Demography of threatened tree species in Vietnam P.D. Chien Demography of threatened tree species in Vietnam ISBN-10: 90-393-4407-8 ISBN-13: 978-90-393-4407-1 NUR 904 @ 2006 P.D. Chien Printed by: Print Partners Ipskamp, Enschede Cover design: Marjolein Kortbeek Photos: P.D. Chien All rights reserved. No part of this publication, apart from bibliographic data and brief quotations in critical reviews, may be reproduced, re-recorded or published in any form including photocopy, microfilm, electronic or electromagnetic record, without written permission. Demography of threatened tree species in Vietnam Demografie van bedreigde boomsoorten in Vietnam (met een samenvatting in het Nederlands) ðộng thái qu ần th ể các loài cây b ị ñe d ọa ở Vi ệt Nam (ph ần tóm t ắt b ằng ti ếng Vi ệt Nam) Proefschrift ter verkrijging van de graad van doctor van de Universiteit Utrecht op gezag van de rector magnificus, prof.dr. W.H. Gispen, ingevolge het besluit van het college voor promoties in het openbaar te verdedigen op woensdag 29 november 2006 des middags te 12:45 uur door Pham Duc Chien geboren op 15 september 1967 te Thai Binh, Vietnam Promotor: Prof. Dr. M.J.A. Werger, Utrecht University Prof. Dr. Nguyen Hoang Nghia, Forest Science Institute of Vietnam Co-promotor: Dr. P.A. Zuidema, Utrecht University The investigations reported in this thesis were carried out within the framework of the Tropenbos-Vietnam Programme and the Plant Ecology and Biodiversity Group at Utrecht University. This study was financially supported by Tropenbos International and the Forest Science Institute of Vietnam. To Ha and Duy Contents Chapter 1 General introduction 9 Chapter 2 Vietnamese forestry, biodiversity and threatened 19 tree species With M.J.A. Werger & N.H. Nghia Chapter 3 Conservation prospects for threatened Vietnamese 57 tree species: results from a demographic study With P.A. Zuidema & N.H. Nghia; submitted Chapter 4 Population viability analysis of threatened tree species 83 in Vietnam with P.A. Zuidema ; submitted Chapter 5 What dimension to use for matrix dimension of tree? 107 recommendations based on a validation of age estimate by tree ring analysis with P.A. Zuidema; submitted Chapter 6 General discussion and summary 125 Samenvatting (summary in Dutch) 137 Tóm t ắt k ết qu ả nghiên c ứu (summary in Vietnamese) 145 Acknowledgements 155 Curriculum vitae 157 Chapter 1 General introduction Forest status in the tropics Tropical forests are characterized by a very high plant diversity: covering less than 10% of the land areas, they posses more than 50% of all known plant species on earth (Wilson 1995, Mayaux et al. 2005). In a single ha of these forests, as many as 300 tree species can coexist (Gentry 1998b), although a large difference may occur between continents and regions (Givnish 1999, ter Steege et al. 2000). Yet, during the past decades, tropical forests have severely declined, with around 6 million ha lost and more than 2 million ha visibly degrading each year (Achard et al. 2002). The main causes for the loss of tropical forests are agricultural expansion, over-harvesting, development of plantations, mining operation, industry, urbanization and road building (Geist & Lambin 2002). As a result, an unknown, but large number of species has become extinct, while many others run the risk of extinction (Frankham et al. 2002, World Conservation Union ‘IUCN’ 2006). Among tropical areas, South- East Asia has the highest relative rate of deforestation (Achard et al. 2002, Brook et al. 2006), also is facing a serious problem of species extinction (Sodhi et al. 2004, IUCN 2006). Tropical forests in Vietnam Three quarters of Vietnam is composed of hills and mountains, which was originally covered by tropical forests (Trung 1998). Being a venue of plant species emigrated from three flora areas: the Himalaya-Yunnam-Guizhou flora in the North-West, the India-Myanmar flora in the West, and the Malaysia-Indonesian flora in the South and South-East, Vietnam harbours a very high number of plant species (Trung 1998, Chan et al. 1999, Lap 1999) (for details see Chapter 2). Nevertheless, due to many reasons, such as rapid changes in land use, over-harvesting and long wars, the forests of Vietnam have severely declined, both in quantity and quality (Dang et al. 2001, for details see Chapter 2). Consequently, many species of Vietnam run the risk of extinction (Nghia 2005), of which around 150 are critically endangered and vulnerable (IUCN 2006). As threatened tree species often occur in small and isolated populations (Ministry of Science, Technology and Environment ‘MSTE’ 1996, cf. Ouborg 1993), they are very vulnerable to local extinction due to demographic stochasticity or lack of genetic variation (Menges 1992; Lande 