of the WHO (30 μg NOx m−3). The gravitational depositions in the open field (bulk deposition) ranged from 10.8 to 14.7 kg N ha−1 a−1 (throughfall: 11.3 to 12.3 kg N ha−1 a−1) in the measuring years 1998 to 2000. Compared to these data, depositions in other forested areas of the Austrian Alps amounted to up to 30 kg N ha−1 a−1. The gravitational depositions (bulk deposition) alone - without considering dry and occult deposition - slightly exceeded the lower limit of Critical Loads for coniferous and deciduous forests (> 10 kg N ha−1 a−1), but were below the Critical Loads for calcareous forests (15–20 kg N ha−1 a−1). 相似文献
10.
Nitrogen isotopic composition of new, middle-aged and old camphor leaves in upper and lower canopies has been determined in a living area, near a motorway and near an industrial area (Jiangan Chemical Fertilizer Plant). We found that at sites near roads, more positive δ 15N values were observed in the camphor leaves, especially in old leaves of upper canopies, and ?δ 15N = δ 15N upper − δ 15N lower > 0, while those near the industrial area had more negative δ 15N values and ?δ 15N < 0. These could be explained by two isotopically different atmospheric N sources: greater uptake from isotopically heavy pools of atmospheric NO x by old leaves in upper canopies at sites adjacent to roads, and greater uptake of 15N-depleted NH y in atmospheric deposition by leaves at sites near the industrial area. This study presents novel evidence that 15N natural abundance of camphor leaves can be used as a robust indicator of atmospheric N sources. 相似文献
11.
We calculated farm, land, and soil N-budgets for countries in Europe and the EU27 as a whole using the agro-economic model CAPRI. For EU27, N-surplus is 55 kg N ha −1 yr −1 in a soil budget and 65 kg N 2O–N ha −1 yr −1 and 67 kg N ha −1 yr −1 in land and farm budgets, respectively. NUE is 31% for the farm budget, 60% for the land budget and 63% for the soil budget. NS values are mainly related to the excretion (farm budget) and application (soil and land budget) of manure per hectare of total agricultural land. On the other hand, NUE is best explained by the specialization of the agricultural system toward animal production (farm NUE) or the share of imported feedstuff (soil NUE). Total N input, intensive farming, and the specialization to animal production are found to be the main drivers for a high NS and low NUE. 相似文献
12.
Two-week average concentrations of ozone (O 3), nitric acid vapor (HNO 3) and ammonia (NH 3) were measured with passive samplers during the 2002 summer season across the central Sierra Nevada Mountains, California, along the San Joaquin River drainage. Elevated concentrations of the pollutants were determined with seasonal means for individual sites ranging between 62 and 88 ppb for O 3, 1.0-3.8 μg m −3 for HNO 3, and 2.6-5.2 μg m −3 for NH 3. Calculated O 3 exposure indices were very high, reaching SUM00-191 ppm h, SUM60-151 ppm h, and W126-124 ppm h. Calculated nitrogen (N) dry deposition ranged from 1.4 to 15 kg N ha −1 for maximum values, and 0.4-8 kg N ha −1 for minimum values; potentially exceeding Critical Loads (CL) for nutritional N. The U.S., California, and European 8 h O 3 human health standards were exceeded during 104, 108, and 114 days respectively, indicating high risk to humans from ambient O 3. 相似文献
13.
The potential of alpine moss-sedge heath to recover from elevated nitrogen (N) deposition was assessed by transplanting Racomitrium lanuginosum shoots and vegetation turfs between 10 elevated N deposition sites (8.2-32.9 kg ha −1 yr −1) and a low N deposition site, Ben Wyvis (7.2 kg ha −1 yr −1). After two years, tissue N of Racomitrium shoots transplanted from higher N sites to Ben Wyvis only partially equilibrated to reduced N deposition whereas reciprocal transplants almost matched the tissue N of indigenous moss. Unexpectedly, moss shoot growth was stimulated at higher N deposition sites. However, moss depth and biomass increased in turfs transplanted to Ben Wyvis, apparently due to slower shoot turnover (suggested to result partly from decreased tissue C:N slowing decomposition), whilst abundance of vascular species declined. Racomitrium heath has the potential to recover from the impacts of N deposition; however, this is constrained by the persistence of enhanced moss tissue N contents. 相似文献
14.
