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PubMed2002

Changes in dissolved organic carbon during artificial recharge of groundwater in a forested esker in Southern Finland.

Sprinkling infiltration in a forested esker leading to artificial recharge of groundwater was studied in Southern Finland. Changes in dissolved organic carbon (DOC) and the molecular size distribution and chemical properties of the organic carbon were investigated during the infiltration process. Artificial groundwater was produced using sprinkling infiltration directly onto the forest floor. One result of lake water infiltration through the organic horizon and I m thick mineral soil layer was a slight net increase in the DOC concentrations from 9.4 mg/L in the infiltration water to 13.2 mg/ L in percolation water. This indicates that the forest soil represents a potential input of organic matter into infiltration water. However, the DOC concentrations decreased by 27-38% as the infiltration water percolated down through the unsaturated soil layer into the groundwater zone. At a distance of 1450 m from the infiltration area, the mean DOC concentration in the groundwater was below the recommended value for drinking water in Finland of 2.0 mg/L. There was a strong reduction in the concentrations of hydrophilic and hydrophobic acids, but only a slight decrease in hydrophilic neutral organic compounds during the infiltration process. The DOC in the production well consisted of low molecular size fractions. Larger molecular size fractions were removed effectively from the water during the infiltration process.

Carbon↗
PubMed2000

Formation of chloroform in spruce forest soil--results from laboratory incubation studies.

The release of chloroform, 1,1,1-trichloroethane, tetrachloromethane, trichloroethene and tetrachloroethene from an organic rich spruce forest soil was studied in laboratory incubation experiments by dynamic headspace analysis, thermodesorption and gas chromatography. Performance parameters are presented for the dynamic headspace system. For spruce forest soil, the results showed a significant increase in chloroform concentration in the headspace under aerobic conditions over a period of seven days, whereas the concentration of the other compounds remained fairly constant. A biogenic formation of chloroform is suggested, whereas for the other compounds anthropogenic sources are assumed. The addition of trichloroacetic acid to the soil increased the release of chloroform from the soil. It is, therefore, suggested that trichloroacetic acid also contributed to the formation of chloroform. Under the experimental conditions, the spruce forest soil released chloroform concentrations corresponding to a rate of 12 microg m(-2) day(-1). Data on chloroform production rates are presented and compared with literature results, and possible formation mechanisms for chloroform are discussed.

Chloroform↗
PubMed2001

Ni and Cu migration and accumulation in forest ecosystems on the Kola Peninsula.

Biogeochemical cycles of Ni and Cu in pine forests on the northern tree line (Kola peninsula) in the background and industry-disturbed areas have been investigated. Total, bio-available and exchangeable concentrations of Ni and Cu in the soil, atmospheric Ni and Cu fluxes and soil water migration, and metal uptake by plants are considered. In the polluted area, forest ecosystems are seen as biogeochemical barriers which may attenuate intensity of Ni and Cu migration down the soil profile. A quantitative assessment is given of the role of dominating forest plants and soil horizons as barriers to heavy metal fluxes.

Air Pollutants↗
PubMed2000

Ice storms and forest impacts.

Ice storms, or icing events, are important meteorological disturbances affecting forests over a surprisingly large portion of the USA. A broad belt extending from east Texas to New England experiences major ice storms at least once a decade; and truly major events occur in the heart of this belt once or twice a century. In the areas most affected, icing events are a factor that shapes stand composition, structure, and condition over wide areas. Impacts of individual storms are highly patchy and variable, and depend on the nature of the storm. Impacts also depend on how (or if) forest managers conduct subsequent salvage cuttings. Important research needs remain to be considered by the forest ecology and meteorology communities. At present, how ice storm frequency and severity may change with future climate change is unknown.

Disasters↗
PubMed2000

Pools and fluxes of mercury and methylmercury in two forested catchments in Germany.

