Bioactivity in limed soil of a spruce forest

Summary The stimulative effect of lime on the bioactivity of various soil horizons was demonstrated by the ATP test, and respiration and microcalorimetric measurements, but not by FDA hydrolysis or the iron reduction test. The latter showed clear inhibition. When the natural structure of layers was saved while sampling, a smaller stimulation of bioactivity was observed than in the case of mixing natural layers. No stimulation was recorded when the lime layer was removed.     

Isotope (C and C) analysis of deep peat CO2 using a passive sampling technique

We developed and tested a new method to collect CO₂ from the surface to deep layers of a peatland for radiocarbon analysis. The method comprises two components: i) a probe equipped with a hydrophobic filter that allows entry of peat gases by diffusion, whilst simultaneously excluding water, and, ii) a cartridge containing zeolite molecular sieve that traps CO₂ passively. We field tested the method by sampling at depths of between 0.25 and 4 m at duplicate sites within a temperate raised peat bog. CO₂ was trapped at a depth-dependent rate of between ∼0.2 and 0.8 ml d⁻¹, enabling sufficient CO₂ for routine ¹⁴C analysis to be collected when left in place for several weeks. The age of peatland CO₂ increased with depth from modern to ∼170 BP for samples collected from 0.25 m, to ∼4000 BP at 4 m. The CO₂ was younger, but followed a similar trend to the age profile of bulk peat previously reported for the site (Langdon and Barber, 2005). δ¹³C values of recovered CO₂ increased with depth. CO₂ collected from the deepest sampling probes was considerably ¹³C-enriched (up to ∼+9‰) and agreed well with results reported for other peatlands where this phenomenon has been attributed to fermentation processes. CO₂ collected from plant-free static chambers at the surface of the mire was slightly ¹⁴C-enriched compared to the contemporary atmosphere, suggesting that surface CO₂ emissions were predominantly derived from carbon fixed during the post-bomb era. However, consistent trends of enriched ¹³C and depleted ¹⁴C in chamber CO₂ between autumn and winter samples were most likely explained by an increased contribution of deep peat CO₂ to the surface efflux in winter. The passive sampling technique is readily portable, easy to install and operate, causes minimal site disturbance, and can be reliably used to collect peatland CO₂ from a wide range of depths.     

Biomass distribution of a microarthropod community in spruce forest soil

It has been previously demonstrated that fractal habitat features, combined with the allometric relationship between body size and metabolic rate, can sufficiently predict the biomass distribution in arthropod communities. This study shows that the relationship between biomass B and abundance N in a community of soil microarthropods is flatter than might be predicted by a combination of hypotheses concerning the (1) fractal dimension of pore surface, (2) metabolic rate, and (3) accessibility of soil pores. The relationship between B and N is N B ^-0.80 for the size classes to the right of the mode of the biomass distribution. Since the relationship between B and metabolic rate M is M B ^0.81, the energy use per size class is independent of size (B ^-0.80×B ^0.81 B ⁰) for a broad range of size classes with the exception of very small microarthropods.     

Patterns of acid deposition to a Danish spruce forest

Bulk precipitation and bulk throughfall was collected during the period September to November 1984 in a Danish spruce forest. Samples were analyzed for all major anions and cations as well as strong and total acidity. The acid load to the forest ecosystem was estimated adding the throughfall fluxes of protons (79 eq ha^?1mo^?1), ammonium (99 eq ha^?1mo^?1) and a calculated estimate oflthe protons buffered by exchange processes in the canopy (75 eq ha^?1 mo^?1). This is still a minimum estimate but it exceeds the proton load determined by pH measurement in bulk throughfall and bulk precipitation by factors 3 and 6, respectively. Throughfall fluxes of all major cations and anions except ammonium decreased with distance from the trunk.     

