The use of organic and mineral fertilizers in reforestation and in revitalization of declining protective forests in the Alps

BIOSOL and BACTOSOL, organic fertilizers based on residue from commercial antibiotic production, were tested as an alternative to mineral fertilizers in reforestation and in revitalization of Norway spruce stands (Picea abies) affected by forest decline. Due to its slow release of N and its stimulation of root growth, the organic fertilizer was superior to mineral fertilizer in enhancing growth of spruce planted in nutrient poor soil with low nutrient retention capacity, especially when combined with magnesium carbonate fertilizer. In mature stands, basal area increment responded positively and significantly to both mineral fertilizer and BIOSOL. So far no pronounced effects of fertilizer treatment on seed production and viability were observed. Fertilization in the moderate amounts employed had no adverse effects on microbial activity in the soil and mycorrhizal status and thus seems to be a safe method to increase tree vigor without dramatically changing site parameters.     

Fertilizer application in aid of plantation establishment in the savanna areas of Nigeria

Fertilizer trials were conducted to stimulate tree establishment and growth in the savanna region of Nigeria. The main nutrients investigated were N, P, K and B while the tree species included Azadirachta indica (Neem), Acacia auriculiformis, Eucalyptus spp., and Pinus spp. Borate application reduced the incidence of die-back of eucalypts and it also increased height growth. There was positive response to phosphate application by all species; phosphate reduced mortality considerably in pines on some sites. Response to N fertilizer by the species varied and related to type of N fertilizer. Urea was often found injurious to pines. There was strong interaction between N and P and usually response to N was not obtained on P-deficient sites. In all the cases where it was applied, there was no response to K. On more arid sites with poorly buffered soils, mineral fertilizers alone were insufficient to produce satisfactory tree growth. Application of animal manure on such sites increased survival and growth of Azadirachta indica, E. camaldulensis and A. auriculiformis.     

Fertilizer application in aid of plantation establishment in the savanna areas of Nigeria

Fertilizer trials were conducted to stimulate tree establishment and growth in the savanna region of Nigeria. The main nutrients investigated were N, P, K and B while the tree species includedAzadirachta indica (Neem),Acacia auriculiformis, Eucalyptus spp., andPinus spp. Borate application reduced the incidence of die-back of eucalypts and it also increased height growth. There was positive response to phosphate application by all species; phosphate reduced mortality considerably in pines on some sites. Response to N fertilizer by the species varied and related to type of N fertilizer. Urea was often found injurious to pines. There was strong interaction between N and P and usually response to N was not obtained on P-deficient sites. In all the cases where it was applied, there was no response to K. On more arid sites with poorly buffered soils, mineral fertilizers alone were insufficient to produce satisfactory tree growth. Application of animal manure on such sites increased survival and growth ofAzadirachta indica, E. camaldulensis andA. auriculiformis.     

Nutrient Fluxes in Planted Norway Spruce Stands of Different Age in Southern Poland

The fluxes of N–NO ₃ ^? , N–NH ₄ ⁺ , S–SO ₄ ^2? , Na⁺, K⁺, Ca²⁺ and Mg²⁺ from bulk precipitation to throughfall, stemflow and soil water surface flows were studied during 1999–2003 in planted Norway spruce forest stands of different ages (11, 24, 91 and 116 years in 1999). Also, runoff from the corresponding Potok Dupniański Catchment in the Silesian Beskid Mts was studied. N deposition was above the critical load for coniferous trees. The interception increased with stand age as well as leaf area index and so did the leaching from the canopy of almost all the analysed elements, but especially S–SO ₄ ^2? , H⁺ and K⁺. The nutrient fluxes varied with age of the spruce stands. Throughfall showed a high amount of S and of the strong acids (S–SO ₄ ^2? and N–NO ₃ ^? ) deposited to the soil, especially in older spruce age classes. Decomposition of organic matter caused a rise in water acidity and an increase in the concentrations of all the analysed ions; the leaching of minerals, however, was low (under 1%). The horizontal soil water flow showed an increase in the amount of water and amount of ions and contributed to a further decrease of pH at the soil depth of 20 cm. Element concentrations and their amounts increased with water penetrating vertically and horizontally on the slopes. Considerable amounts of ions, especially S and alkaline cations, were carried beyond the reach of the root system and then left the catchment. In the long term, these mineral losses will adversely affect health and growth of the spruce stands, and the increased acidity with stand age will presumably have negative effects on the runoff water ecosystem.     