Mercury (Hg) and methylmercury (CH3Hg+) are global pollutants, but little information is available on rates of atmospheric input, distribution and mobility in soils and catchments of central Europe. The objectives of this study were to investigate input and output fluxes of these compounds in a deciduous and a coniferous catchment in NE Bavaria (Germany), and to estimate pools and mobility of total Hg (Hgtot) and CH3Hg+ at the catchment scale. Bulk precipitation, throughfall, litterfall and runoff were collected biweekly from April 1998 to April 1999. Several soil profiles were sampled to estimate pools of Hg compounds in the catchments. In both catchments highest contents of Hgtot were found in the Oa layer of the forest floor (up to 500 ng g(-1)) and the soil storage of Hgtot calculated for a soil depth of 60 cm was approximately 890 g ha(-1) in the coniferous and 190 g ha(-1) in the deciduous catchment. Highest contents of CH3Hg+ in upland soils were observed in the Oi layer of the forest floor, and soil storage of CH3Hg+ was 4.35 g ha(-1) in the coniferous and 0.59 g ha(-1) in the deciduous catchment. The annual total deposition of Hgtot (total deposition not measured directly but calculated from throughfall and litterfall) was 541 mg ha(-1) year(-1) in the coniferous and 618 mg ha(-1) year(-1) in the deciduous catchment. Total deposition rates of CH3Hg+ were 3.5 and 2.6 mg ha(-1) year(-1). The contribution of litterfall to the total deposition of Hgtot and CH3Hg+ was 55% in the deciduous catchment. In the coniferous catchment, the contribution of litterfall to total deposition was only 29% for Hgtot, but 55% for CH3Hg+. By far the largest proportion of the deposited CH3Hg+ and Hgtot remained in the catchments (85% in the coniferous, 95% in the deciduous). As compared to remote Swedish catchments, deposition and output via runoff of Hgtot, were higher, but deposition and output of CH3Hg+ were lower in our catchments. In contrast to other studies, the annual budget revealed no differences in the mobility between the two species at the catchment scale. However, temporal patterns of the runoff fluxes and converse gradients of CH3Hg+ and Hgtot contents in the forest floor indicated differences in mobility on shorter time scales.

Environmental Monitoring↗
PubMed2000

Speciation of aluminium in forest soil extracts by size exclusion chromatography with UV and ICP-AES detection and cation exchange fast protein liquid chromatography with ETAAS detection.

Aluminium speciation was studied in forest soil extracts by size exclusion chromatography (SE) with UV and inductively coupled plasma-atomic emission spectrometric (ICP-AES) detection and cation exchange fast protein liquid chromatography (FPLC) with ETAAS detection. Size exclusion chromatography was performed on a Superdex HR75 10/30 column. Isocratic clution with 0.15 mol dm(-3) NaCl in TRIS-HCl buffer (pH = 5.5) was applied over 100 min at a flow rate of 0.35 cm(3) min(-1). The chromatographic run was followed at 278 nm and separated Al species also determined 'off line' in 0.875 cm3 fractions by ICP-AES. The analytical procedure enabled speciation of high molecular weight Al complexes. Cation exchange FPLC was performed on a Mono S HR 5/5 column. Aqueous 8 mol dm(-3) NH4NO3 linear gradient elution was applied over 10 min at a flow rate of 1 cm3 min(-1). Separated Al species were collected in 0.5 cm3 fractions and Al determined 'off line' by ETAAS. The analytical procedure enabled speciation of some positively charged monomeric Al species. Negatively charged species were eluted with the solvent front. The combination of the two analytical techniques was successfully employed in speciation of Al in forest soil extracts. Water was used as an extracting solution. It was found experimentally that 80-95% of Al in aqueous extracts of forest soils exists in monomeric Al forms. Water soluble Al (30-40%) is bound to high molecular weight complexes with humic substances. The remaining monomeric Al in the low molecular weight fraction exists as AIF2+, Al-oxalate and Al-citrate species.

Aluminum↗
PubMed2002

Forest fire indicators and mercury deposition in an intense land use change region in the Brazilian Amazon (Alta Floresta, MT).

Black carbon, charcoal and mercury fluxes were measured from sediment cores taken in an artificial water dam in an intense land use change area in the Alta Floresta district in the Brazilian Amazon, in order to characterize the differences in the evolution of human occupation patterns in the region during the last 18 years. A positive correlation between the black carbon and charcoal particle fluxes and the evolution of the Brazilian gross domestic production (GDP) was observed. Mercury fluxes showed a positive correlation with gold production and exhibited a distinct evolution pattern when compared to in relation to the forest fires indicators and Brazilian GDP. The fluxes of forest fires markers showed an increase in deforestation activities in the region after 1993. Mercury deposition showed a substantial decrease after 1994. The patterns of distribution in both forest fires tracers and gold mining tracers indicate substitution of the regional economic model. It also marked different antropogenic impact type in the ecosystem.