1993; Oostermeijer et al. 2003). On the other hand, tropical trees are often slow-growing, long-lived species, Chapter 1 taking a long time to reach the age of reproduction (Chambers et al. 1998, Fichtler et al. 2003, Laurance et al. 2004), and this makes it difficult to determine whether the population is growing or declining in size (Kwit et al. 2004). It is therefore necessary to carry out a demographic study for these species in order to decide on actions before they have declined below the critical level. The context of this study In this dissertation, a demographic study of six threatened tree species was carried out in four protected areas in Vietnam: Annamocarya sinensis and Parashorea chinensis in Cuc Phuong National Park, Calocedrus macrolepis and Manglietia fordiana * in Ba Vi National Park, Dacrydium elatum in Bach Ma National Park, and Pinus kwangtungensis in Hang Kia – Pa Co Nature Reserve. The status and distribution of the six species are presented in Chapter 3. The four protected areas are briefly described below. Figure 1 Location of four protected areas in Vietnam: Hang Kia – Pa Co Nature Reserve (1), Ba Vi National Park (2), Cuc Phuong National Park (3), and Bach Ma National Park (4). Ba Vi National Park Ba Vi NP is located in Ha Tay province (21°N, 105°E, Fig.1), about 50 km north- west of Ha Noi. Covering 12,023 ha, the Park includes low to middle high mountains, and is surrounded by plains. The climate in the region is characterized by an average precipitation of 2600 mm y -1, an average annual temperature of 23°C and a pronounced cold and dry season from November to March (Forest Technique and Science Association of Vietnam ‘FTSA’ 2001). The natural forests occur at altitudes * : Some scientists call it Manglietia hainanensis , but we prefer the name Manglietia fordiana as Manglietia hainanensis is conspecific with Manglietia fordiana (Liang 10 & Nooteboom 1993). General introduction above 600 m above sea level (a.s.l.), but not at lower elevation due to a long period of overexploitation and agricultural practice (FTSA 2001). The natural forests are very diverse in species and structure, and can be distinguished into three main types at increasing elevation: Tropical evergreen broad-leaved rain forests, Subtropical evergreen broad-leaved rain forests, and Subtropical evergreen broad-leaved and coniferous forests (FTSA 2001) The buffer zone of the Park is inhabited by 47,000 inhabitants of whom nearly half belong to ethnic minorities. Most local people are poor as their incomes are mainly derived from forests and poor practice of agriculture (FTSA 2001). Bach Ma National Park Bach Ma NP covers 22,030 ha in Central Vietnam (16°N, 105°E, Fig.1). Due to a complex terrain, the annual precipitation of the region strongly varies among places, ranging from 3000 in the lower parts to over 8000 mm yr -1 at altitudes above 700 m a.s.l., with the rainy season from September to February (FTSA 2001, Keo 2003). The average temperature in the rainy season is around 20 ºC compared to 25 ºC in the dry season (FTSA 2001). The Park has two main patterns of forests in relation to elevation. The evergreen tropical forest covers areas below 900 m of which around 2700 ha are considered intact forests, but the rest is secondary forest as a result of a long time of overexploitation and wars. From 900 m a.s.l. to the highest mountain (1450 m a.s.l.), there is evergreen subtropical forest (FTSA 2001, Keo 2003) There are more than 63,000 inhabitants living in the buffer zone of the Park, and most of them are King People. The main incomes of the inhabitants are from agriculture and forest products. Their standard of living is in general very low (FTSA 2001). Cuc Phuong National Park The Park is located on the boundary intersection of three provinces: Hoa Binh, Ninh Binh and Thanh Hoa (20°N, 105°E, Fig.1). Its area is 22,200 ha. The average elevation of the Park is from 300-400 m, while the peak (May Bac) reaches to 648 m a.s.l. (Thu & Can 1999). The climate of the region is characterized by an average annual temperature of 21°C, and the average rainfall of 2150 mm y -1. Most the rainfall falls in the summer, from March to November (FSTA 2001). Three main types of the forests can be distinguished in the Park (FSTA 2001). The forests covering the valleys and foot hills are characterized by 3 layers of tree species, a layer of shrubs and a layer of fern and grass. The forests on mountain slopes include 2 layers of tree species and 1 layer of shrubs. The forests at the top of mountains have only two distinct layers: a layer of small tree species and shrubs, and the under storey. 11 Chapter 1 There are more than 50,000 inhabitants living in the buffer zone of the Park, and most of them are ethnic minorities.