Responses of understory plant diversity to nitrogen (N) additions were investigated in reforested forests of contrasting disturbance regimes in southern China from 2003 to 2008: disturbed forest (with harvesting of understory vegetation and litter) and rehabilitated forest (without harvesting). Experimental additions of N were administered as the following treatments: Control, 50 kg N ha −1 yr −1, and 100 kg N ha −1 yr −1. Nitrogen additions did not significantly affect understory plant richness, density, and cover in the disturbed forest. Similarly, no significant response was found for canopy closure in this forest. In the rehabilitated forest, species richness and density showed no significant response to N additions; however, understory cover decreased significantly in the N-treated plots, largely a function of a significant increase in canopy closure. Our results suggest that responses of plant diversity to N deposition may vary with different land-use history, and rehabilitated forests may be more sensitive to N deposition. 相似文献
15.
A model assuming first-order losses by evasion and leaching was used to evaluate Hg dynamics in UK soils since 1850. Temporal deposition patterns of Hg were constructed from literature information. Inverse modelling indicated that 30% of 898 rural sites receive Hg only from the global circulation, while in 51% of cases local deposition exceeds global. Average estimated deposition is 16 μg Hg m −2 a −1 to rural soils, 19 μg Hg m −2 a −1 to rural and non-rural soils combined. UK soils currently hold 2490 tonnes of reactive Hg, of which 2140 tonnes are due to anthropogenic deposition, mostly local in origin. Topsoil currently releases 5.1 tonnes of Hg 0 per annum to the atmosphere, about 50% more than the anthropogenic flux. Sorptive retention of Hg in the lower soil exerts a strong control on surface water Hg concentrations. Following decreases in inputs, soil Hg concentrations are predicted to decline over hundreds of years. 相似文献
16.
Soil acidification has been of concern in the oil sands region in Alberta due to increased acid deposition. Using the canopy budget model, and accounting for H + canopy leaching by organic acids, we determined sources and sinks of H + in throughfall in jack pine ( Pinus banksiana) and trembling aspen ( Populus tremuloides) stands in two watersheds from 2006 to 2009. In pine stands, H + deposition was greater in throughfall than in bulk precipitation while the opposite was true in aspen stands. The annual H + interception deposition was 148.8-193.8 and 49.7-70.0 mol c ha −1 in pine and aspen stands, respectively; while the annual H + canopy leaching was 127.1-128.7 and 0.0-6.0 mol c ha −1, respectively. The greater H + supply in pine stands was caused by greater interception deposition of SO 42− and organic acids released from the pine canopy. Such findings have significant implications for establishing critical loads for various ecosystems in the oil sands region. 相似文献
17.
Changes in sulphur and nitrogen pollution in Swedish forests have been assessed in relation to European emission reductions, based on measurements in the Swedish Throughfall Monitoring Network. Measurements were analysed over 20 years with a focus on the 12-year period 1996 to 2008. Air concentrations of SO 2 and NO 2, have decreased. The SO 4-deposition has decreased in parallel with the European emission reductions. Soil water SO 4-concentrations have decreased at most sites but the pH, ANC and inorganic Al-concentrations indicated acidification recovery only at some of the sites. No changes in the bulk deposition of inorganic nitrogen could be demonstrated. Elevated NO 3-concentrations in the soil water occurred at irregular occasions at some southern sites. Despite considerable air pollution emission reductions in Europe, acidification recovery in Swedish forests soils is slow. Nitrogen deposition to Swedish forests continues at elevated levels that may lead to leaching of nitrate to surface waters. 相似文献
18.
