Transformation of degraded forests into semi-natural production forests in northern Thailand Inaugural Dissertation Faculty of Forestry Albert-Ludwigs-University Freiburg im Breisgau, Germany submitted by Timm Tennigkeit born in Darmstadt Freiburg im Breisgau 2000 II Abstract ABSTRACT Key words: Thailand; tropical deciduous forests; degraded; site index; improvement treatments; semi-natural production forest. This study focussed on the degraded Deciduous Dipterocarp-Oak Forests (DDF) in northern Thailand. The aim was to provide information on site and stand conditions and to propose and assess improvement treatments to transform these forests into semi-natural production forests. As a consequence of extensive exploitation and dramatic loss of forest cover, Thailand declared a nationwide logging ban in 1989. To halt ongoing forest destruction, by increasing the forest utilisation value, degraded forests have to be transformed into productive forests. The site research showed that the observed DDF on some sites originated from more productive forest types. For the first time, site productivity could be measured by stem section analyses on Vitex limoniifolia. In the research stands, stocking volume was low but the number of stems was high. Only few stems of large dimensions occurred and many of these were damaged. Regeneration seemed sufficient for transformation into semi-natural production forests. Based on the observed site productivity and stand conditions, improvement treatments were proposed and applied for this transformation. The economic feasibility of this approach was assessed: gross margins would be negative initially, however positive gross margins can be achieved in the future if timber of larger dimensions can be extracted. Taken together, the transformation of degraded DDF into semi-natural production forest as proposed and tested, proves to be a promising approach for forest protection by utilisation. III Acknowledgements ACKNOWLEDGEMENTS This study was conducted between November 1997 and March 2000, as part of the European-Thai-Forest-Project (ETFP) "Ecology and Sustainable Semi-Natural Silvicultural Management of Indigenous Forests in Continental Southeast Asia" (1994-1999), funded by the European Union. Additional funding was provided by a research fellowship of the State Baden-Württemberg (Landesgraduiertenförderung) and by the German Academic Exchange Service (Deutscher Akademischer Austauschdienst). First of all, I would like to thank my supervisor Prof. Dr. Jürgen Huss, Chair of the Silviculture-Institute and coordinator of the ETFP, for his guidance and enthusiasm for the research in Thailand and at the Institute in Freiburg. Above all I would like to thank: – Dr. Clemens Fehr for his support and assistance in Thailand, in dealing with the project administration in Freiburg and for valuable discussions and revisions of this thesis; – Dr. Horst Weyerhäuser for organisation of this research, providing contacts in Thailand and for valuable discussions and comments on this thesis; – My brother, Dr. Frank Tennigkeit for his encouragement during the final stages of this thesis and for valuable discussions and revisions. In Thailand, the study was supported by many friends and colleagues. Dr. Viroj Pimmannrojnagool, Director at the Royal Forest Department in Thailand, who provided continual assistance throughout the project. My friend Somchai Noangnuang, Head of the Silviculture Research Station No. 1 at Huai Som and his wife, for his courage and field support. John F. Maxwell for his invaluable taxonomic knowledge and help with species identification, as well as Dr. Stephen Elliott for helpful discussions. At Freiburg University, I appreciate the support of Prof. Dr. Heinrich Spiecker, Chair of the Institute of Forest Growth, Dr. Hans-Peter Kahle and Clemens Koch for providing assistance with stem disc preparation and analysis. I also would like to thank Philippa Allen for proof reading and Nele Rogiers for the final formatting, as well as many colleagues at the forest faculty and my family for their support. IV Abbreviations ABBREVIATIONS Study site abbreviations HR Huai Rai (main research area) HS Huai Som (main research area) PC Pa Cha Lua (research location used for site studies only) MN Mae Naa Baa (research location used for site studies only) HKK Huai Kha Kaeng, west Thailand, a relatively undisturbed forest - mentioned several times for comparison with the degraded forests investigated Other abbreviations used within the study CSEA Continental Southeast Asia DBH Diameter at Breast Height DDF Deciduous Dipterocarp-Oak Forests ETFP European-Thai-Forest-Project F-trees Future tree or potential crop tree FAO Food and Agriculture Organisation GDP Gross Domestic Product MDF Mixed Deciduous Forest NTFP Non Timber Forest Products PCA Principal Component Analysis RFD Royal Forest Department NODDF Not in DDF NOI No indicator value Index V INDEX 1 GENERAL INTRODUCTION AND PROBLEM STATEMENT .......................... 1 1.1 General Introduction.............................................................................................. 1 1.2 State of the World's tropical deciduous forests...................................................... 2 1.3 Secondary and degraded tropical deciduous forests .............................................. 3 1.4 Significance of Deciduous Dipterocarp-Oak Forest in Southeast Asia ................. 4 1.5 Forestry in Thailand............................................................................................... 4 1.5.1 General socio-economic characterisation ...................................................... 4 1.5.2 Forest types in Thailand................................................................................. 5 1.5.3 Forest utilisation in Thailand ......................................................................... 6 1.5.4 Forest Plantations........................................................................................... 7 1.5.5 Transformation of degraded forests into semi-natural production forests ..... 8 1.5.6 Community forest management..................................................................... 8 1.5.7 Review of forest and silvicultural research.................................................... 9 1.5.8 Research and management targets in Thailand............................................ 10 1.6 Research objectives and structure........................................................................ 10 1.6.1 Research framework, objectives .................................................................. 10 1.6.2 Structure of the study................................................................................... 11 2 SITE QUALITY AND PRODUCTIVITY ASSESSMENTS ................................. 12 2.1 Introduction ......................................................................................................... 12 2.2 Research outline................................................................................................... 12 2.3 Review................................................................................................................. 13 2.3.1 Soil and geographic features........................................................................ 13 2.3.2 Bioclimatic zone .......................................................................................... 13 2.3.3 Vegetation.................................................................................................... 13 2.3.4 Construction of site index curves based on tree ring investigations ............ 14 2.3.4.1 Selecting trees for stem analyses ............................................................. 14 2.3.4.2 Tropical tree dendrochronology............................................................... 15 2.3.4.3 Datable tropical tree species .................................................................... 16 2.3.4.4 Tree ring research in Thailand ................................................................. 16 2.3.4.5 Autecology of Vitex limoniifolia.............................................................. 16 2.4 Material and methods .......................................................................................... 17 2.4.1 The study area - an overview....................................................................... 17 2.4.1.1 Main site, stand and silvicultural improvement treatment study sites...... 18 2.4.1.2 Additional site productivity study sites.................................................... 19 2.4.1.3 Soil and geomorphological settings ......................................................... 20 2.4.1.4 Climatical settings.................................................................................... 20 2.4.2 Soil analyses ................................................................................................ 22 2.4.2.1 Field data collection................................................................................. 22 2.4.2.2 Laboratory analyses ................................................................................. 22 2.4.2.3 Soil data analysis ..................................................................................... 22 2.4.3 Vegetation analyses ..................................................................................... 23 2.4.3.1 Field data collection................................................................................. 23 VI Index 2.4.3.2 Data analysis...........................................................................................