TY - GEN A1 - Fischer, Thomas A1 - Veste, Maik A1 - Bens, Oliver A1 - Hüttl, Reinhard F. T1 - Dew formation on the surface of biological soil crusts in central European sand ecosystems T2 - Biogeosciences discussions N2 - Dew formation was investigated in three developmental stages of biological soil crusts (BSC), which were collected along a catena of an inland dune and in the initial substrate. The Penman equation, which was developed for saturated surfaces, was modified for unsaturated surfaces and used for prediction of dewfall rates. The levels of surface saturation required for this approach were predicted using the water retention functions and the thicknesses of the BSCs. During a single event, dewfall increased with crust development from 0.08 kg m−2 for the initial substrate to 0.10, 0.20 and 0.25 kg m−2 for crusts stages 1 to 3, respectively, which was well reflected by the model response. The suggested mechanism of dew formation involves a delay in water saturation in near-surface soil pores and EPS where the crusts were thicker and where the water capacity was high, resulting in elevated vapor flux towards the surface. The results also indicate that the amount of dewfall was too low to observe water flow into deeper soil. Analysis of the soil water retention curves revealed that, despite the sandy mineral matrix, moist crusts with clogged by swollen EPS pores exhibited a clay-like behavior. It is hypothesized that BSCs gain double benefit from suppressing their competitors by runoff generation and from improving their water supply by dew collection. Despite higher amounts of dew, the water availability to the crust community decreases with crust development, which may be compensated by ecophysiological adaptation of crust organisms, and which may further suppress higher vegetation or mosses. Y1 - 2012 U6 - https://doi.org/10.5194/bgd-9-8075-2012 VL - 9 SP - 8075 EP - 8092 ER - TY - GEN A1 - Elmer, Michael A1 - Bachmann, Ute A1 - Gutsch, Martin A1 - Schröder, Jens A1 - Bäucker, Ernst A1 - Lange, Mike A1 - Clauder, Lothar A1 - Bens, Oliver A1 - Suckow, Felicitas A1 - Kätzel, Ralf A1 - Bues, Claus-Thomas A1 - Frommhold, Heinz A1 - Sonntag, Herbert A1 - Fischer, Thomas A1 - Hüttl, Reinhard F. T1 - OakChain: Eichen-Kiefern-Mischbestände im Spannungsfeld von Klimawandel, Waldumbau und internationalem Holzmarkt T2 - Forst und Holz Y1 - 2009 SN - 0932-9315 VL - 64 IS - 7/8 SP - 26 EP - 29 ER - TY - GEN A1 - Rodionov, Andrei A1 - Nii-Annang, Seth A1 - Fischer, Thomas A1 - Gattinger, Andreas A1 - Bens, Oliver A1 - Raab, Thomas A1 - Hüttl, Reinhard F. T1 - Cross-linked polyacrylates in post-mining substrates: persistence and effects on plant growth T2 - Soil Use and Management N2 - Application of hydrophilic polymers composed of cross-linked polyacrylate can improve soil water-holding capacity and accelerate the restoration of post-mining substrates. In this work, we studied the persistence of a polyacrylate polymer incorporated into a soil and its impact on plant nutrients at a reclamation site of former lignite mining in Lusatia (Germany). In contrast to autumn application, the incorporation of the polymer enhanced the sequestration of plant-derived carbon in the soil, which was reflected by a significant increase in the concentration of a lignin marker. Attenuated total reflexion–Fourier transform infrared spectra (ATR-FTIR) and total elemental contents in the applied polymer suggested an intensive cation exchange between the polymer framework and the soil-forming substrate. In addition, there was an enrichment of carbonaceous material, which seems to reduce the swelling and thus the water-holding capacity of the cross-linked polyacrylate. Conversely, this process protected the polymer structure from rapid decomposition. Y1 - 2014 U6 - https://doi.org/10.1111/sum.12103 SN - 1475-2743 VL - 30 IS - 1 SP - 78 EP - 87 ER - TY - GEN A1 - Fischer, Thomas A1 - Veste, Maik A1 - Eisele, Andreas A1 - Bens, Oliver A1 - Spyra, Wolfgang A1 - Hüttl, Reinhard F. T1 - Small Scale Spatial Heterogeneity of Normalized Difference Vegetation Indices (NDVI) and Hot Spots of Photosynthesis in Biological Soil Crusts T2 - Flora N2 - Normalized Difference Vegetation Indices (NDVIs) are typically determined using satellite or airborne remote sensing, or field portable spectrometers, which give an averaged signal on centimetre to metre scale plots. Biological soil crust (BSC) patches may have smaller sizes, and ecophysiological, hydrological as well as pedological processes may be heterogeneously distributed within this level of resolution. A ground-based NDVI imaging procedure using low-cost equipment (Olympus Camedia 5000z digital camera equipped with a Hoya R72 infrared filter) was developed in this study to fill this gap at the level of field research, where carrying costly and bulky equipment to remote locations is often the limiting factor for data collection. Method principle and field data are presented, and