Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review

The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones... J. Hydrol. Hydromech., 69, 2021, 4, 360–368 ©2021. This is an open access article distributed DOI: 10.2478/johh-2021-0028 under the Creative Commons Attribution ISSN 1338-4333 NonCommercial-NoDerivatives 4.0 License The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review Giora J. Kidron Institute of Earth Sciences, The Hebrew University of Jerusalem, Givat Ram Campus, Jerusalem 91904, Israel. Tel: +972-54-4967-271. Fax: 972-2-566-2581. E-mail: kidron@mail.huji.ac.il Abstract: Although playing an important role in shaping the environment, the mechanisms responsible for runoff initia- tion and yield in arid and semiarid regions are not yet fully explored. With infiltration-excess overland flow, known also as Hortonian overland flow (HOF) taking place in these areas, the uppermost surface 'skin' plays a cardinal role in runoff initiation and yield. Over large areas, this skin is composed of biocrusts, a variety of autotrophs (principally cyanobacte- ria, green algae, lichens, mosses) accompanied by heterotrophs (such as fungi, bacteria, archaea), which may largely dictate the infiltration capability of the surface. With most biocrust organisms being capable of excreting extracellular polymeric substances (EPS or exopolymers), and growing evidence pointing to the capability of certain EPS to partially seal the surface, EPS may play a cardinal role in hindering infiltration and triggering HOF. Yet, despite this logic thread, great controversy still exists regarding the main mechanisms responsible for runoff generation (runoff initiation and yield). Elucidation of the possible role played by EPS in runoff generation is the focus of the current review. Keywords: Biological soil crusts; Extracellular polymeric substances; Pore clogging; Hydrophobicity; Infiltration-excess overland flow; Water repellency. 1 INTRODUCTION subsequently published (Fischer et al., 2010; Kidron and Yair, 1997; Lichner et al., 2012). The research also focused on the Mainly attributed to the low vegetal cover, high-magnitude EPS properties. runoff events and occasional hazardous floods commonly take Research aiming to elucidate the different constituents of bi- place in arid and semiarid regions. In contrast to humid areas ocrust-induced EPS and the possible roles played by the EPS is where runoff takes place once a large volume of soil reaches indeed not uncommon. Excreted by microorganisms and micro- saturation, known therefore as saturation excess overland flow flora (cyanobacteria, archaea, bacteria, fungi, diatoms, green (SOF) (Beven and Kirkby, 1979; Dunne, 1990; Dunne and algae, lichens, but not by mosses) of the biocrusts, EPS is be- Black, 1970), runoff in arid and semiarid regions takes place lieved to protect and to assist the cell against possible stress and even when almost the entire soil profile is dry. Runoff takes danger, and to accomplish some physiological needs. EPS place due to infiltration-excess overland flow, known also as facilitate cell adhesion and cohesion (Galle and Arendt, 2014; Hortonian overland flow (HOF), during which only the upper- Rossi et al., 2018), filament gliding and therefore motility most soil skin reaches saturation, thus hindering water infiltra- (Campbell, 1979; Pringault and Garcia-Pichel, 2004), protect- tion into the subsurface, which may therefore remain dry or ing the cell from UV radiation (Rossi et al., 2018), and the relatively dry (Blackburn, 1975; Cammeraat, 2004; Horton, nitrogenase from excess oxygen (Otero and Vincenzini, 2003). 1933). It plays a role in scavenging essential nutrients (Rossi et al., The crust thickness required to impede infiltration is as- 2018), and is believed to scavenge free radicals which other- sumed to be extremely thin, within millimeters. Following the wise may harm the cell (Chen et al., 2009). Among other roles widely-held belief that physical crusts trigger runoff, a possible attributed to EPS is its role to protect the cell from lysis (Eh- link between the thickness of physical crusts and runoff was ling-Schultz and Schere, 1999) and from shifts in the environ- made. According to some scholars it is <1 mm-thick (Epstein mental conditions such as desiccation, salinity, extreme tem- and Grant, 1993; Heil et al., 1997; McIntyre, 1958; Onofiok peratures, pH or exposure to toxic materials (Demig and Young, 2017; Ehling-Schultz and Schere, 1999). The EPS is and Singer, 1984; Pagliai et al., 1983), while according to oth- ers it may be 2–4 mm thick (Chen et al., 1980; de Jong et al., also believed to protect the cell from freezing damage (Nagar et 2011; Tarchitzky et al., 1984), i.e., within the range of thickness al., 2021) and from viral/bacterial infection and predation (Brüll of most biocrusts. et al., 2000). While the above-mentioned roles are widely ac- With biocrusts (biological soil crusts) constituting the upper cepted by the scientific community, this is not the case with the skin of extensive areas in arid and semiarid regions (Rodriguz- possible hydrological role played by the EPS, as reflected in Caballero et al., 2018) and with many of the biocrust microor- recent reviews (Mager and Thomas. 2011; Rossi and De Philip- ganisms being known to excrete exopolymers (extracellular pis, 2015), and the absence of this category in a list of major polymeric substances, EPS), which may affect surface hydrolo- roles played by the EPS most recently published (Rossi et al., gy (Brotherson and Rushforth, 1983; Chamizo et al., 2016; 2018). Kidron et al., 2003; Li et al., 2021; Sun et al., 2021; Xiao et al., It is customary to divide the EPS to tightly bound EPS (TB- 2019a), research on the interrelations between biocrusts and EPS), whether constituting sheaths (around filamentous cells) biocrust-induced EPS and runoff was called for. Papers aiming or capsules (around single cells) and loose bound (released, scattered) EPS (LB-EPS), i.e., slime which has an amorphous to study the possible relationships between these variables were 360 The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review shape, not necessarily related to the shape of the cell (More et which will facilitate aeration and water infiltration (Cantón et al., 2014; Otero and Vincenzini, 2003; Pereira et al., 2009). al., 2020; Or et al., 2007; Redmile-Gordon et al., 2020). Thus While the slime is mostly comprised of low molecular weight for instance EPS shrinkage during desiccation might promote (MW) polysaccharides, the sheaths are complex, mainly char- infiltration through the soil crevices. While these functions acterized by high-MW molecules, and as such are much less were convincingly shown and are not a matter of dispute, some degradable. This may explain the fact that unlike LB-EPS scholars maintain that higher rates of infiltration are induced by which can be extracted by water, the use of Na2EDTA is re- subsurface EPS, especially in developed crusts, which will quired for the extraction of TB-EPS. It was suggested that TB- hinder in turn runoff generation (Belnap, 2006; Brotherson and EPS is responsible for the crust structure (De Philippis, 2015). Rushforth, 1983; Chamizo et al., 2013; Rossi et al., 2012). This The high capability of EPS to absorb high amounts of water conclusion is however very problematic. EPS as well as clay (Chenu, 1993; Or et al., 2007) may have important hydrological tend to absorb water within minutes, resulting in the closure of consequences. For instance, EPS may hinder evaporation and the crevices (Fox et al., 2004). This is especially the case once facilitate longer cell activity (Chenu, 1993). This may be the higher amounts of EPS, which are associated with biocrusts and case for some cyanolichens such as Collema sp. which takes therefore concentrate at the surface, will readily swell upon advantage of the short rain events in deserts to accumulate wetting, blocking easy entry of rainwater to depth. Further- substantial amounts of water, which will facilitate long hours of more, the view that soil aggregation hinders runoff does not photosynthesis, especially during the cool weather that charac- coincide with the prevailing runoff mechanism which takes terize the cool season rains (Lange et al., 1998). On the other place in arid and semiarid regions. Due to limited rain, SOF hand, with some EPS having dark sunscreen pigments (Ehling- does not take place in these areas, and runoff generation takes Schulze and Shere, 1999), the resultant reduction in the albedo place only following HOF (Horton, 1933; Kidron, 2021), which may lead to temperature rise which may increase evaporation implies infiltration impediment only following surface satura- (Harper and Marble, 1988; Kidron and Tal, 2012; Xu and tion regardless of subsurface water content and regardless Singh, 2001), and as such may not necessarily act to prolong whether the subsurface is aggregated or not. cell activity. This was clearly reflected on sand-covered biocrusts at the An additional suggested hydrological role of EPS is the fa- Nizzana research site (NRS) in the Hallamish dune field, Negev cilitation of vapor absorbance and subsequent dew formation, Desert, Israel. Even when covering semi pure sand (⁓98% sand suggested to serve as an additional and important water source with only ⁓2% of silt and clay), extremely thin immature cya- for biocrusts (Colica et al., 2014; Fischer et al., 2012; Hage- nobacterial crusts, only 0.5 mm thick, were able to generate mann et al., 2015; Jia et al., 2014; Lange et al., 1992; Mager runoff (Kidron, 2015). Similarly, 1 mm-thick biocrusts which and Thomas, 2011; Veste et al., 2001). While reported to trig- covered the xeric aspects of the dunes commonly generate ger vapor absorption by Colica et al. (2014) following cyano- runoff (Kidron, 1999; Kidron et al., 2003). With typical soils, bacteria inoculation in the Hobq Desert in China, extensive some of which are well aggregated, having infiltration rates of field measurements, which were carried out in the dewy Negev, 10–150 mm/h (Dunkerley, 2000; Kato et al., 2009; Wood and failed to show vapor condensation on the ground (Kidron and Blackburn, 1981), i.e., substantially lower than sand (having Kronenfeld, 2020a,b). Only once, very limited dew formation >300 mm/h of infiltration; Lichner et al., 2010; Xiao et al., was noted (Kidron et al., 2002). Yet, based on a detailed analy- 2019b), one may safely conclude that runoff over the 0.5 mm- sis, it was too short to allow for net photosynthesis by the cya- thick biocrusts was not impacted by the underlying sand, but nobacterial biocrusts (Kidron and Starinsky, 2019), therefore rather by the biocrust. With HOF being the prevailing mecha- casting doubt on the possible role played by EPS in providing nism that determines runoff generation in arid and semiarid dew water which will serve as an additional water source for regions, the aggregation capability of the subsurface is of minor the cyanobacterial biocrusts. No net photosynthesis was also relevance. recorded from a mixed cyanobacteria and crustose lichens in the Negev following dew (Wilske et al., 2008). Contrary to 2.2 Hydrophobicity detached cobbles or stones which readily condense dew and subsequently serve as an important water source for the stone- Hydrophobicity (water repellency) is a temporal phenome- dwelling lichens (Lange et al., 1970), minimum temperatures at non (Francis et al., 2007) during which a switch in the molecule the soil surface rarely reach the dew point temperature (Td) – a position of hydrophyllic and hydrophobic ends takes place prerequisite for dew formation (Beysens, 2018). (Hallett, 2008). Accordingly, with moisture decrease, the hy- Not less controversial is the possible effect of EPS on infil- drophilic ends tend to strongly bond with each other leaving the tration and runoff. In light of the cardinal role played by runoff hydrophobic ends exposed, resulting in hydrophobicity. While in shaping many aspects of the environment (hydrological, the duration during which the soil turns hydrophobic may be geomorphological, pedological, ecological), elucidation of the long, the process during which hydrophobicity ceases is how- possible role played by EPS in runoff generation is of major ever rapid, sometimes within minutes (Oostindie et al., 2013). importance. Toward this end, the current state-of-the art Some of the biocrust population, such as cyanobacteria, algae, knowledge will be briefly presented, ungrounded conclusions bacteria, and fungi were found to posses temporal hydrophobic published in the literature will be discussed, and a wide array of properties, assumed to be caused by EPS (Mugnai et al., direct and indirect evidence which point to the possible role of 2020a). EPS in runoff generation will be analyzed. Hydrophobicity was extensively reported from humid re- gions (Dekker and Ritsema, 1994, 2000; Doerr et al., 2006; 2 THE POSSIBLE INVOLVEMET OF EPS IN RUNOFF Drahorad et al., 2013; Fischer et al., 2010, 2013; Jungerius and GENERATION van der Muellen, 1988; Lichner et al., 2013; Rutin, 1983). 