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Plant clusters govern soil microbiology in desert systems. Female Acanthosicyos horridus plants in the Namib Desert are preferentially accessed by grazers, especially during fruit availability. We hypothesized that this differential grazing affects the taxonomic diversity of soil bacterial populations. Sampling was carried out at three locations on a northwest-to-southeast transect starting at the Kuiseb Delta, near the shores of the Atlantic in the western Namib Desert, and extending inland over a distance of 140 km. Analyses of the soil samples showed that proximity to the sea had a strong impact on soil salinity. Soil pH and organic matter content were generally not significantly correlated with the presence or absence of plants and varied little and non-uniformly along the transect. A. horridus presence led to distinct under-canopy bacterial-community diversity in contrast with the non-vegetated spaces between shrubs. However, plant gender has only a marginal, statistically insignificant impact on the bacterial-diversity properties, thus not supporting our hypothesis. Therefore, the taxonomic diversity of the bacterial community in Namib Desert soils vegetated with A. horridus is primarily governed by the presence or absence of plants and by proximity to the ocean. [ABSTRACT FROM AUTHOR]

Changes in the soil labile C pools induced by vegetation rehabilitation on semiarid lands are assumed to correlate with changes in the microbial catabolic profiles. To verify this, soil was sampled under the canopies of 12-year-old (R12Y) and 30-year-old (R30Y) planted Caragana microphylla shrubs, as well as native C. microphylla shrubs, all located in the Horqin Sandy Land, China. Community Level Physiological Profiles (CLPPs) of soils were determined to reveal any qualitative and quantitative shifts in soil microbial catabolism linked with the revegetation process. water-soluble C (WSC) and hot-water extractable C (HWEC) were measured to indicate the availability of labile C pools. As the restoration proceeds, soil organic C (C org ) increased 2–3 times at the R30Y habitat compared to the R12Y habitat. The total utilization rate of the 15 C substrates also increased from 0.68 μg CO 2 -C g −1 soil h −1 at the R12Y habitat to 4.90 μg CO 2 -C g −1 soil h −1 at the R30Y habitat, but a slight decline in catabolic diversity, from 2.53 to 2.29, was recorded. Principal component analysis and redundancy analysis revealed that soil microbial communities colonizing the R12Y habitat exhibited an affinity to carbohydrates, which positively correlated to the relative concentration of WSC. Those colonizing the R30Y and native habitats mainly preferred carboxylic acids and 3,4-dihydroxybenzoic acid due to higher C org content and relative concentration of HWEC. [ABSTRACT FROM AUTHOR]

In xeric environments, organic carbon is provided by above and belowground plant-litter components. The plants also act as an aboveground physical barrier. Both these biotic and abiotic features contribute to ‘fertile-island’ formation. Fifty Hammada scoparia shrubs and 50 artificial plants were randomly marked at a study site. The latter allowed simulation of the physical (abiotic) impact of perennial-plant cover and thus allowed distinguishing between biotic and strictly abiotic impacts on under-canopy soil bacterial diversity in a desert ecosystem. Soils were collected monthly over one year from under canopies of H. scoparia and artificial plants, and from the control area between the shrubs. The presence or absence of real plants and seasonality was the main drivers of bacterial diversity in soils. Simple canopy cover, as offered by the artificial plants, induced non-significant shifts in the diversity of the dominant bacteria. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]