Effects of air pollutants on mineral nutrition of Norway spruce and revitalization of declining stands in Austria

The vigor of Norway spruce stands in the Bohemian Forest of Austria was correlated with site factors, informations on historic land use, and chemical properties of the soils and spruce needles. The study confirmed that trees on west exposed slopes and plateaus in higher elevation have lower crown densities. The soils in the area are generally low in base saturation. Historical land use, such as litter raking, grazing and burning of biomass for potash led to nutrient depletion. Increasing deposition of atmospheric N during the last decades alleviated N stress, but increased Ca and Mg stress. N∶Mg ratios in needles of declining stands are wide, indicating N induced nutritional imbalances. PH values in the mineral topsoil are very low on W-slopes and plateaus. Measurements of pollutant deposition at three different sites indicate a strong influence of aspect and elevation on input rates. In a southwest exposed stand and a stand on a hilltop, facing the prevailing winds, substantially more S and N was recovered in the throughfall than in northeast exposed stand. Deposition rates in the open did not differ significantly. High NO₃ ^? concentrations in the soil solution of the southwest exposed site indicate N saturation of the system. In order to test the hypothesis that mineral deficiency and nutritional disorders contribute to the poor vigor of these stands, fertilizer experiments were established. Fertilization with a combination of an organic fertilizer (BACTOSOL^**)) and a magnesite fertilizer (BIOMAG^*)) significantly improved crown density, growth, seed viability, and mineral nutrition as inferred from foliar analysis. NO₃ ^? leaching in the combined BACTOSOL+BIOMAG treatment increased during the first and second growing season after fertilization but leveled off to values typical for the control plots after three years. Mg content of the soil solution increased both in the BIOMAG and the combined BACTOSOL+BIOMAG treatment. These experiments show that the nutritional status and the resilience of declining forests in the Bohemian Forests of Austria can be easily improved by proper fertilizer treatment.     

Simulation of nutrition of forests under stress using forgyte-11

Forest ecosystems are being subjected to an increasing variety of stresses for which we do not yet have rotation-length experience. Where we lack such experience, we cannot make experience-based predictions of the long-term effects of these stresses. While we are accumulating such experience, computer models can be used to make interim knowledge-based predictions. Most scientific knowledge has been produced by reductionist; disciplinary, process-based research. Such knowledge is a vital component of any explanation of natural or human-induced landscape phenomena, but cannot, in its reductionist, disciplinary form, provide an adequate basis on its own for long-term predictions about these phenomena. Such predictions require the development of computer models of ecosystem form and function based on the integration of knowledge from eco-physiology, autecology, community ecology, soil science, and climatology into ecosystem-level models that accurately describe the function and temporal dynamics of forest ecosystems.The ability of the ecosystem-level forest management simulation model FORCYTE-11 (FORest nutrient Cycling and Yield Trend Evaluator) to simulate forest stresses is described briefly. The question of how to model other stresses, such as air pollution, acid rain, climate change, soil compaction and erosion, and moisture competition is discussed, and the outline of a new model (FORECAST: FORestry and Environmental Change ASsessmenT) is presented.     

Nutritional stress inPicea sitchensis plantations in coastal British columbia: The effects ofGaultheria shallon and declining site fertility

Examples of nutritional stress in conifer seedlings caused by competing ericaceous species (e. g. Calluna andKalmia), have been reported in several parts of the world. Nutritional stress (primarily N deficiency) has been reported in Sitka spruce (Picea sitchensis) plantations growing in association with an ericaceous species, salal (Gaultheria shallon), in coastal British Columbia. Nutritional interference by salal was investigated on a chronosequence of sites up to 10 yr after clearcutting and slashburning. No direct evidence for an allelopathic contribution to the N stress was obtained. However, the rapid accumulation of salal fine roots and rhizomes, and the nutrients contained therein, provides a partial explanation for the observed stress symptoms. Soil analyses and seedling bioassays demonstrated a reduction in fertility in the period 8 to 10 yr after clearcutting and slashburning in comparison to the period 2 to 4 yr, which is believed to impose further nutritional stress on Sitka spruce. It is concluded that the nutritional stress in these Sitka spruce plantations is caused by a combination of (1) salal competition for nutrients and their subsequent immobilization in salal biomass, and (2) declining site fertility caused by the termination of the flush of nutrients (the “assart period”) that occurs in the immediate post-clearcutting and slashburning period. Sustaining good growth of plantations under such circumstances will require site nutrient management as well as vegetation management.     

