Post-Glacial Lead Dynamics in a Forest Soil

The use of alkyl-Pb additives in gasoline during the 20th century resulted in widespread Pb pollution. The objective of this study was to determine the relative importance of atmospherically deposited Pb and Pb released through weathering to soil Pb pools at the Hubbard Brook Experimental Forest, New Hampshire. We employed a selective extraction method to estimate the amount of Pb that was: water-soluble + exchangeable (EX); inorganically bound (IB); organically bound (ORG); bound to amorphous oxides (AMOX); and bound in crystalline minerals (RES). After normalizing crystalline-Pb concentrations to the immobile element Ti, we estimated that 14.1 kg ha^-1 of Pb has been weathered from Hubbard Brook soils in the 12,000–14,000 yr since deglaciation – a long-term average release of 1.0–1.2 g ha^-1 a^-1. Analysis of Ti-normalized total Pb concentrations indicated a net post-glacial decrease of 7.2 kg ha^-1 in the total Pb pool – consisting of a net accumulation of 4.9 kg ha^-1 in the O horizon, and a net loss of 12.1 kg ha^-1 from mineral soil. Atmospheric deposition of Pb between 1926 and 1989 (estimated as 8.7 kg ha^-1) was a major source of Pb in the post-glacial period. Together, long-term weathering release and 20th century atmospheric deposition could account for all of the Pb in the EX, IB, ORG, and AMOX fractions. Lead from gasoline appears to constitute a major fraction of the total Pb burden in Hubbard Brook soils. Periodic analysis of soil Pb fractions may be useful in monitoring the fate of Pb in forest soils.     

Impact of Harvest Intensity on Long-Term Base Cation Budgets in Swedish Forest Soils

The effects of harvesting on the long-term mass balances of calcium (Ca), magnesium (Mg) and potassium (K) were evaluated on a regional level in Sweden. A new high-resolution weathering database was used together with estimates of total deposition, losses through harvest and leaching. Estimates were made for pine and spruce separately and for two harvesting intensity scenarios: stem harvesting and whole-tree harvesting. The mass balance calculations showed net losses of Ca and Mg in almost the whole country for both scenarios. The losses were smaller for pine than for spruce. The K balances were mainly positive for pine but negative for spruce. Leaching was a main factor in the mass balances, especially for Ca and Mg. Whole-tree harvesting in spruce forests led to substantially higher net losses of K and Ca than stem harvesting, according to the calculations. In the whole-tree harvesting scenario in spruce forests the estimated yearly net losses of Ca, Mg and K corresponded to at least 5%, 8% and 3% of the pools of exchangeable base cations, respectively, at 25% of the analysed sites. If losses of this magnitude continue the depletion of the pools of Ca, Mg and K may lead to very low base saturation of the soils, possibly accompanied by negative effects on soil fertility, runoff water quality, tree vitality and tree growth within a forest rotation in parts of Sweden. Avoiding whole-tree harvesting can improve the situation substantially for K, but the losses of Ca and Mg will still be significant.     

Levels and Characteristics of TOC in Throughfall, Forest Floor Leachate and Soil Solution in Undisturbed Boreal Forest Ecosystems

