Effects of Vineyard Agro-management Practices on Soil Bacterial Community Composition, and Diversity.

Changes in land use strongly affect soil biological and physico-chemical structure and characteristics, which are strongly related to agricultural conversion of natural habitats to man-made usage. These are among the most important and not always beneficial changes, affecting loss of habitats. In Golan Heights basaltic soils, vineyards are currently a driving force in land-use change. Such changes could have an important effect on soil microbial community that play an important role in maintaining stable functioning of soil ecosystems. This study investigated the microbial communities in five different agro-managements using molecular tools that can clarify the differences in microbial community structure and function. Significant differences in soil microbial community composition were found. However, no differences in alpha diversity or functionality were found between the treatments. To the best of our knowledge, this is the first report indicating that the bacterial community in different agro-managements provide an insight into the potential function of a vineyard system.

Plant Gender Affects Soil Fungal Microbiota Associated with Welwitschia mirabilis, an Unusual Desert Gymnosperm.

In a recent study, we found a distinct soil bacterial community associated with male and female plants of the desert gymnosperm Welwitschia mirabilis. In this subsequent study, we also found that the soil fungal community associated with Welwitschia differs between male and female plants, and between unvegetated areas and the soil under plants. Site location, pH, and soil moisture also had an important influence on the composition of the fungal community. A number of Ascomycota and Chytrid species were found to be distinct indicators of male and female plants, respectively, but there was no overall difference at the phylum level or in terms of diversity. The unvegetated areas between plants also differed in terms of several Ascomycota OTUs. Network connectivity of the fungal communities was found to be higher under both male and female Welwitschia plants than in unvegetated control areas. As with the bacterial community, it is unclear what processes produce the gender-distinct fungal community, and also the more general plant-associated community, and also what the effects on the biology of the plants are. One possibility behind the gender-related difference in fungal community is that there are differences in the production of pollen or nectar between the two plant genders, affecting the below-ground soil community.

A sensitive soil biological indicator to changes in land-use in regions with Mediterranean climate.

The demand for reliable indicators to quantify soil health has increased recently. We propose and test the use of soil microbial functional diversity as an indicator of multifunctional performance in agriculturally important areas. Agricultural fields in the Mediterranean and semiarid regions of Israel were selected as test sites and measured in Spring and Autumn seasons. Measurements included microbial parameters, basic soil abiotic properties and biological responses to agricultural management relative to measures of a natural ecosystem. Using a canonical correlation analysis we found that soil moisture was the most important basic soil property with different responses in Spring and Autumn. In Spring, it had a strongly negative relation with microbial biomass (MB), community level physiological profiling (CLPP) and the Shannon-Weaver index H', while in Autumn it had a strong relation with CLPP. We further show a significant interaction between CLPP and climate for land-use type "orchards". CLPP measured in the autumn season was thus identified as a useful and rapid biological soil health indicator, recommended for application in semiarid and Mediterranean agricultural regions. Apart from obtaining a better understanding of CLPP as the soil indicator, the study concludes that CLPP is well suited to differentiate between soils in different climates, seasons and land use types. The study shows a promising direction for further research on characterizing soil health under a larger variety of conditions.

Differential responses of ground-active arthropod abundance and diversity to shrub afforestation in heterogeneous textured soils in desertified grassland ecosystems, North China.

Shrub afforestation is an effective way for restoration of soil communities and desertification control in desertified regions. However, little is unknown about how heterogeneous textured soils influence the effectiveness of shrub afforestation on the activities and diversity of ground-active arthropods. In the present study, ground-active arthropods were examined by pitfall trapping as well as by herbaceous performances and soil properties investigated in two shrub microhabitats (the shrub canopy and open spaces) in afforested sandy soil and sandy loam soil of northwestern China. The adjacent shifting sandy land, not covered by shrub plantations, served as a control. Total abundance in the open spaces in afforested sandy soil was significantly (p < 0.05) higher than those in the shrub canopy microhabitats in the same soil type and was also higher than those in both shrub microhabitats (open space and shrub canopy) in afforested sandy loam soil. A consistently (p < 0.05) greater taxa richness and the Shannon index as well as taxa richness of trophic groups (phytophages and predators) was found in shrub microhabitats in both soil types compared to the shifting sandy land. However, no significant differences (p > 0.05) were observed in taxa richness, Shannon index, and the Simpson index of ground-active arthropods, and in the abundance and richness of both trophic groups among the four shrub microhabitats in both soil types. In conclusion, soil textural heterogeneity in terms of soil type had a significant effect on the abundance, but not on the biodiversity distribution and trophic relationship, of ground-active arthropods between shrub microhabitats. The facilitative effect of shrubs benefited a stable biodiversity distribution and thus a stable trophic relationship within ground-active arthropod communities through afforestation practices, regardless of soil type.

