Dr. Jörg Luster

The link between above- and belowground communities is a key uncertainty in drought and rewetting effects on forest carbon (C) cycle.
In young beech model ecosystems and mature naturally dry pine forest exposed to 15-yr-long irrigation, we performed ¹³C pulse labeling experiments, one during drought and one 2 wk after rewetting, tracing tree assimilates into rhizosphere communities.
The ¹³C pulses applied in tree crowns reached soil microbial communities of the young and mature forests one and 4 d later, respectively. Drought decreased the transfer of labeled assimilates relative to the irrigation treatment. The ¹³C label in phospholipid fatty acids (PLFAs) indicated greater drought reduction of assimilate incorporation by fungi (−85%) than by gram-positive (−43%) and gram-negative bacteria (−58%).
¹³C label incorporation was more strongly reduced for PLFAs (cell membrane) than for microbial cytoplasm extracted by chloroform. This suggests that fresh rhizodeposits are predominantly used for osmoregulation or storage under drought, at the expense of new cell formation. Two weeks after rewetting, ¹³C enrichment in PLFAs was greater in previously dry than in continuously moist soils. Drought and rewetting effects were greater in beech systems than in pine forest.
Belowground C allocation and rhizosphere communities are highly resilient to drought.

Ein natürlich gewachsener und intakter Waldboden ist von unschätzbarem Wert. Er sorgt für sauberes Trinkwasser, schützt vor Hochwasser, ist Lebensraum unzähliger Organismen und bildet die Grundlage für die Holzproduktion. Eine besonders wichtige Rolle spielt der Waldboden als Kohlenstoffspeicher. Wird seine Speicherleistung beeinträchtigt, hat dies negative Auswirkungen auf das Klima. Die Klimafolgen wiederum gefährden die bedeutenden Funktionen des Waldes und seiner Böden. In diesem Forum für Wissen wollen wir (i) die Funktionen von Waldböden und ihre Bedeutung für die Waldökosystemleistungen darstellen, (ii) auf mögliche Beeinträchtigungen der Bodenfunktionen durch Klimafolgen, zum Beispiel Sturmschäden, aufmerksam machen, (iii) Massnahmen und Handlungen aufzeigen, die zur langfristigen Erhaltung und Verbesserung der Bodenfunktionen beitragen können, und (iv) auf zukünftige Trends hinweisen.

A naturally grown and intact forest soil is invaluable. It provides clean drinking water, protects against floods, is the habitat of countless organisms, and is the basis for wood production. Forest soils play a particularly important role as carbon storage, and an impaired storage capacity has a negative impact on the climate. Climate change in turn endangers important functions of the forest and its soils. In this "Forum für Wissen" workshop, we want to (i) present the various functions of forest soils and their significance for forest ecosystem services, (ii) draw attention to possible degradation of soil functions due to climate impacts, e.g. damage caused by storms, (iii) highlight measures and actions that can contribute to the long-term maintenance and improvement of soil functions, and (iv) identify future trends.

Humusauflagen bedecken die Mineralböden in Wäldern. Sie bestehen aus abgestorbenen Pflanzenresten in unterschiedlichen Zersetzungsstadien und erfüllen wichtige Funktionen im Nährstoff- und Wasserkreislauf der Waldökosysteme. Aktuelle Arbeiten zur Phosphor-Ernährung von Buchenwäldern legen nahe, dass mächtige Humusauflagen das Resultat ökosystemarer Anpassung an P-arme Mineralböden sind. Als oberste Schicht des Bodens reagieren Humusauflagen besonders sensitiv auf oberirdische Veränderungen. Dies ist für Stickstoffeinträge bereits gut belegt und könnte auch für Veränderungen gelten, die mit dem Klimawandel zu tun haben. Episodisch auftretende Störungen oder ein kontinuierlicher Temperaturanstieg führen zu einer beschleunigten Mineralisation von Humusauflagen und können Nährstoffungleichgewichte hervorrufen. Das Belassen der Ernterückstände (Äste, Zweige, Rinde) im Bestand sowie die Berücksichtigung des Waldinnenklimas beim Waldmanagement sind daher besonders an nährstoffarmen Standorten geboten.