We assessed nitrous oxide (N 2O) emissions at shoulder and foot-slope positions along three sloping sites (1.6–2.1%) to identify the factors controlling the spatial variations in emissions. The three sites received same amounts of total nitrogen (N) input at 170 kg N ha −1. Results showed that landscape positions had a significant, but not consistent effect on N 2O fluxes with larger emission in the foot-slope at only one of the three sites. The effect of soil inorganic N (NH 4+ + NO 3−) contents on N 2O fluxes (r 2 = 0.55, p < 0.001) was influenced by water-filled pore space (WFPS). Soil N 2O fluxes were related to inorganic N at WFPS > 60% (r 2 = 0.81, p < 0.001), and NH 4+ contents at WFPS < 60% (r 2 = 0.40, p < 0.01), respectively. Differences in WFPS between shoulder and foot-slope correlated linearly with differences in N 2O fluxes (r 2 = 0.45, p < 0.001). We conclude that spatial variations in N 2O emission were regulated by the influence of hydrological processes on soil aeration intensity. 相似文献
19.
Ambient air and dry deposition, and soil samples were collected at the Aliaga industrial site in Izmir, Turkey. Atmospheric total (particle + gas) ∑ 41-PCB concentrations were higher in summer (3370 ± 1617 pg m −3, average + SD) than in winter (1164 ± 618 pg m −3), probably due to increased volatilization with temperature. Average particulate ∑ 41-PCBs dry deposition fluxes were 349 ± 183 and 469 ± 328 ng m −2 day −1 in summer and winter, respectively. Overall average particulate deposition velocity was 5.5 ± 3.5 cm s −1. The spatial distribution of ∑ 41-PCB soil concentrations ( n = 48) showed that the iron-steel plants, ship dismantling facilities, refinery and petrochemicals complex are the major sources in the area. Calculated air-soil exchange fluxes indicated that the contaminated soil is a secondary source to the atmosphere for lighter PCBs and as a sink for heavier ones. Comparable magnitude of gas exchange and dry particle deposition fluxes indicated that both mechanisms are equally important for PCB movement between air and soil in Aliaga. 相似文献
20.
Deep percolation of nitrate can contribute to the deterioration of groundwater resources. Leaching of nitrate is a complex process affected by fertilizer and irrigation practices, efficiency of N use by the crop, and how the soil's water holding capacity and water transmission properties are affected by soil texture. Depleted ( 15NH 4) 2SO 4 fertilizer at N rates of 0, 125, 250 and 375 kg ha −1 was applied annually for 3 years to continuous corn grown within three different water regimes. This time period and the labeled N permitted an evaluation of N use efficiency by the crop and NO 3 leaching and carryover on a Weld silty clay loam, a fine-textured soil, typical of the “hardland” soils of the semi-arid Great Plains. Three water regimes, W1 ( 1.5 ET), W2 ( ET) and W3 ( 0.8 ET), were used. Beneath each plot within each water regime, Duke-Haise vacuum trough extractors were installed under undisturbed soil profiles at 1.22-m depth to measure weekly percolate and the NO 3 concentration in the percolate. The corn was harvested in the fall in the dent stage to measure the total above-ground biomass N uptake. Soil profiles (1.8 m) were sampled annually in the fall after crop harvest to determine NO 3---N in the soil or carryover.Great variability was encountered in measuring the amount of extractor water and its NO 3 content under each water regime, which made estimates of N03 leaching losses unreliable. Also, the variability demonstrates formidable problems in quantifying percolation losses with vacuum trough extractors under undisturbed fine-textured soil profiles. With the highest N rate of 376 kg ha −1 yr −1 and within the water regime W 1, where leaching was expected to be greatest, only 1% of the cumulative labeled N applied was found in extractor waters and most movement of the labeled N into extractors occurred the third year. The 125-kg-ha −1 yr −1 fertilizer N rate significantly increased the crop yield over the unfertilized plots without increasing residual NO 3---N accumulation; whereas fertilizer N rates of > 125 kg ha −1 yr −1 did not appreciably increase plant yields over the 125-kg-ha −1-N rate, but did appreciably increase residual NO 3. 相似文献
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