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1.
Ninety percent of the pines (P. Sylvestris) in the forests of Berlin (West) are classified as damaged. Needle and leaf analyses do not indicate nutrient deficiencies. In site of high S-inputs (55 kg ha?1 yr?1 with throughfall) total acid inputs are moderate (2.4 kmol ha?1 yr?1) due to their neutralization by carbonatic dusts. Heavy metal depositions have led to accumulations in the forest floor (e.g. Pb 150 mg kg?1, Cd 0.5 mg kg?1). The dominating soil type, a cambic arenosol (Ustipsamment) is strongly acidified (pH 3.2 – 4.0) and poor in available nutrients. On an experimental plot, the application of dolomitic lime (6.1 tons ha?1) and fertilizer (145 kg ha?1 K2SO4) led to a significant increase m pH and base saturation in the top 10 cm of the mineral soil after 2 yr. The data on element fluxes give evidence for increased mineralization rates, enhanced heavy metal accumulation in the forest floor and increased soil solution concentrations of potentially hazardous substances (Al, Cd, NO3). The lime application is discussed in terms of site specific effects on ecosystem stability and groundwater quality.  相似文献   

2.
Clear‐cutting of forest provides a unique opportunity to study the response of dynamic controls on dissolved organic matter. We examined differences in concentrations, fluxes and properties of dissolved organic matter from a control and a clear‐cut stand to reveal controlling factors on its dynamics. We measured dissolved organic C and N concentrations and fluxes in the Oi, Oe and Oa horizons of a Norway spruce stand and an adjacent clear‐cutting over 3 years. Aromaticity and complexity of organic molecules were determined by UV and fluorescence spectroscopy, and we measured δ13C ratios over 1 year. Annual fluxes of dissolved organic C and N remained unchanged in the thin Oi horizon (～ 260 kg C ha?1, ～ 8.5 kg N ha?1), despite the large reduction in fresh organic matter inputs after clear‐cutting. We conclude that production of dissolved organic matter is not limited by lack of resource. Gross fluxes of dissolved organic C and N increased by about 60% in the Oe and 40% in the Oa horizon upon clear‐cutting. Increasing organic C and N concentrations and increasing water fluxes resulted in 380 kg C ha?1 year?1 and 10.5 kg N ha?1 year?1 entering the mineral soil of the clear‐cut plots. We found numerous indications that the greater microbial activity induced by an increased temperature of 1.5°C in the forest floor is the major factor controlling the enhanced production of dissolved organic matter. Increasing aromaticity and complexity of organic molecules and depletion of 13C pointed to an accelerated processing of more strongly decomposed parts of the forest floor resulting in increased release of lignin‐derived molecules after clear‐cutting. The largest net fluxes of dissolved organic C and N were in the Oi horizon, yet dissolved organic matter sampled in the Oa horizon did not originate mainly from the Oi horizon. Largest gross fluxes in the Oa horizon (control 282 kg C ha?1) and increased aromaticity and complexity of the molecules with increasing depth suggested that dissolved organic matter was derived mainly from decomposition, transformation and leaching of more decomposed material of the forest floor. Our results imply that clear‐cutting releases additional dissolved organic matter which is sequestered in the mineral soil where it has greater resistance to microbial decay.  相似文献   