Polycyclic aromatic hydrocarbons (PAHs) in soils of an industrial area in semi-arid Uzbekistan: spatial distribution, relationship with trace metals and risk assessment.

The concentrations, composition patterns, transport and fate of PAHs in semi-arid and arid soils such as in Central Asia are not well known. Such knowledge is required to manage the risk posed by these toxic chemicals to humans and ecosystems in these regions. To fill this knowledge gap, we determined the concentrations of 21 parent PAHs, 4,5-methylenephenanthrene, 6 alkylated PAHs, and biphenyl in soils from 11 sampling locations (0-10, 10-20 cm soil depths) along a 20-km transect downwind from the Almalyk metal mining and metallurgical industrial complex (Almalyk MMC), Uzbekistan. The concentrations of Σ29 PAHs and Σ16 US-EPA PAHs were 41-2670 ng g-1 and 29-1940 ng g-1, respectively. The highest concentration of Σ29 PAHs occurred in the immediate vicinity of the copper smelting factory of the Almalyk MMC. The concentrations in topsoil decreased substantially to a value of ≤ 200 ng g-1 (considered as background concentration) at ≥ 2 km away from the factory. Low molecular weight PAHs dominated the PAH mixtures at less contaminated sites and high molecular weight PAHs at the most contaminated site. The concentration of Σ16 US-EPA PAHs did not exceed the precautionary values set by the soil quality guidelines of, e.g., Switzerland and Germany. Similarly, the benzo[a]pyrene equivalent concentration in soils near the Almalyk MMC did not exceed the value set by the Canadian guidelines for the protection of humans from carcinogenic PAHs in soils. Consequently, the cancer risk due to exposure to PAHs in these soils can be considered as low.

The 'fertile island effect' of Welwitschia plants on soil microbiota is influenced by plant gender.

Desert and semi-desert plants are often associated with a distinct soil biota under the plants and close to the root system. We aimed to understand if similar effects could be found in the taxonomically isolated desert gymnosperm Welwitschia mirabilis in the Namib Desert, and whether this island effect varied with climate and with gender of plants. We took soil cores adjacent to the plants in environments ranging from extreme desert to arid shrubland, and in nearby control sites between the plants. Soil chemistry was analysed, and deoxyribonucleic acid was extracted and sequenced for the bacterial 16s region. Soil under the plants was richer in organic C, N and moisture. Despite the range of climates, the soil around Welwitschia plants was consistently associated with a particular bacterial community composition that was distinct from samples further away. Compared to unvegetated control patches, bacterial diversity close to the plants was reduced. In the plant-associated soil community, there was a clear gender effect across all sites with a distinct community composition and greater diversity under male plants. It is unclear what differences in the soil environment might be producing these gender-associated differences, which provide an additional dimension to the fertile island effect.

Bacterial seed endophyte community of annual plants modulated by plant photosynthetic pathways.

Climate change is predicted to have adverse impacts on terrestrial ecosystems and uncertainties exist on how these systems will respond. Terrestrial plant ecosystems can be divided by how they fix atmospheric carbon- C3, C4 and CAM photosynthesis pathways. However, as for now, no clear answers could be given regarding the future global repartition of the C3, C4 and CAM plants. As seeds are the reproductive and dispersal unit of the plants and endophytes play a central role in their preservation; here it is suggested that a better knowledge regarding the seeds endophytic community is needed when studying the future repartition of C3, C4 and CAM plant seeds. Bacterial endophyte communities inhabiting seeds belonging to C3, C4 and CAM annual plants were analysed by culture-dependent methods and 16S rRNA gene sequencing. Results indicated there were differences in the relative abundance of bacterial phyla within and across all photosynthetic pathways. Indicating some level of niche partitioning, and each of the three photosynthetic pathways could be characterized by a specific endophytic composition of Firmicutes, corresponding to the adaptation capacity of each group. We successfully identified resistant species of endophytes in the Firmicutes phylum of C4 and CAM plant seeds. Those bacteria are known for being involved in thermal regulation and plant protection through enzymes and antibiotic synthesis and match the strong adaptation capacity of C4 and CAM plants. Overall, this study suggests that there is a plant-mediated selection of the seed microbiome and these symbionts could potentially confer additional benefits to the seed.

