Effect of Harvesting on Temporal Papyrus (cyperus papyrus L.) Population among Swamps of Winam Gulf in Lake Victoria Basin, Kenya

Abstract

Experiments were set to determine the effect of monthly and seasonal harvesting on temporal papyrus population density. Mean initial culm count was 21.6±2.26/m2. Initial culm counts varied across sites, but spatial differences were not significant. Mean monthly culm counts declined with successive harvests, and each sequential harvest significantly reduced culm counts. Seasonal culm counts were generally higher in unharvested than in harvested plots, and the differences were significant in Nduru (F=13.569; p<0.05). There were no culm counts differences within and among sites between initial and seasonally harvested plots. Overall, there were more culms in seasonal (32.3±3.34/m2) than in initial counts. It was found that culm counts do not depend on site, and that harvesting reduces culm counts. It is evident that seasonal harvesting does not affect culm counts. Leaving a papyrus crop stand unharvested for more than a season increases its culm count. Given that frequent harvesting reduces culm count, and considering that initial papyrus population densities were the lowest across sites, it may be concluded that Winam Gulf papyrus is harvested faster than the wetlands can replenish. This finding highlights the need for urgent conservation measures in the area. It is suggested that papyrus conservation steps be undertaken most urgently in Winam Gulf. A minimum-harvesting regime at the start is once per patch per season. However, fewer patches were studied relative to the entire swamps. A more elaborate assessment, covering larger areas and more swamps, with greater effort, should be undertaken to determine the replenishment break-even point.