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University of the Western Cape (2012)

Seasonal dynamics of edaphic bacterial communities in the hyper-arid namib desert

Armstrong, Alacia

Titre : Seasonal dynamics of edaphic bacterial communities in the hyper-arid namib desert

Auteur : Armstrong, Alacia

Université de soutenance : University of the Western Cape

Grade : Magister Scientiae – MSc 2012

Résumé
The Namib Desert is a hyper-arid, coastal desert with limited bioavailable water and nutrients ; characteristics which collectively impose constraints on edaphic microbial communities. Several studies in the Namib Desert have investigated changes in soil microbial communities across space. However, the temporal variation of edaphic bacterial community in response to seasonal microenvironmental variation in the Namib Desert gravel plains has never been investigated in situ.The edaphic bacterial community dynamics were evaluated over short (57 days) and long-term (1 year) sampling intervals using an extensive sampling strategy in combination with community fingerprinting by T-RFLP analyses and microenvironmental characterization. The short-term study was conducted on three distinct locations in the Namib Desert gravel plains. Soil bacterial communities were found to be more similar within habitats than between habitats, with the differences likely shaped by soil pH. These findings are consistent with the concept of habitat filtering.Investigation of edaphic bacterial communities over 1 year in an 8100 m2 sampling site revealed seasonal patterns of variation in community structure. Soil moisture,phosphorus, potassium and magnesium were identified as significant abiotic drivers of community temporal dynamics. β diversity was found to increase over time, while the environment remained relatively static. These findings support previous observations that desert communities are likely structured by stochastic and deterministic processes.Taken together, these findings advance understanding of temporal variation of edaphic communities in the Namib Desert.

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