Cyanobacterial Diversity in Biological Soil Crusts along a Precipitation Gradient, Northwest Negev Desert, Israel

Abstract

Cyanobacteria occur worldwide but play an important role in the formation and primary activity of biological soil crusts (BSCs) in arid and semi-arid ecosystems. The cyanobacterial diversity in BSCs of the northwest Negev desert of Israel was surveyed at three fixed sampling stations situated along a precipitation gradient in the years 2010 to 2012. The three stations also are characterized by marked differences in soil features such as soil carbon, nitrogen, or electrical conductivity. The cyanobacterial biodiversity was analyzed by sequencing inserts of clone libraries harboring partial 16S rRNA gene sequences obtained with cyanobacteria-specific primers. Filamentous, non-diazotrophic strains (subsection III), particularly Microcoleus-like, dominated the cyanobacterial community (30% proportion) in all years. Specific cyanobacterial groups showed increased (e.g., Chroococcidiopsis, Leptolyngbya, and Nostoc strains) or decreased (e.g., unicellular strains belonging to the subsection I and Scytonema strains) abundances with declining water availability at the most arid, southern station, whereas many cyanobacterial strains were frequently found in the soils of all three stations. The cyanobacterial diversity at the three sampling stations appears dependent on the available precipitation, whereas the differences in soil chemistry were of lower importance.

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

“…The increase (p < 0.05) of C org , total nitrogen and fines (< 63 µm) from the southernmost to the northernmost sampling site is in accordance with Hagemann et al (2014) and Yair et al (2011). The maximum initial soil water content was found in N69 of 2.38 vol-% (Table 1).…”

“…Despite the close proximity and the uniform quarzitic sandy substratum in the region, crusts differ in their species composition, chemical and physical properties (Drahorad et al, 2013a;Drahorad and Felix-Henningsen, 2013;Kidron et al, 2010;Veste et al, 2001;Yair et al, 2011). The dune slopes and the interdune in NS are colonized by a cyanobacteria dominated BSC with the filamentous genera Microcoleus, Leptolyngbya and Trichocoleus as the most abundant (Hagemann et al, 2014;Karnieli et al, 1999). These BSCs are smooth, lightly gray colored, thin and fragile (1-2 mm thick) and correspond to the crust type A as classified by Kidron et al (2010).…”

“…Only on the north-facing dune slopes, where higher amounts of moisture are available thicker crusts (2-4 mm) with lichens or mosses of type C to E can be found (Kidron et al, 2010;Kidron and Benenson, 2014). Not only within the individual sites the crust types change according to the moisture regime but also along the precipitation gradient (Almog and Yair, 2007;Hagemann et al, 2014;Yair et al, 2011;Zaady et al, 2014). With higher amounts of available water in the interdunes of N84 and N69 BSCs of type C, D and E are more common.…”

“…The abundance of cyanobacterial strains like Microcoleus, Leptolyngbya and Trichocoleus decreases from the southern to the norther site, whereas the abundance of lichens like Collema tenax, Diploschistes diacapsis, Fulgensia fulgens, Squamarina cartilaginea, S. lentigera and mosses of the genera bryum sp. increases (Büdel and Veste, 2008;Hagemann et al, 2014;Veste et al, 2011). More lichens can be found in N84 and more mosses in N69.…”

“…The samples were taken from representative spots in the interdune of each site as close as possible to the infiltration area at the beginning of the dry season in 2012. Physico-chemical characteristics of the samples were determined as described in Hagemann et al (2014). Particle size analysis was conducted according to DIN ISO 11277.…”