2.1 Enhanced soil aggregation However, runoff was convincingly shown to result from hydro- phobicity mainly in northern and central Europe (Fischer et al., With EPS assisting in cell adhesion and cohesion, EPS may 2010; Lichner et al., 2010, 2012, 2018). The first example that I increase soil aggregation, contributing to a better soil structure am aware of and which linked between hydrophobicity and 361 Giora J. Kidron runoff generation on biocrusts was reported from the Dutch 1997). Additional supportive evidence was obtained when the coast during the end of the summer (Jungerius and de Jong, ratio of total carbohydrates to the chlorophyll content was 1989; Rutin, 1983). While hydrophobicity was also reported sought. Thus, assuming a similar amount of carbohydrates from semiarid regions (Chamizo et al., 2012; Mayor et al., within a single cell, and given the fact that most EPSs are car- 2009; Rodriguez-Caballero et al., 2013), the link between hy- bohydrates (Mazor et al., 1996), excess of carbohydrates rela- drophobicity and runoff was not yet substantiated. tive to the chlorophyll content (i.e., high ratio of carbohydrates At the subhumid Dutch coast hydrophobicity was reported to chlorophyll) may attest to carbohydrates which are located following unusual weather conditions during which a long dry outside the cell walls, i.e., extracellular carbohydrates, which period followed a wet period, i.e., during the end of the sum- constitute the majority of the EPS (De Brower and Stal, 2001; mer. Runoff generation took place regardless of rain intensities Kidron et al., 1999). Indeed, when the runoff yield of variable (Rutin, 1983). It was temporal and vanished once the surface plots having 5 different crust types was compared against the was sufficiently wetted. According to Oostindie et al. (2013), ratio of carbohydrates to chlorophyll, a linear relation was hydrophobicity ceased once the moisture content of sand reach- obtained, pointing to a possible link between EPS and runoff generation (Kidron et al., 2003). es ⁓3%. One may therefore conclude that (a) hydrophobicity This measure for assessing the amount of EPS is obviously may only take place once a very dry spell follows a wet period, crude and may be applicable for a similar population of micro- such as at the end of the summer or during long breaks between organisms characterizing habitats with similar climate and soil rain events, (b) runoff induced by hydrophobicity will cease properties. For a more comprehensive comparison of different once the soil gets sufficiently wet, (c) runoff induced by hydro- climates and different soils, a study of the properties of the phobicity will take place regardless of rain intensity, as was constituents of the EPS is required. This was done once a com- indeed recorded at the Dutch coast (Rutin, 1983). parison between the cyanobacterial biocrusts of NRS (which Runoff due to hydrophobicity was thought to take place in receive an annual precipitation of 95 mm) and the cyanobacte- the Negev (Felde et al., 2014; Keck et al., 2013), the Tabernas ria-algae biocrust that cover the Israeli Mediterranean coast, the (Chamizo et al., 2012; Rodriguez-Caballero et al., 2013), and Nizzanim dune field (NIM) (which receives an annual precipi- the Sahel (Malam-Issa et al., 2009; Talbot and Williams, 1978), tation of 500 mm) was carried out. The comparison was trig- but nevertheless no convincing data for meter-scale runoff gered by the different populations of the crusts (cyanobacterial which stems from hydrophpbocity were yet published. On the in NRS and cyanobacteria-algae in NIM) and by the fact that contrary, in all places a close link between rain intensity and while runoff was commonly produced in NRS already during runoff took place, and runoff generation was higher on the wet medium rain intensities as low as 9 mm/h (Kidron and Yair, soils, all pointing to runoff due to pore clogging rather than 1997), no runoff was generated by the NIM crust during three hydrophobicity. Thus for instance, an attempt to attribute runoff years of field measurements albeit the fact that the NIM crusts generation to hydrophobicity was also made for NRS (Felde et had substantially higher chlorophyll content and was subjected al., 2014; Keck et al., 2013). However, further measurements in to substantially higher rain intensities (Kidron and Büdel, NRS by the same group of scholars did not show hydrophobi- 2014). city (Mugnai et al., 2018), and the "hydrophobicity hypothesis" Figure 1 shows a comparison between two interdunal types was not further advanced (Keck et al., 2016). of crusts from Nizzana and one interdunal crust from Nizzanim. I may add that although theoretically runoff due to hydro- No runoff was generated from the NIM crust following sprin- phobicity may be followed by HOF (triggered by the intermit- kling (with 22.5 mm/h for 15 min). The Nizzana crusts (NIZa, tent character and high intensity fluctuation of the rain; Lázaro NIZb) yielded however runoff (Fig. 1a). While exhibiting sub- et al., 2001; Kidron, 2011), no distinction between both mecha- stantially higher thickness and chlorophyll content (Fig. 1b, c), nisms was yet reported, and more importantly, no meter-scale the NIM crust showed however lower water-holding capacity runoff yield that stems from hydrophobicity, was yet reported. (WHC) (Fig. 1d), lower compressive strength (Fig. 1e), lower One may thus assume that even if taking place, the hydrophobic rigidity (Fig. 1f) and a lower ratio between total carbohydrates effect on runoff in these sites is marginal. and chlorophyll (Fig. 1g). Notwithstanding is the ratio of car- Additionally, even when specific hydrophobic constituents bohydrates to chlorophyll, which showed a close link with within the EPS were identified by various scholars in different runoff coefficient and pointed to the apparent important role biocrusts, hydrophobicity was not necessarily detected. Thus played by the EPS in runoff generation. This was further veri- for instance, although fucose and rhamnose are considered fied by the properties of the EPS, such as the higher rigidity hydrophobic (Mugnai et al., 2018), no hydrophobicity was that characterized the NRS biocrusts, which may exert high detected in Scytonema sp. albeit the fact that both of these integrity to the crust. Clear differences were also noted in SEM sugars were present in relatively high amounts in the EPS of pictographs. Thus for instance, while mainly TB-EPS charac- this species (Chamizo et al., 2019). Similarly, although contain- terized the NIM biocrusts (Fig. 2a), abundant LB-EPS charac- ing rhamnose, no hydrophobicity was found in Schizothrix sp. terize the NRS biocrusts, (Fig. 2b). One may conclude that (Mugnai et al., 2018). while the ratio of carbohydrates to chlorophyll may serve as a basic indication for the total amount of EPS, which may serve 2.3 Partial surface pore clogging in turn as a useful crude estimation for the possible dominance of the EPS, a full exploration of the EPS role in runoff genera- A close link between partial surface pore clogging (PSPC) tion also requires the study of the properties of the EPS. and EPS and between PSPC and runoff was long ago reported (Kidron and Yair, 1997; Mazor et al., 1996; Verrecchia et al., 1995). Not only that a close link was found between rain inten- 3 SYNTHESIS sity and runoff, but the lack of runoff on dry crusts during the beginning of rain events even when subjected to high-intensity Attempts to link between the different constituents that make rains was attributed to the necessary delay that stems from the up the biocrust EPS and the hydrological role of the biocrusts time duration required to allow for water imbibitions by the had only limited success. On the one hand, scholars tried to crust, which will result in turn in PSPC (Kidron and Yair, identify constituents with hydrophobic characteristics such as 362 The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review 15 a NIZa NIZb NIM NIZa NIZb NIM NIZa NIZb NIM NIZa NIZb NIM NIZa NIZb NIM 10 400 NIZa NIZb NIM NIZa NIZb NIM Crust Fig. 1. A comparison between two interdunal crust types taken from Nizzana (NIZ) and were shown to readily generate runoff under field conditions and one from the Nizzanim dune field (NIM) that failed to produce runoff under field conditions. The figure shows runoff coef- ficient following sprinkling experiments (a), the thickness (b), chlorophyll content (c), water holding capacity (d), compressive strength (e), rigidity (f) and the ratio of total carbohydrates (CRB) to chlorophyll (CHL) (g). Modified from Kidron et al. (2020). fucose and rhamnose and yet, even when they occupy a fairly which hydrophobicity is vanished also brings into question the high proportion of the total EPS, hydrophobicity was not al- attempts to link between hydrophobic constituents and biocrust ways detected. Moreover, given the fact that hydrophobicity hydrophobicity. Thus for instance, while sulfated groups and may vanish within minutes given that sufficient amount of uronic acids are hydrophilic (Rossi and De Philippis, 2016), water is supplied to the soil, the hypothesis regarding the tran- their presence cannot fully explain water absorption by the sient nature of hydrophobicity during which polar and non- crust. For example, while young cyanobacterial crusts were polar ends of the EPS molecules switch their position is sup- found to only posses low amounts of uronic acids (Mugnai et ported, making the link between hydrophobicity and certain al., 2020b), young cyanobacterial crusts were still observed to types of sugars less likely. Furthermore, the rapidity during readily absorb water during a sprinkling experiment, and WHC (%) Thickness (mm) Rigidity (Pa^10 ) Runoff Coefficient (%) Chlorophyll (mg/m ) Ratio CRB/CHL Strength (g/cm ) Giora J. Kidron 10µ 10µ Fig. 2. SEM pictographs showing the Nizzanim (NIM) (a) and the Nizzana (NIZ) (b) crusts. Whereas LB-EPS is hardly noted in NIM it abounds in NIZ. subsequently to generate runoff (Kidron, 2015). Nevertheless, it order decrease in the micropores volume. Subsequently, I is believed that water absorbance may vary in accordance with would like to suggest that the relative amount of WHC may the EPS properties (Chenu, 1993). therefore serve as a possible indicator for the crust potentiality When the water-holding capacity (WHC) of the cyanobacte- to generate runoff. The higher the amount of WHC, the higher rial crusts from NRS was compared to cyanobacteria-algae is the amount of water occupying the pores, and the higher the crusts from NIM, substantially higher WHC characterize the probability that the water-filled pores are efficiently clogged. NRS crusts. Interestingly, the NRS crusts were also character- This may be also facilitated by the high rigidity of the crust that ized by abundant LB-EPS (Fig. 2b). I would like to suggest that will resist the rain drop impact and possible infiltration through LB-EPS may play a cardinal role in water absorption and hence the crust openings. With the impediment of infiltration, rain, in PSPC. Contrary to TB-EPS which is limited by physiological which will exceed a certain rate of input, will run off the sur- constraints, and therefore has distinct thickness (Rossi and De face. Philippis, 2015), LB-EPS commonly occupies large pore vol- With water addition, the biocrust readily reaches saturation ume (Nicolaus et al., 1999), and as such may absorb exception- leading in turn to infiltration-excess (Hortonian) overland flow ally large amounts of water. (HOF). Unlike the case of hydrophobicity during which water In this regard, it is suggested that rather than TB-EPS, which repellency takes place and runoff results from the incapability was considered to play major role in crust hydrology (De of the water to infiltrate the soil, runoff following pore clogging Philippis, 2015), LB-EPS may play the central role in runoff depends upon the capability of the water to readily saturate the generation. Occupying a much larger pore volume, LB-EPS upper soil surface skin. Runoff will not begin instantly as in the may principally determine the WHC of the crust, as clearly case of hydrophobicity, but only following several minutes or shown in the SEM pictographs of the NRS crusts. High WHC more during which water absorption by the biocrust-induced implies high degree of swelling (Chenu, 1993; Or et al., 2007) EPS will suffice to partially clog the pores (Verrecchia et al., and subsequently efficient pore clogging and infiltration imped- 1995). iment. For instance, according to Chenu (1993), addition of During the current review, an attempt was made to link be- EPS to kaolinite and montmorillonite decreased the pore diame- tween the crust properties and above all, the biocrust-induced ter in high water potentials from 0.5–4 μ to an average of 0.2 μ. EPS and the hydrological mechanisms responsible for runoff According to Verrecchia et al (1995), within <30 min of generation in arid and semiarid regions. While under similar wetting, 8–12-fold decrease in the volume of the biocrust mi- environmental conditions the amount of EPS may serve as a cropores took place. Both groups of scholars report on one- crude indicator for the crust capability to partially clog the 364 The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review surface pores (Kidron et al., 2003), for a more complete and semiarid ecosystem: A complex balance between biological reliable outcome, evaluating the EPS properties is of major soil crust features and rainfall characteristics. J. Hydrol., importance (Chenu, 1993; Fick et al., 2019; Kidron et al., 452–453, 130–138. 