Sedimentary Marl mudstone as a substrate in a xeric environment revealed by microbiome analysis.

The sedimentary Marl mudstone soil is composed primarily of CaCO3, and is an important pedologic and geomorphologic element known as Marl, extensively dispersed in slopes and ridges in the northern Negev Desert, Israel. The wide Marl soil-layer areas are barren, with well-developed streamsides and no perennial vegetation cover. Soil systems in the Negev Desert have been widely studied, yet very little information was collected on Marl soils, and even less on the microbiome present in the Negev. Thus, an evaluation of the microbial-community inhabitants in a Marl soil layer was conducted in an attempt to distinguish between Marl with surface green mat and bare Marl soil layer. Our objective was to investigate the microbiome and abiotic components of the upper layer (0-5 cm) of Marl and Marl-with-green-mat soil collected in the Negev Desert. Plate-counting enabled the estimation of fungal and bacterial population size, while nested polymerase chain reaction (nPCR) and Ion Torrent sequencing were used to analyze biological diversity. The results indicate significant differences in microbial biomass and microbial-community diversity between Marl and Marl-green mat, despite similar pH levels. Further study is needed to enhance understanding of the activity of the biotic components and their contribution to slope stabilization.

Soil health assessment: A critical review of current methodologies and a proposed new approach.

The wellbeing of soils is crucial for securing food production worldwide. The soil health (SH) concept has been introduced due to an evolving understanding that soil is not just a growing medium for crops but that it provides a foundation for other essential ecosystem services (ES). The SH concept requires development of a holistic index for reliable and quantitative assessment of soil wellbeing related to the effects of different soil management practices and land uses. The aims of this paper are to: (1) review current approaches and methods to assess SH, (2) highlight the role of soil ES in characterizing soil function and (3) propose a new approach to assess SH via monitoring of ES provided by soils. We introduce a brief critical review of the following three main steps required for assessment of common SH indices: (1) selection of relevant attributes; (2) quantification and scoring approaches; and (3) integration of the selected attributes to construct the SH index. These steps usually include statistical or expert opinion-based approaches. In addition, we present a new approach that highlights the relevance and importance of soil ES, i.e., provisioning, regulating and supporting services that must be quantified for comprehensive assessment of soil functions and for fitting models that relate selected soil attributes to ES. This will allow practitioners and scholars to identify the most significant and universal attributes, quantify the relative contribution of each attribute to each ES, and subsequently assess the overall health of soils.

Bacterial community composition in costal dunes of the Mediterranean along a gradient from the sea shore to the inland.

Sand dunes are unique ecosystems with distinct features which limited the accumulation of biomass. The distance from seashore affects both the physical properties of the sand dunes and the biota living above- and below ground. The goal of the present study was to determine the effects of the distance from shore to inland on soil bacterial community composition during wet and dry season. We studied a chronosequence of sites close to the eastern Mediterranean coast. Bacterial diversity was assessed using directly extracted DNA from soil samples and 16 S ribosomal RNA gene fingerprinting. Our data indicates a significant influence of season and site on bacterial community structure. We showed that during the wet season soil organic matter, pH and salinity strongly influence bacterial community composition, whereas during the dry period bacterial diversity was mainly driven by the shortage of water at all sites. Consequently diversity was lowest during dry season at dunes close to the shore, whereas during the wet season the higher water content and the reduced salinity at the dunes which are more at the inland induced an increase in diversity, which illustrates the pronounced dynamics of microbial communities in soil over a season mainly at inland dunes.

Trends in Taxonomic and Functional Composition of Soil Microbiome Along a Precipitation Gradient in Israel.

