Ecology of Vascular Epiphytes in West African Rain Forest
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ACTA PHYTOGEOGRAPHICA SUECICA 59 EDIDI:r' SVENSKA VAXTGEOGRAFISKA SALLSKAPET Dick ohansson J Ecology of vascular epiphytes in West African rain forest Resume: Ecologie des epiphytes vasculaires dans la foret dense humide d' Afrique occidentale UPPSALA 1974 ACTA PHYTOGEOGRAPHICA SUECICA 59 Distributor: Svenska vaxtgeografiskasallskapet, Box 559, S-751 22 Uppsala, Sweden Dick Johansson ECOLOGY OF VASCULAR EPIPHYTES IN WEST AFRICAN RAIN FOREST Ecologie des epiphytes vas�ulaires dans la foret dense humide d' Afrique occidentale (French summary) Doctoral dissertation to be publicly discussed in the Botanical auditorium, Upp sala University, on May 2, 1974, at 10 a.m., for the degree of Doctor of Philosophy (according to Royal proclamation No. 327, 1969) Abstract The ecology of 153 species of vascular epiphytes (101 orchids, 39 pteridophytes and 13 others) in the Nimba Mts in Liberia is described. 29 species are recorded in Liberia for the first time including one new species, Rhipidoglossum paucifolium, Orchidaceae. Field characteristics, flowering periods and some pollinators of the orchids are also given. In high forest with the canopy 30 m or more above the ground, 50.4 % of the trees (phorophytes) 10 m or higher carried epiphytes, compared to 14.8% for the phorophytes in regenerating forest. The ratio between fern and orchid species was 1 :3 at 500-700 m alt. and 1:1 at 1000-1300 m. Most of the epiphytic species occupy a ± restricted part of the phorophyte, as judged by their occurrence in the five sectors in which the phorophytes were subdivided. Ten different epiphyte communities are recognized. Their floralcomposi tion and development are also described. Certain species of phorophytes, e.g. Heritiera uti/is, Lophira alata and Parinari excelsa generally carry an. abundance of epiphytes, while others, e.g. Anthocleista nobilis, Fagara. tessmannii and Terminalia invorensis are mostly devoid of epiphytes. Colonization by epiphytes begins late in the life of the phorophyte, which is indicated by the higher frequency of epiphytes on the larger specimens. The effect of the epiphytes on their phorophytes is reviewed and obser vations from Nimba and East Africa provided. The environmental in fluences on the occurrence of the epiphytes on the phorophytes are dis cussed. In addition, field observations and experiments concerning water economy microclimate, substrate properties and light intensities are presented. ISBN 91"-7210-059-1 (ISBN 91-7210-459-7) 136 pp. ACTA PHYTOGEOGRAPHICA SUECICA 59 EDIDIT SVENSKA V AXTGEOGRAFISKA SALLSKAPET Dick J ohansson Ecology of vascular epiphytes in West African rain forest Resume: Ecologie des epiphytes vasculaires dans la foret dense humide d' Afrique occidentale UPPSALA 1974 Suggested citation: Johansson, D., 1974, Ecology of vascular eopiphytes in West African rain fo rest. Acta Phytogeogr. Suec. 59. Uppsala. Doctoral dissertation at Uppsala University, Sweden 1974. ISBN 91-7210-059-1 (paperback) ISBN 91-7210-459-7 (cloth) ©Dick Johansson 1974 Svenska vaxtgeografiska sallskapet Box 559, S- 75 122 Uppsala, Sweden Technical editor: Gunnel Sjors Printed in Sweden 1974 Textgruppen i Uppsala AB Abstract Johansson, D. 1974, Ecology of vascular epiphytes in West African rain forest. (Resume: Ecologie des epiphytes vasculaires dans la foret dense humide d'Afrique occidentale.) Acta Phytogeogr. Suec. 59. Uppsala. 136 pp. The ecology of. 153 species of vascular epiphytes (10 1 orchids, 39 pteridophytes and 13 others) in the Nimba Mts in Liberia is described. 29 species are recorded in Liberia for the first time including one new species, Rhipidoglossum paucifolium, Orchidaceae. Field characteristics, flowering periods and some pollinators of the orchids are also given. In high forest with the canopy 30 m or more above the ground, 50.4 % of the trees (phorophytes) I 0 m or higher carried epiphytes, compared to 14.8% for the phorophytes in regenerating forest. The ratio between fe rn and orchid species was I :3 at 500-700 m alt. and 1: 1 at 1000-1300 m. Most of the epiphytic species occupy a ± restricted part of the phorophyte, as judged by their occurrence in the five sectors in which the phorophytes were subdivided. Ten different epiphyte communities are recognized. Their floral composi tion and development are also described. Certain species of phorophytes, e.g. Heritiera utilis, Lophira alata and Parinari excelsa generally carry an abundance of epiphytes, while others, e.g. Anthocleista nobilis, Fagara tessmannii and Terminalia invorensis are mostly devoid of epiphytes. Colonization by epiphytes begins late in the life of the phorophyte, which is indicated by the higher frequency of epiphytes on the larger specimens. The effect of the epiphytes on their phorophytes is reviewed and obser vations from Nimba and East Africa provided. The environmental in fluences on the occurrence of the epiphytes on the phorophytes are dis cussed. In addition, field observations and experiments concerning water economy microclimate, substrate