Structural and nutritional differences between climbers and their supporting trees in a montane rainforest in South-Ecuador Dissertation Thesis Department of Systematic Botany and Ecology, University of Ulm Dissertation zur Erlangung des Doktorgrades Dr. rer. nat an der Fakultät für Naturwissenschaften der Universität Ulm 2004 Dipl.-Biol. Jörg Salzer Amtierender Dekan: Prof. Dr. R. J. Behm 1. Gutachter: Prof. Dr. Marian Kazda 2. Gutachter: Prof. Dr. Elisabeth Kalko Vorgelegt am 01.10.2003 Tag der Promotion: 05.02.2004 CONTENTS Acknowledgments IV Summary V Zusammenfassung VII Resumen IX 1. Introduction 1 2. Material and Methods 10 2.1. Geographical location of the research area 10 2.2. Climatic conditions 11 2.3. Geology, geomorphology and soils 12 2.4. Vegetation 13 2.5. The investigation plots 15 2.5.1. Soil properties and vegetation types 16 2.6. Sampling procedure and processing of the plant material 20 2.6.1. Measuring leaf area index (LAI) and canopy gap fraction (DIFN) 21 2.6.2. Measuring relative photon flux density (PFDrel) 22 2.6.3. Calculation of leaf area (LA) and leaf mass per unit area (LMA) 23 2.6.4. Kjeldahl digestion 24 2.6.5. Photometry of phosphorus 24 2.6.6. Atomic absorption spectrometry 25 2.6.7. Measurements of carbon content 25 2.7. Statistical interpretation 26 2.7.1. Description of the investigation plots 26 2.7.2. Control for associations between the two growth forms 26 2.7.3. Testing the differences between the two growth forms 26 2.7.4. Testing the differences between the investigation plots 27 2.7.5. Testing the influence of external factors on the plants 28 2.7.6. Grouping of all variables in a principal components analysis 28 3. Results 29 3.1. Environmental conditions on the investigated plots 29 3.2. Sampled specimens and the host/climber-relationship 34 3.2.1. Plant lists 34 3.2.2. Plant distribution among the plots 36 3.2.3. Associations between the two growth forms 37 3.3. The differences in structural and nutritional parameters 40 3.3.1. Differences between the growth forms 40 3.3.2. Differences between the investigated plots 43 3.3.3. Leaf parameter values of the investigated genera 49 3.4. Leaf parameters of the investigated genera 63 3.5. Synthesis of leaf parameters 69 3.5.1. Factor loadings of the PCA 69 3.5.2. Factor loadings according to the genera 71 3.6. Comparison of young and mature leaves 76 3.6.1. Collected leaf samples 76 3.6.2. Differences in LMA, Nmass and Narea 77 4. Discussion 80 4.1. Plot selection 80 4.2. Associations between climbers and host plants 81 4.3. Differences in leaf structure and nutrient allocation 83 4.3.1. Reduction in leaf mass per unit area in the climbers 83 4.3.2. Leaf structure on different plots under changing light regimes 85 4.3.3. Nitrogen allocation and its role in photosynthesis 87 4.3.4. The other nutrients 93 4.3.5. The role of Aluminium 95 4.3.6. Classification derived by PCA 97 4.4. Comparison of young and mature leaves 98 4.5. Conclusions 102 5. Literature 104 Appendices A1 Appendix 1: Environmental conditions at the sample pairs A1 Appendix 2: Soil-pH and content of exchangeable element on the plots A3 Appendix 3: Complete dataset of all collected climber species A4 Appendix 4: Complete dataset of all collected supporter species A6 Appendix 5: Mature and young leaves dataset A8 Appendix 6: Mean leaf structure parameters A9 Appendix 7: Mean leaf element contents A9 Appendix 8: Mean leaf structure parameters among all plots A10 Appendix 9: Mean leaf element contents among all plots A11 Acknowledgements IV ACKNOWLEDGEMENTS I want to express my acknowledgements to all who helped me with my work during the past four years. Firstly, I want to thank Prof. Dr. Marian Kazda for giving me the opportunity to conduct my studies in several tropical countries, for guidance in every critical phase, and for the free and trusty atmosphere he provided me in the Department of Systematic Botany and Ecology. Not to forget his financial support during the whole time. Secondly, I want to express my thanks to the co-referent Prof. Dr. Elisabeth Kalko, as she showed so much interest in my work. Without Prof. Dr. Sigrid Liede from the University of Bayreuth this work would not have been possible. She asked me to help one of her PhD students in Ecuador and gave me also the possibility to perform my own scientific program there. The study was included in and partly financed by the DFG projects LI 496/11-1 and LI 496/11-2. Research permit was given by the Instituto Ecuadoriano Forestal de Areas Naturales y Vida Silvestre (INEFAN), and logistic help came from the Fundación Cinetífica San Francisco (FCSF). Scientific counterpart in Ecuador was Ing. Zhoffre Aguirre. I also want to thank Patricia Brtnik for translating the summary into spanish, Graciela Hinze for her final