Short-Term Physiological Responses of Mosses to Atmospheric Ammonium and Nitrate

Many bryophytes rely to a large extent on atmospheric deposition for their nutrient uptake.However, increasing levels of atmospheric ammonium NH ₄ ⁺ and nitrate NO ₃ ^- attract concern as to the possible harmful effects onbryophytes from these two nutrient sources. Changes in nitrate reductase (NR) activities, cation(Ca, K and Mg), total nitrogen (N) and organic acid concentrations were investigated for themosses, Racomitrium lanuginosum, Rytidiadelphus loreus and Philonotis fontana, in response to asingle field misting with 3 mol m^-3 NH ₄ ⁺ and NO ₃ ^- . Increases of 20% were recordedfor tissue N content, 48 hr after misting with N containing solutions. When labelled NH ₄ ⁺ or NO ₃ ^- were applied to R. Lanuginosum at 1, 3 and 6mol m^-3 concentrations, partitioning ofincorporated ¹⁵N between different tissueregions occured, with the highest N uptake in the upper stem and leaves. High concentrations ofapplied N resulted in reduced efficiency of N uptake. NH ₄ ⁺ applications caused declines in NR activities, organic acidsand cations, whereas, NO ₃ ^- treatments causedthe reverse response. Changes in cation contents, organic acids and NR activity reflect short-termregulation of N metabolism in the presence of defined N sources, as well as potential mechanismsof regulating cell pH homoeostasis. The consistency of physiological responses, especially NRactivities, over short-term pollution episodes, provides evidence for their use as indicators of both NH ₄ ⁺ and NO ₃ ^- pollution.     

Mercury in plants,soil and atmosphere near a chlor-alkali complex

Data of atmospheric Hg concentrations measured near the chlor-alkali complex of Rosignano Solvay (Livorno, Italy) show that the impact of the industry on the terrestrial environment is restricted to a close area around; background values (3 to 5 ng m^?3) are reached within a radius of 4 to 5 km. Hg levels in plants (Poa sp. Pinus nigra and Solidago sp.) and in soil show the highest values in the sampling stations near the electrolytic cells.     

MONITORING NITROGEN POLLUTION FROM SUGARCANE RUNOFF USING 15N ANALYSIS

In many forested wetlands of Louisiana, surface water quality is being deteriorated by nutrient input from adjacent agricultural production areas. This field study assesses the input of fertilizer N, applied to sugarcane fields, to forested wetlands. The potential use of natural abundance variations in ¹⁵N¹⁴N ratios for identification and tracing surface water N sources (NH ₄ ⁺ - and NO₃ ^--N) was evaluated. Runoff and surface water samples were collected from sugarcane fields and bordering forested wetlands (6 stations) over a 16 month period and analyzed for NH ₄ ⁺ -N, NO ₃ ^- -N, and associated NH ₄ ⁺ -δ¹⁵N and NO ₃ ^- -δ¹⁵N ratios. Fertilizer N draining into adjacent forested wetland was estimated to be only a small fraction of the amount applied. Concentrations of NH ₄ ⁺ - and NO ₃ ^- -N in the collected water samples were low and ranged from 0.02 to 1.79 mg L^-1. Isotopic analysis revealed NH ₄ ⁺ -δ¹⁵N and NO ₃ ^- -δ¹⁵N means were distinctive and may have the potential to be used as tracers of N contamination. The mean NH ₄ ⁺ -δ¹⁵N value was +18.6 ± 7.1‰ and the NO ₃ ^- -δ¹⁵N mean was +8.3 ± 3.1‰. Anomalously high NO ₃ ^- -δ¹⁵N values (>30‰) were attributed to denitrification.     

Influence of the nitrification inhibitor DMPP on the community composition of ammonia-oxidizing bacteria at microsites with increasing distance from the fertilizer zone

The effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N transformations and composition of ammonia-oxidizing bacteria (AOB) communities was investigated at the centimeter scale in a microcosm experiment under laboratory conditions. After 28 days, samples were collected from soil treated with urea or urea and DMPP at increasing distance from the fertilizer zone; this distance ranged from 0 to 5 cm in both horizontal and vertical directions. The results showed that DMPP application significantly increased soil pH and NH ₄ ⁺ -N and mineral N (NH ₄ ⁺ -N, NO ₃ ^? -N, and NO ₂ ^? -N) concentrations but decreased (NO ₃ ^? + NO ₂ ^? )-N concentration, and such effect was decreased by increasing the distance from the fertilizer zone. Fingerprint profiles of denaturing gradient gel electrophoresis showed that the number of bands decreased by increasing the distance from the fertilizer zone due to decreasing NH ₄ ⁺ -N concentrations in the urea treatment. Compared to urea applied alone, DMPP application increased NH ₄ ⁺ -N concentrations and decreased AOB diversity from 0 to 3 cm but promoted diversity from 3 to 5 cm distance from the fertilizer zone. A phylogenetic analysis showed that AOB communities were dominated by Nitrosospira cluster 3. Therefore, the nitrification inhibitor DMPP modified the composition of AOB communities by increasing the distance from the fertilizer zone and this probably was related to the changes in soil pH and inorganic N concentration.     

Precipitation Chemistry as an Indicator of Urban Air Quality in Mersin, North-Eastern Mediterranean Region

The chemical composition of precipitation in the city of Mersin on the Mediterranean coast of Turkey has been studied. Spatial and temporal variability of rainwater constituents have been determined from samples collected at two central and two suburban stations for the December 2003–May 2005 period. A total of 246 samples covering all precipitation events were analyzed to determine pH, conductivity, as well as major anion (Cl^?, ${\text{NO}}_3^ - $ , ${\text{SO}}_4^{2 - } $ ); major cation (H⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, ${\text{NH}}_4^ + $ ) and formaldehyde (HCHO) concentrations. The pH varied within a range of 4.8–8.5, with only 8 out of 246 samples being acidic (pH?<?5.6), and the remaining highly alkaline samples being neutralized by either ${\text{NH}}_4^ + $ in rainwater, or by CaCO₃ resulting from wet deposition of atmospheric dust. The volume weighted mean ΣAnion/ΣCation ratio was 0.49. The equivalent concentration of major ionic species followed the order: ${\text{Ca}}^{2 + } > {\text{HCO}}_3^ - > {\text{SO}}_4^{2 - } > {\text{Cl}}^ - > {\text{NH}}_4^ + > {\text{Na}}^ + > {\text{Mg}}^{2 + } > {\text{NO}}_3^ - > {\text{K}}^ + > {\text{H}}^ + $ . Formaldehyde concentrations varied in the range of 0.01–17.9 μM, and was found to be dependent on precipitation volume. Relatively higher ${\text{NH}}_4^ + $ , ${\text{SO}}_4^{2 - } $ , ${\text{NO}}_3^ - $ and HCHO concentrations, mainly of anthropogenic origin, measured near the city center suggest increased pollution from local anthropogenic sources, e.g., residential heating, industrial and/or traffic emissions. In general, the results of this study suggest local precipitation chemistry is more strongly influenced by natural (mineral dust and marine) sources compared to anthropogenic ones.     

Monitoring and Modeling Nitrate Persistence in a Shallow Aquifer

A modeling study on fertilizer by-products fate and transport was performed in an unconfined shallow aquifer equipped with a grid of 13 piezometers. The field site was located in a former agricultural field overlying a river paleochannel near Ferrara (Northern Italy), cultivated with cereals rotation until 2004 and then converted to park. Piezometers were installed in June 2007 and were monitored until June 2009 via pressure transducer data loggers to evaluate the temporal and spatial variation of groundwater heads, while an onsite meteorological station provided data for recharge rate calculations via unsaturated zone modeling. The groundwater composition in June 2007 exhibited elevated nitrate (NO ₃ ^? ) and chloride (Cl^?) concentrations due to fertilizer leaching from the top soil. The spatial distribution of NO ₃ ^? and Cl^? was heterogeneous and the concentration decreased during the monitoring period, with NO ₃ ^? attenuation (below 10?mg/l) after 650?days. A transient groundwater flow and contaminant transport model was calibrated versus observed heads and NO ₃ ^? and Cl^? concentrations. Cl^? was used as environmental tracer to quantify groundwater flow velocity and it was simulated as a conservative species. NO ₃ ^? was treated as a reactive species and denitrification was simulated with a first order degradation rate constant. Model calibration gave a low denitrification rate (2.5e^?3 mg-NO ₃ ^? /l/d) likely because of prevailing oxic conditions and low concentration of dissolved organic carbon. Scenario modeling was implemented with steady state and variable flow time discretization to identify the mechanism of NO ₃ ^? attenuation. It was shown that transient piezometric conditions did not exert a strong control on NO ₃ ^? clean up time, while transient recharge rate did, because it is the main source of unpolluted water in the domain.     

