J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 224 - 235, doi: .
Scientific Paper, English

Igor Bogunovic, Paulo Pereira, Marija Galic, Aleksandra Percin, Ivica Kisic, Vilim Filipovic, Lana Filipovic, Sun Geng, Xiaoyan Tang, Qinli Xiong, Yanbao Lei, Kristina Kljak, Sebastiano Trevisani: Linking tillage practices to soil health, crop productivity, and erosion control in maize – wheat rotation

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• The suitability of conservation tillage in maize–wheat interrow farming in a young plum orchard in Croatia to control runoff, soil, and element loss under natural rainfall was evaluated. Paired runoff plots (20 m2 size) comparing conventional (ploughing and discing) and conservation (chisel and harrow) tillage were implemented in triplicate across Stagnosols (11° slope). Soil physical (bulk density, penetration resistance, mean weight diameter, water stable aggregates) and chemical properties (carbon, nitrogen, phosphorous, potassium and copper) were assessed alongside event-based overland flow formation monitoring. After two years, conservation tillage maintained or improved soil structure, with significantly higher aggregate stability and soil carbon at 0–10 cm depth. Moreover, no clear increase in compaction was documented during the shift to conservation tillage. Conservation tillage exhibited a clear and significant mitigation effect on surface flows of water, sediment, and chemical elements. Sediment concentration decreased from 8.95 to 3.11 g L–1, runoff was 40.5% lower, and cumulative soil loss declined from 8.57 to 2.97 t ha–1 over the two years. Importantly, reduced sediment export translated into markedly lower off-site losses. Conventional tillage increased losses of phosphorus (~3.4×), potassium (~3.2×), copper (~2.6×) and nitrogen (~1.7×) relative to conservation tillage. Overall, non-inversion loosening in orchard inter-rows proved an effective conservation practice for reducing runoff, soil erosion, and chemical export under natural rainfall, supporting on-site soil health and reducing off-site pollution.
  
  KEY WORDS: Agroforestry systems; Cereal cropping systems; Conservation agriculture; Soil degradation; Sustainable agriculture.
  
  Address:
  - Igor Bogunovic, University of Zagreb, Faculty of Agriculture, Svetosimunska 25, 10000, Zagreb, Croatia. (Corresponding author. Tel.: Fax.: Email: ibogunovic@agr.hr)
  - Paulo Pereira, Environmental Management Laboratory, Mykolas Romeris University, Lithuania. Research Institute for Analytical Instrumentation, INCDO INOE, Cluj-Napoca, Romania
  - Marija Galic, University of Zagreb, Faculty of Agriculture, Svetosimunska 25, 10000, Zagreb, Croatia.
  - Aleksandra Percin, University of Zagreb, Faculty of Agriculture, Svetosimunska 25, 10000, Zagreb, Croatia.
  - Ivica Kisic, University of Zagreb, Faculty of Agriculture, Svetosimunska 25, 10000, Zagreb, Croatia.
  - Vilim Filipovic, School of Agriculture and Food Sustainability, The University of Queensland, Australia.
  - Lana Filipovic, School of Agriculture and Food Sustainability, The University of Queensland, Australia.
  - Sun Geng, China-Croatia “Belt and Road” Joint Laboratory on Biodiversity and Ecosystem Services, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610213, China.
  - Xiaoyan Tang, College of Resource, Sichuan Agricultural University, China.
  - Qinli Xiong, China-Croatia “Belt and Road” Joint Laboratory on Biodiversity and Ecosystem Services, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610213, China.
  - Yanbao Lei, China-Croatia “Belt and Road” Joint Laboratory on Biodiversity and Ecosystem Services, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610213, China.
  - Kristina Kljak, University of Zagreb, Faculty of Agriculture, Svetosimunska 25, 10000, Zagreb, Croatia.
  - Sebastiano Trevisani, University IUAV of Venice, Italy.