Total organic carbon (TOC) concentrations and fluxes in throughfall, forest floor leachate, soil solution (15 and 35 cm depths), and groundwater for coniferous forest sites in the boreal zone throughout Finland are described. Eight upland forest stands and one peatland forest stand are included in the study and the samples were collected during 1991–1997. Carbon (C) pools in the living tree biomass and soil compartments are presented, and the hydrophobic/hydrophilic and acidic components of dissolved organic carbon (DOC) in samples collected in autumn 1999 and spring 2000 from two of the sites are compared. Biomass (aboveground and belowground) pools of C averaged 88 Mg ha^-1 and soil (humus layer + 20 cm soil layer) averaged 55 Mg ha^-1. Stand throughfall TOC monthly mean concentrations ranged from 4.0 to 18.6 mg L^-1 and annual fluxes averaged 4.0 g m^-2 yr^-1. TOC concentrations in the water passing through the forest floor and soil decreased with depth. Plot mean concentrations at 35 cm depth values ranged from 4.1 to 21.2 mg L^-1 and fluxes averaged 3.7 g m^-2 yr^-1. Throughfall TOC concentrations were lowest during the winter, snowfall period and highest during the growing season. No monotonic trends in throughfall TOC concentrations over the 1991–1997 period were found. Soil solution TOC concentrations varied considerably, both within and between years. DOC in throughfall, forest floor, and soil solutions and in both autumn and spring seasons was dominated by hydrophobic fractions, particularly acids. Spruce canopies and litter appear to be important sources of soluble organic carbon, particularly acidic and hydrophobic compounds. Further studies on the nature and dynamics of organic carbon fluxing through coniferous, boreal forest ecosystems are needed.     

Stem Growth of Picea Abies in South Western Sweden in the 10 Years Following Liming and Addition of PK and N

Liming and/or application of specific nutrients have been proposed as countermeasures to the acidification of forest soils in southern Sweden. In this study the stem growth of Picea abies (L.) Karst. growing on acidic mineral soils in SW Sweden was investigated 10 years after additions of lime (Ca; 3000 kg lime ha⁻¹), lime plus P (25 kg ha⁻¹) and K (80 kg ha⁻¹), or N in low doses (2 × 10 kg ha⁻¹ yr⁻¹) (treatments: CaPK, Ca, N, CaPKN, and 2Ca2P2K, respectively). Compared with the control, stem growth was increased following all treatments involving lime additions, including liming alone. The PK addition did not seem to affect growth. The most plausible cause of the observed growth increases was that the lime additions indirectly increased the supply of plant-available N. The annual low-dose N addition did not significantly affect growth. This suggests that air-borne deposition of N, which supplies very small doses of N throughout the year, has a minor or even negligible influence on P. abies growth.     

Nitrogen Budget of a Spruce Forest Ecosystem After Six-year Addition of Ammonium Sulphate in Southwest Sweden

A nitrogen (N) budget was constructed for a period of 6 years (1988–1993) in a Norway spruce stand with current deposition of 19 kg N and 22 kg S ha⁻¹ year⁻¹. The stand was fertilized annually by addition of 100 kg N and 114 kg S ha⁻¹ (NS). Above and below ground biomass, litterfall, fine- root litter production, soil solution and net mineralization were measured to estimate pools, fluxes and accumulation of nitrogen. The average needle litterfall in control (C) and NS plots in 1993 was 2.2 and 2.5 ton ha⁻¹ year⁻¹, respectively. The fine root litter production prior to treatment (1987) was 4.4 ton ha⁻¹ year⁻¹ and after treatment (1993) it was 4.5 and 3.9 ton ha⁻¹ year⁻¹ in C and NS plots, respectively. Net N mineralization in the soil profile down to 50 cm was estimated to be 86 and 115 kg ha⁻¹ year⁻¹ in C and NS plots, respectively in 1992. During the treatment period the uptake of N in the needle biomass in C and NS plots was 29 and 77 kg ha⁻¹ year⁻¹, respectively. No N was accumulated in needles of C plot where the NS plots accumulated 34 kg ha⁻¹ year⁻¹. Of the annually added inorganic N to NS plots 47% was accumulated in the above and below ground biomass and 37% in the soil. N fluxes via fine-root litter production in the C plots were much higher (54 kg ha⁻¹ year⁻¹) than that via litterfall (29 kg ha⁻¹ year⁻¹). The corresponding values in the NS plots were 65 and 43 kg ha⁻¹ year⁻¹, respectively. Most of the net N mineralization occurred in the FH layer and upper mineral soil. It is concluded that fine root litter and litterfall play an important role in the cycling of N. Despite a high N uptake the losses of N in litterfall and fine root litter resulted in an incorporation of N in soil organic matter.     