Effects of forest liming on the nutrient status of podzolic soils in Finland

The results of 40 long-term liming experiments in Scots pine and Norway spruce stands on mineral soil sites of varying fertility are reviewed in this paper. Limestone was broadcast at a dose of 2 t ha^?1 at the end of the 1950s and sampling was carried out at the end of the 1970s. Liming resulted in considerable accumulation (10 to 50% increase) of organic matter in the humus layer, but no changes in the mineral soil. The C/N ratio of the humus increased on the most productive sites. Liming brought about a long-term decrease in acidity of the humus layer on all site types, as well as a decrease in the mineral soil (0 to 10 cm) of the least productive ones. There was also a corresponding increase in base saturation. There was considerable accumulation of B and Mn in the humus layer. Sulphur was found to have been immobilized to a considerable extent in the humus layer, presumably as Al sulfate. Liming at fairly low doses (e.g. 2 t ha^?1) thus seems to be sufficient to counteract any future increases in soil acidification without bringing about any adverse effects (apart from perhaps B levels) on the nutrient status of the soil.     

Nitrogen and phosphorus fertilizations alter nitrogen,phosphorus and potassium resorption of alfalfa in the Loess Plateau of China

Abstract

Nutrient resorption from senescing leaves is a pivotal component of nutrient conservation strategy in a plant. Thus understanding the response of nutrient resorption to fertilization is of great help to minimize fertilizer use and further optimize fertilization management. However, little is known about how nutrient resorption responds to fertilization in N₂-fixing species. Nitrogen (N) and phosphorus (P) fertilizers were applied at different rates to alfalfa stands in the Loess Plateau. N fertilization hardly affected leaf N and K resorptions, but tended to increase P resorption. P fertilization increased N and K resorptions but affected P resorption in various ways. However, effect of N or P fertilization was significantly interplayed by P or N rate. At N100P60, alfalfa had the maximum biomass accumulation and less leaf resorption. Therefore, alfalfa could be performed well with 100?kg N ha^?1 and 60?kg P₂O₅ ha^?1 in this region.     

Nitrogen Leaching of Two Forest Ecosystems in a Karst Watershed

Karst watersheds are a major source of drinking water in the European Alps. These watersheds exhibit quick response times and low residence times, which might make karst aquifers more vulnerable to elevated nitrogen (N) deposition than non-karst watersheds. We summarize 13 years of monitoring NO ₃ ^? , NH ₄ ⁺ , and total N in two forest ecosystems, a Norway spruce (Picea abies (L.) Karst.) forest on Cambisols/Stagnosols (IP I) and a mixed beech (Fagus sylvatica L.) spruce forest on Leptosols (IP II). N fluxes are calculated by multiplying concentrations, measured in biweekly intervals, with hydrological fluxes predicted from a hydrological model. The total N deposition in the throughfall amounts to 26.8 and 21.1 kg/ha/year in IP I and IP II, respectively, which is high compared to depositions found in other European forest ecosystems. While the shallow Leptosols at IP II accumulated on average 9.2 kg/ha/year of N between 1999 and 2006, the N budgets of the Cambisols/Stagnosols at IP I were equaled over the study period but show high inter-annual variation. Between 1999 and 2006, on average, 9 kg/ha/year of DON and 20 kg/ha/year of DIN were output with seepage water of IP I but only 4.5 kg/ha/year of DON and 7.7 kg/ha/year of DIN at IP II. Despite high DIN leaching, neither IP I nor IP II showed further signs of N saturation in their organic layer C/N ratios, N mineralization, or leaf N content. The N budget over all years was dominated by a few extreme output events. Nitrate leaching rates at both forest ecosystems correlated the most with years of above average snow accumulation (but only for IP I this correlation is statistically significant). Both snow melt and total annual precipitation were most important drivers of DON leaching. IP I and IP II showed comparable temporal patterns of both concentrations and flux rates but exhibited differences in magnitudes: DON, NO ₃ ^? , and NH ₄ ⁺ inputs peak in spring, NH ₄ ⁺ showed an additional peak in autumn; the bulk of the annual NO ₃ ^? and DON output occurred in spring; DON, NO ₃ ^? , and NH ₄ ⁺ output rates during winter months were low. The high DIN leaching at IP I was related to snow cover effects on N mineralization and soil hydrology. From the year 2004 onwards, disproportional NO ₃ ^? leaching occurred at both plots. This was possibly caused by the exceptionally dry year 2003 and a small-scale bark beetle infestation (at IP I), in addition to snow cover effects. This study shows that both forest ecosystems at Zöbelboden are still N limited. N leaching pulses, particularly during spring, dictate not only annual but also the long-term N budgets. The overall magnitude of N leaching to the karst aquifer differs substantially between forest and soil types, which are found in close proximity in the karstified areas of the Northern Limestone Alps in Austria.     