2020). It follows that among the important functions carried out Chamizo, S., Belnap, J., Eldridge, D.J., Cantón, Y., Malam- by the EPS, EPS may play an important role in runoff genera- Issa, O., 2016. The role of biocrusts in arid land hydrology. tion, as in the case of NRS, which may therefore substantially In: Weber, B., Büdel. B., Belnap. J. (Eds.): Biological Soil impact the hydrology, geomorphology, pedology and ecology Crusts: An Organizing Principle in Dryland. Ecological of arid and semiarid ecosystems. Studies 226. Springer, Switzerland, pp. 321–346. Currently, although occasional hydrophobicity was reported Chamizo, S., Adessi, A., Mugnai, G., Simiani, A., De Philippis, from arid and especially semiarid zones, there are no convinc- R., 2019. Soil type and cyanobacteria species influence the ing data that link between EPS-induced hydrophobicity to macromolecular and chemical characteristics of the polysac- meter-scale runoff generation in arid and semiarid regions. The charide matrix in induced biocrusts. Microbial Ecol., 78, occurrence of both mechanisms is theoretically feasible, as 482–493. DOI: 10.1007/s00248-018-1305-y reported during lab measurements with biocrusts that were Chen, L.Z., Wang, G.H., Hong, S., Liu, A., Li, C., Liu, Y.D., induced to develop hydrophobicity, during which two separated 2009. UV-B-induced oxidative damage and protective role runoff peaks (with a ~5 min interval) were recorded during of exopolysaccharides in desert cyanobacterium Microcoleus continuous sprinkling: following hydrophobicity and following vaginatus. J. Integrat. Plant Biol., 51, 2, 194–200. DOI: pore clogging (Kidron et al., 1999). This was not yet shown 10.1111/j.1744-7909.2008.00784.x under field conditions, and unlike PSPC, hydrophobicity was Chen, Y., Tarchitzky, J., Brouwer, J. Morin, J., Banin, A., not yet shown to play an important role in runoff generation in 1980. Scanning electron microscope observations in soil arid and semiarid zones. In this regard it is useful to refer to crusts and their formation. Soil Sci., 130, 49–55. William of Occam: "Entia non sunt multiplicanda praeter ne- Chenu, C., 1993. Clay-or sand- polysaccharide associations as cessitate", i.e., "Entities should not be multiplied more than models for the interface between micro-organisms and soil: necessary". water related properties and microstructure. Geoderma, 56, 143–156. REFERENCES Colica, G., Li, H., Rossi, F., Li, D., Liu, Y., De Philippis, R., 2014. Microbial secreted exopolysaccharides affect the hy- Belnap, J., 2006. The potential roles of biological soil crusts in drological behavior of induced biological soil crusts in de- dryland hydrologic cycles. Hydrol. Process., 20, 3159–3178. sert sandy soils. Soil Biol. Biochem., 68, 62–70. Beven, K.J., Kirkby, M.J., 1979. A physically based, variable De Brouwer, J.F.C., Stal, L.J., 2001. Short-term dynamics in contributing area model of basin hydrology. Hydrol. Sci. microphytobenthos distribution and associated extracellular Bull., 24, 43–69. DOI: 10.1080/02626667909491834 carbohydrates in surface sediments of the intertidal mudflat. Beysens, D., 2018. Dew Water. River Publishers, Gistrup, Marine Ecol. Progress Series, 218, 33–44. Denmark. de Jong, S.M., Addink, E.A., Van Beek, L.P.H., Duijsings, D., Blackburn, W.H., 1975. Factors influencing infiltration and sed- 2011. Physical characterization, spectral response and re- iment production of semiarid rangelands in Nevada. Water motely sensed mapping of Mediterranean soil surface crusts. Resour. Res., 6, 929–937. DOI: 10.1029/WR011i006p00929 Catena, 86, 24–35. Brotherson, J.D., Rushforth, S.R., 1983. Influence of crypto- Dekker, L.W., Ritsema, C.J., 1994. How water moves in a gamic crusts on moisture relationships of soils in Navajo water repellent sandy soil. 1. Potential and actual water re- National Monument, Arizona. Great Basin Natur., 43, pellency. Water Resour. Res., 30, 2507–2517. 73–78. Dekker, L.W., Ritsema, C.J., 2000. Wetting patterns and mois- Brüll, L.P., Huang, Z., Thomas-Oates, J.E., Paulsen, B.S., Co- ture variability in water repellent Dutch soils. J. Hydrol., hen, E.H., Michaelsen, T.E., 2000. Studies of polysaccha- 231–232, 148–164. rides from three edible species of Nostoc (cyanobacteria) De Philippis, R., 2015. The stability and the hydrological be- with different colony morphologies: Structural characteriza- havior of biological soil crusts is significantly affected by tion and effect on the complement system of polysaccharides the complex nature of their polysaccharide matrix. EGU from Nostoc commune. J. Phycol., 36, 871–881. General Assembly, 12–17 April, 2015, Vienna, Austria. ID: Cammeraat, E.L.H., 2004. Scale dependent thresholds in hydro- 3513. logical and erosion response of a semi-arid catchment in Demig, J.W., Young, J.N., 2017. The role of exopolysaccha- southeast Spain. Agric. Ecosys. Environ., 104, 317–332. rides in microbial adaptation to cold habitats. In: Margesin, DOI: 10.1016/j.agee.2004.01.032 R. (Ed.): Psychrophiles: From Biodiversity to Biotechnolo- Campbell, S.E., 1979. Soil stabilization by prokaryotic desert gy. Springer Inter Pub. AG. DOI: 10.1007/978-3=319- crusts: Implications for Precambrian land biota. Orig. Life, 57057-0-0122. 9, 335–348. Doerr, S.H., Shakesby, R.A., Dekker, L.W., Ritsema, C.J., Cantón, Y., Chamizo, S., Rodríguez-Caballero, E., Lazáro, R., 2006. Occurrence, prediction and hydrological effects of wa- Roncero-Ramos, B., Roman, J.R., Solé-Benet, A., 2020. ter repellency amongst major soil and land-use types in a Water regulation in cyanobacterial biocrusts from drylands: humid temperate climate. Eur. J. Soil Sci., 57, 741–754. Negative impacts of anthropogenic disturbance. Water, 12, Drahorad, S., Steckenmesser, D., Felix-Henningsen, P., Lich- 720. https://doi.org/10.3390/w12030720 ner, L., Rodny, M., 2013. Ongoing succession of biological Chamizo, S., Cantón, Y., Lázaro, R., Domingo, F., 2013. The soil crusts increases water repellency – a case study on role of biological soil crusts in soil moisture dynamics in Arenosols in Sekule, Slovakia. Biologia, 68, 1089–1093. two semiarid ecosystems with contrasting soil textures. J. Dunkerley, D., 2000. Hydrological effects of dryland shrubs: Hydrol., 489, 74–84. defining the spatial extent of modified soil water uptake Chamizo, S., Cantón, Y., Rodríguez-Caballero, E., Domingo, rates at an Australian desert site. J. Arid Environ., 45, 159– F., Escudero, A., 2012. Runoff of contrasting scales in a 172. DOI: 10.1006/jare.2000.0636 365 Giora J. Kidron Dunne, T., 1990. Hydrology, mechanics, and geomorphic im- crust in a revegetated area of the Tengger Desert, Northern plications of erosion by subsurface flow. In: Higgins, C.G., China. J. Hydrol., 519, 2341–2349. Coates, D.R. (Eds.): Groundwater Geomorphology: The Jungerius, D., van der Meulen, F., 1988. Erosion processes in a Role of Subsurface Water in Earth-Surface Processes and dune landscape along the Dutch coast. Catena, 15, 217–228. Landforms. Geological Society of America, Special Paper Jungerius, P.D., de Jong, J.H., 1989. Variability of water repel- 252, pp. 1–28. lence in the dunes along the Dutch coast. Catena, 16, 491– Dunne, T., Black, R.D., 1970. An experimental investigation of 497. runoff production in permeable soils. Water Resour. Res., 6, Kato, H., Onda, Y., Tanaka, Y., Asano, M., 2009. Field meas- 478–490. DOI: 10.1029/WR006i002p00478 urement of infiltration rate using an oscillating nozzle rain- Ehling-Schulz, M., Schere, S., 1999. UV protection in cyano- fall simulator in the cold, semiarid grassland of Mongolia. bacteria. Eur. J. Phycol., 34, 329–338. Catena, 76, 173–181. DOI: 10.1016/j.catena.2008.11.003 Epstein, E., Grant, W.J., 1993. Soil crust formation as affected Keck, H., Felde, V.J.M.N.L., Drahorad, S.L., Felix- by raindrop impact. In: Hadas, A., Swartzendruber, D., Rit- Henningsen, P., 2013. Effects of biological soil crusts on jema, P.E., Fuchs, M., Yaron, B. (Eds.): Physical Aspects of water repellency in a sand dune ecosystem of the NW Soil Water and Salts in Ecosystems. Springer, Berlin and Negev, Israel. Second Intgernational Workshop on th th Heidelberg, pp. 195–201. Biological Soil Crusts, Madrid, 10 –13 June, 2013. Felde, V.J.M.N.L., Peth, S., Uteau-Puschmann, D., Drahorad, Keck, H., Felde, V.J.M.N.L., Drahorad, S.L., Felix-Hennigsen, S., Felix-Henningsen, P., 2014. Soil microstructure as an P., 2016. Biological soil crusts cause subcritical water repel- under-explored feature of biological soil crust hydrological lency in a sand dune ecosystem located along a rainfall gra- properties: case study from the NW Negev Desert. Bio- dient in the NW Negev Desert, Israel. J. Hydrol. Hydro- divers. Conserv., 23, 1687–1708. mech., 64, 133–140. Fick, S.E., Barger, N.N., Duniway, M.C., 2019. Hydrological Kidron, G.J., 1999. Differential water distribution over dune function of rapidly induced biocrusts. Ecohydrology, 12, slopes as affected by slope position and microbiotic crust, e2089. DOI: 10.1002/eco.2089 Negev Desert, Israel. Hydrol. Process., 13, 1665–1682. DOI: Fischer, T., Veste, M., Wiehe, W., Lange, P., 2010. Water 10.1002/(SICI)1099-1085(19990815) repellency and pore clogging at early successional stages of Kidron G.J., 2011. Runoff generation and sediment yield on microbiotic crusts on inland dunes, Brandenburg, NE Ger- homogeneous dune slopes: scale effect and implications for many. Catena, 80, 47–52. DOI: 10.1016/j.catena.2009.08.009 analysis. Earth Surf. Process. Landf., 36, 1809–1824. DOI: Fischer, T., Veste, M., Bens, O., Hüttl, R.F., 2012. Dew 10.1002/esp.2203 formation on the surface of biological soil crusts in central Kidron, G.J., 2015. The role of crust thickness in runoff genera- European sand ecosystems. Biogeosciences, 9, 4621–4628. tion from microbiotic crusts. Hydrol. Process., 29, 1783– Fischer, T., Yair, A., Veste, M., Geppet, H., 2013. Hydraulic 1792. DOI: 10.1002/hyp.10243 properties of biological soil crusts on sand dunes studied by Kidron, G.J., 2021. Comparing overland flow processes be- C-CP/MAS-NMR: A comparison between an arid and tween semiarid and humid regions: Does saturation overland temperate site. Catena, 110, 155–160. flow take place in semiarid regions? J. Hydrol., 593, 125624. Fox, D.M., Bryan, R.B., Price, A.G., 2004. The role of soil DOI: 10.1016/j.jhydrol.2020.125624 surface crusting in desertification and strategies to reduce Kidron, G.J., Büdel, B., 2014. Contrasting hydrological re- crusting. Environ. Monitor. Assess., 99, 149–159. sponse of coastal and desert biocrusts. Hydrol. Process., 28, Francis, M.L., Fey, M.V., Prinsloo, H.P., Ellis, F., Mills, A.J., 361–371. DOI: 10.1002/hyp.9587 Medinski, T.V., 2007. Soils of Namaqualand: Compensa- Kidron, G.J., Kronenfeld, R., 2020a. Assessing the likelihood tions for aridity. J. Arid Environ., 70, 588–603. of the soil surface to condense vapor: The Negev experience. Galle, S., Arendt, E.K., 2014. Exopolysaccharides from sour- Ecohydrology, 13, e2200. DOI: 10.1002/eco.2200 dough lactic acid bacteria. Critical Rev. Food Sci. Nutr., 54, Kidron, G.J., Kronenfeld, R., 2020b. Atmospheric humidity is 891–901. DOI: 10.1080/10408398.2011.617474 unlikely to serve as an important water source for crustose Hagemann, M., Henneberg, M., Felde, V.J.M.N.L., Drahorad, soil lichens in the Tabernas Desert. J. Hydrol. Hydromech., S.L., Berkowicz, S.M., Felix-Henningsen, P. Kaplan, A., 68, 359–367. DOI: 10.2478/johh-2020-0034 2015. Cyanobacterial diversity in biological soil crusts along Kidron, G.J., Starinsky, A., 2019. Measurements and ecological a precipitation gradient, Northwest Negev Desert, Israel. implications of non-rainfall water in desert ecosystems – A Microbiol. Ecol., 70, 219–230. review. Ecohydrology, 12, e2121. DOI: 10.1002/eco.2121 Hallett, P.D., 2008. A brief overview of the causes, impacts and Kidron, G.J., Tal, S.Y., 2012. The effect of biocrusts on evapo- melioration of soil water repellency – a review. Soil Water ration from sand dunes in the Negev Desert. Geoderma, 179- Res., 3, S21–S29. 