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1.
Nitrogen deposition, leaching, and retention were monitored in a mature spruce (Picea abies Karsten) dominated mixed boreal forest in eastern Finland. Bulk precipitation, throughfall, stemflow, and percolation through the podzolic soil profile were monitored from 1993 to 1996. Mean annual bulk deposition of total N was 3.83 kg ha-1, of which 33% was NH4 +, 26% was NO3 - , and 41% was organic N. Throughfall+stemflow flux of total N was 2.93 kg ha-1 yr-1. Sixty-four % of NH4 + and 38% of NO3 - in bulk precipitation was retained by tre three canopy. Organic N was released (0.27 kg ha-1 yr-1) from the tree canopy. Nitrate-N was retained and organic N was leached as the water passed through the ground vegetation and soil O-horizon. Ammonium-N and organic N were retained mainly in the E-horizon. The output of total N from the E-horizon was only 5% of the total N deposition in the forest stand during the study period and it was mainly as organic N. The output of inorganic N forms from under B-horizon was seasonal and occurred mainly at spring snowmelt. 相似文献
2.
Curtis C.J. Allott T.E.H. Reynolds B. Harriman R. 《Water, air, and soil pollution》1998,105(1-2):205-215
The relative contribution of N deposition to the acidification of freshwaters in Great Britain has increased over the last few years as S deposition has fallen in line with reduced emissions. In certain high deposition areas of Great Britain, NO3 --based acidity can equal or exceed the contribution of SO4 2--based acidity in some upland waters. Here we apply the first-order acidity balance model (FAB) to predict the maximum N leaching from 13 study catchments at future steady state. Using mean water chemistry and catchment soils data, along with long-term default values for N sink processes, we predict NO3-N leaching at much higher rates than currently are being measured in surface waters, with a mean increase of 10.5 kg ha-1 yr-1. As a result, mean acid neutralizing capacity would decline to less than 0 meq L-1 at 4 sites. While there are uncertainties associated with model parameterization relating to the short-term storage of N within catchment soils and vegetation, model outputs do indicate much greater leaching of N at some time in the future as steady-state is achieved. 相似文献
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4.
Samples were collected from 13 upland sites (main inflow and loch outflow) in the UK along an N deposition gradient of 12-50 kg ha-1 yr-1 to determine the relationship between N deposition and NO3 - concentrations in surface waters. There was no direct correlation between NO3 - leaching and soluble inorganic N deposition at these sites, but a significant relationship with NO3 - was found using a deposition function incorporating dissolved organic carbon (DOC) flux from each catchment. A similar but less significant relationship was found between NO3 - concentration and DOC:DON ratio in runoff water. Catchments showed evidence of N saturation, i.e., when mean NO3 - concentration exceeded 5 µeq L-1, when the mean DOC:DON ratio fell below an approximate value of 25. Five other large loch sites (LLS) with multiple subcatchments were used to test these relationships and for four of these mostly heathland sites the predicted NO3 - concentrations closely matched measured values. At the fifth site, where most subcatchments were forested, the deposition function and DOC:DON ratios gave conflicting predictions and both methods generally underestimated measured NO3 - concentrations. If the capacity of these catchments to retain deposited N is determined by C supply then many upland catchments in the UK may experience increasing NO3 - concentrations in runoff in the future at current or increased levels of N deposition. 相似文献
5.
Critical loads for nitrogen deposition on forest ecosystems 总被引：2，自引：0，他引：2
E. - D. Schulze W. De Vries M. Hauhs K. Rosén L. Rasmussen C. -O. Tamm J. Nilsson 《Water, air, and soil pollution》1989,48(3-4):451-456
Critical loads for N deposition are derived from an ecosystem's anion and cation balance assuming that the processes determining ecosystem stability are soil acidification and nitrate leaching. Depending on the deposition of S, the parent soil material, and the site quality critical N deposition rates will range between 20 to 200 mmol m?2 yr?1 (3 to 14 kg ha?1 yr?1) on silicate soils and reach 20 to 390 mmol m?2 yr?1 (3 to 48 kg ha?1) on calcareous soils. 相似文献
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7.