Controls on leaching of N species in upland moorland catchments

Spatial and temporal changes in mobility of N species have been studied for three UK upland river networks, the Etherow in the South Pennines, the Nether Beck in the Lake District and the Dee in NE Scotland. The catchments are subject to N deposition at 35.1, 22.0 and 10.8–15.6 kg N ha^?1 yr^?1, respectively. The NH⁺ ₄ leaching appears to be predominantly regulated by flow path in more polluted upland catchments. It is greatest where water draining acidified peaty soils contributes more to total discharge. Soluble organic matter may provide the dominant counter anion. In the Etherow and Dee catchments, which are dominated by acid mineral and organic soils, at high discharge NO^? ₃ also appears to be associated with greater input of water from acidified soils. In contrast, for the Nether Beck, higher NO^? ₃ concentrations are associated with tributaries draining soils contributing water with higher alkalinity, suggesting nitrification is important. For the Etherow and Dee, dissolved organic N (DON) appears to originate predominantly from acidified, peaty soils. Spiking experiments with peat soil from the Etherow catchment confirmed the limited capacity of these soils to utilize inorganic N inputs, favouring equilibration with NH⁺ ₄ inputs and leaching losses of inorganic N throughout the year.     

Pools and Fluxes of Cations,Anions and Doc in Two Forest Soils Treated With Lime and Ash

The effect of liming and ash treatment on pools, fluxes and concentrations of major solutes was investigated at two forestedsites (Norway spruce) in S. Sweden. One site was treated 15 yrprior to sampling (Hasslöv-Hs; dolomite: 3.45 and 8.75 t ha^-1) and the other 4 yr before (Horröd-Hd; dolomite: 3.25 t ha^-1; wood ash: 4.28 t ha^-1). Effects of limingwere most pronounced in the O horizon solutions where higher pH,elevated Ca (120–700 M) and Mg (50–600 M) were observed as compared to control plots. The impact on the mineralsoil was more moderate. Soil solution concentrations were combined with modelled hydrological flow to calculate mass flows,which largely followed the trends of the solution composition. Liming also resulted in large increases of both exchangeable Caand Mg as well as effective cation exchange capacity (CEC_E;2–5 times the controls). The base saturation (BS%) was raised to 60–100% in the O horizon while in the mineral soil elevated values were only seen at the Hs site (20–60%; down to 10–15 cm depth for 8.75 t ha^-1). Ash treatment did notaffect either the soil solution nor the exchangeable pool to thesame extent as lime. In general, the impact at the Hd site was less pronounced especially in the mineral soil, which might be due to shorter treatment time (4 vs. 15 yr) and also differentthickness of the O horizon. Budget calculations for Ca and Mg originating from the lime showed that a major part of the Ca (40–100%) was retained in the top 30 cm of the soil, of which30–95% was present in the O horizon. The mobility of Mg wasgreater and it was estimated that a significant part had been leached from the profile (30 and 50 cm depth) after 15 yr. Increased mass flows of NO₃ ^- due to nitrification resulting from liming at the Hs site were calculated in the range120–350 mmol m^-2 yr^-1 (or 1.2–3.5 kmol ha^-1 yr^-1). There was significant leaching of Al (25–60 mmol m^-2 yr^-1), of which about 70% was inorganic, in thelower B horizon at both sites with no influence of liming.     

Controls on Leaching of N Species in Upland Moorland Catchments

Spatial and temporal changes in mobility of N species have been studied for three UK upland river networks, the Etherow in the South Pennines, the Nether Beck in the Lake District and the Dee in NE Scotland. The catchments are subject to N deposition at 35.1, 22.0 and 10.8–15.6 kg N ha^–1 yr^–1, respectively. TheNH ₄ ⁺ leaching appears to be predominantly regulated by flowpath in more polluted upland catchments. It is greatest where water draining acidified peaty soils contributes more to total discharge. Soluble organic matter may provide the dominant counter anion. In the Etherowand Dee catchments, which are dominated by acid mineral and organic soils, at high discharge NO ₃ ^– also appears to be associated with greater input of water from acidified soils. In contrast, for the Nether Beck, higher NO ₃ ^– concentrations are associated with tributaries draining soils contributingwater with higher alkalinity, suggesting nitrification is important. For the Etherow and Dee, dissolved organic N (DON) appears to originate predominantly from acidified, peaty soils. Spiking experiments with peat soil from the Etherow catchment confirmed the limited capacity of these soils to utilize inorganic N inputs, favouring equilibration with NH ₄ ⁺ inputs and leaching losses of inorganic N throughout the year.     

