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  • 1
    Language: English
    In: Forest Ecology and Management, 01 January 2016, Vol.359, pp.74-82
    Description: Harvesting and logging with heavy forest machines cause soil damage that may restrict forest soil functions. Although the recovery ability of compacted forest soils depends on the soil properties, little is known about the long-term structure recovery of different soils following forest operations. The aim of our study was to evaluate the soil structure recovery of three different soil types. Therefore, we applied a space-for-time substitution approach (10, 20, 30 and 40 years after the last machine impact) to study selected sites in Lower Saxony, Germany, using the following as proxies: bulk density, carbon dioxide (CO ) concentration in soil gas, and the relative apparent gas diffusion coefficient ( / ). At sites with high biological activity and high clay content (Cambisols on limestone), recovery occurred 10–20 years after last traffic impact. At these sites, 10 years after the last traffic impact, gas diffusivity at the wheel track was half of the gas diffusivity of the undisturbed soil, and soil gas CO concentrations were significantly higher at the wheel tracks. At the 20-, 30-, and 40-year-old skid trails, there were no significant differences between the untrafficked reference and the soil frequented by vehicles. Regardless of the kind of traffic impact (wheel track, mid line, side strip or undisturbed reference soil), all investigated parameters indicated that soil structure becomes more favourable with increasing time since the last forest interference. In contrast, loamy sandy soils (Podzols on glacial drift and sand) showed low recovery ability. Forty years after the last machine impact, gas diffusivity was still significantly reduced at the wheel track. Cambisols at loess-covered sandstone showed neither strong impact of forest traffic on soil structure nor changes in soil structure 20–40 years after last traffic impact. In general, bulk density turned out not to be a sufficient proxy for soil structure recovery.
    Keywords: Soil Gas Diffusivity ; Soil Carbon Dioxide ; Soil Compaction ; Soil Structure Recovery ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 2
    Language: English
    In: Urban Forestry & Urban Greening, 2012, Vol.11(3), pp.329-338
    Description: Soil aeration is an important factor in tree growth. Oxygen must be taken from the atmosphere for root respiration, and carbon dioxide must be discharged to the atmosphere. Because the pore space of the soil could be considered the “dead end” of the free atmosphere, topsoil gas diffusivity is particularly important for soil aeration. Due to diverse land uses, several soil cover types alternate on a small scale at urban sites, competing with the natural function of soil as the living space for roots. During Documenta 7 in 1982, the artist Joseph Beuys initiated the spectacular landscape art project “7000 Oaks”. Seven thousand trees of approximately the same age were planted over the whole city of Kassel, Germany, offering best possible conditions for investigating the influence of specific site factors on root and tree development. At 8 different sites featuring 36 Beuys-oaks and 15 Beuys-planes, topsoil gas diffusivity, soil CO concentration and soil respiration of different soil cover types were measured and correlated with fine root density and tree growth. Topsoil gas diffusivity and soil respiration depend on soil cover type. The lowest gas diffusivities and respiration rates were found at sealed sites, and the highest values were measured at vegetated sites such as lawn or flower beds. Soil gas diffusivity primarily controls soil respiration. Soil CO concentration is not strictly linked to the coverage type and does not show a strictly directed dependence on top soil gas diffusivity and soil respiration. Tree root density and height as well as diameter at breast height (1.3 m) of the oaks were decisively shaped by the gas diffusivity of the soil cover, whereas the investigated planes were not affected by soil aeration deficiencies. The vitality of urban trees can be controlled by the design of the tree site and the choice of the species.
