DESCRIPTIONS OF SOME MATURE KAURI FORESTS OF NEW ZEALAND by Moinuddin Ahmed and John Ogden Department of Botany, University of Auckland, Private Bag 92019, Auckland ABSTRACT A quantitative sampling of 25 mature kauri stands, throughout the species natural limits, was carried out. Each kauri stand is described in terms of its phytosociological attributes (frequency, density and basal area) for kauri and associated canopy and subcanopy species. A species list of plants under 10cm dbh is also given with their relative frequencies in each stand. In all stands kauri comprises most of the basal area. It is associated with 10 different co-dominant species. However, most of the forests have a similar species composition. It is suggested that all these kauri forest samples belong to one overall association. INTRODUCTION The vegetation of various kauri forests has been described by Adam (1889), Cockayne (1908, 1928), Cranwell and Moore (1936), Sexton (1941), Anon (1949) and more recently Barton (1972), Anon (1980) and Ecroyd (1982). A quantitative description of some kauri forests was given by Palmer (1982), Ogden (1983) and Wardle (1984). However, due to extensive past disturbance and milling, most of the above accounts do not describe the natural forest state. Observations on the population dynamics of mature kauri forests were presented by Ahmed and Ogden (1987) and Ogden et al. (1987) while multivariate analyses were performed by Ahmed (1988). However, no comprehensive attempt has yet been made to analyse mature undisturbed kauri forest stands in relation to their species composition. Kauri forests have a restricted distribution in the North Island. Among these remnants, there are few, if any, truly untouched sites. Change to, or removal of, surrounding vegetation has changed not only the surrounding microclimatic conditions but also the denser central parts of most of the virgin stands of kauri. Bearing these points in mind, the paper presents details of 25 study areas mostly sited in undisturbed kauri forests. MATERIALS AND METHODS Mirams (1957) regarded mature kauri as being at least 60cm diameter breast height (dbh). However, our criteria of mature kauri forest were: 89 Tane, Vol. 33,1991 1) that it should contain trees greater than 60cm dbh; 2) that there should be no sign of obvious disturbance (in some cases where signs of disturbance were found after sampling had commenced, this criterion was relaxed); and 3) that it covered at least 2ha in area. Quantitative samplings were carried out from 1980 to 1983. Point Centred Quarter Method (Cottom and Curtis, 1956) with the modification of Ogden and Powell (1979) was used to sample 25 kauri stands. In each stand 20 points were taken at 25m intervals along four 100m transects. However, in some cases due to landslides (slips) or the small area of the stand this procedure was not possible and shorter transects were taken. Trees > 10cm dbh only were included in the PCQ sampling. A species list with a frequency table for understorey plants (< 10cm dbh) was made using a circular plot (5m diameter) at each point. Lower plants were ignored but some widely distributed Pteridophyta were included. Species in the canopy, subcanopy and canopy gaps were noted separately. Slope, aspect and phytosociological attributes (density, frequency and basal area) were recorded. Ogden and Powell (1979) and Palmer (1982) used the term 'PCQ frequency' (PCQ = Point Centred Quarter Method) because according to Curtis and Mcintosh (1951) frequency values from plotless methods are not strictly comparable with those obtained using plot methods. Importance values (IV = the sum of relative values of frequency, density and basal area) give more information about the species than any other single attribute alone and reflect the realistic ecological importance of the species in a stand (Brown and Curtis, 1951). Every species was ranked according to its importance value and the species with the highest importance value in the stand was considered the dominant species. The data for each stand was summarised following Mueller- Dombois (1974). Nomenclature generally follows Allan (1961), or Moore and Edgar (1970). In some cases the two species of Weinmannia were not separated, although W. silvicola predominates. Dracophyllum was recorded to the genus if not identified. "Sprouting seedlings" were those with usually three or four leaves while the term "seedlings" describes juveniles under 1cm dbh. All species recorded in the circular plots (<10cm dbh) are defined as understorey or ground flora. RESULTS AND DISCUSSION Locations of the various kauri forests studied are shown in Fig. 1 while details are given in Table 1. Relative attributes with importance values of the first four dominant species of each stand are presented in Table 2. Absolute values for each stand and species (> 10cm dbh) are shown in Tables 3 and 4 90 respectively. A complete species list (< 10cm dbh) with relative frequencies in plots in each stand is given in Ahmed (1984), where more topographical, geological and meteorological details of each stand are also given. Species occurring in less than 4 stands have been excluded from Table 4, but are listed in the footnote. Fig. 1 Map of northern position of North Island of New Zealand showing location of kauri forests studied. Numbers are stand number. Details are given in Table 1. 