PHOTOSYNTHETIC CHARACTERISTICS OF TREES AND LIANAS ALONG AN ALTITUDINAL GRADIENT IN ECUADOR Jana Pauwels Student number: 01403120 Promotors: Prof. dr. Hans Verbeeck and dr. Marijn Bauters Tutors: ir. Miro Demol and Lore Verryckt Master’s Dissertation submitted to GHent University in partial fulfilment of the requirements for the degree of Master of Science in Bioscience Engineering: Environmental TecHnology Academic year: 2018 - 2019 De auteurs en promotors geven de toelating deze scriptie voor consultatie beschikbaar te stellen en delen ervan te kopiëren voor persoonlijk gebruik. Elk ander gebruik valt onder de beperkingen van het auteursrecht, in het bijzonder met betrekking tot de verplichting uitdrukkelijk de bron te vermelden bij het aanhalen van resultaten uit deze scriptie. The authors and supervisors give the permission to use this thesis for consultation and to copy parts of it for personal use. Every other use is subject to the copyright laws, more specifically the source must be extensively specified when using from this thesis. Gent, juni 2019 De promotor, De auteurs, Prof. dr. Hans Verbeeck Jana Pauwels iv Acknowledgements After two months of research in Ecuador and 8 months of analysis and writing, I can proudly say my thesis is finally finished. I can guarantee you it was not plain sailing. Without the help of a bunch of great people, it was never possible to write this thesis. In Ecuador, I was dealing with various technical problems. At the end, these difficulties improved my problem-solving thinking. Besides, I arrived in a team with Spanish speaking people. Luckily, they welcomed me with open arms and showed me a good time. Now, I can count them as my friends. They taught me the basics of Spanish by repeating words infinite times (cuchillo, cuchara, tenedor, cuchillo, cuchara, tenedor, ...). We stayed at places miles from everywhere without any connection with the outside world, where the mulas had to carry our stuff to. We pulled pranks, had discussions about salty or sweet popcorn or taught each other games. We did tree climbing and slid from mama piedra. In short, it was an instructive, but most of all an experience worth remembering. First of all, I want to express my gratitude to my promotor Prof. dr. ir. Hans Verbeeck for offering me this opportunity. I’m deeply indebted to my co-promotor dr. ir. Marijn Bauters and my supervisors ir. Miro De Mol and dr. Lore Verryckt (also known as the photosynthesis-guru). I am looking up to each one of you, guys! During these 10 months, you helped me with solving problems in the field, with the analysis of my data and with proofreading my text. Your critical eye helped me enormously. A special thanks to Michael and James from PP Systems to answer all my many questions about the CIRAS-3. You succored me with the solving of various technical problems with the available resources. Also, I would like to thank Thomas Sibret for demonstrating me the functioning of the CIRAS-3. I cannot leave Selene Baez and Debbie Eraly without mentioning, who assisted me with the practical arrangements. Thank youight Alberto for translating my abstract to Spanish. I’d like to acknowledge Mindo Cloudforest Foundation for letting us stay in one of the cabañas. It was stunning to eat with a view on many squirrels, guatusas, toucans, hummingbirds and other colourful birds. Germania and Karina cooked for us the most mouthwatering meals and made delicious jugos. We were really spoiled by you! I also want to thank German for being hospitable. Your lodge is without a doubt very pleasant to stay. On top of that, you helped me also to determinate my species. Gracias Jens, for jumping in this big adventure with me. Even if our paths during the thesis research in Ecuador were most of the time separated, you were a big support to me. It was always a pleasure to talk some Dutch again, it felt a bit like coming home. The three weeks of travelling together through the beautiful Ecuador was the best ending of this experience I could wish for. I can proudly call you one of my best friends. I had a great pleasure working with the entire team "casa estudio". Nico, my favourite metal friend, I admire your passions in life. I am truly amazed that you taught yourself recognizing botanical plants. I am so grateful that you searched and determined my species every single day. Paúl assisted with gathering my leaves, even if that meant hanging on the tree to be able to cut them with the pruner. Muy amable, amigo. I often think back to our stupid conversations and making jokes about each other. Also, Paula was unmissable these two months. When my Spanish vocabulary was still limited to a few words, you stood up for me. I really miss your weird Spanish accent when you were talking English. Unfortunately, Paola and Tito were vi only with us half of the time. You were both such kind people who I will never