the field experiment was deepened comparing NDVI measurements and CO2 turnover of soil crust samples in the laboratory, backing the reliability of the approach. A commercially available colour rendition chart with known red (600–700 nm) and NIR (800–900 nm) reflectances was placed into each scene and used for calibration purposes on a per-image basis. Generation of NDVI images involved (i) determination of red and NIR reflectances from the pixel values of the red and NIR channels, respectively, and (ii) calculation and imaging of the NDVI, where NDVI values of −1 to +1 were mapped to grey values of 0 to 255. The correlation between NDVI values retrieved from these images and NDVI values determined using field spectrometry was close (r2 = 0.91), the 95% confidence interval amounted to 0.10 NDVI units. The pixel resolution was 0.8 mm in the field and 0.2 mm in the laboratory, but can still be improved significantly with closer distance to the crust or with higher camera resolution. NDVI values obtained using the new method were related to the net CO2 uptake of BSCs, where both slope and correlation coefficient of the respective regression function conformed with literature data. Geostatistical analysis revealed that both spatial variability of net CO2 uptake as well as size of individual hot spots of this parameter increased with crust development. The latter never exceeded 4 mm in the investigated crusts, which points to the necessity of high resolution imaging for linking remote sensing with ecophysiology. Perspectively, the new method could be used for field monitoring of both biological soil crusts and vascular vegetation. Y1 - 2012 U6 - https://doi.org/10.1016/j.flora.2012.01.001 VL - 207 IS - 3 SP - 159 EP - 167 ER - TY - GEN A1 - Fischer, Thomas A1 - Veste, Maik A1 - Schaaf, Wolfgang A1 - Dümig, Alexander A1 - Kögel-Knabner, Ingrid A1 - Wiehe, Wolfgang A1 - Bens, Oliver A1 - Hüttl, Reinhard F. T1 - Initial pedogenesis in a topsoil crust 3 years after construction of an artificial water catchment in Brandenburg, NE Germany T2 - Biogeochemistry N2 - Cyanobacteria and green algae present in biological soil crusts are able to colonize mineral substrates even under extreme environmental conditions. As pioneer organisms, they play a key role during the first phases of habitat colonization. A characteristic crust was sampled 3 years after installation of the artificial water catchment “Chicken creek”, thus representing an early successional stage of ecosystem development. Mean annual rainfall and temperature were 559 mm and 9.3°C, respectively. We combined scanning electron microscopy (SEM/EDX) and infrared (FTIR) microscopy to study the contact zone of algal and cyanobacterial mucilage with soil minerals in an undisturbed biological soil crust and in the subjacent sandy substrate. The crust was characterized by an approximately 50 μm thick surface layer, where microorganisms resided and where mineral deposition was trapped, and by an approximately 2.5 mm thick lower crust where mineral particles were stabilized by organo-mineral structures. SEM/EDX microscopy was used to determine the spatial distribution of elements, organic compounds and minerals were identified using FTIR microscopy and X-ray diffraction (XRD). The concentration of organic carbon in the crust was about twice as much as in the parent material. Depletion of Fe, Al and Mn in the lower crust and in the subjacent 5 mm compared to the geological substrate was observed. This could be interpreted as the initial phase of podzolization. Existence of bridging structures between mineral particles of the lower crust, containing phyllosilicates, Fe compounds and organic matter (OM), may indicate the formation of organo-mineral associations. pH decreased from 8.1 in the original substrate to 5.1 on the crust surface 3 years after construction, pointing to rapid weathering of carbonates. Weathering of silicates could not be detected. Y1 - 2010 U6 - https://doi.org/10.1007/s10533-010-9464-z SN - 1573-515X VL - 101 IS - 1-3 SP - 165 EP - 176 ER - TY - CHAP A1 - Bachmann, Ute A1 - Bens, Oliver A1 - Elmer, Michael A1 - Fischer, Thomas A1 - Raab, Thomas A1 - Hüttl, Reinhard F. ED - Elmer, Michael ED - Kätzel, Ralf ED - Bens, Oliver ED - Bues, Claus-Thomas ED - Sonntag, Herbert ED - Hüttl, Reinhard F. T1 - Boden und Standortqualität T2 - Nachhaltige Bewirtschaftung von Eichen-Kiefern-Mischbeständen : im Spannungsfeld von Klimawandel, Waldumbau und internationalem Holzmarkt Y1 - 2009 SN - 978-3-86581-196-7 SP - 31 EP - 44 PB - oekom CY - München ER - TY - CHAP A1 - Fischer, Thomas A1 - Veste, Maik A1 - Eisele, Andreas A1 - Bens, Oliver A1 - Spyra, Wolfgang A1 - Hüttl, Reinhard F. T1 - High resolution mapping of Normalized Difference Vegetation Indices (NDVI) of biological soil crusts T2 - EGU General Assembly 2012, held 22-27 April, 2012 in Vienna Y1 - 2012 N1 - EGU2012-7052 PB - European Geophysical Society CY - Katlenburg-Lindau ER -