The Philippine Agricultural Scientist Vol. 87 No. 1 (March 2004) 49 Fern Patch Structure and Species Diversity of Mt. Banahaw M.C.N. Banaticla and I.E. Buot, Jr. THE PHILIPPINE AGRICULTURAL SCIENTIST ISSN 0031-7454 Vol. 87 No. 1, 49-60 March 2004 FERN PATCH STRUCTURE AND SPECIES DIVERSITY ALONG THE ALTITUDINAL GRADIENT OF MT. BANAHAW DE LUCBAN, LUZON ISLAND, PHILIPPINES M. C. N. BANATICLA 1 and I. E. BUOT JR. 2 Portion of the M.S. thesis of the senior author. Supported by the Office of the Vice Chancellor for Research and Extension (OVCRE-UPLB), the Southeast Asian Ministers of Education Organization - Southeast Asian Regional Center for Graduate Study and Research in Agriculture (SEAMEO-SEARCA) and the National Research Council of the Philippines (NRCP). 1 Former Graduate Student, Institute of Biological Sciences, Graduate School, University of the Philippines Los Baños, College, Laguna 4031, Philippines (Corresponding author; e-mail: MCNBanaticla@hotmail.com); Current address: Genetic Resources Center, International Rice Research Institute, Los Baños, Laguna, Philippines 2 Associate Professor, Institute of Biological Sciences, University of the Philippines Los Baños, College, Laguna 4031, Philippines Key words: altitudinal distribution, ferns, Mt. Banahaw de Lucban, patch structure, pteridophytes, species diversity Abbreviations: GPS – geographic positioning system; SLPC – Southern Luzon Polytechnic College; PNH – Philippine National Herbarium; CAHUP – College of Agriculture Herbarium, University of the Philippines The line intercept method was used to determine fern patch structure and species diversity along the altitudinal gradient of the northeastern slope of Mt. Banahaw de Lucban, Quezon, Luzon Island, Philippines. A total of 93 species under 47 genera and 24 families were found in the study area, eight of which are Philippine endemics. The most represented families are Polypodiaceae (11 spp.), Hymenophyllaceae (11 spp.) and Aspleniaceae (9 spp.) while the most represented genera are Asplenium (9 spp.), Lycopodium (5 spp.) and Selaginella (5 spp.). Species diversity gradually increased with elevation, reaching a maximum at 814 – 886 m above sea level. Based on the result of stepwise multiple regression analysis, the slope was linearly related to species diversity, explaining 16% of the variation in H’ [H’ = 1.4928 + 0.0092(Slope); r = 0.3995]. On the other hand, there was no direct relationship between species cover and altitude. Majority of the fern patches sheltered all the pteridophyte height classes designated in this study. At least 85% of the pteridophyte species were preferential. Selaginella delicatula (Desv.) Alston, Selaginella cumingiana Spring, Cyathea callosa Christ, Sphaerostephanos hirsutus (Kunze ex Mett.) Hollt. var. hirsutus, Cephalomanes apiifolia (C. Pres.) K. Iwats and Cyathea philippinensis Bak. were the most widely adapted fern species along the slope. INTRODUCTION Mt. Banahaw de Lucban [1875 m above sea level (a.s.l.)] is one of the three peaks that form an isolated mountain mass traversing the provinces of Laguna and Quezon and forming the southwestern tip of the Sierra Madre moun- tain range in the Philippines. The other two peaks are Mt. San Cristobal (1470 m a.s.l.) and Mt. Banahaw (2140 m a.s.l.), the central and tallest peak which reportedly had its last volcanic eruption in 1730 (Adams 1910). This Banahaw–San Cristobal mountain complex is one of the 12 centers of plant diversity and endemism in the Philip- pines as recognized by the World Wildlife Fund/Interna- tional Union for the Conservation of Nature (WWF/IUCN) (Mittermeier et al. 1997). Ironically, there is limited lit- erature on its vascular and non-vascular flora. Further- more, a large portion of it is still relatively unexplored compared to Mt. Makiling, its more well-studied neigh- bor.