Organic layers (constituting the forest floor) cover the mineral soils in forests. They consist of plant litter in different stages of decomposition and fulfil important functions in the nutrient and water cycle of forest ecosystems. Current work on phosphorus nutrition in beech forests suggests that thick forest floors with low turnover may be the result of ecosystem adaptation to phosphorus-poor mineral soils and enable tight recycling of phosphorus. As the uppermost layer of the soil, forest floors react particularly sensitively to aboveground disturbances. This has already been well documented for nitrogen inputs, but is also indicated for climate change related disturbance. Forest disturbances or temperature increases cause accelerated mineralisation of the forest floor and could thus lead to nutrient deficiencies in the forests. Leaving the harvest residues (bark, twigs, and branches) in the stand and taking the forest micro climate into account are therefore particularly important options in forest management on nutrient-poor sites.

The potential of river floodplains to emit nitrous oxide (N₂O), a powerful greenhouse gas and ozone-depleting compound, considerably reduces the climate regulation function of these dynamic transition zones between aquatic and terrestrial ecosystems. However, the assessment of N₂O emissions from floodplain soils is challenging, due to the inherently high spatial heterogeneity and the characteristic occurrence of sporadic inundation phases. Such short-term flood events can temporarily alter the conditions for nitrogen (N) transformation processes taking place within distinct microhabitats, which can lead to the local formation of transient hot spots of enhanced N₂O emissions. This situation emphasizes the urgent need to understand how characteristic factors of microhabitat formation in river floodplains control the balance between major microbial N₂O source processes and N₂O reduction to N₂ that determine the magnitude and duration of N₂O emissions. Therefore, the main objective of this thesis project was to systematically assess the relative importance of microhabitat effects related to soil aggregate size, organic matter accumulation, and plant-soil interactions on the microbial N₂O production and consumption processes controlling the spatiotemporal emission patterns of N₂O under changing pore water saturation. To achieve this objective, a mesocosm experiment under controlled climatic conditions, and a study within the framework of a field manipulation experiment were conducted. [...]

The cultivation of Populus spp. on acid soils is difficult mainly due to low nutrient availability, limiting the distribution and use of this marketable tree species. In this paper we report the results of two experiments, in which a granulated highly reactive micronized calcium carbonate (CaCO₃) was tested at increasing levels to improve the effect of NPKS fertilization on poplar growth. Twin field and pot experiments were carried out in 2017 using two different poplar clones, both of which are often used in Italy. In addition to analysing the data from the two experiments separately, common patterns were evaluated using a mixed-effect model with CaCO₃ level and fertilization as fixed effects, and the experiment type as random effect. Growth was assessed in terms of total height, diameter and biomass. Taken together, the results from the two experiments showed that fertilization led to enhanced growth of poplar, but this effect was stronger when soil conditions in terms of pH and exchangeable Ca were at a sufficiently high level. Available nutrient concentrations in the soil and foliar nutrient concentrations in the plant suggested co-limitation of poplar growth by N and Ca. In conclusion, the results of this study on one hand emphasize the importance of adapting the level of CaCO₃ to the given soil conditions, and on the other hand ask for further studies addressing the relative importance of elevated pH and improved Ca nutrition.

Sustainable forest management requires understanding of ecosystem phosphorus (P) cycling. Lang et al. (2017) [Biogeochemistry, https://doi.org/10.1007/s10533-017-0375-0] introduced the concept of P-acquiring vs. P-recycling nutrition strategies for European beech (Fagus sylvatica L.) forests on silicate parent material, and demonstrated a change from P-acquiring to P-recycling nutrition from P-rich to P-poor sites. The present study extends this silicate rock-based assessment to forest sites with soils formed from carbonate bedrock. For all sites, it presents a large set of general soil and bedrock chemistry data. It thoroughly describes the soil P status and generates a comprehensive concept on forest ecosystem P nutrition covering the majority of Central European forest soils. For this purpose, an Ecosystem P Nutrition Index (ENI_P) was developed, which enabled the comparison of forest P nutrition strategies at the carbonate sites in our study among each other and also with those of the silicate sites investigated by Lang et al. (2017). The P status of forest soils on carbonate substrates was characterized by low soil P stocks and a large fraction of organic Ca-bound P (probably largely Ca phytate) during early stages of pedogenesis. Soil P stocks, particularly those in the mineral soil and of inorganic P forms, including Al- and Fe-bound P, became more abundant with progressing pedogenesis and accumulation of carbonate rock dissolution residue. Phosphorus-rich impure, silicate-enriched carbonate bedrock promoted the accumulation of dissolution residue and supported larger soil P stocks, mainly bound to Fe and Al minerals. In carbonate-derived soils, only low P amounts were bioavailable during early stages of pedogenesis, and, similar to P-poor silicate sites, P nutrition of beech forests depended on tight (re)cycling of P bound in forest floor soil organic matter (SOM). In contrast to P-poor silicate sites, where the ecosystem P nutrition strategy is direct biotic recycling of SOM-bound organic P, recycling during early stages of pedogenesis on carbonate substrates also involves the dissolution of stable Ca-P_org precipitates formed from phosphate released during SOM decomposition. In contrast to silicate sites, progressing pedogenesis and accumulation of P-enriched carbonate bedrock dissolution residue at the carbonate sites promote again P-acquiring mechanisms for ecosystem P nutrition.

