Although dunes are often seen flying a sand-plume pennant from their crests, (image below) the sand-sea of the western Namib has dunes stable enough for grass to prosper. While the dune sea does not have the soil chemistry to support the large variety of grass species which occur inland, one species does however stand out: Stipagrostis; particularly sabulicola although Stipagrostis seelyae and Stipagrostis ciliate also occur.
(Image above: the massive star dunes of the southern Namib, Wild Horses Safari 2018)
Where wind direction is variable, and blasting south-Atlantic gales do not reach far enough inland, we find these sleeping giants - the massive star dunes of the central Namib. Stable enough to be colonised by Stipagrostis and other woody vegetation such as Trianthema hereroensis. These plants give shelter to desert-adapted creatures which in turn bring in small predators and so the circle of life flourishes even in these extremely arid environments.
Requiring a good shower of rain to stimulate growth from the existing seed-bank, Stipagrostis is often sustained from fog alone. Image left shows the condition of the grasses after several years of not receiving any rain at all, yet some of this grass still has nutritional value.
(Image left: Loose horses on our Wild Horses Safari negotiate the hummocks of Stipagrositis)
Using their shallow roots rather than their leaves to take up fog-water, the root systems extend some twenty metres from the plant and take up water from the fog-dampened sand. These grasses don’t occur beyond the coastal fog belt which extends some 60 - 100 km inland and occurs on over 100 days a year. (link to fog blog)
Namibia Horse Safari's Wild Horses Safari crosses 27 km of vegetated dunes - no mean feat on horseback! Stiragrostis is often referred to as the ‘mound building’ species and the images show the hummocky nature of mounds which over several km of dune sea