3.
The sink of CO2 and the C budget of forest biomes of the Former Soviet Union (FSU) were assessed with two distinct methods: (1) ecosystem/ecoregional, and (2) forest statistical data. The ecosystem/ecoregional method was based on the integration of ecoregions (defined with a GIS analysis of several maps) with soil/vegetation C data bases. The forest statistical approach was based on data on growing stock, annual increment of timber, and FSU yield tables. Applying the ecosystem/ecoregional method, the area of forest biomes in the FSU was estimated at 1426.1 Mha (106 ha); forest ecosystems comprised 799.9 Mha, non-forest ecosystems and arable land comprised 506.1 and 119.9 Mha, respectively. The FSU forested area was 28% of the global area of closed forests. Forest phytomass (i.e., live plant mass), mortmass (i.e., coarse woody debris), total forest plant mass, and net increment in vegetation (NIV) were estimated at 57.9 t C ha?1, 15.5 t C ha?1, 73.4 t C ha?1, and 1.0 t C ha?1 yr?1, respectively. The 799.9 Mha area of forest ecosystems calculated in the ecosystem/ecoregional method was close to the 814.2 Mha reported in the FSU forest statistical data. Based on forest statistical data forest phytomass was estimated at 62.7 t C ha?1, mortmass at 37.6 t C ha?1; thus the total forest plant mass C pool was 100.3 t C ha?1. The NIV was estimated at 1.1 t C ha?1 yr?1. These estimates compared well with the estimates for phytomass, total forest plant mass, and NIV obtained from the ecosystem/ecoregional method. Mortmass estimated from the forest statistical data method exceeded the estimate based on the ecosystem/ecoregional method by a factor of 2.4. The ecosystem/ecoregional method allowed the estimation of litter, soil organic matter, NPP (net primary productivity), foliage formation, total and stable soil organic matter accumulation, and peat accumulation (13.9 t C ha?1, 125.0 t C ha?1, 3.1 t C ha?1 yr?1, 1.4 t C ha?1 yr?1, 0.11, and 0.056 t C ha?1 yr?1, respectively). Based on an average value of NEP (net ecosystem productivity) from the two methods, and following a consideration of anthropogenic influences, FSU forests were estimated to be a net sink of approximately 0.5 Gt C yr?1 of atmospheric C.  相似文献   

4.
The release of base cations from chemical weathering is the fundamental process by which base cations lost through leaching or biological uptake are replenished. Soils with a high content of easily weatherable minerals will, in general, be readily able to neutralise incoming acidity and satisfy biological requirements through this supply of base cations from weathering. Conversely those soils with a low content of such minerals will be unable to buffer acid inputs or meet biological demands and will be vulnerable to acidification. It is evident therefore that an accurate estimate of the rate of chemical weathering is a prerequisite for any assessment of ecosystem sensitivity to acidification. The principal methods by which these calculations are made can be grouped into those based on element depletion in soil horizons calculated against a conservative element reference, catchment fluxes, laboratory studies and the use of mathematical models which utilise data from each of these sources. A review of the published data has been undertaken to determine if a systematic variation in weathering rates can be observed for a range of parent materials and/or methods used. Variations of 0.03–0.8 keq ha?1yr?1 for K+, 0.0–1.0 keq ha?1yr?1 for Na+, 0.01–1.39 keq ha?1yr?1 for Mg2+ and 0.0–5.8 keq ha?1yr?1 for Ca2+ were found. In general individual cation weathering rates determined from catchment fluxes, and also the model MAGIC, are dominated by Ca2+, with Mg2+ being the next most significant release rate. However it has not been possible to determine any other systematic variations due to the limited number of sites where weathering rate has been determined by more than one method.  相似文献   

5.
Dissolved organic matter (DOM) dynamics in spruce forested sites - examinations by analytical DOM fractionation Dissolved organic matter from two spruce forested sites in the Fichtelgebirge (Germany) was divided into different chemical and functional fractions, and the budgets of the fractions obtained were calculated. For both sites hydrophobic acids (HoS), hydrophilic acids (HiS), hydrophobic neutrals (HoN), hydrophilic neutrals (HiN), and hydrophilic bases (HiB) are discriminated concerning their dynamics in the compartments. Most of the HiN and HoN are mobilized by leaching from the forest canopy. Both neutral fractions are netto retained in the forest floor as well as in the mineral soil. In contrast, HoS and HiS are mainly released in the organic layers with a total input of organic acids from the forest floor into the mineral soil of ca 100 kg C (HoS) ha?1 a?1, and 50 kg C (HiS) ha?1 a?1, respectively. HoS are selectively better retained in the mineral horizons, leading to a mineral soil output of 2.4 – 4.4 kg C (HoS) ha?1 a?1, and 2.7 – 6.5 kg C (HiS) ha?1 a?1, respectively. It is concluded that the different mobility of the DOM fractions has implications for the mobilization and transport of organic pollutants and heavy metals.  相似文献   

6.
The proton budget for a Japanese cedar (Cryptomeria japonica) forest in Gunma Prefecture, Japan, was studied by estimating biogeochemical fluxes. The proton budgets were estimated for three individual compartments of the ecosystem: vegetation canopy, and the upper (O horizon + 0–10 cm) and lower (10–100 cm) soil layers. The dominant proton sources in the compartments were atmospheric deposition (1.2 kmol ha?1 yr?1), nitrification (5.1 kmol, ha?1 yr?1) and base-cation uptake by vegetation (8.0 kmol, ha?1 yr?1) respectively. These proton sources were neutralized almost completely within the individual compartments mainly by base-cation release from the canopy or the soil. The sum of internal proton sources was five times as large as that of external ones. Nitrogen input from the atmosphere was 2.2 kmol ha?1 yr?1, whereas its output from the lower soil layer was 3.9 kmol ha?1 yr?1, indicating that a net loss of nitrogen occurred in the ecosystem. However, this did not cause the acidification of soil leachates because of a sufficient release rate of base cations from the soil.  相似文献   