Vertical gradients of potential enzyme activities in soil profiles of European beech,Norway spruce and Scots pine dominated forest sites

Management of forest sites has the potential to modulate soil organic matter decomposition by changing the catalytic properties of soil microorganisms within a soil profile. In this study we examined the impact of forest management intensity and soil physico-chemical properties on the variation of enzyme activities (β-glucosidase, β-xylosidase, α-glucosidase, phenol oxidase, N-acetyl-glucosaminidase, l-leucine aminopeptidase, phosphatase) in the topsoil and two subsoil horizons in three German regions (Schorfheide-Chorin, Hainich-Dün, Schwäbische Alb). The sandy soils in the Schorfheide-Chorin (SCH) showed lower ratios of the activity of carbon (C) acquiring enzymes (β-glucosidase) relative to nitrogen (N) acquiring enzymes (N-acetyl-glucosaminidase + l-leucine aminopeptidase), and activity of C acquiring enzymes relative to phosphorous (P) acquiring enzymes (phosphatase) than the finer textured soils in the Hainich-Dün (HAI) and Schwäbische Alb (ALB), indicating a shift in investment to N and P acquisition in the SCH. All enzyme activities, except phenol oxidase activity, decreased in deeper soil horizons as concentrations of organic C and total N did, while the decrease was much stronger from the topsoil to the first subsoil horizon than from the first subsoil to the second subsoil horizon. In contrast, phenol oxidase activity showed no significant decrease towards deeper soil horizons. Additionally, enzyme activities responsible for the degradation of more recalcitrant C relative to labile C compounds increased in the two subsoil horizons. Subsoil horizons in all regions also indicate a shift to higher N acquisition, while the strength of the shift depended on the soil type. Further, our results clearly showed that soil properties explained most of the total variance of enzyme activities in all soil horizons followed by study region, while forest management intensity had no significant impact on enzyme activities. Among all included soil properties, the clay content was the variable that explained the highest proportion of variance in enzyme activities with higher enzyme activities in clay rich soils. Our results highlight the need for large scale studies including different regions and their environmental conditions in order to derive general conclusions on which factors (anthropogenic or environmental) are most influential on enzyme activities in the whole soil profile in the long term at the regional scale.     

Core sampling technique for bulk density and porosity determination on a clay loam soil

Seasonal fluctuations in bulk density and porosity determined from soil cores have been observed to be independent of soil and cropping treatments on the clay and clay loam soils of southwestern Ontario. An experiment was conducted to determine if the fluctuations may be a result of inconsistencies in core sampling technique. Three core sampling techniques were compared on five dates on each of four long-term cropping treatments which provided a range in soil water contents and structure. The core sampling techniques compared were: (1) a typical hand-held, hammer driven, double cylinder core sampler with the recommended procedure; (2) a typical hand-held, hammer driven, double cylinder core sampler with an excess number of blows; (3) pressing the double cylinder core sampler into the soil hydraulically. Variations in core sampling technique significantly affected the observed values of bulk density, total porosity, and air-filled porosity at field soil water contents ranging from 12.6 to 23.8% by weight. However, hammering, compared with hydraulically pressing, the core sampler into the soil, appears to cause more distortion within the soil core which increases variability. The effect of sampling date, and its inherent effect on soil moisture, was generally greater than the effect of the core sampling techniques. Therefore, providing a consistent technique is used, observed seasonal fluctuations in bulk density, total porosity, and air-filled porosity on Brookston clay loam soil are apparently not the result of variations in the core sampling technique.     

Leaching of metals from the A-horizon of a spruce forest soil

The study quantifies the amount of metals (Na, K, Mg, Ca, Al, Fe, Mn, Ni, Cr, V, Cu, Zn, Cd, Pb) leached from the A-horizon of a podzolic spruce forest soil in southern Sweden during 2.5 yr, and offers statistical evidence of environmental conditions of importance to metal release. Considerable losses of Pb, Cr, Ni and V may occur from the A-horizon of forest soils under conditions favoring leaching of organic matter, Fe, and Al, i.e. during periods of comparably high soil temperature and moisture. Metals with a larger fraction present in exchangeable form (Na, Mg, Ca, Zn, Cd) are more susceptible to minor pH changes. An accelerated deposition or internal production of acidic matter therefore will reduce the retention times of these elements particularly.     

