Examination of biotic and abiotic controls of soil bacterial diversity under perennial shrubs in xeric soils

• Plant and soil systems affect bacterial diversity beneath plant canopies.
• Vegetation cover provides organic matter to above- and below-ground parts.
• Vegetation cover also acts as a physical barrier.
• Both functions help determine soil-biotic and bacterial-community activity.
• Plant seasonality & biotic parameters affect bacterial diversity in arid soils.

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.