The 2002 Banks Memorial Lecture The flora of Mt Taranaki/Egmont: Understanding natural and garden experiments Bruce D. Clarkson1 Introduction stones or tufts of grass, but bore much In this, the 2002 Banks Memorial resemblance to flocks of sheep”. It is Lecture, I have two main aims. First, most likely those were hummocks or I will trace what has been discovered patches of the Racomitrium mosses by botanists about the Mt that are still a feature of the debris Taranaki/Egmont flora since Joseph flows on the upper western slopes of Banks scanned the mountain from the mountain. But unfortunately Banks the deck of Cook’s Endeavour in 1770. never had the opportunity to botanise Second, I will discuss some of the on the ground. Figure 1. Mt Taranaki/Egmont, the most recent volcano of the Taranaki Volcanic Succession. results of my own garden and natural experiments, conducted in more Botanical history “missing” taxa (460) and clearly recent times. The first European to describe plants established the significance of recent The landscape that has been the on the mountain was Ernst eruptions in determining vegetation setting for this work is the sequence Dieffenbach, naturalist to the New composition. of linear (NNW to SSE) volcanic activity Zealand Company. His contribution known as The Taranaki Volcanic is still commemorated in the name of My research: natural and garden Succession. Volcanic activity began Kelleria [Drapetes] dieffenbachii, the experiments at Paritutu and the Sugar Loaf Islands dwarf native daphne found in the My interests in the native flora began near New Plymouth 1.75 million years alpine zone. James Buchanan, a as a child growing up “under the ago and was followed by the genesis surveyor and botanist, followed in mountain”. Between 1961 and 1973, of Kaitake, Pouakai and Mt 1869 and recorded 180 vascular I established and maintained a small Taranaki/Egmont, 575,000, 250,000 species on a journey from New native plant garden in the front lawn and 70,000 years ago, respectively. Plymouth over the Pouakai Range to of our homestead. My mother’s exotic My research has focused on the plants the northern slopes of Mt Taranaki. bedding plants and shrubs were growing on these three, progressively Leonard Cockayne, the internationally removed and replaced by a native younger volcanoes. Each has its own renowned plant ecologist, made plant collection, including many distinctive features: each is in effect several trips to Mt Taranaki and listed species collected from the higher a small but distinct botanical district. some 220 vascular species. Oliver slopes of the mountain. These first Nearly all of the landscape covered (1931) was the first to publish garden experiments helped me to with indigenous vegetation is within evidence of the recent eruptions, identify plants and observe their Egmont National Park (Figure 1). describing the presence of scoria phenology and behaviour at close It is fitting that my topic for the lodged in large trees near Stratford, hand. This was the foundation for Banks Memorial Lecture has a direct and Maori ovens (umu) beneath recent much of my later research. link to Joseph Banks. As a botanist I ash layers. However, the most Between 1975 and 1977, for my can easily imagine how frustrating it significant contribution to Master of Science thesis I focused would have been for Banks to see the understanding the flora of the Egmont more on natural experiments following mountain from the deck of the National Park was made by the late the approach advocated by Pielou Endeavour and yet not be able to go Anthony (Tony) Druce in a series of (1977): “Because natural zonation ashore and investigate its botanical publications between 1953 and 1976. (which can be thought of as a natural treasures. Banks did observe “many Tony more than doubled the number experiment) is so ecologically white lumps in companies of fifty or of vascular species known within the informative, it is worthwhile to seek it sixty together, which probably were park (to 440), quantified the extent of out even in places where it would not 1Centre for Biodiversity and Ecology Research, Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton 2 New Zealand Garden Journal, 2002, Vol.5 (2) automatically be expected”. Such From 1981 to 1992, while working perhaps could be distinct only at a places include the margins of for the Department of Scientific and subspecies level. However, more DNA wetlands, sites of major disturbance Industrial Research in Rotorua, the sequencing research will be required or change in topography. I documented main emphasis of my research turned to test this hypothesis. Similarly, the and explained changes in vegetation back to common garden experiments. status of the rhizomatous bog structure and composition with This included growing a wide range Celmisia on the Pouakai Range increasing altitude, and changes in of North Island natives to test requires resolution. The largest species interactions relating to slope. hypotheses