title: Use of spatial analysis to test hypotheses on plant recruitment in a hyper-arid ecosystem.
abstract: Mounds originating from wind-blown sediment accumulation beneath vegetation (nebkhas) often indicate land degradation in dry areas. Thus far, most nebkha research has focused on individual plants. Here, we aimed to explore population-scale processes (up to scales of about 100 m) that might explain an observed nebkha landscape pattern. We mapped the Rhazya stricta Decne. population in a 3 ha study site in a hyper-arid region of Saudi Arabia. We compared the spatial patterns of five different cohorts (age classes) of observed nebkha host plants to those expected under several hypothesized drivers of recruitment and intraspecific interaction. We found that all R. stricta cohorts had a limited fractional vegetation cover and established in large-scale clusters. This clustering weakened with cohort age, possibly indicating merging of neighboring vegetation patches. Different cohort clusters did not spatially overlap in most cases, indicating that recruitment patterns changed position over time. Strong indications were found that the main drivers underlying R. stricta spatial configurations were allogenic (i.e. not driven by vegetation) and dynamic. Most likely these drivers were aeolian-driven sand movement or human disturbance which forced offspring recruitment in spatially dynamic clusters. Competition and facilitation were likely active on the field site too, but apparently had a limited effect on the overall landscape structure.
authors.affiliation: Plant and Vegetation Ecology (PLECO), Department of Biology, University of Antwerp, Wilrijk, Belgium.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Quets
authors.affiliation: Ecosystem Management, Department of Biology, University of Antwerp, Wilrijk, Belgium.
authors.forename: Stijn
authors.initials: S
authors.lastname: Temmerman
authors.affiliation: Department of Botany, Faculty of Science, Port Said University, Port Said, Egypt.
authors.forename: Magdy I
authors.initials: MI
authors.lastname: El-Bana
authors.affiliation: Department of Plant Production, College of Agriculture, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Saud L
authors.initials: SL
authors.lastname: Al-Rowaily
authors.affiliation: Department of Plant Production, College of Agriculture, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Abdulaziz M
authors.initials: AM
authors.lastname: Assaeed
authors.affiliation: Plant and Vegetation Ecology (PLECO), Department of Biology, University of Antwerp, Wilrijk, Belgium.
authors.forename: Ivan
authors.initials: I
authors.lastname: Nijs
mesh_terms: D029062:Apocynaceae / Q000502:physiology*; D003889:Desert Climate; D017753:Ecosystem; D006801:Humans; D008962:Models, Theoretical; D012529:Saudi Arabia; D062206:Spatial Analysis