The biology and ecology of doum palm (hyphaene compressa H wendl) a case study of Meru National park Kenya

Abstract

Down Palm (Hyphaene compressa) is an important multipw-pose tree of the Palmae fmml} ill•.,•. occurs in swamps and along water courses in the tropical dry lands from sea level up to 1400m a.s.l. It provides a variety of products and services of subsistence and commercial value to the communitiesin those areas. It is highly utilized and in some areas almost being overexploited for leaves and trunks. Despite its economic importance very little has been documented on its biology and ecology. This study therefore aimed to investigate the growth characteristics, regenerativepotential and the impact of disturbances on the population dynamics of Doum Palm in its natural habitat. The study was carried out in Meru National Park (MNP) where there is a large population of the species while germination experiment was done in a glasshouse at the KEFRIheadquarters. Field data collection took place between August and December 2003. Four sites were selected for the study in the park and included Murika and Bisanadi in the swamp, Rojeweroalong the river line and Murera outside the park boundary. Transect lines were laid in each site and square plots of 20 m by 20 m established at regular intervals of 20 m apart. A total of 111 plots were established in all the sites. In each plot, all palm seedling, saplings and trees werecounted. The Dbh and heights were measured and sex noted for all palm trees. Disturbances and the possible causes were assessed. The germination experiment involved subjecting three categoriesof seeds (i.e. whole fmits, depulped fmits and extraCted seeds) to three treatments and a control. Treatments involved soaking in water for 10 days, scarification by immersing in 90% concentrated H2S04 for 10 minutes (extracted seeds) and for 30 minutes (depulped fruits) and coveringin ~ grass and burning for 10 minutes. The experiment took 150 days from July 2nd to November 29 , 2004. Data were analyzed using Microsoft excel and SPSS computer software. The parameters that were analyzed included density, size classes (ubh and height) and sex distribution. Seed germination data were analyzed using GenStat version 6.1 computer software. Natural regeneration was found to take place very wen judging from the relatively high mean seedling density (838.96±92.22) in all the sites. However the relatively low density of saplings and trees suggested that there were interruptions in the recruitment process. ANOVA for mean densityshowed no significant difference (P>O.05)in seedling density while there were significant differences (P<0.05) for saplings and trees among the sites. The sex distribution pattern in the entire population comprised of 37 males, 26 females and 34 unknown (young trees) with an overall male: female ratio of 1.4:1. ANOVA for mean percentage germination showed a highly significant difference (P<O.OOl)between the treatments. Extracted seeds recorded the highest germination ranging from 56% to 78% while whole fruits had the lowest, ranging from 17% to 28%. Results have also shown that Doum Palm seeds take 115 days to germinate after the roots has grown to a depth of slightly over 60 cm. For better results the bare nuts/seeds should be extracted from the ripe freshly collected fruits before sowing. The study has also revealed that disturbances associated with herbivory by wildlife and frequent fire outbreak were important ecological factors that influenced the population structure of Doum Palm woodlands in Meru National Park.