180, 104–112. DOI: 10.1016/j.geoderma.2012.02.021 Harper, K.T., Marble, J.R., 1988. A role for nonvascular plants Kidron, G.J., Yair, A., 1997. Rainfall-runoff relationships over in management of arid and semiarid rangelands. In: Tuller, encrusted dune surfaces, Nizzana, Western Negev, Israel. P.T. (Ed.): Applications of Plant Sciences to Rangeland Earth Surf. Process. Landf., 22, 1169–1184. DOI: Management and Inventory. Kluwer, Amsterdam, pp. 135– 10.1002/esp.1532 169. Kidron, G.J., Yaalon, D.H., Vonshak, A., 1999. Two causes for Heil, J.W., Juo, A.S.R., McInnes, K.J., 1997. Soil properties runoff initiation on microbiotic crusts: hydrophobicity and influencing surface sealing of some sandy soils in the Sahel. pore clogging. Soil Sci. 164, 18–27. Soil Sci., 162, 459–469. Kidron, G.J., Herrnstadt, I., Barzilay, E., 2002. The role of dew Horton, R.E., 1933. The role of infiltration in the hydrological as a moisture source for sand microbiotic crusts in the Negev cycle. EOS Transactions AGU, 14, 446–460. DOI: Desert, Israel. J. Arid Environ., 52, 517–533. DOI: 10.1029/TR014;001p00446 10.1016/jare.2002.1014 Jia, R.L., Li, X.R., Liu, L.C., Pan, Y.X., Gao, Y.H., Wei, Y.P., Kidron, G.J., Wang, Y., Herzberg, M., 2020. 2014. Effects of sand burial on dew deposition on moss soil Exopolysaccharides may increase biocrust rigidity and 366 The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review induce runoff generation. J. Hydrol., 588, 125081. DOI: R.Y., 2014. Extracellular polymeric substances of bacteria 10.1016/J.JHYDROL.2020.125081 and their potential environmental applications. J. Environ. Kidron, G.J., Yair, A., Vonshak, A., Abeliovich A., 2003. Mi- Manage., 144, 1–25. DOI: 10.1016/j.jenvman.2014.05.010. crobiotic crust control of runoff generation on sand dunes in Mugnai, G., Rossi, F., Chamizo, S., Adessi, A., De Philippis, the Negev Desert. Water Resour. Res., 39, 1108. DOI: R., 2020a. The role of grain size and inoculums amount of 10.1029/2002WR001561.2003 biocrust formation by Leptolyngbya ohadii. Catena, 184, Lange, O.L., Schulze, E.D., Koch, W., 1970. Ecophysiological 104248. DOI: 10.1016/j.catena.2019.104248 investigations on lichens of the Negev Desert, III: CO2 gas Mugnai, G., Rossi, F., Mascalchi, C., Ventura, S., De Philippis, exchange and water metabolism of crustose and foliose li- R., 2020b. High arctic biocrusts: characterization of the ex- chens in their natural habitat during the summer dry period. opolysaccharidic matrix. Polar Biol., 43, 1805–1815. DOI: Flora, 159, 525–538. 10.1007/s00300-020-02746-8 Lange, O.L., Belnap, J., Reichenberger, H., 1998. Photosynthe- Mugnai, G., Rossi, F., Felde, V.J.M.N.L., Colesie, C., Büdel, sis of the cyanobacterial soil-crust lichen Collema tenax B., Peth, S., Kaplan, A., De Philippis, R., 2018. Develop- from arid lands in southern Utah, USA: role of water content ment of the polysaccharide matrix in biocrusts induced by a on light and temperature response of CO exchange. Func. cyanobacterium inoculated in sand microcosms. Biol. Fert. Ecol., 12, 195–202. Soils, 54, 27–40. Lange, O.L., Kidron, G.J., Büdel, B., Meyer, A., Kilian, E., Nagar, S., Antony, R., Thamban, M., 2021. Extracellular poly- Abeliovitch, A., 1992. Taxonomic composition and photo- meric substances in Antarctic environments: A review of synthetic characteristics of the biological soil crusts covering their ecological roles and impact on glacier biogeochemical sand dunes in the Western Negev Desert. Func. Ecol., 6, cycles. Polar Sci. DOI: 10.1016/j.polar.2021.100686 519–527. Nicolaus, B., Panico, A., Lama, L., Romano, I., Manca, M.C., Lázaro, R., Rodrigo, F.S., Gutiérrez, L., Domingo, F., De Giulio, A., Gambacorta, A., 1999. Chemical composition Puigdegabregas, J., 2001. Analysis of 30-year rainfall record and production of exopolysaccharides from representative (1967-1997) in semi-arid SE Spain for implications on vege- members of heterocystous and non-heterocystous cyanobac- tation. J. Arid Environ., 48, 373–395. teria. Phytochemistry, 52, 639–647. Li, S., Xiao, B., Sun F., Kidron, G.J., 2021. Moss-dominated Onofiok, O., Singer, M.J., 1984. Scanning electron microscope biocrusts greatly enhance water vapor sorption capacity and studies of surface crusts formed by simulated rainfall. Soil increase non-rainfall water deposition in drylands. Geoder- Sci. Soc. Am. J., 48, 1137–1143. ma, 388, 114930. DOI: 10.1016/j.geoderma.2021.114930 Oostindie, K., Dekker, L.W., Wesseling, J.G., Ritsema, C.J., Lichner, L., Hallett, P.D., Orfánus, T., Czachor, H., Rajkai, K., Geissen, V., 2013. Development of actual water repellency Šir, M., Tesař, M., 2010. Vegetation impact on the hydrolo- in a grass-covered dune sand during dehydration experiment. gy of an aeolian sandy soil in a continental climate. Ecohy- Geoderma, 204–205, 23–30. drology, 3, 413–420. Or, D., Smets, B.F., Wraith, J.M., Dechesne, A., Friedman, Lichner, L., Holko, L., Zhukova, N., Shacht, K., Rajkai, K., S.P., 2007. Physical constraints affecting bacterial habitats Fodor, N., Sándor, R., 2012. Plants and biological soil crust and activity in unsaturated porous media – a review. Adv. influence the hydrophysical parameters and water flow in an Water Resour., 30, 1505–1527. aeolian sandy soil. J. Hydrol. Hydromech., 60, 309–318. Otero, A., Vincenzini, M., 2003. Extracellular polysaccharide Lichner, L., Hallett, P.D., Drongova, Z., Czachor, H., Kovacik, synthesis by Nostoc strains as affected by N source and light L., Mataix-Solera, J., Homolák, M., 2013. Algae influence intensity. J. Biotechnol., 102, 143–152. the hydrophysical parameters of a sand soil. Catena, 108, Pagliai, M., Bisdom, E.B.A., Ledin, S., 1983. Changes in sur- 58–68. face structure (crusting) after application of sewage sludge Lichner, L., Felde, V.J.M.N.L., Büdel, B., Leue, M., Gerke, and pig slurry to cultivated agricultural soils in northern Ita- H.H., Ellerbrock, R.H., Kollár, J., Rodny, M., Šurda, P., ly. Geoderma, 30, 35–53. Fodor, N., Sándor, R., 2018. Effect of vegetation and its suc- Pereira, S., Zille, A., Micheletti, E., Moradas-Ferreira, P., De cession on water repellency in sandy soils. Ecohydrology, Philippis, R., Tamagnini, P., 2009. Complexity of cyanobac- 11, e1991. DOI: 10.1002/eco.1991 terial exopolysaccharides: composition, structures, inducing Mager, D.M., Thomas, A.D., 2011. Extracellular polysaccha- factors and putative genes involved in their biosynthesis and rides from cyanobacterial soil crusts: A review of their role assembly. FEMS Microbiol. Rev., 33, 917–941. in dryland soil processes. J. Arid Environ., 75, 91–97. Pringault, O., Garcia-Pichel, F., 2004. Hydrotaxis of cyanobac- Malam-Issa, O., Défarge, C., Trichet, J., Valentin, C., Rajot, teria in desert crusts. Microb. Ecol., 47, 366–373. J.L., 2009. Microbiotic soil crusts in the Sahel of western Redmile-Gordon, M., Gregory, A.S., White, R.P., Watts, C.W., Niger and their influence on soil porosity and water dynam- 2020. Soil organic carbon, extracellular polymeric substanc- ics. Catena, 77, 48–55. es (EPS), and soil structural stability as affected by previous Mayor, A.G., Bautista, S., Bellot, J., 2009. Factors and interac- and current land-use. Geoderma, 363. 114143. DOI: tions controlling infiltration, runoff, and soil loss at the mi- 10.1016/j.geoderma.2019.114143 croscale in a patchy Mediterranean semiarid landscape. Rodriguez-Caballero, E., Cantón, Y., Chamizo, S., Lázaro, R., Earth Surf. Process. Landf., 34, 1702–1711. DOI: Escudero, A., 2013. Soil loss and runoff in semiarid ecosys- 10.1002/esp.1875 tems: A complex interaction between biological soil crusts, Mazor, G., Kidron, G.J., Vonshak, A., Abeliovich, A., 1996. micro-topography, and hydrological drivers. Ecosystems, 16, The role of cyanobacterial exopolysaccharides in structuring 529–546. desert microbial crusts. FEMS Microbiol. Ecol., 21, 121– Rodriguez-Caballero, E., Belnap, J., Büdel, B., Crutzen, P.J., 130. DOI: 10.1111/j.1574-6941.1996.tb00339.x Andreae, M.O., Pöschl, U., Weber, B., 2018. Dryland photo- McIntyre, D.S., 1958. Soil splash and the formation of surface autotrophic soil surface communities endangered by global crusts by raindrop impact. Soil Sci., 85, 261–266. change. Nat. Geosci., 11, 185–189. DOI: 10.1038/s41561- More, T.T., Yadav, J.S.S., Yan, S., Tyagi, R.D., Surampalli, 018-0072-1 367 Giora J. Kidron Rossi, F., De Philippis, R., 2015. Role of cyanobacterial exopol- Verrecchia, E., Yair, A., Kidron, G.J., Verrecchia, K., 1995. ysccharides in phototrophic biofilms and in complex micro- Physical properties of the psammophile cryptogamic crust bial mats. Life, 5, 1218–1238. DOI: 10.3390/life5021218 and their consequences to the water regime of sandy soils, Rossi, F., De Philippis, R., 2016. Excocellular polysaccharides Northwestern Negev Desert, Israel. J. Arid Environ., 29, in microalgae and cyanobacteria: Chemical features, role 427–437. DOI: 10.1016/S0140-1963(95)80015-8 and enzymes and genes involved in their biosynthesis. In: Veste, M., Littmann, T., Friedrich, H., Breckle, S.-W., 2001. Borowitzka, M.A., Beardall, J., Raven, J.A. (Eds.): The Microclimatic boundary conditions for activity of soil lichen Physiology of Microalgae. Developments in Applied Phy- crusts in sand dunes of the north-western Negev desert, Isra- cology, Springer, Switzerland. pp. 565–590. DOI: el. Flora, 196, 465–474. 10.1007/978-3-319-24945-2_21 Wilske, B., Burgheimer, J., Karnieli, A., Zaady, E., Andreae, Rossi, F., Mugnai, G., De Philippis, R., 2018. Complex role of M.O., Yakir, D., Kesselmeir, J., 2008. The CO exchange of the polymeric matrix in biological soil crusts. Plant Soil, biological soil crusts in a semiarid grass-shrubland at the 429, 19–34. DOI: 10.1007/s11104-017-3441-4 northern transition zone of the Negev Desert, Israel. Bioge- Rossi, F., Potrafka, R.M., Garcia-Pichel, F., De Philippis, R., osci. Discuss., 5, 1969–2001. 2012. The role of exopolysaccharides in enhancing hydraulic Wood, M.K., Blackburn, W.H., 1981. Grazing systems: Their conductivity of biological soil crusts. Soil Biol. Biochem., influence on infiltration rates in the rolling plains of Texas. 46, 33–40. J. Range Manage., 34, 331–335. Rutin, J., 1983. Erosional processes on a coastal sand dune, De Xiao, B., Sun, F., Hu, K., Kidron, G.J., 2019a. Biocrusts reduce Blink, Noordwijkerhout. Publication 35 of the Physical Ge- surface soil infiltrability and impede soil water infiltration ography and Soils Laboratory, University of Amsterdam, under tension and ponding conditions in dryland ecosystem. Amsterdam. J. Hydrol., 568, 792–802. DOI: 10.1016/j.jhydrol.2018.11.51 Sun, F., Xiao, B., Li S., Kidron, G.J., 2021. Towards moss Xiao, B, Sun, F., Yao, X., Hu, K., Kidron, G.J., 2019b. Season- biocrust effects on surface soil water holding capacity: Soil al variations in infiltrability of moss-dominated biocrusts on water retention curve analysis and modeling. Geoderma, aeolian sand and loess soil in the Chinese Loess Plateau. 399, 115120. DOI: 10.1016/j.geoderma.2021.115120 Hydrol. Process., 33, 2449–2463. DOI: 10.1002/hyp.13484 Talbot, M.R., Williams, M.A.J., 1978. Erosion of fixed dunes Xu, C.-Y., Singh, V.P., 2001. Evaluation and generalization of in the Sahel, central Niger. Earth Surf. Process. Landf., 3, temperature-based methods for calculating evaporation. 107–113. Hydrol. Process., 15, 205–319. DOI: 10.1002/hyp.119 Tarchitzky, J., Banin, A., Morin, J., Chen, Y., 1984. Nature, formation and effects of soil crusts formed by water drop Received 24 June 2021 impact. Geoderma, 33, 135–155. Accepted 27 August 2021 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Hydrology and Hydromechanics de Gruyter

The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review

Journal of Hydrology and Hydromechanics , Volume 69 (4): 9 – Dec 1, 2021

Loading next page...