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 236 - 247, doi: .
Scientific Paper, English

Misagh Parhizkar, Safoora Asadi Kapourchal, Masoumeh Izadpanah Nashroudkoli, Manuel Esteban Lucas-Borja, Demetrio Antonio Zema: Eco-engineered rice-husk nanosilica enhances soil structural stability and re-duces detachment capacity in paddy fields

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• Previous studies have shown that silica nanomaterials produced from rice residues, such as husk, can influence several soil properties. However, their effects on soil detachment capacity and structural characteristics in rice paddy fields remain poorly quantified. This study evaluated the effects of nanosilica derived from rice husk on wet aggregate stability, plasticity index, and detachment capacity in paddy soils of Northern Iran under different flow discharges simulated in a hydraulic flume. The nanosilica used in this study was produced by acid extraction followed by controlled heating, and was incorporated into field plots at a 2% amendment level. Results showed that wet aggregate stability and plasticity index significantly increased by 32% and 27%, respectively, in the nanosilica-treated soils compared with the untreated control. Conversely, the average soil detachment capacity decreased by 49%, also in this case significantly. Multivariate analysis indicated strong interrelations among the measured properties and distinctly separated the amended soils from the control group. Linear regressions between detachment capacity and shear stress or stream power showed that nanosilica reduced soil erodibility and increased the threshold resistance to particle detachment under increasing flow power. Overall, the findings demonstrate that rice-husk-derived nanosilica enhances aggregate cohesion and substantially reduces soil vulnerability to concentrated flow erosion in paddy systems.
  
  KEY WORDS: Soil erosion; Wet aggregate stability; Soil plasticity index; Hydraulic forces; Rice husk nanosilica; Paddy soil.
  
  Address:
  - Misagh Parhizkar, Rice Research Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Rasht 4199613475, Iran.
  - Safoora Asadi Kapourchal, Faculty of Agricultural Sciences, University of Guilan, Rasht 4199613776, Iran.
  - Masoumeh Izadpanah Nashroudkoli, Faculty of Agricultural Sciences, University of Guilan, Rasht 4199613776, Iran.
  - Manuel Esteban Lucas-Borja, Department of Agroforestry Technology, Science and Genetics, School of Advanced Agricultural and Forestry Engineering, Campus Universitario s/n, Castilla La Mancha University, E-02071 Albacete, Spain.
  - Demetrio Antonio Zema, AGRARIA Department, Mediterranean University of Reggio Calabria, Loc. Feo di Vito, I-89122, Reggio Calabria, Italy. (Corresponding author. Tel.: Fax.: Email: dzema@unirc.it)

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 248 - 260, doi: .
Scientific Paper, English

Misagh Parhizkar, Manuel Esteban Lucas-Borja, Demetrio Antonio Zema: Treatment of soil with nanosilica particles derived from rice husk: influence of substrate ageing on soil resistance to detachment

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• No studies have explored how much ageing of rice husk, used as substrate for nanosilica production, alters apparent particle size distribution in this substrate, and therefore modifies nanosilica-soil interactions. To fill this gap, this study has investigated the effects of nanosilica derived from fresh and aged rice husk on soil physical properties and particle detachment (Dc) in paddy soils through flume experiments on samples collected in Northern Iran. Nanosilica obtained from aged husk showed an increase in mean apparent particle size by 96% compared to the soil amendment derived from fresh residues. Soil treated with fresh husk nanosilica exhibited significantly higher (+106%) water-stable aggregates and lower (–7.4%) bulk density compared to the control, while the differences from aged husk treatments were +86 % and –6.3%, also in this case significant. Flume experiments revealed a significant reduction (–21%) in Dc following application of nanosilica from fresh rice husk, while no effect was found for the soil amendment derived from the aged biomass. Compared to the control, Dc decreased by 8.1% with aged husk and by approximately 21% with fresh husk. Dc can be accurately estimated by hydraulic predictors (shear stress, stream power, and unit stream power) using a shifted power function (R² = 0.80–0.96). These models show that, across treatments, the effective hydraulic threshold parameter generally increases from control to amended soils, indicating enhanced resistance to detachment initiation.
  
  KEY WORDS: Soil erosion; Soil structural stability; Agricultural residues; Biomass transformation; Soil resilience.
  