7.
Forestry studies were undertaken within the Turkey Lakes Watershed to determine the impact of long-range transport of air pollutants on biogeochemical processes in old-growth sugar maple forest on shallow Precambrian-derived till soils in the Algoma District of Ontario, Canada. Distributions of organic matter and macroelements were determined in the tree- and field-layer vegetation, the forest floor and the mineral soil of the study site. Annual tree growth was largely offset by mortality, resulting in a relatively stable standing stock of ca. 245 t ha?1. Annual aboveground litter production averaged 3.7 t ha?1 yr?1, chiefly in the form of deciduous leaf fall. The average pH of the precipitation (4.3) was reduced considerably by contact with the forest canopy. Throughfall was enriched with other elements, principally K and, to a lesser extent, Ca and Mg. The cationic composition of the forest-floor percolates, on the other hand, was dominated primarily by Ca and only to a lesser extent by Mg and K. The stand receives moderate acid deposition, mainly from average inputs of 33–36 kg ha?1 yr?1 of SO4 2? and 24–29 kg ha?1 yr?1 of NO3 ? distributed throughout the year. Atmospheric inputs add to substantial natural NO3 ? production, notably within the forest floor and upper mineral soil, and contribute to leaching of bases, principally Ca and Mg, from the rooting zone. Active recycling of elements together with weathering of primary minerals should assist in preserving the base status of the site.  相似文献   

8.
A regional study was conducted to assess current levels of trace metals in the forest floor, and to establish a baseline for future studies of metal accumulation. Quantitative forest floor samples collected from 78 sites in 9 states in the northeastern United States in 1978 and 1980 were analyzed for Zn, Cu, Ni, and Cd. Mean amounts present in the forest floor were 9.8 ± 1.9 (standard error of the mean), 1.7 ± 0.2, 0.86 ± 0.08, and 0.13 ± 0.01 kg ha?1, for Zn, Cu, Ni, and Cd, respectively. Mean concentrations were 133 ± 25, 19.5 ± 1.6, 11 ± 0.8, and 1.7 ± 0.1 mg kg?1, respectively. Differences in metal and organic matter concentrations and amounts among forest types were attributed to geographic location of specific forest types rather than to direct biotic influence. No element was strongly correlated with elevation for the entire sample area. Regional patterns of elemental amounts showed that trace metal levels are slightly higher in the southern part than in the northern part of the study region. Regional variation of Zn, Cu, Ni, and Cd in the forest floor was not indicative of atmospheric deposition except near point sources of pollution.  相似文献   

9.
We estimated the total inorganic fluxes of nitrogen (N), sulfur (S), chloride (Cl?, sodium (Na+, calcium (Ca2+, magnesium (Mg2+, potassium (K+ and hydronium (H+. The resistance deposition algorithm that is programmed as part of the CALMET/CALPUFF modeling system was used to generate spatially-distributed deposition velocities, which were then combined with measurements of urban and rural concentrations of gas and particle species to obtain dry deposition rates. Wet deposition rates for each species were determined from rainfall concentrations and amounts available from the National Acid Deposition Program (NADP) monitoring network databases. The estimated total inorganic nitrogen deposition to the Tampa Bay watershed (excluding Tampa Bay) was 17 kg-N ha?1 yr?1 or 9,700 metric tons yr?1, and the ratio of dry to wet deposition rates was ～2.3 for inorganic nitrogen. The largest contributors to the total N flux were ammonia (NH3 and nitrogen oxides (NO x at 4.6 kg-N ha?1 yr?1 and 5.1 kg-N ha?1 yr?1, respectively. Averaged wet deposition rates were 2.3 and 2.7 kg-N ha?1 yr?1 for NH4 + and NO3 ?, respectively.  相似文献   