Foliar phosphorus (P) concentrations in beech trees are decreasing in Europe, potentially leading to reductions in the trees’ growth and vitality. In the course of climate change, drying and rewetting (DRW) cycles in forest soils are expected to intensify. As a consequence, P leakage from the root zone may increase due to temporarily enhanced organic matter mineralization. We addressed the questions whether sites with different soil properties, including P pools, differ in their susceptibility to DRW-induced P leaching, and whether this is affected by the DRW intensity. A greenhouse experiment was conducted on naturally structured soil columns with beech saplings from three sites representing a gradient of soil P availability. Four DRW cycles were conducted by air-drying and irrigating the soils over 4 hours (fast rewetting) or 48 hours (slow rewetting). Leachates below the soil columns were analyzed for total P, and molybdate reactive P (considered as inorganic P). The difference was considered to represent organically bound P. Boosted regression trees were used to examine the effects of DRW and soil characteristics on P leaching. Contrary to a first hypothesis, that P leaching increases upon rewetting with the intensity of the preceding desiccation phase, intense soil drying (to pF 3.5 to 4.5) did not generally increase P leakage compared to moderate drying (to pF 2 to 3). However, we observed increased inorganic P concentrations and decreased organic P concentrations in leachates after drying to matric potentials above pF 4. Also against our expectations, fast rewetting did not lead to higher leakage of P than slow rewetting. However, the results confirmed our third hypothesis that the site poorest in P, where P recycling is mainly limited to the humus layer and the uppermost mineral soil, lost considerably more P during DRW than the other two sites. The results of our experiment with naturally structured soils imply that intensified drying and rewetting cycles, as predicted by climate-change scenarios, may not per se lead to increased P leaching from forest soils. Soil properties such as soil organic carbon content and texture appear to be more important predictors of P losses.

Research on drought impact on tree functioning is focussed primarily on water and carbon (C) dynamics. Changes in nutrient uptake might also affect tree performance under drought and there is a need to explore underlying mechanisms. We investigated effects of drought on (a) in situ nitrogen (N) uptake, accounting for both, N availability to fine roots in soil and actual N uptake, (b) physiological N uptake capacity of roots and (c) the availability of new assimilates to fine roots influencing the N uptake capacity using ¹⁵N and ¹³C labelling. We assessed saplings of six different tree species (Acer pseudoplatanus L., Fagus sylvatica L., Quercus petraea (Mattuschka) Liebl., Abies alba Mill., Picea abies (L.) H.Karst. and Pinus sylvestris L.). Drought resulted in significant reduction of in situ soil N uptake in deciduous trees accompanied by reduced C allocation to roots and by a reduction in root biomass available for N uptake. Although physiological root N uptake capacity was not affected by drought in deciduous saplings, reduced maximum ammonium but not nitrate uptake was observed for A. alba and P. abies. Our results indicate that drought has species-specific effects on N uptake. Even water limitations of only 5 weeks as assessed here can decrease whole-plant inorganic N uptake, independent of whether the physiological N uptake capacity is affected or not.