  Address:
  - Misagh Parhizkar, Rice Research Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran.
  - Manuel Esteban Lucas-Borja, Department of Agroforestry Technology and Science and Genetics, School of Advanced Agricultural Engineering, Castilla La Mancha University, Campus Universitario s/n, E-02071 Albacete, Spain.
  - Demetrio Antonio Zema, Department AGRARIA, Mediterranean University of Reggio Calabria, Loc. Feo di Vito, I-89122, Reggio Calabria, Italy. (Corresponding author. Tel.: Fax.: Email: dzema@unirc.it)

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 261 - 270, doi: .
Scientific Paper, English

Khedija Zhioua, Giovanni Russo, Vincenzo Alagna, Dario Autovino, Cristina Bondi, Massimo Iovino, Vincenzo Bagarello: Near-saturated hydraulic conductivity of a sandy-loam soil a few months after incorporating compost or zeolite

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• Little is known about compost (C) and zeolite (Z) effects on hydrodynamic properties of near-saturated coarse-textured soils. These effects were tested for a sandy-loam soil by a mini-disk infiltrometer at three pressure heads (h0 = -6, -3 and -1 cm) and a wide range of amendment percentages, pa (0-40%). Soil hydraulic conductivity, K-6, K-3 and K-1, depending on h0, was determined 3.5 and 8.0 months after the treatment with C and 5.0 and 10.5 months after that with Z. With the C, more amendment determined smaller K-6 (by 1.7-3.0 times), stable K-3 and larger K-1 (3.4-4.4 times) values on both sampling dates. With the Z, the most frequent result was that the soil hydrodynamic parameters did not change with pa. Time effects were more appreciable with the C (means for the two sampling dates differing by 2.1-3.8 times, depending on h0) than the Z (means differing by 1.1-1.7 times). The soil treated with Z was more permeable than that treated with C in the first sampling date (percentage differences, Δ, between corresponding means = 38% - 103%, depending on h0) but not in the second date (Δ values varying from -61% to 4%). In the first year after the treatment, near-saturated soil hydrodynamic behaviour can change appreciably following C addition but the same effect is not expected for the Z. Future investigations should include independent determination of soil pore and particle size distributions.
  
  KEY WORDS: Organic soil amendment; Mineral soil amendment; Coarse-textured soils; Near-saturated soil; Hydrodynamic parameters; Mini-Disk Infiltrometer.
  
  Address:
  - Khedija Zhioua, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128 Palermo, Italy.
  - Giovanni Russo, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128 Palermo, Italy.
  - Vincenzo Alagna, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128 Palermo, Italy.
  - Dario Autovino, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128 Palermo, Italy. (Corresponding author. Tel.: Fax.: Email: dario.autovino@unipa.it)
  - Cristina Bondi, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128 Palermo, Italy.
  - Massimo Iovino, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128 Palermo, Italy.
  - Vincenzo Bagarello, Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, 90128 Palermo, Italy.

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 271 - 279, doi: .
Scientific Paper, English

Jan Frouz, Jiří Kučera, Lukáš Jačka, Martin Šanda, Jimmy C. Oppong, Šárka Řehořková, Martin Bartuška, Olga Vindušková: Relationship between tree transpiration and soil properties: Do trees with higher water demand promote formation of soils with higher water retention?

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• Soil water availability influence plant growth, vegetation, particularly trees, can in turn substantially alter soil properties affecting soil water availability. This study investigates whether tree species with higher transpiration rates promote the development of soils with a higher water-holding capacity using common garden experiment in post-mining heap in northwest Czechia, where several tree species were planted directly into bare overburden. We focused on three monocultures of alder (Alnus glutinosa), oak (Quercus robur), and spruce (Picea omorica). Tree sap flow was measured and used to estimate transpiration at both individual and stand levels. At the same time, soil moisture and water-holding capacity were assessed in each stand. Alder and oak showed similarly high transpiration rates, significantly exceeding those of spruce. The alder stand exhibited the highest average annual soil moisture as well as the highest moisture during the vegetation and dormant season, significantly differing from oak and spruce, while oak soils had a significantly higher moisture than spruce. Water-holding capacity was the highest in oak soils, significantly exceeding that of alder and spruce. These results support the hypothesis that tree species with a higher water demand foster the development of soils with an enhanced water retention capacity.
  