Fenn M. E. de Bauer L. I. Quevedo-Nolasco A. Rodriguez-Frausto C. 《Water, air, and soil pollution》1999,113(1-4):155-174
Mexico City experiences some of the most severe air pollution in the world. Ozone injury has been documented in sensitive tree species in urban and forested areas in the Valley of Mexico. However, little is known of the levels of other atmospheric pollutants and their ecological effects on forests in the Valley of Mexico. In this study bulk throughfall deposition of inorganic nitrogen (N) and sulfur (S) was measured for one year at a forested site upwind (east) and downwind (southwest) of Mexico City. Edaphic and plant (Pinus hartwegii Lindl.) indicators of N and S nutrient status were also measured. Streamwater NO3 - and SO4 2- concentrations were also determined as an indicator of watershed-level N and S loss. Annual bulk throughfall deposition of inorganic N and S at the high-pollution forested site 23 km southwest of Mexico City (Desierto de los Leones National Park; DL) was 18.5 and 20.4 kg ha-1. Values for N and S deposition at Zoquiapan (ZOQ), a relatively low-pollution site 53 km east of Mexico City, were 5.5 and 8.8 kg ha-1 yr-1. Foliar concentrations of N, foliar N:P and C:N ratios, extractable soil NO3 -, and streamwater NO3 - concentrations indicate that the forest at DL is N enriched, possibly as a result of chronic N deposition. Sulfur concentrations in current-year foliage were also slightly greater at DL than at ZOQ, but S concentrations in one-year-old foliage were not statistically different between the two sites. Streamwater concentrations of NO3 - ranged from 0.8 to 44.6 μEq L-1 at DL compared to 0.0 to 11.3 μEq L-1 at ZOQ. In summary, these findings support the hypothesis that elevated N deposition at DL has increased the level of available N, increased the N status of P. hartwegii, and resulted in export of excess N as NO3 - in streamwater. 相似文献
8.
Rainfall, stemflow, and throughfall were collected from 1996 to 1999 at two types of forest sites: (1) forests near the traffic roads and urban areas and (2) forests away from the urban areas at Mt. Gokurakuji, Hiroshima, western Japan in order to estimatethe effects of anthropogenic activities on atmospheric deposition. Rainfall deposition for major ions showed small differences between the sites. The NO3 - and SO4 2-concentrations in stemflow were higher at the urban-facing slope than at the mountain-facing slope. Throughfall deposition of NO3 - and SO4 2- was also higher at urban-facing slopes. Net throughfall (NTF) deposition (throughfall minus rainfall) of NO3 - and SO4 2- accounted for 77 and50% of the total throughfall deposition on urban-facing slopes, respectively, while it accounted for 44 and 23% on themountain-facing slopes, respectively. These results indicated a higher contribution from dry deposition on urban-facing slopes compared to mountain-facing slopes. Atmospheric N (NO3 - +NH4 +) deposition from throughfall was estimated to be around 17–26 kg N ha-1 yr-1 on urban-facing slopes, which was greater than the threshold of N deposition that could cause nitrogen leaching in Europe and the United States. The highload of atmospheric N deposition may be one of the factors bringing about the decline of pine forests on urban-facing slopesof Mt. Gokurakuji. 相似文献
9.
Ion leaching from a sugar maple forest in response to acidic deposition and nitrification 总被引：1，自引：0，他引：1
N. W. Foster P. W. Hazlett J. A. Nicolson I. K. Morrison 《Water, air, and soil pollution》1989,48(1-2):251-261
Year-to-year variation in acidic deposition within a mature sugar maple-dominated forest and in leaching of ions from the associated podzolic soil were examined at the Turkey Lakes Watershed between 1981 and 1986. Below-canopy inputs to the soil of SO4 2? and NO3 ? in throughfall averaged 640 and 295 eq. ha?1 yr?1; the corresponding ranges were 493–917 and 261–443 eq. ha?1 yr?1. The contribution of atmospheric deposition to SO4 2? NO3 ? and Ca2+ leaching decreased over the six years. During the study period, the mean annual volume-weighted NO3 ? concentration decreased in throughfall and forest-floor percolate and increased in the mineral-soil solution collected below the effective rooting zone. A substantial shift in the balance between SO4 2? and NO3 ?leaching from the mineral soil was observed; leaching of SO4 2?decreased and NO3 ? leaching increased with time. Leaching of Ca2+ and Mg2+ from the soil was increased as a result of excess NO3 ? production in the soil. The calculated output of NO3 ? from the soil, which averaged 1505 eq. ha?1 yr?1, considerably exceeded the atmospheric deposition of NO3 ?, whereas SO4 2? outputs were only moderately greater than inputs. 相似文献
10.
