Biological and microbial activity in biological soil crusts from the Tabernas desert, a sub-arid zone in SE Spain

Abstract

The ecology and functional role of biological soil crusts (BSCs) in arid and semi-arid zones have been extremely well studied. However, little is known about the biochemical properties related to the number and activity of the microbiota that form the crusts, even though information about these properties is very important for understanding many of the processes that affect the formations. In this study, several properties related to the activity and number of microorganisms (biomass-C, basal respiration, dehydrogenase activity and nitrogen mineralization potential) were determined at different depths (crusts, 0-0.5 cm; middle, 0.5-3 cm and deep, 3-5 cm layers) in two types of crusts (predominated by cyanobacteria and by lichens) in the Tabernas desert (Almeria, SE Spain). The absolute values of the above-mentioned properties and the values expressed relative to the total organic carbon (TOC) content were both much higher in the crust layers than in the surface horizons of soils under Mediterranean or Atlantic climates. A large part of the TOC in the BSCs was contained in the microbiota and another large part was readily metabolized during incubation of the crusts for 10 days at 25 °C. The net nitrogen mineralization rate was also high, and ammonification predominated in the crust layers, whereas nitrification predominated in the middle and deep layers. In all types of BSCs, the microbiota colonized the deep layers, although with greater intensity in the lichen-dominated BSCs than in the cyanobacterial BSCs. The results also indicate that hydrolytic enzymes are not stabilized on soil colloids and their activity depends only on the active microbiota.

Differences in thallus chemistry are related to species‐specific effects of biocrust‐forming lichens on soil nutrients and microbial communities

“…; Miralles et al . , ). For example, species such as D. diacapsis were positively related to variables from the C cycle, but had a negligible effect on the availability of both inorganic and organic P (Fig.…”

“…; Miralles et al . , ). Communities dominated by mosses, lichens, microalgae and cyanobacteria (biocrusts hereafter) constitute a key biotic component from boreal, arctic, temperate and dryland ecosystems world‐wide, where they play major roles in controlling ecosystem structure and functioning (Belnap & Lange ; Lindo & Gonzalez ).…”

“…For example, Miralles et al . (, ) showed that soils under late‐successional lichen species such as Diploschistes diacapsis and Lepraria crassissima have a higher soil respiration, enzyme activities and inorganic N concentrations than those located under cyanobacteria. Similarly, Concostrina‐Zubiri et al .…”

Biocrusts in the Context of Global Change

“…Drylands are strongly constrained by nutrient availability, and biocrusts are known to significantly affect nutrient inputs and cycling (e.g., Belnap 2002;Reed et al 2012;DelgadoBaquerizo et al 2013b). Recent research indicates that the effects of biocrusts on nutrient pools and cycles are species specific (Bowker et al 2011;Miralles et al 2012Miralles et al , 2013Delgado-Baquerizo et al 2015), as typically found with vascular plants (e.g., Bardgett et al 1999). Thus, the effects of warming could significantly alter nutrient cycling and availability via changes to biocrust community composition and activity (Hu et al 2014).…”

Capacity of biological soil crusts colonized by the lichen Diploschistes to metabolize simple phenols

“…In the Desierto de Tabernas, the biocrusts colonized by Diploschistes diacapsis act as atmospheric C fixers and thus accumulate large quantities of total organic C (Lázaro et al 2008). However, they also possess a strong catabolic capacity as indicated by high microbial and respiratory coefficients (Miralles et al 2012b), which suggests a high content of labile C. In fact, it has been found that the total labile C in the surface layers (0-0.5 cm) of the DIPLOS biocrust represents about 40 % of the total organic C (Miralles et al 2013). In addition, these authors showed that under the moisture conditions most favourable for the metabolic activity of DIPLOS biocrusts (water content equivalent to 78 % of water retained at field capacity), most of the labile C was consumed during respiratory processes and used for microbial growth.…”