A passive sampling method for radiocarbon analysis of soil respiration using molecular sieve

Radiocarbon analysis of soil CO₂ can provide information on the age, source and turnover rate of soil organic C. We developed a new method for passively trapping respired CO₂ on molecular sieve, allowing it to be returned to the laboratory and recovered for C isotope analysis. We tested the method on a soil at a grassland site, and using a synthetic soil created to provide a contrasting isotopic signature. As with other passive sampling techniques, a small amount of fractionation of the ¹³C isotope occurs during sampling, which we have quantified, otherwise the results show that the molecular sieve traps a sufficiently large and representative sample of CO₂ for C isotope analysis. Since ¹⁴C results are routinely corrected for mass-dependent fractionation, our results show that passive sampling of soil respiration using molecular sieve offers a reliable method to collect soil-respired CO₂ for ¹⁴C analysis.     

Analysis of summertime cloud water measurements made in a Southern Appalachian spruce forest

This paper presents an analysis of cloud water measurements made during the summers of 1986 and 1987 at Whitetop Mountain, Virginia (36.639° N, 81.605° W). Analysis of cloud water chemistry, cloud type, and air mass origin are made for each cloud event occurring during one 3 to 4 week measurement ‘intensive’ per year. Regional source/receptor relationships are also investigated. Cloud water concentrations of major ions (i.e., H⁺, SO₄ ^2?, NO₃ ?, and NH₄ ⁺) are consistently higher during orographically formed ‘cap’ cloud events. Differences in cloud liquid water content between cap and frontal cloud events explains most, but not all, of the cloud water ion concentration differences. The remaining difference can be explained by greater rainfall associated with frontal cloud events. Most of the cloud water sulfate measured at Whitetop Mountain is apparently due to nucleation of aerosol sulfate within cloud droplets and not to local in-cloud aqueous phase SO, oxidation. No strong source/ receptor relationships were evident from this analysis. Most 72 hr air trajectories arriving at Whitetop Mountain during the cloud events described in this paper originated in the southeastern United States. Few came from the Ohio River Valley or the northeastern United States.     

Process-specific analysis of nitrite dynamics in a permanent grassland soil by using a Monte Carlo sampling technique

The aim of the present study was to separate and quantify process‐specific gross nitrite (NO₂^?) production in a permanent grassland soil and separate the observed NO₂^? concentration into process‐specific sub‐pools. We re‐analysed data from a laboratory experiment where either the nitrate and/or ammonium ions were labelled with ¹⁵N. The simultaneously occurring N transformations were quantified with a ¹⁵N tracing tool in combination with a Monte Carlo sampling technique which has been extended by a NO₂^? sub‐model. Three pathways of NO₂^? production were identified, that is autotrophic nitrification, denitrification and the oxidation of organic N. The full model contained nine pools and 14 N transformations. This is the first report where such a complex ¹⁵N tracing model has been used and where all parameters have been optimized simultaneously. Our analysis shows that on average 52.4% of the total soil NO₂^? concentration was directly derived from oxidation of organic N. Nitrification and denitrification contributed on average 18.1 and 29.5%, respectively, to the total NO₂^? pool. However, more than 99% of the gross NO₂^? production was related to the NH₄⁺ oxidation, which was rapidly further oxidized to NO₃^?. Our re‐analysis using a Monte Carlo sampling technique resulted in parameter profiles that differed from the original analysis. As the new technique is able to optimize all parameters in one optimization run we regard this technique as superior to the previous one. A process‐based understanding of NO₂^? dynamics in soils has important implications for the understanding of the production of the greenhouse gas nitrous oxide (N₂O), which is tightly linked to NO₂^? turnover.     

