Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Master → Kenya → 2008 → Bryodiversity of Mount Marsabit forest and bryophytes mist trapping ability assessment

University of Nairobi (2008)

Bryodiversity of Mount Marsabit forest and bryophytes mist trapping ability assessment

Muchura, Henry Mwangi

Titre : Bryodiversity of Mount Marsabit forest and bryophytes mist trapping ability assessment

Auteur : Muchura, Henry Mwangi

Université de soutenance : University of Nairobi, Kenya

Grade : MSc 2008

Mt. Marsabit forest is isolated by semi desert and desert, with vegetation ranging from scrubland at the base to tropical rain forest at the peak. The forest has abundant pendant bryophyte cover at the peak. The mountain rises from 950 m. asl. lowland of to 1750 m. asl., ruling out the possibility of the forest supported by underground water. The annual rainfall of 1,000 mm received by the forest is not enough to support the tropical rain forest at the peak. The forest experiences consistent mist throughout the year. The development of a forest in a situation where water is a limiting factor to community development inspired this study. The forest is currently threatened by invasive species e.g. Caesalpinia decapetala, Lantana camara, Eucalyptus spp., Senna spectabilis, Ocimum suave, in addition to other anthropogenic activities. The objectives of this study were to assess the diversity of bryophytes in Mt. Marsabit forest, collect bryophyte specimens and assess the role of bryophytes in mist water trapping for forest community development. To achieve this, the forest was studied through 3 windows transects, and in quadrats 400 m. x 400 m., 26 quadrats were randomized for study. Within each quadrat, nine sample stations were sited. The first sample point ’was located at the centre of the quadrat, while , two more sample points were located 50m and 100m away from centre point. This was repeated in the four compass directions. Bryophyte cover assessment was done using 25cm x 25cm quadrat. Data collection involved bryophytes specimen collection for NAI , ..• herbarium. The mist traps of 5()cm x 50cm, sandwiched 300g of bryophytes between wires, were set up at 1450 m. asl., on the windward side. On the same site, stem simulates of circumference 20 em, 35 em, and 53cm, dre sedall round with Meteoriaceae moss, were also set. The ·water retention capacity of _bryophytes was assessed, by spraying water on naturally occurring mats of Meteoriaceae and Frullania angulata, for 30 minutes, then placed on wires until dripping stopped then weighed. The hygroscopic capacity was assessed by oven drying the moss at 80 .C for 4 days, and weighed hot. The dried moss was kept in a room at 20 . C and 70 % relative humidity for 4 days and weighed. The species diversity is high on Mt. Marsabit forest, with high altitude quadrats recording the highest diversity. This study found 93 species of bryophytes with 51 mosses species in 30 moss families, 39 liverwort species in 13 liverwort families and 1 species of Anthocerotae and 81 new entries for the northern semi arid region of Kenya (K1). The mist water collected in trap reservoir was 1 - 2 liters of water per meter squared per mist day, conformed to results in Atacama Desert. The bryophytes water (intercept) retention capacity of 6.8 liters of water per meter squared per day, which is more than 600 times its own dry weight. The total amount of mist water trapped by a hectare of bryophytes is 70,000 liters each mist day. Working with a conservative figure of one misty day a week, a hectare of bryophytes trap more than 4.5 million liters annually. The small branches use less than half of their surface area to trap more mist water than the large stems, with an average of 1000 ml of water per meter squared per mist day. Hygroscopic capacity assessment showed a weight gain of 13 % of both Meteoriaceae and Frullania angulata dry weight. The results give evidence that mist water is important compensation factor that have supported development of Mt. Marsabit forest community. Considering mist water trapped by bryophytes, epiphytes, tree stems, branches and leaves, more water resource is availed to the forest community than is evident by conventional methods of measuring physical climatic parameters. It is the,mist water trapped by bryophytes and vegetation that is the compensation factor, which maintain Mt. Marsabit forest community. The mist water can be trapped and availed to community outside the forest, as a way to conserve Mt Marsabit forest. The phenomena apply to many high ,altitude forests, particularly mist forests.

Mots clés : Ecology / Forest / Mount Marsabit Forest, Kenya


Page publiée le 23 septembre 2010, mise à jour le 19 mars 2018