Predictions on how the increasingly warmer and drier climate and the related stronger fluctuations in soil moisture will change the geographic distribution of beech (Fagus sylvatica L.) require dryingrewetting (DRW) studies in undisturbed soil. Considering the potential effects of DRW on soil physicochemical properties and drying and drought release on plant and microbial physiology, such conditions may affect the bioavailability and uptake of nutrients, but also losses from the soil, and consequently plant productivity and P cycling. Effects may be particularly strong for nutrients with a low solubility and mobility in soils, such as phosphorus (P), when present in low concentrations or when they limit plant and microbial growth. The goal of this study was to elucidate how much organic P can potentially be hydrolysed by the activity of acid phosphatase, and how much 33P is taken up by beech saplings and microbes in naturally structured soils, that were dried and differently rewetted. The effects of DRW were studied in controlled greenhouse experiments, which involved undisturbed soil columns with naturally grown beech saplings from two acid forest sites strongly differing in P supply. The soil from the site Bad Brückenau (BBR) with the higher P supply was a silty clay loam, whereas the soil from the site Unterlüss (LUE) with the lower P supply was a loamy sand with a thick organic surface layer. [...]

Um Vorhersagen treffen zu können, wie sich die geographische Verteilung der Buche (Fagus sylvatica L.) unter wärmeren und trockeneren Klimabedingungen und den damit verbundenen stärkeren Schwankungen im Bodenwassergehalt ändern könnte, bedarf es Austrocknungs- und Wiederbewässerungs-Studien (AWB) in ungestörten Böden. In Anbetracht der möglichen Effekte von AWB auf physikalisch-chemische Bodeneigenschaften und auf die Physiologie von Pflanzen und Boden-Mikroorganismen, können solche Klimaveränderungen starken Einfluss auf die Bioverfügbarkeit und die Aufnahme von Nährstoffen haben. Folglich kann sich AWB auf Pflanzenwachstum und P Kreisläufe auswirken. Besonders stark betroffen sind möglicherweise Nährstoffe mit beschränkter Verfügbarkeit und Mobilität im Boden, wie z.B. Phosphor (P), vor allem, wenn diese in nur geringen Konzentrationen im Boden vorliegen oder das Wachstum von Pflanzen und Mikroorganismen limitieren. Im Rahmen von kontrollierten Gewächshausexperimenten wollten wir anhand ungestörter Bodensäulen, die ausgetrocknet und unterschiedlich wiederbewässert wurden, untersuchen wieviel organischer P durch die Aktivität von saurer Phosphatase potentiell hydrolysiert werden kann, und wieviel P von jungen Buchen und von Mikroorganismen aufgenommen werden kann. Die Bodensäulen wurden gemeinsam mit natürlich gewachsenen jungen Buchen in Wäldern mit unterschiedlicher P-Verfügbarkeit im Boden entnommen. Der Standort Bad Brückenau (BBR) mit einer hohen P-Verfügbarkeit war ein lehmiger Boden, während der Standort Unterlüss (LUE) mit einer niedrigen P-Verfügbarkeit ein sandiger Boden war. Letzterer Standort zeichnet sich vor allem durch einen starken organischen Horizont aus. [...]

Drought alters carbon (C) allocation within trees, thereby impairing tree growth. Recovery of root and leaf functioning and prioritized C supply to sink tissues after drought may compensate for drought-induced reduction of assimilation and growth. It remains unclear if C allocation to sink tissues during and following drought is controlled by altered sink metabolic activities or by the availability of new assimilates. Understanding such mechanisms is required to predict forests’ resilience to a changing climate. We investigated the impact of drought and drought release on C allocation in a 100-y-old Scots pine forest. We applied ¹³CO₂ pulse labeling to naturally dry control and long-term irrigated trees and tracked the fate of the label in above- and belowground C pools and fluxes. Allocation of new assimilates belowground was ca. 53% lower under nonirrigated conditions. A short rainfall event, which led to a temporary increase in the soil water content (SWC) in the topsoil, strongly increased the amounts of C transported belowground in the nonirrigated plots to values comparable to those in the irrigated plots. This switch in allocation patterns was congruent with a tipping point at around 15% SWC in the response of the respiratory activity of soil microbes. These results indicate that the metabolic sink activity in the rhizosphere and its modulation by soil moisture can drive C allocation within adult trees and ecosystems. Even a subtle increase in soil moisture can lead to a rapid recovery of belowground functions that in turn affects the direction of C transport in trees.