about species status Celmisia recorded in the park, C. I continued with the natural particularly in Hebe, Coprosma, semicordata (= C. coriacea), is experiment approach for my Doctor Melicytus and Olearia. doubtfully native. It occurs on the of Philosophy research between 1978 main cone at one isolated site and and 1981. This time I focused on Current status of the flora was probably planted there. variation in vegetation structure and Turning to the current statistics on the Hebe also remains problematic composition around the cones, and flora of the Egmont National Park, we although its resolution seems more understanding eruption effects on now know that at least 550 indigenous imminent than in Celmisia. The vegetation, especially at the treeline. vascular species occur here. The common subalpine scrub species is Results showed how the treeline magnitude of the vascular flora of the named Hebe stricta var. egmontiana composition related to the direction park is now very well known. I am in the Flora Volume 1, but it is clearly and depth of recent ash showers, aware of only four new listings to the a different species to H. stricta, having especially the Burrell eruption of 1655 park flora since the 1980s. A recent double the chromosome number (2n AD. A small suite of tree species, exciting discovery was the threatened = 80). At present it should be referred kamahi (Weinmannia racemosa), native milfoil (Myriophyllum robustum). to as Hebe sp. unnamed (H. kaikawaka (Libocedrus bidwillii), Progress has been made in “egmontiana”). Hebe subsimilis var. broadleaf (Griselinia littoralis) and Hall’s understanding the status of many of astonii which occurs only on Pouakai totara (Podocarpus hallii), are found the species in the park, but several could possibly be a variety of the more in various different combinations at problems remain. I will discuss some widespread Hebe tetragona complex, different treeline sites depending on examples that I have worked on, but in cultivation it retains its more past eruption effects. The distinctive recognising that this is not a delicate growth form and is not as goblin forest (kamahi-Hall’s totara comprehensive discussion. drought tolerant as true H. tetragona. forest) of the main Egmont cone at Celmisia provides a continuing Hebe odora has two distinct forms Dawson Falls, Stratford Mountain problem, especially the taxa belonging in the park. The common form occurs House and near the North Egmont to the C. gracilenta/graminifolia mainly in tussock grassland and Visitor Centre also owes much of its complex. Celmisia major var. brevis subalpine shrublands on both the character to the impacts of recent may or may not be part of a Egmont and Pouakai cones, but on eruptions (Figure 2). widespread species complex, and the Pouakai tops there is a prostrate form that retains this character in cultivation. Other variants occur elsewhere, on North Island mountains at least, and resolution will require more detailed comparison before a decision about its status can be made. One taxon previously considered an Egmont endemic, Ourisia macrophylla subsp. macrophylla, has lost this status, having been found on the Herangi Range some 120km to the north. The everlasting daisy (Anaphalioides alpina) of the alpine zone of Egmont and many other mountains has at last been recognised as distinct from the more widespread A. bellidioides. Figure 2. Kamahi (Weinmannia racemosa) dominated goblin forest at North Egmont. Of the five or six species still New Zealand Garden Journal, 2002, Vol.5 (2) 3 ground are probably major reasons proportions in the 1960s, and for the depauperate flora, as well as thankfully deer and pigs have never the exceptional abundance of kamahi been a significant problem. Most of and leatherwood (Brachyglottis the weeds that have invaded the park elaeagnifolia) over large areas of the to date are rather benign by national park. and international standards. However, Five taxa common in the South ongoing surveillance will be required Island have their only North Island to ensure the forests especially are occurrence in the park. These vary protected from invasive shade tolerant considerably in abundance, the shrubs, trees and lianes cultivated in extremes illustrated by the alpine lowland gardens, which have not yet shield fern (Polystichum cystostegia) naturalised. and mountain lacebark (Hoheria The indigenous vegetation glabrata). Alpine shield fern can be protected within the park is not found in the alpine zone on Egmont, representative of the full range of Figure 3. Melicytus drucei shrubs on the but the mountain lacebark has so far diversity once characteristic of the margins of Ahukawakawa Swamp (Dr Brian completely eluded me. This tree was Egmont Ecological District. There are Molloy as scale). found in the 1960s by Tony Druce and still some prospects for developing considered to be Egmont endemics, Geoff Kelly while measuring the forest lowland corridors of forest especially only one has been fully resolved.