The soil microbiome is important for the functioning of terrestrial ecosystems. However, the impacts of climate on taxonomic and functional diversity of soil microbiome are not well understood. A precipitation gradient along regional scale transects may offer a model setting for understanding the effect of climate on the composition and function of the soil microbiome. Here, we compared taxonomic and functional attributes of soil microorganisms in arid, semiarid, Mediterranean, and humid Mediterranean climatic conditions of Israel using shotgun metagenomic sequencing. We hypothesized that there would be a distinct taxonomic and functional soil community for each precipitation zone, with arid environments having lower taxonomic and functional diversity, greater relative abundance of stress response and sporulation-related genes, and lower relative abundance of genes related to nutrient cycling and degradation of complex organic compounds. As hypothesized, our results showed a distinct taxonomic and functional community in each precipitation zone, revealing differences in soil taxonomic and functional selection in the different climates. Although the taxonomic diversity remained similar across all sites, the functional diversity was-as hypothesized-lower in the arid environments, suggesting that functionality is more constrained in "extreme" environments. Also, with increasing aridity, we found a significant increase in genes related to dormancy/sporulation and a decrease in those related to nutrient cycling (genes related to nitrogen, potassium, and sulfur metabolism), respectively. However, relative abundance of genes related to stress response were lower in arid soils. Overall, these results indicate that climatic conditions play an important role in shaping taxonomic and functional attributes of soil microbiome. These findings have important implications for understanding the impacts of climate change (e.g., precipitation change) on structure and function of the soil microbiome.

The influence of flint stones on a soil microbial community in the northern Negev Desert.

In the Negev Desert ecosystems, flint-stone cover on slopes acts as a barrier against water flow. As a result, soil moisture increases and organic matter accumulates under the stone and in the immediate surroundings, both affecting the duration of soil microbial activity. On the other hand, during the dry season (characterized by approximately 210 dew nights), flint-stone cover plays an important role in the formation of dew, which eventually trickles down beneath the stone, correspondingly enhancing biological activity. The present study examined the possible role of flint stones as hotspots for soil microbial-community activity and diversity. The results were compared with those obtained from the adjacent stone-free soils in the open spaces (OS), which served as controls. Microbial activity (respiration and biomass) and functional diversity were determined by the MicroResp™ method. In addition, estimates of genetic diversity and viable counts of bacteria and fungi [colony-forming units (CFUs)] were obtained. The soil was significantly wetter and contained more organic matter beneath the flint stones (BFS). As hypothesized, biological activity was enhanced under the stones, as described by CO2 evolution, microbial-community biomass functional diversity, and fungal phylogenetic diversity. BFS environments favored a greater range of catabolic functions. Taxa generally known for their stress resilience were found in the OS habitats. The results of this study elucidate the importance of flint-stone cover to soil microbial biomass, community activity, and functional diversity in the northern Negev Desert.

Desert Perennial Shrubs Shape the Microbial-Community Miscellany in Laimosphere and Phyllosphere Space.

Microbial function, composition, and distribution play a fundamental role in ecosystem ecology. The interaction between desert plants and their associated microbes is expected to greatly affect their response to changes in this harsh environment. Using comparative analyses, we studied the impact of three desert shrubs, Atriplex halimus (A), Artemisia herba-alba (AHA), and Hammada scoparia (HS), on soil- and leaf-associated microbial communities. DNA extracted from the leaf surface and soil samples collected beneath the shrubs were used to study associated microbial diversity using a sequencing survey of variable regions of bacterial 16S rRNA and fungal ribosomal internal transcribed spacer (ITS1). We found that the composition of bacterial and fungal orders is plant-type-specific, indicating that each plant type provides a suitable and unique microenvironment. The different adaptive ecophysiological properties of the three plant species and the differential effect on their associated microbial composition point to the role of adaptation in the shaping of microbial diversity. Overall, our findings suggest a link between plant ecophysiological adaptation as a "temporary host" and the biotic-community parameters in extreme xeric environments.

Successive development of soil ecosystems at abandoned coal-ash landfills.

The main goal of the present study was to determine the effect of the native vegetation on the successive development of the soil ecosystem at abandoned coal-ash landfills of the Angren coal-fired power plant in Uzbekistan. Two different landfills (one not in use for 3 years, termed newer, and the other not in use for 10 years, termed older) with different degrees of vegetation cover were chosen to assess the time and vegetation effects on soil biota and habitat development. The soil biotic structure, including soil microorganisms and soil free-living nematode communities, was investigated both at open plots and under different native plants at the coal-ash landfill area. The observed soil microorganisms were found to be the most important component of the observed ecosystems. Total abundance, biomass, species, trophic and sexual diversity of soil free-living nematodes, along with fungi and organic-matter content, were found to be correlated with trace metals. The nematode trophic and species abundance and diversity increased from the newer toward the older coal-ash landfills. The sex ratio of the nematode communities was found to be dependent on the environmental conditions of the study area, with the males being the most sensitive nematode group. All applied ecological indices confirmed that open landfill plots distant from plants are the most unfavorable areas for soil biota. In that respect, the native plants Alhagi maurorum Desv. and Tamarix sp. were found to be important environmental components for the natural remediation of a soil ecosystem in the coal-ash landfill area.