forget. Many thanks Paola for letting me use your cell phone when we were in the middle of nowhere and I had to contact someone if my máquina was stubborn again. Last but not least, I wouldn’t be writing this without the endless support of my family. Thank you mama, for making me who I am now and giving me all the chances in my life. Also, I want to give my appreciation to my friends and my boyfriend Jelle for working together and to take a break from time to time. Thank you all for being such amazing and supporting persons. Contents Acknowledgements v List of Abbreviations xi Abstract xiii Samenvatting xiv Resumen xv 1 Introduction 1 2 Literature review 3 2.1 From forest to tropical montane cloud forest . .3 2.1.1 Forest ecosystems . .3 2.1.2 Tropical rainforest . .3 2.1.2.1 The role of lianas in tropical rainforests . .5 2.1.3 Tropical montane cloud forest . .5 2.1.3.1 Hydrology of TMCF . .6 2.1.3.2 Threats of TMCF . .6 2.1.3.3 TMCF in Ecuador . .8 2.2 Water Use Efficiency . .9 2.2.1 Definitions . .9 2.2.2 WUE and climate change . .9 2.2.3 13C isotope signature and discrimination as evaluation . .9 2.2.4 WUE differs between trees and lianas . 10 2.2.5 Case study: the isotope trends in Ecuador and Rwanda . 11 2.3 Leaf photosynthesis . 11 2.3.1 Photosynthetic light-response curves . 13 2.3.1.1 Theory . 13 CONTENTS viii 2.3.1.2 Fitting . 13 2.3.1.3 C3 and C4 pathway . 15 2.3.1.4 Sun and shade leaves . 15 2.3.2 gs-VPD curves . 17 2.3.2.1 Theory . 17 2.3.2.2 Fitting . 17 2.4 Altitudinal gradients . 19 2.4.1 Changing parameters with the altitude . 19 2.4.2 High altitudinal ecosystems are more vulnerable to climate change . 19 3 Material and methods 21 3.1 Site description . 21 3.2 Leaf inventory . 24 3.3 Leaf sample analysis . 25 3.3.1 Response curves . 25 3.3.1.1 Leaf net photosynthesis . 25 3.3.1.2 Light response curves . 26 3.3.1.3 gs-VPD response curves . 26 3.3.2 Specific leaf area . 26 3.4 Data processing and statistical analysis . 28 3.4.1 Data quality check . 28 3.4.2 Regression selection . 28 3.4.3 Statistical analysis . 29 4 Results 31 4.1 Regression selection . 31 4.2 gs-VPD measurements . 31 4.2.1 Comparison between growth forms and altitudes . 32 4.2.2 The effect of the different genera . 34 4.2.3 Comparison between growth forms and forest type . 35 4.3 SLA............................................... 36 4.4 Carbon assimilation . 39 4.5 Intrinsic and instantaneous WUE . 42 CONTENTS ix 5 Discussion 47 5.1 Water relations . 47 5.1.1 Goodness of fit . 47 5.1.2 The response of the stomata on atmospheric drought stress . 47 5.1.3 Altitudinal changes . 48 5.1.4 Differences between growth forms . 49 5.1.5 Genetic effects . 52 5.2 Carbon relations . 52 5.2.1 SLA . 52 5.2.2 Maximum carbon assimilation . 53 5.3 Carbon-water relations . 54 5.4 Impacts of climate change on TMCFs . 55 5.5 Pitfalls of the measurement method . 56 6 Conclusions 57 7 Bibliography 59 A Extra Tables and Figures 68 CONTENTS x List of Abbreviations Φ0 Apparent quantum efficiency A Net photosynthetic rate Amass Mass-based saturated net photosynthetic rate Asat Area-based saturated net photosynthetic rate a.s.l. Above sea level C Carbon ca Atmospheric leaf CO2 concentration CAVElab Computational & Applied Vegetation Ecology ci Internal leaf CO2 concentration CIRAS Combined Infra-Red Analysis System CO2 Carbon dioxide E Leaf level transpiration ET Evapotranspiration FAO Food and Agriculture Organization FWU Foliar water uptake GHG Greenhouse gases GPP Gross primary production gmax Maximum stomatal conductance gs Stomatal conductance H2O Water Icomp Light compensation point IRGA Infra-red gas analyser iWUE Intrinsic water use efficiency LA Leaf area LM Leaf mass LMA Leaf mass per area LMER Linear mixed-effects regression MAE Mean absolute error xii MAPE Mean absolute percentage error MCF Mindo Cloudforest Foundation MSE Mean squared error Narea Area-based nitrogen content Nmass Mass-based nitrogen content PAR Photosynthetically active radiation PPFD Photosynthetic photon flux density PSP Permanent sampling plot RAINFOR Red Amazonica de Inventarios Forestales Rd Dark respiration rate RH Relative humidity RMSE Root mean squared error SLA Specific leaf area Tamb Ambient temperature Tcuv Cuvette temperature Tleaf Leaf temperature TMCF Tropical montane cloud forest VPD Vapour pressure deficit WUE Instantaneous water use efficiency Abstract Research questions: Is there a different response to atmospheric drought between lianas and trees as well as between the different types of forests? Similarly, do the saturated carbon assimilation (Asat), specific leaf area (SLA), intrinsic and instantaneous water use efficiency differ (iWUE and WUE respectively)? Is the carbon assimilation linked with SLA? Are the genetic effects playing an important role in the differences of aforementioned variables between plants? Location: Four strata at a 400-3000m a.s.l.