Soil Acidification Induced by Ammonium Sulphate Addition in a Norway Spruce Forest in Southwest Sweden 总被引：1，自引：0，他引：1
The contributions of different acidifying processes to the total protonload (TPL) of the soil in control plots (C) and ammonium sulphate treatedplots (NS) were studied in a Norway spruce stand in Southwest Sweden during 1988–1998. The annual deposition of inorganic nitrogen and sulphate was on average 18 kg N and 20 kg S ha-1. In addition the NS treated plots received 100 kg N and 114 kg S ha-1 annually. The amounts of nutrients added to the ecosystem by wet and dry deposition and the leaching at 50 cm depth were calculated. The net atmosphericproton load, the proton load by nitrogen transformations in the soil, the sulphate sorption/desorption in the soil and the excess base cation accumulation in biomass were calculated. There was no leaching of inorganic nitrogen from control plots during the study period. The net atmospheric proton deposition, originating from sulphuric and nitric acid deposition, was the main contributor to TPL in control plots. The addition of ammonium sulphate increased the leaching of ammonium, nitrate, sulphate, magnesium and calcium but not of potassium. The TPL in NS plots was about ten times that in control plots. The nitrogen transformation processes were the main contributors to TPL to NS soil, in the beginning by ammonium uptake and later also by nitrification. The pH decreased by 0.4 units in the mineral soil. The between-year variation in TPL during the eleven year period in C plots (200–1500 molc ha-1 yr-1) and in NS plots (1000–13000 molc ha-1 yr-1) was mainly dependent on the sorption or release of sulphate. Both in C and NS, the TPL was buffered mainly by dissolving solid aluminium compounds, most probably some Al(OH)3 phase. 相似文献
11.
To investigate which ecosystem parameters determine the risk and magnitude of nitrate leaching we compiled data from published and unpublished sources on dissolved inorganic nitrogen (DIN: NO3 -) in throughfall, DIN leaching loss in runoff or seepage water, and other ecosystem characteristics from 139 European forests. Not all data were available for all sites: 126 sites had at least one year's data on DIN inputs and DIN leaching loss; 40-50 sites had some data on soil chemistry and/or vegetation pools of N. DIN inputs in throughfall range between <1 and about 70 kg N ha-1 yr-1 and the losses with seepage or runoff range between <1 and 50 kg N ha-1 yr-1. Retention of N within the ecosystem increases with increasing DIN deposition and increasing proportion of NH4 + in deposition. The amount of N in needles and litterfall shows a significant linear relationship with throughfall deposition of DIN, whereas the C:N ratio of the organic (OH) horizon is uncorrelated to the level of throughfall-DIN flux. About 50% of the variability in DIN leaching loss can be explained by the flux of DIN in throughfall. Alternatively, about 60% of the variability in DIN leaching loss can be explained in a two-variable multiple regression combining the C:N ratio of the organic soil and the pH of the mineral soil. The survey data suggest that leaching of DIN from forest ecosystems in Europe is related in part to current DIN deposition and in part to the longer-term internal ecosystem N status as reflected in the chemistry of the humus and acidification status of the soil. 相似文献
12.
Fisher T.R. Lee K.-Y. Berndt H. Benitez J.A. Norton M.M. 《Water, air, and soil pollution》1998,105(1-2):387-397
The Choptank River basin is a coastal plain catchment dominated by agriculture (52% of land use). We summarize an 11 year data set of discharge and chemistry from a gauged subbasin. Discharge exhibited seasonal variations driven by seasonal evapotranspiration. There were double seasonal maxima of pH, NH4 +, NO3 -, total N, Fe, and total P concentrations in late spring and fall as the saturated zone rose and fell within the soil. Significant interannual variability in discharge was the result of rainfall variation. There were positive nterannual trends in NO3 - concentrations and negative interannual trends in NH4 + and PO4 3- concentrations. These data were combined to estimate N and P export coefficients of 3-11 kg N ha-1 yr-1 and 0.14-0.66 kg P ha-1 yr-1, driven primarily by interannual variations in discharge. These export coefficients are low compared to other coastal plain watersheds dominated by agriculture and may be responsible for the small anthropogenic effects in the Choptank estuary compared to other Chesapeake drainages. 相似文献
13.
