Life Zone Ecology of the Bhutan Himalaya
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LIFE ZONE ECOLOGY OF THE BHUTAN HIMALAYA Edited by M. OHSAWA Laboratory of Ecology, Chiba University 1987 Scanned from original by ISRIC - World Soil Information, as ICSU World Data Centre for Soils. The purpose is to make a safe depository for endangered documents and to make the accrued information available for consultation, following Fair Use Guidelines. Every effort is taken to respect Copyright of the materials within the archives where the identification of the Copyright holder is clear and, where feasible, to contact the originators. For questions please contact soil.isrictawur.nl indicating the item reference number concerned. Life Zone Ecology of the Bhutan Himalaya Published March 1987 Editor: Dr. M. Ohsawa, Associate Professor of Ecology Laboratory of Ecology, Faculty of Science, Chiba University 1-33, Yayoicho, Chiba 260, Japan Published with The financial support of the Grant-in-Aid for Scientific Research(Grant-in- Aid for Overseas Scientific Survey) of the Ministry of Education, Science and Culture of Japan. Project No. 60041009 and 61043007. CORRECTION 193 16-17 "To the contrary" should read "On the contrary". OHSAWA, M. VEGETATION ZONES IN THE BHUTAN HIMALAYA ITINERARY Page Line Fig. 2: in climate diagram below left, place name 312 6 "24: Dali( 1 500m;U:30)" should read "SHRBHANG" should read "SARBHANG". "24.: Nagor(7:45)-Dali(1500m;14:30)". 16-17 "Abies densa (in 52 plots) and Quercus griffithii (4.8)" should read: Abies densa (in 48 plots) and Quercus griffithii (46). Fig. 5: legend line 3, "upper(shaded) or lower limit" should read "upper or lower(shaded) limit". 19 Fig. 2: a box showing vertical range but missing species name should read "Bamboo". 37 25-26 "at around 1900 m on Mount Kerinci, Sumatra" should read "at around 1900 m". 58 Fig. 15: in the figure "CAINPÜR" should read "CHAINPUR". 60 Photo 25: legend line 3, "for trunk" should read "trunk for". NÜMATA, M. VEGETATION, PLANT INDUSTRY AND NATURE CONSERVATION IN BHUTAN 139 Photo 6: legend line 2, "marked ree" should read "marked tree". OKAZAKI, M. SOILS OF THE BHUTAN HIMALAYA 151 4 "amongthem" should read "among them". 157 Photo 5: legend "Umshelb" should read "Umshalbi". 159 15 "5-6 + 0.47" should read "5.6 + 0.47". 23 "us/cm" should read "us/cm". 27 "Alpinemeadow" should read "Alpine meadow". 32 "organiccarbon" should read "organic carbon". EGUCHI, T. TOPOGRAPHIC FEATURES IN THE CENTRAL PART OF THE BHUTAN HIMALAYA 192 26 "many" should read "mainly". 1 CONTRIBUTORS EGUCHI, Takashi Department of Geography, Faculty of Science, University of Tokyo, Hongo, Tokyo 113, Japan NUMATA, Makoto Shukutoku University, Daiganji, Chiba 280, Japan OHSAWA, Masahiko Laboratory of Ecology, Faculty of Science, Chiba University, Yayoicho, Chiba 260, Japan OKAZAKI, Masanori Laboratory of Soil and Aquatic Environment, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183, Japan TSUCHIDA, Katsuyoshi Laboratory of Nature Conservation, Faculty of Liberal Arts, Shinshu University, Matsumoto, 390, Japan PREFACE This is a preliminary report of our nature trekking in Bhutan, in 1985. Some of our members, Numata and Ohsawa had visited Bhutan in 1984, and were impressed very much with its nature. In 1985, the fol- lowing five members visited Bhutan to observe the nature of Bhutan on a wide scale. The members and their main field of study are as follows: Dr. M. Ohsawa, Leader, -Forest ecology Dr. M. Numata, -Weed and grassland ecology Dr. K. Tsuchida, -Grassland ecology Dr. M. Okazaki, -Soil science Dr. T. Eguchi, -Climatology Since 1963, Chiba University has been carrying out Himalayan studies in East Nepal under the leadership of Prof. Emeritus M. Numata. Four expeditions in 1963, 1971, 1977, and 1981, were all concentrated in East Nepal. The temperate vegetation of East Nepal is very similar to that of Japan as is understood by the fact that both of the regions are in the same floristic region, the Sino-Japanese region. Bhutan lies between East Nepal and Japan and if the distance also has some meaning to the similarity, Bhutanese vegetation may have more similarities with Japanese vegetation. Moreover the nature of Bhutan is still well preserved and we are able to obtain proper information about Himalayan vegetation. We are greatly indebted to the VIPs of Bhutan, Lyonpo Sangye Penjor, Dasho late Lam Penjor, Dasho C. Dorji, Dasho K. Letho, Dasho Dorji Tenzing, Dasho Tseten Dorji, and Dasho, K. Nishioka for their valu- able advice and help with our trekking. Also to Mr. Jigme Tshultim of Bhutan Tourism Corporation and his staff who helped us very much in many ways. We also thank to Y. Imaeda and T. Tsugawa who also helped us very much at Thimphu. We have a strong desire to cooporate with the Bhutanese people to study and conserve the last and most valuable Himalayan nature in Bhutan. I hope that this will promote future cooperation between the peoples of Bhutan and Japan. March 1987 Masahiko Ohsawa CONTENTS Preface Part I. VEGETATION AND