The effects of mancozeb and lindane on the soil microfauna of a spruce forest: A field study using a completely randomized block design

Summary The effects of mancozeb (fungicide) and lindane (insecticide) were investigated in active soil ciliates, testaceans, rotifers, and nematodes. The effects were evaluated 1, 7, 15, 40, 65, and 90 days after application of a standard and a high (10x) dose. Individual numbers were estimated with a direct counting method. Mancozeb, even at the high dose, had no pronounced acute or long-term effects on absolute numbers of the taxa investigated. The number of ciliate species, which decreased 1 day after treatment with the normal dose (0.05 <P < 0.1), soon recovered. However, the community structure of ciliate species was still slightly altered after 90 days. Testaceans were not reduced before day 15 at the higher dose or before day 40 at the normal one (0.05 <P < 0.1). A normal dose of lindane caused acute toxicity in ciliates and rotifers (P < 0.05) but the latter soon recovered. The number and community structure of ciliate species were still distinctly altered after 90 days (0.05 <P <0.1), indicating the critical influence of lindane. Testaceans were reduced only after day 15, and nematodes only on day 40 (0.05 <P < 0.1). At the high dose of lindane severe long-term effects occurred in soil moisture, total rotifers (P < 0.05), total nematodes (0.05 <P <0.1), and in the structure of the ciliate community. Generally, there were marked differences in the effect of the normal and the high dose of lindane but not with mancozeb. Ciliates showed very pronounced changes after the pesticide applications, indicating their usefulness for testing biocides under field conditions. Testaceans were more resistant than ciliates.     

The Enchytraeidae of spruce forest plots of different exposure and acid deposition in a German mountain range

Enchytraeidae were studied at spruce forest sites (Harz, Germany) differing in their exposure and soil acidity affected by acid deposition. Total density ranged between 38 000 and 59 000 ind. m^–2 and biomass between 0.5 and 1 g m^–2 d.m. (annual means). Of the seven species recorded, Cognettia sphagnetorum, Marionina clavata, and Achaeta camerani were dominant. The site affected most by acidification had the highest densities and lowest species number. Population dynamics and vertical distributions were affected by climate. Field and laboratory data provide evidence for sexual reproduction in C. sphagnetorum. Substrate preference experiments showed this species to prefer spruce litter from the O_L-Horizon to that from the O_H-Horizon, and spruce litter to beech litter.     

Methane consumption in a frequently nitrogen-fertilized and limed spruce forest soil after clear-cutting

Abstract. The effects of especially frequent nitrogen (N) additions (from 1959 to 1986, totalling 860 kg N ha⁻¹) and liming (in 1958 and 1980, totalling 6000 kg CaCO₃ ha⁻¹) on CH₄ uptake by a boreal forest soil were studied in a stand of Norway spruce. Except for a forested reference plot, the stand was clear-cut in January 1993 and the following year one-half of each clear-cut plot was prepared by mounding. Fluxes of CH₄ were measured with static chambers in the autumn before clear-cutting and during the following four summers. The average CH₄ uptake during 1993–96 in the forested reference plot was 82 μg CH₄ m⁻² h⁻¹(ranging from 10 to 147 units). In the first summer after clear-cutting, the cleared plot showed 42% lower CH₄ uptake rate than the forested reference plot, but thereafter the difference became less pronounced. The short-term decrease in CH₄ consumption after clear-cutting was associated with increases in soil NH₄⁺ and NO₃⁻concentrations. Mounding tended at first to stimulate CH₄ uptake but later to inhibit it. Neither liming nor N-fertilization had significant effects on CH₄ consumption. Our results suggest that over the long term, in N-limited upland boreal forest soils, N addition does not decrease CH₄ uptake by the soil.     

A study on fine-root dynamics in response to nutrient applications in a Norway spruce stand using the minirhizotron technique

Minirhizotrons with high resolution were used to investigate how the fine-root turnover rate is influenced by extra nitrogen input to a Norway spruce stand. The stand was subjected to repeated application of ammonium sulphate (NS) and nitrogen-free fertilizers (V), the latter containing macro and micro nutrients other than nitrogen. Data were collected and analysed during a one-year period, 3–4 years after the start of fertilizer additions. A significant interaction of data x treatment (P < 0.001) in root-length production and mortality was found between treatments. However, the total production in the NS and V treated plots was not significantly higher than in the C plots. The annual net production (production minus mortality) was higher in NS than V plots, while net production in the V plots was lower than in the C plots. The NS and V treatments resulted in a higher total root-length mortality than the C plots during the period of study. Winter root-mortality was higher in the V plots than in the C and NS plots. No root-length mortality occurred from June to August in the V plots, while root-length mortality in the C and NS plots during this period was 56% and 55% of annual root mortality, respectively. The NS application increased the production of white roots while the V treatment decreased the mortality of white roots. The mortality of white roots during August 1991 to August 1992 in the V plots was only 8% of total fine root mortality compared with 30% in the C and 60% in the NS plots. The NS and V applications resulted in a larger root diameter than in the C plots.     