Nitrogen deposition and leaching in European forests — Preliminary results from a data compilation 总被引：1，自引：0，他引：1
P. Gundersen 《Water, air, and soil pollution》1995,85(3):1179-1184
Input-output fluxes of nitrogen (N) and other ecosystem data from 64 European forest ecosystem studies have been compiled in a database (ECOFEE). Sites with high N deposition (up to 64 kg N ha–1yr–1) were characterized by high input of ammonia/ammonium. The deposition of oxidized N was usually only 10 to 15 kg N ha–1yr–1 Of all the sites included, 60 % leached more than 5 kg N ha–1yr–1. Elevated nitrate leaching appeared at inputs above 10 kg N ha–1yr–1. At several sites with inputs of 15–25 kg N ha–1yr–1 nitrate leaching approached the N input, whereas ammonium dominated sites with high input still retained c. 50 % of the input. 相似文献
14.
Nitrate leaching from intensively and extensively grazed grassland measured with suction cup samplers and sampling of soil mineral‐N I Influence of pasture management Leaching of nitrate (NO3—) from two differently managed cattle pastures was determined over four winters between 1993 and 1997 using ceramic suction cup samplers (with min. 34 cups ha—1); additionally, vertical soil mineral‐N content in 0—0.9 m (Nmin) was measured at the beginning and end of two winters (with min. 70 different sample cores ha—1). The experimental site in the highlands north‐east of Cologne, Germany, is characterized by high annual precipitation (av. 1,362 mm between 1993 and 1996). An intensive continuous grazing management (1.3 ha, fertilized with 250 kg N ha—1 yr—1, average stocking density 4.9 LU ha—1, = [I]) was tested against an extensive continuous grazing system (2.2 ha, av. 2.9 LU ha—1; no N‐fertilizer but an estimated proportion of Trifolium repens up to 15 % of total dry matter in the final year, = [E]). The results can be summarized as follows: (1) Mean leaching losses of NO3‐N, estimated from suction cup sampling and balance of drainage volume, were 85 kg NO3‐N ha—1 [I] and 15 kg NO3‐N ha—1 [E] during three wet winters with drainage volumes between 399 and 890 mm; in a dry winter with 105 mm calculated percolation, nitrate leaching decreased by a factor of 5 for both grazing treatments. (2) Although the amount of mineral N in soil (Nmin) sampled in late autumn showed differences between intensive and extensive grazing, the Nmin method permits no certain indication of the risk of NO3 leaching. For example, during the winter period 1994/95 a reduction of mineral N in the soil (0—0.9 m) in both grazing treatments was found (—33 [I] / —8 [E] kg NO3‐N ha—1 and —26 [I] / —21 [E] kg NH4‐N ha—1) whereas during the winter 1996/97 an increase in almost all mean mineral N values occurred (+10 [I] / +2 [E] kg NO3‐N ha—1 and +10 [I] / —10 [E] kg NH4‐N ha—1). (3) In spite of the differences between both methods, the experiment shows that NO3‐N leaching under extensive grazing could be reduced almost to levels close to those under mown grassland. 相似文献
15.