 
/lp/de-gruyter/the-role-of-biocrust-induced-exopolymeric-matrix-in-runoff-generation-ifUFE9RTUS
Publisher
de Gruyter
Copyright
© 2021 Giora J. Kidron, published by Sciendo
ISSN
0042-790X
eISSN
1338-4333
DOI
10.2478/johh-2021-0028
Publisher site
See Article on Publisher Site

Abstract

J. Hydrol. Hydromech., 69, 2021, 4, 360–368 ©2021. This is an open access article distributed DOI: 10.2478/johh-2021-0028 under the Creative Commons Attribution ISSN 1338-4333 NonCommercial-NoDerivatives 4.0 License The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review Giora J. Kidron Institute of Earth Sciences, The Hebrew University of Jerusalem, Givat Ram Campus, Jerusalem 91904, Israel. Tel: +972-54-4967-271. Fax: 972-2-566-2581. E-mail: kidron@mail.huji.ac.il Abstract: Although playing an important role in shaping the environment, the mechanisms responsible for runoff initia- tion and yield in arid and semiarid regions are not yet fully explored. With infiltration-excess overland flow, known also as Hortonian overland flow (HOF) taking place in these areas, the uppermost surface 'skin' plays a cardinal role in runoff initiation and yield. Over large areas, this skin is composed of biocrusts, a variety of autotrophs (principally cyanobacte- ria, green algae, lichens, mosses) accompanied by heterotrophs (such as fungi, bacteria, archaea), which may largely dictate the infiltration capability of the surface. With most biocrust organisms being capable of excreting extracellular polymeric substances (EPS or exopolymers), and growing evidence pointing to the capability of certain EPS to partially seal the surface, EPS may play a cardinal role in hindering infiltration and triggering HOF. Yet, despite this logic thread, great controversy still exists regarding the main mechanisms responsible for runoff generation (runoff initiation and yield). Elucidation of the possible role played by EPS in runoff generation is the focus of the current review. Keywords: Biological soil crusts; Extracellular polymeric substances; Pore clogging; Hydrophobicity; Infiltration-excess overland flow; Water repellency. 1 INTRODUCTION subsequently published (Fischer et al., 2010; Kidron and Yair, 1997; Lichner et al., 2012). The research also focused on the Mainly attributed to the low vegetal cover, high-magnitude EPS properties. runoff events and occasional hazardous floods commonly take Research aiming to elucidate the different constituents of bi- place in arid and semiarid regions. In contrast to humid areas ocrust-induced EPS and the possible roles played by the EPS is where runoff takes place once a large volume of soil reaches indeed not uncommon. Excreted by microorganisms and micro- saturation, known therefore as saturation excess overland flow flora (cyanobacteria, archaea, bacteria, fungi, diatoms, green (SOF) (Beven and Kirkby, 1979; Dunne, 1990; Dunne and algae, lichens, but not by mosses) of the biocrusts, EPS is be- Black, 1970), runoff in arid and semiarid regions takes place lieved to protect and to assist the cell against possible stress and even when almost the entire soil profile is dry. Runoff takes danger, and to accomplish some physiological needs. EPS place due to infiltration-excess overland flow, known also as facilitate cell adhesion and cohesion (Galle and Arendt, 2014; Hortonian overland flow (HOF), during which only the upper- Rossi et al., 2018), filament gliding and therefore motility most soil skin reaches saturation, thus hindering water infiltra- (Campbell, 1979; Pringault and Garcia-Pichel, 2004), protect- tion into the subsurface, which may therefore remain dry or ing the cell from UV radiation (Rossi et al., 2018), and the relatively dry (Blackburn, 1975; Cammeraat, 2004; Horton, nitrogenase from excess oxygen (Otero and Vincenzini, 2003). 1933). It plays a role in scavenging essential nutrients (Rossi et al., The crust thickness required to impede infiltration is as- 2018), and is believed to scavenge free radicals which other- sumed to be extremely thin, within millimeters. Following the wise may harm the cell (Chen et al., 2009). Among other roles widely-held belief that physical crusts trigger runoff, a possible attributed to EPS is its role to protect the cell from lysis (Eh- link between the thickness of physical crusts and runoff was ling-Schultz and Schere, 1999) and from shifts in the environ- made. According to some scholars it is <1 mm-thick (Epstein mental conditions such as desiccation, salinity, extreme tem- and Grant, 1993; Heil et al., 1997; McIntyre, 1958; Onofiok peratures, pH or exposure to toxic materials (Demig and Young, 2017; Ehling-Schultz and Schere, 1999). The EPS is and Singer, 1984; Pagliai et al., 1983), while according to oth- ers it may be 2–4 mm thick (Chen et al., 1980; de Jong et al., also believed to protect the cell from freezing damage (Nagar et 2011; Tarchitzky et al., 1984), i.e., within the range of thickness al., 2021) and from viral/bacterial infection and predation (Brüll of most biocrusts. et al., 2000). While the above-mentioned roles are widely ac- With biocrusts (biological soil crusts) constituting the upper cepted by the scientific community, this is not the case with the skin of extensive areas in arid and semiarid regions (Rodriguz- possible hydrological role played by the EPS, as reflected in Caballero et al., 2018) and with many of the biocrust microor- recent reviews (Mager and Thomas. 2011; Rossi and De Philip- ganisms being known to excrete exopolymers (extracellular pis, 2015), and the absence of this category in a list of major polymeric substances, EPS), which may affect surface hydrolo- roles played by the EPS most recently published (Rossi et al., gy (Brotherson and Rushforth, 1983; Chamizo et al., 2016; 2018). Kidron et al., 2003; Li et al., 2021; Sun et al., 2021; Xiao et al., It is customary to divide the EPS to tightly bound EPS (TB- 2019a), research on the interrelations between biocrusts and EPS), whether constituting sheaths (around filamentous cells) biocrust-induced EPS and runoff was called for. Papers aiming or capsules (around single cells) and loose bound (released, scattered) EPS (LB-EPS), i.e., slime which has an amorphous to study the possible relationships between these variables were 360 The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review shape, not necessarily related to the shape of the cell (More et which will facilitate aeration and water infiltration (Cantón et al., 2014; Otero and Vincenzini, 2003; Pereira et al., 2009). al., 2020; Or et al., 2007; Redmile-Gordon et al., 2020). Thus While the slime is mostly comprised of low molecular weight for instance EPS shrinkage during desiccation might promote (MW) polysaccharides, the sheaths are complex, mainly char- infiltration through the soil crevices. While these functions acterized by high-MW molecules, and as such are much less were convincingly shown and are not a matter of dispute, some degradable. This may explain the fact that unlike LB-EPS scholars maintain that higher rates of infiltration are induced by which can be extracted by water, the use of Na2EDTA is re- subsurface EPS, especially in developed crusts, which will quired for the extraction of TB-EPS. It was suggested that TB- hinder in turn runoff generation (Belnap, 2006; Brotherson and EPS is responsible for the crust structure (De Philippis, 2015). Rushforth, 1983; Chamizo et al., 2013; Rossi et al., 2012). This The high capability of EPS to absorb high amounts of water conclusion is however very problematic. EPS as well as clay (Chenu, 1993; Or et al., 2007) may have important hydrological tend to absorb water within minutes, resulting in the closure of consequences. For instance, EPS may hinder evaporation and the crevices (Fox et al., 2004). This is especially the case once facilitate longer cell activity (Chenu, 1993). This may be the higher amounts of EPS, which are associated with biocrusts and case for some cyanolichens such as Collema sp. which takes therefore concentrate at the surface, will readily swell upon advantage of the short rain events in deserts to accumulate wetting, blocking easy entry of rainwater to depth. Further- substantial amounts of water, which will facilitate long hours of more, the view that soil aggregation hinders runoff does not photosynthesis, especially during the cool weather that charac- coincide with the prevailing runoff mechanism which takes terize the cool season rains (Lange et al., 1998). On the other place in arid and semiarid regions. Due to limited rain, SOF hand, with some EPS having dark sunscreen pigments (Ehling- does not take place in these areas, and runoff generation takes Schulze and Shere, 1999), the resultant reduction in the albedo place only following HOF (Horton, 1933; Kidron, 2021), which may lead to temperature rise which may increase evaporation implies infiltration impediment only following surface satura- (Harper and Marble, 1988; Kidron and Tal, 2012; Xu and tion regardless of subsurface water content and regardless Singh, 2001), and as such may not necessarily act to prolong whether the subsurface is aggregated or not. cell activity. This was clearly reflected on sand-covered biocrusts at the An additional suggested hydrological role of EPS is the fa- Nizzana research site (NRS) in the Hallamish dune field, Negev cilitation of vapor absorbance and subsequent dew formation, Desert, Israel. Even when covering semi pure sand (⁓98% sand suggested to serve as an additional and important water source with only ⁓2% of silt and clay), extremely thin immature cya- for biocrusts (Colica et al., 2014; Fischer et al., 2012; Hage- nobacterial crusts, only 0.5 mm thick, were able to generate mann et al., 2015; Jia et al., 2014; Lange et al., 1992; Mager runoff (Kidron, 2015). Similarly, 1 mm-thick biocrusts which and Thomas, 2011; Veste et al., 2001). While reported to trig- covered the xeric aspects of the dunes commonly generate ger vapor absorption by Colica et al. (2014) following cyano- runoff (Kidron, 1999; Kidron et al., 2003). With typical soils, bacteria inoculation in the Hobq Desert in China, extensive some of which are well aggregated, having infiltration rates of field measurements, which were carried out in the dewy Negev, 10–150 mm/h (Dunkerley, 2000; Kato et al., 2009; Wood and failed to show vapor condensation on the ground (Kidron and Blackburn, 1981), i.e., substantially lower than sand (having Kronenfeld, 2020a,b). Only once, very limited dew formation >300 mm/h of infiltration; Lichner et al., 2010; Xiao et al., was noted (Kidron et al., 2002). Yet, based on a detailed analy- 2019b), one may safely conclude that runoff over the 0.5 mm- sis, it was too short to allow for net photosynthesis by the cya- thick biocrusts was not impacted by the underlying sand, but nobacterial biocrusts (Kidron and Starinsky, 2019), therefore rather by the biocrust. With HOF being the prevailing mecha- casting doubt on the possible role played by EPS in providing nism that determines runoff generation in arid and semiarid dew water which will serve as an additional water source for regions, the aggregation capability of the subsurface is of minor the cyanobacterial biocrusts. No net photosynthesis was also relevance. recorded from a mixed cyanobacteria and crustose lichens in the Negev following dew (Wilske et al., 2008). Contrary to 2.2 Hydrophobicity detached cobbles or stones which readily condense dew and subsequently serve as an important water source for the stone- Hydrophobicity (water repellency) is a temporal phenome- dwelling lichens (Lange et al., 1970), minimum temperatures at non (Francis et al., 2007) during which a switch in the molecule the soil surface rarely reach the dew point temperature (Td) – a position of hydrophyllic and hydrophobic ends takes place prerequisite for dew formation (Beysens, 2018). (Hallett, 2008). Accordingly, with moisture decrease, the hy- Not less controversial is the possible effect of EPS on infil- drophilic ends tend to strongly bond with each other leaving the tration and runoff. In light of the cardinal role played by runoff hydrophobic ends exposed, resulting in hydrophobicity. While in shaping many aspects of the environment (hydrological, the duration during which the soil turns hydrophobic may be geomorphological, pedological, ecological), elucidation of the long, the process during which hydrophobicity ceases is how- possible role played by EPS in runoff generation is of major ever rapid, sometimes within minutes (Oostindie et al., 2013). importance. Toward this end, the current state-of-the art Some of the biocrust population, such as cyanobacteria, algae, knowledge will be briefly presented, ungrounded conclusions bacteria, and fungi were found to posses temporal hydrophobic published in the literature will be discussed, and a wide array of properties, assumed to be caused by EPS (Mugnai et al., direct and indirect evidence which point to the possible role of 2020a). EPS in runoff generation will be analyzed. Hydrophobicity was extensively reported from humid re- gions (Dekker and Ritsema, 1994, 2000; Doerr et al., 2006; 2 THE POSSIBLE INVOLVEMET OF EPS IN RUNOFF Drahorad et al., 2013; Fischer et al., 2010, 2013; Jungerius and GENERATION van der Muellen, 1988; Lichner et al., 2013; Rutin, 1983). 