Coupling geochemical, mineralogical and microbiological approaches to assess the health of contaminated soil around the Almalyk mining and smelter complex, Uzbekistan.

This study describes the impact of airborne pollution resulting from mining and smelting activities on the soils of the Almalyk mining and industrial area (NE Uzbekistan). Samples were collected along a transect downwind of the industrial area. Enriched contents of some metals were found in the upper soil layers near the metallurgical complex (Zn≤3010 mg kg(-1), Pb≤630 mg kg(-1), Cd≤30 mg kg(-1)) which suggests that these metals were derived from local stack emissions. The morphology and internal microstructure of metal-bearing spherical particles found in the heavy mineral fraction suggest that these particles were probably a result of inefficient flue gas cleaning technique of the smelter. The highest metal concentrations were found also in soil solutions and exchangeable solid fractions from the first three locations, and decreased with increasing distance from the pollution source along transect. Thermodynamic equilibrium calculations suggest that the mobile metal pool in the contaminated soil is mainly controlled by dissolution of metal carbonates formed as weathering product of the metalliferous particles. The health of the microbiological soil ecosystem was assessed by measurements of basal respiration, nematode abundance, biomass-related C and N content, and microbial metabolic quotient qCO2. Significant correlations were found between the dissolved metal content and the microbiological health parameters, a negative one for Cmic/Corg ratio, and a positive one for qCO2. A negative correlation was found between the amount of nematodes and the metal contents suggesting that the contaminated soil has significant impact on the functioning of the microbiological community. A better understanding of the spatial variations in the whole ecosystem functioning due to airborne impact could be very useful for establishing suitable land use and best management practices for the polluted areas.

Microfungal-community diversity in Zygophyllum dumosum and Hammada scoparia root zones in the northern Negev Desert.

The soil dilution plate method was used to determine the influences of perennial shrubs on the species diversity and density of cultivable microfungal communities inhabiting the root zones of two perennial shrubs, Zygophyllum dumosum and Hammada scoparia, in the northern Negev Desert, Israel. Soil samples were collected under the canopies of shrubs and the open spaces between them (serving as control) from five depths (0-10, 10-20, 20-30, 30-40, and 40-50 cm) during the wet and dry seasons of 2010. Fifty-one species belonging to 31 genera were identified from Zygomycota, teleomorphic and anamorphic Ascomycota, including Coelomycetes. During the wet and dry seasons, 4-10 and 2-6 species were identified at different soil depths beneath perennial shrubs and in the open spaces, while the corresponding colony-forming units (CFUs) varied from 3071 to 27687 and from 3201 to 15247 g(-1) dry soil. More diverse microfungal communities were collected in the vicinity of perennial shrubs compared to the open spaces during the wet season, while a reverse trend was observed during the dry season. Further study is needed to provide insights into the correlation between compounds of litter and root exudates of perennial shrubs and microfungal-community structure by a combination of molecular and physiological tools.

Soil microbial diversity in the vicinity of desert shrubs.

Water and nutrient availability are the major limiting factors of biological activity in arid and semiarid ecosystems. Therefore, perennial plants have developed different ecophysiological adaptations to cope with harsh conditions. The chemical profile of the root exudates varies among plant species and this can induce variability in associated microbial populations. We examined the influence of two shrubs species, Artemisia sieberi and Noaea mucronata, on soil microbial diversity. Soil samples were collected monthly, from December 2006 to November 2007, near canopies of both shrubs (0-10-cm depth). Samples were used for abiotic tests and determination of soil bacterial diversity. No significant differences were found in the abiotic variables (soil moisture, total organic matter, and total soluble nitrogen (TSN)) between soil samples collected from under the two shrubs during the study period. No obvious differences in the Shannon-Weaver index, evenness values, or total phylogenetic distances were found for the soil microbial communities. However, detailed denaturing gradient gel electrophoresis (DGGE) clustering as well as taxonomic diversity analyses indicated clear shifts in the soil microbial community composition. These shifts were governed by seasonal variability in water availability and, significantly, by plant species type.

