Lateral and longitudinal distribution of riparian vegetation along an ephemeral river in Namibia using remote sensing techniques

• Published in: Journal of arid environments 2020-10, Vol.181, p.104220, Article 104220
• Main Authors: Morgan, Bryn E., Bolger, Douglas T., Chipman, Jonathan W., Dietrich, James T.
• Format: Article
• Language: English
• Subjects: Ephemeral rivers; Namib Desert; Remote sensing; Riparian vegetation
• ISSN: 0140-1963; 1095-922X
• DOI: 10.1016/j.jaridenv.2020.104220

Ephemeral rivers are key features of desert ecosystems, providing shallow groundwater and occasional surface flow, but compared to perennial systems, the structure of riparian forests in ephemeral rivers and their interactions with the hydrologic regime are poorly understood. This study examines the distribution of riparian woody species in the ephemeral Kuiseb River in central Namibia. Unmanned aerial vehicle (UAV) and satellite imagery were used to examine the structure of the riparian forest across lateral and longitudinal gradients. Woody plant abundance peaked in the terminal alluvial zone, the reach of the river where floods typically run dry. The five dominant species exhibited similar spatial patterns at latitudinal and longitudinal scales. Faidherbia albida and Salvadora persica were found more proximal to the active channel and concentrated in the terminal alluvial zone. Acacia (Vachellia) erioloba, Euclea pseudebenus, and Tamarix usneoides were more evenly dispersed laterally across the riparian zone and along the river's longitudinal profile. These spatial patterns correspond to plant physiological properties of hydrological dependence and gradients of water availability and soil composition. The tight coupling of plant distributions with water availability highlights the need for long-term monitoring of ephemeral riparian vegetation in light of potential future changes to the global hydrologic regime. •The distribution of vegetation along the lower Kuiseb River was examined.•Overall woody species density was higher upstream and close to the active channel.•Two plant assemblages were found, consistent with species' physiological traits.