Comparison of the macrophyte communities of a clearwater and a brownwater oligotrophic lake in Kejimkujik National Park,Nova Scotia

Beaverskin and Pebbleloggitch Lakes are small, proximate, acidic, oligotrophic, headwater lakes located in southwestern Nova Scotia. Beaverskin Lake has clear water, its euphotic zone is deep, and it has extensive beds of macrophytic vegetation that cover most of its bottom to a depth of 6.5 m. In contrast, the water of Pebbleloggitch Lake is highly colored by dissolved humic substances, and macrophytes are restricted to a narrow littoral fringe in depths of less than about 1.8 m. The most widespread macrophyte community in Beaverskin Lake occurs at depths of 2.0–6.5 m and is dominated by Sphagnum macrophyllum and Utricularia vulgaris, while the second most prominent community is littoral and is dominated by Eriocaulon septangulare, Lobelia dortmanna, and Eleocharis acicularis. The most prominent community in Pebbleloggitch Lake is dominated by the floating-leaved Nuphar variegatum rooted as deep as 1.8 m, while communities dominated by E. septangulare and Sphagnum spp. occur in water less than about 0.7 m deep.     

Role of air pollution in forest decline in Eastern North America

Evidence for and against three general mechanisms by which air pollution stress may cause or contribute to forest decline in eastern North America is examined. These mechanisms are (1) soil acidification, cation nutrient depletion, and subsequent Al toxicity, (2) direct and indirect effects of gaseous pollutants on the physiology and growth of forest trees; and (3) excess nitrogen deposition and subsequent soil acidification or physiological injury. Recent studies have revealed reductions in base saturation in some sites (both polluted and pristine), but the consequences of these changes to forest health and nutrition are not resolved. Aluminum toxicity may contribute to forest decline in red spruce (Picearubens L.) in high-elevation sites, but the data are contradictory. In forested landscapes in which regional decline (reduced tree growth and/or dieback) is reported, O₃ is the only gaseous pollutant documented as a contributing factor in the eastern North America. Whereas this secondary pollutant exhibits a regional distribution and occurs at potentially phytotoxic levels, a linkage between O₃ and forest decline is substantive only for loblolly pine (Pinustaeda Sarg.) in the southeast. Studies in high elevations do not support the hypothesis that O₃ or hydrogen peroxide directly affects the growth of red spruce or fraser fir (Abiesfraseri Poir.).However, preliminary data link chronic-level O₃ exposure with indirect effects, principally changes in drought tolerance in low-elevations (e.g., P. taeda) nd winter hardiness in high elevations (e.g., P. rubens).The emerging data on the role of air pollution as an environmental stress indicate that indirect effects (i.e., responses in which pollution alters the plant's ability to compete for limited resources or withstand other environmental stresses) are more important than direct effects (e.g., foliar necrotic lesions). Nitrogen saturation has been offered as an hypothesis for P. rubens decline, but no experimental data exist supporting this hypothesis.     

Deposition of air pollutants in a wind-exposed forest edge

The atmospheric deposition of air pollutants at a forest edge was studied by means of monitoring canopy throughfall at the edge and at five different parallel lines in the forest behind the edge. The investigation was carried out at a pine forest on the Swedish west coast. Throughfall and bulk deposition samples were analyzed for volume, SO ₄ ^2? , NO ₃ ^? , Cl^?, NH ₄ ⁺ , Na⁺, K⁺, Mg²⁺, Ca²⁺, and for pH. The results show that the throughfall flow at the edge was increased substantially for most ions. The ratios in throughfall flows between the edge and the line 50 m into the forest were for SO ₄ ^2? , 1.5, NO ₃ ^? 2.9, NH ₄ ⁺ 2.7, and Na⁺ 3.1. Since this effect is not only valid for forest edges but also for hillsides, hilltops, and edges between stands of different age, etc., there might be substantial areas which get much larger total deposition than the normally considered closed forest.