reviews on the “resumen”, Dr. Iris Schmid, Philipp von Wrangell, Norbert Gäng, Kordula Heinen and Gregoire Hummel for their ideas during the past years, Christel Necker for her outstanding help in the laboratory, Steffen Matezki for determination of most samples, and a long list of other people for their friendship and support – hopefully they all know that they are mentioned. Special thanks go out to Rita Schneider. She gave me not only substantial comments on the manuscript, but also amounts of motivation and a place of peacefulness for my mind in hard phases during the past months. Finally, I want to mention my parents. They enabled me always to follow my way and gave me all the support I needed so much. I just hope that my mother can see how everything now has come to a great end. Summary V SUMMARY Climbing plants, like lianas, vines or root climbers, can be the dominating growth form on several sites not only in tropical forests but also in other climatic zones. Climbers from a wide range of plant families can be found especially on forest edges and treefall gaps. The uneven distribution of this growth form was well investigated in the past years and different reasons for that patchiness, like light demand, support quality and nutrient or water availability were mentioned but not fully understood. Further research upon the relationships between external parameters and climber abundance is necessary as different types of mostly negative effects on the host trees were reported in many studies. Knowledge about the climbers ecophysiology is mainly limited on transpiration and water transport, but other physiological mechanisms that also determine the competitiveness of a climbing plant and thereby its abundance are still poorly understood. The climbers fast growth requires fast adaptability to changes in their surrounding conditions, such as effective biochemical mechanisms within the plant, combined with low growth-cost and high nutrient content. Former studies already indicated a good assignment of nitrogen towards light harvesting under shade by low leaf mass per unit area (LMA) in the leaves of climbers, accompanied by high leaf nitrogen contents. Aim of this study was to improve the knowledge about the mechanisms that lead to different patterns in climber abundance. Therefore basic data in high resolution were inquired about the nutritional status of climber leaves compared with their supporting hosts along different environmental conditions. The study was performed in a primary montane rainforest in South-Ecuador along an altitudinal gradient between 1930 m a.s.l. and 2700 m a.s.l., covering a wide range of different forest types. On each of the 8 investigation plots 10 pairs of climbers and supporting host plants were selected. Stand characteristics were investigated by measuring LAI, DIFN and PFDrel below each sample pair and directly above them. The single plots distinguished well in their crown closure and light availability, giving so the possibility to achieve high resolution data about the different reactions of climbers and their supporting trees towards changing conditions. Retarded nutrient turn-over in the soils of the undisturbed plots on the investigation area, a varied mosaic of parent materials, and therefore extremely patchy nutrient availability conditions can explain the uneven abundance of climbers in the ECSF forest with its huge species and structural diversity. Host tree preferences by climbers were tested but were not evident and did so not Summary VI influence the further evaluation. Leaf samples from both growth forms were collected pair wise and analysed for structural factors (LA, LMA, C, Carea) and element contents (Nmass, Narea, P, K, Ca, MG, Mn, Al). Results showed that investment in supporting tissues on leaf level was lower by the climbers than that by their hosts. Climbers built smaller leaves with lower specific leaf mass (LMA). The morphological structures were better adapted to the prevailing light conditions than within the self supporting vegetation. Very economic allocation of nutrients was expressed on leaf area basis (Narea) by irradiance input optimised nitrogen contents. Variations in LMA and Narea values along the light gradient were remarkably lower within the climbers. With less investment per leaf area the climbers can achieve comparable carbon gain as their hosts, which was confirmed by photosynthesis measurements in another ecosystem. The efficient use of nutrient resources was also evident for phosphorus and potassium, which enables the climbers not only to allocate nutrients towards their shoot growth but also fast responses toward changes in their environment. Several variables like e.g. PFDrel, LMA and Narea were combined to new factors in a principal components analysis.