The effect of wind-borne sand and salt spray on the growth of Scirpus nodosus in a mobile dune system

Much of the coastline along the eastern Cape consists of Shifting sand dunes with little vegetation cover. It was postulated that in the Kleinemonde River area Scirpus nodosus Rottb., a pioneering sedge of the dune slacks, was limited to this region of the dune system because of the effect of wind-borne sand and salt spray. This was tested by planting seedlings of S. nodosus at seven selected sites from the edge of the spring high water mark to the coastal scrub and monitoring their growth and corresponding environmental factors. Of the soil factors, a detrimentally high conductivity was recorded only on the foredunes. Salt spray had a deleterious effect on plant growth on the foredunes, Whereas sand movement was important along the entire profile; at some sites the only factor causing the death of plants. It appears that sand movement and low percentage soil moisture were the major factors preventing S. nodosus plants from becoming established throughout the dune system. Groot dele van die kuslyn langs die oos-Kaap bestaan uit bewegende sandduine met min plantegroeibedekking. Dit is aanvaar dat Scirpus nodosus Rottb., ’n pionier watergras van die tussenduin-holtes in die Kleinemonderivier gebied, beperk is tot ’n streek van die duinsisteem as gevolg van die effek van verwaaide sand en soutsproeireën. Saailinge van S. nodosus was uitgeplant op sewe uitgesoekte persele van die springty-hoogwatermerk tot by die kusstruikgewasse om die aanname te toets deur monitoring van hul groei en ooreenstemmende omgewingseienskappe. Van al die grondeienskappe was ’n nadelige hoër elektriese geleiding net op die voorduin bepaal. Soutsproeireën het ’n nadelige effek op plantegroei op die voorduine uitgeoefen, terwyl sandbeweging belangrik was langs die hele profiel en op sekere persele was dit die enigste faktor wat plant-mortaliteit veroorsaak het. Dit lyk asof sandbeweging en ’n lae persentasie vogligheid die belangrikste faktore is wat die vestiging van S. nodosus-plante dwarsdeur die duinsisteem verhinder.