10.
Mass flux assessment can provide information that is essential for a sustainable management of elements in agricultural soils. In this article, we present an assessment of regional-scale averages of zinc (Zn) fluxes into agricultural soils and crops of central Iran for the period 1997–2011, using available databases such as regional agricultural statistics. The basic units of the balances were 15 townships of the provinces Qom, Isfahan and Fars. Averaged over the entire study region, the net Zn input into arable soil resulting from all fertilizer inputs – Zn removal with harvested crops was 1515 g ha?1 yr?1 across the entire region, with a range of 438–3009 g ha?1 yr?1 among townships. Estimated average Zn inputs with manure, mineral fertilizers, sewage sludge and compost were 1254, 531, 19 and 7 g ha?1 yr?1, respectively. The input-to-output ratio of these fluxes ranged from 1.8 to 12.9 among townships and averaged 6.1 for the entire study area. Considering that outputs other than with crop harvests are minor, Zn stocks are rapidly building up in the soils of the study region. Uncertainties in the manure and crop removal data were the main sources of estimation uncertainty in this study.  相似文献   

11.
From 1986–1989, a team of scientists measured atmospheric concentrations and fluxes in precipitation and throughfall, and modeled dry and cloudwater deposition in a spruce-fir forest of the Great Smoky Mountains National Park which is located in the Southern Appalachian Region of the United States. The work was part of the Integrated Forest Study (IFS) conducted at 12 forests in N. America and Europe. The spruce-fir forest at 1740 m consistently received the highest total deposition rates (～2200, 1200, and 700 eq ha?1 yr?1 for SO4 2?, NO3 ?, and NH4 +). During the summers of 1989 and 1990 we used multiple samplers to measure hydrologie, SO4 2?, and NO3 ? fluxes in rain and throughfall events beneath spruce forests above (1940 m) and below (1720 m) cloud base. Throughfall was used to estimate total deposition using relationships determined during the IFS. Although the SO4 2? fluxes increased with elevation by a factor of ～2 due to higher cloudwater interception at 1940 m, the NO3 ? fluxes decreased with elevation by ～30%. To investigate further, we began year round measurements of fluxes of all major ions in throughfall below spruce-fir forests at 1740 m and at 1920 m in 1993–1994. The fluxes of most ions showed a 10–50% increase with elevation due to the ～70 cm yr?1 cloudwater input at 1920 m. However, total inorganic nitrogen exhibited a 40% lower flux in throughfall at 1920 m than at 1740 m suggesting either higher dry deposition to trees at 1740 m or much higher canopy uptake of nitrogen by trees at 1920 m. Differential canopy absorption of N by trees at different elevations would have significant consequences for the use of throughfall N fluxes to estimate deposition. We used artificial trees to understand the foliar interactions of N.  相似文献   

12.
Summary Total S, organic S and sulfate were measured in foliage, litter, roots, soil and solutions at a hardwood site within the Adirondack Mountains of New York. Sulfate as a percentage of total S was similar in foliage and litter (10%), but was greater in roots (30%). Sulfur constituents in the hardwood forest ecosystem were dominated by C-bonded S (60 g m–2) and ester sulfate (16 g m–2) which are formed by biological processes. Because sulfur mineralization (1.42 g m–2 yr–1) was greater than wet precipitation inputs (0.82 g m–2 yr–1), those factors that influence mineralization-immobilization processes are important in evaluating S cycling and sulfate fluxes in this ecosystem. Ester sulfate was formed within the forest floor by the soil biota and was leached to mineral horizons. Annual turnover of this pool was high (25%) within the mineral forest floor. Forest-floor C-bonded S was derived from root and above-ground litter, and substantial amounts were leached to mineral horizons. Calculated storage + outputs (1.64 g m–2 yr–1) was much greater than wet inputs (0.82 g m–2 yr–1).  相似文献   

