Linking surface and subsurface properties of biocrusted and non-biocrusted habitats of fine-grained fluvial sediments (playas) from the Negev Desert

Abstract

Abstract:With biocrusts playing a cardinal role in C and N fixation in arid zones, information regarding the factors that determine their limits of growth is of uttermost importance for the study of ecosystem structure and function. This is also the case in the western Negev dunefields, where although abundant on the sandy surfaces, biocrusts are scarce on finegrained (mainly loessial) sediments, termed playas. In the Nizzana research site (NRS), visibly distinct surfaces, with and without biocrusts were noted within a single playa. In an attempt to characterize these distinct surfaces, a set of random measurements were carried out, which included measurements of crack density, microrelief and chlorophyll content of the upper 0-1 cm. Following a cluster analysis, four distinct types of surfaces (hereafter habitats) were defined, one with substantial amount of chlorophyll content which can be regarded as biocrust (P4), and three non-crusted surfaces (P1-P3). Within each type, two 50 cm-deep pits were dug and the pH, electrical conductivity (EC) and fine (silt and clay) content (FC) of samples collected at 1-5, 5-10, 10-20, 20-30, 30-40 and 40-50 cm-depth were analyzed. In addition, periodical moisture measurements were carried out (in pairs) to a depth of 0-20 cm at each surface type during 2013/14. All non-crusted habitats (P1-P3) were characterized by loessial subsurface sediments. Conversely, P4 was either characterized by loessial subsurface sediments (and in this case it was characterized by a slightly concave surface) or having a sandy subsurface (at ~5-10 cm depth). While the non-crusted surfaces exhibited low moisture content, P4 exhibited deeper and higher moisture content explained either by the more sandy sediments or by lower water loss through runoff. The findings point to the close link between surface and subsurface properties and indicate that water availability may explain biocrust establishment and growth also at the loessial playa surfaces. Biocrusts may thus serve as bioindicators for habitats with high moisture content.

Halophilic Algal Communities in Biological Soil Crusts Isolated From Potash Tailings Pile Areas

“…Until now, only one study has recorded terrestrial algae in soils with an EC Sat up to 260 mS cm −1 (Tsujimura et al, 1998). Other studies on biocrusts on saline soils reported only sites with EC Sat values <30 mS cm −1 (e.g., Fox et al, 2009;Kidron, 2016;Sandoval Pérez et al, 2016;Schulz et al, 2016;Zhou et al, 2016;Ghiloufi et al, 2017;Kakeh et al, 2018). In the present study, however, much higher ranges of EC Sat (up to 950 mS cm −1 ) were documented, emphasizing the extreme soil salinities of the sampling sites.…”

Biocrust research: A critical view on eight common hydrological‐related paradigms and dubious theses

“…There is additional supportive evidence for the above‐mentioned conclusion from NRS. Thus, for instance, (a) as found by Littmann () and Kidron et al (), there is no correlation between dust input and crust biomass; (b) as found by Littmann () and Felde, Chamizo, Felix‐Henningsen, and Drahorad (), the amount of montromillonite (which is the most potent clay type for water absorption and CEC in the Eastern Mediterranean) is small (25% of the clays); (c) nutrient addition does not necessarily benefit crust growth (Bu, Wu, Yang, & Zheng, ; Strong, Bullard, Burford, & McTainsh, ); and (d) as found by Kidron (), biocrusts are readily established on the dune crest even with <1% of fines (out of which clay comprised only 10–20% and expanding clay only 25% of the total amount of the clay,i.e., with only 0.005% of expanding clays), whereas almost absent from flat playa surfaces with 50–98% of fines (Kidron, ). It follows that a substrate with higher dust or fine content (and therefore with higher CEC or nutrients) does not necessarily guarantee a better crust growth (Kidron et al, ).…”

“…Swelling results in a substantial increase in the WHC, leading to infiltration-excess conditions Mazor et al, 1996) and subsequently to Hortonian run-off (Kidron & Yair, 1997;Kidron, 1999, 2011, 2014, Kidron, 2016, Kidron & Zohar, 2016Kidron & Büdel, 2014;Kidron et al, 2000, 2003. While runoff due to EPS swelling and subsequently pore clogging was demonstrated in numerous publications, only sporadic reports claim that EPS enhance infiltration.…”

The effect of biological soil crusts on soil moisture dynamics under different rainfall conditions in the Tengger Desert, China

“…At the same time, surface roughness could affect the persistence time of rainfall (X. R. Li et al, ). Generally, well developed BSCs (e.g., moss dominated crust) showed a higher surface roughness, and thus allowing more time to infiltrate (Kidron, ). Crust thickness was a negative factor in water infiltration, as crust thickness was significantly correlated to water resistance capacity (B. Li et al, ; Yang et al, ; Zaady et al, ).…”

“…To date, numerous studies have discussed the role of BSCs in infiltration process, but the results are far from conclusive. On the one hand, BSCs increase infiltration for its increased water holding capacity and biomass, and this effect increases with the developmental level of biological crusts (Belnap, Wilcox, Van Scoyoc, & Phillips, 2013;Bu, Wu, Han, Yang, & Meng, 2015;Chamizo et al, 2011;Chamizo, Cantón, Miralles, & Domingo, 2012;Kidron, 2016;Kidron & Benenson, 2014). On the other hand, BSCs decrease infiltration for the change of hydraulic properties, such as water repellency and hydraulic conductivity and the increase of crust thickness with the development of biological crusts (Coppola et al, 2011;Keck, Felde, Drahorad, & Felix-Henningsen, 2016;Li, Tian, Jia, Zhang, & Liu, 2010;Lichner et al, 2013;Yang et al, 2016;Zaady, Katra, Yizhaq, Kinast, & Ashkenazy, 2014).…”