    Keywords: Gas Diffusion Coefficient ; Oak ; Plane ; Soil Co2 Concentration ; Soil Cover ; Soil Respiration ; Agriculture ; Architecture
    ISSN: 1618-8667
    E-ISSN: 1610-8167
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  • 3
    Language: English
    In: Soil Science Society of America Journal, 2012, Vol.76(6), pp.1992-1998
    Description: A commonly accepted method to measure the in situ gas diffusivity of topsoil is based on the diffusion of a test gas from an open-bottomed chamber that is inserted a few centimeters into the soil. The aim of this study is to develop an easy-to-use approach to determine the gas diffusivity of topsoil at sites where the chamber cannot be inserted into the soil. In the existing method, the diffusion of gas into the soil is a quasi-one-dimensional problem with an analytical solution for gas concentration in the chamber as a function of time t. This one-dimensionality is no longer given in the case of a chamber placed on top of the soil. In the newly suggested method, simulated time series of gas concentrations in a chamber inserted into the soil (Case 1) were compared to those for a chamber placed on top of the soil (Case 2), with equal gas diffusion coefficients for the soil, D-s. We determined a relationship that can be used to convert the chamber concentration for a given D-s at each t in Case 2 to Case 1. The values of D-s can be found iteratively. The method was validated using D-s values different from those used to calculate the function parameters. Practical field measurements of gas diffusivity were also conducted, which show that, on average, both methods yield the same results for an individual site.
    Keywords: Natural Sciences ; Physical Sciences ; Naturvetenskap ; Fysik
    ISSN: 0361-5995
    E-ISSN: 14350661
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  • 4
    Language: English
    In: Geoderma, 01 July 2017, Vol.297, pp.61-69
    Description: The use of heavy machinery for timber harvesting causes soil damage, which may restrict forest soil functions over decades. Numerous studies have demonstrated the negative impact of soil compaction on soil physical properties, but the effects of compaction of forest soils on soil chemical and biological processes like the phosphorus availability are largely unknown. Aim of our study was to analyze the effect of skidding activity on the P dynamics on skid trails and the soil recovery ability after skidding. Furthermore, we wanted to assess if acid phosphatase activity is an appropriate indicator of soil structure damage after compaction. We investigated the phosphorus availability, acid phosphatase activity, TOC, pH value, and fine root density of soil samples from skid trails and from control plots without any skidding effect. We conducted our studies at three sites (Göttingen: Cambisols on limestone, Heide: Podzol on glacial drift and sand, and Solling: Cambisols at loess-covered sandstone) in Lower Saxony, Germany 10 to 40 years after last traffic impact in a space-for-time substitution. We observed mainly higher P concentrations and higher pH values at the wheel tracks than in the control. TOC was predominantly higher at the wheel tracks, but lower TOC at the wheel tracks was also found. In the acidic loams of the Solling region, the amount of mineralized phosphate was much higher in the tracks compared to the control areas 10 to 30 years after last traffic impact. This suggests a decoupling of P mineralization from P uptake in the wheel tracks for several decades. Furthermore, higher as well as lower phosphatase activity at the wheel tracks compared to the untrafficked control was found, but higher phosphatase activities at the wheel tracks were predominant. Acid phosphatase activity was strongly correlated with TOC, but did not correlate with the time since last traffic impact and the gas diffusivity of the soil. Therefore, our results did not confirm that acid phosphatase activity is an appropriate soil biological indicator of soil compaction and structural recovery.
    Keywords: Acid Phosphatase Activity ; P Availability ; Soil Compaction ; Soil Structure Recovery ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 5
    Language: English
    In: Forest Ecology and Management, 2002, Vol.159(1), pp.15-25
    Description: In middle-European silviculture, oak species are largely used for restoration of wind-thrown spruce stands on dense or badly aerated soils. However, vitality of mature oak stands have decreased in the last decade. Symptoms of fine root degeneration as well as soil structure deficiencies in the upper layer have been observed. This study tested the working hypothesis that deficiencies in soil gas permeability reduce fine root formation and thereby reduce stress tolerance of trees. Topsoil gas diffusivity, root density and oak vitality were assessed for 36 oak stands with pedunculate oak (Quercus robur L.) and sessile oak (Quercus petraea [Matt.] Liebl.). The relationship between topsoil gas diffusivity, soil respiration and soil CO sub(2) concentration were also investigated. Evidence that root density decreases significantly with decreasing soil gas permeability was found, which is representative for oak stands at southwest Germany. Heavily damaged oak stands have been found only at sites suffering from soil aeration deficiencies. Although, we observed decreased soil respiration in compacted soils, CO sub(2) concentration in soil was up to three times higher on these sites. High soil CO sub(2) concentrations indicate insufficient soil aeration rather than high biological activity. Insufficient soil aeration is apparently an important factor causing oak decline. It cannot be, therefore, concluded from the oak's ability to open up dense subsoils that they can be used for the restoration of stands with compacted topsoils.