13.
The Fukushima Daiichi nuclear power plant accident caused radioactive pollution in northeastern Honshu Island, Japan. This study examined the influence of snowmelt and rainfall on soil erosion processes and siltation of small lakes in Miyagi Prefecture (150 km northwest of the power plant). Two sets of slopes and lakes, respectively in pasture and forest catchments, were examined. Snowpack thickness, soil infiltration, surface runoff volume, soil and sediment physicochemical properties, Cs concentration of precipitation, meltwater, and rainwater, and lake siltation rates were determined. The total radioactive Cs content in precipitation was 0.7–7.4 BqˑL−1 and was below the Japanese standard (10 BqˑL−1). Total radioactive Cs was at the allowable level in water flowing down the pasture catchment slope (0.1–9.2 BqˑL−1) during snowmelt and rainfall, as well as in pasture (0.9–8.8 BqˑL−1) and forest (0.7–5.2 BqˑL−1) catchment lake water. There was no soil erosion (surface runoff) in the forest catchment. Soil losses in the pasture catchment were 23 due to rainfall and 9 kg ha−1 yr−1 following spring snowmelt. After snowmelt, a 0.5 and 0.2 mm thick layer of silt was deposited in pasture and forest catchment lakes, respectively, and 1.4 and 0.6 mm were deposited during the rainfall period. Average siltation rates were 1.9 and 0.8 mmˑyr−1 for pasture and forest catchment lakes, respectively. The upper layer of lake bottom sediments is represented mainly by silt fractions (2–50 μm), with high organic matter (4.0–5.7%) and radiocesium (1100–1600 kgˑha−1) contents.  相似文献   

14.
Prescribed fires are likely to re-emit atmospherically deposited mercury (Hg), and comparison of soil Hg storage in areas affected by prescribed fire to that in similar unburned areas may provide cross-validating estimates of atmospheric Hg deposition. Prescribed fires are common in the southeastern United States (US), a region of relatively high Hg deposition compared to the rest of the US, and are thus a potentially significant source of re-emitted atmospheric Hg. Accordingly, Hg was determined in soil layers of a prescribed fire experiment in a Florida longleaf pine forest. The Hg deficit in the annually burned forest floor relative to the forest floor unburned for 46 years (0.180 g ha?1?yr?1) agreed to within 5% of an independent estimate of Hg deposition for this site based on a regional monitoring network and computer model (0.171 g ha?1 yr?1). Consideration of other potential inputs and outputs of Hg suggested that atmospheric deposition was the primary input of Hg to the site. If extrapolated, these results suggest that prescribed fires in the southeastern US mainly re-emit atmospherically deposited Hg and that this re-emission is less than 1% of total US anthropogenic emissions. However, emissions at other sites may vary due to the possible presence of Hg in underlying geological strata and differences in fire regime and levels of atmospheric Hg deposition.  相似文献   

15.
Forest floor and mineral soil samples were collected from subalpine spruce-fir forests at 1000 m above mean sea level on 19 mountains in the northeastern United States to assess patterns in trace metal concentrations, acidity, and organic matter content. The regional average concentrations of Pb, Cu, and Zn in the forest floor were 72.3 (2.9 s.e.) μg g?1, 8.5 (0.7) μg g?1, and 46.9 (2.0) μg g?1, respectively. The regional average concentrations of Pb, Cu, and Zn in the mineral soil were 13.4 (0.8) μg g?1, and 18.2 (1.2) μg g?1, respectively. The regional average pH values of the forest floor and mineral soil were 3.99 (0.03), and 4.35 (0.03), respectively. The Green Mountains had the highest concentrations of Pb (105.7 μg g?1), and Cu (22.7 μg g?1), in the forest floor. They also had the highest concentrations of Cu (18.0 μg g?1), in the mineral soil. Site aspect did not significantly influence any of the values. Concentrations of Pb were lower than concentrations reported earlier in this decade at similar sites while concentrations of Cu and Zn remained the same. We believe that these lower Pb concentrations reflect real changes in forest Pb levels that have occurred in recent years.  相似文献   