91 Table 1: Characteristics of 25 kauri sampling sites Stand Locations Latitude Longitude Altitude Slope Aspect No S E (m) (degrees) 1. Te Paki Coastal Park 34° 28 172° 46 220 24 W 2. Omahuta Sanctuary 35° 15 173° 37 150 12 Flat Puketi State Forest 3. Te Harua Stream 35° 16 173° 44 305 35 N 4. Onekura Bluff 35° 11 173° 45 305 30 N 5. Loop Track 35° 15 173° 44 274 31 NE 6. Takapau Track 35° 13 173° 45 252 19 Flat 7. Manginangina Scenic 35° 12 173° 48 274 24 E Reserve 8. Russell State Forest 35° 23 174° 15 221 26 SW Warawara State Forest 9. Ridge Site 35° 22 173° 17 468 32 N 10. Plateau Site 35° 23 173° 17 358 28 N Waipoua State Forest 11. Waipoua Sanctuary 35° 29 173° 34 145 19 SW 12. Waipoua Coastal 35° 37 173° 29 244 21 SW 13. Trounson Kauri Park 35° 43 173° 38 175 19 N 14. Mount Manaia East facing slope 35° 49 174° 31 320 31 E West facing slope 35° 49 174° 31 320 26 W Little Barrier Island 15. Upper Thumb Track 36° 12 175° 04 335 32 S 16. Lower Thumb Track 36° 13 175° 04 213 26 NE 17. Valley Track 36° 13 175° 04 243 34 S High altitude Kauri 36° 12 175° 04 426 38 S 18. Te-Moehau 36° 31 175° 24 450 29 NW 19. Manaia Sanctuary 36° 52 175° 32 350 30 NW Waitakere Ranges 20. Cascade Kauri Park 36° 53 174° 31 240 35 EW 21. Piha 36° 58 174° 30 274 29 NW 22. Huia 36° 58 174° 34 274 31 NW Hunua Range 23. Konini Forks 37° 04 175° 08 335 30 NE 24. Mount William 37° 13 175° 02 350 26 N 25. Kaimai-Mamaku State 37° 36 175° 52 350 30 NW Forest 92 1. Te Paki Coastal Park The Te Paki coastal park is located on the east coast of the Cape Reinga district and the study area is one of the ridges to the east of the Cape Reinga road a few miles south of the lighthouse. Fifteen tree species were recorded in the study area (Table 3). Kauri comprised 67% of the total basal area and 39% of the total density (Table 2). Leptospermum ericoides was abundant having 9 % basal area. Dacrydium kirkii, Dacrydium cupressinum, Libocedrus plumosa, Phyllocladus trichomanoides and Knightia excelsa were other associates of kauri with low importance values. The canopy was irregular and high stand density (464 ha"*) with low stand basal area (34.5m2 ha-1) was the characteristic feature of this stand. Forty one species were recorded during the circular plot study. The vegetation was mainly composed of juvenile of Myrsine salicina, Gahnia xanthocarpa, Geniostoma ligustrifolium and kauri seedlings. These species were recorded in 65 to 95% of quadrats. Blechnum capense, Coprosma areolata, Cyathea smithii, Cyathea dealbata, Cyathodes fasciculata, Dodonea viscosa, Freycinetia banksii, Leptospermum ericoides, Nestegis lanceolata and Phebalium nudum were also found in 25 to 55% of quadrats. The study area was dry and steep. In many places the ground surface was exposed to direct sunlight either with no vegetation cover or with a few scattered plants. 2. Omahuta Sanctuary Omahuta kauri forest stands to the west of Puketi State Forest and 1km south of Mangamuka Bridge on State Highway 1 between Whangarei and Kaitaia. The sampling site was in a gully in Omahuta Sanctuary. This area was protected from the logging and now contains one of the finest stands of kauri in New Zealand (Sale 1978). Kauri is the dominant species of the area, although 28 stems in the sample comprised only 23m2 ha basal area (Table 3). Ackama rosaefolia is the co-dominant species. A few Dacrydium cupressinum, Podocarpus hallii and Podocarpus ferrugineus are present with kauri in the canopy layer. In the subcanopy Ixerba brexioides, Beilschmiedia tawa, Elaeocarpus dent at us and Pittosporum tenuifolium are abundant. These species are also frequent and widespread in the canopy gaps which are created by the fall of kauri or other big trees. Nineteen species > 10cm dbh are found in the area. The understorey contained 35 species < 10cm dbh, but it was mainly composed of dense Gahnia xanthocarpa, Dicksonia lanata and Freycinetia banksii. These species comprised 65 to 80% of the plots. Geniostoma ligustrifolium, Astelia trinervia and juvenile Ackama rosaefolia were found in 93 over 45% of the plots. Ricker sized kauri individuals were rare and only observed along the track and outside the sampling area in open places.