Forests dominated by beech (Fagus sylvatica L.) cover large parts of Europe where they occupy a broad ecological niche in terms of soil fertility. This indicates a large potential to adapt to different soil conditions over long time periods. Recent changes in tree mineral nutrition across Europe raise the question to what degree beech can acclimate to changing soil conditions in the short term. In this study, we aimed at assessing the plasticity of root traits and rhizosphere properties of young beech trees from populations that are adapted to either high or low nutrient supply, when growing in soils differing in their fertility. We sampled beech saplings from two forest sites of contrasting nutrient supply, most distinctly in terms of phosphorus. We grew them for 2 years in rhizoboxes in mineral soil either from their own site or from the other site. We assessed the influence of the factors "plant origin" and "current soil" on root traits and rhizosphere properties. Fine root traits related to growth (biomass, length), architecture (branching), and morphology (diameter) responded strongly to the factor “current soil.” Provenance (factor “plant origin”) modified the response. The modifying effect was consistent with an influence of the plant status in those nutrients, which were not in sufficient supply in the soil. An additional genotypic difference in the sensitivity of the beech saplings to different soil nutrient supply could not be excluded. Fine root parameters normalized for length, mass, or volume (root tip density and frequency, specific root length and area, and root tissue density) did not differ among the treatments. Differences in percentage of mycorrhizal root tips and rhizosphere parameters related to phosphorus mobilization potential (pH, abundance of organic acid anions, and phosphatase activity) were small and mainly determined by the “current soil.” Provenance had only a minor modifying effect, possibly due to differences in the ability of the plants to transfer carbon compounds from the shoot to the root and the fungal partner. Our results indicate a high plasticity of young beech trees to adapt their root system to different soil nutrient supply, thereby also taking into account internal nutrient reserves.

Decreasing phosphorus (P) concentrations in leaves of beech (Fagus sylvatica L.) across Europe raise the question about the implications for forest health. Considering the distribution of beech forests on soils encompassing a broad range of nutrient availability, we hypothesized that this tree species exhibits high phenotypic plasticity allowing it to alter mass, and nutrient allocation in response to local nutrient availability. To test this,
we grew two groups of 12–15 year old beech saplings originating from sites with high and low soil P availability for 2 years in mineral soil from their own site and in soil from the other site. After two growing seasons, P concentrations in leaves and stem, as well as mass allocation to leaves and fine roots were affected by both soil and plant origin. By contrast, relative P allocation to leaves and fine roots, as well as P concentrations in
fine roots, were determined almost entirely by the experimental soil. Independent of the P nutritional status defined as average concentration of P in the whole plant, which still clearly reflected the soil conditions at the site of plant origin, relative P allocation to leaves was a particularly good indicator of P availability in the experimental soil. Furthermore, a high plasticity of this plant trait was indicated by a large difference between plants
growing in the two experimental soils. This suggests a strong ability of beech to alter resource allocation in response to specific soil conditions.

Forests dominated by beech (Fagus sylvatica L.) cover a large part of Europe and occur on a wide variety of soils, realizing a broad ecological niche in terms of soil chemical properties including pH, base saturation, and plant-available phosphorus (P) pools in the mineral topsoil. On the other hand, a decrease in foliar P concentrations and a corresponding increase in the nitrogen (N) to P ratio during the last decades all over Europe raised questions about a possible reduction in forest health and productivity due to P limitation. These changes in leaf nutrient status have been attributed to continuing high N deposition and increasing atmospheric carbon dioxide concentrations. Both accelerated tree growth due to high N and carbon (C) input and adverse effects of elevated N on fine root biomass, mycorrhization, and litter mineralization appear to have created a higher need for other nutrients that cannot be met by the supply from the soil. Surprisingly little is known about internal P allocation of beech and its capacity to deal with changing soil P availability in the short-term. Considering the distribution of beech forests on soils encompassing a broad range of nutrient availability, and thus proven ability to adapt to different soil conditions in the long-term, we hypothesized that this tree species exhibits a high phenotypic plasticity allowing it to alter multiple traits in response to local nutrient availability leading to adaptive acclimation and resulting in a phenotype tailored for local soil conditions. [...]