16.
Net ecosystem exchange of carbon (FNEE) was estimated for a temperate broadleaf, evergreen eucalypt forest ecosystem at Tumbarumba in south-eastern Australia to investigate the processes controlling forest carbon sinks and their response to climate. Measurements at a range of temporal and spatial scales were used to make three different estimates of FNEE based on: (1) the difference between fluxes of carbon input by photosynthesis and output by autotrophic plus heterotrophic respiration, (2) changes over time in the carbon pools in the above- and below-ground biomass, soil and litter, and (3) micrometeorological flux measurements that provide a continuous estimate of the net exchange. A rigorous comparison of aggregated component fluxes and the net eddy fluxes within a flux tower source area was achieved based on an inventory of the site and a detailed sampling strategy. Measurements replicated in space and time provided mean values, confidence limits and patterns of variation of carbon pools and fluxes that allowed comparisons within known limits of uncertainty. As a result of comparisons between nighttime eddy flux and chamber measurements of respiration, a revised micrometeorological method was developed for estimating nighttime carbon flux using flux tower measurements. Uncertainty in the final estimate of FNEE was reduced through mutual constraints of each of these measurement approaches. FNEE for the period October 2001–September 2002, with average rainfall, was an uptake of 6.7 (5.1–8.3) tC ha?1 yr?1 estimated from component fluxes, and 5.4 (3.0–7.5) tC ha?1 yr?1 estimated from the revised eddy flux method. Biomass increment was 4.5 (3.7–5.4) tC ha?1 yr?1 and the remaining 0.9–2.2 tC ha?1 yr?1 could represent a carbon sink in the soil and litter pools or lie within the confidence limits of the measured fluxes. FNEE was reduced to ?0.1 to 2.4 tC ha?1 yr?1 during a period of drought and insect disturbance in October 2002–September 2003, with biomass increment being the main component reduced. The forest is a large carbon sink compared with other forest ecosystems, but this is subject to high-annual variability in response to climate variability and disturbance.  相似文献   

17.
We estimated the contribution of dissolved organic matter (DOM) to cation leaching and the translocation of acidity in three acid forest soils. The analysis was based on monitored (2 years) concentrations of dissolved organic carbon (DOC) in the field, measured total acidities of DOM, and measured as well as predicted weighted mean dissociation constants of the organic acids. Although the forest floor solutions were strongly acidic (pH 3.47–4.10), a considerable proportion of the organic acids was dissociated and organic anions represented 22–40% of the total anions in the mineral soil input. The flux of DOM-associated exchangeable protons from the forest floor to the mineral soil ranged from 0.35 (Wülfersreuth) to 3.72 (Hohe Matzen) kmol ha?1 yr?1. In the subsoil, this organic acidity may be neutralized by microbial decomposition of the organic acids, but a part of the hydrogen ions may dissociate and contribute to acidification of the soil solution and to weathering processes. Due to the pronounced retention of DOM in the mineral subsoil horizons, the contribution of DOM to the output of cations and acidity from the soil is much lower than in the surface horizons but still significant.?  相似文献   

18.
We lack an understanding of nitrogen (N) cycles in tropical forests of Africa, although the environmental conditions in this region, such as soil type, vegetation, and climate, are distinct when compared with other tropical forests. Herein, we simultaneously quantified N fluxes through precipitation, throughfall, and 0-, 15-, and 30-cm soil solutions, as well as litterfall, in two forests with different soil acidity (Ultisols at the MV village (exchangeable Al3+ in 0–30 cm, 126 kmolc ha–1) and Oxisols at the AD village (exchangeable Al3+ in 0–30 cm, 59.8 kmolc ha–1)) over 2 years in Cameroon. The N fluxes to the O horizon via litterfall plus throughfall were similar for both sites (MV and AD, 243 and 273 kg N ha–1 yr–1, respectively). Those values were remarkably large relative to other tropical forests, reflecting the dominance of legumes in this region. The total dissolved N flux from the O horizon at the MV was 28 kg N ha–1 yr–1, while it was 127 kg N ha–1 yr–1 mainly as NO3–-N (~80%) at the AD. The distinctly different pattern of N cycles could be caused by stronger soil acidity at the MV, which was considered to promote a superficial root mat formation in the O horizon despite the marked dry season (fine root biomass in the O horizon and its proportion to the 1-m-soil profile: 1.5 Mg ha–1 and 31% at the MV; 0.3 Mg ha–1 and 9% at the AD). Combined with the published data for N fluxes in tropical forests, we have shown that Oxisols, in combination with N-fixing species, have large N fluxes from the O horizon; meanwhile, Ultisols do not have large fluxes because of plant uptake through the root mat in the O horizon. Consequently, our results suggest that soil type can be a major factor influencing the pattern of N fluxes from the O horizon via the effects of soil acidity, thereby determining the contrasting plant–soil N cycles in the tropical forests of Africa.  相似文献   

19.
Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid deposition in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3 – 23.5 kg ha?1 yr?1 (annual inorganic total N deposition: 9.6 – 10.7 kgN ha?1 yr?1) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that in precipitation. The average soil surface nitrate concentration in 1998 was 140 µg g?1 (the range: 21.1 – 429 µg g?1, n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L?1 (the range: 2.38 – 20.6 mg L?1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.  相似文献   

20.
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   

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