Structure-function relations of strigolactone analogs: activity as plant hormones and plant interactions.

Strigolactones (SLs) have several functions as signaling molecules in their interactions with symbiotic arbuscular mycorrhizal (AM) fungi and the parasitic weeds Orobanche and Striga. SLs are also a new class of plant hormone regulating plant development. In all three organisms, a specific and sensitive receptor-mediated perception system is suggested. By comparing the activity of synthetic SL analogs on Arabidopsis root-hair elongation, Orobanche aegyptiaca seed germination, and hyphal branching of the AM fungus Glomus intraradices, we found that each of the tested organisms differs in its response to the various examined synthetic SL analogs. Structure-function relations of the SL analogs suggest substitutions on the A-ring as the cause of this variation. Moreover, the description of competitive antagonistic analogs suggests that the A-ring of SL can affect not only affinity to the receptor, but also the molecule's ability to activate it. The results support the conclusion that Arabidopsis, Orobanche, and AM fungi possess variations in receptor sensitivity to SL analogs, probably due to variation in SL receptors among the different species.

Microbial functional diversity associated with plant litter decomposition along a climatic gradient.

Predicted changes in climate associated with increased greenhouse gas emissions can cause increases in global mean temperature and changes in precipitation regimes. These changes may affect key soil processes, e.g., microbial CO(2) evolution and biomass, mineralization rates, primary productivity, biodiversity, and litter decomposition, which play an important role in carbon and nutrient cycling in terrestrial ecosystems. Our study examined the changes in litter microbial communities and decomposition along a climatic gradient, ranging from arid desert to humid Mediterranean regions in Israel. Wheat straw litter bags were placed in arid, semi-arid, Mediterranean, and humid Mediterranean sites. Samples were collected seasonally over a 2-year period in order to evaluate mass loss, litter moisture, C/N ratio, bacterial colony-forming units (CFUs), microbial CO(2) evolution and biomass, microbial functional diversity, and catabolic profile. Decomposition rate was the highest during the first year of the study at the Mediterranean and arid sites. Community-level physiological profile and microbial biomass were the highest in summer, while bacterial CFUs were the highest in winter. Microbial functional diversity was found to be highest at the humid Mediterranean site, whereas substrate utilization increased at the arid site. Our results support the assumption that climatic factors control litter degradation and regulate microbial activity.

Vertical distribution of microbial community functionality under the canopies of Zygophyllum dumosum and Hammada scoparia in the Negev Desert, Israel.

Patchy desert shrubs magnify the horizontal heterogeneities of carbon source and nutrient availability in an arid ecosystem, significantly affecting the abundance and activity of the soil microbial community. Since each shrub species develops special ecophysiological adaptations to the extreme harsh desert environments, previous studies elucidated that the effects of perennial shrubs on microbial diversity are unequal. The aim of the present study, conducted in the Negev Desert, Israel, was to illustrate the vertical changes of soil microbial community functionality in the root zone of perennial shrubs. Soil samples were collected from the 0-50 cm depth at 10-cm intervals under the canopy of Zygophyllum dumosum, Hammada scoparia, and from the open spaces between them, in the wet and dry seasons. Soil moisture and organic matter exhibited a significant (P<0.001) plant and depth dependence. The mean basal respiration rates and microbial biomass in soils collected beneath perennial shrubs were relatively higher than the control during the wet season, however, a contrasting trend was observed at some soil depths during the dry season. Relatively high abundance and activity of aromatic and carboxylic acid utilizers were observed in the vicinity of perennial shrubs, and the values recorded during the dry season were generally higher than the corresponding values during the wet season. In addition, a "mirror effect" in vertical changes of the community-level physiological profile was observed between Z. dumosum and H. scoparia. This study demonstrated the stratification of the functional aspects in soils under the canopy of perennial shrubs, thus indicating that the scattered distribution of vegetation not only causes horizontal heterogeneities of the microbial community in an arid system, but also that the ecophysiological adaptations developed by xerophytes regulate the abundance and saprotrophic functionality of microorganisms in the root zone.