Hermann Hafner Joachim Bley Andr Bationo Peter Martin Horst Marschner 《植物养料与土壤学杂志》1993,156(2):169-176
On acid sandy soils of Niger (West Africa) fertilizer N recovery by pearl millet (Pennisetum glaucum L.) is often more than 100 per cent in years with normal or above average rainfall. Biological nitrogen fixation (BNF) by N2-fixing bacteria may contribute to the N supply in pearl millet cropping systems. For a long-term field experiment comprising treatments with and without mineral fertilizer (F) and with and without crop residue application (CR) a N balance sheet was calculated over a period of six years (1983-1988). After six years of successive millet cropping total N uptake (36-77 kg N ha?1 yr?1) was distinctly higher than the amount of fertilizer N applied (30 kg N ha?1 yr?1). The atmospheric input of NH4-N and NO3-N in the rainwater was about 2 kg N ha?1 yr?1, 70 % in the form of NH4-N. Gaseous NH3 losses from urea (broadcast, incorporated) were estimated from other experiments to amount to 36 % of the fertilizer N applied. Nitrogen losses by leaching (15 to > 25 kg N ha?1 yr?1) were dependent on the treatment and on the quantity and distribution of single rainfall events (>50 mm). Decline in total soil N content (0-60 cm) ranged from 15 to 48 kg N ha?1 yr?1. The long-term N balance (1983-1988) indicated an annual net gain between 6 (+CR-F) and 13 (+CR+F) kg N ha?1 yr?1. For the control (-CR-F) the long-term N balance was negative (10 kg N ha?1 yr?1). In the treatment with crop residues only, the N balance was mainly determined by leaching losses, whereas in treatments with mineral fertilizer application the N balance depended primarily on N removal by the millet crop. The annual net gain in the N balance increased from 7 kg ha?1 with mineral fertilizer to 13 kg ha?1 in the combination mineral fertilizer plus crop residues. In both the rhizosphere and the bulk soil (0-15 cm), between 9 and 45% of the total bacterial population were N2-fixing (diazotrophic) bacteria. The increased N gain upon crop residue application was positively correlated with an increase in the number of diazotrophic and total bacteria. The data on bacterial numbers suggest that the gain of N in the longterm N balance is most likely due to an N input by biological nitrogen fixation. In addition, evidence exists from related studies that the proliferation of diazotrophs and total bacteria in the rhizosphere due to crop residue application stimulated root growth of pearl millet, and thus improved the phosphorus (P) acquisition in the P deficient soil. 相似文献
16.
Three years of N application to a Cambic arenosol (Typic Udorthent) in two lysimeter series, one with and one without young saplings of Pinus sylvestris L. have produced significant changes in soil solution and leachate chemistry. An application of 30 kg N/ha*yr?1 significantly increased NO3 ? leaching from the soil. This N load was also sufficient to significantly increase the mobility of the phyto-toxic elements Al3+ and Mn2+, likewise to increase leaching of the important plant nutrients Ca2+, Mg2+ and K+. At a N load of 90 kg N/ha*yr?1 significant increase in NH4 + leaching was observed, but total leaching of NH4 + was still very low compared to NO3 ? leaching. No significant treatment effects were found for SO4 2?, Fe2+ and Cl? in the leachate. Trees grown in the lysimeters buffered the acidifying effect of N application and increased the leachate pH by 0.2 pH units compared to lysimeters without trees. 相似文献
17.
Elmi Abdirashid A. Madramootoo C. Egeh Mohamud Hamel C. 《Water, air, and soil pollution》2004,151(1-4):117-134
Nitrate-N (NO3 --N) pollution of water resources is a widely recognized problem. Water and nitrogen fertilizer are the two most important factors affecting NO3 --N movement to surface and groundwater. Field trials were conducted from 1998 to 2000 growing seasons to investigate the combined impacts of water table management (WTM) and N fertilization rate on NO3 --N concentration in the soil profile and in drain discharge. There were two water table treatments: free drainage (FD) with open drains at a 1.0 m depth from the soil surface and subirrigation (SI) with a target water table depth of 0.6 m below the soil surface, and two N fertilizer rates: 120 kg N ha-1 (N120) and 200 kg N ha-1 (N200) in a split-plot design. Compared to FD, SI reducedNO3 --N concentration in the soil by up to 50% averaged over the two N rates. Concentrations of NO3 --N in drainage water fromSI plots were lower than those from FD by 55 to 73%. These findings suggest that SI can be used as a means of reducing soil NO3 --N pollution and drainage water NO3 --N concentrations. 相似文献
18.
Abstract. In grazed dairy pasture systems, a major source of NO3– leached and N2O emitted is the N returned in the urine from the grazing animal. The objective of this study was to use lysimeters to measure directly the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO3– leaching and N2O emissions from urine patches in a grazed dairy pasture under irrigation. The soil was a free‐draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The use of DCD decreased NO3–‐N leaching by 76% for the urine N applied in the autumn, and by 42% for urine N applied in the spring, giving an annual average reduction of 59%. This would reduce the NO3–‐N leaching loss in a grazed paddock from 118 to 46 kg N ha–1 yr–1. The NO3–‐N concentration in the drainage water would be reduced accordingly from 19.7 to 7.7 mg N L–1, with the latter being below the drinking water guideline of 11.3 mg N L–1. Total N2O emissions following two urine applications were reduced from 46 kg N2O‐N ha–1 without DCD to 8.5 kg N2O‐N with DCD, representing an 82% reduction. In addition to the environmental benefits, the use of DCD also increased herbage production by more than 30%, from 11 to 15 t ha–1 yr–1. The use of DCD therefore has the potential to make dairy farming more environmentally sustainable by reducing NO3– leaching and N2O emissions. 相似文献
19.