Brazil↗
PubMed1999

Distribution of radiocaesium in an Austrian forest stand.

Within an Austrian spruce stand, vertical distribution of radiocaesium in soil as well as 137Cs concentration in different forest ecosystem compartments including spruce and surface water were investigated 10 years after the Chernobyl accident. The total 137Cs inventory in the forest was estimated to be 46 kBq m-2 (ref. date: 86-05-01). From the collected data annual input rates via litterfall of 0.48% per year and output rates through waterflows of only 0.02% per year were derived. The results identify the high importance of forest soils as a sink for radiocaesium. The estimated ecological residence half-times turned out to be highest in the organic soil horizons (1-3 years per cm), whereas in mineral horizons the values decrease significantly. As a consequence, soil inventory represents more than 95% of the total, whereas only approximately 3.3% of the 137Cs inventory is stored in the living biomass of spruce trees and a further 0.5% in the phytomass of understorey vegetation.

Austria↗
PubMed2000

Critical examination of trace element enrichments and depletions in soils: As, Cr, Cu, Ni, Pb, and Zn in Swiss forest soils.

The aim of this study was to obtain an overview of trace element concentrations in Swiss forest soils and to critically assess the measured values with respect to anthropogenic input vs. lithogenic background. Twenty-three sites were selected which represent a broad range of natural forest sites, bedrock material and soil types of Switzerland. At each site, samples were collected from all genetic soil horizons down to a C or B/C horizon. Total concentrations of As, Cr, Cu, Ni, Pb, and Zn in all samples were determined by X-ray fluorescence spectrometry. There were distinct differences in the geological background values estimated from the concentrations measured in the samples from the lowest soil horizon. Background concentrations for Cr and Ni were lowest in granite and gneiss, whereas Pb and Zn were highest in limestone and marl. Enrichment or depletion of the trace elements was assessed using Zr as reference element. Within the same profile, the six trace elements showed completely different enrichment/depletion patterns with depth. The various natural processes and anthropogenic inputs that can lead to these patterns are critically discussed. Based on this critical assessment, pollution of the investigated forest soils was found to be most severe for Pb and Zn and to a somewhat lesser extent for As and Cu, whereas anthropogenic input of Cr and Ni seems to be less important. The data suggest that a critical evaluation of enrichment factors is a better tool to assess soil pollution with trace elements than the use of maximum allowable concentrations (MAC) for topsoil samples. The enrichment factors calculated as described here consider the effects of geological variation on metal abundances whereas the MAC does not. In order to obtain an estimate of soil solution concentrations, water extracts of the samples collected from a subset of 10 soil profiles were analyzed for the same trace elements. Solubility of all elements generally decreased with soil depth. An exception was Cr, Cu, and Ni solubility in the humus layer, which was lower than in the underlying mineral horizon. For all elements, solubility was higher for the collective of soil samples depleted in this element when compared to the samples, in which the element was enriched.

Arsenic↗
PubMed2003

Photochemical smog effects in mixed conifer forests along a natural gradient of ozone and nitrogen deposition in the San Bernardino Mountains.

Toxic effects of photochemical smog on ponderosa and Jeffrey pines in the San Bernardino Mountains were discovered in the 1950s. It was revealed that ozone is the main cause of foliar injury manifested as chlorotic mottle and premature needle senescence. Various morphological, physiological and biochemical alterations in the affected plants have been reported over a period of about 40 years of multidisciplinary research. Recently, the focus of research has shifted from studying the effects of ozone to multiple pollutant effects. Recent studies have indicated that the combination of ozone and nitrogen may alter biomass allocation in pines towards that of deciduous trees, accelerate litter accumulation, and increase carbon sequestration rates in heavily polluted forests. Further study of the effects of multiple pollutants, and their long-term consequences on the mixed conifer ecosystem, cannot be adequately done using the original San Bernardino Mountains Air Pollution Gradient network. To correct deficiencies in the design, the new site network is being configured for long-term studies on multiple air pollutant concentrations and deposition, physiological and biochemical changes in trees, growth and composition of over-story species, biogeochemical cycling including carbon cycling and sequestration, water quality, and biodiversity of forest ecosystems. Eleven sites have been re-established. A comparison of 1974 stand composition with data from 2000 stand composition indicate that significant changes in species composition have occurred at some sites with less change at other sites. Moist, high-pollution sites have experienced the greatest amount of forest change, while dryer low-pollution sites have experienced the least amount of stand change. In general, ponderosa pine had the lowest basal area increases and the highest mortality across the San Bernardino Mountains.