2.1 Enhanced soil aggregation However, runoff was convincingly shown to result from hydro- phobicity mainly in northern and central Europe (Fischer et al., With EPS assisting in cell adhesion and cohesion, EPS may 2010; Lichner et al., 2010, 2012, 2018). The first example that I increase soil aggregation, contributing to a better soil structure am aware of and which linked between hydrophobicity and 361 Giora J. Kidron runoff generation on biocrusts was reported from the Dutch 1997). Additional supportive evidence was obtained when the coast during the end of the summer (Jungerius and de Jong, ratio of total carbohydrates to the chlorophyll content was 1989; Rutin, 1983). While hydrophobicity was also reported sought. Thus, assuming a similar amount of carbohydrates from semiarid regions (Chamizo et al., 2012; Mayor et al., within a single cell, and given the fact that most EPSs are car- 2009; Rodriguez-Caballero et al., 2013), the link between hy- bohydrates (Mazor et al., 1996), excess of carbohydrates rela- drophobicity and runoff was not yet substantiated. tive to the chlorophyll content (i.e., high ratio of carbohydrates At the subhumid Dutch coast hydrophobicity was reported to chlorophyll) may attest to carbohydrates which are located following unusual weather conditions during which a long dry outside the cell walls, i.e., extracellular carbohydrates, which period followed a wet period, i.e., during the end of the sum- constitute the majority of the EPS (De Brower and Stal, 2001; mer. Runoff generation took place regardless of rain intensities Kidron et al., 1999). Indeed, when the runoff yield of variable (Rutin, 1983). It was temporal and vanished once the surface plots having 5 different crust types was compared against the was sufficiently wetted. According to Oostindie et al. (2013), ratio of carbohydrates to chlorophyll, a linear relation was hydrophobicity ceased once the moisture content of sand reach- obtained, pointing to a possible link between EPS and runoff generation (Kidron et al., 2003). es ⁓3%. One may therefore conclude that (a) hydrophobicity This measure for assessing the amount of EPS is obviously may only take place once a very dry spell follows a wet period, crude and may be applicable for a similar population of micro- such as at the end of the summer or during long breaks between organisms characterizing habitats with similar climate and soil rain events, (b) runoff induced by hydrophobicity will cease properties. For a more comprehensive comparison of different once the soil gets sufficiently wet, (c) runoff induced by hydro- climates and different soils, a study of the properties of the phobicity will take place regardless of rain intensity, as was constituents of the EPS is required. This was done once a com- indeed recorded at the Dutch coast (Rutin, 1983). parison between the cyanobacterial biocrusts of NRS (which Runoff due to hydrophobicity was thought to take place in receive an annual precipitation of 95 mm) and the cyanobacte- the Negev (Felde et al., 2014; Keck et al., 2013), the Tabernas ria-algae biocrust that cover the Israeli Mediterranean coast, the (Chamizo et al., 2012; Rodriguez-Caballero et al., 2013), and Nizzanim dune field (NIM) (which receives an annual precipi- the Sahel (Malam-Issa et al., 2009; Talbot and Williams, 1978), tation of 500 mm) was carried out. The comparison was trig- but nevertheless no convincing data for meter-scale runoff gered by the different populations of the crusts (cyanobacterial which stems from hydrophpbocity were yet published. On the in NRS and cyanobacteria-algae in NIM) and by the fact that contrary, in all places a close link between rain intensity and while runoff was commonly produced in NRS already during runoff took place, and runoff generation was higher on the wet medium rain intensities as low as 9 mm/h (Kidron and Yair, soils, all pointing to runoff due to pore clogging rather than 1997), no runoff was generated by the NIM crust during three hydrophobicity. Thus for instance, an attempt to attribute runoff years of field measurements albeit the fact that the NIM crusts generation to hydrophobicity was also made for NRS (Felde et had substantially higher chlorophyll content and was subjected al., 2014; Keck et al., 2013). However, further measurements in to substantially higher rain intensities (Kidron and Büdel, NRS by the same group of scholars did not show hydrophobi- 2014). city (Mugnai et al., 2018), and the "hydrophobicity hypothesis" Figure 1 shows a comparison between two interdunal types was not further advanced (Keck et al., 2016). of crusts from Nizzana and one interdunal crust from Nizzanim. I may add that although theoretically runoff due to hydro- No runoff was generated from the NIM crust following sprin- phobicity may be followed by HOF (triggered by the intermit- kling (with 22.5 mm/h for 15 min). The Nizzana crusts (NIZa, tent character and high intensity fluctuation of the rain; Lázaro NIZb) yielded however runoff (Fig. 1a). While exhibiting sub- et al., 2001; Kidron, 2011), no distinction between both mecha- stantially higher thickness and chlorophyll content (Fig. 1b, c), nisms was yet reported, and more importantly, no meter-scale the NIM crust showed however lower water-holding capacity runoff yield that stems from hydrophobicity, was yet reported. (WHC) (Fig. 1d), lower compressive strength (Fig. 1e), lower One may thus assume that even if taking place, the hydrophobic rigidity (Fig. 1f) and a lower ratio between total carbohydrates effect on runoff in these sites is marginal. and chlorophyll (Fig. 1g). Notwithstanding is the ratio of car- Additionally, even when specific hydrophobic constituents bohydrates to chlorophyll, which showed a close link with within the EPS were identified by various scholars in different runoff coefficient and pointed to the apparent important role biocrusts, hydrophobicity was not necessarily detected. Thus played by the EPS in runoff generation. This was further veri- for instance, although fucose and rhamnose are considered fied by the properties of the EPS, such as the higher rigidity hydrophobic (Mugnai et al., 2018), no hydrophobicity was that characterized the NRS biocrusts, which may exert high detected in Scytonema sp. albeit the fact that both of these integrity to the crust. Clear differences were also noted in SEM sugars were present in relatively high amounts in the EPS of pictographs. Thus for instance, while mainly TB-EPS charac- this species (Chamizo et al., 2019). Similarly, although contain- terized the NIM biocrusts (Fig. 2a), abundant LB-EPS charac- ing rhamnose, no hydrophobicity was found in Schizothrix sp. terize the NRS biocrusts, (Fig. 2b). One may conclude that (Mugnai et al., 2018). while the ratio of carbohydrates to chlorophyll may serve as a basic indication for the total amount of EPS, which may serve 2.3 Partial surface pore clogging in turn as a useful crude estimation for the possible dominance of the EPS, a full exploration of the EPS role in runoff genera- A close link between partial surface pore clogging (PSPC) tion also requires the study of the properties of the EPS. and EPS and between PSPC and runoff was long ago reported (Kidron and Yair, 1997; Mazor et al., 1996; Verrecchia et al., 1995). Not only that a close link was found between rain inten- 3 SYNTHESIS sity and runoff, but the lack of runoff on dry crusts during the beginning of rain events even when subjected to high-intensity Attempts to link between the different constituents that make rains was attributed to the necessary delay that stems from the up the biocrust EPS and the hydrological role of the biocrusts time duration required to allow for water imbibitions by the had only limited success. On the one hand, scholars tried to crust, which will result in turn in PSPC (Kidron and Yair, identify constituents with hydrophobic characteristics such as 362 The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review 15 a NIZa NIZb NIM NIZa NIZb NIM NIZa NIZb NIM NIZa NIZb NIM NIZa NIZb NIM 10 400 NIZa NIZb NIM NIZa NIZb NIM Crust Fig. 1. A comparison between two interdunal crust types taken from Nizzana (NIZ) and were shown to readily generate runoff under field conditions and one from the Nizzanim dune field (NIM) that failed to produce runoff under field conditions. The figure shows runoff coef- ficient following sprinkling experiments (a), the thickness (b), chlorophyll content (c), water holding capacity (d), compressive strength (e), rigidity (f) and the ratio of total carbohydrates (CRB) to chlorophyll (CHL) (g). Modified from Kidron et al. (2020). fucose and rhamnose and yet, even when they occupy a fairly which hydrophobicity is vanished also brings into question the high proportion of the total EPS, hydrophobicity was not al- attempts to link between hydrophobic constituents and biocrust ways detected. Moreover, given the fact that hydrophobicity hydrophobicity. Thus for instance, while sulfated groups and may vanish within minutes given that sufficient amount of uronic acids are hydrophilic (Rossi and De Philippis, 2016), water is supplied to the soil, the hypothesis regarding the tran- their presence cannot fully explain water absorption by the sient nature of hydrophobicity during which polar and non- crust. For example, while young cyanobacterial crusts were polar ends of the EPS molecules switch their position is sup- found to only posses low amounts of uronic acids (Mugnai et ported, making the link between hydrophobicity and certain al., 2020b), young cyanobacterial crusts were still observed to types of sugars less likely. Furthermore, the rapidity during readily absorb water during a sprinkling experiment, and WHC (%) Thickness (mm) Rigidity (Pa^10 ) Runoff Coefficient (%) Chlorophyll (mg/m ) Ratio CRB/CHL Strength (g/cm ) Giora J. Kidron 10µ 10µ Fig. 2. SEM pictographs showing the Nizzanim (NIM) (a) and the Nizzana (NIZ) (b) crusts. Whereas LB-EPS is hardly noted in NIM it abounds in NIZ. subsequently to generate runoff (Kidron, 2015). Nevertheless, it order decrease in the micropores volume. Subsequently, I is believed that water absorbance may vary in accordance with would like to suggest that the relative amount of WHC may the EPS properties (Chenu, 1993). therefore serve as a possible indicator for the crust potentiality When the water-holding capacity (WHC) of the cyanobacte- to generate runoff. The higher the amount of WHC, the higher rial crusts from NRS was compared to cyanobacteria-algae is the amount of water occupying the pores, and the higher the crusts from NIM, substantially higher WHC characterize the probability that the water-filled pores are efficiently clogged. NRS crusts. Interestingly, the NRS crusts were also character- This may be also facilitated by the high rigidity of the crust that ized by abundant LB-EPS (Fig. 2b). I would like to suggest that will resist the rain drop impact and possible infiltration through LB-EPS may play a cardinal role in water absorption and hence the crust openings. With the impediment of infiltration, rain, in PSPC. Contrary to TB-EPS which is limited by physiological which will exceed a certain rate of input, will run off the sur- constraints, and therefore has distinct thickness (Rossi and De face. Philippis, 2015), LB-EPS commonly occupies large pore vol- With water addition, the biocrust readily reaches saturation ume (Nicolaus et al., 1999), and as such may absorb exception- leading in turn to infiltration-excess (Hortonian) overland flow ally large amounts of water. (HOF). Unlike the case of hydrophobicity during which water In this regard, it is suggested that rather than TB-EPS, which repellency takes place and runoff results from the incapability was considered to play major role in crust hydrology (De of the water to infiltrate the soil, runoff following pore clogging Philippis, 2015), LB-EPS may play the central role in runoff depends upon the capability of the water to readily saturate the generation. Occupying a much larger pore volume, LB-EPS upper soil surface skin. Runoff will not begin instantly as in the may principally determine the WHC of the crust, as clearly case of hydrophobicity, but only following several minutes or shown in the SEM pictographs of the NRS crusts. High WHC more during which water absorption by the biocrust-induced implies high degree of swelling (Chenu, 1993; Or et al., 2007) EPS will suffice to partially clog the pores (Verrecchia et al., and subsequently efficient pore clogging and infiltration imped- 1995). iment. For instance, according to Chenu (1993), addition of During the current review, an attempt was made to link be- EPS to kaolinite and montmorillonite decreased the pore diame- tween the crust properties and above all, the biocrust-induced ter in high water potentials from 0.5–4 μ to an average of 0.2 μ. EPS and the hydrological mechanisms responsible for runoff According to Verrecchia et al (1995), within <30 min of generation in arid and semiarid regions. While under similar wetting, 8–12-fold decrease in the volume of the biocrust mi- environmental conditions the amount of EPS may serve as a cropores took place. Both groups of scholars report on one- crude indicator for the crust capability to partially clog the 364 The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review surface pores (Kidron et al., 2003), for a more complete and semiarid ecosystem: A complex balance between biological reliable outcome, evaluating the EPS properties is of major soil crust features and rainfall characteristics. J. Hydrol., importance (Chenu, 1993; Fick et al., 2019; Kidron et al., 452–453, 130–138. 