The Distribution Of Two Major Plant Groups (bryophytes And Tracheophytes) Along An Altitudinal Gradient On Naro Moru Track, Mount Kenya.

Abstract

Tropical mountain forests are known as the cradle of flowering plants and have many archaic angiosperm taxa. However processes of climate change and human activities have resulted in massive degradation and loss of mountain biodiversity. In Mt. Kenya, human activities have caused the shifting of the forest base margin to higher altitudes, increased soil erosion with resultant increase in sedimentation of wetlands, rivers and water storage dams down steam posing serious and economic consequences. The presence of cryptogams are known to contribute to the good health of mountain ecosystems, however their composition, abundance and distribution in the face of the ongoing forest destruction in Mt Kenya is not clear. The aim of this study was therefore, to establish the taxonomic and ecological relationship between one group of cryptogams- the bryophytes and tracheophytes along an altitudinal gradient using Narumoru tract of the western slope of Mt. Kenya. Plants were sampled at an interval of 200m from 2400 to 4800m. The higher plants were sampled along a 50 m transect using 10m by 10 m plots while the bryophytes were sampled using 10 x5cm quadrats of the same plots where higher plants were collected. Fine-scale variations in bryophyte communities were investigated in nine microhabitats including the soil surface, humus layer, decaying lignin, stem trunks, rachises, rocks and water edges. All the specimens collected were identified in the field and later confirmed at the University of Nairobi (NAI) and National Museums of Kenya (EA) herbaria. Data analysis and descriptive and inferential measures of species diversity were done using SPSS computer program. The results showed that bryophytes had the highest diversity (50.6%) followed by angiosperms (47.3%), while gymnosperms had the lowest (1.3%). There was a general decrease in the plant species diversity from 2400m to 4600m asl, the optimum levels being at 2400 and 3000m asl (each containing over 350 species). At least five microhabitats were identified with the most diverse bryophytes being the humicolous and corticolous types (80%) while the least was aquatic (0.001%). It is hoped that data accrued from this study will aid in the conservation of the Mt Kenya mountain flora. The aim of this study was to establish the taxonomic and ecological relationship between bryophytes and tracheophytes along western slope of Mt. Kenya and this has been determined whereby the study revealed that NMT of Mt. Kenya harbors a high diversity of bryophytes and tracheophytes 81 and 83 in percentage it is 50 and 49 respectively. The study has also demonstrated that the diversity and distribution of bryophytes and the tracheophytes is influenced firstly by altitude and secondly by the microhabitats provided by natural features such as bogs, rocks and the tracheophytes themselves. Therefore, the taxonomic information of the less studied and less appreciated groups is essential in laying down the strategies to conserve Mt. Kenya.