  KEY WORDS: Soil formation; Evapotranspiration; Niche construction; Soil water retention.
  
  Address:
  - Jan Frouz, Institute for Environmental Studies, Faculty of Science & Charles University Environmental Centre, Charles University, Benátská 2, 128 01 Prague 2, Czech Republic. Biology Centre CAS, Na Sádkách 7, 370 05 České Budějovice, Czech Republic. (Corresponding author. Tel.: Fax.: Email: jan.frouz@natur.cuni.cz)
  - Jiří Kučera, Environmental Measuring Systems, s.r.o., Kociánka 85/39, 612 00 Brno, Czech Republic.
  - Lukáš Jačka, Department of Water Resources and Environmental Modeling, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 00 Prague, Czech Republic.
  - Martin Šanda, Czech Technical University in Prague, Thákurova 7, 160 00 Prague 6, Czech Republic.
  - Jimmy C. Oppong, Institute for Environmental Studies, Faculty of Science & Charles University Environmental Centre, Charles University, Benátská 2, 128 01 Prague 2, Czech Republic.
  - Šárka Řehořková, Environmental Measuring Systems, s.r.o., Kociánka 85/39, 612 00 Brno, Czech Republic. Global Change Research Institute CAS, Bělidla 986/4a, 603 00 Brno, Czech Republic. Section of Experimental Plant Biology, Faculty of Science, Masaryk University, Žerotínovo nám. 617/9, 601 77 Brno, Czech Republic.
  - Martin Bartuška, Institute for Environmental Studies, Faculty of Science & Charles University Environmental Centre, Charles University, Benátská 2, 128 01 Prague 2, Czech Republic. Biology Centre CAS, Na Sádkách 7, 370 05 České Budějovice, Czech Republic.
  - Olga Vindušková, Institute for Environmental Studies, Faculty of Science & Charles University Environmental Centre, Charles University, Benátská 2, 128 01 Prague 2, Czech Republic.

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 280 - 288, doi: .
Scientific Paper, English

D.A.L. Leelamanie, H.I.G.S. Piyaruwan: Response of severity and persistence of water repellency to thermal heating parameters in eucalyptus and pine forest soils in Sri Lanka

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• Soil water repellency (SWR) relates to plant species such as conifers and Eucalyptus with high amounts of hydrophobic substances such as resins, waxes, and other oily substances, and are highly vulnerable to wildfires. The heat generated through fire can influence SWR, although the changes can deviate based on soil, climatic, and environmental conditions. This study aims to examine the impact of heating temperature and duration of exposure to heat on the severity and persistence of SWR in eucalyptus and pine forest soils in Sri Lankan highlands. Soils collected from three depths (0–5, 5–10, 10–15 cm) were air dried, passed through a 2 mm sieve, and exposed to six heating temperatures (50, 70, 100, 150, 200, 250°C) and five durations of exposure (20, 40, 60, 90, 120 min). SWR was determined using water drop penetration time (WDPT) and soil-water contact angle. Both eucalyptus and pine soils showed water repellent conditions at the field and at air-dried conditions. Both soils reached completely wettable level (WDPT < 5 s) with very low contact angles when exposed to 200–250°C for 90–120 min, except for the contact angle of the eucalyptus 0–5 cm layer that decreased to a minimum of 40°. SWR showed fluctuations with increasing temperature between 28 and 150°C at all durations of exposure. SWR showed significant positive linear correlation with soil organic matter (SOM) content, of which the strength was moderate (R2 = 0.64 and 0.50, respectively, for eucalyptus and pine), indicating that the heat-induced change in SWR was not strongly dependent on SOM content. Contrasting transitions in SOM due to removal via various processes and structural and molecular rearrangements might explain fluctuations of SWR at lower temperatures (28–150°C). The findings would be useful for understanding the impacts of various heating dynamics that might occur during forest fires. Further research considering the other important factors, such as molecular-level variations in organic substances as well as mineralogical and climatic aspects, would be important for a better understanding of hydrological responses on burnt forest floors.
  
  KEY WORDS: Heating duration; Heating temperature; Soil organic matter; Soil water repellency.
  