Air Pollutants↗
PubMed2000

Tropical forests and atmospheric carbon dioxide.

Tropical forests play a major role in determining the current atmospheric concentration of CO2, as both sources of CO2 following deforestation and sinks of CO2 probably resulting from CO2 stimulation of forest photosynthesis. Recently, researchers have tried to quantify this role. The results suggest that both the carbon sources and sinks in tropical forests are significantly greater than previously thought.

Journal Article↗
PubMed1999

The responsive C and N biogeochemistry of the temperate forest floor.

Soil organic matter is often viewed as comprising large pools of carbon and nitrogen with long residence times. However, the organic horizon that lies on the soil surface in temperate forests is a dynamic component of ecosystem carbon and nitrogen cycling. Responses to elevated inputs of nitrogen in this organic layer are emerging as key facets of ecosystem retention or loss of dissolved nitrogen. Research along nitrogen deposition gradients in the USA and Europe reveals a link between the ratio of organic carbon:nitrogen in the forest floor and nitrogen turnover rates, nitrification and leaching losses. Characteristics and processes in the forest floor are now recognized as key indicators or determinants of ecosystem 'nitrogen status'.

Journal Article↗
PubMed2001

The presence of some artificial and natural radionuclides in a Eucalyptus forest in the south of Spain.

Long-lived artificial radionuclides (137Cs, 90Sr) were studied in a Eucalyptus plantation located in the south-west of Spain. Radionuclide concentrations were determined in different types of samples corresponding to specific forest components (soil, trees, herbs and litter). Depth profile distributions were obtained in two selected core soils. Two layers were separately measured in three other cores. The concentration factor, defined as the ratio between the mean activity concentration in a component and the mean activity concentration in the soil, was calculated for each component. The biomass of different components was estimated in order to evaluate the total density concentration (Bq/ha) of the artificial radionuclides (137Cs, 90Sr) in the Eucalyptus plantation. The transfer of the radionuclides between the different forest components can be inferred from the results. Additionally, other naturally occurring radionuclides (40K, 226Ra, 228Ra, 228Ac) were determined for comparison. Transport of radionuclides from forest to a nearby pulp mill is also discussed.

Biomass↗
PubMed2002

The role of fungi in the transfer and cycling of radionuclides in forest ecosystems.

Fungi are one of the most important components of forest ecosystems, since they determine to a large extent the fate and transport processes of radionuclides in forests. They play a key role in the mobilization, uptake and translocation of nutrients and are likely to contribute substantially to the long-term retention of radiocesium in organic horizons of forest soil. This paper gives an overview of the role of fungi regarding the transfer and cycling of nutrients and radionuclides, with special emphasis on mycorrhizal symbiosis. Common definitions of transfer factors, soil-fungus and soil-green plant, including their advantages and limitations. are reviewed. Experimental approaches to quantify the bioavailability of radionuclides in soil and potential long-term change are discussed.

Biological Availability↗
PubMed2001

Ozone exposure thresholds and foliar injury on forest plants in Switzerland.

Canton Ticino in southern Switzerland is exposed to some of the highest concentrations of tropospheric ozone in Europe. During recent field surveys in Canton Ticino, foliar symptoms identical to those caused by ozone have been documented on native tree and shrub species. In Europe, the critical ozone level for forest trees has been defined at an AOT40 of 10 ppm.h O3 (10 ppm.h accumulated exposure of ozone over a threshold of 40 ppb) during daylight hours over a six-month growing season. The objective of this study was to determine the amount of ambient ozone required to induce visible foliar symptoms on various forest plant species in southern Switzerland. Species were grown within eight open-top chambers and four open plots at the Vivaio Lattecaldo Cantonal Forest Nursery in Ticino, Switzerland. Species differed significantly in terms of the ppb.h exposures needed to cause visible symptoms. The most to least symptomatic species grown within open-plots in this study rank as Prunus serotina, Salix viminalis, Vibrnum lantana, Rhamnus cathartica, Betula pendula, Rumex obtusifolius, Sambucus racemosa, Morus nigra, Prunus avium, Fraxinus excelsior, Rhamnus frangula, Alnus viridis, Fagus sylvatica and Acer pseudoplatanus. Similar rankings were obtained in the non-filtered chamber plots. The ranking of species sensitivity closely follows AOT values for the occurrence of initial symptoms and symptom progression across the remainder of the exposure season. Species that first showed evidence of foliar injury also demonstrated the most sensitivity throughout the growing season, with symptoms rapidly advancing over ca. 25-30% of the total plant leaf surfaces by the end of the observation period. Conversely, those species that developed symptoms later in the season had far less total injury to plant foliage by the end of the observation period (1.5 to < 5% total leaf area injured). The current European ambient ozone standard may be insufficient to protect native plant species from visible foliar injury, and many more native species may be sensitive to ozone-induced foliar injury than are currently known.