    Keywords: Oak Decline ; Soil Aeration ; Fine Roots ; Gas-Diffusion Coefficient ; Soil Air Carbon Dioxide ; Soil Respiration ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 6
    Language: English
    In: Journal of Plant Nutrition and Soil Science, June 2001, Vol.164(3), pp.253-258
    Description: The McIntyre and Phillip method yields the product of a gas‐diffusion coefficient (D) and the gas‐filled proportion of soil volume ε. Until now, ε had to be measured independently from soil cores in order to obtain D. To avoid soil sampling, we broke up chamber measurement results by means of an empirical relationship D= f(ε). In contrast to an exclusive use of such an empirical relationship, this approach is advantageous in that the site‐specific information concerning pore continuity is integrated into the result. Another modification involves the use of a non‐linear regression technique, which fits the unknown parameters of the mechanistic dilution function of the tracer gas to the measured values. In this way, the independent measurement of chamber clearance with a ruler could be replaced with an estimation based on the dilution function. We could then show, by means of a Monte Carlo simulation, that the exponential parameter of the dilution function contributes to the highest error of the diffusion coefficient estimation from the 6 input parameters. We then compared the results of the following methods at 6 sites. The methods included: (a) the approach described above, (b) the laboratory measurement on soil cores, and (c) the original McIntyre and Philip method. This method is a combination of in‐situ chamber measurement and laboratory measurement of the air‐filled soil fraction. We did not detect any significant differences in the means of our method (a) in any of the aforementioned cases, as well as in the laboratory measurement (b). Deviations between individual measurements could be attributed to differences in spatial integration. These deviations are a result of scale‐dependent spatial heterogeneity and thereby provide site‐specific information on soil structure. Ein modifizierter McIntyre‐and‐Phillip‐Ansatz zur in‐situ Bestimmung der Gasdiffusivität von Oberböden Die Methode von McIntyre und Phillip zur Bestimmung von Bodengasdiffusionskoeffizienten in‐situ liefert als eigentliches Messergebnis das Produkt aus Gasdiffusionskoeffizient (D) und luftgefülltem Bodenanteil (ε). Um den D zu erhalten, musste ε bisher an zusätzlich entnommenen Stechzylindern bestimmt werden. Wir extrahieren aus dem Ergebnis der Kammermessung den Diffusionskoeffizienten mit Hilfe eines empirischen Zusammenhangs D = f(ε). Da auch Informationen über die standortspezifische Porenkontinuität mit in die Schätzung des Diffusionskoeffizienten einfließen, ist dieses Vorgehen der rein empirischen Abschätzung von D aus ε überlegen. Eine weitere Modifikation liegt in der Verwendung eines nicht‐linearen Regressionsverfahrens zur Anpassung der unbekannten Parameter der mechanistischen Verdünnungsfunktion an die Messwerte. Damit konnte die bei rauen Waldbodenoberflächen problematische Bestimmung des lichten Kammervolumens durch Längenmessung überflüssig gemacht werden. Mit einer Monte‐Carlo‐Simulation konnten wir unter der Annahme normalverteilter Fehler zeigen, dass von den 6 Eingangsparametern der Steigungsparameter der Verdünnungskurve des Tracer‐Gases die größte Streuung der Ergebnisse bewirkt. Zur Prüfung der Methode wurden an 6 Waldstandorten verglichen: (a) der oben beschriebene Ansatz, (b) die Labormessung an Stechzylindern und (c) die ursprüngliche Methode, bei der die Kammermessung mit der Stechzylinderprobe zur Luftvolumenbestimmung kombiniert wird. In keinem Fall konnten wir signifikante Unterschiede im Mittelwert zwischen der von uns entwickelten Methode a) und der Labormessung b) finden. Ursache der zum Teil erheblichen Abweichungen der Einzelwerte ist wahrscheinlich die unterschiedliche räumliche Integration. Damit sind sie Ausdruck der skalenabhängigen räumlichen Heterogenität der Böden und enthalten somit standortspezifische Strukturinformationen.
    Keywords: Gas Diffusion Coefficient ; In‐Situ Measurement ; Closed Chamber ; Volume Estimation ; Non‐Linear Regression ; Analytical Solution
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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