  Address:
  - D.A.L. Leelamanie, Department of Soil Science, Faculty of Agriculture, University of Ruhuna, Mapalana, Kamburupitiya 81100, Sri Lanka. (Corresponding author. Tel.: Fax.: Email: leelamanie@soil.ruh.ac.lk)
  - H.I.G.S. Piyaruwan, Department of Soil Science, Faculty of Agriculture, University of Ruhuna, Mapalana, Kamburupitiya 81100, Sri Lanka.

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 289 - 303, doi: .
Scientific Paper, English

Jaroslav Vido, Paulína Nalevanková, Martin Jančo, Daniel Kurjak, Jozef Zverko, Jana Kurjaková, Lenka Malovcová, Jana Škvareninová, Jaroslav Škvarenina: Deadwood-dominated forests buffer microclimate in exposed mountain areas

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• Microclimatic buffering is a key process that determines the regeneration potential and ecosystem stability in disturbed mountain spruce forests. Retention of standing and downed deadwood alters the balance of radiation, temperature, and humidity near the surface; however, quantitative evidence from exposed slopes in the Carpathians has been scarce. We therefore compared intact forest, deadwood-dominated forest, and open area on steep south-eastern slopes of the Western Tatras (Slovakia) using continuous measurements from 2021 to 2025. Micrometeorological stations recorded global solar radiation, air and soil temperature, and humidity at multiple heights and depths; vapour pressure deficit (VPD) was calculated at 5 cm above ground. Differences among sites were assessed using non-parametric tests. Open areas received the highest radiation loads, resulting in extreme warming of the air near the ground (up to 34 °C at 5 cm) and intense soil heating (absolute maximum of 49 °C at –2 cm). Intact forest reduced incoming radiation and maintained the most stable conditions. Deadwood-dominated stands represented an intermediate type but repeatedly buffered extremes: summer soil maxima remained below 26 °C, and air temperatures near the ground were several degrees cooler than in the open area. In winter, snow cover largely equalised conditions, while during snow-free episodes intact forest showed stronger nocturnal cooling, whereas deadwood stands preserved milder soil minima. VPD patterns followed the same gradient, with the shortest daily duration above the threshold of 1.5 kPa in intact forest, the longest in open area, and intermediate values in deadwood stands. Overall, deadwood-dominated forest approximates, and under certain circumstances even exceeds, the buffering capacity of intact spruce stands. We conclude that retention of deadwood-dominated forests mitigates heat and drought stress, reduces thermal extremes, and provides a low-cost, ecologically grounded adaptation strategy for mountain forest management in the context of climate change.
  
  KEY WORDS: Climate change; Natural regeneration; Vapour pressure deficit; Soil temperature; post-disturbance succession.
  
  Address:
  - Jaroslav Vido, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, 960 01 Zvolen, Slovakia. Department of Forest Botany, Dendrology and Geobiocoenology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemědelská 1665/1, 613 00 Brno, Czech Republic. (Corresponding author. Tel.: Fax.: Email: vido@tuzvo.sk)
  - Paulína Nalevanková, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, 960 01 Zvolen, Slovakia.
  - Martin Jančo, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská Cesta 9, 84104 Bratislava, Slovakia.
  - Daniel Kurjak, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, 960 01 Zvolen, Slovakia. Institute of Forest Ecology, Slovak Academy of Sciences, Ľ. Štúra 2, 96001 Zvolen, Slovakia.
  - Jozef Zverko, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, 960 01 Zvolen, Slovakia.
  - Jana Kurjaková, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, 960 01 Zvolen, Slovakia.
  - Lenka Malovcová, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, 960 01 Zvolen, Slovakia.
  - Jana Škvareninová, Faculty of Ecology and Environmental Sciences, Technical University in Zvolen, T. G. Masaryka 24, 960 01 Zvolen, Slovakia.
  - Jaroslav Škvarenina, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, 960 01 Zvolen, Slovakia. Earth Science Institute of the Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 304 - 313, doi: .
Scientific Paper, English

