Rain forest dynamics and response to drought in a Bornean primary lowland dipterocarp forest Inauguraldissertation der Philosophisch-naturwissenschaftlichen Fakultät der Universität Bern vorgelegt von Marcus Lingenfelder von Deutschland Leiter der Arbeit: Prof. Dr. D. M. Newbery Institut für Pflanzenwissenschaften Rain forest dynamics and response to drought in a Bornean primary lowland dipterocarp forest Inauguraldissertation der Philosophisch-naturwissenschaftlichen Fakultät der Universität Bern vorgelegt von Marcus Lingenfelder von Deutschland Leiter der Arbeit: Prof. Dr. D. M. Newbery Institut für Pflanzenwissenschaften Von der Philosophisch-naturwissenschaftlichen Fakultät angenommen. Bern, 22.06.2005 Der Dekan: Prof. Dr. P. Messerli To Anna-Luise and Karl Lingenfelder Table of Contents I. Summary / Zusammenfassung............................................................................... 1 II. Introduction ...................................................................................................... 5 III. Study site.......................................................................................................... 9 IV. Methods.......................................................................................................... 13 1. Field measurements........................................................................................... 13 (a) Measurements made prior to the present study ............................................ 13 (b) Measurements made in the present study .................................................... 16 2. Taxonomic identifications ................................................................................... 22 3. Definition of periods........................................................................................... 23 3.1. Lengths of enumerations .............................................................................. 23 3.2. Overall period lengths .................................................................................. 23 3.3. Naming of periods and populations included .................................................. 24 4. Topography....................................................................................................... 25 5. Population changes............................................................................................ 25 5.1. Mortality and recruitment vs. losses and gains ............................................... 25 5.1.1. Rate calculations .................................................................................... 27 5.1.2. Correction of annualised mortality rates for time interval difference ........... 28 5.2. Growth rates ............................................................................................... 29 5.3. Diversity measures....................................................................................... 30 6. Size classes ....................................................................................................... 30 7. Light environment.............................................................................................. 31 8. Data analysis..................................................................................................... 31 V. Results............................................................................................................ 33 1. Drought intensity derived from ‘antecedent rainfall history’ ................................... 33 2. Topography....................................................................................................... 39 3. The Danum main plots in 2001 ........................................................................... 40 3.1. Structure ..................................................................................................... 40 3.1.1. Tree numbers (including losses and gains)............................................... 40 3.1.2. Density and basal area ........................................................................... 40 3.2. Floristic composition of Danum main plots in 2001 ......................................... 41 3.2.1 Taxonomic revisions in 2001 .................................................................... 41 3.2.2. Quality of taxonomic identifications ......................................................... 42 3.2.3. Floristic composition ............................................................................... 42 3.2.4. Tree diversity......................................................................................... 45 3.2.5. Most abundant species ........................................................................... 46 3.3. Mortality and Recruitment............................................................................. 47 3.4. Growth........................................................................................................ 49 3.4.1. Negative growth rates ............................................................................ 49 3.4.2. Growth across main plots........................................................................ 51 4. Lowland rainforest dynamics 1986 to 2001 .......................................................... 52 4.1. Across main plots......................................................................................... 52 4.1.1. Changes in structure .............................................................................. 52 4.1.1.1. Revisions for 1986 and 1996 ............................................................. 52 4.1.1.2. Tree numbers .................................................................................. 52 i Table of Contents 4.1.1.3. Densities..........................................................................................53 4.1.1.4. Basal area........................................................................................55 4.1.1.5. Density and basal area in topographic classes..................................... 57 4.1.2. Dynamics...............................................................................................58 4.1.2.1. Mortality and recruitment ..................................................................58 4.1.2.2. Mortality in size classes .....................................................................60 4.1.2.3. Mortality in topographic classes ......................................................... 64 4.1.2.4. Growth ............................................................................................67 4.1.2.5. Growth in size classes .......................................................................67 4.1.2.6. Growth in topographic classes ...........................................................68 4.1.3. Changes in floristic composition...............................................................69 4.1.3.1. Taxonomic revisions .........................................................................69 4.1.3.2. Changes...........................................................................................70 4.1.3.3. Diversity ..........................................................................................70 4.2. Dynamics at the species level........................................................................72 4.2.1. Percentage change .................................................................................72 4.2.2. Overall average mortality and interval corrected mortality ......................... 73 4.2.3. Mortality of the most abundant species ....................................................74 4.2.4. Mortality within families ..........................................................................77 4.2.5. Turnover................................................................................................78 4.2.6. Growth across species ............................................................................79 4.2.6.1. Growth of most abundant species ......................................................81 4.2.7. Comparison of growth rates for the most abundant species.......................84 4.2.7.1. ‘Pairs of growth rates’ .......................................................................84 4.2.7.2. ‘Projected growth rates’ ....................................................................90 4.3. Growth and mortality of commercial timber species ........................................95 5. Possible lagged effect of drought in the understorey........................................... 100 5.1. Structure ................................................................................................... 100 5.2. Floristic composition ................................................................................... 100 5.3. Fate of trees .............................................................................................. 101 5.4. Mortality .................................................................................................... 102 5.4.1. Simple mortality rates across all trees .................................................... 102 5.4.2. Overall average mortality with species as groups .................................... 103 5.4.3. Overall average mortality with species within subplots as groups ............. 107 5.4.4. Interval-corrected overall average mortality............................................ 107 5.4.5. Mortality of the most abundant species .................................................. 118 5.4.6. Mortality in size classes........................................................................