properties and light intensities are presented. Content Preface 'herbs' 64, On dead trees 64, On rocks and soil 65 I. Introduction Distribution of epiphytes on the phorophytes 66 2 General notes on vascular epiphytes Ecological subdivision of the phorophyte 66, Distribution 2, Occurrence in various Recording and registration of epiphytes 69, Eco- families 2, Phylogeny 2, Properties 2, logical observations 72, General distribution Ecological subdivisions 4 pattern 75 Previous studies of vascular epiphyte ecology 5 Epiphyte communities 78 Scope of the present study 5 Terminology 78, Methods 79, Abundance 80, Epi- Field work 6 phyte communities at altitudes below 1000 m 80, Terminology 6 Epiphyte communities at altitudes above 1000 m The area of investigation 6 85, General observations 86 Climate 8 Epiphyte succession 86 Veg etation 13 Primary and secondary forest I 3, The Liberian Epiphyte succession in Himalayan Quercus forest rain forest 14, Classification of the forest 87, Succession indicated by floristic composi- 87, in the Nimba area 15, The phorophytes (the tion Succession traced by analysis of humus 87, 89 host trees) 17 deposits Effects of environmental changes Effects of the epiphytes on the phorophytes 91 If. The epiphytic flora Earl ier observations 91 Composition and geographical distribution 21 Indirect effects 9 I, Direct effects 92 List of species 23 Author's observations 93 Pteridophytes 23, Orchids 26, Other vascular The leafless orchids 93 epiphytes 41 V. Environmental influence Ill. Biology of vascular epiphytes Climate 95 Reproduction biology 43 Macroclimate 95, Microclimate I 00, Light inten- Flowering periods of orchids 43, Observa si ties 10 I, Daily variations in light intensity tions of orchid pollination 44, Diaspore 104 size and dispersal 45, Germination and establishment 45 Substrate 106 Life forms 46 Properties of the substrate and their influence Drought tolerance and drought avoidant on the epiphytes 106 epiphytes 47 The bark 106, Bark pH and the epiphytic flora Water economy 48 107, Exudates 108, Humus deposits 109, Corre- lation between substrate and epiphytic flora Water uptake 48, Storage of water 51, 110 Expenditure of water 53 Biotic factors 115 IV. The occurrences of epiphytes Human influence 115, Animal influence II5, Nut- Epiphytes on forest trees 55 ritionaJ importance of animals and microorga- 1. Total number of epiphytic species known 55, nisms 115 2. Quotient epiphytes/other vascular plants 55, VI. Distribution on the phorophytes 3. Percentage of tall trees carrying epiphytes 55, 116 4. Highest number of epiphytic species on one General pattern 116, Specific patterns tree 59, 5. Number of epiphytic specimens or Resume 121 'stands' on one tree 61 Epiphytes on other substrates 62 Literature 124 On cultivated trees 62, On tree-ferns 63, On Acta phytogeogr. suec. 59 Ecology of vascular epiphytes in West African rain forest 1 Preface My first contact with a tropical rain forest dates Many other Lamco employees have in one way or back to August 1964 when I commenced employ another helped or simplified my field work. ment for Lamco J.V. Op. Co. in Liberia. As a high Help and guidance in the determination of critical school teacher at the International school in Yekepa specimens have been received from Jean Bowden, I used my spare time during the following six years F.N. Hepper, Prances Jarrett, M. Sands and P. to explore the rain forest. In the vicinity of the newly Taylor of the Kew Herbarium, and from L. Garay of constructed Yekepa community, at 500 m altitude, the Oakes Ames Herbarium, Harvard Univ., Cam virgin rain forest covered the slopes of the Nimba bridge, Mass. Prof. Sanford, Univ. of Ile Ife, Nigeria, range up to the peaks at 1300 m altitude. The rain provided an unpublished manuscript on the use of forest was very poor in species in the field layer. On epiphytic orchids in general ecology work. the trees, however, vascular epiphytes were abun The determinations of the insects were performed dant and soon caught my particular interest. While by M.A. Grog an, S.L. Shute and I.H.H. Yarrow of trying to learn about the ecology of the epiphytes it the Entomological Dept. of the British Museum soon became evident that the literature on this sub (Natural History). ject was very scanty. Although the vascular epi Aina Aim, Gertie Backlund, Margareta Hellman phytes are a very characteristic floristic element in and Barbro Enander have typed the manuscript. the rain forest inaccessible growing sites have Miirta Ekdahl has prepared the large tables and resulted in few and often superficial reports on their Ulla-Britt Sahlstrom has copied the photographs. ecology. The map over the investigated area was drawn by After an introductory period in which to become Per Ake Soderman . acquainted with the tropical floraa preliminary plan In the preparation of the manuscript valuable for the future investigation was outlined in coopera criticism has been provided by Doe. Orj an Nilsson. tion with Prof. Hugo Sjors at the Institute of Dr Jerk Hellkvist at the Institute of Physiological Ecological Botany in Uppsala.