Fluxes of NO3-, NH4+, NO,NO2, and N2O in an Old Danish Beech Forest

The fluxes of the major nitrogen compounds havebeen investigated in many ecosystem studies over the world.However, only in few studies has attention been drawn to theimportance of the fluxes of minor gaseous nitrogen compoundsto complete the nitrogen cycle. In Denmark a detailed study onthe nitrogen cycle in an old beech forest has been implementedin 1997 at Gyrstinge near Sorø, Zealand. The study includesthe fluxes of the gases NO, N₂O and water mediatedtransport of NO₃ ^- and NH₄ ⁺. Measurementsof the fluxes of the gaseous compounds are performed withmicro-meteorological methods (eddy-correlation and gradient)and with chambers. Water mediated fluxes encompass rain,throughfall, stem-flow and leaching from the root zone. Thehydrological model is verified by TDR measurements. The findings show that the total water mediated N input tothe forest floor with throughfall and stemflow was 25.6 kg Nha^-1 yr ^-1, and open field wet deposition withprecipitation was 19.0 kg N ha^-1 yr ^-1. The internalcycling of N in the ecosystem measured as turnover oflitterfall and plant uptake was 100 kg N ha^-1 yr ^-1and 14 kg N ha^-1 yr ^-1, respectively. The fluxes ofthe gaseous N compounds NO and N₂O were of minorimportance for the total N turnover in the forest, NO_xemission being <1 kg N ha^-1 yr ^-1 and N₂Oemission from the soil being 0.5 kg N ha^-1 yr ^-1 withno significant difference between wet and dry soils.Concentrations of NO₃ ^- and NH₄ ⁺ in thesoil solution beneath the rooting zone are very small andconsequently the N leaching is almost negligible. It isconcluded that the nitrogen mass balance of this old beechforest ecosystem mainly is controlled by the input by dry andwet deposition and a large internal N cycle with a fast litterturnover. The nitrogen input tothe forest ecosystem which currently exceeds the critical loadby 5 kg N ha^-1 yr ^-1is mainly accumulated in the soil and no significant nitrateleaching is occurring.     

Effects of Acidification and its Mitigation with Lime and Wood Ash on Forest Soil Processes in Southern Sweden. A Joint Multidisciplinary Study