Fluctuations of diptera larvae in soil from a spruce forest in relation to climatic factors

Summary Diptera larvae were extracted by the wash and flotation method according to Healey and Russell-Smith (1970) as modified by Altmüller (1979). The larvae had been kept in alcohol for at least 2 months. After this time their specific gravity changed, and an additional flotation with MgSO₄-water solution of SG = 1.26 g/cm³ was very effective. This new method is described. The working procedure can be reduced to about 50%–70% of the time Altmüller (1979) and Hövemeyer (1984) needed. Many tests have shown that some small sciarid larvae settle out with the needle and humus particles in solution of SG = 1.26 and cannot be found, so that it is necessary to apply a correction factor. Samples taken each August from 1979 to 1984 were extracted and floated off by the methods described. Larvae from seven families of Diptera nematocera and from six families of Diptera brachycera were found. Numbers of sciarid larvae varied between 2500 (1979) and 100/m² (1981), of the cecidomyid larvae between 6700 (1983) and 400/m² (1980) and of the brachyceran larvae between 650 (1979) and 50/m² (1984). The correlation coefficient (= r) of larval population size with temperature and precipitation, respectively, was calculated and hence the coefficient of determination as a percentage (r ² x 100), which represents the proportion of the fluctuations in population size that is accounted for by weather factors. All families were influenced negatively by the temperature and positively by the precipitation in August, i.e., the higher the precipitation and the lower the temperature in August the higher the larval abundance in August. The development of the larvae begins in the previous year, and the influence of monthly climatic factors during the whole period of development was tested. It was shown that: Precipitation is correlated with the abundance of (1) sciarid larvae in June and August of the previous year (positively); (2) brachyceran larvae in June (August) of the previous year and in (February), March, April and August of the same year (positively); and (3) cecidomyid larvae in July of the same year (negatively). Temperature is correlated with the abundance of (1) sciarid larvae in August of the previous year (negatively); (2) brachyceran larvae in August of the previous year (negatively); and (3) cecidomyid larvae in September of the previous year, in January and July of the same year (positively). Monthly data for precipitation and temperature, taken together, showed maximum positive correlations with abundance as follows: (1) for sciarid larvae, with data for August of the previous year; (2) for brachyceran larvae, with data for August of the previous year; (3) for cecidomyid larvae, with data for July of the same year.     

The response of soil microbial biomass and activity of a Norway spruce forest to liming and drought

Long-term effects of liming and short-term effects of an experimentally induced drought on microbial biomass and activity were investigated in samples from the O-layer (Of/Oh) and uppermost mineral soil (0—10 cm) in a spruce forest near Schluchsee (Black Forest, South-West Germany). Seven years after lime application a marked increase of pH values was restricted to the O-layer. The contents of C and N in the O-layer of the limed plot appeared to be lower, whereas in the A-horizon from the limed plot the contents of C and N appeared to be higher than on the control. However, these differences were statistically not significant due to a distinct spatial variability of topsoil conditions. On the limed plots C_mic, N_mic, and P_mic in the O-layer were lower in comparison to the control whereas differences in the A-horizon were negligible. In both sampling depths of the limed plot protease activity was higher while N-mineralization was lower. The other microbial activities studied (basal respiration, catalase activity) followed no consistent pattern after liming. Drought and drought in combination with liming, respectively, had no clear effects on microbial biomass and activity. Only in the A-horizon of the control, there is some evidence for drought stress for microorganisms. The high variability of results from the drought experiment (roof installation) is likely due to the marked spatial variability of top soil properties as well as imperfect and uneven achievement of experimental drought. Nevertheless, our study indicates that long-term effects of liming on microorganisms highly depend on site conditions. Thus, liming operations which currently affect vast areas of forest land should be accompanied by monitoring of soil organisms and their activities to reduce the possibility of a loss in functional diversity of soil organisms.     

