Browsing by Subject "luonnontieteet, kasviekologia"

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  • Stam, Åsa (Helsingin yliopisto, 2020)
    Non-vascular epiphytes (bryophytes, lichens) play an important ecological role in tropical montane cloud forests. Bryophytes and lichens influence hydrological conditions in forest canopies by intercepting large amounts of water and, through evapotranspiration, helping to maintain high humidity long after precipitation has ceased. Despite their obvious ecological importance, also for insects and other animals, few experimental studies on their ecology have yet been done in the tropics. For the remaining cloud forests in East Africa, basic information on biomass distribution and growth potential is urgently needed to better understand the various roles of non-vascular epiphytes in these montane ecosystems. The aim of this thesis was to study responses of tropical non-vascular epiphytes to environmental factors. Because of their sensitivity to atmospheric conditions, changes in the forest environment can effect epiphytes in many ways. I studied such effects in the montane forests of Taita Hills, Kenya. I analyzed epiphyte growth and resilience experimentally with the help of pendant transplants and studied epiphyte colonization of artificial substrates in different forest environments. The transplant studies provided a wealth of data on the ecology of nonvascular epiphytes. This included novel information on the growth responses of several epiphytic bryophyte and lichen species and their relations to environmental factors. Probable effect of climate change on the non-vascular epiphytes were simulated by comparing transplant performance in moist upper montane forests and drier lower montane forests, respectively. Results also indicated that the absence of many non-vascular epiphytes from exotic tree plantations more likely reflects the lack of suitable substrates than differences in forest microclimate. We developed a new method for documenting epiphyte colonization with the help of plastic nets. The results revealed consistent differences in epiphyte cover, biomass and community composition between different types of forests. Finally, floristic observations contributed to overall knowledge of epiphyte diversity in the study area and led to the discovery of many epiphytic species that were new for the Taita Hills region.