Francisco Gavi William R. Raun Nicholas T. Basta Gordon V. Johnson 《Journal of plant nutrition》2013,36(2-3):203-218
The beneficial effect of sewage sludge in crop production has been demonstrated, but there is concern regarding its contribution to nitrate (NO3) leaching. The objectives of this study were to compare nitrogen (N) rates of sewage sludge and ammonium nitrate (NH4NO3) on soil profile (0–180 cm), inorganic N [ammonium nitrate (NH4‐N) and nitrate nitrogen (NO3‐N)] accumulation, yield, and N uptake in winter wheat (Triticum aestivum L.). One field experiment was established in 1993 that evaluated six N rates (0 to 540 kg·ha‐1·yr‐1) as dry anaerobically digested sewage sludge and ammonium nitrate. Lime application in 1993 (4.48 Mg ha‐1) with 540 kg N ha‐1·yr‐1 was also evaluated. A laboratory incubation study was included to simulate N mineralization from sewage sludge applied at rates of 45, 180, and 540 kg N ha‐1·yr‐1. Treatments did not affect surface soil (0–30 cm) pH, organic carbon (C), and total N following the first (1994) and second (1995) harvest. Soil profile inorganic N accumulation increased when ≥270 kg N ha‐1 was applied as ammonium nitrate. Less soil profile inorganic N accumulation was detected when lime was applied. In general, wheat yields and N uptake increased linearly with applied N as sewage sludge, while wheat yields and N uptake peaked at 270 kg N ha‐1 when N was applied as ammonium nitrate. Lime did not affect yields or N uptake. Fertilizer N immobilization was expected to be high at this site where wheat was produced for the first time in over 10 years (previously in native bermudagrass). Estimated N use efficiency using sewage sludge in grain production was 20% (average of two harvests) compared to ammonium nitrate. Estimated plant N recovery was 17% for sewage sludge and 27% for ammonium nitrate. 相似文献
20.
Karin Hansen Lars Vesterdal Annemarie Bastrup-Birk Jørgen Bille-Hansen 《Water, air, and soil pollution》2007,183(1-4):293-308
The aim of this study was to evaluate the suitability of the (Ca?+?Mg?+?K)/Al and the Ca/Al ratios in soil solution as chemical criteria for forest condition in critical load calculations for forest ecosystems. The tree species Norway spruce, Sitka spruce and beech were studied in an area with high deposition of sea salt and nitrogen in the south-western part of Jutland, Denmark. Throughfall and soil water were collected monthly and analysed for pH, NO3-N, NH4-N, K, Ca, Mg, DOC and Altot. Organic Al was estimated using DOC concentrations. Increment and defoliation were determined annually, and foliar element concentrations were determined every other year. The throughfall deposition was highest in the Sitka spruce stand (maximum of 40 kg N ha?1yr?1) and lowest in the beech stand (maximum of 11 kg N ha?1yr?1). The Sitka spruce stand leached on average 12 kg N ha?1yr?1 during the period 1988–1997 and leaching increased throughout the period. Only small amounts of N were leached from the Norway spruce stand whereas almost no N was leached from the beech stand. For all tree species, both (Ca?+?Mg?+?K)/Al and Ca/Al ratios decreased in soil solution at 90 cm depth between 1989 and 1999, which was mainly caused by a decrease in concentrations of base cations. The toxic inorganic Al species were by far the most abundant Al species at 90 cm depth. At the end of the measurement period, the (Ca?+?Mg?+?K)/Al ratio was approximately 1 for all species while the Ca/Al ratio was approximately 0.2. The lack of a trend in the increment rates, a decrease in defoliation as well as sufficient levels of Mg and Ca in foliage suggested an unchanged or even slightly improved health condition, despite the decreasing and very low (Ca?+?Mg?+?K)/Al and Ca/Al ratios. The suitability of these soil solution element ratios is questioned as the chemical criteria for soil acidification under field conditions in areas with elevated deposition rates of sea salts, in particular Mg. 相似文献