title: Water regime history drives responses of soil Namib Desert microbial communities to wetting events.
abstract: Despite the dominance of microorganisms in arid soils, the structures and functional dynamics of microbial communities in hot deserts remain largely unresolved. The effects of wetting event frequency and intensity on Namib Desert microbial communities from two soils with different water-regime histories were tested over 36 days. A total of 168 soil microcosms received wetting events mimicking fog, light rain and heavy rainfall, with a parallel "dry condition" control. T-RFLP data showed that the different wetting events affected desert microbial community structures, but these effects were attenuated by the effects related to the long-term adaptation of both fungal and bacterial communities to soil origins (i.e. soil water regime histories). The intensity of the water pulses (i.e. the amount of water added) rather than the frequency of wetting events had greatest effect in shaping bacterial and fungal community structures. In contrast to microbial diversity, microbial activities (enzyme activities) showed very little response to the wetting events and were mainly driven by soil origin. This experiment clearly demonstrates the complexity of microbial community responses to wetting events in hyperarid hot desert soil ecosystems and underlines the dynamism of their indigenous microbial communities.
authors.affiliation: Centre for Microbial Ecology and Genomics (CMEG), Genomic Research Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: Aline
authors.initials: A
authors.lastname: Frossard
authors.affiliation: Centre for Microbial Ecology and Genomics (CMEG), Genomic Research Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Ramond
authors.affiliation: 1] Gobabeb Research and Training Centre (GTRC), PO Box 953, Walvis Bay, Namibia [2] Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Mary
authors.initials: M
authors.lastname: Seely
authors.affiliation: Centre for Microbial Ecology and Genomics (CMEG), Genomic Research Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: Don A
authors.initials: DA
authors.lastname: Cowan
mesh_terms: D000704:Analysis of Variance; D001419:Bacteria / Q000378:metabolism*; D003889:Desert Climate; D005658:Fungi / Q000378:metabolism*; D006813:Humidity; D009276:Namibia; D012987:Soil; D012988:Soil Microbiology; D014867:Water
chemical_list: D012987:Soil; D014867:Water