Anton Zvala, Ľubomír Lichner, Jozef Kollár, Irena D. Atanassova, Peter Šurda: Heating affects properties of forest soils with different texture: 1. Physical and chemical properties

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• Wildland fires affect physical and chemical properties of forest soils, and the magnitude of their effects depends on the soil temperature achieved during a fire. Laboratory heating of soil samples in muffle furnace was used to simulate a natural fire heating of forest soils, although it does not completely reproduce natural fire conditions. The effect of heating temperature of 100–900°C on particle size distribution, soil water repellency (SWR), soil organic carbon content (SOC) and pH was estimated in three soils differing in texture (sandy soil, silty-clay soil, and clay soil) sampled in coniferous and deciduous forests at Gbely (Areni-Gleyic Umbrisol), Hviezdoslavov (Fluvisol) and Gabčíkovo (Fluvisol), respectively. Decrease in the clay content and increase in the sand content was large in silty-clay and clay soils, but not as large in sandy soils. Surprisingly, heating the soil to 100°C, commonly used in soil moisture measurement, caused a decrease in clay content by half (the average value for all soils). This finding should be confirmed by further measurements on the soils from other regions, because the degree of aggregation depends also on the type of clay and other minerals. The persistence of SWR gradually increased in the heating temperature range 100–300°C in all three soils from coniferous forests and sandy soil from deciduous forest, and was absent in the remaining two soils. The SOC decreased and pH increased with increasing heating temperature.
  
  KEY WORDS: Heating; Temperature; Particle size distribution; Soil water repellency; Soil organic carbon; pH.
  
  Address:
  - Anton Zvala, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia.
  - Ľubomír Lichner, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: lichner@uh.savba.sk)
  - Jozef Kollár, Institute of Landscape Ecology, Slovak Academy of Sciences, Štefánikova 3, 81499 Bratislava, Slovakia.
  - Irena D. Atanassova, Institute of Soil Science, Agrotechnologies and Plant Protection, Agricultural Academy, Shosse Bankya Str. 7, 1331Sofia, Bulgaria.
  - Peter Šurda, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 314 - 322, doi: .
Scientific Paper, English

Thomas Fischer, Maik Veste: Kinetics of water sorption, EPS swelling and evaporation in biological soil crusts on reclaimed temperate dunes, Brandenburg, Germany

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• Biological soil crusts (BSCs) play a crucial role in regulating water infiltration into surface substrates; however, their exact hydrological effects remain a subject of ongoing debate. This study quantitatively investigates the kinetics of water immobilization through sorption and the swelling behavior of extracellular polymeric substances (EPS) during the wetting of dry BSCs on recultivated temperate dunes in Brandenburg. Crust samples dominated by the green alga Zygogonium ericetorum were collected from an inland dune in the Lusatian post-mining area. Following a multi-week drying phase, rehydration experiments were conducted using deuterium oxide (D2O) to avoid spectral interference with the O–H groups of the EPS. Using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the time-dependent shift of the O–D stretching vibrations was analyzed to determine the sorption kinetics of the biological crusts relative to an undisturbed mineral control. In parallel, gravimetric measurements monitored evaporation, while the EPS composition was characterized via ATR-FTIR spectroscopy. Spectroscopic analysis identified alginate as the primary organic component of the crust EPS. While the uncoated mineral control showed almost immediate water infiltration, the BSC samples exhibited a pronounced plateau in OD vibrations during the first three minutes, indicating an initial phase of free water at the surface. Between the 3rd and 12th minutes, a distinct redshift toward lower wavenumbers followed, reflecting the ongoing functional group reorganization, hydration, and EPS swelling, until thermodynamic equilibrium was reached after approximately 12 minutes. Gravimetric data also revealed a significantly higher and faster evaporation rate for the BSCs compared to the control. These results demonstrate that the alginate and EPS matrix of the biological soil crust acts as a water reservoir that hydrologically seals the surface, drastically limiting vertical infiltration into deeper soil layers while retaining water in a highly accessible surface pool. Furthermore, it is conceivable that this delayed water immobilization by the swelling EPS matrix provides a vital ecological benefit by buffering the crust microbiome against severe hypo-osmotic shock during rapid rewetting. However, direct microbial analyses are required to confirm this effect. By moving beyond conventional visual assessments or indirect macro-hydraulic inferences, this approach provides unprecedented molecular-scale insights into the rapid physicochemical transition from free to matrix-bound water during EPS hydration. To our knowledge, this study represents the first application of time-resolved diffuse reflectance infrared spectroscopy (DRIFTS) combined with deuterium oxide (D2O) rehydration to directly track water immobilization kinetics in biological soil crusts. By eliminating spectral interference from biopolymer hydroxyl groups, this approach provides unprecedented insights into the rapid physicochemical transition from free to matrix-bound water.
  