A joint multidisciplinary investigation was undertaken to studythe effects of lime and wood ash applications on two Norway spruce forest Spodosolic soils. The two sites, typical for southern Sweden, were treated in 1994 with either 3.25 t ha^-1 dolomite or 4.28 t ha^-1 wood ash (Horröd site) or in 1984 with either 3.45 or 8.75 t ha^-1 dolomite (Hasslöv site). Both sites show signs of acidification by atmospheric anthropogenic deposition and possessed low soil pH(4.3) and high concentrations of inorganic Al (35 M) in theupper illuvial soil solution. The prevailing soil conditions indicated perturbed soil processes. Following treatment with lime or wood ash, the soil conditions were dramatically altered. Cation exchange capacity (CEC) and base saturation (BS) was considerable increased after addition. Four years after application most of the added Ca and Mg was still present in the mor layer. Fifteen years after application,Mg in particular, became integrated deeper in the soil profile with a greater proportion lost by leaching incomparison to Ca. The concentrations of these ions were greatestin the mor layer soil solutions and Mg had higher mobility givinghigher concentrations also deeper in the profile. Four years after treatment, the application of wood ash and limeresulted in lower pH values and higher inorganic Al in mineral subsoil solutions compared to the untreated soil. We hypothesize that this was probably due to an increased flow of hydrogen ionsfrom the upper soil as a result of displacement by Ca and Mg ionsin the enlarged exchangeable pool. In contrast, fifteen years after lime and wood ash application, the mineral subsoil horizonspossessed a higher pH and lower soil solution Al content than theuntreated plots.Liming promoted soil microbial activity increasing soil respiration 10 to 36%. This is in the same range as net carbon exchange for forests in northern Sweden and could potentially have a climatological impact. The turnover of low molecularweight organic acids (LMWOA) by the soil microbial biomass werecalculated to contribute 6 to 20% to this CO₂ evolution.At Horröd, citrate and fumarate were the predominant LMWOAs with lowest concentrations found in the treated areas. In contrast, at the Hasslöv site, propionate and malonate were the most abundant LMWOAs. Higher microbial activity in the upper soil horizons was also theprobable cause of the considerably higher DOC concentrations observed in the soil solution of ash and lime treated areas. Thelime-induced increase in DOC levels at Hasslöv could be attributed to increases in the 3–10 kDa hydrophobic size fraction. Liming also promoted nitrification with high liming doses leading to extreme concentrations of NO₃ ^- (1 mM) in soil solution.At Hasslöv the community of mycorrhizal fungi was dramatically changed by the addition of lime, with only four of 24 species recorded being common to both control and treated areas.Many of the observed effects of lime and ash treatment can be viewed as negative in terms of forest sustainability. After fouryears of treatment, there was a decrease in the pH of the soil solution and higher concentrations of inorganic Al and DOC. Increased organic matter turnover, nitrification and NO₃ ^-leakage were found at Hasslöv. Considering that the weathering rate and the mineral nutrient uptake by trees is mostprobably governed by mycorrhizal hyphae etchingmineral grains in the soil, it is important to maintain this ability of the mycorrhizal fungi. The lime and ash-induced changed mycorrhizal community structure may significantly affect this capability. In light of this investigation and others, as reviewed by Lundström et al. (2003), the implications ofliming on forest health are multifaceted with complex relationships occurring over both space and time.     

Nitrate Leaching From a Mountain Forest Ecosystem with Gleysols Subjected to Experimentally Increased N Deposition

Nitrate leaching was measured over seven years of nitrogen (N) addition in a paired-catchment experiment in Alptal, central Switzerland (altitude: 1200 m, bulk N deposition: 12 kg ha^-1 a^-1). Two forested catchments (1500 m² each) dominated by Picea abies) were delimited by trenches in the Gleysols. NH₄NO₃ was added to one of the catchments using sprinklers. During the first year, the N addition was labelled with ¹⁵N. Additionally, soil N transformationswere studied in replicated plots. Pre-treatment NO₃ ^--N leaching was 4 kg ha^-1 a^-1 from both catchments, and remained between 2.5 and 4.8 kg ha^-1 a^-1 in the control catchment. The first year of treatment induced an additional leaching of 3.1 kg ha^-1, almost 90% of which was labelled with ¹⁵N, indicating that it did not cycle through the large N pools of the ecosystem (soil organic matter and plants). These losses partly correspond to NO₃ ^- from precipitation bypassing the soil due to preferential flow. During rain or snowmelt events, NO₃ ^- concentration peaks as the water table is rising, indicating flushing from the soil. Nitrification occurs temporarily along the water flow paths in the soil and can be the source of NO₃ ^- flushing. Its isotopic signature however, shows that this release mainly affects recently applied N, stored only between runoff events or up to a few weeks. At first, the ecosystem retained 90% of the added N (2/3 in the soil), but NO₃ ^- losses increased from 10 to 30% within 7 yr, indicating that the ecosystem became progressively N saturated.     

