Editorial: Ecological Development and Functioning of Biological Soil Crusts After Natural and Human Disturbances

[no abstract available

Determining Millimeter‐Scale Maps of Cation Exchange Capacity at Macropore Surfaces in Bt Horizons

During preferential flow in structured soils, solute transport is largely restricted to a complex network of macropores. Clay–organic coatings of macropore surfaces determine soil physicochemical properties relevant for mass transport and carbon and nutrient turnover, such as the cation exchange capacity (CEC). However, due to the lack of an appropriate measurement approach, the small‐scale spatial distributions of the CEC and its quantities are unknown to date. The objective of this work was to develop a method for predicting the millimeter‐ to centimeter‐scale, two‐dimensional spatial distribution of the CEC at intact macropore surfaces. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to analyze bulk soil and separated coating material and for intact macropore surfaces as DRIFT mapping. To determine effective CEC (CECeff), a reduction of soil mass down to 0.5 g for use in the standard barium chloride batch method was tested to account for the limited amount of soil material that can be separated from thin macropore coatings. Linear and partial least squares regression analyses were applied to predict the CECeff distribution at intact macropore surfaces for samples from Luvisol Bt horizons from loess (L) and glacial till (T) using DRIFT spectral data. The highest CECeff values were found for coatings and pinhole fillings rich of clay–organic material (L: 38 cmol kg−1; T: 29 cmol kg−1) compared with low CECeff values of uncoated cracks and earthworm burrows that were similar to those of bulk soil (L: 21 cmol kg−1; T: 14 cmol kg−1). The location of millimeter‐ to centimeter‐sized regions with increased CECeff levels at intact macropore surfaces corresponded with the location of clay–organic coatings. The proposed method allows determining the CEC at macropore surfaces to quantify their effect on nutrient transport by preferential flow as well as on plant nutrient supply in macropores that may serve as preferential growth paths for plant roots

Biological soil crusts cause subcritical water repellency in a sand dune ecosystem located along a rainfall gradient in the NW Negev desert, Israel

The biological soil crusts (BSCs) in the NW Negev cause local water redistribution by increasing surface runoff. The effects of pore clogging and swelling of organic and inorganic crust components were intensively investigated in earlier studies. However, the effect of water repellency (WR) was not addressed systematically yet. This study investigates subcritical WR of BSCs in three different study sites in the NW Negev. For this purpose, three common methods to determine soil WR were used: (i) the repellency index (RI) method (ii) the water drop penetration time (WDPT) test and (iii) the Wilhelmy plate method (WPM). Furthermore, the potential influence of WR on local water redistribution is discussed and the applied methods are compared. We found the BSC to be subcritically water repellent. The degree of WR may only affect water redistribution on a microscale and has little influence on the ecosystem as a whole. The RI method was clearly the most appropriate to use, whereas the WDPT and the WPM failed to detect subcritical WR

Development of the polysaccharidic matrix in biocrusts induced by a cyanobacterium inoculated in sand microcosms

Soil inoculation with cyanobacteria (cyanobacterisation) is a biotechnological method widely studied to improve soil quality and productivity. During their growth on soil, cyanobacteria excrete exopolysaccharides (EPS) which glue trichomes to soil particles, in a three-dimensional extracellular polymeric matrix. EPS productivity is an important screening parameter to select proficient inoculants, and is affected by growth conditions and abiotic stresses. In this study, we evaluated the capability of the cyanobacterium Schizothrix c.f. delicatissima AMPL0116 to form biocrusts when inoculated in sand microcosms under stressing conditions, and the characteristics of the synthesized polymeric matrix. In parallel, we evaluated the characteristics of exopolysaccharidic exudates of the strain when grown in liquid culture, under optimal growth setting. Our results pointed out at significant differences of the exopolymers produced in the two conditions in terms of monosaccharidic composition and molecular weight distribution, and prove the capability of S. c.f. delicatissima AMPL0116 to form stable bio-aggregates on sandy soils.Soil inoculation with cyanobacteria (cyanobacterization) is a biotechnological method widely studied to improve soil quality and productivity. During their growth on soil, cyanobacteria excrete exopolysaccharides (EPSs) which glue trichomes to soil particles, in a three-dimensional extracellular polymeric matrix. EPS productivity is an important screening parameter to select proficient inoculants and is affected by growth conditions and abiotic stresses. In this study, we evaluated the capability of the cyanobacterium Schizothrix cf. delicatissima AMPL0116 to form biocrusts when inoculated in sand microcosms under stressing conditions, and the characteristics of the synthesized polymeric matrix. In parallel, we evaluated the characteristics of exopolysaccharidic exudates of the strain when grown in liquid culture, under optimal growth setting. Our results pointed out at significant differences of the exopolymers produced in the two conditions in terms of monosaccharidic composition and molecular weight distribution, and proved the capability of S. cf. delicatissima AMPL0116 to form stable bioaggregates on sandy soils

Wet sieving versus dry crushing: Soil microaggregates reveal different physical structure, bacterial diversity and organic matter composition in a clay gradient

Gefördert im Rahmen des Projekts DEA

Comment on ‘Kidron, G. J. (2018). Biocrust research: A critical view on eight common hydrological-related paradigms and dubious theses. Ecohydrology, e2061’

According this discussion the eight putative paradigms advanced by Kidron (2018) cannot be upheld nor are they commonly held among hydrologists, ecologists, or microbiologists that investigate biocrusts