Population structure and growth of the fern Rumohra adiantiformis in relation to frond harvesting in the southern Cape forests

Demography, phenology and experimental harvesting of the fern Rumohra adiantiformis (G. Forst.) Ching were studied as a basis of sustained commercial frond harvesting from indigenous forest. The fern grows densely and produces large fronds on moist, well-drained sites. Numbers of frond buds peak during spring, and mature utilizable fronds in late summer. Growth rates for frond development stages varied with season. The period from the bud stage to mature utilizable fronds averaged 16 weeks. The mature stage lasted 10–18 weeks during summer. Picking of all mature fronds on a 22-week cycle over 3 years reduced frond size to 51% of the controls and on a 4,3-week cycle to 24%. Density of buds and mature fronds was significantly reduced by picking. Reduced frond size and density, and production of malformed fronds are attributed to depletion of the potassium and phosphorous reserves in the plant. Decreased harvest intensity, longer harvest cycle, improved monitoring and future research are recommended for better resource conservation. Guidelines are provided for cultivation of the fern. Demografie, fenologie en eksperimentele benutting van die varing Rumohra adiantiformis (G. Forst.) Ching is bestudeer as basis vir standhoudende kommersiële varingbenutting uit inheemse woud. Die varing groei dig en vorm groot blare op vogtige, goed-gedreineerde groeiplekke. Die getal blaarknoppe bereik ‘n piek gedurende die lente en volwasse blare ‘n piek in die laatsomer. Groeitempo van die blaarontwikkelingstadia varieer volgens seisoen. Die gemiddelde periode vanaf die knopstadium totdat die blaar volwasse en benutbaar is, is 16 weke. Die volwasse stadium duur 10–18 weke in die somer. Die pluk van alle volwasse blare oor 3 jaar het met ‘n 22-week-siklus die blaargrootte tot 51% van die kontrole verminder, en met ‘n 4,3-week-siklus tot 24%. Digtheid van knoppe en volwasse blare is betekenisvol verminder deur benutting. Verminderde blaargrootte en -digtheid, en vorming van abnormale blare word toegeskryf aan ‘n uitputting van die kalium- en fosfaatreserwes van die plant. Verlaagde plukintensiteit, ‘n verlengde pluksiklus, verbeterde monitering en verdere navorsing word aanbeveel vir beter bewaring van die hulpbron. Riglyne word voorsien vir die kweek van die varing.