Buchenwälder (Fagus sylvatica L.) bedecken grosse Teile Europas und kommen auf einer Vielzahl von Böden vor, die einerseits eine breite ökologische Nische in Bezug auf bodenchemische Eigenschaften wie pH-Wert, Basensättigung und pflanzenverfügbaren Phosphor (P) im Oberboden bilden. Andererseits haben in Europa zurückgehende P Gehalte in Blättern und der damit einhergehende Anstieg des Stickstoff (N) zu P Verhältnisses während der letzten Jahrzehnten die Frage über einen möglichen Rückgang der Waldgesundheit und der Produktivität aufgrund von P Limitierung aufkommen lassen. Diese Veränderungen im Nährstoffgehalt der Blätter wurden hauptsächlich auf anhaltend hohe N Depositionen und ansteigende atmosphärische CO2 Konzentrationen zurückgeführt. Sowohl beschleunigtes Baumwachstum durch hohe N und Kohlenstoff (C) Einträge als auch negative Effekte von erhöhtem N auf die Feinwurzelbiomasse, die Mykorrhizierung und die Streumineralisierung scheinen einen höheren Bedarf an anderen Nährstoffen ausgelöst zu haben, der nicht durch die Versorgung aus dem Boden gedeckt werden kann. Erstaunlicherweise ist sehr wenig bekannt über interne P Zuteilung in Buchen und deren Kapazität mit veränderter Phosphorverfügbarkeit im Boden auf kurze Sicht zurecht zu kommen. [...]

Soil structure formation is among the most important processes in river floodplains which are strongly influenced by alluvial dynamics. In the context of river restoration projects, a better understanding of soil structure formation in habitats adjacent to the river can help to prevent damages caused by riverbank erosion. Ecosystem engineers such as pioneer herbaceous plants and earthworms likely contribute to soil structure formation even despite less favourable environmental conditions. This study aims to assess the capacity of the herbaceous perennial and native species Phalaris arundinacea and earthworm communities to promote a stable soil structure in alluvial sediments, in particular fresh alluvial deposits, in the short term. Delimited plots were set-up in a restored floodplain adjacent to the Thur River in NE Switzerland and exposed to natural alluvial dynamics for 19 months. Four treatments were replicated in a randomised complete block design: (i) plots with Phalaris arundinacea as only vegetation, (ii) plots with all vegetation constantly removed, (iii) and (iv) the earthworm community reduced by mustard treatment, otherwise as (i) and (ii), respectively. Soil structure formation was analysed at the end of the experiment using different indicators: aggregate stability, field-saturated hydraulic conductivity and the porosity calculated from X-ray CT reconstructions of freeze cores. Phalaris arundinacea was capable of improving the porosity and aggregate stability of both alluvial sediments present at the beginning of the experiment but also of sediments freshly deposited during the observation period. The latter indicates a structuring effect within only one vegetation period. Earthworm abundance was as a whole very low, most likely due to the large proportion of sand. There was a small earthworm effect on soil structure formation, and only in combination with Phalaris.arundinacea. Our findings highlight the ability of Phalaris arundinacea in efficiently structuring sandy alluvial sediments in the short term even under strong alluvial dynamics. Phalaris arundinacea can therefore play a key role in the early stage of river restoration projects. Thus, facilitating the colonisation by such native pioneer herbaceous plants is a suitable step to improve the success of river restoration projects.

The soil water content affects rates of oxygen diffusion and redox potentials (E_H). When water‐saturated soils become aerated, a switch from reducing to oxidizing conditions occurs. However, limited information is available at which air‐filled pore volume ε this shift happens. To obtain values of ε, undisturbed soil cores were taken from a Fluvisol and a Gleysol that differed in structure and clay content. Experiments on submergence and drying following a new experimental design were performed in the laboratory. After submergence, the cores were sealed with a glass hood to exclude oxygen and to achieve reducing conditions (E_H < –100 mV). We then aerated the sample by removal of glass plugs in the hood and consecutively measured E_H by platinum (Pt) electrodes and ε by matric potential readings on an hourly basis. From the drying curve we determined two characteristic values: (i) ε_{Pt reaction} indicates the air‐filled pore volume at which a response of the Pt‐electrode from contact with oxygen occurs (i.e. E_H increase > 5 mV hour^–1) and (ii) ε_{Pt aeration} indicates when oxidizing soil conditions are present (i.e. E_H > 300 mV at pH 7). The Fluvisol was characterized by an ε_{Pt reaction} value of 0.036±0.006 cm³ cm^–3 and an ε_Pt aeration value of 0.047±0.005, whereas for the Gleysol these values were 0.048±0.008 and 0.085±0.007 cm³ cm^–3, respectively. We aimed to obtain such characteristic values for different soils to estimate the aeration status of a soil when ε is known, but E_H measurements are unavailable.