Leaching of metals from a spruce forest soil as influenced by experimental acidification

Acidified (H₂SO₄+HNO₃, 3:1) throughfall waters (pH 3.16 and 3.40 as volume weighted means or control (untreated throughfall water, pH 3.72) were applied for 3.5 yr by an automatic irrigation device to lysimeters containing podzolized spruce forest soils of 0–5, 0–15 and 0–35 cm soil depth. The total volume of the leachates was measured together with their pH and total content of DOC, Na, K, Ca, Mg, Fe, Mn, Al, Cu, Zn, Cd and Pb and the initial amounts of metals and H in the soil. The main part of H⁺ added with the throughfall waters was retained within the soil. Concentrations and fluxes of Mg, Ca, Mn, Zn and Cd in the soil were significantly increased by addition of acidified throughfall waters; K was less affected. As a consequence of lowered flux of DOC in the A horizon as acid input increased, Fe, Al, Cu, and Pb fluxes also decreased. The mobility of these metals in the A horizon was shown to be regulated mainly by the formation of watersoluble organic compounds rather than directly by pH variations. Compared to the control, the additional annual loss of Mg from the soil profile in the most acid treatment was c. 10% of the currently exchangeable amount.     

Particle-size distribution of PAH in the air of a remote Norway spruce forest in northern Bavaria

The aim of the present study was to elucidate thedistribution of particulate polycyclic aromatichydrocarbons (PAH) in the air of a remote Norwayspruce (Picea abies (L.) karst.) stand.The study encompassed a total of twenty differentcongeners. Particles in ambient air were alternativelycollected by two different Berner cascade impactors atthe field site in Northern Bavaria over a 14-weeksperiod from the end of April through to the end ofJuly 1994 and subsequently analyzed for their PAHcontent. The concentrations of total suspendedparticulate matter (TSP) ranged from 9–31 μg m^-3,suggesting that the field site is an area with a lowlevel of airborne particles. There was a negativerelationship of total particle concentrations with theamount of canopy precipitation due to particle washout at precipitation events. The distribution of theparticle masses on the different size fractions witha maximum in the 1-μm range is typical for remoteareas and indicates a medium-range transport. Theaerosol-bound PAH load decreased from spring sampleswith 2–4 ng m^-3 to values <1 ng m^-3 in the summersamples. Concurrently, the proportion of low molecularweight congeners in the total PAH load declined.Frequently, the highest PAH concentrations (referringto the air) were found in the 0.1–3 μm sizeseparates (accumulation mode). The results suggestthat apart from PAH input to the soil with litter, dryand wet deposition of aerosol particles is animportant pathway of PAH contamination of acid forestsoils in the Fichtelgebirge mountain range.     

Uptake of Sr from microcline and biotite by ectomycorrhizal fungi in a Norway spruce forest

Ectomycorrhizal (EM) fungi growing in symbiosis with tree seedlings have been found in laboratory experiments to stimulate weathering and the uptake of nutrients from silicate minerals. In the present study, we used the natural abundance of strontium isotopes to confirm that these fungi obtain strontium from biotite and microcline under field conditions. Minerals enriched in radiogenic ⁸⁷Sr were introduced into fungal in-growth mesh bags and placed under a 5-10 cm thick humus layer developed on boulders in a Norway spruce (Picea abies (L.) Karst) forest in south-western Sweden. EM root tips were sampled above the mesh bags and the ⁸⁷Sr/⁸⁶Sr ratio was used to calculate the fraction of Sr in the root tips that originated from the minerals. In the EM root tips sampled above the mesh bags containing the different minerals, 1.5% of the Sr originated from biotite and 6.4% from microcline. The amount of Sr was more than 300 times higher in the mesh bags containing microcline than in those containing biotite, indicating that proportionally more Sr was released from the biotite. This study demonstrates that EM fungi have the potential to take up measurable amounts of nutrients, such as Ca and K, from microcline and biotite in the field.