Tree Species Diversity of Agro- and Urban Ecosystems Within the Welgegund Atmospheric Measurement Station Fetch Region
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Tree species diversity of agro- and urban ecosystems within the Welgegund Atmospheric Measurement Station fetch region L Knoetze 21215294 Dissertation submitted in fulfillment of the requirements for the degree Magister Scientiae in Environmental Sciences at the Potchefstroom Campus of the North-West University Supervisor: Prof SJ Siebert Co-supervisor: Dr DP Cilliers October 2017 DECLARATION I declare that the work presented in this Masters dissertation is my own work, that it has not been submitted for any degree or examination at any other university, and that all the sources I have used or quoted have been acknowledged by complete reference. Signature of the Student:………………………………………………………… Signature of the Supervisor:………………………………………………………. Signature of the Co-supervisor:………………………………………………………… i ABSTRACT Rapid worldwide urbanisation has noteworthy ecological outcomes that shape the patterns of global biodiversity. Habitat loss, fragmentation, biological invasions, climate- and land-use change, alter ecosystem functioning and contribute to the loss of biodiversity. This warrants the study of urban ecosystems and their surrounding environments since biodiversity is essential for economic success, ecosystem function and stability as well as human survival, due to the fact that it provides numerous ecosystem goods and services. Furthermore, agroecosystems are continuously expanding to meet human needs and play a distinctive role in supplying and demanding ecosystem services, consequently impacting biodiversity. With anthropogenic impacts on ecosystems increasing exponentially, pressure on ecosystem services are intensifying and ultimately unique urban environments that are perfect for the establishment of alien species is created. The proportion of native species in urban areas has increasingly been reduced due to urbanisation, while the proportion of alien species has markedly increased. Trees are normally not considered as typical weedy plants, but many species are invasive aliens in different parts of the world. Trees are generally long-lived and easy to locate, which make trees good indicators of long-term climate conditions, physiognomy and overall vegetation structure. Knowledge of urban floras is vital to improve and maintain the services provided by these areas, as well as aiding in conservation and management practices in urban and surrounding ecosystems. The aim of this study was to compile a detailed floristic account of the woody vegetation of agro- and urban ecosystems in a 60 km radius around the Welgegund Atmospheric Measurement Station. Bushclumps in different land-cover types were targeted, namely gardens, grasslands, hillsides, plantations, ridges, riparian areas, roadsides, sandy areas, streets and urban open spaces and included tree measurement along a belt transect. Results indicated clear differences between land-cover types as well as alien and indigenous species diversity and composition, which were indicated by means of ordinations. A total of 169 woody species were recorded, with aliens comprising 114 of these species. Tree species diversity was higher in urban areas, but mainly constituted of alien species, whereas species richness was higher in natural areas. Meaningful correlations occur between the socio-economic status of cultivated areas and the categories of alien invader trees. DCA, NMDS, Linnear Mixed Models displaying effect sizes, diversity indices and basic statistical analyses were performed using the data. Variation in tree species composition and diversity occur between the different land-cover types. Keywords: Agroecosystems, Tree diversity, Urban ecosystems, JB Marks Local Municipality, Woody species. ii ACKNOWLEDGEMENTS I would like to thank and acknowledge the following people, institutions and organisations that have aided me in the completion of this study. First and foremost, I want to thank my Heavenly Father, for being with me every step of this journey and for always working everything out for the best… Quoting this prayer from the movie “Book of Eli” seems the most appropriate way to give thanks. “Dear Lord, thank you for giving me the strength and conviction to complete the task (my M.Sc.) you entrusted to me. Thank you for guiding me straight and true through the many obstacles in my path. And for keeping me resolute when all around seemed lost. Thank you for your protection and for your many signs along the way. Thank you for the good that I may have done. I am so sorry about the bad. Thank you for the friends I made during my studies. Please watch over them as you watched over me. I fought the good fight. I finished the race. I kept the faith.” My sincerest gratitude to my supervisor, Stefan Siebert, who supported and believed in me, throughout this journey. Without your encouragement, supervision, guidance and support, I would not have been able to finish my masters. Thank you for always being available at short notice and for your time and effort with my studies. I would also like to thank my co-supervisor, Dirk Cilliers, for your support, encouragement, excellent GIS map drawing skills and always helping with any questions. A special thanks to Dr. Suria Ellis of the Statistical Consultation Services, North-West University and Dr. Frances Siebert for helping with statistical analysis and making the numbers significant. Esmé Harris (from Esmé Harris Text editing and proofreading) and Peter Jansen (Stellenbosch University) for editing and proofreading my work. The National Research Foundation (NRF); North-West University, Potchefstroom Campus; Atmospheric Chemistry Research Group and Prof. Nico Smit for financial support. Alisja Janse van Rensburg, Anita Knoetze, Arnold Frisby, Dennis Komape, Hanna Wessels, Helga van Coller, Hlobisile Khanyi, Jaqueline Knoetze, Laaiqah Abdul Jabar, Peter Jansen and Tammy Knoetze for assisting with the endless fieldwork… Brigitte Languag with final formatting and for putting it all together. I am so greatful!! Finally, I would like to thank my friends and family, for your encouragements, endless love, support, prayers and understanding during this period. Thank you Helgi, Nannies, Hanna and Laaiqah for always being there, making me laugh and laughing with me and keeping me iii positive, as well as listening and enduring my endless “tree talk”. Tamz, thanks for your love and support, especially during the last stretch. Jaqueline, thank you for your help with data processing and constant encouragement. Laaiqah, thanks for the part you “acted out’” near the end and all the significant jokes and Special K talk – you were an awesome office mate and colleague. Hanna, for being there every step, putting up with me under one roof, enduring the leaves and masters project things everywhere, as well as for supporting me in ways no one else could. My deepest gratitude goes to my parents, Tienie and Anita Knoetze, for their everlasting love and support, endless prayers, encouragement, financial support, understanding and carrying me through the last stretch. Without you, I would not have been able to finish. Mom, I am indebted to you, for your help, support and the effort you put into my last stretch. It is also to my parents that I would like to dedicate this work... Thank you Leandra Knoetze SOLI DEO GLORIA iv TABLE OF CONTENTS DECLARATION ......................................................................................................................... I ACKNOWLEDGEMENTS ........................................................................................................ III LIST OF TABLES ................................................................................................................... XII LIST OF FIGURES .................................................................................................................. XV LIST OF DEFINITIONS .......................................................................................................... XIX CHAPTER 1 .............................................................................................................................. 1 INTRODUCTION ....................................................................................................................... 1 1.1 Background ...................................................................................................... 1 1.2 Project history .................................................................................................. 3 1.3 Study rationale .................................................................................................. 3 1.4 Aims and objectives ......................................................................................... 5 1.4.1 Wider aim ........................................................................................................... 5 1.4.2 Immediate aim and objectives ............................................................................ 5 1.5 Hypotheses ....................................................................................................... 5 1.6 Format of dissertation ...................................................................................... 6 CHAPTER 2 .............................................................................................................................. 8 LITERATURE REVIEW ............................................................................................................. 8 2.1 Introduction .....................................................................................................