Long Term NH3 Flux Measurements above Grasslands in The Netherlands

Ammonia concentration gradients were measuredabove a grassland in an agricultural region fromJuly 1998 to July 2000 at the locationSchagerbrug in the Netherlands. They were used tocalculate the surface-atmosphere exchange ofammonia by means of the aerodynamic gradienttechnique. Measurements of the ammonia exchangewere also performed at a grass field that is partof a major wetland reserve in the centre of theNetherlands (Oostvaardersplassen), during theperiod June 1994–September 1995. At Schagerbrug,low net emissions or small depositions weremeasured during the winter months, and a netemission up to 5 kg NH₃ ha^-1 month^-1 in summer. The net annual emission was 26 kgN ha^-1, with manure application contributingabout 50% of this emission. AtOostvaardersplassen mainly deposition occurred,but large emissions were measured in autumn. Themeasured exchange fluxes are compared to modelevaluations that incorporate plant physiologicaldata, such as apoplastic NH₄ ⁺concentrations and pH. Results show a goodagreement between field observations and modelsimulations, although some improvements arenecessary during nighttime periods. Themeasurements are conducted within the GRAMINAEproject, a second tranche project of EC TERI.     

Nitrogen Turnover and Nitrate Leaching after Bark Beetle Attack in Mountainous Spruce Stands of the Bavarian Forest National Park

More than 85% of the mountainous spruce forest of the Bavarian Forest National Park died after bark beetle attack during the last decade. The elemental budget of intact stands and of different stages after the dieback was investigated. N-fluxes in throughfall of intact stands were lower (12–16 kg ha^-1 a^-1) than in an earlier study in an intact mountainous spruce stand in the Bavarian Forest National Park and were reduced in the first years after the dieback (3–5 kg N ha^-1 a^-1). Nitrate-N fluxes by seepage water of intact stands at 40 cm depth, which is below the main rooting zone, were moderate (5–9 kg ha^-1 a^-1). After the dieback of the stands, NH₄ ⁺ concentrations were increased in humus efflux as were NO₃ ^- concentrations in mineral soil. Due to the relatively high precipitation, dilution of the elemental concentrations in seepage was considerable.Therefore, NO₃ ^- concentrations were usually below the level of drinking water (806 μmol NO₃ ^- L^-1), with lowest concentrations after the snowmelt and highest in autumn. Nitrate concentrations were elevated from the first year until the 7th year after the dieback. Total NO₃ ^--N losses by seepage until the 7th year after the dieback equalled 543 kg N ha^-1. Aluminium fluxesafter the dieback were enhanced in the mineral soil from 55 to 503 mmol_c m^-2 a^-1 (average of 8 yr), K⁺ fluxes from 8 to 37 mmol_c m^-2 a^-1, and Mg²⁺ fluxes from 13 to 35 mmol_c m^-2 a^-1. The consequences for the nutritional status of the ecosystem, the hydrosphere, and forest management are discussed in the paper.     

Integrated biogas technology in the tropics. 2. Use of slurry for fish culture

The composite slurry from four 3.5-m³ ferrocement digesters fed a mixture of nightsoil, water hyacinth (Eichhornia crassipes) and rice straw was loaded into four 200-m² earth fish ponds at organic loading rates of 25, 50, and 100 kg chemical oxygen demand (COD) ha⁻¹ day⁻¹. Impressive extrapolated net fish yields of about 10 kg ha⁻¹ day⁻¹ (3.7 ton ha⁻¹ year⁻¹) were obtained at the highest organic loading rate, equivalent to loading rates of about 120 kg total solids and 4.5 kg total Kjeldahl nitrogen ha⁻¹ day⁻¹. There may be potential for even greater yields from biogas slurry fed fish ponds because the relationship between net fish yield and slurry loading rate was linear. Constraints in the development of integrated biogas technology for poor farmers in the tropics are likely to be associated with the digester rather than with the reuse of slurry for fish culture.     