  KEY WORDS: Biological soil crusts; EPS swelling; Sorption kinetics; Alginate; DRIFTS; Infiltration; Evaporation.
  
  Address:
  - Thomas Fischer, Brandenburg University of Technology Cottbus-Senftenberg, Faculty of Ecology and Environmental Sciences, Cottbus, Germany. (Corresponding author. Tel.: Fax.: Email: thomas.fischer@b-tu.de)
  - Maik Veste, CEBra–Center for Energy Technology Brandenburg e.V., Cottbus, Germany. Department Molecular Botany, Institute of Biology, University of Hohenheim, Stuttgart, Germany.

J. Hydrol. Hydromech., Vol. 74, No. 3 - Early view, 2026, p. 323 - 330, doi: .
Scientific Paper, English

Giora J. Kidron, Bo Xiao: Does temperature-induced vapor flux trigger desert floods? The Negev exam-ple

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• High-magnitude floods characterize deserts, commonly explained by the high rain intensities coupled with the low vegetation cover, surface smoothness and the sealing capability of biocrusts. Nevertheless, runoff generation and the subsequent high-magnitude floods stand out when considering the high evaporation, the relatively dry desert surfaces and the high stoniness that characterize many of the surfaces. Also, the rain amount that stems from high intensity (convective) rains is not necessarily higher than in subhumid regions, and indeed, based on a study of runoff dynamics over biocrusted sand dunes in the Negev Desert, runoff was generated already at low to medium intensities of 9-12 mm/h, explained by the high-water absorbance of the extracellular polymeric substances (EPS) that is excreted by the variable microorganisms inhabiting the biocrust. In the Negev, convective intensities were found to primarily result from unstable daily atmospheric conditions following by daytime surface heating. Daytime heating, coupled with cool/cold nighttime temperatures, were also found responsible for the occurrence of temperature-induced vapor flux (TIVF) and the subsequent occurrence of wet-dry cycles that may last for up to 1-2 weeks following a rain event. We hypothesize that the wet cycles which stem from an upward vapor movement from the warm subsurface soil towards the cool soil surface during the night result in biocrust saturation, triggering in turn runoff generation. By wetting the surface (commonly already during the late afternoon), TIVF may trigger runoff in deserts. This is supported hereafter following a thorough four year-long analysis (1990-1994) of rain-runoff relationship that took place on a pair of biocrusted plots covering dunes in the Negev. Albeit the ~20% higher intensities measured during daytime that should have resulted in higher runoff, nighttime runoff amount, runoff flow duration, runoff yield per average rain intensities and runoff yield per the average intensity of each event were 1.8-, 1.5-, 1.5- and 3.1-fold higher during nighttime in comparison to daytime. It is suggested that in addition to the role played by runoff intensity and the surface properties, TIVF provides an additional mechanism that explains the high runoff generation already at low- to medium-intensities, also explaining, at least partially, the relatively high runoff yield and potent floods in the Negev and other arid regions.
  
  KEY WORDS: Biocrusts; Dew; Distillation; Runoff; Wet-dry cycles.
  
  Address:
  - Giora J. Kidron, Institute of Earth Sciences, The Hebrew University, Givat Ram Campus, Jerusalem 91904, Israel. (Corresponding author. Tel.: Fax.: Email: kidron@mail.huji.ac.il)
  - Bo Xiao, Key Laboratory of Arable Land Conservation in North China, Ministry of Agriculture and Rural Affairs, China. College of Land Science and Technology, China Agricultural University, Beijing 100193, China.