2020). It follows that among the important functions carried out Chamizo, S., Belnap, J., Eldridge, D.J., Cantón, Y., Malam- by the EPS, EPS may play an important role in runoff genera- Issa, O., 2016. The role of biocrusts in arid land hydrology. tion, as in the case of NRS, which may therefore substantially In: Weber, B., Büdel. B., Belnap. J. (Eds.): Biological Soil impact the hydrology, geomorphology, pedology and ecology Crusts: An Organizing Principle in Dryland. Ecological of arid and semiarid ecosystems. Studies 226. Springer, Switzerland, pp. 321–346. Currently, although occasional hydrophobicity was reported Chamizo, S., Adessi, A., Mugnai, G., Simiani, A., De Philippis, from arid and especially semiarid zones, there are no convinc- R., 2019. Soil type and cyanobacteria species influence the ing data that link between EPS-induced hydrophobicity to macromolecular and chemical characteristics of the polysac- meter-scale runoff generation in arid and semiarid regions. The charide matrix in induced biocrusts. Microbial Ecol., 78, occurrence of both mechanisms is theoretically feasible, as 482–493. DOI: 10.1007/s00248-018-1305-y reported during lab measurements with biocrusts that were Chen, L.Z., Wang, G.H., Hong, S., Liu, A., Li, C., Liu, Y.D., induced to develop hydrophobicity, during which two separated 2009. UV-B-induced oxidative damage and protective role runoff peaks (with a ~5 min interval) were recorded during of exopolysaccharides in desert cyanobacterium Microcoleus continuous sprinkling: following hydrophobicity and following vaginatus. J. Integrat. Plant Biol., 51, 2, 194–200. DOI: pore clogging (Kidron et al., 1999). This was not yet shown 10.1111/j.1744-7909.2008.00784.x under field conditions, and unlike PSPC, hydrophobicity was Chen, Y., Tarchitzky, J., Brouwer, J. Morin, J., Banin, A., not yet shown to play an important role in runoff generation in 1980. Scanning electron microscope observations in soil arid and semiarid zones. In this regard it is useful to refer to crusts and their formation. Soil Sci., 130, 49–55. William of Occam: "Entia non sunt multiplicanda praeter ne- Chenu, C., 1993. Clay-or sand- polysaccharide associations as cessitate", i.e., "Entities should not be multiplied more than models for the interface between micro-organisms and soil: necessary". water related properties and microstructure. Geoderma, 56, 143–156. REFERENCES Colica, G., Li, H., Rossi, F., Li, D., Liu, Y., De Philippis, R., 2014. Microbial secreted exopolysaccharides affect the hy- Belnap, J., 2006. The potential roles of biological soil crusts in drological behavior of induced biological soil crusts in de- dryland hydrologic cycles. Hydrol. Process., 20, 3159–3178. sert sandy soils. Soil Biol. Biochem., 68, 62–70. Beven, K.J., Kirkby, M.J., 1979. A physically based, variable De Brouwer, J.F.C., Stal, L.J., 2001. Short-term dynamics in contributing area model of basin hydrology. Hydrol. Sci. microphytobenthos distribution and associated extracellular Bull., 24, 43–69. DOI: 10.1080/02626667909491834 carbohydrates in surface sediments of the intertidal mudflat. Beysens, D., 2018. Dew Water. River Publishers, Gistrup, Marine Ecol. Progress Series, 218, 33–44. Denmark. de Jong, S.M., Addink, E.A., Van Beek, L.P.H., Duijsings, D., Blackburn, W.H., 1975. Factors influencing infiltration and sed- 2011. Physical characterization, spectral response and re- iment production of semiarid rangelands in Nevada. Water motely sensed mapping of Mediterranean soil surface crusts. Resour. Res., 6, 929–937. DOI: 10.1029/WR011i006p00929 Catena, 86, 24–35. Brotherson, J.D., Rushforth, S.R., 1983. Influence of crypto- Dekker, L.W., Ritsema, C.J., 1994. How water moves in a gamic crusts on moisture relationships of soils in Navajo water repellent sandy soil. 1. Potential and actual water re- National Monument, Arizona. Great Basin Natur., 43, pellency. Water Resour. Res., 30, 2507–2517. 73–78. Dekker, L.W., Ritsema, C.J., 2000. Wetting patterns and mois- Brüll, L.P., Huang, Z., Thomas-Oates, J.E., Paulsen, B.S., Co- ture variability in water repellent Dutch soils. J. Hydrol., hen, E.H., Michaelsen, T.E., 2000. Studies of polysaccha- 231–232, 148–164. rides from three edible species of Nostoc (cyanobacteria) De Philippis, R., 2015. The stability and the hydrological be- with different colony morphologies: Structural characteriza- havior of biological soil crusts is significantly affected by tion and effect on the complement system of polysaccharides the complex nature of their polysaccharide matrix. EGU from Nostoc commune. J. Phycol., 36, 871–881. General Assembly, 12–17 April, 2015, Vienna, Austria. ID: Cammeraat, E.L.H., 2004. Scale dependent thresholds in hydro- 3513. logical and erosion response of a semi-arid catchment in Demig, J.W., Young, J.N., 2017. The role of exopolysaccha- southeast Spain. Agric. Ecosys. Environ., 104, 317–332. rides in microbial adaptation to cold habitats. In: Margesin, DOI: 10.1016/j.agee.2004.01.032 R. (Ed.): Psychrophiles: From Biodiversity to Biotechnolo- Campbell, S.E., 1979. Soil stabilization by prokaryotic desert gy. Springer Inter Pub. AG. DOI: 10.1007/978-3=319- crusts: Implications for Precambrian land biota. Orig. Life, 57057-0-0122. 9, 335–348. Doerr, S.H., Shakesby, R.A., Dekker, L.W., Ritsema, C.J., Cantón, Y., Chamizo, S., Rodríguez-Caballero, E., Lazáro, R., 2006. Occurrence, prediction and hydrological effects of wa- Roncero-Ramos, B., Roman, J.R., Solé-Benet, A., 2020. ter repellency amongst major soil and land-use types in a Water regulation in cyanobacterial biocrusts from drylands: humid temperate climate. Eur. J. Soil Sci., 57, 741–754. Negative impacts of anthropogenic disturbance. Water, 12, Drahorad, S., Steckenmesser, D., Felix-Henningsen, P., Lich- 720. https://doi.org/10.3390/w12030720 ner, L., Rodny, M., 2013. Ongoing succession of biological Chamizo, S., Cantón, Y., Lázaro, R., Domingo, F., 2013. The soil crusts increases water repellency – a case study on role of biological soil crusts in soil moisture dynamics in Arenosols in Sekule, Slovakia. Biologia, 68, 1089–1093. two semiarid ecosystems with contrasting soil textures. J. Dunkerley, D., 2000. Hydrological effects of dryland shrubs: Hydrol., 489, 74–84. defining the spatial extent of modified soil water uptake Chamizo, S., Cantón, Y., Rodríguez-Caballero, E., Domingo, rates at an Australian desert site. J. Arid Environ., 45, 159– F., Escudero, A., 2012. Runoff of contrasting scales in a 172. DOI: 10.1006/jare.2000.0636 365 Giora J. Kidron Dunne, T., 1990. Hydrology, mechanics, and geomorphic im- crust in a revegetated area of the Tengger Desert, Northern plications of erosion by subsurface flow. In: Higgins, C.G., China. J. Hydrol., 519, 2341–2349. Coates, D.R. (Eds.): Groundwater Geomorphology: The Jungerius, D., van der Meulen, F., 1988. Erosion processes in a Role of Subsurface Water in Earth-Surface Processes and dune landscape along the Dutch coast. Catena, 15, 217–228. Landforms. Geological Society of America, Special Paper Jungerius, P.D., de Jong, J.H., 1989. Variability of water repel- 252, pp. 1–28. lence in the dunes along the Dutch coast. Catena, 16, 491– Dunne, T., Black, R.D., 1970. An experimental investigation of 497. runoff production in permeable soils. Water Resour. Res., 6, Kato, H., Onda, Y., Tanaka, Y., Asano, M., 2009. Field meas- 478–490. DOI: 10.1029/WR006i002p00478 urement of infiltration rate using an oscillating nozzle rain- Ehling-Schulz, M., Schere, S., 1999. UV protection in cyano- fall simulator in the cold, semiarid grassland of Mongolia. bacteria. Eur. J. Phycol., 34, 329–338. Catena, 76, 173–181. DOI: 10.1016/j.catena.2008.11.003 Epstein, E., Grant, W.J., 1993. Soil crust formation as affected Keck, H., Felde, V.J.M.N.L., Drahorad, S.L., Felix- by raindrop impact. In: Hadas, A., Swartzendruber, D., Rit- Henningsen, P., 2013. Effects of biological soil crusts on jema, P.E., Fuchs, M., Yaron, B. (Eds.): Physical Aspects of water repellency in a sand dune ecosystem of the NW Soil Water and Salts in Ecosystems. Springer, Berlin and Negev, Israel. Second Intgernational Workshop on th th Heidelberg, pp. 195–201. Biological Soil Crusts, Madrid, 10 –13 June, 2013. Felde, V.J.M.N.L., Peth, S., Uteau-Puschmann, D., Drahorad, Keck, H., Felde, V.J.M.N.L., Drahorad, S.L., Felix-Hennigsen, S., Felix-Henningsen, P., 2014. Soil microstructure as an P., 2016. Biological soil crusts cause subcritical water repel- under-explored feature of biological soil crust hydrological lency in a sand dune ecosystem located along a rainfall gra- properties: case study from the NW Negev Desert. Bio- dient in the NW Negev Desert, Israel. J. Hydrol. Hydro- divers. Conserv., 23, 1687–1708. mech., 64, 133–140. Fick, S.E., Barger, N.N., Duniway, M.C., 2019. Hydrological Kidron, G.J., 1999. Differential water distribution over dune function of rapidly induced biocrusts. Ecohydrology, 12, slopes as affected by slope position and microbiotic crust, e2089. DOI: 10.1002/eco.2089 Negev Desert, Israel. Hydrol. Process., 13, 1665–1682. DOI: Fischer, T., Veste, M., Wiehe, W., Lange, P., 2010. Water 10.1002/(SICI)1099-1085(19990815) repellency and pore clogging at early successional stages of Kidron G.J., 2011. Runoff generation and sediment yield on microbiotic crusts on inland dunes, Brandenburg, NE Ger- homogeneous dune slopes: scale effect and implications for many. Catena, 80, 47–52. DOI: 10.1016/j.catena.2009.08.009 analysis. Earth Surf. Process. Landf., 36, 1809–1824. DOI: Fischer, T., Veste, M., Bens, O., Hüttl, R.F., 2012. Dew 10.1002/esp.2203 formation on the surface of biological soil crusts in central Kidron, G.J., 2015. The role of crust thickness in runoff genera- European sand ecosystems. Biogeosciences, 9, 4621–4628. tion from microbiotic crusts. Hydrol. Process., 29, 1783– Fischer, T., Yair, A., Veste, M., Geppet, H., 2013. Hydraulic 1792. DOI: 10.1002/hyp.10243 properties of biological soil crusts on sand dunes studied by Kidron, G.J., 2021. Comparing overland flow processes be- C-CP/MAS-NMR: A comparison between an arid and tween semiarid and humid regions: Does saturation overland temperate site. Catena, 110, 155–160. flow take place in semiarid regions? J. Hydrol., 593, 125624. Fox, D.M., Bryan, R.B., Price, A.G., 2004. The role of soil DOI: 10.1016/j.jhydrol.2020.125624 surface crusting in desertification and strategies to reduce Kidron, G.J., Büdel, B., 2014. Contrasting hydrological re- crusting. Environ. Monitor. Assess., 99, 149–159. sponse of coastal and desert biocrusts. Hydrol. Process., 28, Francis, M.L., Fey, M.V., Prinsloo, H.P., Ellis, F., Mills, A.J., 361–371. DOI: 10.1002/hyp.9587 Medinski, T.V., 2007. Soils of Namaqualand: Compensa- Kidron, G.J., Kronenfeld, R., 2020a. Assessing the likelihood tions for aridity. J. Arid Environ., 70, 588–603. of the soil surface to condense vapor: The Negev experience. Galle, S., Arendt, E.K., 2014. Exopolysaccharides from sour- Ecohydrology, 13, e2200. DOI: 10.1002/eco.2200 dough lactic acid bacteria. Critical Rev. Food Sci. Nutr., 54, Kidron, G.J., Kronenfeld, R., 2020b. Atmospheric humidity is 891–901. DOI: 10.1080/10408398.2011.617474 unlikely to serve as an important water source for crustose Hagemann, M., Henneberg, M., Felde, V.J.M.N.L., Drahorad, soil lichens in the Tabernas Desert. J. Hydrol. Hydromech., S.L., Berkowicz, S.M., Felix-Henningsen, P. Kaplan, A., 68, 359–367. DOI: 10.2478/johh-2020-0034 2015. Cyanobacterial diversity in biological soil crusts along Kidron, G.J., Starinsky, A., 2019. Measurements and ecological a precipitation gradient, Northwest Negev Desert, Israel. implications of non-rainfall water in desert ecosystems – A Microbiol. Ecol., 70, 219–230. review. Ecohydrology, 12, e2121. DOI: 10.1002/eco.2121 Hallett, P.D., 2008. A brief overview of the causes, impacts and Kidron, G.J., Tal, S.Y., 2012. The effect of biocrusts on evapo- melioration of soil water repellency – a review. Soil Water ration from sand dunes in the Negev Desert. Geoderma, 179- Res., 3, S21–S29. 