Environmental Monitoring↗
PubMed2002

Summer and autumn ozone fluxes to a forest in the Czech Republic Brdy Mountains.

In an effort to examine ozone (O3) deposition over a forest site in the Czech Republic, a low cost eddy flux experiment using slow response ozone and temperature sensors was implemented in July 1993 within the Brdy Mountains. Half-hour 2-Hz ozone and sensible heat measurements made at the Brdy Mountains for 98 days during the period 7 July 1994-20 October 1994 are analyzed and reported. While the Czech Brdy Mountains AOT40 level for the overall 104 day period was 7.6 ppm h (15.1 ppm h for the full 24-h summation), indicating a slight potential for 03 injury, the 1994 summer to autumn'measured forest O3 uptake was 2.4 (+/- 0.9) g m(-2), not unusually high compared to other studies. Average summer midday 03 fluxes and depositidn velocities were -1.0 (+/- 0.6) microg m(-2) s(-1) and 1.1 (+/- 0.7) cm s(-1). and autumn values were -0.36 (+/- 0.4) microg m(-2) s(-1) and 0.7 (+/- 0.5) cm s(-1) respectively. A unique contribution of this study is the first time demonstrated use of slow responding sensors for eddy covariance flux measurements at heights of 20 m above a forest.

Air Pollutants↗
PubMed2002

Nitrogen deposition in Mediterranean forests.

Atmospheric deposition of inorganic nitrogen was studied at two forested sites in the Montseny mountains (northeast Spain), peripheral to the Barcelona conurbation, and at a nearby lowland town, using bulk deposition, wet-only deposition, throughfall, and dry deposition inferred from branch-washes and surrogate surfaces (metacrylate plates). Bulk deposition inputs of ammonium and nitrate did not show significant temporal trends over a 16-year period. Bulk inputs of inorganic N were moderate, ranging from 6 to 10 kg N ha(-1) year(-1) depending on the time period considered and the degree of site exposure to polluted air masses from the Barcelona conurbation. Large dry-sedimented particles played a minor role, since wet-only inputs were virtually identical to bulk inputs. On the contrary, branch- and plate-washes indicated substantial dry inputs of N gases and small particles. Total atmospheric deposition was estimated at 15-22 kg N ha(-1) year(-1), most of it being retained within the studied broadleaved evergreen forests. Ecosystem N availability is thus likely to be increasing in these forests.

Air Pollutants↗
PubMed2003

Total and methyl mercury concentrations and fluxes from small boreal forest catchments in Finland.

Total mercury (TotHg) and methyl mercury (MeHg) concentrations were studied in runoff from eight small (0.02-1.3 km2) boreal forest catchments (mineral soil and peatland) during 1990-1995. Runoff waters were extremely humic (TOC 7-70 mg l-1). TotHg concentrations varied between 0.84 and 24 ng l-1 and MeHg between 0.03 and 3.8 ng l-1. TotHg fluxes from catchments ranged from 0.92 to 1.8 g km-2 a-1, and MeHg fluxes from 0.03 to 0.33 g km-2 a-1. TotHg concentrations and output fluxes measured in runoff water from small forest catchments in Finland were comparable with those measured in other boreal regions. By contrast, MeHg concentrations were generally higher. Estimates for MeHg output fluxes in this study were comparable at sites with forests and wetlands in Sweden and North America, but clearly higher than those measured at upland or agricultural sites in other studies. Peatland catchments released more MeHg than pure mineral soil or mineral soil catchments with minor area of peatland.

Ecosystem↗