Critical Loads and Exceedances of Acid Deposition and Associated Forest Growth in the Northern Hardwood and BorealConiferous Forests in Québec,Canada

We used the Québec forest monitoring network (`Réseaud'Étude et de Surveillance des Écosystèmes Forestiers' or RESEF)along with its atmospheric monitoring stations to assess criticalS and N loads and their combined soil acidification exceedancesfor natural ecosystems of the northern hardwood and borealconiferous forests in Québec, Canada. Critical loads (CL) forforest soil acidification were calculated using the simple mass-balance (SMB) approach and with the steady-state PROFILE model.Atmospheric deposition rates for water, S, N, Ca, Mg, Na, and K,for the years 1989–1993, and detailed, plot-specific forest andsoil characteristics were used as input. The SMB model alsorequired information regarding nutrient uptake and storage in theaboveground woody biomass. The CL calculations indicated that,from the 31 RESEF plots, 18 received atmospheric acidic inputs inexcess of their CL (55 and 61% of the hardwood and coniferousplots, respectively). The range of CL exceedance varied from 60to 470 eq ha^-1 yr^-1 for the hardwood stands, and from 10to 590 eq ha^-1 yr^-1 for the coniferous stands. The standswith CL exceedance were mainly located in the western and centralpart of the province. Stand growth associated with exceedanceclass of acidity was determined using the RESEF plots along withselected permanent forest survey plots having similar sitecharacteristics, but for which longer growth records wereavailable. We found a significant negative correlation betweenforest growth rates and critical soil acidification exceedancefor both the northern hardwood and the boreal conifer sites.Specifically, plots with critical load exceedances were found tohave a growth reduction of about 30% during the 1974–1982 andthe 1972–1990 measurement (plots with no soil acidificationexceedance served as a control). While this correlation is notnecessarily causal, it is nevertheless consistent with theexpectation that increased losses of soil base cations on accountof increased soil acidification should and could lead todeteriorating forest health conditions.     

Some limitations of sluiced fly ash as a liming material for acidic soils

Innovative methods are currently being sought to safely utilize and reduce the amount of sluiced fly ash stored in on-site facilities at thermal electric power facilities in Ontario, Canada. The objective of this study was to investigate the possibility of utilizing sluiced fly ash as a liming material on acidic soils. A greenhouse experiment was established to examine the influence of the ash on soil pH values and the yield and chemical composition of corn, soybeans, wheat and alfalfa grown on amended soil.The sluiced ash had an initial pH value of 9.1 (1:1 H₂O) and contained an equivalent CaCO₃ content of 11.5% (±0.2%) based on total content of Ca and Mg in the ash. Fly ash was applied at rates of up to 167 tonnes ha⁻¹ to samples of the surface horizon (0–15 cm) of an acidic clay textured soil found local to the power plant. Application of fly ash increased soil pH values but a high concentration of boron in the added ash limited plant growth. Results indicated that the sluiced ash could be used as a liming material at application rates of up to 110 tonnes ha⁻¹, on acidic, clay textured soils provided boron tolerant crops such as alfalfa were grown. Further research is required to establish the potential for leaching of boron to ground water and to determine the potential for plant uptake of other trace elements such as As and Se.     

Accumulation of pollutant nitrogen in calcareous and acidic grasslands: Evidence from N flux and 15N tracer studies

Semi-natural calcareous and acidic grasslands are known to be sensitive to increased atmospheric N deposition. However, the fate of pollutant N within these systems is unknown. This paper reports on the first studies to determine the fate of added N within a calcareous and an acidic grassland subject to long-term simulated enhanced N deposition. Intact soil/turf cores were removed from field plots treated for six years with enhanced N deposition (ambient +0, +35 and +140 kg N ha^?1 year^?1). Cores were inserted into lysimeters and output fluxes of N were monitored in detail. Complete N budgets—calculated from the N flux data—showed considerable accumulation of N within the treated grasslands, up to 76% and 38% of pollutant N in the calcareous and acidic grasslands respectively. In the second study, the short-term (21 day) fate of pollutant N was determined by tracing ¹⁵N labelled ammonium nitrate (+35 kg N ha^?1 year^?1) though the acidic and calcareous lysimeters into plant, soil and leachate pools. Up to 91% and 59% of ¹⁵N was recovered in soils and vegetation of the calcareous and acidic grasslands respectively, with negligible amounts recovered in soil extractable ammonium and nitrate (<0.3%) and in leachate (<0.02%). This rapid short-term immobilisation of pollutant N supports the long-term accumulation of the element calculated from the N flux study.     