180, 104–112. DOI: 10.1016/j.geoderma.2012.02.021 Harper, K.T., Marble, J.R., 1988. A role for nonvascular plants Kidron, G.J., Yair, A., 1997. Rainfall-runoff relationships over in management of arid and semiarid rangelands. In: Tuller, encrusted dune surfaces, Nizzana, Western Negev, Israel. P.T. (Ed.): Applications of Plant Sciences to Rangeland Earth Surf. Process. Landf., 22, 1169–1184. DOI: Management and Inventory. Kluwer, Amsterdam, pp. 135– 10.1002/esp.1532 169. Kidron, G.J., Yaalon, D.H., Vonshak, A., 1999. Two causes for Heil, J.W., Juo, A.S.R., McInnes, K.J., 1997. Soil properties runoff initiation on microbiotic crusts: hydrophobicity and influencing surface sealing of some sandy soils in the Sahel. pore clogging. Soil Sci. 164, 18–27. Soil Sci., 162, 459–469. Kidron, G.J., Herrnstadt, I., Barzilay, E., 2002. The role of dew Horton, R.E., 1933. The role of infiltration in the hydrological as a moisture source for sand microbiotic crusts in the Negev cycle. EOS Transactions AGU, 14, 446–460. DOI: Desert, Israel. J. Arid Environ., 52, 517–533. DOI: 10.1029/TR014;001p00446 10.1016/jare.2002.1014 Jia, R.L., Li, X.R., Liu, L.C., Pan, Y.X., Gao, Y.H., Wei, Y.P., Kidron, G.J., Wang, Y., Herzberg, M., 2020. 2014. Effects of sand burial on dew deposition on moss soil Exopolysaccharides may increase biocrust rigidity and 366 The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones – a mini review induce runoff generation. J. Hydrol., 588, 125081. DOI: R.Y., 2014. Extracellular polymeric substances of bacteria 10.1016/J.JHYDROL.2020.125081 and their potential environmental applications. J. Environ. Kidron, G.J., Yair, A., Vonshak, A., Abeliovich A., 2003. Mi- Manage., 144, 1–25. DOI: 10.1016/j.jenvman.2014.05.010. crobiotic crust control of runoff generation on sand dunes in Mugnai, G., Rossi, F., Chamizo, S., Adessi, A., De Philippis, the Negev Desert. Water Resour. Res., 39, 1108. DOI: R., 2020a. The role of grain size and inoculums amount of 10.1029/2002WR001561.2003 biocrust formation by Leptolyngbya ohadii. Catena, 184, Lange, O.L., Schulze, E.D., Koch, W., 1970. Ecophysiological 104248. DOI: 10.1016/j.catena.2019.104248 investigations on lichens of the Negev Desert, III: CO2 gas Mugnai, G., Rossi, F., Mascalchi, C., Ventura, S., De Philippis, exchange and water metabolism of crustose and foliose li- R., 2020b. High arctic biocrusts: characterization of the ex- chens in their natural habitat during the summer dry period. opolysaccharidic matrix. Polar Biol., 43, 1805–1815. DOI: Flora, 159, 525–538. 10.1007/s00300-020-02746-8 Lange, O.L., Belnap, J., Reichenberger, H., 1998. Photosynthe- Mugnai, G., Rossi, F., Felde, V.J.M.N.L., Colesie, C., Büdel, sis of the cyanobacterial soil-crust lichen Collema tenax B., Peth, S., Kaplan, A., De Philippis, R., 2018. Develop- from arid lands in southern Utah, USA: role of water content ment of the polysaccharide matrix in biocrusts induced by a on light and temperature response of CO exchange. Func. cyanobacterium inoculated in sand microcosms. Biol. Fert. Ecol., 12, 195–202. Soils, 54, 27–40. Lange, O.L., Kidron, G.J., Büdel, B., Meyer, A., Kilian, E., Nagar, S., Antony, R., Thamban, M., 2021. Extracellular poly- Abeliovitch, A., 1992. Taxonomic composition and photo- meric substances in Antarctic environments: A review of synthetic characteristics of the biological soil crusts covering their ecological roles and impact on glacier biogeochemical sand dunes in the Western Negev Desert. Func. Ecol., 6, cycles. Polar Sci. DOI: 10.1016/j.polar.2021.100686 519–527. Nicolaus, B., Panico, A., Lama, L., Romano, I., Manca, M.C., Lázaro, R., Rodrigo, F.S., Gutiérrez, L., Domingo, F., De Giulio, A., Gambacorta, A., 1999. Chemical composition Puigdegabregas, J., 2001. Analysis of 30-year rainfall record and production of exopolysaccharides from representative (1967-1997) in semi-arid SE Spain for implications on vege- members of heterocystous and non-heterocystous cyanobac- tation. J. Arid Environ., 48, 373–395. teria. Phytochemistry, 52, 639–647. Li, S., Xiao, B., Sun F., Kidron, G.J., 2021. Moss-dominated Onofiok, O., Singer, M.J., 1984. Scanning electron microscope biocrusts greatly enhance water vapor sorption capacity and studies of surface crusts formed by simulated rainfall. Soil increase non-rainfall water deposition in drylands. Geoder- Sci. Soc. Am. J., 48, 1137–1143. ma, 388, 114930. DOI: 10.1016/j.geoderma.2021.114930 Oostindie, K., Dekker, L.W., Wesseling, J.G., Ritsema, C.J., Lichner, L., Hallett, P.D., Orfánus, T., Czachor, H., Rajkai, K., Geissen, V., 2013. Development of actual water repellency Šir, M., Tesař, M., 2010. Vegetation impact on the hydrolo- in a grass-covered dune sand during dehydration experiment. gy of an aeolian sandy soil in a continental climate. Ecohy- Geoderma, 204–205, 23–30. drology, 3, 413–420. Or, D., Smets, B.F., Wraith, J.M., Dechesne, A., Friedman, Lichner, L., Holko, L., Zhukova, N., Shacht, K., Rajkai, K., S.P., 2007. Physical constraints affecting bacterial habitats Fodor, N., Sándor, R., 2012. Plants and biological soil crust and activity in unsaturated porous media – a review. Adv. influence the hydrophysical parameters and water flow in an Water Resour., 30, 1505–1527. aeolian sandy soil. J. Hydrol. Hydromech., 60, 309–318. Otero, A., Vincenzini, M., 2003. Extracellular polysaccharide Lichner, L., Hallett, P.D., Drongova, Z., Czachor, H., Kovacik, synthesis by Nostoc strains as affected by N source and light L., Mataix-Solera, J., Homolák, M., 2013. Algae influence intensity. J. Biotechnol., 102, 143–152. the hydrophysical parameters of a sand soil. Catena, 108, Pagliai, M., Bisdom, E.B.A., Ledin, S., 1983. Changes in sur- 58–68. face structure (crusting) after application of sewage sludge Lichner, L., Felde, V.J.M.N.L., Büdel, B., Leue, M., Gerke, and pig slurry to cultivated agricultural soils in northern Ita- H.H., Ellerbrock, R.H., Kollár, J., Rodny, M., Šurda, P., ly. Geoderma, 30, 35–53. Fodor, N., Sándor, R., 2018. Effect of vegetation and its suc- Pereira, S., Zille, A., Micheletti, E., Moradas-Ferreira, P., De cession on water repellency in sandy soils. Ecohydrology, Philippis, R., Tamagnini, P., 2009. Complexity of cyanobac- 11, e1991. DOI: 10.1002/eco.1991 terial exopolysaccharides: composition, structures, inducing Mager, D.M., Thomas, A.D., 2011. Extracellular polysaccha- factors and putative genes involved in their biosynthesis and rides from cyanobacterial soil crusts: A review of their role assembly. FEMS Microbiol. Rev., 33, 917–941. in dryland soil processes. J. Arid Environ., 75, 91–97. Pringault, O., Garcia-Pichel, F., 2004. Hydrotaxis of cyanobac- Malam-Issa, O., Défarge, C., Trichet, J., Valentin, C., Rajot, teria in desert crusts. Microb. Ecol., 47, 366–373. J.L., 2009. Microbiotic soil crusts in the Sahel of western Redmile-Gordon, M., Gregory, A.S., White, R.P., Watts, C.W., Niger and their influence on soil porosity and water dynam- 2020. Soil organic carbon, extracellular polymeric substanc- ics. Catena, 77, 48–55. es (EPS), and soil structural stability as affected by previous Mayor, A.G., Bautista, S., Bellot, J., 2009. Factors and interac- and current land-use. Geoderma, 363. 114143. DOI: tions controlling infiltration, runoff, and soil loss at the mi- 10.1016/j.geoderma.2019.114143 croscale in a patchy Mediterranean semiarid landscape. Rodriguez-Caballero, E., Cantón, Y., Chamizo, S., Lázaro, R., Earth Surf. Process. Landf., 34, 1702–1711. DOI: Escudero, A., 2013. Soil loss and runoff in semiarid ecosys- 10.1002/esp.1875 tems: A complex interaction between biological soil crusts, Mazor, G., Kidron, G.J., Vonshak, A., Abeliovich, A., 1996. micro-topography, and hydrological drivers. Ecosystems, 16, The role of cyanobacterial exopolysaccharides in structuring 529–546. desert microbial crusts. FEMS Microbiol. Ecol., 21, 121– Rodriguez-Caballero, E., Belnap, J., Büdel, B., Crutzen, P.J., 130. DOI: 10.1111/j.1574-6941.1996.tb00339.x Andreae, M.O., Pöschl, U., Weber, B., 2018. Dryland photo- McIntyre, D.S., 1958. Soil splash and the formation of surface autotrophic soil surface communities endangered by global crusts by raindrop impact. Soil Sci., 85, 261–266. change. Nat. Geosci., 11, 185–189. DOI: 10.1038/s41561- More, T.T., Yadav, J.S.S., Yan, S., Tyagi, R.D., Surampalli, 018-0072-1 367 Giora J. Kidron Rossi, F., De Philippis, R., 2015. Role of cyanobacterial exopol- Verrecchia, E., Yair, A., Kidron, G.J., Verrecchia, K., 1995. ysccharides in phototrophic biofilms and in complex micro- Physical properties of the psammophile cryptogamic crust bial mats. Life, 5, 1218–1238. DOI: 10.3390/life5021218 and their consequences to the water regime of sandy soils, Rossi, F., De Philippis, R., 2016. Excocellular polysaccharides Northwestern Negev Desert, Israel. J. Arid Environ., 29, in microalgae and cyanobacteria: Chemical features, role 427–437. DOI: 10.1016/S0140-1963(95)80015-8 and enzymes and genes involved in their biosynthesis. In: Veste, M., Littmann, T., Friedrich, H., Breckle, S.-W., 2001. Borowitzka, M.A., Beardall, J., Raven, J.A. (Eds.): The Microclimatic boundary conditions for activity of soil lichen Physiology of Microalgae. Developments in Applied Phy- crusts in sand dunes of the north-western Negev desert, Isra- cology, Springer, Switzerland. pp. 565–590. DOI: el. Flora, 196, 465–474. 10.1007/978-3-319-24945-2_21 Wilske, B., Burgheimer, J., Karnieli, A., Zaady, E., Andreae, Rossi, F., Mugnai, G., De Philippis, R., 2018. Complex role of M.O., Yakir, D., Kesselmeir, J., 2008. The CO exchange of the polymeric matrix in biological soil crusts. Plant Soil, biological soil crusts in a semiarid grass-shrubland at the 429, 19–34. DOI: 10.1007/s11104-017-3441-4 northern transition zone of the Negev Desert, Israel. Bioge- Rossi, F., Potrafka, R.M., Garcia-Pichel, F., De Philippis, R., osci. Discuss., 5, 1969–2001. 2012. The role of exopolysaccharides in enhancing hydraulic Wood, M.K., Blackburn, W.H., 1981. Grazing systems: Their conductivity of biological soil crusts. Soil Biol. Biochem., influence on infiltration rates in the rolling plains of Texas. 46, 33–40. J. Range Manage., 34, 331–335. Rutin, J., 1983. Erosional processes on a coastal sand dune, De Xiao, B., Sun, F., Hu, K., Kidron, G.J., 2019a. Biocrusts reduce Blink, Noordwijkerhout. Publication 35 of the Physical Ge- surface soil infiltrability and impede soil water infiltration ography and Soils Laboratory, University of Amsterdam, under tension and ponding conditions in dryland ecosystem. Amsterdam. J. Hydrol., 568, 792–802. DOI: 10.1016/j.jhydrol.2018.11.51 Sun, F., Xiao, B., Li S., Kidron, G.J., 2021. Towards moss Xiao, B, Sun, F., Yao, X., Hu, K., Kidron, G.J., 2019b. Season- biocrust effects on surface soil water holding capacity: Soil al variations in infiltrability of moss-dominated biocrusts on water retention curve analysis and modeling. Geoderma, aeolian sand and loess soil in the Chinese Loess Plateau. 399, 115120. DOI: 10.1016/j.geoderma.2021.115120 Hydrol. Process., 33, 2449–2463. DOI: 10.1002/hyp.13484 Talbot, M.R., Williams, M.A.J., 1978. Erosion of fixed dunes Xu, C.-Y., Singh, V.P., 2001. Evaluation and generalization of in the Sahel, central Niger. Earth Surf. Process. Landf., 3, temperature-based methods for calculating evaporation. 107–113. Hydrol. Process., 15, 205–319. DOI: 10.1002/hyp.119 Tarchitzky, J., Banin, A., Morin, J., Chen, Y., 1984. Nature, formation and effects of soil crusts formed by water drop Received 24 June 2021 impact. Geoderma, 33, 135–155. Accepted 27 August 2021

Journal

Journal of Hydrology and Hydromechanicsde Gruyter

Published: Dec 1, 2021

Keywords: Biological soil crusts; Extracellular polymeric substances; Pore clogging; Hydrophobicity; Infiltration-excess overland flow; Water repellency

There are no references for this article.