Phytogeography, endemism and diversity of the fynbos of the southern Langeberg David Jury McDonald University of Cape Town Thesis Presented for the Degree of DOCTOR OF PHILOSOPHY in the Department of Botany UNIVERSITY OF CAPE TOWN July 1995 The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgement of the source. The thesis is to be used for private study or non- commercial research purposes only. Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University of Cape Town Phytogeography, endemisn1 and diversity of the fynbos of the southern Langeberg David Jury McDonald 'I look to the mountains; where will my help come from? My help comes from the Lord, who made heaven and earth.' Psalm 121: 1-2. '... lofty mountains are most worthy ofdeep study. For everywhere you turn, they present to every sense a multitude of objects to excite and delight the mind They offer problems to our intellect; they amaze our souls. They remind us ofthe infinite variety ofcreation, and offer an unequaled field for the observation ofthe processes ofnature.' Josias Simler {1574) De alpibus commentarius II The southern Langeberg looking westwards from 12 O'Clock Peak (Crown Peak, 1428 m). The highest peak visible is Leeurivierberg (1628.5 m). Preface Why study fynbos? This question has no doubt been asked many times. In a personal sense it may be appropriate to briefly trace how I came to study fynbos and how I have become closely involved with the flora and vegetation of one of the major mountain ranges in the fynbos biome. My interest in fynbos vegetation developed when, as an undergraduate student at the University of Natal University, Pieterrnaritzburg, I read papers and articles on the rich and varied flora of the Cape. Prior to this time I had not ever visited this part of South Africa so was otherwise unfamiliar with fynbos vegetation. This early interest was stimulated further during my Botany Honours course when I investigated the growth and propagation of Protea neriifolia using tissue culture. Later, faced with the decision of following a career in plant propagation or plant ecology, I opted for the latter. My particular goal was then to study aspects of the ecology of Cape fynbos, and more specifically the fynbos of the mountains. In rnid-1980 a position was advertised for a research assistant at the Botanical Research Unit, Stellenbosch (part of the former Botanical Research Institute), to become part of a mountain vegetation survey team. My application was successful and I became part of the team whose object was to survey 'Mountain Fynbos' according to a programme entitled "Botanical survey of the Mountain Fynbos vegetation of South Africa' first drafted in 1965. The programme was to have been 'an Acocks-type survey of all the Mountain Fynbos in south Africa, with special reference to the Capensis area'. As trained staff and resources became more limited and priorities changed in the early to rnid-1970's the early plans were amended a number of times. At this time the structural-functional classification Ill of f;11bos in the mountains by Prof Bruce Campbell was underway and the focus of the parallel floristically-based 'semi-detailed phytosociological surveys' was aimed at two areas designated as the 'Western Mountain Fynbos' and the 'Southern Mountain Fynbos' (details from an memorandum: H.C. Taylor, February 1980). In 1978 the Fynbos Biome Project was constituted as a loose alliance of researchers in the f;11bos (Kruger 1978). One of the special sites earmarked for study was Swartboschkloof at Jonkershoek near Stellenbosch. After my appointment to the staff of the Botanical Research Unit, Stellenbosch at the beginning of 1981 my first project was a survey of the vegetation of Swartboschkloof, under the leadership of Mr Hugh Taylor. Within a few months I took over this project, completed it and wrote a thesis entitled 'The vegetation of Swartboschkloof, Jonkershoek, Cape, South Africa' for a Master of Science degree at the University of Cape Town in 1983. Jonkershoek falls within the 'Western Mountain Fynbos' zone and since Hugh Taylor was aiming at future work on the Cedarberg, in the western zone, I chose to move my focus eastwards to the 'Southern Mountain F)11bos'. The flora and vegetation of the Langeberg were inadequately kilo\\11 and from personal correspondence with the Directorate of Forestry, Department of Environment Affairs, which at that time (1984) was responsible for the management of the mountain catchments of the Langeberg, I ascertained that a survey of the vegetation of this mountain range had a high priority. There was a definite need for a comprehensive study of the flora and vegetation of the Langeberg and this becan1e the primary motivation for selecting this mountain range for study. The first general objective of the study of the vegetation of the Langeberg was to sample and describe the plant communities. An early proposal was to subdivide the Langcberg IV range into sections and sample each of these using a north-south transect that would straddle the mountain. Four transects were initially proposed but this was later reduced to three. The fourth transect was to have been in the section of the Langeberg, referred to as the north-west Langeberg, between Montagu-Ashton and Worcester. However, since this part of the Langeberg is bioclimatically quite different from the southern Langeberg (that part of the range from Montagu-Ashton eastwards to the Gouritz River), a survey of the vegetation of the north-west Langeberg was not carried out. I concentrated my efforts on the southern Langeberg. In studies of the fynbos, as with many other vegetation types, descriptive studies of vegetation based on the floristic composition of the respective communities are of great importance. However, there has been a tendency for these to be seen as an end in themselves. This is a short-sighted view because these studies are rich sources of data that can be used for a variety of other purposes. The data are usually rigorously collected in plots of pre-determined size and the plant species encountered are arduously identified either in the field or in the herbarium. This demands that such data be used for more that just simply describing the assemblages of plants found in a study area; a necessity that is underscored by the high financial and physical cost of acquiring data, particularly in the mountains. Therefore, the second general aim of my study of the vegetation of the southern Langeberg was to extend the use the phytosociological data to investigate the phytogeographic and ecological patterns apparent in the fynbos communities. The idea was to use this data to answer questions that would give insights into the environmental determinants of the distribution of the plant conununities as well as the determinants, both environmental and biological, of endemism and diversity. V In this study a fair measure off success has been achieved in using phytosociological data for the purposes described. However, as rich as they are, these data do not necessarily offer all that is required for more detailed analyses. It has been necessary to obtain additional data from other sources such as herbaria and published taxonomic accounts as well as climate databases and models, to augment the data set. Some limitations of the present data set, for example the location of sample plots, have prevented optimal use of the data in the study of beta diversity for instance. This has highlighted the need for more careful phytosociological sampling procedures that would accommodate more suitable location of plots for other additional analyses. The accumulation and analysis of vegetation data from the southern Langeberg has been a time-consuming, demanding and expensive task but at the same time extremely challenging and enriching. Despite many trials it has been a great privilege to work in this wonderful environment and explore its mysteries. Unfortunately, the cost of extensive surveys such as the one on which this study is based will in future be prohibitive, so this type of work ,,ill probably not be done on a large scale. This is all the more reason why it has been imperative to capitalize on the available data and use them as meaningfully as possible. Not only have theoretical questions required answers, but more importantly an attempt has been made to address practical questions aimed at conserving the fynbos as a national and global resource. It is my hope that the work presented in this thesis - which is the culmination of a number of years of intimate contact with the southern Langeberg and its flora - will contribute in some way to the understanding and wise use of the fynbos in general and more specifically to the conservation of the fynbos of the southern Lange berg. VI Acknowledgements During the course of this project many people assisted in numerous ways, both large and small. Each of these people has made a contribution, not only to the final product but also to me personally. To all of them, although they may not be named, I am deeply indebted. My family has made a great sacrifice in accepting long weeks of absence of a husband and father while I was away from home on field trips. These \Vere difficult times and I am grateful for their patience. In the later 'writing-up' stages of the project and production of this thesis my family has been equally supportive and understanding. To Anne, Ross, Bryony and Claire I owe my sincere appreciation for their love, care and long-suffering.