Carbon sequestration: Do N inputs and elevated atmospheric CO2 alter soil solution chemistry and respiratory C losses?

Soil respiration is a large C flux which is of primary importance in determining C sequestration. Here we ask how it is altered by atmospheric CO₂ concentration and N additions. Swards of Lolium perenne L. were grown in a Eutric cambisol under controlled conditions with and without the addition of 200 kg NO^? ₃ ?N ha^?1, at either 350 ppm or 700 ppm CO₂, for 3 months. Soil respiration and net canopy photosynthesis were both increased by added N and elevated CO₂, but soil respiration increased proportionately less than fixation by photosynthesis. Thus, both elevated CO₂ and N appeared to increase potential C sequestration, although adding N at elevated CO₂ reduced the C sequestered as a proportion of that fixed relative to elevated CO₂ alone. Across all treatments below-ground respiratory C losses were predicted by root biomass, but not by soil solution C and N concentrations. Specific root-dependent respiration was increased by elevated CO₂, such that below-ground respiration per unit biomass and per unit plant N was increased.     

Changing of Lead and Cadmium Pools of Swedish Forest Soils

The aims of the paper are to; i)evaluate the rate and direction of present changesin lead (Pb) and cadmium (Cd) soil pools of Swedishforests; ii) discuss processes of importance forleaching of Pb and Cd in Swedish forest soils. Thepresently ongoing changes of Pb and Cd pools ofSwedish forest soils are evaluated by compilationof data from the literature and unpublishedsources. It is concluded that Cd pools arepresently decreasing in larger areas of Sweden. Therate of decrease is mainly determined by soilacidity status; Cd leaching is regulated by ionexchange with Ca²⁺, Mg²⁺, Al³⁺ andH⁺, and is higher in acid soils. The Pb poolsare presently increasing with 0.1 to 0.3 percentannually in the soil down to 0.5 meter. Pb isredistributed from the O horizon to the B horizon,most pronounced in spruce forests; the Pb pools ofthe O horizon are presently not increasing, but isslightly decreasing by 0.1 to 0.2 percent annually. The leaching of Pb in the soil is controlled byfactors regulating the solubility of organicmatter.     

Accumulation of pollutant nitrogen in calcareous and acidic grasslands: Evidence from N flux and 15N tracer studies

Semi-natural calcareous and acidic grasslands are known to be sensitive to increased atmospheric N deposition. However, the fate of pollutant N within these systems is unknown. This paper reports on the first studies to determine the fate of added N within a calcareous and an acidic grassland subject to long-term simulated enhanced N deposition. Intact soil/turf cores were removed from field plots treated for six years with enhanced N deposition (ambient +0, +35 and +140 kg N ha^–1 year^–1). Cores were inserted into lysimeters and output fluxes of N were monitored in detail. Complete N budgets—calculated from the N flux data—showed considerable accumulation of N within the treated grasslands, up to 76% and 38% of pollutant N in the calcareous and acidic grasslands respectively. In the second study, the short-term (21 day) fate of pollutant N was determined by tracing ¹⁵N labelled ammonium nitrate (+35 kg N ha^–1 year^–1) though the acidic and calcareous lysimeters into plant, soil and leachate pools. Up to 91% and 59% of ¹⁵N was recovered in soils and vegetation of the calcareous and acidic grasslands respectively, with negligible amounts recovered in soil extractable ammonium and nitrate (<0.3%) and in leachate (<0.02%). This rapid short-term immobilisation of pollutant N supports the long-term accumulation of the element calculated from the N flux study.