CONSERVATION Vegetation Zones in the Bhutan Himalaya, by Masahiko Ohsawa j Grassland Vegetation and Succession in Central Bhutan, by Katsuyoshi Tsuchida 73 Observations of Farmlands and Pastures in Central Bhutan, by Makoto Numata 1 17 Vegetation, Plant Industry and Nature Conservation in Bhutan, by Makoto Numata 133 Part II. SOILS AND TOPOGRAPHY Soils of the Bhutan Himalaya, by Masanori Okazaki 145 Topographic Features in the Central Part of the Bhutan Himalayas, by Takashi Eguchi 185 Part III. CLIMATE Synoptic Analysis of Temperature, Precipitation and Moisture Conditions in the Bhutan Himalayas, by Takashi Eguchi 209 Synoptic- and Meso-analysis of Climatic Conditions in Bhutan from September through November in 1985, by Takashi Eguchi 249 Part IV. MISCELLANEOUS List of Plants collected in Bhutan, by Katsutoshi Tsuchida 281 Itinerary 305 Part I VEGETATION AND CONSERVATION M.Ohsawa(ed.), Life Zone Ecology of the Bhutan Himalaya.1987. Chiba University. VEGETATION ZONES IN THE BHUTAN HIMALAYA M. OHSAWA Laboratory of Ecology, Faculty of Science, Chiba University, Chiba 260, Japan ABSTRACT The vegetation zones in the Bhutan Himalaya are studied based on 363 plot data collected by plot sampling methods along the trekking route ranging from 100 to 5200 m in al- titude. About 90 dominant and co-dominant trees were iden- tified in all the forest plots. The three groups of dominant trees having different habitat requirements, i.e., mesic, xeric, and scree or ravine trees, are distinguished. The mesic dominants show a clear segregation of distribution along al- titudes, and are the climax dominants of respective zone. The xeric dominants are extrazonal in their distribution, and scree or ravine species are sporadic. Vegetation zones can be divided into six zones (five forest and one scrub) on the basis of higher frequency of distribution limits at certain altitudes. Floristic similarities of the dominant species composition in every 200 m altitudinal segments also show six clusters of forest types from lower to higher altitude; Tetrameles- Pterospermum-Phoebe type, Schima-Lithocarpus-Castanopsis type, Castanopsis-Quercus-Acer type, Tsuga-Picea type, and Abies type, and above forest limit, Rhododendron scrub type. These six zones correspond to the following climatic zones: tropical, subtropical, warm-temperate, cool-temperate, subarctic (cold-temperate, subalpine), and arctic (alpine) zone. The prin- cipal pattern of zonation is equivalent to that of East Nepal. -1- The six zones are further grouped into two pan-zones; i.e., 1) tropical pan-zone, including tropical, subtropical, and warm- temperate zones, and 2) temperate pan-zone, including cool- temperate, subarctic (cold-temperate), and arctic (alpine) zones. The boundary between two pan-zones at 2500 m corresponds to that of two floristic regions, Paleotropis and Holarctis, on the southern slopes of the Himalaya. In the Bhutan Himalaya, these two floristic regions are represented by contrasting life forms of principal dominants, i.e., evergreen broad-leaved trees in tropical pan-zone and conifers in temperate pan-zone. Within the temperate pan-zone, the equivalent forest zones between Himalaya and Japan are distributed under the similar tempera- ture conditions. But within tropical pan-zone, the similar tem- perature conditions between the Himalaya and Japan, flourish in different zonal forests. The vegetation in the dry valleys is a binding route for some common species both east and west of the Himalaya. INTRODUCTION The Bhutan Himalaya is the main part of the East Himalaya, which span ca. 700 km from Mount Namcha Barwa to the Tista river in Sikkim (Mani, 1973). The topography is composed of rather simple slopes facing south dissected deeply by seven big rivers flowing south, and in the middle part of these rivers, dry valleys are developed at different al- tiudinal ranges by valley. The land is covered by dense natural forests amounting to 64 % of the total land area (47000 sq. km). The percentage is similar to that of Japan, but the qualities of the forests are different in many respects. For example natural and semi-natural forests comprise more than 99 % of the total forested area of Bhutan (C. Dorji, 1983), while that of Japan is about 30 % of the forested area. Undoubtedly, such forest resources in Bhutan are valuable not simply as timber but through their vital functions of maintaining natural environment and human welfare. As has been discussed by many researchers since the pioneering -2- work by Hooker (1906), the Himalaya itself is the transitional region, be- tween tropical and temperate region of the northern hemisphere, and be- tween dry west and humid east of the south slope of the Himalaya (Schweinfurth, 1957; Troll, 1967; de Laubenfels, 1975; Meusel, 1971; Meusel and Schubert, 1971; Ohsawa et al., 1986; Ohsawa, 1987). Most of these discussions are based on research made in the Himalaya westward from Sikkim, except some research of the Assam Himalaya done by Indian scientists including some previous researches by British colonials.